Acetylene_ the Principles of Its Generation and Use F. H. Leeds and W. J. Atkinson Butterfield 883 downloads.pdf

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The Project Gutenberg eBook of Acetylene, the Principles of Its
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Title: Acetylene, the Principles of Its Generation and Use

Author: F. H. Leeds
W. J. Atkinson Butterfield

Release date: May 1, 2005 [eBook #8144]
Most recently updated: May 17, 2013

Language: English

Other information and formats: www.gutenberg.org/ebooks/8144

Credits: Produced by Richard Prairie, Tonya Allen, Juliet Sutherland,
Charles Franks, and the Online Distributed Proofreading Team

*** START OF THE PROJECT GUTENBERG EBOOK ACETYLENE,
THE PRINCIPLES OF ITS GENERATION AND USE ***

ACETYLENE

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THE PRINCIPLES OF ITS GENERATION AND
USE
A PRACTICAL HANDBOOK ON THE PRODUCTION,
PURIFICATION, AND SUBSEQUENT TREATMENT OF
ACETYLENE FOR THE DEVELOPMENT OF LIGHT,
HEAT, AND POWER

BY

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F. H. LEEDS, F.I.C.
FOR SOME YEARS TECHNICAL EDITOR OF THE
JOURNAL "ACETYLENE"

AND

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W. J. ATKINSON BUTTERFIELD, M.A.
AUTHOR OF "THE CHEMISTRY OF GAS
MANUFACTURE"

Second Edition

REVISED AND ENLARGED

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PREFATORY NOTE TO THE FIRST EDITION
In compiling this work on the uses and application of acetylene, the special
aim of the authors has been to explain the various physical and chemical
phenomena:

(1) Accompanying the generation of acetylene from calcium carbide and
water.

(2) Accompanying the combustion of the gas in luminous or incandescent
burners, and

(3) Its employment for any purpose--(a) neat, (b) compressed into cylinders,
(c) diluted, and (d) as an enriching material.

They have essayed a comparison between the value of acetylene and other
illuminants on the basis of "illuminating effect" instead of on the
misleading basis of pure "illuminating power," a distinction which they
hope and believe will do much to clear up the misconceptions existing on
the subject. Tables are included, for the first time (it is believed) in English
publications, of the proper sizes of mains and service-pipes for delivering
acetylene at different effective pressures, which, it is hoped, will prove of
use to those concerned in the installation of acetylene lighting systems.

June 1903

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NOTE TO THE SECOND EDITION
The revision of this work for a new edition was already far advanced when
it was interrupted by the sudden death on April 30, 1908, of Mr. F. H.
Leeds. The revision was thereafter continued single-handed, with the help
of very full notes which Mr. Leeds had prepared, by the undersigned. It had
been agreed prior to Mr. Leeds' death that it would add to the utility of the
work if descriptions of a number of representative acetylene generators
were given in an Appendix, such as that which now appears at the
conclusion of this volume. Thanks are due to the numerous firms and
individuals who have assisted by supplying information for use in this
Appendix.

W. J. ATKINSON BUTTERFIELD

WESTMINSTER

August 1909

CONTENTS

CHAPTER I

INTRODUCTORY--THE COST AND ADVANTAGES OF ACETYLENE
LIGHTING

Intrinsic advantages
Hygienic advantages
Acetylene and paraffin oil
Blackened ceilings
Cost of acetylene lighting

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Cost of acetylene and coal-gas
Cost of acetylene and electric lighting
Cost of acetylene and paraffin oil
Cost of acetylene and air-gas
Cost of acetylene and candles
Tabular statement of costs (to face)
Illuminating power and effect

CHAPTER II

THE PHYSICS AND CHEMISTRY OF THE REACTION BETWEEN
CARBIDE AND WATER

Nature of calcium carbide
Storage of calcium carbide
Fire risks of acetylene lighting
Purchase of carbide
Quality and sizes of carbide
Treated and scented carbide
Reaction between carbide and water
--chemical nature
--heat evolved
--difference between heat and temperature
--amount of heat evolved
--effect of heat on process of generation
Reaction:
--effects of heat
--effect of heat on the chemical reaction
--effects of heat on the acetylene
--effects of heat on the carbide
Colour of spent carbide
Maximum attainable temperatures
Soft solder in generators
Reactions at low temperatures
Reactions at high temperatures
Pressure in generators

CHAPTER III

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THE GENERAL PRINCIPLES OF ACETYLENE GENERATION
ACETYLENE GENERATING APPARATUS

Automatic and non-automatic generators
Control of the chemical reaction
Non-automatic carbide-to-water generators
Non-automatic water-to-carbide generators
Automatic devices
Displacement gasholders
Action of water-to-carbide generators
Action of carbide-to-water generators
Use of oil in generator
Rising gasholder
Deterioration of acetylene on storage
Freezing and its avoidance
Corrosion in apparatus
Isolation of holder from generator
Water-seals
Vent pipes and safety valve
Frothing in generator
Dry process of generation
Artificial lighting of generator sheds

CHAPTER IV

THE SELECTION OF AN ACETYLENE GENERATOR

Points to be observed
Recommendations of Home Office Committee
British and Foreign regulations for the construction and installation of
acetylene generating plant

CHAPTER V

THE TREATMENT OF ACETYLENE AFTER GENERATION

Impurities in calcium carbide
Impurities of acetylene

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Removal of moisture
Generator impurities in acetylene
Filters
Carbide impurities in acetylene
Washers
Reasons for purification
Necessary extent of purification
Quantity of impurities in acetylene
Purifying materials
Bleaching powder
Heratol, frankoline, acagine, and puratylene
Efficiency of purifying material
Minor reagent
Method of a gas purifier
Methods of determining exhaustion of purifying material
Regulations for purification
Drying
Position of purifier
Filtration
General arrangement of plans
Generator residues
Disposal of residue

CHAPTER VI

THE CHEMICAL AND PHYSICAL PROPERTIES OF ACETYLENE

Physical properties
Leakage
Heat of combustion
Explosive limits
Range of explosibility
Solubility in liquids
Toxicity
Endothermic nature
Polymerisation
Heats of formation and combustion

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Colour of flame
Radiant efficiency
Chemical properties
Reactions with copper

CHAPTER VII

MAINS AND SERVICE-PIPES--SUBSIDIARY APPARATUS

Meters
Governors
Gasholder pressure
Pressure-gauges
Dimensions of mains and pipes
Velocity of flow in pipes
Service-pipes and mains
Leakage
Pipes and fittings
Laying mains
Expelling air from pipes
Tables of pipes and mains

CHAPTER VIII

COMBUSTION OF ACETYLENE IN LUMINOUS BURNERS--THEIR
DISPOSITION

Nature of luminous flames
Illuminating power
Early burners
Injector and twin-flame burners
Illuminating power of self-luminous burners
Glassware for burners

CHAPTER IX

INCANDESCENT BURNERS--HEATING APPARATUS--MOTORS--
AUTOGENOUS SOLDERING

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Merits of incandescent lighting
Conditions for incandescent lighting
Illuminating power of incandescent burners
Durability of mantles
Typical incandescent burners
Acetylene for heating and cooking
Acetylene motors
Blowpipes
Autogenous soldering and welding

CHAPTER X

CARBURETTED ACETYLENE

Carburetted acetylene
Illuminating power of carburetted acetylene
Carburetted acetylene for "power"

CHAPTER XI

COMPRESSED AND DISSOLVED ACETYLENE--MIXTURES WITH
OTHER GASES

Compression
Dissolved acetylene
Solution in acetone
Liquefied acetylene
Dilution with carbon dioxide
Dilution with air
Mixed carbides
Dilution with, methane and hydrogen
Self-inflammable acetylene
Enrichment with acetylene
Partial pressure
Acetylene-oil-gas

CHAPTER XII

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SUNDRY USES

Destruction of noxious moths
Destruction of phylloxera and mildew
Manufacture of lampblack
Production of tetrachlorethane
Utilisation of residues
Sundry uses for the gas

CHAPTER XIII

PORTABLE ACETYLENE LAMPS AND PLANT

Table and vehicular lamps
Flare lamps
Cartridges of carbide
Cycle-lamp burners
Railway lighting

CHAPTER XIV

VALUATION AND ANALYSIS OF CARBIDE

Regulations of British Acetylene Association
Regulations o£ German Acetylene Association
Regulations of Austrian Acetylene Association
Sampling carbide
Yield of gas from small carbide
Correction of volumes for temperature and pressure
Estimation of impurities
Tabular numbers

APPENDIX

DESCRIPTIONS OP GENERATORS

America: Canada
America: United States

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Austria-Hungary
Belgium
France
Germany
Great Britain and Ireland

INDEX

INDEX TO APPENDIX

ACETYLENE

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CHAPTER I
INTRODUCTORY--THE COST AND ADVANTAGES OF
ACETYLENE LIGHTING

Acetylene is a gas [Footnote: For this reason the expression, "acetylene
gas," which is frequently met with, would be objectionable on the ground of
tautology, even if it were not grammatically and technically incorrect.
"Acetylene-gas" is perhaps somewhat more permissible, but it is equally
redundant and unnecessary.] of which the most important application at the
present time is for illuminating purposes, for which its properties render it
specially well adapted. No other gas which can be produced on a
commercial scale is capable of giving, volume for volume, so great a yield
of light as acetylene. Hence, apart from the advantages accruing to it from
its mode of production and the nature of the raw material from which it is
produced, it possesses an inherent advantage over other illuminating gases
in the smaller storage accommodation and smaller mains and service-pipes
requisite for the maintenance of a given supply of artificial light. For
instance, if a gasholder is required to contain sufficient gas for the lighting
of an establishment or district for twenty-four hours, its capacity need not
be nearly so great if acetylene is employed as if oil-gas, coal-gas, or other
illuminating gas is used. Consequently, for an acetylene supply the
gasholder can be erected on a smaller area and for considerably less outlay
than for other gas supplies. In this respect acetylene has an unquestionable
economical advantage as a competitor with other varieties of illuminating
gas for supplies which have generally been regarded as lying peculiarly
within their preserves. The extent of this advantage will be referred to later.

The advantages that accrue to acetylene from its mode of production, and
the nature of the raw material from which it is obtained, are in reality of
more importance. Acetylene is readily and quickly produced from a raw
material--calcium carbide--which, relatively to the yield of light of the
gaseous product, is less bulky than the raw materials of other gases. In
comparison also with oils and candles, calcium carbide is capable of

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yielding, through the acetylene obtainable from it, more light per unit of
space occupied by it. This higher light-yielding capacity of calcium carbide,
ready to be developed through acetylene, gives the latter gas a great
advantage over all other illuminants in respect of compactness for transport
or storage. Hence, where facilities for transport or storage are bad or costly,
acetylene may be the most convenient or cheapest illuminant,
notwithstanding its relatively high cost in many other cases. For example, in
a district to which coal and oil must be brought great distances, the freight
on them may be so heavy that--regarding the question as simply one of
obtaining light in the cheapest manner--it may be more economical to bring
calcium carbide an equal or even greater distance and generate acetylene
from it on the spot, than to use oil or make coal-gas for lighting purposes,
notwithstanding that acetylene may not be able to compete on equal terms
with oil--or coal-gas at the place from which the carbide is brought.
Likewise where storage accommodation is limited, as in vehicles or in ships
or lighthouses, calcium carbide may be preferable to oil or other illuminants
as a source of light. Disregarding for the moment intrinsic advantages
which the light obtainable from acetylene has over other lights, there are
many cases where, owing to saving in cost of carriage, acetylene is the most
economical illuminant; and many other cases where, owing to limited space
for storage, acetylene far surpasses other illuminants in convenience, and is
practically indispensable.

The light of the acetylene flame has, however, some intrinsic advantages
over the light of other artificial illuminants. In the first place, the light more
closely resembles sunlight in composition or "colour." It is more nearly a
pure "white" light than is any other flame or incandescent body in general
use for illuminating purposes. The nature or composition of the light of the
acetylene flame will be dealt with more exhaustively later, and compared
with that afforded by other illuminants; but, speaking generally, it may be
said that the self-luminous acetylene light is superior in tint, to all other
artificial lights, for which reason it is invaluable for colour-judging and
shade-matching. In the second place, when the gas issues from a suitable
self-luminous burner under proper pressure, the acetylene flame is perfectly
steady; and in this respect it in preferable to most types of electric light, to
all self- luminous coal-gas flames and candles, and to many varieties of oil-
lamp. In steadiness and freedom from flicker it is fully equal to

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incandescent coal-gas light, but it in distinctly superior to the latter by
virtue of its complete freedom from noise. The incandescent acetylene
flame emits a slight roaring, but usually not more than that coming from an
atmospheric coal-gas burner. With the exception of the electric arc, self-
luminous acetylene yields a flame of unsurpassed intensity, and yet its light
is agreeably soft. In the third place, where electricity is absent, a brilliancy
of illumination which can readily be obtained from self-luminous acetylene
can otherwise only be procured by the employment of the incandescent
system applied either to coal-gas or to oil; and there are numerous
situations, such as factories, workshops, and the like, where the vibration of
the machinery or the prevalence of dust renders the use of mantles
troublesome if not impossible. Anticipating what will be said later, in cases
like these, the cost of lighting by self-luminous acetylene may fairly be
compared with self-luminous coal- gas or oil only; although in other
positions the economy of the Welsbach mantle must be borne in mind.

Acetylene lighting presents also certain important hygienic advantages over
other forms of flame lighting, in that it exhausts, vitiates, and heats the air
of a room to a less degree, for a given yield of light, than do either coal-gas,
oils, or candles. This point in favour of acetylene is referred to here only in
general terms; the evidence on which the foregoing statement is based will
be recorded in a tabular comparison of the cost and qualities of different
illuminants. Exhaustion of the air means, in this connexion, depletion of the
oxygen normally present in it. One volume of acetylene requires 2-1/2
volumes of oxygen for its complete combustion, and since 21 volumes of
oxygen are associated in atmospheric air with 79 volumes of inert gases--
chiefly nitrogen--which do not actively participate in combustion, it follows
that about 11.90 volumes of air are wholly exhausted, or deprived of
oxygen, in the course of the combustion of one volume of acetylene. If the
light which may be developed by the acetylene is brought into
consideration, it will be found that, relatively to other illuminants, acetylene
causes less exhaustion of the air than any other illuminating agent except
electricity. For instance, coal-gas exhausts only about 6- 1/2 times its
volume of air when it is burnt; but since, volume for volume, acetylene
ordinarily yields from three to fifteen times as much light as coal-gas, it
follows that the same illuminative value is obtainable from acetylene by
considerably less exhaustion of the air than from coal-gas. The exact ratio

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depends on the degree of efficiency of the burners, or of the methods by
which light is obtained from the gases, as will be realised by reference to
the table which follows. Broadly speaking, however, no illuminant which
evolves light by combustion (oxidation), and which therefore requires a
supply of oxygen or air for its maintenance, affords light with so little
exhaustion of the air as acetylene. Hence in confined, ill-ventilated, or
crowded rooms, the air will suffer less exhaustion, and accordingly be
better for breathing, if acetylene is chosen rather than any other illuminant,
except electricity.

Next, in regard to vitiation of the air, by which is meant the alteration in its
composition resulting from the admixture of products of combustion with it.
Electric lighting is as superior to other modes of lighting in respect of direct
vitiation as of exhaustion of the air, because it does not depend on
combustion. Putting it aside, however, light is obtainable by means of
acetylene with less attendant vitiation of the air than by means of any other
gas or of oil or candles. The principal vitiating factor in all cases is the
carbonic acid produced by the combustion. Now one volume of acetylene
on combustion yields two volumes of carbonic acid, whereas one volume of
coal-gas yields about 0.6 volume of carbonic acid. But even assuming that
the incandescent system of lighting is applied in the case of coal-gas and
not of acetylene, the ratio of the consumption of the two gases for the
development of a given illuminative effect will be such that no more
carbonic acid will be produced by the acetylene; and if the incandescent
system is applied either in both cases or in neither, the ratio will be greatly
in favour of acetylene. The other factors which determine the vitiation of
the air of a room in which the gas is burning are likewise under ordinary
conditions more in favour of acetylene. They are not, however, constant,
since the so-called "impurities," which on combustion cause vitiation of the
air, vary greatly in amount according to the extent to which the gases have
been purified. London coal-gas, which was formerly purified to the highest
degree practically attainable, used to contain on the average only 10 to 12
grains of sulphur per 100 cubic feet, and virtually no other impurity. But
now coal-gas, in London and most provincial towns, contains 40 to 50
grains of sulphur per 100 cubic foot. At least 5 grains of ammonia per 100
cubic foot in also present in coal-gas in some towns. Crude acetylene also
contains sulphur and ammonia, that coming from good quality calcium

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carbide at the present day including about 31 grains of the former and 25
grains of the latter per 100 cubic feet. But crude acetylene is also
accompanied by a third impurity, viz., phosphoretted hydrogen or
phosphine, which in unknown in coal-gas, and which is considerably more
objectionable than either ammonia or sulphur. The formation, behaviour,
and removal of those various impurities will be discussed in Chapter V.; but
here it may be said that there is no reason why, if calcium carbide of a fair
degree of purity has been used, and if the gas has been generated from it in
a properly designed and smoothly working apparatus-- this being quite as
important as, or even more important than, the purity of the original
carbide--the gas should not be freed from phosphorus, sulphur, and
ammonia to the utmost necessary or desirable extent, by processes which
are neither complicated nor expensive. And if this is done, as it always
should be whenever the acetylene is required for domestic lighting, the
vitiation of the air of a room due to the "impurities" in the gas will become
much less in the case of acetylene than in that of even well-purified coal-
gas; taking equal illuminating effect as the basis for comparison.

Acetylene is similarly superior, speaking generally, to petroleum in respect
of impurities, though the sulphur present in petroleum oils, such as are sold
in this country for household use, though very variable, is often quite small
in amount, and seldom is responsible for serious vitiation of the
atmosphere.

Regarding somewhat more closely the relative convenience and safety of
acetylene and paraffin for the illumination of country residences, it may be
remarked that an extraordinarily great amount of care must be bestowed
upon each separate lamp if the whole house is to be kept free from an odour
which is very offensive to the nostrils; and the time occupied in this
process, which of itself is a disagreeable one, reaches several hours every
day. Habit has taught the country dweller to accept as inevitable this waste
of time, and largely to ignore the odour of petroleum in his abode; but the
use of acetylene entirely does away with the daily cleaning of lamps, and, if
the pipe-fitting work has been done properly, yields light absolutely
unaccompanied by smell. Again, unless most carefully managed, the lamp-
room of a large house, with its store of combustible oil, and its collection of
greasy rags, must unavoidably prove a sensible addition to the risk of fire.

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The analogue of the lamp- room when acetylene is employed is the
generator-house, and this is a separate building at some distance from the
residence proper. There need be no appreciable odour in the generator-
house, except during the times of charging the apparatus; but if there is, it
passes into the open air instead of percolating into the occupied apartments.

The amount of heat developed by the combustion of acetylene also is less
for a given yield of light than that developed by most other illuminants. The
gas, indeed, is a powerful heating gas, but owing to the amount consumed
being so small in proportion to the light developed, the heat arising from
acetylene lighting in a room is less than that from most other illuminating
agents, if the latter are employed to the extent required to afford equally
good illumination. The ratio of the heat developed in acetylene lighting to
that developed in, e.g., lighting by ordinary coal-gas, varies considerably
according to the degree of efficiency of the burners, or, in other words, of
the methods by which light is obtained from the gases. Volume for volume,
acetylene yields on combustion about three and a half times as much heat as
coal- gas, yet, owing to its superior efficiency as an illuminant, any required
light may be obtained through it with no greater evolution of heat than the
best practicable (incandescent) burners for coal-gas produce. The heat
evolved by acetylene burners adequate to yield a certain light is very much
less than that evolved by ordinary flat-flame coal-gas burners or by oil-
lamps giving the same light, and is not more than about three times as much
as that from ordinary electric lamps used in numbers sufficient to give the
same light. More exact figures for the ratio between the heat developed in
acetylene lighting and that in other modes of lighting are given in the table
already referred to.

In connexion with the smaller amount of heat developed per unit of light
when acetylene is the illuminant, the frequently exaggerated claim that
acetylene does not blacken ceilings at all may be studied. Except it be a
carelessly manipulated petroleum-lamp, no form of artificial illuminant
employed nowadays ever emits black smoke, soot, or carbon, in spite of the
fact that all luminous flames commercially capable of utilisation do contain
free carbon in the elemental state. The black mark on a ceiling over a source
of light is caused by a rising current of hot air and combustion products set
up by the heat accompanying the light, which current of hot gas carries with

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it the dust and dirt always present in the atmosphere of an inhabited room.
As this current of air and burnt gas travels in a fairly concentrated vertical
stream, and as the ceiling is comparatively cool and exhibits a rough
surface, that dust and dirt are deposited on the ceiling above the flame, but
the stain is seldom or never composed of soot from the illuminant itself.
Proof of this statement may be found in the circumstance that a black mark
is eventually produced over an electric glow-lamp and above a pipe
delivering hot water. Clearly, therefore, the depth and extent of the mark
will depend on the volume and temperature of the hot gaseous current; and
since per unit of light acetylene emits a far smaller quantity of combustion
products and a far smaller amount of heat than any other flame illuminant
except incandescent coal-gas, the inevitable black mark over its flame takes
very much longer to appear. Quite roughly speaking, as may be deduced
from what has already been said on this subject, the luminous flame of
acetylene "blackens" a ceiling at about the same rate as a coal-gas burner of
the best Welsbach type.

There is one respect in which acetylene and other flame illuminants are
superior to electric lighting, viz., that they sterilise a larger volume of air.
All the air which is needed to support combustion, as well as the excess of
air which actually passes through the burner tube and flame in incandescent
burners, is obviously sterilised; but so also is the much larger volume of air
which, by virtue of the up-current due to the heat of the flame, is brought
into anything like close proximity with the light. The electric glow-lamp,
and the most popular and economical modern enclosed electric arc-lamp,
sterilise only the much smaller volume of air which is brought into direct
contact with their glass bulbs. Moreover, when large numbers of persons are
congregated in insufficiently ventilated buildings--and many public rooms
are insufficiently ventilated--the air becomes nauseous to inspire and
positively detrimental to the health of delicate people, by reason of the
human effluvia which arise from soiled raiment and uncleansed or
unhealthy bodies, long before the proportion of carbonic acid by itself is
high enough to be objectionable. Thus a certain proportion of carbonic acid
coming from human lungs and skin is more harmful than the same
proportion of carbonic acid derived from the combustion of gas or oil.
Hence acetylene and flame illuminants generally have the valuable hygienic
advantages over electric lighting, not only of killing a far larger number of

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the micro-organisms that may be present in the air, but, by virtue of their
naked flames, of burning up and destroying a considerable quantity of the
aforesaid odoriferous matter, thus relieving the nose and materially assisting
in the prevention of that lassitude and anæmia occasionally follow the
constant inspiration of air rendered foul by human exhalations.

The more important advantages of acetylene as an illuminant have now
been indicated, and it remains to discuss the cost of acetylene lighting in
comparison with other modes of procuring artificial light. At the outset it
may be stated that a very much greater reduction in the price of calcium
carbide--from which acetylene is produced--than is likely to ensue under
the present methods and conditions of manufacture will be required to make
acetylene lighting as cheap as ordinary gas lighting in towns in this country,
provided incandescent burners are used for the gas. On the score of
cheapness (and of convenience, unless the acetylene were delivered to the
premises from some central generating station) acetylene cannot compete as
an illuminant with coal-gas where the latter costs, say, not more than 5s. per
1000 cubic feet, if only reasonable attention is given to the gas-burners, and
at least a quarter of them are on the incandescent system. If, on the other
hand, coal-gas is misused and wasted through the employment only of
interior or worn-out flat-flame burners, while the best types of burner are
used for acetylene, the latter gas may prove as cheap for lighting as coal-gas
at, say, 2s. 6d. per 1000 cubic feet (and be far better hygienically); whereas,
contrariwise, if coal-gas is used only with good and properly maintained
incandescent burners, it may cost over 10s. per 1000 cubic feet, and be
cheaper than acetylene burned in good burners (and as good from the
hygienic standpoint). More precise figures on the relative costs of coal-gas
lighting and acetylene lighting are given in the tabular statement at the close
of this chapter.

With regard to electric lighting it is somewhat difficult to lay down a fair
basis of comparison, owing to the wide variations in the cost of current, and
in the efficiency of lamps, and to the undoubted hygienic and aesthetic
claims of electric lighting to precedence. But in towns in this country where
there is a public electricity supply, electric lighting will be used rather than
acetylene for the same reasons that it is preferred to coal-gas. Cost is only a
secondary consideration in such cases, and where coal-gas is reasonably

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cheap, and nevertheless gives place to electric lighting, acetylene clearly
cannot hope to supplant the latter. [Footnote: Where, however, as is
frequently the case with small public electricity-supply works, the voltage
of the supply varies greatly, the fluctuations in the light of the lamps, and
the frequent destruction of fuses and lamps, are such manifest
inconveniences that acetylene is in fact now being generally preferred to
electric lighting in such circumstances.] But where current cannot be had
from an electricity-supply undertaking, and it is a question, in the event of
electric lighting being adopted, of generating current by driving a dynamo,
either by means of a gas-engine supplied from public gas-mains, by means
of a special boiler installation, or by means of an oil-engine or of a power
gas-plant and gas-engine, the claims of acetylene to preference are very
strong. An important factor in the estimation of the relative advantages of
electricity and acetylene in such cases is the cost of labour in looking after
the generating plant. Where a gas-engine supplied from public gas-mains is
used for driving the dynamo, electric lighting can be had at a relatively
small expenditure for attendance on the generating plant. But the cost of the
gas consumed will be high, and actually light could be obtained directly
from the gas by means of incandescent mantles at far loss cost than by
consuming the gas in a motor for the indirect production of light by means
of electric current. Therefore electric lighting, if adopted under these
conditions, must be preferred to gas lighting from considerations which are
deemed to outweigh those of a much higher cost, and acetylene does not
present so great advantages over coal-gas as to affect the choice of electric
lighting. But in the cases where there is no public gas-supply, and current
must be generated from coal or coke or oil consumed on the spot, the cost
of the skilled labour required to look after either a boiler, steam-engine and
dynamo, or a power gas-plant and gas-engine or oil- engine and dynamo,
will be so heavy that unless the capacity of the installation is very great,
acetylene will almost certainly prove a cheaper and more convenient
method of obtaining light. The attention required by an acetylene
installation, such as a country house of upwards of thirty rooms would
want, is limited to one or two hours' labour per diem at any convenient time
during daylight. Moreover, the attendant need not be highly paid, as he will
not have required an engineman's training, as will the attendant on an
electric lighting plant. The latter, too, must be present throughout the hours
when light is wanted unless a heavy expenditure has been incurred on

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accumulators. Furthermore, the capital outlay on generating plant will be
very much less for acetylene than for electric lighting. General
considerations such as these lead to the conclusion that in almost all country
districts in this country a house or institution could be lighted more cheaply
by means of acetylene than by electricity. In the tabular statement of
comparative costs of different modes of lighting, electric lighting has been
included only on the basis of a fixed cost per unit, as owing to the very
varied cost of generating current by small installations in different parts of
the country it would be futile to attempt to give the cost of electric lighting
on any other basis, such as the prime cost of coal or coke in a particular
district. Where current is supplied by a public electricity- supply
undertaking, the cost per unit is known, and the comparative costs of
electric light and acetylene can be arrived at with tolerable precision. It has
not been thought necessary to include in the tabular statement electric arc-
lamps, as they are only suitable for the lighting of large spaces, where the
steadiness and uniformity of the illumination are of secondary importance.
Under such conditions, it may be stated parenthetically, the electric arc-light
is much less costly than acetylene lighting would be, but it is now in many
places being superseded by high-pressure gas or oil incandescent lights,
which are steady and generally more economical than the arc light.

The illuminant which acetylene is best fitted to supersede on the score of
convenience, cleanliness, and hygienic advantages is oil. By oil is meant, in
this connection, the ordinary burning petroleum, kerosene, or paraffin oil,
obtained by distilling and refining various natural oils and shales, found in
many countries, of which the United States (principally Pennsylvania),
Russia (the Caucasus chiefly), and Scotland are practically the only ones
which supply considerable quantities for use in Great Britain. Attempts are
often made to claim superiority for particular grades of these oils, but it
may be at once stated that so for as actual yield of light is concerned, the
same weight of any of the commercial oils will give practically the same
result. Hence in the comparative statement of the cost of different methods
of lighting, oil will be taken at the cheapest rate at which it could ordinarily
be obtained, including delivery charges, at a country house, when bought by
the barrel. This rate at the present time is about ninepence per gallon. A
higher price may be paid for grades of mineral oil reputed to be safer or to
give a "brighter" or "clearer" light; but as the quantity of light depends

Page 26

mainly upon the care and attention bestowed on the burner and glass fittings
of the lamp, and partly upon the employment of a suitable wick, while the
safety of each lamp depends at least as much upon the design of that lamp,
and the accuracy with which the wick fits the burner tube, as upon the
temperature at which the oil "flashes," the extra expense involved in
burning fancy-priced oils will not be considered here.

The efficiency (i.e., the light yielded per pint or other unit volume
consumed) of oil-lamps varies greatly, and, speaking broadly, increases with
the power of the lamp. But as large or high-power lamps are not needed
throughout a house, it is fairer to assume that the light obtainable from oil in
ordinary household use is the mean of that afforded by large and that
afforded by small lamps. A large oil-lamp as commonly used in country
houses will give a light of about 20 candle- power, while a convenient small
lamp will give a light of not more than about 5 candle-power. The large
lamp will burn about 55 hours for every gallon of oil consumed, or give an
illuminating duty of about 1100 candle-hours (i.e., the product of candle-
power by burning-hours) per gallon. The small lamp, on the other hand, will
burn about 140 hours for every gallon of oil consumed, or give an
illuminating duty of about 700 candle-hours per gallon. Actually large
lamps would in most country houses be used only in the entrance hall,
living-rooms, and kitchen, while passages and minor rooms on the lower
floors would be lighted by small lamps. Hence, making due allowance for
the lower rate of consumption of the small lamps, it will be seen that, given
equal numbers of large and small lamps in use, the mean illuminating duty
of a gallon of oil as burnt in country houses will be 987, or, in round
figures, 990 candle-hours. Usually candles are used in the bedrooms of
country houses where the lower floors are lighted by means of petroleum
lamps; but when acetylene is installed in such a house it will frequently be
adopted in the principal bed- and dressing-rooms as well as in the living-
rooms, as, unless candles are employed very lavishly, they are really totally
inadequate to meet the reasonable demands for light of, e.g., a lady dressing
for dinner. Where acetylene displaces candles as well as lamps in a country
house, it is necessary, in comparing the cost of the new illuminant with that
of the candles and oil, to bear in mind the superior degree of illumination
which is secured in all rooms, at least where candles were formerly used.

Page 27

In regard to exhaustion and vitiation of the air, and to heat evolved, self-
luminous petroleum lamps stand on much the same footing as coal-gas
when the latter is burned in flat-flame burners, if the comparison is based
on a given yield of light. A large lamp, owing to its higher illuminating
efficiency, is better in this respect than a small one-- light for light, it is
more hygienic than ordinary flat-flame coal-gas burners, while a small lamp
is less hygienic. It will therefore be understood at once, from what has
already been said about the superiority on hygienic grounds of acetylene to
flat-flame coal-gas lighting, that acetylene is in this respect far superior to
petroleum lamps. The degree of its superiority is indicated more precisely
by the figures quoted in the tabular statement which concludes this chapter.

Before giving the tabular statement, however, it is necessary to say a few
words in regard to one method of lighting which, may possibly develop into
a more serious competitor with acetylene for the lighting of the better class
of country house than any of the illuminating agents and modes of lighting
so far referred to. The method in question is lighting by so-called air-gas
used for raising mantles to incandescence in upturned or inverted burners of
the Welsbach-Kern type. "Air-gas" is ordinary atmospheric air, more or less
completely saturated with the vapour of some highly volatile hydrocarbon.
The hydrocarbons practically applied have so far been only "petroleum
spirit" or "carburine," and "benzol." "Petroleum spirit" or "carburine"
consists of the more highly volatile portion of petroleum, which is removed
by distillation before the kerosene or burning oil is recovered from the
crude oil. Several grades of this highly volatile petroleum distillate are
distinguished in commerce; they differ in the temperature at which they
begin to distil and the range of temperature covered by their distillation,
and, speaking more generally, in their degree of volatility, uniformity, and
density. If the petroleum distillate is sufficiently volatile and fairly uniform
in character, good air-gas may be produced merely by allowing air to pass
over an extended surface of the liquid. The vapour of the petroleum spirit is
of greater density than air, and hence, if the course of the air-gas is
downward from the apparatus at which it is produced, the flow of air into
the apparatus and over the surface of the spirit will be automatically
maintained by the "pull" of the descending air-gas when once the flow has
been started until the outlet for the air-gas is stopped or the spirit in the
apparatus is exhausted. Hence, if the apparatus for saturating air with the

Page 28

vapour of the light petroleum is placed well above all the points at which
the air-gas is to be burnt-- e.g., on the roof of the house--the production of
the air-gas may by simple devices become automatic, and the only attention
the apparatus will require will be the replenishing of its reservoir from time
to time with light petroleum. But a number of precautions are required to
make this simple process operate without interruption or difficulty. For
instance, the evaporation of the spirit must not be so rapid relatively to its
total bulk as to lower its temperature, and thereby that of the overflowing
air, too much; the reservoir must be protected from extreme cold and
extreme heat; and the risk of fire from the presence of a highly volatile and
highly inflammable liquid on or near the roof of the house must be met.
This risk is one to which fire insurance companies take exception.

More commonly, however, air-gas is made non-automatically, or more or
less automatically by the employment of some mechanical means. The light
petroleum, benzol, or other suitable volatile hydrocarbon is volatilised,
where necessary, by the application of gentle heat, while air is driven over
or through it by means of a small motor, which in some cases is a hot-air
engine operated by heat supplied by a flame of the air-gas produced. These
air-gas producers, or at least the reservoir of volatile hydrocarbon, may be
placed in an outbuilding, so that the risk of fire in the house itself is
minimised. They require, however, as much attention as an acetylene
generator, usually more. It is difficult to give reliable data as to the cost of
air-gas, inclusive of the expenses of production. It varies considerably with
the description of hydrocarbon employed, and its market price. Air-gas is
only slightly inferior hygienically to acetylene, and the colour of its light is
that of the incandescent light as produced by coal-gas or acetylene. Air-gas
of a certain grade may be used for lighting by flat-flame burners, but it has
been available thus for very many years, and has failed to achieve even
moderate success. But the advent of the incandescent burner has completely
changed its position relatively to most other illuminants, and under certain
conditions it seems likely to be the most formidable competitor with
acetylene. Since air-gas, and the numerous chemically identical products
offered under different proprietary names, is simply atmospheric air more
or less loaded with the vapour of a volatile hydrocarbon which is normally
liquid, it possesses no definite chemical constitution, but varies in
composition according to the design of the generating plant, the

Page 29

atmospheric temperature at the time of preparation, the original degree of
volatility of the hydrocarbon, the remaining degree of volatility after the
more volatile portions have been vaporised, and the speed at which the air
is passed through the carburettor. The illuminating power and the calorific
value of air-gas, unless the manufacture is very precisely controlled, are apt
to be variable, and the amount of light, emitted, either in self-luminous or in
incandescent burners, is somewhat indeterminate. The generating plant
must be so constructed that the air cannot at any time be mixed with as
much hydrocarbon vapour as constitutes an explosive mixture with it,
otherwise the pipes and apparatus will contain a gas which will forthwith
explode if it is ignited, i.e., if an attempt is made to consume it otherwise
than in burners with specially small orifices. The safely permissible
mixtures are (1) air with less hydrocarbon vapour than constitutes an
explosive mixture, and (2) air with more hydrocarbon vapour than
constitutes an explosive mixture. The first of these two mixtures is available
for illuminating purposes only with incandescent mantles, and to ensure a
reasonable margin of safety the mixing apparatus must be so devised that
the proportion of hydrocarbon vapour in the air-gas can never exceed 2 per
cent. From Chapter VI. it will be evident that a little more than 2 per cent.
of benzene, pentane or benzoline vapour in air forms an explosive mixture.
What is the lowest proportion of such vapours in admixture with air which
will serve on combustion to maintain a mantle in a state of incandescence,
or even to afford a flame at all, does not appear to have been precisely
determined, but it cannot be much below 1- 1/2 per cent. Hence the
apparatus for producing air-gas of this first class must be provided with
controlling or governing devices of such nicety that the proportion of
hydrocarbon vapour in the air-gas is maintained between about 1-1/2 and 2
per cent. It is fair to say that in normal working conditions a number of
devices appear to fulfil this requirement satisfactorily. The second of the
two mixtures referred to above, viz., air with more hydrocarbon vapour than
constitutes an explosive mixture, is primarily suitable for combustion in
self-luminous burners, but may also be consumed in properly designed
incandescent burners. But the generating apparatus for such air-gas must be
equipped with some governing or controlling device which will ensure the
proportion of hydrocarbon vapour in the mixture never falling below, say, 7
per cent. On the other hand, if saturation of the air with the vapour is
practically attained, should the temperature of the gas fall before it arrives

Page 30

at the point of combustion, part of the spirit will condense out, and the
product will thus lose part of its illuminating or calorific intensity, besides
partially filling the pipes with liquid products of condensation. The loss of
intensity in the gas during cold weather may or may not be inconvenient
according to circumstances; but the removal of part of the combustible
material brings the residual air-gas nearer to its limit of explosibility--for it
is simply a mixture of combustible vapour with air, which, normally, is not
explosive because the proportion of spirit is too high--and thus, when led
into an atmospheric burner, the extra amount of air introduced at the
injector jets may cause the mixture to be an explosive mixture of air and
spirit, so that it will take fire within the burner tube instead of burning
quietly at the proper orifice. This matter will be made clearer on studying
what is said about explosive limits in Chapter VI., and what is stated about
incandescent acetylene (carburetted or not) in Chapters IX. and X. Clearly,
however, high-grade air-gas is only suitable for preparation at the
immediate spot where it is to be consumed; it cannot be supplied to a
complete district unless it is intentionally made of such lower intensity that
the proportion of spirit is too small ever to allow of partial deposition in the
mains during the winter.

It is perhaps necessary to refer to the more extended use of candles for
lighting in some few houses in which lamps are disliked on aesthetic, or, in
some cases, ostensibly on hygienic grounds. Candle lighting, speaking
broadly, is either very inadequate so far as ordinary living-rooms are
concerned, or, if adequate, is very costly. Tests specially carried out by one
of the authors to determine some of the figures required in the ensuing table
show that ordinary paraffin or "wax" candles usually emit about 20 per
cent. more light than that given by the standard spermaceti candle, whose
luminosity is the unit by which the intensity of other lights is reckoned in
Great Britain; and also that the light so emitted by domestic candles is
practically unaffected by the sizes--"sixes," "eights," or "twelves"--burnt. In
the sizes examined the light evolved has varied between 1.145 and 1.298
"candles," perhaps tending to increase slightly with the diameter of the
candle tested. Hence, to obtain illumination in a room equal on the average
to that afforded by 100 standard candles, or some other light or lights
aggregating 100 candle- power, would require the use of only 80 to 85
ordinary paraffin, ozokerite, or wax candles. But actually the essential

Page 31

objects in a room could be equally well illuminated by, say, 30 candles well
distributed, as by two or three incandescent gas-burners, or four or five
large oil- lamps. Lights of high intensity, such as powerful gas-burners or
oil- lamps, must give a higher degree of illumination in their immediate
vicinity than is really necessary, if they are to illuminate adequately the
more distant objects. The dissemination and diffusion of their light can be
greatly aided by suitable colouring of ceilings, walls and drapings; but
unless the illumination by means of lights of relatively high intensity is
made almost wholly indirect, candles or other lights of low intensity, such
as small electric glow-lamps, can, by proper distribution, be made to give
more uniform or more suitably apportioned illumination. In this respect
candles have an economical and, in some measure, a material advantage
over acetylene also. (But when the method of lighting is by flames--candle
or other--the multiplication of the number of units which is involved when
they are of low intensity, seriously increases the risk of fire through
accidental contact of inflammable material with any one of the flames. This
risk is much greater with naked flames, such as candles, than with, say,
inverted incandescent gas flames, which are to all intents and purposes fully
protected by a closed glass globe.) Hence, in the tabular statement which
follows of the comparative cost, &c., of different illuminants, it will be
assumed that 30 good candles would in practice be equally efficient in
regard to the illumination of a room as large oil-lamps, acetylene flames, or
incandescent gas-burners aggregating 100 candle-power.

For the same reason it will be assumed that electric glow-lamps of low
intensity (nominally of 8 candle-power or less), aggregating 70-80 candle-
power, will practically serve, if suitably distributed, equally as well as 100
candle-power obtained from more powerful sources of light. Electric glow-
lamps of a nominal intensity of 16 candles or thereabouts, and good flat-
flame gas-burners, aggregating 90-95 candle-power, will similarly be taken
as equivalent, if suitably distributed, to 100 candle- power from more
powerful sources of light. Of the latter it will be assumed that each source
has an intensity between 20 and 30 candle-power, such as is afforded by a
large oil-lamp, a No. 1 Welsbach-Kern upturned, or a "Bijou" inverted
incandescent gas-burner, or a 0.70-cubic-foot-per- hour acetylene burner.
Either of these sources of light, when used in sufficient numbers, so that
with proper distribution they light a room adequately, will be taken in the

Page 32

tabular statement which follows as affording, per candle-power evolved, the
standard illuminating effect required in that room. The same illuminating
effect will be regarded as attainable by means of candles aggregating only
35 per cent., or small electric glow-lamps aggregating 77 per cent., or large
electric glow- lamps and flat-flame gas-burners aggregating 90 to 95 per
cent. of this candle-power; while if sources of light of higher intensity are
used, such as Osram or Tantalum electric lamps, or the larger incandescent
gas- burners (the Welsbach "C" or "York," or the Nos. 3 or 4 Welsbach-
Kern upturned, or the No. 1 or larger size inverted burners) or incandescent
acetylene burners, it will be assumed that their aggregate candle-power
must be in excess by about 15 per cent., in order to compensate for the
impossibility of obtaining equally well distributed illumination. These
assumptions are based on general considerations and data as to the effect of
sources of light of different intensities in giving practically the same degree
of illumination in a room; it would occupy too much space here to discuss
more fully the grounds on which they have been made. It must suffice to
say that they have been adopted with the object of being perfectly fair to
each means of illumination.

COST PER HOUR AND HYGIENIC EFFECT OF LIGHTING BY
DIFFERENT MEANS

The data (except in the column headed "cost per 100 candle-hours") refer to
the illumination afforded by medium-sized (0.5 to 0.7 cubic foot per hour)
acetylene burners yielding together a light of about 100 candle- power, and
to the approximately equivalent illumination as afforded by other means of
illumination, when the lighting-units or sources of light are rationally
distributed.

Interest and depreciation charges on the outlay on piping or wiring a house,
on brackets, fittings, lamps, candelabra, and storage accommodation (for
carbide and oil) have been taken as equivalent for all modes of lighting, and
omitted in computing the total cost. The cost of labour for attendance on
acetylene plant, oil lamps, and candles is an uncertain and variable item--
approximately equal for all these modes of lighting, but saved in coal-gas
and electric lighting from public supply mains.

Page 33

_______________________________________________________________
_______
| | | | |
| |
| | |Candle- | Number
|Aggregate| Cost |
| | |Power of| of | Candle-
| per |
| | Description of | each |Lighting | Power
| 100 |
|Illuminant. | Burner or Lamp. |Lighting| Units
|Afforded.|Candle-|
| | | Unit. |Required.|(About.)
|Hours. |
| | |(About.)| |
|Pence. |
|____________|____________________|________|_________|_________
|_______|
| | | | |
| |
| |Self-luminous; 0.5 | | |
| |
| | cubic foot per hour| 18 | 5 | 90
| 1.11 |
| |Self-luminous; 0.7 | | |
| |
| Acetylene | cubic foot per hour| 27 | 4 | 108
| 1.02 |
| |Self-luminous; 1.0 | | |
| |
| | cubic foot per hour| 45.5 | 3 | 136
| 0.85 |
| |Incandescent; 0.5 | | |
| |
| | cubic foot per hour| 50 | 3 | 150
| 0.49 |
|____________|____________________|________|_________|_________
|_______|
| | | | |
| |
| Petroleum | Large lamp . . . . | 20 | 5 | 100
| 0.84 |
| (paraffin | | | |
| |
| oil) | Small lamp . . . . | 5 | 14 | 70
| 1.31 |

Page 34

|____________|____________________|________|_________|_________
|_______|
| | | | |
| |
| |Flat flame (bad) 5 | | |
| |
| | cubic feet per hour| 8 | 10 | 80
| 3.75 |
| |Flat flame (good) 6 | | |
| |
| Coal Gas | cubic feet per hour| 16 | 6 | 96
| 2.25 |
| |Incandescent (No. 1 | | |
| |
| | Kern or Bijou In- | 25 | 4 | 100
| 0.38 |
| | verted); 1-1/2 | | |
| |
| | cubic feet per hour| | |
| |
|____________|____________________|________|_________|_________
|_______|
| | | | |
| |
| Candles |"Wax" (so-called) . | 1.2 | 30 | 35
| 6.14 |
|____________|____________________|________|_________|_________
|_______|
| | | | |
| |
| | Small glow . . . . | 7 | 11 | 77
| 2.81 |
| | Large glow . . . . | 13 | 7 | 91
| 2.90 |
| Electricity| | | |
| |
| | Tantalum . . . . . | 19 | 5 | 95
| 1.52 |
| | Osram . . . . . . | 14 | 7 | 98
| 1.00 |
|____________|____________________|________|_________|_________
|_______|

_______________________________________________________________
____
| | | |

Page 35

Page 36

Page 37

| | Description of | tal |Air.Cubic|Cubic
Feet|Number of|
|Illuminant. | Burner or Lamp. |Expen-|Feet Dep-| of Car-
|Units of |
| | | ces. |rived of |bonic Acid|
Heat. |
| | | | Oxygen. | Formed.
|Calories.|
|____________|____________________|______|_________|__________|
_________|
| | | | | |
|
| |Self-luminous; 0.5 | | | |
|
| | cubic foot per hour| [1] | 29.8 | 5.0 |
900 |
| |Self-luminous; 0.7 | | | |
|
| Acetylene | cubic foot per hour| | 33.3 | 5.6 |
1010 |
| |Self-luminous; 1.0 | | | |
|
| | cubic foot per hour| | 35.7 | 6.0 |
1000 |
| |Incandescent; 0.5 | | | |
|
| | cubic foot per hour| [2] | 17.9 | 3.0 |
545 |
|____________|____________________|______|_________|__________|
_________|
| | | | | |
|
| Petroleum | Large lamp . . . . | | 140.0 | 19.6 |
3630 |
| (paraffin | | [3] | | |
|
| oil) | Small lamp . . . . | | 154.0 | 21.6 |
4000 |
|____________|____________________|______|_________|__________|
_________|
| | | | | |
|
| |Flat flame (bad) 5 | | | |
|
| | cubic feet per hour| Nil | 270.0 | 27.0 |
7750 |
| |Flat flame (good) 6 | | | |
|

Page 38

| Coal Gas | cubic feet per hour| Nil | 195.0 | 19.5 |
5580 |
| |Incandescent (No. 1 | | | |
|
| | Kern or Bijou In- | [4] | 27.0 | 2.7 |
775 |
| | verted); 1-1/2 | | | |
|
| | cubic feet per hour| | | |
|
|____________|____________________|______|_________|__________|
_________|
| | | | | |
|
| Candles |"Wax" (so-called) . | Nil | 100.5 | 13.7 |
2700 |
|____________|____________________|______|_________|__________|
_________|
| | | | | |
|
| | Small glow . . . . |2s.6d.| Nil | Nil |
285 |
| | Large glow . . . . |2s.6d.| " | " |
360 |
| Electricity| | [5] | | |
|
| | Tantalum . . . . . |7s.6d.| " | " |
172 |
| | Osram . . . . . . | 6s. | " | " |
96 |
|____________|____________________|______|_________|__________|
_________|

[Footnote 1: Interest and depreciation charges on generating and purifying
plant = 0.15 penny. Purifying material and burner renewals = 0.05 penny.]

[Footnote 2: Mantle renewals as for coal-gas.]

[Footnote 3: Renewals of wicks and chimneys = 0.02 penny.]

[Footnote 4: Renewals and mantles (and chimneys) at contract rate of 3s.
per burner per annum.]

[Footnote 5: Renewals of lamps and fuses, at price indicated per lamp per
annum.]

Page 39

The conventional method of making pecuniary comparisons between
different sources of artificial light consists in simply calculating the cost of
developing a certain number of candle-hours of light--i.e., a certain amount
of standard candle-power for a given number of hours--on the assumption
that as many separate sources of light are employed as may be required to
bring the combined illuminating power up to the total amount wanted. In
view of the facts as to dissemination and diffusion, or the difference
between sheer illuminating power and useful illuminating effect, which
have just been elaborated, and in view of the different intensities of the
different unit sources of light (which range from the single candle to a
powerful large incandescent gas-burner or a metallic filament electric
lamp), such a method of calculation is wholly illusory. The plan adopted in
the following table may also appear unnecessarily complicated; but it is not
so to the reader if he remembers that the apparently various amount of
illumination is corrected by the different numbers of illuminating units until
the amount of simple candle-power developed, whatever illuminant be
employed, suffices to light a room having an area of about 300 square feet
(i.e., a room, 17-1/2 feet square, or one 20 feet long by 15 feet wide), so
that ordinary print may be read comfortably in any part of the room, and the
titles of books, engravings, &c., in any position on the walls up to a height
of 8 feet from the ground may be distinguished with ease. The difference in
cost, &c., of a greater or less degree of illumination, or of lighting a larger
or smaller room by acetylene or any other of the illuminants named, will be
almost directly proportional to the cost given for the stated conditions.
Nevertheless, it should be recollected that when the conventional system is
retained--useful illuminating effect being sacrificed to absolute illuminating
power--acetylene is made to appear cheaper in comparison with all weaker
unit sources of light, and dearer in comparison with all stronger unit sources
of light than the accompanying table indicates it to be. In using the
comparative figures given in the table, it should be borne in mind that they
refer to more general and more brilliant illumination of a room than is
commonly in vogue where the lighting is by means of electric light,
candles, or oil- lamps. The standard of illumination adopted for the table is
one which is only gaining general recognition where incandescent gas or
acetylene lighting is available, though in exceptional cases it has doubtless
been attained by means of oil-lamps or flat-flame gas-burners, but very
rarely if ever by means of carbon-filament electric glow-lamps, or candles.

Page 40

It assumes that the occupants of a room do not wish to be troubled to bring
work or book "to the light," but wish to be able to work or read wheresoever
in the room they will, without consideration of the whereabouts of the light
or lights.

It should, perhaps, be added that so high a price as 5s. per 1000 cubic feet
for coal-gas rarely prevails in Great Britain, except in small outlying towns,
whereas the price of 6d. per Board of Trade unit for electricity is not
uncommonly exceeded in the few similar country places in which there is a
public electricity supply.

Page 41

CHAPTER II
THE PHYSICS AND CHEMISTRY OF THE REACTION
BETWEEN CARBIDE AND WATER

THE NATURE OF CALCIUM CARBIDE.--The raw material from which,
by interaction with water, acetylene is obtained, is a solid body called
calcium carbide or carbide of calcium. Inasmuch as this substance can at
present only be made on a commercial scale in the electric furnace--and so
far as may be foreseen will never be made on a large scale except by means
of electricity--inasmuch as an electric furnace can only be worked
remuneratively in large factories supplied with cheap coal or water power;
and inasmuch as there is no possibility of the ordinary consumer of
acetylene ever being able to prepare his own carbide, all descriptions of this
latter substance, all methods of winning it, and all its properties except
those which concern the acetylene-generator builder or the gas consumer
have been omitted from the present book. Hitherto calcium carbide has
found but few applications beyond that of evolving acetylene on treatment
with water or some aqueous liquid, hygroscopic solid, or salt containing
water of crystallisation; but it has possibilities of further employment,
should its price become suitable, and a few words will be devoted to this
branch of the subject in Chapter XII. Setting these minor uses aside,
calcium carbide has no intrinsic value except as a producer of acetylene,
and therefore all its characteristics which interest the consumer of acetylene
are developed incidentally throughout this volume as the necessity for
dealing with them arises.

It is desirable, however, now to discuss one point connected with solid
carbide about which some misconception prevails. Calcium carbide is a
body which evolves an inflammable, or on occasion an explosive, gas when
treated with water; and therefore its presence in a building has been said to
cause a sensible increase in the fire risk because attempts to extinguish a
fire in the ordinary manner with water may cause evolution of acetylene
which should determine a further production of flame and heat. In the

Page 42

absence of water, calcium carbide is absolutely inert as regards fire; and on
several occasions drums of it have been recovered uninjured from the
basement of a house which has been totally destroyed by fire. With the
exception of small 1-lb. tins of carbide, used only by cyclists, &c., the
material is always put into drums of stout sheet-iron with riveted or folded
seams. Provided the original lid has not been removed, the drums are air-
and water-tight, so that the fireman's hose may be directed upon them with
impunity. When a drum has once been opened, and not all of its contents
have been put into the generator, ordinary caution--not merely as regards
fire, but as regards the deterioration of carbide when exposed to the
atmosphere--suggests either that the lid must be made air-tight again (not by
soldering it), [Footnote: Carbide drums are not uncommonly fitted with
self-sealing or lever-top lids, which are readily replaced hermetically tight
after opening and partial removal of the contents of the drum.] or preferably
that the rest of the carbide shall be transferred to some convenient
receptacle which can be perfectly closed. [Footnote: It would be a
refinement of caution, though hardly necessary in practice, to fit such a
receptacle with a safety-valve. If then the vessel were subjected to sudden
or severe heating, the expansion of the air and acetylene in it could not
possibly exert a disruptive effect upon the walls of the receptacle, which, in
the absence of the safety-valve, is imaginable.] Now, assuming this done,
the drums are not dependent upon soft solder to keep them sound, and so
they cannot open with heat. Fire and water, accordingly, cannot affect them,
and only two risks remain: if stored in the basement of a tall building,
falling girders, beams or brickwork may burst them; or if stored on an upper
floor, they may fall into the basement and be burst with the shock--in either
event water then having free access to the contents. But drums of carbide
would never be stored in such positions: a single one would be kept in the
generator-house; several would be stored in a separate room therein, or in
some similar isolated shed. The generator-house or shed would be of one
story only; the drums could neither fall nor have heavy weights fall on them
during a fire; and therefore there is no reason why, if a fire should occur, the
firemen should not be permitted to use their hose in the ordinary fashion.
Very similar remarks apply to an active acetylene generator. Well built, such
plant will stand much heat and fire without failure; if it is non-automatic,
and of combustible materials contains nothing but gas in the holder, the
worst that could happen in times of fire would be the unsealing of the bell

Page 43

or its fracture, and this would be followed, not at all by any explosion, but
by a fairly quiet burning of the escaping gas, which would be over in a very
short time, and would not add to the severity of the conflagration unless the
generator-house were so close to the residence that the large flame of
burning gas could ignite part of the main building. Even if the heat were so
great near the holder that the gas dissociated, it is scarcely conceivable that
a dangerous explosion should arise. But it is well to remember, that if the
generator-house is properly isolated from the residence, if it is constructed
of non-inflammable materials, if the attendant obeys instructions and
refrains from taking a naked light into the neighbourhood of the plant, and
if the plant itself is properly designed and constructed, a fire at or near an
acetylene generator is extremely unlikely to occur. At the same time, before
the erection of plant to supply any insured premises is undertaken, the
policy or the company should be consulted to ascertain whether the
adoption of acetylene lighting is possibly still regarded by the insurers as
adding an extra risk or even as vitiating the whole insurance.

REGULATIONS FOR THE STORAGE OF CARBIDE: BRITISH.--There
are also certain regulations imposed by many local authorities respecting
the storage of carbide, and usually a licence for storage has to be obtained if
more than 5 lb. is kept at a time. The idea of the rule is perfectly justifiable,
and it is generally enforced in a sensible spirit. As the rules may vary in
different localities, the intending consumer of acetylene must make the
necessary inquiries, for failure to comply with the regulations may
obviously be followed by unpleasantness.

Having regard to the fact that, in virtue of an Order in Council dated July 7,
1897, carbide may be stored without a licence only in separate substantial
hermetically closed metal vessels containing not more than 1 lb. apiece and
in quantities not exceeding 5 lb. in the aggregate, and having regard also to
the fact that regulations are issued by local authorities, the Fire Offices'
Committee of the United Kingdom has not up to the present deemed it
necessary to issue special rules with reference to the storage of carbide of
calcium.

The following is a copy of the rules issued by the National Board of Fire
Underwriters of the UNITED STATES OF AMERICA for the storage of

Page 44

calcium carbide on insured premises:

RULES FOR THE STORAGE OF CALCIUM CARBIDE.

(a) Calcium carbide in quantities not to exceed six hundred (600) pounds
may be stored, when contained in approved metal packages not to exceed
one hundred (100) pounds each, inside insured property, provided that the
place of storage be dry, waterproof and well ventilated, and also provided
that all but one of the packages in any one building shall be sealed and the
seals shall not be broken so long as there is carbide in excess of one (1)
pound in any other unsealed package in the building.

(b) Calcium carbide in quantities in excess of six hundred (600) pounds
must be stored above ground in detached buildings, used exclusively for the
storage of calcium carbide, in approved metal packages, and such buildings
shall be constructed to be dry, waterproof and well ventilated.

(c) Packages to be approved must be made of metal of sufficient strength to
insure handling the package without rupture, and be provided with a
screwed top or its equivalent.

They must be constructed so as to be water- and air-tight without the use of
solder, and conspicuously marked "CALCIUM CARBIDE--DANGEROUS
IF NOT KEPT DRY."

The following is a summary of the AUSTRIAN GOVERNMENT rules
relating to the storage and handling of carbide:

(1) It must be sold and stored only in closed water-tight vessels, which, if
the contents exceed 10 kilos., must be marked in plain letters "CALCIUM
CARBIDE--TO BE KEPT CLOSED AND DRY." They must not be of
copper and if soldered must be opened by mechanical means and not by
unsoldering. They must be stored out of the reach of water.

(2) Quantities not exceeding 300 kilos. may be stored in occupied houses,
provided the single drums do not exceed 100 kilos. nominal capacity. The
storage-place must be dry and not underground.

Page 45

(3) The limits specified in Rule 2 apply also to generator-rooms, with the
proviso also that in general the amount stored shall not exceed five days'
consumption.

(4) Quantities ranging from 300 to 1000 kilos. must be stored in special
well-ventilated uninhabited non-basement rooms in which lights and
smoking are not allowed.

(5) Quantities exceeding 1000 kilos. must be stored in isolated fireproof
magazines with light water-tight roofs. The floors must be at least 8 inches
above ground-level.

(6) Carbide in water-tight drums may be stored in the open in a fenced
enclosure at least 30 feet from buildings, adjoining property, or
inflammable materials. The drums must be protected from wet by a light
roof.

(7) The breaking of carbide must be done by men provided with respirators
and goggles, and care taken to avoid the formation of dust.

(8) Local or other authorities will issue from time to time special
regulations in regard to carbide trade premises.

The ITALIAN GOVERNMENT rules relating to the storage and transport
of carbide follow in the main those of the Austrian Government, but for
quantities between 300 and 2000 kilos sanction is required from the local
authorities, and for larger quantities from superior authorities. The storage
of quantities ranging from 300 to 2000 kilos is forbidden in dwelling-
houses and above the latter quantity the storage-place must be isolated and
specially selected. No special permit is required for the storage of quantities
not exceeding 300 kilos. Workmen exposed to carbide dust arising from the
breaking of carbide or otherwise must have their eyes and respiratory
organs suitably protected.

THE PURCHASE OF CARBIDE.--Since calcium carbide is only useful as
a means of preparing acetylene, it should be bought under a guarantee (1)
that it contains less impurities than suffice to render the crude gas
dangerous in respect of spontaneous inflammability, or objectionable in a

Page 46

manner to be explained later on, when consumed; and (2) that it is capable
of evolving a fixed minimum quantity of acetylene when decomposed by
water. Such determination, however, cannot be carried out by the ordinary
consumer for himself. A generator which is perfectly satisfactory in general
behaviour, and which evolves a sufficient proportion of the possible total
make of gas to be economical, does not of necessity decompose the carbide
quantitatively; nor is it constructed in a fashion to render an exact
measurement of the gas liberated at standard temperature and pressure easy
to obtain. For obvious reasons the careful consumer of acetylene will keep a
record of the carbide decomposed and of the acetylene generated--the latter
perhaps only in terms of burner- hours, or the like; but in the event of
serious dispute as to the gas- making capacity of his raw material, he must
have a proper analysis made by a qualified chemist.

Calcium carbide is crushed by the makers into several different sizes, in
each of which all the lumps exceed a certain size and are smaller than
another size. It is necessary to find out by experiment, or from the maker,
what particular size suits the generator best, for different types of apparatus
require different sizes of carbide. Carbide cannot well be crushed by the
consumer of acetylene. It is a difficult operation, and fraught with the
production of dust which is harmful to the eyes and throat, and if done in
open vessels the carbide deteriorates in gas- making power by its exposure
to the moisture of the atmosphere. True dust in carbide is objectionable, and
practically useless for the generation of acetylene in any form of apparatus,
but carbide exceeding 1 inch in mesh is usually sold to satisfy the
suggestions of the British Acetylene Association, which prescribes 5 per
cent, of dust as the maximum. Some grades of carbide are softer than
others, and therefore tend to yield more dust if exposed to a long journey
with frequent unloadings.

There are certain varieties of ordinary carbide known as "treated carbide,"
the value of which is more particularly discussed in Chapter III. The
treatment is of two kinds, or of a combination of both. In one process the
lumps are coated with a strong solution of glucose, with the object of
assisting in the removal of spent lime from their surface when the carbide is
immersed in water. Lime is comparatively much more soluble in solutions
of sugar (to which class of substances glucose belongs) than in plain water;

Page 47

so that carbide treated with glucose is not so likely to be covered with a
closely adherent skin of spent lime when decomposed by the addition of
water to it. In the other process, the carbide is coated with or immersed in
some oil or grease to protect it from premature decomposition. The latter
idea, at least, fulfils its promises, and does keep the carbide to a large extent
unchanged if the lumps are exposed to damp air, while solving certain
troubles otherwise met with in some generators (cf. Chapter III.); but both
operations involve additional expense, and since ordinary carbide can be
used satisfactorily in a good fixed generator, and can be preserved without
serious deterioration by the exercise of reasonable care, treated carbide is
only to be recommended for employment in holderless generators, of which
table-lamps are the most conspicuous forms. A third variant of plain carbide
is occasionally heard of, which is termed "scented" carbide. It is difficult to
regard this material seriously. In all probability calcium carbide is
odourless, but as it begins to evolve traces of gas immediately atmospheric
moisture reaches it, a lump of carbide has always the unpleasant smell of
crude acetylene. As the material is not to be stored in occupied rooms, and
as all odour is lost to the senses directly the carbide is put into the generator,
scented carbide may be said to be devoid of all utility.

THE REACTION BETWEEN CARBIDE AND WATER.--The reaction
which occurs when calcium carbide and water are brought into contact
belongs to the class that chemists usually term double decompositions.
Calcium carbide is a chemical compound of the metal calcium with carbon,
containing one chemical "part," or atomic weight, of the former united to
two chemical parts, or atomic weights, of the latter; its composition
expressed in symbols being CaC_2. Similarly, water is a compound of two
chemical parts of hydrogen with one of oxygen, its formula being H_2O.
When those two substances are mixed together the hydrogen of the water
leaves its original partner, oxygen, and the carbon of the calcium carbide
leaves the calcium, uniting together to form that particular compound of
hydrogen and carbon, or hydrocarbon, which is known as acetylene, whose
formula is C_2H_2; while the residual calcium and oxygen join together to
produce calcium oxide or lime, CaO. Put into the usual form of an equation,
the reaction proceeds thus--

(1) CaC_2 + H_2O = C_2H_2 + CaO.

Page 48

This equation not only means that calcium carbide and water combine to
yield acetylene and lime, it also means that one chemical part of carbide
reacts with one chemical part of water to produce one chemical part of
acetylene and one of lime. But these four chemical parts, or molecules,
which are all equal chemically, are not equal in weight; although, according
to a common law of chemistry, they each bear a fixed proportion to one
another. Reference to the table of "Atomic Weights" contained in any text-
book of chemistry will show that while the symbol Ca is used, for
convenience, as a contraction or sign for the element calcium simply, it
bears a more important quantitative significance, for to it will be found
assigned the number 40. Against carbon will be seen the number 12; against
oxygen, 16; and against hydrogen, 1. These numbers indicate that if the
smallest weight of hydrogen ever found in a chemical compound is called 1
as a unit of comparison, the smallest weights of calcium, carbon, and
oxygen, similarly taking part in chemical reactions are 40, 12, and 16
respectively. Thus the symbol CaC_2, comes to convoy three separate
ideas: (a) that the substance referred to is a compound of calcium and
carbon only, and that it is therefore a carbide of calcium; (b) that it is
composed of one chemical part or atom of calcium and two atoms of
carbon; and (c) that it contains 40 parts by weight of calcium combined
with twice twelve, or 24, parts of carbon. It follows from (c) that the weight
of one chemical part, now termed a molecule as the substance is a
compound, of calcium carbide is (40 + 2 x 12) = 64. By identical methods
of calculation it will be found that the weight of one molecule of water is
18; that of acetylene, 26; and that of lime, 56. The general equation (1)
given above, therefore, states in chemical shorthand that 64 parts by weight
of calcium carbide react with 18 parts of water to give 26 parts by weight of
acetylene and 56 parts of lime; and it is very important to observe that just
as there are the same number of chemical parts, viz., 2, on each side, so
there are the same number of parts by weight, for 64 + 18 = 56 + 26 = 82.
Put into other words equation (1) shows that if 64 grammes, lb., or cwts. of
calcium carbide are treated with 18 grammes, lb., or cwts. of water, the
whole mass will be converted into acetylene and lime, and the residue will
not contain any unaltered calcium carbide or any water; whence it may be
inferred, as is the fact, that if the weights of carbide and water originally
taken do not stand to one another in the ratio 64 : 18, both substances
cannot be entirely decomposed, but a certain quantity of the one which was

Page 49

in excess will be left unattacked, and that quantity will be in exact
accordance with the amount of the said excess--indifferently whether the
superabundant substance be carbide or water.

Hitherto, for the sake of simplicity, the by-product in the preparation of
acetylene has been described as calcium oxide or quicklime. It is, however,
one of the leading characteristics of this body to be hygroscopic, or greedy
of moisture; so that if it is brought into the presence of water, either in the
form of liquid or as vapour, it immediately combines therewith to yield
calcium hydroxide, or slaked lime, whose chemical formula is Ca(OH)_2.
Accordingly, in actual practice, when calcium carbide is mixed with an
excess of water, a secondary reaction takes place over and above that
indicated by equation (1), the quicklime produced combining with one
chemical part or molecule of water, thus--

CaO + H_2O = Ca(OH)_2.

As these two actions occur simultaneously, it is more usual, and more in
agreement with the phenomena of an acetylene generator, to represent the
decomposition of calcium carbide by the combined equation--

(2) CaC_2 + 2H_2O = C_2H_2 + Ca(OH)_2.

By the aid of calculations analogous to those employed in the preceding
paragraph, it will be noticed that equation (2) states that 1 molecule of
calcium carbide, or 64 parts by weight, combines with 2 molecules of water,
or 36 parts by weight, to yield 1 molecule, or 26 parts by weight of
acetylene, and 1 molecule, or 74 parts by weight of calcium hydroxide
(slaked lime). Here again, if more than 36 parts of water are taken for every
64 parts of calcium carbide, the excess of water over those 36 parts is left
undecomposed; and in the same fashion, if less than 36 parts of water are
taken for every 64 parts of calcium carbide, some of the latter must remain
unattacked, whilst, obviously, the amount of acetylene liberated cannot
exceed that which corresponds with the quantity of substance suffering
complete decomposition. If, for example, the quantity of water present in a
generator is more than chemically sufficient to attack all the carbide added,
however largo or small that excess may be, no more, and, theoretically
speaking, no less, acetylene can ever be evolved than 26 parts by weight of

Page 50

gas for every 64 parts by weight of calcium carbide consumed. It is,
however, not correct to invert the proposition, and to say that if the carbide
is in excess of the water added, no more, and, theoretically speaking, no
less, acetylene can ever be evolved than 26 parts by weight of gas for every
36 parts of water consumed, as might be gathered from equation (2);
because equation (1) shows that 26 parts of acetylene may, on occasion, be
produced by the decomposition of 18 parts by weight of water. From the
purely chemical point of view this apparent anomaly is explained by the
circumstance that of the 36 parts of water present on the left-hand aide of
equation (2), only one-half, i.e., 18 parts by weight, are actually
decomposed into hydrogen and oxygen, the other 18 parts remaining
unattacked, and merely attaching themselves as "water of hydration" to the
56 parts of calcium oxide in equation (1) so as to produce the 74 parts of
calcium hydroxide appearing on the right-hand side of equation (2). The
matter is perhaps rendered more intelligible by employing the old name for
calcium hydroxide or slaked lime, viz., hydrated oxide of calcium, and by
writing its formula in the corresponding form, when equation (2) becomes

CaC_2 + 2H_2O = C_2H_2 + CaO.H_2O.

It is, therefore, absolutely correct to state that if the amount of calcium
carbide present in an acetylene generator is more than chemically sufficient
to decompose all the water introduced, no more, and theoretically speaking
no less, acetylene can ever be liberated than 26 parts by weight of gas for
every 18 parts by weight of water attacked. This, it must be distinctly
understood, is the condition of affairs obtaining in the ideal acetylene
generator only; since, for reasons which will be immediately explained,
when the output of gas is measured in terms of the water decomposed, in no
commercial apparatus, and indeed in no generator which can be imagined
fit for actual employment, does that output of gas ever approach the
quantitative amount; but the volume of water used, if not actually
disappearing, is always vastly in excess of the requirements of equation (2).
On the contrary, when the make of gas is measured in terms of the calcium
carbide consumed, the said make may, and frequently does, reach 80, 90, or
even 99 per cent. of what is theoretically possible. Inasmuch as calcium
carbide is the one costly ingredient in the manufacture of acetylene, so long
as it is not wasted-- so long, that is to say, as nearly the theoretical yield of

Page 51

gas is obtained from it--an acetylene generator is satisfactory or efficient in
this particular; and except for the matter of solubility discussed in the
following chapter, the quantity of water consumed is of no importance
whatever.

HEAT EVOLVED IN THE REACTION.--The chemical reaction between
calcium carbide and water is accompanied by a large evolution of heat,
which, unless due precautions are taken to prevent it, raises the temperature
of the substances employed, and of the apparatus containing them, to a
serious and often inconvenient extent. This phenomenon is the most
important of all in connexion with acetylene manufacture; for upon a proper
recognition of it, and upon the character of the precautions taken to avoid
its numerous evil effects, depend the actual value and capacity for smooth
working of any acetylene generator. Just as, by an immutable law of
chemistry, a given weight of calcium carbide yields a given weight of
acetylene, and by no amount of ingenuity can be made to produce either
more or less; so, by an equally immutable law of physics, the
decomposition of a given weight of calcium carbide by water, or the
decomposition of a given weight of water by calcium carbide, yields a
perfectly definite quantity of heat--a quantity of heat which cannot be
reduced or increased by any artifice whatever. The result of a production of
heat is usually to raise the temperature of the material in which it is
produced; but this is not always the case, and indeed there is no necessary
connexion or ratio between the quantity of heat liberated in any form of
chemical reaction--of which ordinary combustion is the commonest type--
and the temperature attained by the substances concerned. This matter has
so weighty a bearing upon acetylene generation, and appears to be so
frequently misunderstood, that a couple of illustrations may with advantage
be studied. If a vessel full of cold water, and containing also a thermometer,
is placed over a lighted gas-burner, at first the temperature of the liquid
rises steadily, and there is clearly a ratio between the size of the flame and
the speed at which the mercury mounts up the scale. Finally, however, the
thermometer indicates a certain point, viz., 100° C, and the water begins to
boil; yet although the burner is untouched, and consequently, although heat
must be passing into the vessel at the same rate as before, the mercury
refuses to move as long as any liquid water is left. By the use of a gas meter
it might be shown that the same volume of gas is always consumed (a) in

Page 52

raising the temperature of a given quantity of cold water to the boiling-
point, and another equally constant volume of gas is always consumed (b)
in causing the boiling water to disappear as steam. Hence, as coal-gas is
assumed for the present purpose to possess invariably the same heating
power, it appears that the same quantity of heat is always needed to convert
a given amount of cold water at a certain temperature into steam; but
inasmuch as reference to the meter would show that about 5 times the
volume of gas is consumed in changing the boiling water into steam as is
used in heating the cold water to the boiling-point, it will be evident that the
temperature of the mass is raised as high by the heat evolved during the
combustion of one part of gas as it is by that liberated on the combustion of
6 times that amount.

A further example of the difference between quantity of heat and sensible
temperature may be seen in the combustion of coal, for (say) one
hundredweight of that fuel might be consumed in a very few minutes in a
furnace fitted with a powerful blast of air, the operation might be spread
over a considerable number of hours in a domestic grate, or the coal might
be allowed to oxidise by exposure to warm air for a year or more. In the last
case the temperature might not attain that of boiling water, in the second it
would be about that of dull redness, and in the first it would be that of
dazzling whiteness; but in all three cases the total quantity of heat produced
by the time the coal was entirely consumed would be absolutely identical.
The former experiment with water and a gas-burner, too, might easily be
modified to throw light upon another problem in acetylene generation, for it
would be found that if almost any other liquid than water were taken, less
gas (i.e., a smaller quantity of heat) would be required to raise a given
weight of it from a certain low to a certain high temperature than in the case
of water itself; while if it were possible similarly to treat the same weight of
iron (of which acetylene generators are constructed), or of calcium carbide,
the quantity of heat used to raise it through a given number of thermometric
degrees would hardly exceed one-tenth or one- quarter of that needed by
water itself. In technical language this difference is due to the different
specific heats of the substances mentioned; the specific heat of a body being
the relative quantity of heat consumed in raising a certain weight of it a
certain number of degrees when the quantity of heat needed to produce the
same effect on the same weight of water is called unity. Thus, the specific

Page 53

heat of water being termed 1.0, that of iron or steel is 0.1138, and that of
calcium carbide 0.247, [Footnote: This is Carlson's figure. Morel has taken
the value 0.103 in certain calculations.] both measured at temperatures
where water is a liquid. Putting the foregoing facts in another shape, for a
given rise in temperature that substance will absorb the most heat which has
the highest specific heat, and therefore, in this respect, 1 part by weight of
water will do the work of roughly 9 parts by weight of iron, and of about 4
parts by weight of calcium carbide.

From the practical aspect what has been said amounts to this: During the
operation of an acetylene generator a large amount of heat is produced, the
quantity of which is beyond human control. It is desirable, for various
reasons, that the temperature shall be kept as low as possible. There are
three substances present to which the heat may be compelled to transfer
itself until it has opportunity to pass into the surrounding atmosphere: the
material of which the apparatus is constructed, the gas which is in process
of evolution, and whichever of the two bodies-- calcium carbide or water--is
in excess in the generator. Of these, the specific heat at constant pressure of
acetylene has unfortunately not yet been determined, but its relative
capacity for absorbing heat is undoubtedly small; moreover the gas could
not be permitted to become sufficiently hot to carry off the heat without
grave disadvantages. The specific heat of calcium carbide is also
comparatively small, and there are similar disadvantages in allowing it to
become hot; moreover it is deficient in heat-conducting power, so that heat
communicated to one portion of the mass does not extend rapidly
throughout, but remains concentrated in one spot, causing the temperature
to rise objectionably. Steel has a sufficient amount of heat-conducting
power to prevent undue concentration in one place; but, as has been stated,
its specific heat is only one-ninth that of water. Water is clearly, therefore,
the proper substance to employ for the dissipation of the heat generated,
although it is strictly speaking almost devoid of heat-conducting power; for
not only is the specific heat of water much greater than that of any other
material present, but it possesses in a high degree the faculty of absorbing
heat throughout its mass, by virtue of the action known as convection,
provided that heat is communicated to it at or near the bottom, and not too
near its upper surface. Moreover, water is a much more valuable substance
for dissipating heat than appears from the foregoing explanation; for

Page 54

reference to the experiment with the gas- burner will show that six and a
quarter times as much heat can be absorbed by a given weight of water if it
is permitted to change into steam, as if it is merely raised to the boiling-
point; and since by no urging of the gas-burner can the temperature be
raised above 100° C. as long as any liquid water remains unevaporated, if
an excess of water is employed in an acetylene generator, the temperature
inside can never-- except quite locally--exceed 100° C., however fast the
carbide be decomposed. An indefinitely large consumption of water by
evaporation in a generator matters nothing, for the liquid may be considered
of no pecuniary value, and it can all be recovered by condensation in a
subsequent portion of the plant.

It has been said that the quantity of heat liberated when a certain amount of
carbide suffers decomposition is fixed; it remains now to consider what that
quantity is. Quantities of heat are always measured in terms of the amount
needed to raise a certain weight of water a certain number of degrees on the
thermometric scale. There are several units in use, but the one which will be
employed throughout this book is the "Large Calorie"; a large calorie being
the amount of heat absorbed in raising 1 kilogramme of water 1° C.
Referring for a moment to what has been said about specific heats, it will be
apparent that if 1 large calorie is sufficient to heat 1 kilo, of water through
1° C. the same quantity will heat 1 kilo. of steel, whose specific heat is
roughly 0.11, through (10/011) = 9° C., or, which comes to the same thing,
will heat 9 kilos, of steel through 1° C.; and similarly, 1 large calorie will
raise 4 kilos. of calcium carbide 1° C. in temperature, or 1 kilo. 4° C. The
fact that a definite quantity of heat is manifested when a known weight of
calcium carbide is decomposed by water is only typical; for in every
chemical process some disturbance of heat, though not necessarily of
sensible (or thermometric) character, occurs, heat being either absorbed or
set free. Moreover, if when given weights of two or more substances unite
to form a given weight of another substance, a certain quantity of heat is set
free, precisely the same amount of heat is absorbed, or disappears, when the
latter substance is decomposed to form the same quantities of the original
substances; and, per contra, if the combination is attended by a
disappearance of heat, exactly the same amount is liberated when the
compound is broken up into its first constituents. Compounds are therefore
of two kinds: those which absorb heat during their preparation, and

Page 55

consequently liberate heat when they are decomposed--such being termed
endothermic; and those which evolve heat during their preparation, and
consequently absorb heat when they are decomposed--such being called
exothermic. If a substance absorbs heat during its formation, it cannot be
produced unless that heat is supplied to it; and since heat, being a form of
motion, is equally a form of energy, energy must be supplied, or work must
be done, before that substance can be obtained. Conversely, if a substance
evolves heat during its formation, its component parts evolve energy when
the said substance is being produced; and therefore the mere act of
combination is accompanied by a facility for doing work, which work may
be applied in assisting some other reaction that requires heat, or may be
usefully employed in any other fashion, or wasted if necessary. Seeing that
there is a tendency in nature for the steady dissipation of energy, it follows
that an exothermic substance is stable, for it tends to remain as it is unless
heat is supplied to it, or work is done upon it; whereas, according to its
degree of endothermicity, an endothermic substance is more or less
unstable, for it is always ready to emit heat, or to do work, as soon as an
opportunity is given to it to decompose. The theoretical and practical results
of this circumstance will be elaborated in Chapter VI., when the
endothermic nature of acetylene is more fully discussed.

A very simple experiment will show that a notable quantity of heat is set
free when calcium carbide is brought into contact with water, and by
arranging the details of the apparatus in a suitable manner, the quantity of
heat manifested may be measured with considerable accuracy. A lengthy
description of the method of performing this operation, however, scarcely
comes within the province of the present book, and it must be sufficient to
say that the heat is estimated by decomposing a known weight of carbide by
means of water in a small vessel surrounded on all sides by a carefully
jacketed receptacle full of water and provided with a sensitive thermometer.
The quantity of water contained in the outer vessel being known, and its
temperature having been noted before the reaction commences, an
observation of the thermometer after the decomposition is finished, and
when the mercury has reached its highest point, gives data which show that
the reaction between water and a known weight of calcium carbide
produces heat sufficient in amount to raise a known weight of water through
a known thermometric distance; and from these figures the corresponding

Page 56

number of large calories may easily be calculated. A determination of this
quantity of heat has been made experimentally by several investigators,
including Lewes, who has found that the heat evolved on decomposing 1
gramme of ordinary commercial carbide with water is 0.406 large calorie.
[Footnote: Lewes returns his result as 406 calories, because he employs the
"small calorie." The small calorie is the quantity of heat needed to raise 1
gramme of water 1° C.; but as there are 1000 grammes in 1 kilogramme, the
large calorie is equal to 1000 small calories. In many respects the former
unit is to be preferred.] As the material operated upon contained only 91.3
per cent. of true calcium carbide, he estimates the heat corresponding with
the decomposition of 1 gramme of pure carbide to be 0.4446 large calorie.
As, however, it is better, and more in accordance with modern practice, to
quote such data in terms of the atomic or molecular weight of the substance
concerned, and as the molecular weight of calcium carbide is 64, it is
preferable to multiply these figures by 64, stating that, according to Lewes'
researches, the heat of decomposition of "1 gramme- molecule" (i.e., 64
grammes) of a calcium carbide having a purity of 91.3 per cent. is just
under 26 calories, or that of 1 gramme-molecule of pure carbide 28.454
calories. It is customary now to omit the phrase "one gramme-molecule" in
giving similar figures, physicists saying simply that the heat of
decomposition of calcium carbide by water when calcium hydroxide is the
by-product, is 28.454 large calories.

Assuming all the necessary data known, as happens to be the case in the
present instance, it is also possible to calculate theoretically the heat which
should be evolved on decomposing calcium carbide by means of water.
Equation (2), given on page 24, shows that of the substances taking part in
the reaction 1 molecular weight of calcium carbide is decomposed, and 1
molecular weight of acetylene is formed. Of the two molecules of water,
only one is decomposed, the other passing to the calcium hydroxide
unchanged; and the 1 molecule of calcium hydroxide is formed by the
combination of 1 atom of free calcium, 1 atom of free oxygen, and 1
molecule of water already existing as such. Calcium hydroxide and water
are both exothermic substances, absorbing heat when they are decomposed,
liberating it when they are formed. Acetylene is endothermic, liberating
heat when it is decomposed, absorbing it when it is produced. Unfortunately
there is still some doubt about the heat of formation of calcium carbide, De

Page 57

Forcrand returning it as -0.65 calorie, and Gin as +3.9 calories. De
Forcrand's figure means, as before explained, that 64 grammes of carbide
should absorb 0.65 large calorie when they are produced by the
combination of 40 grammes of calcium with 24 grammes of carbon; the
minus sign calling attention to the belief that calcium carbide is
endothermic, heat being liberated when it suffers decomposition. On the
contrary, Gin's figure expresses the idea that calcium carbide is exothermic,
liberating 3.9 calories when it is produced, and absorbing them when it is
decomposed. In the absence of corroborative evidence one way or the other,
Gin's determination will be accepted for the ensuing calculation. In equation
(2), therefore, calcium carbide is decomposed and absorbs heat; water is
decomposed and absorbs heat; acetylene is produced and absorbs heat; and
calcium hydroxide is produced liberating heat. On consulting the tables of
thermo-chemical data given in the various text-books on physical
chemistry, all the other constants needed for the present purpose will be
found; and it will appear that the heat of formation of water is +69 calories,
that of acetylene -58.1 calories, and that of calcium hydroxide, when 1 atom
of calcium, 1 atom of oxygen, and 1 molecule of water unite together, is
+160.1 calories. [Footnote: When 1 atom of calcium, 2 atoms of oxygen,
and 2 atoms of hydrogen unite to form solid calcium hydroxide, the heat of
formation of the latter is 229.1 (cf. infra). This value is simply 160.1 + 69.0
= 229.1; 69.0 being the heat of formation of water.] Collecting the results
into the form of a balance-sheet, the effect of decomposing calcium carbide
with water is this:

_Heat liberated._ | _Heat absorbed._
|
Formation of Ca(OH)_2 16O.1 | Formation of acetylene 58.1
| Decomposition of water 69.0
| Decomposition of carbide 3.9
| Balance 29.1
_____ |
_____
|
Total 160.1 | Total 160.1

Therefore when 64 grammes of calcium carbide are decomposed by water,
or when 18 grammes of water are decomposed by calcium carbide (the by-
product in each case being calcium hydroxide or slaked lime, for the

Page 58

formation of which a further 18 grammes of water must be present in the
second instance), 29.1 large calories are set free. It is not possible yet to
determine thermo-chemical data with extreme accuracy, especially on such
a material as calcium carbide, which is hardly to be procured in a state of
chemical purity; and so the value 28.454 calories experimentally found by
Lewes agrees very satisfactorily, considering all things, with the calculated
value 29.1 calories. It is to be noticed, however, that the above calculated
value has been deduced on the assumption that the calcium hydroxide is
obtained as a dry powder; but as slaked lime is somewhat soluble in water,
and as it evolves 3 calories in so dissolving, if sufficient water is present to
take up the calcium hydroxide entirely into the liquid form (i.e., that of a
solution), the amount of heat set free will be greater by those 3 calories, i.e.,
32.1 large calories altogether.

THE PROCESS OF GENERATION.--Taking 28 as the number of large
calories developed when 64 grammes of ordinary commercial calcium
carbide are decomposed with sufficient water to leave dry solid calcium
hydroxide as the by-product in acetylene generation, this quantity of heat is
capable of exerting any of the following effects. It is sufficient (1) to raise
1000 grammes of water through 28° C., say from 10° C. (50° F., which is
roughly the temperature of ordinary cold water) to 38° C. It is sufficient (2)
to raise 64 grammes of water (a weight equal to that of the carbide
decomposed) through 438° C., if that were possible. It would raise (3) 311
grammes of water through 90° C., i.e., from 10° C. to the boiling-point. If,
however, instead of remaining in the liquid state, the water were converted
into vapour, the same quantity of heat would suffice (4) to change 44.7
grammes of water at 10° C. into steam at 100° C.; or (5) to change 46.7
grammes of water at 10° C. into vapour at the same temperature. It is an
action of the last character which takes place in acetylene generators of the
most modern and usual pattern, some of the surplus water being evaporated
and carried away as vapour at a comparatively low temperature with the
escaping gas; for it must be remembered that although steam, as such,
condenses into liquid water immediately the surrounding temperature falls
below 100° C., the vapour of water remains uncondensed, even at
temperatures below the freezing- point, when that vapour is distributed
among some permanent gas--the precise quantity of vapour so remaining
being a function of the temperature and barometric height. Thus it appears

Page 59

that if the heat evolved during the decomposition of calcium carbide is not
otherwise consumed, it is sufficient in amount to vaporise almost exactly 3
parts by weight of water for every 4 parts of carbide attacked; but if it were
expended upon some substance such as acetylene, calcium carbide, or steel,
which, unlike water, could not absorb an extra amount by changing its
physical state (from solid to liquid, or from liquid to gas), the heat
generated during the decomposition of a given weight of carbide would
suffice to raise an equal weight of the particular substance under
consideration to a temperature vastly exceeding 438° C. The temperature
attained, indeed, measured in Centigrade degrees, would be 438 multiplied
by the quotient obtained on dividing the specific heat of water by the
specific heat of the substance considered: which quotient, obviously, is the
"reciprocal" of the specific heat of the said substance.

The analogy to the combustion of coal mentioned on a previous page shows
that although the quantity of heat evolved during a certain chemical reaction
is strictly fixed, the temperature attained is dependent on the time over
which the reaction is spread, being higher as the process is more rapid. This
is due to the fact that throughout the whole period of reaction heat is
escaping from the mass, and passing into the atmosphere at a fairly constant
speed; so that, clearly, the more slowly heat is produced, the better
opportunity has it to pass away, and the less of it is left to collect in the
material under consideration. During the action of an acetylene generator,
there is a current of gas constantly travelling away from the carbide, there is
vapour of water constantly escaping with the gas, there are the walls of the
generator itself constantly exposed to the cooling action of the atmosphere,
and there is either a mass of calcium carbide or of water within the
generator. It is essential for good working that the temperature of both the
acetylene and the carbide shall be prevented from rising to any noteworthy
extent; while the amount of heat capable of being dissipated into the air
through the walls of the apparatus in a given time is narrowly limited,
depending upon the size and shape of the generator, and the temperature of
the surrounding air. If, then, a small, suitably designed generator is working
quite slowly, the loss of heat through the external walls of the apparatus
may easily be rapid enough to prevent the internal temperature from rising
objectionably high; but the larger the generator, and the more rapidly it is
evolving gas, the less does this become possible. Since of the substances in

Page 60

or about a generator water is the one which has by far the largest capacity
for absorbing heat, and since it is the only substance to which any necessary
quantity of heat can be safely or conveniently transmitted, it follows that the
larger in size an acetylene generator is, or the more rapidly that generator is
made to deliver gas, the more desirable is it to use water as the means for
dissipating the surplus heat, and the more necessary is it to employ an
apparatus in which water is in large chemical excess at the actual place of
decomposition.

The argument is sometimes advanced that an acetylene generator containing
carbide in excess will work satisfactorily without exhibiting an undesirable
rise in internal temperature, if the vessel holding the carbide is merely
surrounded by a large quantity of cold water. The idea is that the heat
evolved in that particular portion of the charge which is suffering
decomposition will be communicated with sufficient speed throughout the
whole mass of calcium carbide present, whence it will pass through the
walls of the containing vessel into the water all round. Provided the
generator is quite small, provided the carbide container is so constructed as
to possess the maximum of superficial area with the minimum of cubical
capacity (a geometrical form to which the sphere, and in one direction the
cylinder, are diametrically opposed), and provided the walls of the container
do not become coated internally or externally with a coating of lime or
water scale so as to diminish in heat- transmitting power, an apparatus
designed in the manner indicated is undoubtedly free from grave objection;
but immediately any of those provisions is neglected, trouble is likely to
ensue, for the heat will not disappear from the place of actual reaction at the
necessary speed. Apparent proof that heat is not accumulating unduly in a
water-jacketed carbide container even when the generator is evolving gas at
a fair speed is easy to obtain; for if, as usually happens, the end of the
container through which the carbide is inserted is exposed to the air, the
hand may be placed upon it, and it will be found to be only slightly warm to
the touch. Such a test, however, is inconclusive, and frequently misleading,
because if more than a pound or two of carbide is present as an undivided
mass, and if water is allowed to attack one portion of it, that particular
portion may attain a high temperature while the rest is comparatively cool:
and if the bulk of the carbide is comparatively cool, naturally the walls of
the containing vessel themselves remain practically unheated. Three causes

Page 61

work together to prevent this heat being dissipated through the walls of the
carbide vessel with sufficient rapidity. In the first place, calcium carbide
itself is a very bad conductor of heat. So deficient in heat-conducting power
is it that a lump a few inches in diameter may be raised to redness in a gas
flame at one spot, and kept hot for some minutes, while the rest of the mass
remains sufficiently cool to be held comfortably in the fingers. In the
second place, commercial carbide exists in masses of highly irregular
shape, so that when they are packed into any vessel they only touch at their
angles and edges; and accordingly, even if the material were a fairly good
heat conductor of itself, the air or gas present between each lump would act
as an insulator, protecting the second piece from the heat generated in the
first. In the third place, the calcium hydroxide produced as the by-product
when calcium carbide is decomposed by water occupies considerably more
space than the original carbide--usually two or three times as much space,
the exact figures depending upon the conditions in which it is formed--and
therefore a carbide container cannot advisedly be charged with more than
one-third the quantity of solid which it is apparently capable of holding.
The remaining two-thirds of the space is naturally full of air when the
container is first put into the generator, but the air is displaced by acetylene
as soon as gas production begins. Whether that space, however, is occupied
by air, by acetylene, or by a gradually growing loose mass of slaked lime,
each separate lump of hot carbide is isolated from its neighbours by a
material which is also a very bad heat conductor; and the heat has but little
opportunity of distributing itself evenly. Moreover, although iron or steel is
a notably better conductor of heat than any of the other substances present
in the carbide vessel, it is, as a metal, only a poor conductor, being
considerably inferior in this respect to copper. If heat dissipation were the
only point to be studied in the construction of an acetylene apparatus, far
better results might be obtained by the employment of copper for the walls
of the carbide container; and possibly in that case a generator of
considerable size, fitted with a water- jacketed decomposing vessel, might
be free from the trouble of overheating. Nevertheless it will be seen in
Chapter VI. that the use of copper is not permissible for such purposes, its
advantages as a good conductor of heat being neutralised by its more
important defects.

Page 62

When suitable precautions are not taken to remove the heat liberated in an
acetylene apparatus, the temperature of the calcium carbide occasionally
rises to a remarkable degree. Investigating this point, Caro has studied the
phenomena of heat production in a "dipping" generator-- i.e., an apparatus
in which a cage of carbide is alternately immersed in and lifted out of a
vessel containing water. Using a generator designed to supply five burners,
he has found a maximum recording thermometer placed in the gas space of
the apparatus to give readings generally between 60° and 100° C.; but in
two tests out of ten he obtained temperatures of about 160° C. To determine
the actual temperature of the calcium carbide itself, he scattered amongst
the carbide charge fragments of different fusible metallic alloys which were
known to melt or soften at certain different temperatures. In all his ten tests
the alloys melting at 120° C. were fused completely; in two tests other
alloys melting at 216° and 240° C. showed signs of fusion; and in one test
an alloy melting at 280° C. began to soften. Working with an experimental
apparatus constructed on the "dripping" principle-- i.e., a generator in which
water is allowed to fall in single drops or as a fine stream upon a mass of
carbide--with the deliberate object of ascertaining the highest temperatures
capable of production when calcium carbide is decomposed in this
particular fashion, and employing for the measurement of the heat a Le
Chatelier thermo-couple, with its sensitive wires lying among the carbide
lumps, Lewes has observed a maximum temperature of 674° C. to be
reached in 19 minutes when water was dripped upon 227 grammes of
carbide at a speed of about 8 grammes per minute. In other experiments he
used a laboratory apparatus designed upon the "dipping" principle, and
found maximum temperatures, in four different trials, of 703°, 734°, 754°,
and 807° C., which were reached in periods of time ranging from 12 to 17
minutes. Even allowing for the greater delicacy of the instrument adopted
by Lewes for measuring the temperature in comparison with the device
employed by Caro, there still remains an astonishing difference between
Caro's maximum of 280° and Lewes' maximum of 807° C. The explanation
of this discrepancy is to be inferred from what has just been said. The
generator used by Caro was properly made of metal, was quite small in size,
was properly designed with some skill to prevent overheating as much as
possible, and was worked at the speed for which it was intended--in a word,
it was as good an apparatus as could be made of this particular type. Lewes'
generator was simply a piece of glass and metal, in which provisions to

Page 63

avoid overheating were absent; and therefore the wide difference between
the temperatures noted does not suggest any inaccuracy of observation or
experiment, but shows what can be done to assist in the dissipation of heat
by careful arrangement of parts. The difference in temperature between the
acetylene and the carbide in Caro's test accentuates the difficulty of gauging
the heat in a carbide vessel by mere external touch, and supplies
experimental proof of the previous assertions as to the low heat-conducting
power of calcium carbide and of the gases of the decomposing vessel. It
must not be supposed that temperatures such as Lewes has found ever occur
in any commercial generator of reasonably good design and careful
construction; they must be regarded rather as indications of what may
happen in an acetylene apparatus when the phenomena accompanying the
evolution of gas are not understood by the maker, and when all the
precautions which can easily be taken to avoid excessive heating have been
omitted, either by building a generator with carbide in excess too large in
size, or by working it too rapidly, or more generally by adopting a system of
construction unsuited to the ends in view. The fact, however, that Lewes has
noted the production of a temperature of 807° C. is important; because this
figure is appreciably above the point 780° C., at which acetylene
decomposes into its elements in the absence of air.

Nevertheless the production of a temperature somewhat exceeding 100° C.
among the lumps of carbide actually undergoing decomposition can hardly
be avoided in any practical generator. Based on a suggestion in the "Report
of the Committee on Acetylene Generators" which was issued by the British
Home Office in 1902, Fouché has proposed that 130° C., as measured with
the aid of fusible metallic rods, [Footnote: An alloy made by melting
together 55 parts by weight of commercial bismuth and 45 parts of lead
fuses at 127° C., and should be useful in performing the tests.] should be
considered the maximum permissible temperature in any part of a generator
working at full speed for a prolonged period of time. Fouché adopts this
figure on the ground that 130° C. sensibly corresponds with the temperature
at which a yellow substance is formed in a generator by a process of
polymerisation; and, referring to French conditions, states that few actual
apparatus permit the development of so high a temperature. As a matter of
fact, however, a fairly high temperature among the carbide is less important
than in the gas, and perhaps it would be better to say that the temperature in

Page 64

any part of a generator occupied by acetylene should not exceed 100° C.
Fraenkel has carried out some experiments upon the temperature of the
acetylene immediately after evolution in a water-to-carbide apparatus
containing the carbide in a subdivided receptacle, using an apparatus now
frequently described as belonging to the "drawer" system of construction.
When a quantity of about 7 lb. of carbide was distributed between 7
different cells of the receptacle, each cell of which had a capacity of 25
fluid oz., and the apparatus was caused to develop acetylene at the rate of 7
cubic feet per hour, maximum thermometers placed immediately over the
carbide in the different cells gave readings of from 70° to 90° C., the
average maximum temperature being about 80° C. Hence the Austrian code
of rules issued in 1905 governing the construction of acetylene apparatus
contains a clause to the effect that the temperature in the gas space of a
generator must never exceed 80° C.; whereas the corresponding Italian code
contains a similar stipulation, but quotes the maximum temperature as 100°
C. (vide Chapter IV.).

It is now necessary to see why the production of an excessively high
temperature in an acetylene generator has to be avoided. It must be avoided,
because whenever the temperature in the immediate neighbourhood of a
mass of calcium carbide which is evolving acetylene under the attack of
water rises materially above the boiling-point of water, one or more of three
several objectionable effects is produced--(a) upon the gas generated, (b)
upon the carbide decomposed, and (c) upon the general chemical reaction
taking place.

It has been stated above that in moat generators when the action between
the carbide and the water is proceeding smoothly, it occurs according to
equation (2)--

(2) CaC_2 + 2H_2O = C_2H_2 + Ca(OH)_2

rather than in accordance with equation (1)--

(1) CaC_2 + H_2O = C_2H_2 + CaO.

This is because calcium oxide, or quicklime, the by-product in (1), has
considerable affinity for water, evolving a noteworthy quantity of heat when

Page 65

it combines with one molecule of water to form one molecule of calcium
hydroxide, or slaked lime, the by-product in (2). If, then, a small amount of
water is added to a large amount of calcium carbide, the corresponding
quantity of acetylene may be liberated on the lines of equation (1), and
there will remain behind a mixture of unaltered calcium carbide, together
with a certain amount of calcium oxide. Inasmuch as both these substances
possess an affinity for water (setting heat free when they combine with it),
when a further limited amount of water is introduced into the mixture some
of it will probably be attracted to the oxide instead of to the carbide present.
It is well known that at ordinary temperatures quicklime absorbs moisture,
or combines with water, to produce slaked lime; but it is equally well
known that in a furnace, at about a red heat, slaked lime gives up water and
changes into quicklime. The reaction, in fact, between calcium oxide and
water is reversible, and whether those substances combine or dissociate is
simply a question of temperature. In other words, as the temperature rises,
the heat of hydration of calcium oxide diminishes, and calcium hydroxide
becomes constantly a less stable material. If now it should happen that the
affinity between calcium carbide and water should not diminish, or should
diminish in a lower ratio than the affinity between calcium oxide and water
as the temperature of the mass rises from one cause or other, it is
conceivable that at a certain temperature calcium carbide might be capable
of withdrawing the water of hydration from the molecule of slaked lime,
converting the latter into quicklime, and liberating one molecule of
acetylene, thus--

(3) CaC_2 + Ca_2(OH) = C_2H_2 + 2CaO.

It has been proved that a reaction of this character does occur, the
temperature necessary to determine it being given by Lewes as from 420° to
430° C., which is not much more than half that which he found in a
generator having carbide in excess, albeit one of extremely bad design.
Treating this reaction in the manner previously adopted, the thermo-
chemical phenomena of equation (3) are:

_Heat liberated._ | _Heat liberated._
|
Formation of 2CaO 290.0 | Formation of acetylene
58.1

Page 66

| Decomposition of Ca(OH)_2 [1]
229.1
| Decomposition of carbide
3.9
Balance 1.1 |
______ |
_____
|
291.1 |
291.1

[1 Footnote: Into its elements, Ca, O_2, and H_2; cf. footnote, p: 31.]

Or, since the calcium hydroxide is only dehydrated without being entirely
decomposed, and only one molecule of water is broken up, it may be
written:

Formation of CaO 145.0 | Formation of acetylene
58.1
| Decomposition of Ca(OH)_2
15.1
| Decomposition of water
69.0
Balance 1.1 | Decomposition of carbide
3.9
_____ |
_____
|
146.1 |
146.1

which comes to the same thing. Putting the matter in another shape, it may
be said that the reaction between calcium carbide and water is exothermic,
evolving either 14.0 or 29.1 calories according as the byproduct is calcium
oxide or solid calcium hydroxide; and therefore either reaction proceeds
without external assistance in the cold. The reaction between carbide and
slaked lime, however, is endothermic, absorbing 1.1 calories; and therefore
it requires external assistance (presence of an elevated temperature) to start
it, or continuous introduction of heat (as from the reaction between the rest
of the carbide present and the water) to cause it to proceed. Of itself, and
were it not for the disadvantages attending the production of a temperature
remotely approaching 400° C. in an acetylene generator, which

Page 67

disadvantages will be explained in the following paragraphs, there is no
particular reason why reaction (3) should not be permitted to occur, for it
involves (theoretically) no loss of acetylene, and no waste of calcium
carbide. Only one specific feature of the reaction has to be remembered,
and due practical allowance made for it. The reaction represented by
equation (2) proceeds almost instantaneously when the calcium carbide is
of ordinarily good quality, and the acetylene resulting therefrom is wholly
generated within a very few minutes. Equation (3), on the contrary,
consumes much time for its completion, and the gas corresponding with it is
evolved at a gradually diminishing speed which may cause the reaction to
continue for hours--a circumstance that may be highly inconvenient or quite
immaterial according to the design of the apparatus. When, however, it is
desired to construct an automatic acetylene generator, i.e., an apparatus in
which the quantity of gas liberated has to be controlled to suit the
requirements of any indefinite number of burners in use on different
occasions, equation (3) becomes a very important factor in the case. To
determine the normal reaction (No. 2) of an acetylene generator, 64 parts by
weight of calcium carbide must react with 36 parts of water to yield 26
parts by weight of acetylene, and apparently both carbide and water are
entirely consumed; but if opportunity is given for the occurrence of reaction
(3), another 64 parts by weight of carbide may be attacked, without the
addition of any more water, producing, inevitably, another 26 parts of
acetylene. If, then, water is in chemical excess in the generator, all the
calcium carbide present will be decomposed according to equation (2), and
the action will take place without delay; after a few minutes' interval the
whole of the acetylene capable of liberation will have been evolved, and
nothing further can possibly happen until another charge of carbide is
inserted in the apparatus. If, on the other hand, calcium carbide is in
chemical excess in the generator, all the water run in will be consumed
according to equation (2), and this action will again take place without
delay; but unless the temperature of the residual carbide has been kept well
below 400° C., a further evolution of gas will occur which will not cease for
an indeterminate period of time, and which, by strict theory, given the
necessary conditions, might continue until a second volume of acetylene
equal to that liberated at first had been set free. In practice this phenomenon
of a secondary production of gas, which is known as "after-generation," is
regularly met with in all generators where the carbide is in excess of the

Page 68

water added; but the amount of acetylene so evolved rarely exceeds one-
quarter or one-third of the main make. The actual amount evolved and the
rate of evolution depend, not merely upon the quantity of undecomposed
carbide still remaining in contact with the damp lime, but also upon the
rapidity with which carbide naturally decomposes in presence of liquid
water, and the size of the lumps. Where "after-generation" is caused by the
ascent of water vapour round lumps of carbide, the volume of gas produced
in a given interval of time is largely governed by the temperature prevailing
and the shape of the apparatus. It is evident that even copious "after-
generation" is a matter of no consequence in any generator provided with a
holder to store the gas, assuming that by some trustworthy device the
addition of water is stopped by the time that the holder is two-thirds or
three-quarters full. In the absence of a holder, or if the holder fitted is too
small to serve its proper purpose, "aftergeneration" is extremely
troublesome and sometimes dangerous, but a full discussion of this subject
must be postponed to the next chapter.

EFFECT OF HEAT ON ACETYLENE.--The effect of excessive retention
of heat in an acetylene generator upon the gas itself is very marked, as
acetylene begins spontaneously to suffer change, and to be converted into
other compounds at elevated temperatures. Being a purely chemical
phenomenon, the behaviour of acetylene when exposed to heat will be fully
discussed in Chapter VI. when the properties of the gas are being
systematically dealt with. Here it will be sufficient to assume that the
character of the changes taking place is understood, and only the practical
results of those changes as affecting the various components of an acetylene
installation have to be studied. According to Lewes, acetylene commences
to "polymerise" at a temperature of about 600° C., when it is converted into
other hydrocarbons having the same percentage composition, but containing
more atoms of carbon and hydrogen in their molecules. The formula of
acetylene is C_2H_2 which means that 2 atoms of carbon and 2 atoms of
hydrogen unite to form 1 molecule of acetylene, a body evidently
containing roughly 92.3 per cent. by weight of carbon and 7.7 per cent. by
weight of hydrogen. One of the most noteworthy substances produced by
the polymerisation of acetylene is benzene, the formula of which is
C_6H_6, and this is formed in the manner indicated by the equation--

Page 69

(4) 3C_2H_2 = C_6H_6.

Now benzene also contains 92.3 per cent. of carbon and 7.7 per cent. by
weight of hydrogen in its composition, but its molecule contains 6 atoms of
each element. When the chemical formula representing a compound body
indicates a substance which is, or can be obtained as, a gas or vapour, it
convoys another idea over and above those mentioned on a previous page.
The formula "C_2H_2," for example, means 1 molecule, or 26 parts by
weight of acetylene, just as "H_2" means 1 molecule, or 2 parts by weight
of hydrogen; but both formulæ also mean equal parts by volume of the
respective substances, and since H_2 must mean 2 volumes, being twice H,
which is manifestly 1, C_2H_2 must mean 2 volumes of acetylene as well.
Thus equation (4) states that 6 volumes of acetylene, or 3 x 26 parts by
weight, unite to form 2 volumes of benzene, or 78 parts by weight. If these
hydrocarbons are burnt in air, both are indifferently converted into carbon
dioxide (carbonic acid gas) and water vapour; and, neglecting for the sake
of simplicity the nitrogen of the atmosphere, the processes may be shown
thus:

(5) 2C_2H_2 + 5O_2 = 4CO_2 + 2H_2O.

(6) 2C_6H_6 + 15O_2 = 12CO_2 + 6H_2O.

Equation (5) shows that 4 volumes of acetylene combine with 10 volumes
of oxygen to produce 8 volumes of carbon dioxide and 4 of water vapour;
while equation (6) indicates that 4 volumes of benzene combine with 30
volumes of oxygen to yield 24 volumes of carbon dioxide and 12 of water
vapour. Two parts by volume of acetylene therefore require 5 parts by
volume of oxygen for perfect combustion, whereas two parts by volume of
benzene need 15--i.e., exactly three times as much. In order to work
satisfactorily, and to develop the maximum of illuminating power from any
kind of gas consumed, a gas-burner has to be designed with considerable
skill so as to attract to the base of the flame precisely that volume of air
which contains the quantity of oxygen necessary to insure complete
combustion, for an excess of air in a flame is only less objectionable than a
deficiency thereof. If, then, an acetylene burner is properly constructed, as
most modern ones are, it draws into the flame air corresponding with two
and a half volumes of oxygen for every one volume of acetylene passing

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from the jets; whereas if it were intended for the combustion of benzene
vapour it would have to attract three times that quantity. Since any flame
supplied with too little air tends to emit free carbon or soot, it follows that
any well-made acetylene burner delivering a gas containing benzene vapour
will yield a more or lens smoky flame according to the proportion of
benzene in the acetylene. Moreover, at ordinary temperatures benzene is a
liquid, for it boils at 81° C., and although, as was explained above in the
case of water, it is capable of remaining in the state of vapour far below its
boiling-point so long as it is suspended in a sufficiency of some permanent
gas like acetylene, if the proportion of vapour in the gas at any given
temperature exceeds a certain amount the excess will be precipitated in the
liquid form; while as the temperature falls the proportion of vapour which
can be retained in a given volume of gas also diminishes to a noteworthy
extent. Should any liquid, be it water or benzene, or any other substance,
separate from the acetylene under the influence of cold while the gas is
passing through pipes, the liquid will run downwards to the lowest points in
those pipes; and unless due precautions are taken, by the insertion of draw-
off cocks, collecting wells, or the like, to withdraw the deposited water or
other liquid, it will accumulate in all bends, angles, and dips till the pipes
are partly or completely sealed against the passage of gas, and the lights
will either "jump" or be extinguished altogether. In the specific case of an
acetylene generator this trouble is very likely to arise, even when the gas is
not heated sufficiently during evolution for polymerisation to occur and
benzene or other liquid hydrocarbons to be formed, because any excess of
water present in the decomposing vessel is liable to be vaporised by the heat
of the reaction--as already stated it is desirable that water shall be so
vaporised--and will remain safely vaporised as long as the pipes are kept
warm inside or near the generator; but directly the pipes pass away from the
hot generator the cooling action of the air begins, and some liquid water
will be immediately produced. Like the phenomenon of after- generation,
this equally inevitable phenomenon of water condensation will be either an
inconvenience or source of positive danger, or will be a matter of no
consequence whatever, simply as the whole acetylene installation, including
the service-pipes, is ignorantly or intelligently built.

As long as nothing but pure polymerisation happens to the acetylene, as
long, that is to say, as it is merely converted into other hydrocarbons also

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having the general formula C_(2n)H_(2n), no harm will be done to the gas
as regards illuminating power, for benzene burns with a still more luminous
flame than acetylene itself; nor will any injury result to the gas if it is
required for combustion in heating or cooking stoves beyond the fact that
the burners, luminous or atmospheric, will be delivering a material for the
consumption of which they are not properly designed. But if the
temperature should rise much above the point at which benzene is the most
conspicuous product of polymerisation, other far more complicated changes
occur, and harmful effects may be produced in two separate ways. Some of
the new hydrocarbons formed may interact to yield a mixture of one or
more other hydrocarbons containing a higher proportion of carbon than that
which is present in acetylene and benzene, together with a corresponding
proportion of free hydrogen; the former will probably be either liquids or
solids, while the latter burns with a perfectly non-luminous flame. Thus the
quantity of gas evolved from the carbide and passed into the holder is less
than it should be, owing to the condensation of its non-gaseous constituents.
To quote an instance of this, Haber has found 15 litres of acetylene to be
reduced in volume to 10 litres when the gas was heated to 638° C. By other
changes, some "saturated hydrocarbons," i.e., bodies having the general
formula C_nH_(2n+2), of which methane or marsh-gas, CH_4 is the best
known, may be produced; and those all possess lower illuminating powers
than acetylene. In two of those experiments already described, where Lewes
observed maximum temperatures ranging from 703° to 807° C., samples of
the gas which issued when the heat was greatest were submitted to chemical
analysis, and their illuminating powers were determined. The figures he
gives are as follows:

I. II.
Per Cent. Per Cent.
Acetylene 70.0 69.7
Saturated hydrocarbons 11.3 11.4
Hydrogen 18.7 18.9
_____ _____

100.0 100.0

The average illuminating power of these mixed gases is about 126 candles
per 5 cubic feet, whereas that of pure acetylene burnt under good laboratory

Page 72

conditions is 240 candles per 5 cubic feet. The product, it will be seen, had
lost almost exactly 50 per cent. of its value as an illuminant, owing to the
excessive heating to which it had been, exposed. Some of the liquid
hydrocarbons formed at the same time are not limpid fluids like benzene,
which is less viscous than water, but are thick oily substances, or even tars.
They therefore tend to block the tubes of the apparatus with great
persistence, while the tar adheres to the calcium carbide and causes its
further attack by water to be very irregular, or even altogether impossible.
In some of the very badly designed generators of a few years back this tarry
matter was distinctly visible when the apparatus was disconnected for
recharging, for the spent carbide was exceptionally yellow, brown, or
blackish in colour, [Footnote: As will be pointed out later, the colour of the
spent lime cannot always be employed as a means for judging whether
overheating has occurred in a generator.] and the odour of tar was as
noticeable as that of crude acetylene.

There is another effect of heat upon acetylene, more calculated to be
dangerous than any of those just mentioned, which must not be lost sight of.
Being an endothermic substance, acetylene is prone to decompose into its
elements--

(7) C_2H_2 -> C_2 + H_2

whenever it has the opportunity; and the opportunity arrives if the
temperature of the gas risen to 780° C., or if the pressure under which the
gas is stored exceeds two atmospheres absolute (roughly 30 lb. per square
inch). It decomposes, be it carefully understood, in the complete absence of
air, directly the smallest spark of red-hot material or of electricity, or
directly a gentle shock, such as that of a fall or blow on the vessel holding
it, is applied to any volume of acetylene existing at a temperature exceeding
780° or at a gross pressure of 30 lb. per square inch; and however large that
volume may be, unless it is contained in tubes of very small diameter, as
will appear hereafter, the decomposition or dissociation into its elements
will extend throughout the whole of the gas. Equation (7) states that 2
volumes of acetylene yield 2 volumes of hydrogen and a quantity of carbon
which would measure 2 volumes were it obtained in the state of gas, but
which, being a solid, occupies a space that may be neglected. Apparently,

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therefore, the dissociation of acetylene involves no alteration in volume,
and should not exhibit explosive effects. This is erroneous, because 2
volumes of acetylene only yield exactly 2 volumes of hydrogen when both
gases are measured at the same temperature, and all gases increase in
volume as their temperature rises. As acetylene is endothermic and evolves
much heat on decomposition, and as that heat must primarily be
communicated to the hydrogen, it follows that the latter must be much
hotter than the original acetylene; the hydrogen accordingly strives to fill a
much larger space than that occupied by the undecomposed gas, and if that
gas is contained in a closed vessel, considerable internal pressure will be set
up, which may or may not cause the vessel to burst.

What has been said in the preceding paragraph about the temperature at
which acetylene decomposes is only true when the gas is free from any
notable quantity of air. In presence of air, acetylene inflames at a much
lower temperature, viz., 480° C. In a manner precisely similar to that of all
other combustible gases, if a stream of acetylene issues into the atmosphere,
as from the orifices of a burner, the gas catches fire and burns quietly
directly any substance having a temperature of 480° C. or upwards is
brought near it; but if acetylene in bulk is mixed with the necessary quantity
of air to support combustion, and any object exceeding 480° C. in
temperature comes in contact with it, the oxidation of the hydrocarbon
proceeds at such a high rate of speed as to be termed an explosion. The
proportion of air needed to support combustion varies with every
combustible material within known limits (cf. Chapter VI.), and according
to Eitner the smallest quantity of air required to make acetylene burn or
explode, as the case may be, is 25 per cent. If, by ignorant design or by
careless manipulation, the first batches of acetylene evolved from a freshly
charged generator should contain more than 25 per cent. of air; or if in the
inauguration of a new installation the air should not be swept out of the
pipes, and the first makes of gas should become diluted with 25 to 50 per
cent. of air, any glowing body whose temperature exceeds 480° C. will fire
the gas; and, as in the former instance, the flame will extend all through the
mass of acetylene with disastrous violence and at enormous speed unless
the gas is stored in narrow pipes of extremely small diameter. Three
practical lessons are to be learnt from this circumstance: first, tobacco-
smoking must never be permitted in any building where an escape of raw

Page 74

acetylene is possible, because the temperature of a lighted cigar, &c.,
exceeds 480° C.; secondly, a light must never be applied to a pipe
delivering acetylene until a proper acetylene burner has been screwed into
the aperture; thirdly, if any appreciable amount of acetylene is present in the
air, no operation should be performed upon any portion of an acetylene
plant which involves such processes as scraping or chipping with the aid of
a steel tool or shovel. If, for example, the iron or stoneware sludge-pipe is
choked, or the interior of the dismantled generator is blocked, and attempts
are made to remove the obstruction with a hard steel tool, a spark is very
likely to be formed which, granting the existence of sufficient acetylene in
the air, is perfectly able to fire the gas. For all such purposes wooden
implements only are best employed; but the remark does not apply to the
hand-charging of a carbide-to-water generator through its proper shoot.
Before passing to another subject, it may be remarked that a quantity of air
far less than that which causes acetylene to become dangerous is
objectionable, as its presence is apt to reduce the illuminating power of the
gas unduly.

EFFECT OF HEAT ON CARBIDE.--Chemically speaking, no amount of
heat possible of attainment in the worst acetylene generator can affect
calcium carbide in the slightest degree, because that substance may be
raised to almost any temperature short of those distinguishing the electric
furnace, without suffering any change or deterioration. In the absence of
water, calcium carbide is as inert a substance as can well be imagined: it
cannot be made to catch fire, for it is absolutely incombustible, and it can
be heated in any ordinary flame for reasonable periods of time, or thrown
into any non-electrical furnace without suffering in the least. But in
presence of water, or of any liquid containing water, matters are different. If
the temperature of an acetylene generator rises to such an extent that part of
the gas is polymerised into tar, that tar naturally tends to coat the residual
carbide lumps, and, being greasy in character, more or less completely
protects the interior from further attack. Action of this nature not only
means that the acetylene is diminished in quantity and quality by partial
decomposition, but it also means that the make is smaller owing to
imperfect decomposition of the carbide: while over and above this is the
liability to nuisance or danger when a mass of solid residue containing
some unaltered calcium carbide is removed from the apparatus and thrown

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away. In fact, whenever the residue of a generator is not so saturated with
excess of water as to be of a creamy consistency, it should be put into an
uncovered vessel in the open air, and treated with some ten times its volume
of water before being run into any drain or closed pipe where an
accumulation of acetylene may occur. Even at temperatures far below those
needed to determine a production of tar or an oily coating on the carbide, if
water attacks an excess of calcium carbide somewhat rapidly, there is a
marked tendency for the carbide to be "baked" by the heat produced; the
slaked lime adhering to the lumps as a hard skin which greatly retards the
penetration of more water to the interior.

COLOUR OF SPENT CARBIDE.--In the early days of the industry, it was
frequently taken for granted that any degradation in the colour of the spent
lime left in an acetylene generator was proof that overheating had taken
place during the decomposition of the carbide. Since both calcium oxide
and hydroxide are white substances, it was thought that a brownish, greyish,
or blackish residue must necessarily point to incipient polymerisation of the
gas. This view would be correct if calcium carbide were prepared in a state
of chemical purity, for it also is a white body. Commercial carbide,
however, is not pure; it usually contains some foreign matter which tints the
residue remaining after gasification. When a manufacturer strives to give
his carbide the highest gas-making power possible he frequently increases
the proportion of carbon in the charge submitted to electric smelting, until a
small excess is reached, which remains in the free state amongst the
finished carbide. After decomposition the fine particles of carbon stain the
moist lime a bluish grey tint, the depth of shade manifestly depending upon
the amount present. If such a sludge is copiously diluted with water,
particles of carbon having the appearance and gritty or flaky nature of coke
often rise to the surface or fall to the bottom of the liquid; whence they can
easily be picked out and identified as pure or impure carbon by simple tests.
Similarly the lime or carbon put into the electric furnace may contain small
quantities of compounds which are naturally coloured; and which,
reappearing in the sludge either in their original or in a different state of
combination, confer upon the sludge their characteristic tinge. Spent lime of
a yellowish brown colour is frequently to be met with in circumstances that
are clearly no reproach to the generator. Doubtless the tint is due to the
presence of some coloured metallic oxide or other compound which has

Page 76

escaped reduction in the electric furnace. The colour which the residual
lime afterwards assumes may not be noticeable in the dry carbide before
decomposition, either because some change in the colour-giving impurity
takes place during the chemical reactions in the generator or because the
tint is simply masked by the greyish white of the carbide and its free
carbon. Hence it follows that a bad colour in the waste lime removed from a
generator only points to overheating and polymerisation of the acetylene
when corroborative evidence is obtained--such as a distinct tarry smell, the
actual discovery of oily or tarry matters elsewhere, or a grave reduction in
the illuminating power of the gas.

MAXIMUM ATTAINABLE TEMPERATURES.--In order to discover the
maximum temperature which can be reached in or about an acetylene
generator when an apparatus belonging to one of the best types is fed at a
proper rate with calcium carbide in lumps of the most suitable size, the
following calculation may be made. In the first place, it will be assumed
that no loss of heat by radiation occurs from the walls of the generator;
secondly, the small quantity of heat taken up by the calcium hydroxide
produced will be ignored; and, thirdly, the specific heat of acetylene will be
assumed to be 0.25, which is about its most probable value. Now, a hand-
fed carbide-to-water generator will work with half a gallon of water for
every 1 lb. of carbide decomposed, quantities which correspond with 320
grammes of water per 64 grammes (1 molecular weight) of carbide. Of
those 320 grammes of water, 18 are chemically destroyed, leaving 302. The
decomposition of 64 grammes of commercial carbide evolves 28 large
calories of heat. Assuming all the heat to be absorbed by the water, 28
calories would raise 302 grammes through (28 X 1000 / 302) = 93° C., i.e.,
from 44.6° F. to the boiling-point. Assuming all the heat to be
communicated to the acetylene, those 28 calories would raise the 26
grammes of gas liberated through (28 X 1000 / 26 / 0.25) = 4308° C., if that
were possible. But if, as would actually be the case, the heat were
distributed uniformly amongst the 302 grammes of water and the 20
grammes of acetylene, both gas and water would be raised through the same
number of degrees, viz., 90.8° C. [Footnote: Let x = the number of large
calories absorbed by the water; then 28 - x = those taken up by the gas.
Then--

Page 77

1000x / 302 = 1000 (28 - x) / (26 X 0.25)

whence x = 27.41; and 28 - x = 0.59.

Therefore, for water, the rise in temperature is--

27.41 X 1000 / 302 = 90.8° C.;

and for acetylene the rise is--

0.59 X 1000 / 26 / 0.25 = 90.8° C.]

If the generator were designed on lines to satisfy the United States Fire
Underwriters, it would contain 8.33 lb. of water to every 1 lb. of carbide
attacked; identical calculations then showing that the original temperature
of the water and gas would be raised through 53.7° C. Provided the carbide
is not charged into such an apparatus in lumps of too large a size, nor at too
high a rate, there will be no appreciable amount of local overheating
developed; and nowhere, therefore, will the rise in temperature exceed 91°
in the first instance, or 54° C. in the second. Indeed it will be considerably
smaller than this, because a large proportion of the heat evolved will be lost
by radiation through the generator walls, while another portion will be
converted from sensible into latent heat by causing part of the water to pass
off as vapour with the acetylene.

EFFECT OF HIGH TEMPERATURES ON GENERATORS.--As the
temperature amongst the carbide in any generator in which water is not
present in large excess may easily reach 200° C. or upwards, no material
ought to be employed in the construction of such generators which is not
competent to withstand a considerable amount of heat in perfect safety. The
ordinary varieties of soft solder applied with the bitt in all kinds of light
metal-work usually melt, according to their composition, at about 180° C.;
and therefore this method of making joints is only suitable for objects that
are never raised appreciably in temperature above the boiling-point of
water. No joint in an acetylene generator, the partial or complete failure of
which would radically affect the behaviour of the apparatus, by permitting
the charges of carbide and of water to come into contact at an abnormal rate
of speed, by allowing the acetylene to escape directly through the crack into

Page 78

the atmosphere, or by enabling the water to run out of the seal of any vessel
containing gas so as to set up a free communication between that vessel and
the air, ought ever to be made of soft solder--every joint of this character
should be constructed either by riveting, by bolting, or by doubly folding
the metal sheets. Apparently, a joint constantly immersed in water on one
side cannot rise in temperature above the boiling-point of the liquid, even
when its other side is heated strongly; but since, even if a generator is not
charged with naturally hard water, its fluid contents soon become "hard" by
dissolution of lime, there is always a liability to the deposition of water
scale over the joint. Such water scale is a very bad heat conductor, as is seen
in steam boilers, so that a seam coated with an exceedingly thin layer of
scale, and heated sharply on one side, will rise above the boiling-point of
water even if the liquid on its opposite side is ice-cold. For a while the film
of scale may be quite water-tight, but after it has been heated by contact
with the hot metal several times it becomes brittle and cracks without
warning. But there is a more important reason for avoiding the use of
plumbers' solder. It might seem that as the natural hard, protective skin of
the metal is liable to be injured or removed by the bending or by the drilling
or punching which precedes the insertion of the rivets or studs, an
application of soft solder to such a joint should be advantageous. This is not
true because of the influence of galvanic action. As all soft solders consist
largely of lead, if a joint is soldered, a "galvanic couple" of lead and iron, or
of lead and zinc (when the apparatus is built of galvanised steel), is exposed
to the liquid bathing it; and since in both cases the lead is highly electro-
negative to the iron or zinc, it is the iron or zinc which suffers attack,
assuming the liquid to possess any corrosive properties whatever.
Galvanised iron which has been injured during the joint-making presents a
zinc-iron couple to the water, but the zinc protects the iron; if a lead solder
is present, the iron will begin to corrode immediately the zinc has
disappeared. In the absence of lead it is the less important metal, but in the
presence of lead it is the more important (the foundation) metal which is the
soluble element of the couple. Where practicable, joints in an acetylene
generator may safely be made by welding or by autogenous soldering
("burning"), because no other metal is introduced into the system; any other
process, except that of riveting or folding, only hastens destruction of the
plant. The ideal method of making joints about an acetylene generator is
manifestly that of autogenous soldering, because, as will appear in Chapter

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IX. of this book, the most convenient and efficient apparatus for performing
the operation is the oxy-acetylene blow-pipe, which can be employed so as
to convert two separate pieces of similar metal into one homogeneous
whole.

In less critical situations in an acetylene plant, such as the partitions of a
carbide container, &c., where the collapse of the seam or joint would not be
followed by any of the effects previously suggested, there is less cause for
prohibiting the use of unfortified solder; but even here, two or three rivets,
just sufficient to hold the metal in position if the solder should give way, are
advisedly put into all apparatus. In other portions of an acetylene
installation where a merely soldered joint is exposed to warm damp gas
which is in process of cooling, instead of being bathed in hard water, an
equal, though totally dissimilar, danger is courted. The main constituent of
such solders that are capable of being applied with the bitt is lead; lead is
distinctly soluble in soft or pure water; and the water which separates by
condensation out of a warm damp gas is absolutely soft, for it has been
distilled. If condensation takes place at or near a soldered joint in such a
way that water trickles over the solder, by slow degrees the metallic lead
will be dissolved and removed, and eventually a time will come when the
joint is no longer tight to gas. In fact, if an acetylene installation is of more
than very small dimensions, e.g., when it is intended to supply any building
as large as, or larger than, the average country residence, if it is to give
satisfaction to both constructor and purchaser by being quite trustworthy
and, possessed of a due lease of life, say ten or fifteen years, it must be built
of stouter materials than the light sheets which alone are suitable for
manipulation with the soldering-iron or for bending in the ordinary type of
metal press. Sound cast-iron, heavy sheet-metal, or light boiler-plate is the
proper substance of which to construct all the important parts of a generator,
and the joints in wrought metal must be riveted and caulked or soldered
autogeneously as mentioned above. So built, the installation becomes much
more costly to lay down than an apparatus composed of tinplate, zinc, or
thin galvanised iron, but it will prove more economical in the long run. It is
not too much to say that if ignorant and short-sighted makers in the earliest
days of the acetylene industry had not recommended and supplied to their
customers lightly built apparatus which has in many instances already
begun to give trouble, to need repairs, and to fail by thorough corrosion--

Page 80

apparatus which frequently had nothing but cheapness in its favour--the use
of the gas would have spread more rapidly than it has done, and the public
would not now be hearing of partial or complete failures of acetylene
installations. Each of these failures, whether accompanied by explosions
and injury to persons or not, acts more powerfully to restrain a possible new
customer from adopting the acetylene light, than several wholly successful
plants urge him to take it up; for the average member of the public is not in
a position to distinguish properly between the collapse of a certain
generator owing to defective design or construction (which reflects no
discredit upon the gas itself), and the failure of acetylene to show in
practice those advantages that have been ascribed to it. One peculiar and
noteworthy feature of acetylene, often overlooked, is that the apparatus is
constructed by men who may have been accustomed to gas-making plant all
their lives, and who may understand by mere habit how to superintend a
chemical operation; but the same apparatus is used by persons who
generally have no special acquaintance with such subjects, and who, very
possibly, have not even burnt coal-gas at any period of their lives. Hence it
happens that when some thoughtless action on the part of the country
attendant of an acetylene apparatus is followed by an escape of gas from the
generator, and by an accumulation of that gas in the house where the plant
is situated, or when, in disregard of rules, he takes a naked light into the
house and an explosion follows, the builder dismisses the episode as a piece
of stupidity or wilful misbehaviour for which he can in nowise be held
morally responsible; whereas the builder himself is to blame for designing
an apparatus from which an escape of gas can be accompanied by sensible
risks to property or life. However unpalatable this assertion may be, its truth
cannot be controverted; because, short of criminal intention or insanity on
the part of the attendant, it is in the first place a mere matter of knowledge
and skill so to construct an acetylene plant that an escape of gas is
extremely unlikely, even when the apparatus is opened for recharging, or
when it is manipulated wrongly; and in the second place, it is easy so to
arrange the plant that any disturbance of its functions which may occur
shall be followed by an immediate removal of the surplus gas into a place
of complete safety outside and above the generator-house.

GENERATION AT LOW TEMPERATURES.--In all that has been said
hitherto about the reaction between calcium carbide and water being

Page 81

instantaneous, it has been assumed that the two substances are brought
together at or about the usual temperature of an occupied room, i.e., 15
degrees C. If, however, the temperature is materially lower than this, the
speed of the reaction falls off, until at -5 degrees C., supposing the water
still to remain liquid, evolution of acetylene practically ceases. Even at the
freezing-point of pure water gas is produced but slowly; and if a lump of
carbide is thrown on to a block of ice, decomposition proceeds so gently
that the liberated acetylene may be ignited to form a kind of torch, while
heat is generated with insufficient rapidity to cause the carbide to sink into
the block. This fact has very important bearings upon the manipulation of
an acetylene generator in winter time. It is evident that unless precautions
are taken those portions of an apparatus which contain water are liable to
freeze on a cold night; because, even if the generator has been at work
producing gas (and consequently evolving heat) till late in the evening, the
surplus heat stored in the plant may escape into the atmosphere long before
more acetylene has to be made, and obviously while frost is still reigning in
the neighbourhood. If the water freezes in the water store, in the pipes
leading therefrom, in the holder seal, or in the actual decomposing chamber,
a fresh batch of gas is either totally incapable of production, because the
water cannot be brought into contact with the calcium carbide in the
apparatus, or it can only be generated with excessive slowness because the
carbide introduced falls on to solid ice. Theoretically, too, there is a
possibility that some portion of the apparatus--a pipe in particular--may be
burst by the freezing, owing to the irresistible force with which water
expands when it changes into the solid condition. Probably this last
contingency, clearly accompanied as it would be by grave risk, is somewhat
remote, all the plant being constructed of elastic material; but in practice
even a simple interference with the functions of a generator by freezing,
ideally of no special moment, is highly dangerous, because of the great
likelihood that hurried and wholly improper attempts to thaw it will be
made by the attendant. As it has been well known for many years that the
solidifying point of water can be lowered to almost any degree below
normal freezing by dissolving in it certain salts in definite proportions, one
of the first methods suggested for preventing the formation of ice in an
acetylene generator was to employ such a salt, using, in fact, for the
decomposition of the carbide some saline solution which remains liquid
below the minimum night temperature of the winter season. Such a process,

Page 82

however, has proved unsuitable for the purpose in view; and the explanation
of that fact is found in what has just been stated: the "water" of the
generator may admittedly be safely maintained in the fluid state, but from
so cold a liquid acetylene will not be generated smoothly, if at all.
Moreover, were it not so, a process of this character is unnecessarily
expensive, although suitable salts are very cheap, for the water of the
generator is constantly being consumed, [Footnote: It has already been said
that most generators "consume" a much larger volume of water than the
amount corresponding with the chemical reaction involved: the excess of
water passing into the sludge or by- product. Thus a considerable quantity
of any anti-freezing agent must be thrown aside each time the apparatus is
cleaned out or its fluid contents are run off.] and as constantly needs
renewal; which means that a fresh batch of salt would be required every
time the apparatus was recharged, so long as frost existed or might be
expected. A somewhat different condition obtains in the holder of an
acetylene installation. Here, whenever the holder is a separate item in the
plant, not constituting a portion of the generating apparatus, the water
which forms the seal of a rising holder, or which fills half the space of a
displacement holder, lasts indefinitely; and it behaves equally well,
whatever its temperature may be, so long as it retains a fluid state. This
matter will be discussed with greater detail at the end of Chapter III. At
present the point to be insisted on is that the temperature in any constituent
of an acetylene installation which contains water must not be permitted to
fall to the freezing-point; while the water actually used for decomposition
must be kept well above that temperature.

GENERATION AT HIGH TEMPERATURES.--At temperatures largely
exceeding those of the atmosphere, the reaction between calcium carbide
and water tends to become irregular; while at a red heat steam acts very
slowly upon carbide, evolving a mixture of acetylene and hydrogen in place
of pure acetylene. But since at pressures which do not materially exceed
that of the atmosphere, water changes into vapour at 100° C., above that
temperature there can be no question of a reaction between carbide and
liquid water. Moreover, as has been pointed out, steam or water vapour will
continue to exist as such at temperatures even as low as the freezing-point
so long as the vapour is suspended among the particles of a permanent gas.
Between calcium carbide and water vapour a double decomposition occurs

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chemically identical with that between carbide and liquid water; but the
physical effect of the reaction and its practical bearings are considerably
modified. The quantity of heat liberated when 30 parts by weight of steam
react with 64 parts of calcium carbide should be essentially unaltered from
that evolved when the reagent is in the liquid state; but the temperature
likely to be attained when the speed of reaction remains the same as before
will be considerably higher for two conspicuous reasons. In the first place,
the specific heat of steam in is only 0.48, while that of liquid water is 1.0.
Hence, the quantity of heat which is sufficient to raise the temperature of a
given weight of liquid water through n thermometric degrees, will raise the
temperature of the same weight of water vapour through rather more than 2
n degrees. In the second place, that relatively large quantity of heat which in
the case of liquid water merely changes the liquid into a vapour, becoming
"latent" or otherwise unrecognisable, and which, as already shown, forms
roughly five-sixths of the total heat needed to convert cold water into steam,
has no analogue if the water has previously been vaporised by other means;
and therefore the whole of the heat supplied to water vapour raises its
sensible temperature, as indicated by the thermometer. Thus it appears that,
except for the sufficient amount of cooling that can be applied to a large
vessel containing carbide by surrounding it with a water jacket, there is no
way of governing its temperature satisfactorily if water vapour is allowed to
act upon a mass of carbide--assuming, of course, that the reaction proceeds
at any moderate speed, e.g., at a rate much above that required to supply
one or two burners with gas.

The decomposition which with perfect chemical accuracy has been stated to
occur quantitatively between 36 parts by weight, of water and 64 parts of
calcium carbide scarcely ever takes place in so simple a fashion in an actual
generator. Owing to the heat developed when carbide is in excess, about
half the water is converted into vapour; and so the reaction proceeds in two
stages: half the water added reacting with the carbide as a liquid, the other
half, in a state of vapour, afterwards reacting similarly, [Footnote: This
secondary reaction is manifestly only another variety of the phenomenon
known as "after-generation" (cf. ante). After-generation is possible between
calcium carbide and mechanically damp slaked lime, between carbide and
damp gas, or between carbide and calcium hydroxide, as opportunity shall
serve. In all cases the carbide must be in excess.] or hardly reacting at all, as

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the case may be. Suppose a vessel, A B, somewhat cylindrical in shape, is
charged with carbide, and that water is admitted at the end called A.
Suppose now (1) that the exit for gas is at the opposite end, B. As the lumps
near A are attacked by half the liquid introduced, while the other half is
changed into steam, a current, of acetylene and water vapour travels over
the charge lying between the decomposing spot and the end B. During its
passage the second half of the water, as vapour, reacts with the excess of
carbide, the first make of acetylene being dried, and more gas being
produced. Thus a second quantity of heat is developed, equal by theory to
that previously evolved; but a second elevation in temperature, far more
serious, and far less under control, than the former also occurs; and this is
easily sufficient to determine some of those undesirable effects already
described. Digressing for a moment, it may be admitted that the desiccation
of the acetylene produced in this manner is beneficial, even necessary; but
the advantages of drying the gas at this period of its treatment are
outweighed by the concomitant disadvantages and by the later inevitable
remoistening thereof. Suppose now (2) that both the water inlet and the gas
exit of the carbide cylinder are at the same end, A. Again half the added
water, as liquid, reacts with the carbide it first encounters, but the hot
stream of damp gas is not permitted to travel over the rest of the lumps
extending towards B: it is forced to return upon its steps, leaving B
practically untouched. The gas accordingly escapes from the cylinder at A
still loaded with water vapour, and for a given weight of water introduced
much less acetylene is evolved than in the former case. The gas, too, needs
drying somewhere else in the plant; but these defects are preferable to the
apparent superiority of the first process because overheating is, or can be,
more thoroughly guarded against.

PRESSURE IN GENERATORS.--Inasmuch as acetylene is prone to
dissociate or decompose into its elements spontaneously whenever its
pressure reaches 2 atmospheres or 30 lb. per square inch, as well as when
its temperature at atmospheric pressure attains 780° C., no pressure
approaching that of 2 atmospheres is permissible in the generator. A due
observance of this rule, however, unlike a proper maintenance of a low
temperature in an acetylene apparatus, is perfectly easy to arrange for. The
only reason for having an appreciable positive pressure in any form of
generating plant is that the gas may be compelled to travel through the pipes

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and to escape from the burner orifices; and since the plant is only installed
to serve the burners, that pressure which best suits the burners must be
thrown by the generator or its holder. Therefore the highest pressure it is
ever requisite to employ in a generator is a pressure sufficient (a) to lift the
gasholder bell, or to raise the water in a displacement holder, (b) to drive
the gas through the various subsidiary items in the plant, such as washers
and purifiers, (c) to overcome the friction in the service-pipes, [Footnote:
This friction manifestly causes a loss of pressure, i.e., a fall in pressure, as a
gas travels along a pipe; and, as will be shown in Chapter VII., it is the fall
in pressure in a pipe rather than the initial pressure at which a gas enters a
pipe that governs the volume of gas passing through that pipe. The proper
behaviour and economic working of a burner (acetylene or other, luminous
or incandescent) naturally depend upon the pressure in the pipe to which the
burner is immediately attached being exactly suited to the design of that
burner, and have nothing to do with the fall in pressure occurring in the
delivery pipes. It is therefore necessary to keep entirely separate the ideas of
proper burner pressure and of maximum desirable fall in pressure within the
service due to friction.] and (d) to give at the points of combustion a
pressure which is required by the particular burners adopted. In all except
village or district installations, (c) may be virtually neglected. When the
holder has a rising bell, (a) represents only an inch or so of water; but if a
displacement holder is employed the pressure needed to work it is entirely
indeterminate, being governed by the size and shape of the said holder. It
will be argued in Chapter III. that a rising holder is always preferable to one
constructed on the displacement principle. The pressure (d) at the burners
may be taken at 4 inches of water as a maximum, the precise figure being
dependent upon the kind of burners--luminous, incandescent, boiling, &c.--
attached to the main. The pressure (b) also varies according to
circumstances, but averages 2 or 3 inches. Thus a pressure in the generator
exceeding that of the atmosphere by some 12 inches of water--i.e., by about
7 oz., or less than half a pound per square inch--is amply sufficient for
every kind of installation, the less meritorious generators with displacement
holders only excepted. This pressure, it should be noted, is the net or
effective pressure, the pressure with which the gas raises the liquid in a
water-gauge glass out of the level while the opposite end of the water
column is exposed to the atmosphere. The absolute pressure in a vessel
containing gas at an effective pressure of 12 inches of water is 7 oz. plus the

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normal, insensible pressure of the atmosphere itself--say 15-1/4 lb. per
square inch. The liquid in a barometer which measures the pressure of the
atmosphere stands at a height of 30 inches only, because that liquid is
mercury, 13.6 times as heavy as water. Were it filled with water the
barometer would stand at (30 X 13.6) = 408 inches, or 34 feet,
approximately. Gas pressures are always measured in inches of water
column, because expressed either as pounds per square inch or as inches of
mercury, the figures would be so small as to give decimals of unwieldy
length.

It would of course be perfectly safe so to arrange an acetylene plant that the
pressure in the generating chamber should reach the 100 inches of water
first laid down by the Home Office authorities as the maximum allowable.
There is, however, no appreciable advantage to be gained by so doing, or by
exceeding that pressure which feeds the burners best. Any higher original
pressure involves the use of a governor at the exit of the plant, and a
governor is a costly and somewhat troublesome piece of apparatus that can
be dispensed with in most single installations by a proper employment of a
well-balanced rising holder.

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CHAPTER III
THE GENERAL PRINCIPLES OF ACETYLENE
GENERATION--ACETYLENE GENERATING APPARATUS

Inasmuch as acetylene is produced by the mere interaction of calcium
carbide and water, that is to say, by simply bringing those two substances in
the cold into mutual contact within a suitable closed space, and inasmuch as
calcium carbide can always be purchased by the consumer in a condition
perfectly fit for immediate decomposition, the preparation of the gas, at
least from the theoretical aspect, is characterised by extreme simplicity. A
cylinder of glass or metal, closed at one end and open at the other, filled
with water, and inverted in a larger vessel containing the same liquid, may
be charged almost instantaneously with acetylene by dropping into the basin
a lump of carbide, which sinks to the bottom, begins to decompose, and
evolves a rapid current of gas, displacing the water originally held in the
inverted cylinder or "bell." If a very minute hole is drilled in the top of the
floating bell, acetylene at once escapes in a steady stream, being driven out
by the pressure of the cylinder, the surplus weight of which causes it to
descend into the water of the basin as rapidly as gas issues from the orifice.
As a laboratory experiment, and provided the bell has been most carefully
freed from atmospheric air in the first instance, this escaping gas may be set
light to with a match, and will burn with a more or loss satisfactory flame of
high illuminating power. Such is an acetylene generator stripped of all
desirable or undesirable adjuncts, and reduced to its most elementary form;
but it is needless to say that so simple an apparatus would not in any way
fulfil the requirements of everyday practice.

Owing to the inequality of the seasons, and to the irregular nature of the
demand for artificial light and heat in all households, the capacity of the
plant installed for the service of any institution or district must be amply
sufficient to meet the consumption of the longest winter evening--for, as
will be shown in the proper place, attempts to make an acetylene generator
evolve gas more quickly than it is designed to do are fraught with many

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objections--while the operation of the plant, must be under such thorough
control that not only can a sudden and unexpected demand for gas be met
without delay, but also that a sudden and unexpected interruption or
cessation of the demand shall not be followed by any disturbance in the
working of the apparatus. Since, on the one hand, acetylene is produced in
large volumes immediately calcium carbide is wetted with water, so that the
gas may be burnt within a minute or two of its first evolution; and, on the
other, that acetylene once prepared can be stored without trouble or
appreciable waste for reasonable periods of time in a water-sealed gasholder
closely resembling, in everything but size, the holders employed on coal-
gas works; it follows that there are two ways of bringing the output of the
plant into accord with the consumption of the burners. It is possible to make
the gas only as and when it is required, or it is possible in the space of an
hour or so, during the most convenient part of the day, to prepare sufficient
to last an entire evening, storing it in a gasholder till the moment arrives for
its combustion. It is clear that an apparatus needing human attention
throughout the whole period of activity would be intolerable in the case of
small installations, and would only be permissible in the case of larger ones
if the district supplied with gas was populous enough to justify the regular
employment of two men at least in or about the generating station. But with
the conditions obtaining in such a country as Great Britain, and in other
lands where coal is equally cheap and accessible, if a neighbourhood was as
thickly populated as has been suggested, it would be preferable on various
grounds to lay down a coal- gas or electricity works; for, as has been shown
in the first chapter, unless a very material fall in the price of calcium carbide
should take place--a fall which at present is not to be expected--acetylene
can only be considered a suitable and economical illuminant and heating
agent for such places as cannot be provided cheaply with coal-gas or
electric current. To meet this objection, acetylene generators have been
invented in which, broadly speaking, gas is only produced when it is
required, control of the chemical reaction devolving upon some mechanical
arrangement. There are, therefore, two radically different types of acetylene
apparatus to be met with, known respectively as "automatic" and "non-
automatic" generators. In a non-automatic generator the whole of the
calcium carbide put into the apparatus is more or less rapidly decomposed,
and the entire volume of gas evolved from it is collected in a holder, there
to await the moment of consumption. In an automatic apparatus, by means

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of certain devices which will be discussed in their proper place, the act of
turning on a burner-tap causes some acetylene to be produced, and the act
of turning it off brings the reaction to an end, thus obviating the necessity
for storage. That, at any rate, is the logical definition of the two
fundamentally different kinds of generator: in automatic apparatus the
decomposition of the carbide is periodically interrupted in such fashion as
more or less accurately to synchronise with the consumption of gas; in the
non-automatic variety decomposition proceeds without a break until the
carbide vessels are empty. Unfortunately a somewhat different
interpretation of these two words has found frequent acceptance, a
generator being denominated non-automatic or automatic according as the
holder attached to it is or is not large enough to store the whole of the
acetylene which the charge of carbide is capable of producing if it is
decomposed all at once. Apart from the fact that a holder, though desirable,
is not an absolutely indispensable part of an acetylene plant, the definition
just quoted was sufficiently free from objection in the earliest days of the
industry; but now efficient commercial generators are to be met with which
become either automatic or non-automatic according to the manner of
working them, while some would be termed non-automatic which comprise
mechanism of a conspicuously self- acting kind.

AUTOMATIC AND NON-AUTOMATIC GENERATORS.--Before
proceeding to a detailed description of the various devices which may be
adopted to render an acetylene generator automatic in action, the relative
advantages of automatic and non-automatic apparatus, irrespective of type,
from the consumer's point of view may be discussed. The fundamental idea
underlying the employment of a non-automatic generator is that the whole
of the calcium carbide put into the apparatus shall be decomposed into
acetylene as soon after the charge is inserted as is natural in the
circumstances; so that after a very brief interval of time the generating
chambers shall contain nothing but spent lime and water, and the holder be
as full of gas as is ever desirable. In an automatic apparatus, the
fundamental idea is that the generating chamber, or one at least of several
generating chambers, shall always contain a considerable quantity of
undecomposed carbide, and some receptacle always contain a store of water
ready to attack that carbide, so that whenever a demand for gas shall arise
everything may be ready to meet it. Inasmuch as acetylene is an

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inflammable gas, it possesses all the properties characteristic of
inflammable gases in general; one of which is that it is always liable to take
fire in presence of a spark or naked light, and another of which is that it is
always liable to become highly explosive in presence of a naked light or
spark if, accidentally or otherwise, it becomes mixed with more than a
certain proportion of air. On the contrary, in the complete absence of liquid
or vaporised water, calcium carbide is almost as inert a body as it is possible
to imagine: for it will not take fire, and cannot in any circumstances be
made to explode. Hence it may be urged that a non-automatic generator,
with its holder always containing a large volume of the actually
inflammable and potentially explosive acetylene, must invariably be more
dangerous than an automatic apparatus which has less or practically no
ready-made gas in it, and which simply contains water in one chamber and
unaltered calcium carbide in another. But when the generating vessels and
the holder of a non-automatic apparatus are properly designed and
constructed, the gas in the latter is acetylene practically free from air, and
therefore while being, as acetylene inevitably is, inflammable, is devoid of
explosive properties, always assuming, as must be the case in a water-
sealed holder, that the temperature of the gas is below 780° C.; and also
assuming, as must always be the case in good plant, that the pressure under
which the gas is stored remains less than two atmospheres absolute. It is
perfectly true that calcium carbide is non-inflammable and non-explosive,
that it is absolutely inert and incapable of change; but so comprehensive an
assertion only applies to carbide in its original drum, or in some impervious
vessel to which moisture and water have no access. Until it is exhausted, an
automatic acetylene generator contains carbide in one place and water in
another, dependence being put upon some mechanical arrangement to
prevent the two substances coming into contact prematurely. Many of the
devices adopted by builders of acetylene apparatus for keeping the carbide
and water separate, and for mixing them in the requisite quantities when the
proper time arrives, are as trustworthy, perhaps, as it is possible for any
automatic gear to be; but some are objectionably complicated, and a few are
positively inefficient. There are two difficulties which the designer of
automatic mechanism has to contend with, and it is doubtful whether he
always makes a sufficient allowance for them. The first is that not only
must calcium carbide and liquid water be kept out of premature contact, but
that moisture, or vapour of water, must not be allowed to reach the carbide;

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or alternatively, that if water vapour reaches the carbide too soon, the
undesired reaction shall not determine overheating, and the liberated gas be
not wasted or permitted to become a source of danger. The second difficulty
encountered by the designer of automata is so to construct his apparatus that
it shall behave well when attended to by completely unskilled labour, that it
shall withstand gross neglect and resist positive ill-treatment or
mismanagement. If the automatic principle is adopted in any part of an
acetylene apparatus it must be adopted throughout, so that as far as
possible--and with due knowledge and skill it is completely possible--
nothing shall be left dependent upon the memory and common sense of the
gasmaker. For instance, it must not be necessary to shut a certain tap, or to
manipulate several cocks before opening the carbide vessel to recharge it; it
must not be possible for gas to escape backwards out of the holder; and
either the carbide-feed gear or the water-supply mechanism (as the case
may be) must be automatically locked by the mere act of taking the cover
off the carbide store, or of opening the sludge-cock at the bottom. It would
be an advantage, even, if the purifiers and other subsidiary items of the
plant were treated similarly, arranging them in such fashion that gas should
be automatically prevented from escaping out of the rest of the apparatus
when any lid was removed. In fact, the general notion of interlocking,
which has proved so successful in railway signal-cabins and in carburetted
water gas-plant for the prevention of accidents duo to carelessness or
overnight, might be copied in principle throughout an acetylene installation
whenever the automatic system is employed.

It is no part of the present argument, to allege that automatic generators are,
and must always be, inherently dangerous. Automatic devices of a suitable
kind may be found in plenty which are remarkably simple and highly
trustworthy; but it would be too bold a statement to say that any such
arrangement is incapable of failure, especially when put into the hands of a
person untrained in the superintendence of machinery. The more reliable a
piece of automatic mechanism proves itself to be, the more likely is it to
give trouble and inconvenience and utterly to destroy confidence when it
does break down; because the better it has behaved in the past, and the
longer it has lasted without requiring adjustment, the less likely is it that the
attendant will be at hand when failure occurs. By suitable design and by an
intelligent employment of safety-valves and blow-off pipes (which will be

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discussed in their proper place) it is quite easy to avoid the faintest
possibility of danger arising from an increase of pressure or an improper
accumulation of gas inside the plant or inside the building containing the
plant; but every time such a safety-valve or blow-off pipe comes into action
a waste of gas occurs, which means a sacrifice of economy, and shows that
the generator is not working as it should.

As glass is a fragile and brittle substance, and as it is not capable of bearing
large, rapid, and oft-repeated alterations of temperature in perfect safety, it
is not a suitable material for the construction of acetylene apparatus or of
portions thereof. Hence it follows that a generator must be built of some
non-transparent material which prevents the interior being visible when the
apparatus is at work. Although it is comparatively easy, by the aid of a lamp
placed outside the generator- shed in such a position as to throw its beams
of light through a window upon the plant inside, to charge a generator after
dark; and although it is possible, without such assistance, by methodical
habits and a systematic arrangement of utensils inside the building to charge
a generator even in perfect darkness, such an operation is to be deprecated,
for it is apt to lead to mistakes, it prevents any slight derangement in the
installation from being instantly noticed, and it offers a temptation to the
attendant to break rules and to take a naked light with him. On all those
grounds, therefore, it is highly desirable that every manipulation connected
with a generator shall be effected during the daytime, and that the
apparatus-house shall be locked up before nightfall. But owing to the
irregular habits engendered by modern life it is often difficult to know,
during any given day, how much gas will be required in the ensuing
evening; and it therefore becomes necessary always to have, as ready-made
acetylene, or as carbide in a proper position for instant decomposition, a
patent or latent store of gas more than sufficient in quantity to meet all
possible requirements. Now, as already stated, a non-automatic apparatus
has its store of material in the form of gas in a holder; and since this is
preferably constructed on the rising or telescopic principle, a mere
inspection of the height of the bell--on which, if preferred, a scale
indicating its contents in cubic feet or in burner-hours may be marked--
suffices to show how near the plant is to the point of exhaustion. In many
types of automatic apparatus the amount of carbide remaining
undecomposed at any moment is quite unknown, or at best can only be

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deduced by a tedious and inexact calculation; although in some generators,
where the store of carbide is subdivided into small quantities, or placed in
several different receptacles, an inspection of certain levers or indicators
gives an approximate idea as to the capacity of the apparatus for further gas
production. In any case the position of a rising holder is the most obvious
sign of the degree of exhaustion of a generator; and therefore, to render
absolutely impossible a failure of the light during an evening, a non-
automatic generator fitted with a rising holder is best.

Since calcium carbide is a solid body having a specific gravity of 2.2, water
being unity, and since 1 cubic foot of water weighs 62.4 lb., in round
numbers 137 lb. of compact carbide only occupy 1 cubic foot of space.
Again, since acetylene is a gas having a specific gravity of 0.91, air being
unity, and since the specific gravity of air, water being unity, is 0.0013, the
specific gravity of acetylene, water being unity, is roughly O.00116. Hence
1 cubic foot of acetylene weighs roughly 0.07 lb. Furthermore, since 1 lb. of
good carbide evolves 5 cubic feet of gas on decomposition with water,
acetylene stored at atmospheric pressure occupies roundly 680 times as
much space as the carbide from which it has been evolved. This figure by
no means represents the actual state of affairs in a generator, because, as
was explained in the previous chapter, a carbide vessel cannot be filled
completely with solid; and, indeed, were it so "filled," in ordinary language,
much of its space would be still occupied with air. Nevertheless it is
incontrovertible that an acetylene plant calculated to supply so many
burners for so long a period of time must be very much larger if it is
constructed on the non-automatic principle, when the carbide is
decomposed all at once, than if the automatic system is adopted, when the
solid remains unattacked until a corresponding quantity of gas is required
for combustion. Clearly it is the storage part of a non-automatic plant alone
which must be so much larger; the actual decomposing chambers may be of
the same size or even smaller, according to the system of generation to
which the apparatus belongs. In practice this extra size of the non-automatic
plant causes it to exhibit two disadvantages in comparison with automatic
apparatus, disadvantages which are less serious than they appear, or than
they may easily be represented to be. In the first place, the non- automatic
generator requires more space for its erection. If acetylene were an
illuminating agent suitable for adoption by dwellers in city or suburb, where

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the back premises and open-air part of the messuage are reduced to minute
proportions or are even non-existent, this objection might well be fatal. But
acetylene is for the inhabitant of a country village or the occupier of an
isolated country house; and he has usually plenty of space behind his
residence which he can readily spare. In the second place, the extra size of
the non-automatic apparatus makes it more expensive to construct and more
costly to instal. It is more cosily to construct and purchase because of its
holder, which must be well built on a firm foundation and accurately
balanced; it is more costly to instal because a situation must be found for
the erection of the holder, and the apparatus-house may have to be made
large enough to contain the holder as well as the generator itself. As regards
the last point, it may be said at once that there is no necessity to place the
holder under cover: it may stand out of doors, as coal-gas holders do in
England, for the seal of the tank can easily be rendered frost-proof, and the
gas itself is not affected by changes of atmospheric temperature beyond
altering somewhat in volume. In respect of the other objections, it must be
remembered that the extra expense is one of capital outlay alone, and
therefore only increases the cost of the light by an inappreciable amount,
representing interest and depreciation charges on the additional capital
expenditure. The increased cost of a year's lighting due to these charges will
amount to only 10 or 15 per cent, on the additional capital sunk. The extra
capital sunk does not in any way increase the maintenance charges; and if,
by having a large holder, additional security and trustworthiness are
obtained, or if the holder leads to a definite, albeit illusive, sense of extra
security and trustworthiness, the additional expenditure may well be
permissible or even advantageous.

The argument is sometimes advanced that inasmuch as for the same, or a
smaller, capital outlay as is required to instal a non-automatic apparatus
large enough to supply at one charging the maximum amount of light and
heat that can ever be needed on the longest winter's night, an automatic
plant adequate to make gas for two or three evenings can be laid down, the
latter must be preferable, because the attendant, in the latter case, will only
need to enter the generator-house two or three times a week. Such an
argument is defective because it ignores the influence of habit upon the
human being. A watch which must be wound every day, or a clock which
must be wound every week, on a certain day of the week, is seldom

Page 95

permitted to run down; but a watch requiring to be re-wound every other
day, or a fourteen-day clock (used as such), would rarely be kept going.
Similarly, an acetylene generator might be charged once a week or once a
day without likelihood of being forgotten; but the operation of charging at
irregular intervals would certainly prove a nuisance. With a non-automatic
apparatus containing all its gas in the holder, the attendant would note the
position of the bell each morning, and would introduce sufficient carbide to
fill the holder full, or partly full, as the case might be; with an automatic
apparatus he would be tempted to trust that the carbide holders still
contained sufficient material to last another night.

The automatic system of generating acetylene has undoubtedly one
advantage in those climates where frost tends to occur frequently, but only
to prevail for a short period. As the apparatus is in operation during the
evening hours, the heat evolved will, or can be made to, suffice to protect
the apparatus from freezing until the danger has passed; whereas if the gas
is generated of a morning in a non-automatic apparatus the temperature of
the plant may fall to that of the atmosphere before evening, and some
portion may freeze unless special precautions are taken to protect it.

It was shown in Chapter II that overheating is one of the chief troubles to be
guarded against in acetylene generators, and that the temperature attained is
a function of the speed at which generation proceeds. Seeing that in an
automatic apparatus the rate of decomposition depends on the rate at which
gas is being burnt, while in a non-automatic generator it is, or may be,
under no control, the critic may urge that the reaction must take place more
slowly and regularly, and the maximum temperature therefore be lower,
when the plant works automatically. This may be true if the non-automatic
generator is unskilfully designed or improperly manipulated; but it is quite
feasible to arrange an apparatus, especially one of the carbide-to-water or of
the flooded-compartment type, in such fashion that overheating to an
objectionable extent is rendered wholly impossible. In a non-automatic
apparatus the holder is nothing but a holder and may be placed wherever
convenient, even at a distance from the generating plant; in an automatic
apparatus the holder, or a small similarly constructed holder placed before
the main storage vessel, has to act as a water-supply governor, as the
releasing gear for certain carbide-food mechanism, or indeed as the motive

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power of such mechanism; and accordingly it must be close to the water or
carbide store, and more or less intimately connected by means of levers, or
the like, with the receptacle in which decomposition occurs. Sometimes the
holder surrounds, or is otherwise an integral part of, the decomposing
chamber, the whole apparatus being made self-contained or a single
structure with the object of gaining compactness. But it is evident that such
methods of construction render additionally awkward, or even hazardous,
any repair or petty operation to the generating portion of the plant; while the
more completely the holder is isolated from the decomposing vessels the
more easily can they be cleaned, recharged, or mended, without blowing off
the stored gas and without interfering with the action of any burners that
may be alight at the time. Owing to the ingenuity of inventors, and the
experience they have acquired in the construction of automatic acetylene
apparatus during the years that the gas has been in actual employment, it is
going too far boldly to assert that non-automatic generators are invariably to
be preferred before their rivals. Still in view of the nature of the labour
which is likely to be bestowed on any domestic plant, of the difficulty in
having repairs or adjustments done quickly in outlying country districts, and
of the inconvenience, if not risk, attending upon any failure of the
apparatus, the greater capital outlay, and the larger space required by non-
automatic generators are in most instances less important than the economy
in space and prime cost characteristic of automatic machines when the
defects of each are weighed fairly in the balance. Indeed, prolonged
experience tends to show that a selection between non-automatic and
automatic apparatus may frequently be made on the basis of capacity. A
small plant is undoubtedly much more convenient if automatic; a very large
plant, such as that intended for a public supply, is certainly better if non-
automatic, but between these two extremes choice may be exercised
according to local conditions.

CONTROL OF THE CHEMICAL REACTION.--Coming now to study the
principles underlying the construction of an acetylene generator more
closely it will be seen that as acetylene is produced by bringing calcium
carbide into contact with water, the chemical reaction may be started either
by adding the carbide to the water, or by adding the water to the carbide.
Similarly, at least from the theoretical aspect, the reaction, may be caused to
stop by ceasing to add carbide to water, or by ceasing to add water to

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carbide. Apparently if water is added by degrees to carbide, until the
carbide is exhausted, the carbide must always be in excess; and manifestly,
if carbide is added in small portions to water, the water must always be in
excess, which, as was argued in Chapter II., is emphatically the more
desirable position of affairs. But it in quite simple to have carbide present in
large excess of the water introduced when the whole generator is
contemplated, and yet to have the water always in chemical excess in the
desired manner; because to realise the advantages of having water in
excess, it is only necessary to subdivide the total charge of carbide into a
number of separate charges which are each so small that more than
sufficient water to decompose and flood one of them is permitted to enter
every time the feed mechanism comes into play, or (in a non-automatic
apparatus) every time the water-cock is opened; so arranging the charges
that each one is protected from the water till its predecessor, or its
predecessor, have been wholly decomposed. Thus it is possible to regard
either the carbide or the water as the substance which has to be brought into
contact with the other in specified quantity. It is perhaps permissible to
repeat that in the construction of an automatic generator there is no
advantage to be gained from regulating the supply of both carbide and
water, because just as the mutual decomposition will begin immediately any
quantity of the one meets any quantity of the other, so the reaction will
cease (except in one case owing to "after-generation") directly the whole of
that material which is not in chemical excess has been consumed-quite
independently of the amount of the other material left unattacked. Being a
liquid, and possessing as such no definite shape or form of its own
irrespective of the vessel in which it is held, water is by far the more
convenient of the two substances to move about or to deliver in
predetermined volume to the decomposing chamber. A supply of water can
be started instantaneously or cut oil as promptly by the movement of a cock
or valve of the usual description; or it may be allowed to run down a
depending pipe in obedience to the law of gravitation, and stopped from
running down such a pipe by opposing to its passage a gas pressure superior
to that gravitational force. In any one of several obvious ways the supply of
water to a mass of carbide may be controlled with absolute certainty, and
therefore it should apparently follow that the make of acetylene should be
under perfect control by controlling the water current. On the other hand,
unless made up into balls or cartridges of some symmetrical form, calcium

Page 98

carbide exists in angular masses of highly irregular shape and size. Its
lumps alter in shape and size directly liquid water or moisture reaches them;
a loose more or loss gritty powder, or a damp cohesive mud, being
produced which is well calculated to choke any narrow aperture or to jam
any moving valve. It is more difficult, therefore, by mechanical agency to
add a supply of carbide to a mass of water than to introduce a supply of
water to a stationary mass of carbide; and far more difficult still to bring the
supply of carbide under perfect control with the certainty that the movement
shall begin and stop immediately the proper time arrives.

But assuming the mechanical difficulties to be satisfactorily overcome, the
plan of adding carbide to a stationary mass of water has several chemical
advantages, first, because, however the generator be constructed, water will
be in excess throughout the whole time of gas production; and secondly,
because the evolution of acetylene will actually cease completely at the
moment when the supply of carbide is interrupted. There is, however, one
particular type of generator in which as a matter of fact the carbide is the
moving constituent, viz., the "dipping" apparatus (cf. infra), to which these
remarks do not apply; but this machine, as will be seen directly, is,
illogically perhaps, but for certain good reasons, classed among the water-
to-carbide apparatus. All the mechanical advantages are in favour, as just
indicated, of making water the moving substance; and accordingly, when
classified in the present manner, a great majority of the generators now on
the markets are termed water-to-carbide apparatus. Their disadvantages are
twofold, though these may be avoided or circumvented: in all types save
one the carbide is in excess at the immediate place and time of
decomposition; and in all types without exception the carbide in the whole
of the generator is in excess, so that the phenomenon of "after- generation"
occurs with more or less severity. As explained in the last chapter, after-
generation is the secondary production of acetylene which takes place more
or less slowly after the primary reaction is finished, proceeding either
between calcium hydroxide, merely damp lime, or damp gas and calcium
carbide, with an evolution of more acetylene. As it is possible, and indeed
usual, to fit a holder of some capacity even to an automatic generator, the
simple fact that more acetylene is liberated after the main reaction is over
does not matter, for the gas can be safely stored without waste and entirely
without trouble or danger. The real objection to after-generation is the

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difficulty of controlling the temperature and of dissipating the heat with
which the reaction is accompanied. It will be evident that the balance of
advantage, weighing mechanical simplicity against chemical superiority, is
somewhat even between carbide-to-water and water-to-carbide generators
of the proper type; but the balance inclines towards the former distinctly in
the ease of non-automatic apparatus, and points rather to the latter when
automatism is desired. In the early days of the industry it would have been
impossible to speak so favourably of automatic carbide-to-water generators,
for they were at first constructed with absurdly complicated and unreliable
mechanism; but now various carbide-feed gears have been devised which
seem to be trustworthy even when carbide not in cartridge form is
employed.

NON-AUTOMATIC CARBIDE-TO-WATER GENERATORS.--There is
little to be said in the present place about the principles underlying the
construction of non-automatic generators. Such apparatus may either be of
the carbide-to- water or the water-to-carbide type. In the former, lumps of
carbide are dropped by hand down a vertical or sloping pipe or shoot, which
opens at its lower end below the water-level of the generating chamber, and
which is fitted below its mouth with a deflector to prevent the carbide from
lodging immediately underneath that mouth. The carbide falls through the
water which stands in the shoot itself almost instantaneously, but during its
momentary descent a small quantity of gas is evolved, which produces an
unpleasant odour unless a ventilating hood is fixed above the upper end of
the tube. As the ratio of cubical contents to superficial area of a lump is
greater as the lump itself is larger, and as only the outer surface of the lump
can be attacked by the water in the shoot during its descent, carbide for a
hand-fed carbide-to-water generator should be in fairly large masses--
granulated material being wholly unsuitable--and this quite apart from the
fact that large carbide is superior to small in gas-making capacity, inasmuch
as it has not suffered the inevitable slight deterioration while being crushed
and graded to size. If carbide is dropped too rapidly into such a generator
which is not provided with a false bottom or grid for the lumps to rest upon,
the solid is apt to descend among a mass of thick lime sludge produced at a
former operation, which lies at the bottom of the decomposing chamber;
and here it may be protected from the cooling action of fresh water to such
an extent that its surface is baked or coated with a hard layer of lime, while

Page 100

overheating to a degree far exceeding the boiling-point of water may occur
locally. When, however, it falls upon a grid placed some distance above the
bottom of the water vessel, the various convection currents set up as parts
of the liquid become warm, and the mechanical agitations produced by the
upward current of gas rinse the spent lime from the carbide, and entirely
prevent overheating, unless the lumps are excessively large in size. If the
carbide charged into a hand-fed generator is in very large lumps there is
always a possibility that overheating may occur in the centre of the masses,
due to the baking of the exterior, even if the generator is fitted with a
reaction grid. Manifestly, when carbide in lumps of reasonable size is
dropped into excess of water which is not merely a thick viscid cream of
lime, the temperature cannot possibly exceed the boiling-point--i.e., 100°
C.--provided always the natural convection currents of the water are
properly made use of.

The defect which is, or rather which may be, characteristic of a hand-fed
carbide-to-water generator is a deficiency of gas yield due to solubility. At
atmospheric temperatures and pressure 10 volumes of water dissolve 11
volumes of acetylene, and were the whole of the water in a large generator
run to waste often, a sensible loss of gas would ensue. If the carbide falls
nearly to the bottom of the water column, the rising gas is forced to bubble
through practically the whole of the liquid, so that every opportunity is
given it to dissolve in the manner indicated till the liquid is completely
saturated. The loss, however, is not nearly so serious as is sometimes
alleged, because (1) the water becomes heated and so loses much of its
solvent power; and (2) the generator is worked intermittently, with
sufficiently long intervals to allow the spent lime to settle into a thick
cream, and only that thick cream is run off, which represents but a small
proportion of the total water present. Moreover, a hand-fed carbide-to-water
generator will work satisfactorily with only half a gallon [Footnote: The
United States National Board of Fire Underwriters stipulates for the
presence of 1 (American) gallon of water for every 1 lb. of carbide before
such an apparatus is "permitted." This quantity of liquid might retain nearly
4 per cent. of the total acetylene evolved. Even this is an exaggeration; for
neither her, nor in the corresponding figure given in the text, is any
allowance made for the diminution in solvent power of the water as it
becomes heated by the reaction.] of liquid present for every 1 lb. of carbide

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decomposed, and were all this water run off and a fresh quantity admitted
before each fresh introduction of carbide, the loss of acetylene by
dissolution could not exceed 2 per cent. of the total make, assuming the
carbide to be capable of yielding 5 cubic feet of gas per lb. Admitting,
however, that some loss of gas does occur in this manner, the defect is
partly, if not wholly, neutralised by the concomitant advantages of the
system: (1) granted that the generator is efficiently constructed,
decomposition of the carbide is absolutely complete, so that no loss of gas
occurs in this fashion; (2) the gas is evolved at a low temperature, so that it
is unaccompanied, by products of polymerisation, which may block the
leading pipes and must reduce the illuminating power; (3) the acetylene is
not mixed with air (as always happens at the first charging of a water-to-
carbide apparatus), which also lowers the illuminating power; and (4) the
gas is freed from two of its three chief impurities, viz., ammonia and
sulphuretted hydrogen, in the generating chamber itself. To prevent the loss
of acetylene by dissolution, carbide-to-water generators are occasionally
fitted with a reaction grid placed only just below the water-level, so that the
acetylene has no more than 1 inch or so of liquid to bubble through. The
principle is wrong, because hot water being lighter than cold, the upper
layers may be raised to the boiling-point, and even converted into steam,
while the bulk of the liquid still remains cold; and if the water actually
surrounding the carbide is changed into vapour, nearly all control over the
temperature attending the reaction is lost.

Page 102

The hand-fed carbide-to-water generator is very simple and, as already
indicated, has proved itself perhaps the best type of all for the construction
of very large installations; but the very simplicity of the generator has
caused it more than once to be built in a manner that has not given entire
satisfaction. As shown at L in Fig. 6, p. 84, the generator essentially consists
of a closed cylindrical vessel communicating at its top with a separate rising
holder. At one side as drawn, or disposed concentrically if so preferred, is
an open-mouthed pipe or shoot (American "shute") having its lower open
extremity below the water-level. Into this shoot are dropped by hand or
shovel lumps of carbide, which fall into the water and there suffer
decomposition. As the bottom of the shoot is covered with water, which,
owing to the small effective gas pressure in the generator given by the
holder, stands a few inches higher in the shoot than in the generator, gas
cannot escape from the shoot; because before it could do so the water in the
generator would have to fall below the level of the point a, being either
driven out through the shoot or otherwise. Since the point b of the shoot
extends further into the generator than a, the carbide drops centrally, and as
the bubbles of gas rise vertically, they have no opportunity of ascending
into the shoot. In practice, the generator is fitted with a conical bottom for
the collection of the lime sludge and with a cock or other aperture at the
apex of the cone for the removal of the waste product. As it is not desirable
that the carbide should be allowed to fall directly from the shoot into the
thicker portion of the sludge within the conical part of the generator, one or
more grids is usually placed in the apparatus as shown by the dotted lines in
the sketch. It does not seem that there is any particular reason for the
employment of more than one grid, provided the size of the carbide
decomposed is suited to the generator, and provided the mesh of the grid is
suited to the size of the carbide. A great improvement, however, is made if
the grid is carried on a horizontal spindle in such a way that it can be rocked
periodically in order to assist in freeing the lumps of carbide from the
adhering particles of lime. As an alternative to the movable grid, or even as
an adjunct thereto, an agitator scraping the conical sides of the generator
may be fitted which also assists in ensuring a reasonably complete absence
of undecomposed carbide from the sludge drawn off at intervals. A further
point deserves attention. If constructed in the ideal manner shown in Fig. 6
removal of some of the sludge in the generator would cause the level of the

Page 103

liquid to descend and, by carelessness, the level might fall below the point a
at the base of the shoot. In these circumstances, if gas were unable to return
from the holder, a pressure below that of the atmosphere would be
established in the gas space of the generator and air would be drawn in
through the shoot. This air might well prove a source of danger when
generation was started again. Any one of three plans may be adopted to
prevent the introduction of air. A free path may be left on the gas-main
passing from the generator to the holder so that gas may be free to return
and so to maintain the usual positive pressure in the decomposing vessel;
the sludge may be withdrawn into some vessel so small in capacity that the
shoot cannot accidentally become unsealed; or the waterspace of the
generator may be connected with a water-tank containing a ball-valve
attached to a constant service of water be that liquid runs in as quickly as
sludge is removed, and the level remains always at the same height. The
first plan is only a palliative and has two defects. In the first place, the
omission of any non-return valve between, the generator and the next item
in the train of apparatus is objectionable of itself; in the second place,
should a very careless attendant withdraw too much liquid, the shoot might
become unsealed and the whole contents of the holder be passed into the air
of the building containing the apparatus through the open mouth of the
shoot. The second plan is perfectly sound, but has the practical defect of
increasing the labour of cleaning the generator. The third plan is obviously
the best. It can indeed be adopted where no real constant service of water is
at hand by connecting the generator to a water reservoir of relatively large
size and by making the latter of comparatively large transverse area, in
proportion to its depth; so that the escape of even a largo volume of water
from the reservoir may not involve a large reduction in the level at which it
stands there.

The dust that always clings to lumps of carbide naturally decomposes with
extreme rapidity when the material is thrown into the shoot of a carbide- to-
water generator, and the sudden evolution of gas so produced has on more
than one occasion seriously alarmed the attendant on the plant. Moreover, to
a trifling extent the actual superficial layers of the carbide suffer attack
before the lumps reach the true interior of the generator, and a small loss of
gas thereby occurs through the open mouth of the shoot. To remove these
objections to the hand-fed generator it has become a common practice in

Page 104

large installations to cause the lower end of the shoot to dip under the level
of some oil contained in an appropriate receptacle, the carbide falling into a
basket carried upon a horizontal spindle. The basket and its support are so
arranged that when a suitable charge of carbide has been dropped into it, a
partial rotation of an external hand-wheel lifts the basket and carbide out of
the oil into an air-tight portion of the generator where the surplus oil can
drain away from the lumps. A further rotation of the hand-wheel then tips
the basket over a partition inside the apparatus, allowing the carbide to fall
into the actual decomposing chamber. This method of using oil has the
advantage of making the evolution of acetylene on a large scale appear to
proceed more quietly than usual, and also of removing the dust from the
carbide before it reaches the water of the generator. The oil itself obviously
does not enter the decomposing chamber to any appreciable extent and
therefore does not contaminate the final sludge. The whole process
accordingly lies to be favourably distinguished from those other methods of
employing oil in generators or in the treatment of carbide which are referred
to elsewhere in this book.

NON-AUTOMATIC WATER-TO-CARBIDE GENERATORS.--The only
principle underlying the satisfactory design of a non-automatic water-to-
carbide generator is to ensure the presence of water in excess at the spot
where decomposition is taking place. This may be effected by employing
what is known as the "flooded-compartment" system of construction, i.e.,
by subdividing the total carbide charge into numerous compartments
arranged either vertically or horizontally, and admitting the water in
interrupted quantities, each more than sufficient thoroughly to decompose
and saturate the contents of one compartment, rather than in a slow, steady
stream. It would be quite easy to manage this without adopting any
mechanism of a moving kind, for the water might be stored in a tank kept
full by means of a ball-valve, and admitted to an intermediate reservoir in a
slow, continuous current, the reservoir being fitted with an inverted syphon,
on the "Tantalus-cup" principle, so that it should first fill itself up, and then
suddenly empty into the pipe leading to the carbide container. Without this
refinement, however, a water-to-carbide generator, with subdivided charge,
behaves satisfactorily as long as each separate charge of carbide is so small
that the heat evolved on its decomposition can be conducted away from the
solid through the water- jacketed walls of the vessel, or as the latent heat of

Page 105

steam, with sufficient rapidity. Still it must be remembered that a water-to-
carbide generator, with subdivided charge, does not belong to the flooded-
compartment type if the water runs in slowly and continuously: it is then
simply a "contact" apparatus, and may or may not exhibit overheating, as
well as the inevitable after-generation. All generators of the water-to-
carbide type, too, must yield a gas containing some air in the earlier
portions of their make, because the carbide containers can only be filled
one-third or one-half full of solid. Although the proportion of air so passed
into the holder may be, and usually is, far too small in amount to render the
gas explosive or dangerous in the least degree, it may well be sufficient to
reduce the illuminating power appreciably until it is swept out of the service
by the purer gas subsequently generated. Moreover, all water-to-carbide
generators are liable, as just mentioned, to produce sufficient overheating to
lower the illuminating power of the gas whenever they are wilfully driven
too fast, or when they are reputed by their makers to be of a higher
productive capacity than they actually should be; and all water-to-carbide
generators, excepting those where the carbide is thoroughly soaked in water
at some period of their operation, are liable to waste gas by imperfect
decomposition.

DEVICES TO SECURE AUTOMATIC ACTION,--The devices which are
commonly employed to render a generator automatic in action, that is to
say, to control the supply of one of the two substances required in the
intermittent evolution of gas, may be divided into two broad classes: (A)
those dependent upon the position of a rising-holder bell, and (B) those
dependent upon the gas pressure inside the apparatus. As the bell of a rising
holder descends in proportion as its gaseous contents are exhausted, it may
(A^1) be fitted with some laterally projecting pin which, arrived at a certain
position, actuates a series of rods or levers, and either opens a cock on the
water-supply pipe or releases a mechanical carbide-feed gear, the said cock
being closed again or the feed-gear thrown out of action when the pin,
rising with the bell, once more passes a certain position, this time in its
upward path. Secondly (A^2), the bell may be made to carry a perforated
receptacle containing carbide, which is dipped into the water of the holder
tank each time the bell falls, and is lifted out of the water when it rises
again. Thirdly (A^3), by fitting inside the upper part of the bell a false
interior, conical in shape, the descent of the bell may cause the level of the

Page 106

water in the holder tank to rise until it is above some lateral aperture
through which the liquid may escape into a carbide container placed
elsewhere. These three methods are represented in the annexed diagram
(Fig. 1). In Al the water-levels in the tank and bell remain always at l, being
higher in the tank than in the bell by a distance corresponding with the
pressure produced by the bell itself. As the bell falls a pin X moves the lever
attached to the cock on the water- pipe, and starts, or shuts off, a current
passing from a store-tank or reservoir to a decomposing vessel full of
carbide. It is also possible to make X work some releasing gear which
permits carbide to fall into water--details of this arrangement are given later
on. In A^1 the water in the tank serves as a holder seal only, a separate
quantity being employed for the purposes of the chemical reaction. This
arrangement has the advantage that the holder water lasts indefinitely,
except for evaporation in hot weather, and therefore it may be prevented
from freezing by dissolving in it some suitable saline body, or by mixing
with it some suitable liquid which lowers its point of solidification. It will
be observed, too, that in A^1 the pin X, which derives its motive power
from the surplus weight of the falling bell, has always precisely the same
amount of work to do, viz., to overcome the friction of the plug of the
water-cock in its barrel. Hence at all times the pressure obtaining in the
service-pipe is uniform, except for a slight jerk momentarily given each
time the cock is opened or closed. When X actuates a carbide-feed
arrangement, the work it does may or may not vary on different occasions,
as will appear hereafter. In A^2 the bell itself carries a perforated basket of
carbide, which is submerged in the water when the bell falls, and lifted out
again when it rises. As the carbide is thus wetted from below, the lower
portion of the mass soon becomes a layer of damp slaked lime, for although
the basket is raised completely above the water-level, much liquid adheres
to the spent carbide by capillary attraction. Hence, even when the basket is
out of the water, acetylene is being produced, and it is produced in
circumstances which prevent any control over the temperature attained. The
water clinging to the lower part of the basket is vaporised by the hot, half-
spent carbide, and the steam attacks the upper part, so that polymerisation
of the gas and baking of the carbide are inevitable. In the second place, the
pressure in the service-pipe attached to A^2 depends as before upon the net
weight of the holder bell; but here that net weight is made up of the weight
of the bell itself, that of the basket, and that of the carbide it contains. Since

Page 107

the carbide is being gradually converted into damp slaked lime, it increases
in weight to an indeterminate extent as the generator in exhausted; but
since, on the other hand, some lime may be washed out of the basket each
time it is submerged, and some of the smaller fragments of carbide may fall
through the perforations, the basket tends to decrease in weight as the
generator is exhausted. Thus it happens in A^2 that the combined weight of
bell plus basket plus contents is wholly indefinite, and the pressure in the
service becomes so irregular that a separate governor must be added to the
installation before the burners can be expected to behave properly. In the
third place, the water in the tank serves both for generation and for
decomposition, and this involves the employment of some arrangement to
keep its level fairly constant lest the bell should become unsealed, while
protection from frost by saline or liquid additions is impossible. A^2 is
known popularly as a "dipping" generator, and it will be seen to be
defective mechanically and bad chemically. In both A^1 and A^2 the bell is
constructed of thin sheet- metal, and it is cylindrical in shape; the mass of
metal in it is therefore negligible in comparison with the mass of water in
the tank, and so the level of the liquid is sensibly the same whether the bell
be high or low. In A^3 the interior of the bell is fitted with a circular plate
which cuts off its upper corners and leaves a circumferential space S
triangular in vertical section. This space is always full of air, or air and
water, and has to be deducted from the available storage capacity of the
bell. Supposing the bell transparent, and viewing it from above, its effective
clear or internal diameter will be observed to be smaller towards the top
than near the bottom; or since the space S is closed both against the water
and against the gas, the walls of the bell may be said to be thicker near its
top. Thus it happens that as the bell descends into the water past the lower
angle of S, it begins to require more space for itself in the tank, and so it
displaces the water until the levels rise. When high, as shown in the sketch
marked A^3(a), the water-level is at l, below the mouth of a pipe P; but
when low, as in A^3(b), the water is raised to the point l', which is above P.
Water therefore flows into P, whence it reaches the carbide in an attached
decomposing chamber. Here also the water in the tank is used for
decomposition as well as for sealing purposes, and its normal level must be
maintained exactly at l, lest the mouth of P should not be covered whenever
the bell falls.

Page 108

The devices employed to render a generator automatic which depend upon
pressure (B) are of three main varieties: (B^1) the water-level in the
decomposing chamber may be depressed by the pressure therein until its
surface falls below a stationary mass of carbide; (B^2) the level in a water-
store tank may be depressed until it falls below the mouth of a pipe leading
to the carbide vessel; (B^3) the current of water passing down a pipe to the
decomposing chamber may be interrupted by the action of a pressure
superior to the force of gravitation. These arrangements are indicated
roughly in Fig. 2. In B^1, D is a hollow cylinder closed at all points except
at the cock G and the hole E, which are always below the level of the water
in the annulus F, the latter being open to the air at its top. D is rigidly
fastened to the outer vessel F so that it cannot move vertically, and the
carbide cage is rigidly fastened to D. Normally the water-levels are at l, and
the liquid has access to the carbide through perforations in the basket.
Acetylene is thus produced; but if G is shut, the gas is unable to escape, and
so it presses downwards upon the water until the liquid falls in D to the
dotted line l", rising in F to the dotted line l'. The carbide is then out of
water, and except for after-generation, evolution of gas ceases. On opening
G more or less fully, the water more or less quickly reaches its original
position at l, and acetylene is again produced. Manifestly this arrangement
is identical with that of A^2 as regards the periodical immersion of the
carbide holder in the liquid; but it is even worse than the former
mechanically because there is no rising holder in B^1, and the pressure in
the service is never constant. B^2 represents the water store of an unshown
generator which works by pressure. It consists of a vessel divided vertically
by means of a partition having a submerged hole N. One-half, H, is cloned

Page 109

against the atmosphere, but communicates with the gas space of the
generator through L; the other half, K, is open to the air. M is a pipe leading
water to the carbide. When gas is being burnt as fast as, or faster than, it is
being evolved, the pressure in the generator is small, the level of the water
stands at l, and the mouth of M is below it. When the pressure rises by
cessation of consumption, that pressure acts through L upon the water in H,
driving it down in H and up in K till it takes the positions l", and l', the
mouth of M being then above the surface. It should be observed that in the
diagrams B^1 and B^3, the amount of pressure, and the consequent
alteration in level, is grossly exaggerated to gain clearness; one inch or less
in both cases may be sufficient to start or retard evolution of acetylene. Fig.
B^3 is somewhat ideal, but indicates the principle of opposing gas pressure
to a supply of water depending upon gravitation; a method often adopted in
the construction of portable acetylene apparatus. The arrangement consists
of an upper tank containing water open to the air, and a lower vessel
holding carbide closed everywhere except at the pipe P, which leads to the
burners, and at the pipe S, which introduces water from the store-tank. If
the cock at T is closed, pressure begins to rise in the carbide holder until it
is sufficient to counterbalance the weight of the column of water in the pipe
S, when a further supply is prevented until the pressure sinks again. This
idea is simply an application of the displacement-holder principle, and as
such is defective (except for vehicular lamps) by reason of lack of
uniformity in pressure.

DISPLACEMENT GASHOLDERS.--An excursion may here be made for
the purpose of studying the action of a displacement holder, which in its

Page 110

most elementary form is shown at C. It consists of an upright vessel open at
the top, and divided horizontally into two equal portions by a partition,
through which a pipe descends to the bottom of the lower half. At the top of
the closed lower compartment a tube is fixed, by means of which gas can be
introduced below the partition. While the cock is open to the air, water is
poured in at the open top till the lower compartment is completely full, and
the level of the liquid is at l. If now, gas is driven in through the side tube,
the water is forced downwards in the lower half, up through the depending
pipe till it begins to fill the upper half of the holder, and finally the upper
half is full of water and the lower half of gas an shown by the levels l' and
l". But the force necessary to introduce gas into such an apparatus, which
conversely is equal to the force with which the apparatus strives to expel its
gaseous contents, measured in inches of water, is the distance at any
moment between the levels l' and l"; and as these are always varying, the
effective pressure needed to fill the apparatus, or the effective pressure
given by the apparatus, may range from zero to a few inches less than the
total height of the whole holder. A displacement holder, accordingly, may be
used either to store a varying quantity of gas, or to give a steady pressure
just above or just below a certain desired figure; but it will not serve both
purposes. If it is employed as a holder, it in useless as a governor or
pressure regulator; if it is used as a pressure regulator, it can only hold a
certain fixed volume of gas. The rising holder, which is shown at A^1 in
Fig. 1 (neglecting the pin X, &c.) serves both purposes simultaneously;
whether nearly full or nearly empty, it gives a constant pressure--a pressure
solely dependent upon its effective weight, which may be increased by
loading its crown or decreased by supporting it on counterpoises to any
extent that may be required. As the bell of a rising holder moves, it must be
provided with suitable guides to keep its path vertical; these guides being
arranged symmetrically around its circumference and carried by the tank
walls. A fixed control rod attached to the tank over which a tube fastened to
the bell slides telescope-fashion is sometimes adopted; but such an
arrangement is in many respects less admirable than the former.

Two other devices intended to give automatic working, which are scarcely
capable of classification among their peers, may be diagrammatically
shown in Fig. 3. The first of these (D) depends upon the movements of a
flexible diaphragm. A vessel (a) of any convenient size and shape is divided

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into two portions by a thin sheet of metal, leather, caoutchouc, or the like.
At its centre the diaphragm is attached by some air-tight joint to the rod c,
which, held in position by suitable guides, is free to move longitudinally in
sympathy with the diaphragm, and is connected at its lower extremity with
a water-supply cock or a carbide-feed gear. The tube e opens at its base into
the gas space of the generator, so that the pressure below the diaphragm in a
is the same as that elsewhere in the apparatus, while the pressure in a above
the diaphragm is that of the atmosphere. Being flexible and but slightly
stretched, the diaphragm is normally depressed by the weight of c until it
occupies the position b; but if the pressure in the generator (i.e., in e) rises,
it lifts the diaphragm to somewhat about the position b'--the extent of
movement being, as usual, exaggerated in the sketch. The movement of the
diaphragm is accompanied by a movement of the rod c, which can be
employed in any desirable way. In E the bell of a rising holder of the
ordinary typo is provided with a horizontal striker which, when the bell
descends, presses against the top of a bag g made of any flexible material,
such as india-rubber, and previously filled with water. Liquid is thus
ejected, and may be caused to act upon calcium carbide in some adjacent
vessel. The sketch is given because such a method of obtaining an
intermittent water-supply has at one time been seriously proposed; but it is
clearly one which cannot be recommended.

ACTION OF WATER-TO-CARBIDE GENERATORS.--Having by one or
other of the means described obtained a supply of water intermittent in
character, it remains to be considered how that supply may be made to
approach the carbide in the generator. Actual acetylene apparatus are so
various in kind, and merge from one type to another by such small
differences, that it is somewhat difficult to classify them in a simple and
intelligible fashion. However, it may be said that water-to-carbide
generators, i.e., such as employ water as the moving material, may be
divided into four categories: (F^1) water is allowed to fall as single drops or
as a fine stream upon a mass of carbide--this being the "drip" generator;

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(F^2) a mass of water is made to rise round and then recede from a
stationary vessel containing carbide--this being essentially identical in all
respects save the mechanical one with the "dip" or "dipping" generator
shown in A^2, Fig. 1; (F^3) a supply of water is permitted to rise round, or
to flow upon, a stationary mass of carbide without ever receding from the
position it has once assumed--this being the "contact" generator; and (F^4)
a supply of water is admitted to a subdivided charge of carbide in such
proportion that each quantity admitted is in chemical excess of the carbide
it attacks. With the exception of F^2, which has already been illustrated as
A^2 Fig. 1, or as B^1 in Fig. 2, these methods of decomposing carbide are
represented in Figs. 4 and 5. It will be observed that whereas in both F^1
and F^3 the liberated acetylene passes off at the top of the apparatus, or
rather from the top of the non-subdivided charge of carbide, in F^1 the
water enters at the top, and in F^3 it enters at the bottom. Thus it happens
that the mixture of acetylene and steam, which is produced at the spot
where the primary chemical reaction is taking place, has to travel through
the entire mass of carbide present in a generator belonging to type F^3,
while in F^1 the damp gas flows directly to the exit pipe without having to
penetrate the lumps of solid. Both F^1 and F^3 exhibit after-generation
caused by a reaction between the liquid water mechanically clinging to the
mass of spent lime and the excess of carbide to an approximately equal
extent; but for the reason just mentioned, after-generation due to a reaction
between the vaporised water accompanying the acetylene first evolved and
the excess of carbide is more noticeable in F^3 than in F^1; and it is
precisely this latter description of after-generation which leads to
overheating of the most ungovernable kind. Naturally both F^1 and F^3 can
be fitted with water jackets, as is indicated by the dotted lines in the second
sketch; but unless the generating chamber in quite small and the evolution
of gas quite slow, the cooling action of the jacket will not prove sufficient.
As the water in F^1 and F^3 is not capable of backward motion, the
decomposing chambers cannot be employed as displacement holders, as is
the case in the dipping generator pictured at B^1, Fig. 2. They must be
coupled, accordingly, to a separate holder of the displacement or,
preferably, of the rising type; and, in order that the gas evolved by after-
generation may not be wasted, the automatic mechanism must cut off the
supply of water to the generator by the time that holder is two-thirds or
three-quarters full.

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The diagrams G, H, and K in Figs. 4 and 5 represent three different methods
of constructing a generator which belongs either to the contact type (F^3) if
the supply of water is essentially continuous, i.e., if less is admitted at each
movement of the feeding mechanism than is sufficient to submerge the
carbide in each receptacle; or to the flooded- compartment type (F') if the
water enters in large quantities at a time. In H the main carbide vessel is
arranged horizontally, or nearly so, and each partition dividing it into
compartments is taller than its predecessor, so that the whole of the solid in
(1) must be decomposed, and the compartment entirely filled with liquid
before it can overflow into (2), and so on. Since the carbide in all the later
receptacles is exposed to the water vapour produced in that one in which
decomposition is proceeding at any given moment, at least at its upper
surface, some after-generation between vapour and carbide occurs in H; but
a partial control over the temperature may be obtained by water-jacketing
the container. In G the water enters at the base and gas escapes at the top,
the carbide vessels being disposed vertically; hero, perhaps, more after-
generation of the same description occurs, as the moist gas streams round
and over the higher baskets. In K, the water enters at the top and must
completely fill basket (1) before it can run down the depending pipe into
(2); but since the gas also leaves the generator at the top, the later carbide
receptacles do not come in contact with water vapour, but are left
practically unattacked until their time arrives for decomposition by means
of liquid water. K, therefore, is the best arrangement of parts to avoid after-
generation, overheating, and polymerisation of the acetylene whether the

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generator be worked as a contact or as a flooded-compartment apparatus;
but it may be freely admitted that the extent of the overheating due to
reaction between water vapour and carbide may be kept almost negligible in
either K, H, or G, provided the partitions in the carbide container be
sufficient in number--provided, that is to say, that each compartment holds a
sufficiently small quantity of carbide; and provided that the quantity of
water ultimately required to fill each compartment is relatively so large that
the temperature of the liquid never approaches the boiling-point where
vaporisation is rapid. The type of generator indicated by K has not become
very popular, but G is fairly common, whilst H undoubtedly represents the
apparatus which is most generally adopted for use in domestic and other
private installations in the United Kingdom and the Continent of Europe.
The actual generators made according to the design shown by H usually
have a carbide receptacle designed in the form of a semi-cylindrical or
rectangular vessel of steel sliding fairly closely into an outside container,
the latter being either built within the main water space of the entire
apparatus or placed within a separate water-jacketed casing. Owing to its
shape and the sliding motion with which the carbide receptacle is put into
the container these generators are usually termed "drawer" generators. In
comparison with type G, the drawer generator H certainly exhibits a lower
rise in temperature when gas is evolved in it at a given speed and when the
carbide receptacles are constructed of similar dimensions. It is very
desirable that the whole receptacle should be subdivided into a sufficient
number of compartments and that it should be effectively water-cooled
from outside. It would also be advantageous if the water- supply were so
arranged that the generator should be a true flooded- compartment
apparatus, but experience has nevertheless shown that generators of type H
do work very well when the water admitted to the carbide receptacle, each
time the feed comes into action, is not enough to flood the carbide in one of
the compartments. Above a certain size drawer generators are usually
constructed with two or even more complete decomposing vessels,
arrangements being such that one drawer can be taken out for cleaning,
whilst the other is in operation. When this is the case a third carbide
receptacle should always be employed so that it may be dry, lit to receive a
charge of carbide, and ready to insert in the apparatus when one of the
others is withdrawn. The water-feed should always be so disposed that the
attendant can see at a glance which of the two (or more) carbide receptacles

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is in action at any moment, and it should be also so designed that the supply
is automatically diverted to the second receptacle when the first is wholly
exhausted and back again to the first (unless there are more than two) when
the carbide in the second is entirely gasified. In the sketches G, H, and K,
the total space occupied by the various carbide receptacles is represented as
being considerably smaller than the capacity of the decomposing chamber.
Were this method of construction copied in actual acetylene apparatus, the
first makes of gas would be seriously (perhaps dangerously) contaminated
with air. In practice the receptacles should fit so tightly into the outer vessel
and into one another that when loaded to the utmost extent permissible--
space being left for the swelling of the charge and for the passage of water
and gas--but little room should be left for the retention of air in the
chamber.

ACTION OF CARBIDE-TO-WATER GENERATORS.--The methods
which may be adopted to render a generator automatic when carbide is
employed as the moving material are shown at M, N, and P, in Fig. 6; but
the precise devices used in many actual apparatus are so various that it is
difficult to portray them generically. Moreover it is desirable to subdivide
automatic carbide-to-water generators, according to the size of the carbide
they are constructed to take, into two or three classes, which are termed
respectively "large carbide-feed," "small carbide-feed," and "granulated
carbide-feed" apparatus. (The generator represented at L does not really
belong to the present class, being non-automatic and fed by hand; but the
sketch is given for completeness.) M is an automatic carbide-feed generator
having its store of carbide in a hopper carried by the rising- holder bell. The
hopper is narrowed at its mouth, where it is closed by a conical or
mushroom valve d supported on a rod held in suitable guides. When the bell
falls by consumption of gas, it carries the valve and rod with it; but
eventually the button at the base of c strikes the bottom of the generator, or
some fixed distributing plate, and the rod can descend no further. Then,
when the bell falls lower, the mushroom d rises from its seat, and carbide
drops from the hopper into the water. This type of apparatus has the defect
characteristic of A^2, Fig. 1; for the pressure in the service steadily
diminishes as the effective weight of bell plus hopper decreases by
consumption of carbide. But it has also two other defects--(1) that ordinary
carbide is too irregular in shape to fall smoothly through the narrow annular

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space between the valve and its seat; (2) that water vapour penetrates into
the hopper, and liberates some gas there, while it attacks the lumps of
carbide at the orifice, producing dust or causing them to stick together, and
thus rendering the action of the feed worse than ever. Most of these defects
can be avoided by using granulated carbide, which is more uniform in size
and shape, or by employing a granulated and "treated" carbide which has
been dipped in some non-aqueous liquid to make it less susceptible to the
action of moisture. Both these plans, however, are expensive to adopt; first,
because of the actual cost of granulating or "treating" the carbide; secondly,
because the carbide deteriorates in gas-making capacity by its inevitable
exposure to air during the granulating or "treating" process. The defects of
irregularity of pressure and possible waste of gas by evolution in the hopper
may be overcome by disposing the parts somewhat differently; making the
holder an annulus round the hopper, or making it cylindrical with the
hopper inside. In this case the hopper is supported by the main portion of
the apparatus, and does not move with the bell: the rod and valve being
given their motion in some fashion similar to that figured. Apparatus
designed in accordance with the sketch M, or with the modification just
described, are usually referred to under the name of "hopper" generators.
On several occasions trouble has arisen during their employment owing to
the jamming of the valve, a fragment of carbide rather larger than the rest of
the material lodging between the lips of the hopper and the edges of the
mushroom valve. This has been followed by a sudden descent of all the
carbide in the store into the water beneath, and the evolution of gas has
sometimes been too rapid to pass away at the necessary speed into the
holder. The trouble is rendered even more serious should the whole charge
of carbide fall at a time when, by neglect or otherwise, the body of the
generator contains much lime sludge, the decomposition then proceeding
under exceptionally bad circumstances, which lead to the production of an
excessively high temperature. Hopper generators are undoubtedly very
convenient for certain purposes, chiefly, perhaps, for the construction of
table-lamps and other small installations. Experience tends to show that
they may be employed, first, provided they are designed to take granulated
carbide--which in comparison with larger grades is much more uniform and
cylindrical in shape--and secondly, provided the quantity of carbide in the
hopper does not exceed a few pounds. The phenomenon of the sudden
unexpected descent of the carbide, popularly known as "dumping," can

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hardly be avoided with carbide larger in size than the granulated variety;
and since the results of such an accident must increase in severity with the
size of the apparatus, a limit in their capacity is desirable.

When it is required to construct a carbide-feed generator of large size or one
belonging to the large carbide-feed pattern, it is preferable to arrange the
store in a different manner. In N the carbide is held in a considerable
number of small receptacles, two only of which are shown in the drawing,
provided with detachable lids and hinged bottoms kept shut by suitable
catches. At proper intervals of time those catches in succession are knocked
on one side by a pin, and the contents of the vessel fall into the water. There
are several methods available for operating the pins. The rising-holder bell
may be made to actuate a train of wheels which terminate in a disc
revolving horizontally on a vertical axis somewhere just below the catches;
and this wheel may bear an eccentric pin which hits each catch as it rotates.
Alternatively the carbide boxes may be made to revolve horizontally on a
vertical axis by the movements of the bell communicated through a clutch;
and thus each box in succession may arrive at a certain position where the
catch is knocked aside by a fixed pin. The boxes, again, may revolve
vertically on a horizontal axis somewhat like a water-wheel, each box
having its bottom opened, or, by a different system of construction, being
bodily upset, when it arrives at the bottom of its circular path. In no case,
however, are the carbide receptacles carried by the bell, which is a totally
distinct part of the apparatus; and therefore in comparison with M, the
pressure given by the bell is much more uniform. Nevertheless, if the
system of carbide boxes moves at all, it becomes easier to move by
decrease in weight and consequent diminution in friction as the total charge

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is exhausted; and accordingly the bell has less work to do during the later
stages of its operation. For this reason the plan actually shown at N is
preferable, since the work done by the moving pin, i.e., by the descending
bell, is always the same. P represents a carbide-feed effected by a spiral
screw or conveyor, which, revolved periodically by a moving bell, draws
carbide out of a hopper of any desired size and finally drops it into a shoot
communicating with a generating chamber such as that shown in L. Here
the work done by the bell is large, as the friction against the blades of the
screw and the walls of the horizontal tube is heavy; but that amount of work
must always be essentially identical. The carbide-feed may similarly be
effected by means of some other type of conveyor instead of the spiral
screw, such as an endless band, and the friction in these cases may be
somewhat less than with the screw, but the work to be done by the bell will
always remain large, whatever type of conveyor may be adopted. A further
plan for securing a carbide-feed consists in employing some extraneous
driving power to propel a charge of carbide out of a reservoir into the
generator. Sometimes the propulsive effort is obtained from a train of
clockwork, sometimes from a separate supply of water under high pressure.
The clockwork or the water power is used either to drive a piston travelling
through the vessel containing the carbide so that the proper quantity of
material is dropped over the open mouth of a shoot, or to upset one after
another a series of carbide receptacles, or to perform some analogous
operation. In these cases the pin or other device fitted to the acetylene
apparatus itself has nothing to do beyond releasing the mechanism in
question, and therefore the work required from the bell is but small. The
propriety of employing a generator belonging to these latter types must
depend upon local conditions, e.g., whether the owner of the installation has
hydraulic power on a small scale (a constant supply of water under
sufficient pressure) at disposal, or whether he does not object to the extra
labour involved in the periodical winding up of a train of clockwork.

It must be clear that all these carbide-feed arrangements have the defect in a
more or less serious degree of leaving the carbide in the main storage vessel
exposed to the attack of water vapour rising from the decomposing
chamber, for none of the valves or operating mechanism can be made quite
air-tight. Evolution of gas produced in this way does not matter in the least,
because it is easy to return the gas so liberated into the generator or into the

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holder; while the extent of the action, and the consequent production of
overheating, will tend to be less than in generators such as those shown in G
and H of Figs. 4 and 5, inasmuch as the large excess of water in the carbide-
feed apparatus prevents the liquid arriving at a temperature at which it
volatilises rapidly. The main objection to the evolution of gas in the carbide
vessel of a carbide-to-water generator depends on the danger that the
smooth working of the feed-gear may be interfered with by the formation of
dust or by the aggregation of the carbide lumps.

USE OF OIL IN GENERATORS.--Calcium carbide is a material which is
only capable of attack for the purpose of evolving acetylene by a liquid that
is essentially water, or by one that contains some water mixed with it. Oils
and the like, or even such non-aqueous liquids as absolute alcohol, have no
effect upon carbide, except that the former naturally make it greasy and
somewhat more difficult to moisten. This last property has been found of
service in acetylene generation, especially on the small scale; for if carbide
is soaked in, or given a coating of, some oil, fat, or solid hydrocarbon like
petroleum, cocoanut oil, or paraffin wax, the substance becomes
comparatively indifferent towards water vapour or the moisture present in
the air, while it still remains capable of complete, albeit slow,
decomposition by liquid water when completely immersed therein. The fact
that ordinary calcium carbide is attacked so quickly by water is really a
defect of the substance; for it is to this extreme rapidity of reaction that the
troubles of overheating are due. Now, if the basket in the generator B^1 of
Fig. 2, or, indeed, the carbide store in any of the carbide-to-water apparatus,
is filled with a carbide which has been treated with oil or wax, as long as
the water-level stands at l' and l" or the carbide still remains in the hopper, it
is essentially unattacked by the vapour arising from the liquid; but directly
the basket is submerged, or the lumps fall into the water, acetylene is
produced, and produced more slowly and regularly than otherwise. Again,
oils do not mix with water, but usually float thereon, and a mass of water
covered by a thick film or layer of oil does not evaporate appreciably. If,
now, a certain quantity of oil, say lamp paraffin or mineral lubricating oil, is
poured on to the water in B^1, Fig. 2, it moves upwards and downwards
with the water. When the water takes the position l, the oil is driven
upwards away from the basket of carbide, and acetylene is generated in the
ordinary manner; but when the water falls to l" the oil descends also, rinses

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off much of the adhering water from the carbide lumps, covers them with a
greasy film, and almost entirely stops generation till it is in turn washed off
by the next ascent of the water. Similarly, if the carbide in generators F, G,
and H (also K) has been treated with a solid or semi-solid grease, it is
practically unattacked by the stream of warm damp gas, and is only
decomposed when the liquid itself arrives in the basket. For the same reason
treated carbide can be kept for fairly long periods of time, even in a drum
with badly fitting lid, without suffering much deterioration by the action of
atmospheric moisture. The problem of acetylene generation is accordingly
simplified to a considerable degree by the use of such treated carbide, and
the advantage becomes more marked as the plant decreases in size till a
portable apparatus is reached, because the smaller the installation the more
relatively expensive or inconvenient is a large holder for surplus gas. The
one defect of the method is the extra cost of such treated carbide; and in
English conditions ordinary calcium carbide is too expensive to permit of
any additional outlay upon the acetylene if it is to compete with petroleum
or the product of a tiny coal-gas works. The extra cost of using treated
carbide falls upon the revenue account, and is much more noticeable than
that of a large holder, which is capital expenditure. When fluid oil is
employed in a generator of type B^1, evolution of gas becomes so regular
that any holder beyond the displacement one which the apparatus itself
constitutes is actually unnecessary, though still desirable; but B^1, with or
without oil, still remains a displacement apparatus, and as such gives no
constant pressure. It must be admitted that the presence of oil so far governs
the evolution of gas that the movement of the water, and the consequent
variation of pressure, is rendered very small; still a governor or a rising
holder would be required to give the best result at the burners. One point in
connexion with the use of liquid oil must not be overlooked, viz., the extra
trouble it may give in the disposal of the residues. This matter will be dealt
with more fully in Chapter V.; here it is sufficient to say that as the oil does
not mix with the water but floats on the surface, care has to be taken that it
is not permitted to enter any open stream. The foregoing remarks about the
use of oil manifestly only apply to those cases where it is used in quantity
and where it ultimately becomes mixed with the sludge or floats on the
water in the decomposing chamber. The employment of a limpid oil, such
as paraffin, as an intermediate liquid into which carbide is introduced on its
way to the water in the decomposing vessel of a hand-fed generator in the

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manner described on page 70 is something quite different, because, except
for trifling losses, one charge of oil should last indefinitely.

RISING GASHOLDERS.--Whichever description of holder is employed in
an acetylene apparatus, the gas is always stored over, or in contact with, a
liquid that is essentially water. This introduces three subjects for
consideration: the heavy weight of a large body of liquid, the loss of gas by
dissolution in that liquid, and the protection of that liquid from frost in the
winter. The tanks of rising holders are constructed in two different ways. In
one the tank is a plain cylindrical vessel somewhat larger in diameter than
the bell which floats in it; and since there must be nearly enough water in
the tank to fill the interior of the bell when the latter assumes its lowest
position, the quantity of water is considerable, its capacity for dissolving
acetylene is large, and the amount of any substance that may have to be
added to it to lower its freezing-point becomes so great as to be scarcely
economical. All these defects, including that of the necessity for very
substantial foundations under the holder to support its enormous weight,
may be overcome by adopting the second method of construction. It is clear
that the water in the centre of the tank is of no use,--all that is needed being
a narrow trough for the bell to work in. Large rising holders are therefore
advantageously built with a tank formed in the shape of an annulus, the
effective breadth of which is not more than 2 or 3 inches, the centre portion
being roofed over so as to prevent escape of gas. The same principle may be
retained with modified details by fitting inside a plain cylindrical tank a
"dummy" or smaller cylinder, closed by a flat or curved top and fastened
water- and air-tight to the bottom of the main vessel. The construction of
annular tanks or the insertion of a "dummy" may be attended with difficulty
if the tank is wholly or partly sunk below the ground level, owing to the
lifting force of water in the surrounding soil. Where a steel tank is sunk, or
a masonry tank is constructed, regard must be paid, both in the design of the
tank and in the manner of construction, to the level of the underground
water in the neighbourhood, as in certain cases special precautions will be
needed to avoid trouble from the pressure of the water on the outside of the
tank until it is balanced by the pressure of the water with which the tank is
filled. So far as mere dissolution of gas is concerned, the loss may be
reduced by having a circular disc of wood, &c., a little smaller in diameter
than the boll, floating on the water of a plain tank.

Page 122

EFFECT OF STORAGE IN GASHOLDER ON ACETYLENE.--It is
perfectly true, as has been stated elsewhere, that the gas coming from an
acetylene generator loses some of its illuminating power if it is stored over
water for any great length of time; such loss being given by Nichols as 94
per cent, in five months, and having been found by one of the authors as
0.63 per cent. per day--figures which stand in fair agreement with one
another. This wastage is not due to any decomposition of the acetylene in
contact with water, but depends on the various solubilities of the different
gases which compose the product obtained from commercial calcium
carbide. Inasmuch as an acetylene evolved in the best generator contains
some foreign ingredients, and inasmuch as an inferior product contains
more (cf. Chapter V.), the contents of a holder are never pure; but as those
contents are principally made up of acetylene itself, that gas stands at a
higher partial pressure in the holder than the impurities. Since acetylene is
more soluble in water than any of its diluents or impurities, sulphuretted
hydrogen and ammonia excepted, and since the solubility of all gases
increases as the pressure at which they are stored rises, the true acetylene in
an acetylene holder dissolves in the water more rapidly and comparatively
more copiously than the impurities; and thus the acetylene tends to
disappear and the impurities to become concentrated within the bell.
Simultaneously at the outer part of the seal, air is dissolved in the water;
and by processes of diffusion the air so dissolved passes through the liquid
from the outside to the inside, where it escapes into the bell, while the
dissolved acetylene similarly passes from the inside to the outside of the
seal, and there mingles with the atmosphere. Thus, the longer a certain
volume of acetylene is stored over water, the more does it become
contaminated with the constituents of the atmosphere and with the
impurities originally present in it; while as the acetylene is much more
soluble than its impurities, more gas escapes from, than enters, the holder
by diffusion, and so the bulk of stored gas gradually diminishes. However,
the figures previously given show that this action is too slow to be
noticeable in practice, for the gas is never stored for more than a few days
at a time. The action cannot be accepted as a valid argument against the
employment of a holder in acetylene plant. Such deterioration and wastage
of gas may be reduced to some extent by the use of a film of some cheap
and indifferent oil floating on the water inside an acetylene holder; the
economy being caused by the lower solubility of acetylene in oils than in

Page 123

aqueous liquids not saturated with some saline material. Probably almost
any oil would answer equally well, provided it was not volatile at the
temperature of the holder, and that it did not dry or gum on standing, e.g.,
olive oil or its substitutes; but mineral lubricating oil is not so satisfactory.
It is, however, not necessary to adopt this method in practice, because the
solvent power of the liquid in the seal can be reduced by adding to it a
saline body which simultaneously lowers its freezing-point and makes the
apparatus more trustworthy in winter.

FREEZING OF GASHOLDER SEAL.--The danger attendant upon the
congelation of the seal in an acetylene holder is very real, not so much
because of the fear that the apparatus may be burst, which is hardly to be
expected, as because the bell will be firmly fixed in a certain position by the
ice, and the whole establishment lighted by the gas will be left in darkness.
In these circumstances, hurried and perhaps injudicious attempts may be
made to thaw the seal by putting red-hot bars into it or by lighting fires
under it, or the generator-house may be thoughtlessly entered with a naked
light at a time when the apparatus is possibly in disorder through the loss of
storage-room for the gas it is evolving. Should a seal ever freeze, it must be
thawed only by the application of boiling water; and the plant-house must
be entered, if daylight has passed, in perfect darkness or with the assistance
of an outside lamp whining through a closed window. [Footnote: By "closed
window" is to be understood one incapable of being opened, fitted with one
or two thicknesses of stout glass well puttied in, and placed in a wall of the
house as far as possible from the door.] There are two ways of preventing
the seal from freezing. In all large installations the generator-house will be
fitted with a warm-water heating apparatus to protect the portion of the
plant where the carbide is decomposed, and if the holder is also inside the
same building it will naturally be safe. If it is outside, one of the flow-pipes
from the warming apparatus should be led into and round the lowest part of
the seal, care being taken to watch for, or to provide automatic
arrangements for making good, loss of water by evaporation. If the holder is
at a distance from the generator-house, or if for any other reason it cannot
easily be brought into the warming circuit, the seal can be protected in
another way; for unlike the water in the generator, the water in the holder-
seal will perform its functions equally well however much it be reduced in
temperature, always providing it is maintained in the liquid condition. There

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are numerous substances which dissolve in, or mix with, water, and yield
solutions or liquids that do not solidify until their temperature falls far
below that of the natural freezing- point. Assuming that those substances in
solution do not attack the acetylene, nor the metal of which the holder is
built, and are not too expensive, choice may be made between them at will.
Strictly speaking the cost of using them is small, because unless the tank is
leaky they last indefinitely, not evaporating with the water as it is vaporised
into the gas or into the air. The water-seal of a holder standing within the
generator-house may eventually become so offensive to the nostrils that the
liquid has to be renewed; but when this happens it is due to the
accumulation in the water of the water-soluble impurities of the crude
acetylene. If, as should be done, the gas is passed through a washer or
condenser containing much water before it enters the holder the
sulphuretted hydrogen and ammonia will be extracted, and the seal will not
acquire an obnoxious odour for a very long time.

Four principal substances have been proposed for lowering the freezing-
point of the water in an acetylene-holder seal; common salt (sodium
chloride), calcium chloride (not chloride of lime), alcohol (methylated
spirit), and glycerin. A 10 per cent. solution of common salt has a specific
gravity of 1.0734, and does not solidify above -6° C. or 21.2° F.; a 15 per
cent. solution has a density of 1.111, and freezes at -10° C. or 14° F.
Common salt, however, is not to be recommended, as its solutions always
corrode iron and steel vessels more or less quickly. Alcohol, in its English
denatured form of methylated spirit, is still somewhat expensive to use, but
it has the advantage of not increasing the viscosity of the water; so that a
frost-proof mixture of alcohol and water will flow as readily through minute
tubes choked with needle- valves, or through felt and the like, or along
wicks, as will plain water. For this reason, and for the practically identical
one that it is quite free from dirt or insoluble matter, diluted spirit is
specially suitable for the protection of the water in cyclists' acetylene lamps,
[Footnote: As will appear in Chapter XIII., there is usually no holder in a
vehicular acetylene lamp, all the water being employed eventually for the
purpose of decomposing the carbide. This does not affect the present
question. Dilute alcohol does not attack calcium carbide so energetically as
pure water, because it stands midway between pure water and pure alcohol,
which is inert. The attack, however, of the carbide is as complete as that of

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pure water, and the slower speed thereof is a manifest advantage in any
holderless apparatus.] where strict economy is less important than smooth
working. For domestic and larger installations it is not indicated. As
between calcium chloride and glycerin there is little to choose; the former
will be somewhat cheaper, but the latter will not be prohibitively expensive
if the high-grade pure glycerins of the pharmacist are avoided. The
following tables show the amount of each substance which must be
dissolved in water to obtain a liquid of definite solidifying point. The data
relating to alcohol were obtained by Pictet, and those for calcium chloride
by Pickering. The latter are materially different from figures given by other
investigators, and perhaps it would be safer to make due allowance for this
difference. In Germany the Acetylene Association advocates a 17 per cent.
solution of calcium chloride, to which Frank ascribes a specific gravity of
1.134, and a freezing-point of -8° C. or 17.6° F.

Freezing-Points of Dilute Alcohol.
_________________________________________________________
| | | |
| Percentage of | Specific Gravity. | Freezing-point. |
| Alcohol. | | |
|_______________|___________________|_____________________|
| | | | |
| | | Degs. C. | Degs. F. |
| 4.8 | 0.9916 | -2.0 | +28.4 |
| 11.3 | 0.9824 | 5.0 | 23.0 |
| 16.4 | 0.9761 | 7.5 | 18.5 |
| 18.8 | 0.9732 | 9.4 | 15.1 |
| 20.3 | 0.9712 | 10.6 | 12.9 |
| 22.1 | 0.9689 | 12.2 | 10.0 |
| 24.2 | 0.9662 | 14.0 | 6.8 |
| 26.7 | 0.9627 | 16.0 | 3.2 |
| 29.9 | 0.9578 | 18.9 | -2.0 |
|_______________|___________________|__________|__________|

Freezing-Points of Dilute Glycerin.
_________________________________________________________
| | | |
| Percentage of | Specific Gravity. | Freezing-point. |
| Glycerin. | | |
|_______________|___________________|_____________________|
| | | | |
| | | Degs. C. | Degs. F. |

Page 126

| 10 | 1.024 | -1.0 | +30.2 |
| 20 | 1.051 | 2.5 | 27.5 |
| 30 | 1.075 | 6.0 | 21.2 |
| 40 | 1.105 | 17.5 | 0.5 |
| 50 | 1.127 | 31.3 | -24.3 |
|_______________|___________________|__________|__________|

Freezing-Points of Calcium Chloride Solutions.
_________________________________________________________
| | | |
| Percentage of | Specific Gravity. | Freezing-point. |
| CaCl_2. | | |
|_______________|___________________|_____________________|
| | | | |
| | | Degs. C. | Degs. F. |
| 6 | 1.05 | -3.0 | +26.6 |
| 8 | 1.067 | 4.3 | 24.3 |
| 10 | 1.985 | 5.9 | 21.4 |
| 12 | 1.103 | 7.7 | 18.1 |
| 14 | 1.121 | 9.8 | 14.4 |
| 16 | 1.140 | 12.2 | 10.0 |
| 18 | 1.159 | 15.2 | 4.6 |
| 20 | 1.170 | 18.6 | -1.5 |
|_______________|___________________|__________|__________|

Calcium chloride will probably be procured in the solid state, but it can be
purchased as a concentrated solution, being sold under the name of
"calcidum" [Footnote: This proprietary German article is a liquid which
begins to solidify at -42° C. (-43.6° F.), and is completely solid at -56° C.
(-69)° F.). Diluted with one-third its volume of water, it freezes between
-20° and -28° C. (-4° and-l8.4° F.). The makers recommend that it should be
mixed with an equal volume of water. Another material known as
"Gefrierschutzflüssigkeit" and made by the Flörsheim chemical works,
freezes at -35° C. (-3° F.). Diluted with one-quarter its volume of water, it
solidifies at -18° C. (-0.4° F.); with equal parts of water it freezes at -12° C.
(10.4° F.). A third product, called "calcidum oxychlorid," has been found by
Caro and Saulmann to be an impure 35 per cent. solution of calcium
chloride. Not one of these is suitable for addition to the water used in the
generating chamber of an acetylene apparatus, the reasons for this having
already been mentioned.] for the protection of gasholder seals. Glycerin
itself resembles a strong solution of calcium chloride in being a viscid, oily-
looking liquid; and both are so much heavier than water that they will not

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mix with further quantities unless they are thoroughly agitated therewith.
Either may be poured through water, or have water floated upon it, without
any appreciable admixture taking place; and therefore in first adding them
to the seal great care must be taken that they are uniformly distributed
throughout the liquid. If the whole contents of the seal cannot conveniently
be run into an open vessel in which the mixing can be performed, the
sealing water must be drawn off a little at a time and a corresponding
quantity of the protective reagent added to it. Care must be taken also that
motives of economy do not lead to excessive dilution of the reagent; the
seal must be competent to remain liquid under the prolonged influence of
the most severe frost ever known to occur in the neighbourhood where the
plant is situated. If the holder is placed out of doors in an exposed spot
where heavy rains may fall on the top of the bell, or where snow may
collect there and melt, the water is apt to run down into the seal, diluting the
upper layers until they lose the frost- resisting power they originally had.
This danger may be prevented by erecting a sloping roof over the bell
crown, or by stirring up the seal and adding more preservative whenever it
has been diluted with rain water. Quite small holders would probably
always be placed inside the generator-house, where their seals may be
protected by the same means as are applied to the generator itself. It need
hardly be said that all remarks about the dangers incidental to the freezing
of holder seals and the methods for obviating them refer equally to every
item in the acetylene plant which contains water or is fitted with a water-
sealed cover; only the water which is actually used for decomposing the
calcium carbide cannot be protected from frost by the addition of calcium
chloride or glycerin--that water must be kept from falling to its natural
freezing-point. From Mauricheau-Beaupré's experiments, referred to on
page 106, it would appear that a further reason for avoiding an addition of
calcium chloride to the water used for decomposing carbide should lie in
the danger of causing a troublesome production of froth within the
generator.

It will be convenient to digress here for the purpose of considering how the
generators of an acetylene apparatus themselves should be protected from
frost; but it may be said at the outset that it is impossible to lay down any
fixed rules applicable to all cases, since local conditions, such as climate,
available resources, dimensions, and exposed or protected position of the

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plant-house vary so largely in different situations. In all important
installations every item of the plant, except the holder, will be collected in
one or two rooms of a single building constructed of brick or other
incombustible material. Assuming that long-continued frost reigns at times
in the neighbourhood, the whole of such a building, with the exception of
one apartment used as a carbide store only, is judiciously fitted with a
heating arrangement like those employed in conservatories or hothouses; a
system of pipes in which warm water is kept circulating being run round the
walls of each chamber near the floor. The boiler, heated with coke, paraffin,
or even acetylene, must naturally be placed in a separate room of the
apparatus-house having no direct (indoor) communication with the rooms
containing the generators, purifiers, &c. Instead of coils of pipe, "radiators"
of the usual commercial patterns may be adopted; but the immediate source
of heat should be steam, or preferably hot water, and not hot air or
combustion products from the stove. In exposed situations, where the
holder is out of doors, one branch of the flow-pipe should enter and travel
round the seal as previously suggested. Most large country residences are
already provided with suitable heating apparatus for warming the
greenhouses, and part of the heat may be capable of diversion into the
acetylene generator-shed if the latter is erected in a convenient spot. In fact,
if any existing hot-water warming appliances are already at hand, and if
they are powerful enough to do a little more work, it may be well to put the
generator-building in such a position that it can be efficiently supplied with
artificial warmth from those boilers; for any extra length of main necessary
to lead the gas into the residence from a distant generator will cost less on
the revenue account than the fuel required to feed a special heating
arrangement. In smaller installations, especially such as are to be found in
mild climates, it may be possible to render the apparatus-house sufficiently
frost-proof without artificial heat by building it partly underground, fitting it
with a double skylight in place of a window for the entrance of daylight,
and banking up its walls all round with thick layers of earth. The house
must have a door, however, which must open outwards and easily, so that
no obstacle may prevent a hurried exit in emergencies. Such a door can
hardly be made very thick or double without rendering it heavy and difficult
to open; and the single door will be scarcely capable of protecting the
interior if the frost is severe and prolonged. Ventilators, too, must be
provided to allow of the escape of any gas that may accidentally issue from

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the plant during recharging, &c.; and some aperture in the roof will be
required for the passage of the vent pipe or pipes, which, in certain types of
apparatus, move upwards and downwards with the bell of the holder. These
openings manifestly afford facilities for the entry of cold air, so that
although this method of protecting generator-houses has proved efficient in
many places, it can only be considered inferior to the plan of installing a
proper heating arrangement. Occasionally, where local regulations do not
forbid, the entire generator-house may be built as a "lean-to" against some
brick wall which happens to be kept constantly warm, say by having a
furnace or a large kitchen stove on its other side.

In less complicated installations, where there are only two distinct items in
the plant to be protected from frost--generator and holder--or where
generator and holder are combined into one piece of apparatus, other
methods of warming become possible. As the reaction between calcium
carbide and water evolves much heat, the most obvious way of preventing
the plant from freezing is to economise that heat, i.e., to retain as much of it
as is necessary within the apparatus. Such a process, clearly, is only
available if the plant is suitable in external form, is practically self-
contained, and comprises no isolated vessels containing an aqueous liquid.
It is indicated, therefore, rather for carbide-to- water generators, or for
water-to-carbide apparatus in which the carbide chambers are situated
inside the main water reservoir--any apparatus, in fact, where much water is
present and where it is all together in one receptacle. Moreover, the method
of heat economy is suited for application to automatic generators rather than
to those belonging to the opposite system, because automatic apparatus will
be generating gas, and consequently evolving heat, every evening till late at
night--just at the time when frost begins to be severe. A non-automatic
generator will usually be at work only in the mornings, and its store of heat
will accordingly be much more difficult to retain till nightfall. With the
object of storing up the heat evolved in the generator, it must be covered
with some material possessed of the lowest heat-conducting power possible;
and the proper positions for that material in order of decreasing importance
are the top, sides, and bottom of the plant. The generator may either be
covered with a thick layer of straw, carpet, flannel, or the like, as is done in
the protection of exposed water- pipes; or it may be provided with a jacket
filled with some liquid. In view of the advisability of not having any

Page 130

organic or combustible material near the generator, the solid substances just
mentioned may preferably be replaced by one of those partially inorganic
compositions sold for "lagging" steam-pipes and engine-cylinders, such as
"Fossil meal." Indeed, the exact nature of the lagging matters comparatively
little, because the active substance in retaining the heat in the acetylene
generator or the steam-pipe is the air entangled in the pores of the lagging;
and therefore the value of any particular material depends mainly on its
exhibiting a high degree of porosity. The idea of fitting a water jacket round
an acetylene generator is not altogether good, but it may be greatly
improved upon by putting into the jacket a strong solution of some cheap
saline body which has the property of separating from its aqueous solution
in the form of crystals containing water of crystallisation, and of evolving
much heat in so separating. This method of storing much heat in a small
space where a fire cannot be lighted is in common use on some railways,
where passengers' foot-warmers are filled with a strong solution of sodium
acetate. When sodium acetate is dissolved in water it manifestly exists in
the liquid state, and it is presumably present in its anhydrous condition (i.e.,
not combined with water of crystallisation). The common crystals are solid,
and contain 3 molecules of water of crystallisation--also clearly in the solid
state. Now, the reaction

NaC_2H_3O_2 + 3H_2O = NaC_2H_3O_2.3H_2O

(anhydrous acetate) (crystals)

evolves 4.37 calories (Berthelot), or 1.46 calorie for each molecule of
water; and whereas 1 kilo. of water only evolves 1 large calorie of heat as
its temperature falls 1° C., 18 grammes of water (1 gramme-molecule)
evolve l.46 large calorie when they enter into combination with anhydrous
sodium acetate to assist in forming crystals--and this 1.46 calorie may either
be permitted to warm the mass of crystals, or made to do useful work by
raising the temperature of some adjacent substance. Sodium acetate crystals
dissolve in 3.9 parts by weight of water at 6° C. (43° F.) or in 2.4 parts at
37° C. (99° F.). If, then, a jacket round an acetylene apparatus is filled with
a warm solution of sodium acetate crystals in (say) 3 parts by weight of
water, the liquid will crystallise when it reaches some temperature between
99° and 43° F.; but when the generator comes into action, the heat liberated

Page 131

will change the mass of crystals into a liquid without raising its sensible
temperature to anything like the extent that would happen were the jacket
full of simple water. Not being particularly warm to the touch, the liquefied
product in the jacket will not lose much heat by radiation, &c., into the
surrounding air; but when the water in the generator falls again (after
evolution of acetylene ceases) the contents of the jacket will also cool, and
finally will begin to crystallise once more, passing a large amount of low-
temperature heat into the water of the generator, and safely maintaining it
for long periods of time at a temperature suitable for the further evolution of
gas. Like the liquid in the seal of an isolated gasholder, the liquid in such a
jacket will last indefinitely; and therefore the cost of the sodium acetate in
negligible.

Another method of keeping warm the water in any part of an acetylene
installation consists in piling round the apparatus a heap of fresh stable
manure, which, as is well known, emits much heat as it rots. Where horses
are kept, such a process may be said to cost nothing. It has the advantage
over methods of lagging or jacketing that the manure can be thrown over
any pipe, water-seal, washing apparatus, &c., even if the plant is
constructed in several separate items. Unfortunately the ammonia and the
volatile organic compounds which are produced during the natural
decomposition of stable manure tend seriously to corrode iron and steel,
and therefore this method of protecting an apparatus from frost should only
be employed temporarily in times of emergency.

CORROSION IN APPARATUS.--All natural water is a solution of oxygen
and may be regarded also as a weak solution of the hypothetical carbonic
acid. It therefore causes iron to rust more or less quickly; and since no paint
is absolutely waterproof, especially if it has been applied to a surface
already coated locally with spots of rust, iron and steel cannot be perfectly
protected by its aid. More particularly at a few inches above and below the
normal level of the water in a holder, therefore, the metal soon begins to
exhibit symptoms of corrosion which may eventually proceed until the iron
is eaten away or becomes porous. One method of prolonging the life of
such apparatus is to give it fresh coats of paint periodically; but unless the
old layers are removed where they have cracked or blistered, and the rust
underneath is entirely scraped off (which is practically impossible), the new

Page 132

paint films will not last very long. Another more elegant process for
preserving any metal like iron which is constantly exposed to the attack of a
corrosive liquid, and which is readily applicable to acetylene holders and
their tanks, depends on the principle of galvanic action. When two metals in
good electrical contact are immersed in some liquid that is capable of
attacking both, only that metal will be attacked which is the more electro-
positive, or which (the same thing in other words) is the more readily
attacked by the liquid, evolving the more heat during its dissolution. As
long as this action is proceeding, as long, that is, as some of the more
electro- positive material is present, the less electro-positive material will
not suffer. All that has to be done, therefore, to protect the walls of an
acetylene-holder tank and the sides of its bell is to hang in the seal,
supported by a copper wire fastened to the tank walls by a trustworthy
electrical joint (soldering or riveting it), a plate or rod of some more electro-
positive metal, renewing that plate or rod before it is entirely eaten away.
[Footnote: Contact between the bell and the rod may be established by
means of a flexible metallic wire; or a separate rod might be used for the
bell itself.] If the iron is bare or coated with lead (paint may be overlooked),
the plate may be zinc; if the iron is galvanised, i.e., coated with zinc, the
plate may be aluminium or an alloy of aluminium and zinc. The joint
between the copper wire and the zinc or aluminium plate should naturally
be above the water-level. The foregoing remarks should be read in
conjunction with what was said in Chapter II., about the undesirability of
employing a soft solder containing lead in the construction of an acetylene
generator. Here it is proposed intentionally to set up a galvanic couple to
prevent corrosion; there, with the same object in view, the avoidances of
galvanic action is counselled. The reason for this difference is self-evident;
here a foreign metal is brought into electrical contact with the apparatus in
order that the latter may be made electro-negative; but when a joint is
soldered with lead, the metal of the generator is unintentionally made
electro-positive. Here the plant is protected by the preferential corrosion of
a cheap and renewable rod; in the former case the plant is encouraged to
rust by the unnecessary presence of an improperly selected metal.

OTHER ITEMS IN GENERATING PLANT.--It has been explained in
Chapter II. that the reaction between calcium carbide and water is very
tumultuous in character, and that it occurs with great rapidity. Clearly,

Page 133

therefore, the gas comes away from the generator in rushes, passing into the
next item of the plant at great speed for a time, and then ceasing altogether.
The methods necessarily adopted for purifying the crude gas are treated of
in Chapter V.; but it is manifest now that no purifying material can prove
efficient unless the acetylene passes through it at a uniform rate, and at one
which is as slow as other conditions permit. For this reason the proper
position of the holder in an acetylene installation is before the purifier, and
immediately after the condenser or washer which adjoins the generator. By
this method of design the holder is filled up irregularly, the gas passing into
it sometimes at full speed, sometimes at an imperceptible rate; but if the
holder is well balanced and guided this is a matter of no consequence. Out
of the holder, on the other hand, the gas issues at a rate which is dependent
upon the number and capacity of the burners in operation at any moment;
and in ordinary conditions this rate is so much more uniform during the
whole of an evening than the rate at which the gas is evolved from the
carbide, that a purifier placed after the holder is given a far better
opportunity of extracting the impurities from the acetylene than it would
have were it situated before the holder, as is invariably the case on coal-gas
works.

For many reasons, such as capacity for isolation when being recharged or
repaired, it is highly desirable that each item in an acetylene plant shall be
separated, or capable of separation, from its neighbours; and this
observation applies with great force to the holder and the decomposing
vessel of the generator. In all large plants each vessel should be fitted with a
stopcock at its inlet and, if necessary, one at its outlet, being provided also
with a by-pass so that it can be thrown out of action without interfering with
the rest of the installation. In the best practice the more important vessels,
such as the purifiers, will be in duplicate, so that unpurified gas need not be
passed into the service while a solitary purifier is being charged afresh. In
smaller plants, where less skilled labour will probably be bestowed on the
apparatus, and where hand-worked cocks are likely to be neglected or
misused, some more, automatic arrangement for isolating each item is
desirable. There are two automatic devices which may be employed for the
purposes in view, the non-return valve and the water-seal. The non-return
valve is simply a mushroom or ball valve without handle, lifted off its seat
by gas passing from underneath whenever the pressure of the gas exceeds

Page 134

the weight of the valve, but falling back on to its seat and closing the pipe
when the pressure decreases or when pressure above is greater than that
below. The apparatus works perfectly with a clean gas or liquid which is not
corrosive; but having regard to the possible presence of tarry products, lime
dust, or sludge, condensed water loaded with soluble impurities, &c., in the
acetylene, a non-return valve is not the best device to adopt, for both it and
the hand-worked cock or screw- down valve are liable to stick and give
trouble. The best arrangement in all respects, especially between the
generator and the holder, is a water-seal. A water-seal in made by leading
the mouth of a pipe delivering gas under the level of water in a suitable
receptacle, so that the issuing gas has to bubble through the liquid. Gas
cannot pass backwards through the pipe until it has first driven so much
liquid before it that the level in the seal has fallen below the pipe's mouth;
and if the end of the pipe is vertical more pressure than can possibly be
produced in the apparatus is necessary to effect this. Omitting the side tube
b, one variety of water-seal is shown at D in Fig. 7 on page 103. The water
being at the level l, gas enters at a and bubbles through it, escaping from the
apparatus at c. It cannot return from c to a without driving the water out of
the vessel till its level falls from f to g; and since the area of the vessel is
much greater than that of the pipe, so great a fall in the vessel would
involve a far greater rise in a. It is clear that such a device, besides acting as
a non-return valve, also fulfils two other useful functions: it serves to
collect and retain all the liquid matter that may be condensed in the pipe a
from the spot at which it was originally level or was given a fall to the seal,
as well as that condensing in c as far as the spot where c dips again; and it
equally acts as a washer to the gas, especially if the orifice g of the gas-inlet
pipe is not left with a plain mouth as represented in the figure, but
terminates in a large number of small holes, the pipe being then preferably
prolonged horizontally, with minute holes in it so as to distribute the gas
throughout the entire vessel. Such an apparatus requires very little attention.
It may with advantage be provided with the automatic arrangement for
setting the water-level shown at d and e. d is a tunnel tube extending almost
to the bottom of the vessel, and e is a curved run-off pipe of the form
shown. The lower part of the upper curve in e is above the level f, being
higher than f by a distance equal to that of the gas pressure in the pipes; and
therefore when water is poured into the funnel it fills the vessel till the
internal level reaches f, when the surplus overflows of itself. The operation

Page 135

thus not only adjusts the quantity of water present to the desired level so
that a cannot become unsealed, but it also renews the liquid when it has
become foul and nearly saturated with dissolved and condensed impurities
from the acetylene. It would be a desirable refinement to give the bottom of
the vessel a slope to the mouth of e, or to some other spot where a large-
bore draw-off cock could be fitted for the purpose of extracting any sludge
of lime, &c., that may collect. By having such a water-seal, or one simpler
in construction, between the generator and the holder, the former may be
safely opened at any time for repairs, inspection, or the insertion of a fresh
charge of carbide while the holder is full of gas, and the delivery of
acetylene to the burners at a specified pressure will not be interrupted. If a
cock worked by hand were employed for the separation of the holder from
the generator, and the attendant were to forget to close it, part or all of the
acetylene in the holder would escape from the generator when it was
opened or disconnected.

Especially when a combined washer and non-return valve follows
immediately after a generator belonging to the shoot type, and the mouth of
the shoot is open to the air in the plant-house, it is highly desirable that the
washer shall be fitted with some arrangement of an automatic kind for
preventing the water level rising much above its proper position. The liquid
in a closed washer tends to rise as the apparatus remains in use, water
vapour being condensed within it and liquid water, or froth of lime, being
mechanically carried forward by the stream of acetylene coming from the
decomposing chamber. In course of time, therefore, the vertical depth to
which the gas-inlet pipe in the washer is sealed by the liquid increases; and
it may well be that eventually the depth in question, plus the pressure
thrown by the holder bell, may become greater than the pressure which can
be set up inside the generator without danger of gas slipping under the
lower edge of the shoot. Should this state of things arise, the acetylene can
no longer force its way through the washer into the holder bell, but will
escape from the mouth of the shoot; filling the apparatus-house with gas,
and offering every opportunity for an explosion if the attendant disobeys
orders and takes a naked light with him to inspect the plant.

It is indispensable that every acetylene apparatus shall be fitted with a
safety-valve, or more correctly speaking a vent-pipe. The generator must

Page 136

have a vent-pipe in case the gas-main leading to the holder should become
blocked at any time, and the acetylene which continues to be evolved in all
water-to-carbide apparatus, even after the supply of water has been cut off
be unable to pass away. Theoretically a non-automatic apparatus does not
require a vent-pipe in its generator because all the gas enters the holder
immediately, and is, or should be, unable to return through the intermediate
water seal; practically such a safeguard is absolutely necessary for the
reason given. The holder must have a safety-valve in case the cutting-off
mechanism of the generator fails to act, and more gas passes into it than it
can store. Manifestly the pressure of the gas in a water-sealed holder or in
any generator fitted with a water-sealed lid cannot rise above that
corresponding with the depth of water in the seal; for immediately the
pressure, measured in inches of water, equals the depth of the sealing liquid,
the seal will be blown out, and the gas will escape. Such an occurrence,
however, as the blowing of a seal must never be possible in any item of an
acetylene plant, more especially in those items that are under cover, for the
danger that the issuing gas might be fired or might produce suffocation
would be extremely great. Typical simple forms of vent-pipe suitable for
acetylene apparatus are shown in Fig. 7. In each case the pipe marked
"vent" is the so-called safety-valve; it is open at its base for the entry of gas,
and open at its top for the escape of the acetylene into the atmosphere, such
top being in all instances carried through the roof of the generator-house
into the open air, and to a spot distant from any windows of that house or of
the residence, where it can prove neither dangerous nor a nuisance by
reason of its odour. At A is represented the vent-pipe of a displacement
vessel, which may either be part of a displacement holder or of a generator
working on the displacement principle. The vent-pipe is rigidly fixed to the
apparatus. If gas is generated within the closed portion of the holder or
passes through it, and if the pressure so set up remains less than that which
is needed to move the water from the level l to the levels l' and l", the
mouth of the pipe is under water, and acetylene cannot enter it; but
immediately such an amount of gas is collected, or such pressure is
produced that the interior level sinks below l", which is that of the mouth of
the pipe, it becomes unsealed, and the surplus gas freely escapes. There are
two minor points in connexion with this form of vent-pipe often
overlooked. At the moment when the water arrives at l" in the closed half of
the apparatus, its level in the interior of the vent-pipe stands at l', identical

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with that in the open hall of the apparatus (for the mouth of the vent-pipe
and the water in the open hall of the apparatus are alike exposed to the
pressure of the atmosphere only). When the water, then, descends just
below l" there is an amount of water inside the pipe equal in height to the
distance between l' and l"; and before the acetylene can escape, it must
either force this water as a compact mass out of the upper mouth of the
vent-pipe (which it is clearly not in a position to do), drive it out of the
upper mouth a little at a time, or bubble through it till the water is gradually
able to run downwards out of the pipe as its lower opening is more fully
unsealed. In practice the acetylene partly bubbles through this water and
partly drives it out of the mouth of the pipe; on some occasions temporarily
yielding irregular pressures at the burners which cause them to jump, and
always producing a gurgling noise in the vent- pipe which in calculated to
alarm the attendant. If the pipe is too small in diameter, and especially if its
lower orifice is cut off perfectly horizontal and constricted slightly, the
water may refuse to escape from the bottom altogether, and the pipe will
fail to perform its allotted task. It is better therefore to employ a wide tube,
and to cut off its mouth obliquely, or to give its lower extremity the shape of
an inverted funnel. At the half of the central divided drawing marked B
(Fig. 7) is shown a precisely similar vent-pipe affixed to the bell of a rising
holder, which behaves in an identical fashion when by the rising of the bell
its lower end is lifted out of the water in the tank. The features described
above as attendant, upon the act of unsealing of the displacement-holder
vent-pipe occur here also, but to a less degree; for the water remaining in
the pipe at the moment of unsealing is only that which corresponds with the
vertical distance between l' and l", and in a rising holder this is only a
height always equal to the pressure given by the bell. Nevertheless this form
of vent-pipe produces a gurgling noise, and would be better for a trumpet-
shaped mouth. A special feature of the pipe in B is that unless it is placed
symmetrically about the centre of the bell its weight tends to throw the bell
out of the vertical, and it may have to be supported at its upper part;
conversely, if the pipe is arranged concentrically in the bell, it may be
employed as part of the guiding arrangement of the bell itself. Manifestly,
as the pipe must be long enough to extend through the roof of the generator-
house, its weight materially increases the weight of the bell, and
consequently the gas pressure in the service; this fact is not objectionable
provided due allowance is made for it. So tall a vent-pipe, however,

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seriously raises the centre of gravity of the bell and may make it top-heavy.
To work well the centre of gravity of a holder bell should be as low as
possible, any necessary weighting being provided symmetrically about its
circumference and close to its bottom edge. The whole length of an
ascending vent-pipe need not be carried by the rising bell, because the
lower portion, which must be supported by the bell, can be arranged to slide
inside a wider length of pipe which is fixed to the roof of the generator-
house at the point where it passes into the open air.

A refinement upon this vent-pipe is represented at C, where it is rigidly
fastened to the tank of the holder, and has its internal aperture always above
the level of the water in the apparatus. Rigidly fixed to the crown of the bell
is a tube of wider diameter, h, which is closed at its upper end. h is always
full of gas, and its mouth is normally beneath the level of the water in the
seal; but when the bell rises to its highest permissible position, the mouth of
h comes above the water, and communication is opened between the holder
and the outer atmosphere. No water enters the vent-pipe from the holder,
and therefore no gurgling or irregular pressure is produced. Another
excellent arrangement of a vent-pipe, suggested by Klinger of
Gumpoldskirchen, is shown at D, a drawing which has already been partly
considered as a washer and water-seal. For the present purpose the main
vessel and its various pipes are so dimensioned that the vertical height g to f
is always appreciably greater than the gas pressure in the service or in the
generator or gasholder to which it is connected. In these circumstances the
gas entering at a depresses the water in the pipe below the level f to an
extent equal to the pressure at which it enters that pipe--an extent normally
less than the distance f to g; and therefore gas never passes into the body of

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the vessel, but travels away by the side tube b (which in former references
to this drawing was supposed to be absent). If, however, the pressure at a
exceeds that of the vertical height f to g, gas escapes at g through the water,
and is then free to reach the atmosphere by means of the vent c. As before,
d serves to charge the apparatus with water, and e to ensure a proper amount
being added. Clearly no liquid can enter the vent-pipe in this device. Safety-
valves such as are added to steam-boilers and the like, which consist of a
weighted lever holding a conical valve down against its seat, are not
required in acetylene apparatus, for the simpler hydraulic seals discussed
above can always be fitted wherever they may be needed. It should be
noticed that these vent-pipes only come into operation in emergencies,
when they are required to act promptly. No economy is to be effected by
making them small in diameter. For obvious reasons the vent-pipe of a
holder should have a diameter equal to that of the gas-inlet tube, and the
vent-pipe of a generator be equal in size to the gas-leading tube.

FROTHING IN GENERATORS.--A very annoying trouble which crops up
every now and then during the evolution of acetylene consists in the
production of large masses of froth within the generator. In the ordinary
way, decomposition of carbide is accompanied by a species of
effervescence, but the bubbles should break smartly and leave the surface of
the liquid reasonably free from foam. Sometimes, however, the bubbles do
not break, but a persistent "head" of considerable height is formed. Further
production of gas only increases the thickness of the froth until it rises so
high that it is carried forward through the gas-main into the next item of the
plant. The froth disappears gradually in the pipes, but leaves in them a
deposit of lime which sooner or later causes obstructions by accumulating
at the angles and dips; while during its presence in the main the steady
passage of gas to the holder is interrupted and the burners may even be
made to jump. Manifestly the defect is chiefly, if not always, to be noticed
in the working of carbide-to-water generators. The phenomenon has been
examined by Mauricheau-Beaupré, who finds that frothing is not
characteristic of pure carbide and that it cannot be attributed to any of the
impurities normally present in commercial carbide. If, however, the carbide
contains calcium chloride, frothing is liable to occur. A 0.1 per cent.
solution of calcium chloride appears to yield some foam when carbide is
decomposed in it, and a 1 per cent. solution to foam in a pronounced

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manner. In the absence of calcium chloride, the main cause of frothing
seems to be the presence in the generator of new paint or tar. If a generator
is taken into use before the paint in any part of it which becomes moistened
by warm lime-water has had opportunity of drying thoroughly hard,
frothing is certain to occur; and even if the carbide has been stored for only
a short time in a tin or drum which has been freshly painted, a production of
froth will follow when it is decomposed in water. The products of the
polymerisation of acetylene also tend to produce frothing, but not to such an
extent as the turpentine in paint and the lighter constituents of coal-tar.
Carbide stored even temporarily in a newly painted tin froths on
decomposition because it has absorbed among its pores some of the volatile
matter given off by the paint during the process of desiccation.

THE "DRY" PROCESS OF GENERATION.--A process for generating
acetylene, totally different in principle from those hitherto considered, has
been introduced in this country. According to the original patents of G. J.
Atkins, the process consisted in bringing small or powdered carbide into
mechanical contact with some solid material containing water, the water
being either mixed with the solid reagent or attached to it as water of
crystallisation. Such reagents indeed were claimed as crude starch and the
like, the idea being to recover a by-product of pecuniary value. Now the
process seems to be known only in that particular form in which granulated
carbide is treated with crystallised sodium carbonate, i.e., common washing
soda. Assuming the carbide employed to be chemically pure and the
reaction between it and the water of crystallisation contained in ordinary
soda crystals to proceed quantitatively, the production of acetylene by the
dry process should be represented by the following chemical equation:

5CaC_2 + Na_2CO_3.10H_2O = 5C_2H_2 + 5Ca(OH)_2 + Na_2CO_3.

On calculating out the molecular weights, it will be seen that 286 parts of
washing soda should suffice for the decomposition of 320 parts of pure
calcium carbide, or in round numbers 9 parts of soda should decompose 10
parts of carbide. In practice, however, it seems to be found that from 1 to
1.5 parts of soda are needed for every part of carbide.

The apparatus employed is a metal drum supported on a hollow horizontal
spindle, one end of which is closed and carries a winch handle, and the

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other end of which serves to withdraw the gas generated in the plant. The
drum is divided into three compartments by means of two vertical partitions
so designed that when rotation proceeds in one particular direction portions
of the two reagents stored in one end compartment pass into the centre
compartment; whereas when rotation proceeds in the opposite direction, the
material in the centre compartment is merely mixed together, partly by the
revolution of the drum, partly with the assistance of a stationary agitator
slung loosely from the central spindle. The other end compartment contains
coke or sawdust or other dry material through which the gas passes for the
removal of lime or other dust carried in suspension as it issues from the
generating compartment. The gas then passes through perforations into the
central spindle, one end of which is connected by a packed joint with a
fixed pipe, which leads to a seal or washer containing petroleum.
Approached from a theoretical standpoint, it will be seen that this method of
generation entirely sacrifices the advantages otherwise accruing from the
use of liquid water as a means for dissipating the heat of the chemical
reaction, but on the other hand, inasmuch as the substances are both solid,
the reaction presumably occurs more slowly than it would in the presence
of liquid water; and moreover the fact that the water employed to act upon
the carbide is in the solid state and also more or less combined with the rest
of the sodium carbonate molecule, means that, per unit of weight, the water
decomposed must render latent a larger amount of heat than it would were it
liquid. Experiments made by one of the authors of this book tend to show
that the gas evolved from carbide by the dry process contains rather less
phosphorus than it might in other conditions of generation, and as a fact gas
made by the dry process is ordinarily consumed without previous passage
through any chemical purifying agent. It is obvious, however, that the use
of the churn described above greatly increases the labour attached to the
production of the gas; while it is not clear that the yield per unit weight of
carbide decomposed should be as high as that obtained in wet generation.
The inventor has claimed that his by-product should be valuable and
saleable, apparently partly on the ground that it should contain caustic soda.
Evidence, however, that a reaction between the calcium oxide or hydroxide
and the sodium carbonate takes place in the prevailing conditions is not yet
forthcoming, and the probabilities are that such decomposition would not
occur unless the residue were largely diluted with water. [Footnote: The
oldest process employed for manufacturing caustic soda consisted in mixing

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a solution of sodium carbonate with quick or slaked lime, and it has been
well established that the causticisation of the soda will not proceed when
the concentration of the liquid is greater than that corresponding with a
specific gravity of about 1-10, i.e., when the liquid contains more than some
8 to 10 per cent, of sodium hydroxide.] Conversely there are some grounds
for believing that the dry residue is less useful than an ordinary wet residue
for horticultural purposes, and also for the production of whitewash. From a
financial standpoint, the dry process suffers owing to the expense involved
in the purchase of a second raw material, for which but little compensation
can be discovered unless it is proved that the residue is intrinsically more
valuable than common acetylene-lime and can be sold or used
advantageously by the ordinary owner of an installation. The discarding of
the chemical purifier at the present day is a move of which the advantage
may well be overrated.

ARTIFICIAL LIGHTING OF GENERATOR SHEDS.--It has already been
argued that all normal or abnormal operations in connexion with an
acetylene generating plant should be carried out, if possible, by daylight;
and it has been shown that on no account must a naked light ever be taken
inside the house containing such a plant. It will occasionally happen,
however, that the installation must be recharged or inspected after nightfall.
In order to do this in safety, a double window, incapable of being opened,
should be fitted in one wall of the house, as far as possible from the door,
and in such a position that the light may fall on to all the necessary places.
Outside this window may be suspended an ordinary hand- lantern burning
oil or paraffin; or, preferably, round this window may be built a closed
lantern into which some source of artificial light may be brought. If the
acetylene plant has an isolated holder of considerable size, there is no
reason at all why a connexion should not be made with the service-pipes,
and an acetylene flame be used inside this lantern; but with generators of
the automatic variety, an acetylene light is not so suitable, because of the
fear that gas may not be available precisely at the moment when it is
necessary to have light in the shed. It would, however, be a simple matter to
erect an acetylene burner inside the lantern in such a way that when needed
an oil-lamp or candle could be used instead. Artificial internal light of any
kind is best avoided; the only kind permissible being an electric glow-lamp.
If this is employed, it should be surrounded by a second bulb or gas-tight

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glass jacket, and preferably by a wire cage as well; the wires leading to it
must be carefully insulated, and all switches or cut-outs (which may
produce a spark) must be out of doors. The well-known Davy safety or
miner's lamp is not a trustworthy instrument for use with acetylene because
of (a) the low igniting-point of acetylene; (b) the high temperature of its
flame; and (c) the enormous speed at which the explosive wave travels
through a mixture of acetylene and air. For these reasons the metallic gauze
of the Davy lamp is not so efficient a protector of the flame as it is in cases
of coal-gas, methane, &c. Moreover, in practice, the Davy lamp gives a
poor light, and unless in constant use is liable to be found out of order when
required. It should, however, be added that modern forms of the safety
lamp, in which the light is surrounded by a stout glass chimney and only
sufficient gauze is used for the admission of fresh air and for the escape of
the combustion products, appear quite satisfactory when employed in an
atmosphere containing some free acetylene.

Page 144

CHAPTER IV
THE SELECTION OF AN ACETYLENE GENERATOR

In Chapter II. an attempt has been made to explain the physical and
chemical phenomena which accompany the interaction of calcium carbide
and water, and to show what features in the reaction are useful and what
inconvenient in the evolution of acetylene on a domestic or larger scale.
Similarly in Chapter III. have been described the various typical devices
which may be employed in the construction of different portions of
acetylene plant, so that the gas may be generated and stored under the best
conditions, whether it is evolved by the automatic or by the non- automatic
system. This having been done, it seemed of doubtful utility to include in
the first edition of this work a long series of illustrations of such generators
as had been placed on the markets by British, French, German, and
American makers. It would have been difficult within reasonable limits to
have reproduced diagrams of all the generators that had been offered for
sale, and absolutely impossible within the limits of a single hand-book to
picture those which had been suggested or patented. Moreover, some
generating apparatus appeared on the market ephemerally; some was
constantly being modified in detail so as to alter parts which experience or
greater knowledge had shown the makers to be in need of alteration, while
other new apparatus was constantly being brought out. On these and other
grounds it did not appear that much good purpose would have been served
by describing the particular apparatus which at that time would have been
offered to prospective purchasers. It seemed best that the latter should
estimate the value and trustworthiness of apparatus by studying a section of
it in the light of the general principles of construction of a satisfactory
generator as enunciated in the book. While the position thus taken by the
authors in 1903 would still not be incorrect, it has been represented to them
that it would scarcely be inconsistent with it to give brief descriptions of
some of the generators which are now being sold in Great Britain and a few
other countries. Six more years' experience in the design and manufacture
of acetylene plant has enabled the older firms of manufacturers to fix upon

Page 145

certain standard patterns for their apparatus, and it may confidently be
anticipated that many of these will survive a longer period. Faulty devices
and designs have been weeded out, and there are lessons of the past as well
as theoretical considerations to guide the inventor of a new type of
generator. On those grounds, therefore, an attempt has now been made to
give brief descriptions, with sectional views, of a number of the generators
now on the market in Great Britain. Moreover, as the first edition of this
book found many readers in other countries, in several of which there is
greater scope for the use of acetylene, it has been decided to describe also a
few typical or widely used foreign generators. All the generators described
must stand or fall on their merits, which cannot be affected by any opinion
expressed by the authors. In the descriptions, which in the first instance
have generally been furnished by the manufacturers of the apparatus, no
attempt has therefore been made to appraise the particular generators, and
comparisons and eulogistic comments have been excluded. The
descriptions, however, would nevertheless have been somewhat out of place
in the body of this book; they have therefore been relegated to a special
Appendix. It has, of course, been impossible to include the generators of all
even of the English manufacturers, and doubtless many trustworthy ones
have remained unnoticed. Many firms also make other types of generators
in addition to those described. It must not be assumed that because a
particular make of generator is not mentioned it is necessarily faulty. The
apparatus described may be regarded as typical or well known, and
workable, but it is not by reason of its inclusion vouched for in any other
respect by the authors. The Appendix is intended, not to bias or modify the
judgment of the would-be purchaser of a generator, but merely to assist him
in ascertaining what generators there are now on the market.

The observations on the selection of a generator which follow, as well as
any references in other chapters to the same matter, have been made without
regard to particular apparatus of which a description may (or may not)
appear in the Appendix. With this premise, it may be stated that the
intending purchaser should regard the mechanism of a generator as shown
in a sectional view or on inspection of the apparatus itself. If the generator
is simple in construction, he should be able to understand its method of
working at a glance, and by referring it to the type (vide Chapter III.) to
which it belongs, be able to appraise its utility from a chemical and physical

Page 146

aspect from what has already been said. If the generator is too complicated
for ready understanding of its mode of working, it is not unlikely to prove
too complicated to behave well in practice. Not less important than the
mechanism of a generator is good construction from the mechanical point
of view, i.e., whether stout metal has been employed, whether the seams
and joints are well finished, and whether the whole apparatus has been built
in the workman- like fashion which alone can give satisfaction in any kind
of plant. Bearing these points in mind, the intending purchaser may find
assistance in estimating the mechanical value of an apparatus by perusing
the remainder of this chapter, which will be devoted to elaborating at length
the so-called scientific principles underlying the construction of a
satisfactory generator, and to giving information on the mechanical and
practical points involved.

It is perhaps desirable to remark that there is scarcely any feature in the
generation of acetylene from calcium carbide and water--certainly no
important feature--which introduces into practice principles not already
known to chemists and engineers. Once the gas is set free it ranks simply as
an inflammable, moisture-laden, somewhat impure, illuminating and heat-
giving gas, which has to be dried, purified, stored, and led to the place of
combustion; it is in this respect precisely analogous to coal- gas. Even the
actual generation is only an exothermic, or heat-producing, reaction
between a solid and a liquid, in which rise of temperature and pressure must
be prevented as far as possible. Accordingly there is no fundamental or
indispensable portion of an acetylene apparatus which lends itself to the
protection of the patent laws; and even the details (it may be said truthfully,
if somewhat cynically) stand in patentability in inverse ratio to their
simplicity and utility.

During the early part of 1901 a Committee appointed by the British Home
Office, "to advise as to the conditions of safety to which acetylene
generators should conform, and to carry out tests of generators in the
market in order to ascertain how far those conform with such conditions,"
issued a circular to the trade suggesting that apparatus should be sent them
for examination. In response, forty-six British generators were submitted
for trial, and were examined in a fashion which somewhat exceeded the
instructions given to the Committee, who finally reported to the Explosives

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Department of the Home Office in a Blue Book, No. Cd. 952, which can be
purchased through any bookseller. This report comprises an appendix in
which most of the apparatus are illustrated, and it includes the result of the
particular test which the Committee decided to apply. Qualitatively the test
was useful, as it was identical in all instances, and only lacks full utility
inasmuch as the trustworthiness of the automatic mechanism applied to
such generators as were intended to work on the automatic system was not
estimated. Naturally, a complete valuation of the efficiency of automatic
mechanism cannot be obtained from one or even several tests, it demands
long-continued watching; but a general notion of reliability might have
been obtained. Quantitatively, however, the test applied by the Committee is
not so free from reproach, for, from the information given, it would appear
to have been less fair to some makers of apparatus than to others.
Nevertheless the report is valuable, and indicates the general character of
the most important apparatus which were being offered for sale in the
United Kingdom in 1900-1901.

It is not possible to give a direct answer to the question as to which is the
best type of acetylene generator. There are no generators made by
responsible firms at the present time which are not safe. Some may be
easier to charge and clean than others; some require more frequent attention
than others; some have moving parts less likely to fail, when handled
carelessly, than others; some have no moving mechanism to fail. For the
illumination of a large institution or district where one man can be fully
occupied in attending to the plant, cleaning, lighting, and extinguishing the
lamps, or where other work can be found for him so as to leave him an hour
or so every day to look after the apparatus, the hand-fed carbide-to-water
generator L (Fig. 6) has many advantages, and is probably the best of all. In
smaller installations choice must be made first between the automatic and
the non-automatic principle--the advantages most frequently lying with the
latter. If a non-automatic generator is decided upon, the hand carbide-feed
or the flooded- compartment apparatus is almost equally good; and if
automatism is desired, either a flooded-compartment machine or one of the
most trustworthy types of carbide-feed apparatus may be taken. There are
contact apparatus on the markets which appear never to have given trouble,
and those are worthy of attention. Some builders advocate their own
apparatus because the residue is solid and not a cream. If there is any

Page 148

advantage in this arising from greater ease in cleaning and recharging the
generator and in disposing of the waste, that advantage is usually
neutralised by the fear that the carbide may not have been wholly
decomposed within the apparatus; and whereas any danger arising from
imperfectly spent carbide being thrown into a closed drain may be
prevented by flooding the residue with plenty of water in an open vessel,
imperfect decomposition in the generator means a deficiency in the amount
of gas evolved from a unit weight of solid taken or purchased. In fact,
setting on one side apparatus which belong to a notoriously defective
system and such as are constructed in large sizes on a system that is only
free from overheating, &c., in small sizes; setting aside all generators which
are provided with only one decomposing chamber when they are of a
capacity to require two or more smaller ones that can more efficiently be
cooled with water jackets; and setting aside any form of plant which on
examination is likely to exhibit any of the more serious objections indicated
in this and the previous chapters, there is comparatively little to choose,
from the chemical and physical points of view, between the different types
of generators now on the markets. A selection may rather be made on
mechanical grounds. The generator must be well able to produce gas as
rapidly as it will ever be required during the longest or coldest evening; it
must be so large that several more brackets or burners can be added to the
service after the installation is complete. It must be so strong that it will
bear careless handling and the frequent rough manipulation of its parts. It
must be built of stout enough material not to rust out in a few years. Each
and all of its parts must be accessible and its exterior visible. Its pipes, both
for gas and sludge, must be of large bore (say 1 inch), and fitted at every dip
with an arrangement for withdrawing into some closed vessel the moisture,
&c., that may condense. The number of cocks, valves, and moving parts
must be reduced to a minimum; cocks which require to be shut by hand
before recharging must give way to water-seals. It must be simple in all its
parts, and its action intelligible at a glance. It must be easy to charge--
preferably even by the sense of touch in darkness. It must be easy to clean.
The waste lime must be easily removed. It must be so fitted with vent-pipes
that the pressure can never rise above that at which it is supposed to work.
Nevertheless, a generator in which these vent-pipes are often brought into
use is badly constructed and wasteful, and must be avoided. The water of
the holder seal should be distinct from that used for decomposing the

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carbide; and those apparatus where the holder is entirely separated from the
generator are preferable to such as are built all in one, even if water-seals
are fitted to prevent return of gas. Apparatus which is supposed to be
automatic should be made perfectly automatic, the water or the carbide-feed
being locked automatically before the carbide store, the decomposing
chamber, or the sludge-cock can be opened. The generating chamber must
always be in communication with the atmosphere through a water-sealed
vent-pipe, the seal of which, if necessary, the gas can blow at any time. All
apparatus should be fitted with rising holders, the larger the better.
Duplicate copies of printed instructions should be demanded of the maker,
one copy being kept in the generator-house, and the other elsewhere for
reference in emergencies. These instructions must give simple and precise
information as to what should be done in the event of a breakdown as well
as in the normal manipulation of the plant. Technical expressions and
descriptions of parts understood only by the maker must be absent from
these rules.

ADDENDUM.

BRITISH AND FOREIGN REGULATIONS FOR THE CONSTRUCTION
AND INSTALLATION OF ACETYLENE GENERATING PLANT

Dealing with the "conditions which a generator should fulfil before it can be
considered as being safe," the HOME OFFICE COMMITTEE of 1901
before mentioned write as follows:

1. The temperature in any part of the generator, when run at the maximum
rate for which it is designed, for a prolonged period, should not exceed 130°
C. This may be ascertained by placing short lengths of wire, drawn from
fusible metal, in those parts of the apparatus in which heat is liable to be
generated.

2. The generator should have an efficiency of not less than 90 per cent.,
which, with carbide yielding 5 cubic feet per pound, would imply a yield of
4.5 cubic feet for each pound of carbide used.

3. The size of the pipes carrying the gas should be proportioned to the
maximum rate of generation, so that undue back pressure from throttling

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may not occur.

4. The carbide should be completely decomposed in the apparatus, so that
lime sludge discharged from the generator shall not be capable of
generating more gas.

5. The pressure in any part of the apparatus, on the generator side of the
holder, should not exceed that of 20 inches of water, and on the service side
of same, or where no gasholder is provided, should not exceed that of 5
inches of water.

6. The apparatus should give no tarry or other heavy condensation products
from the decomposition of the carbide.

7. In the use of a generator regard should be had to the danger of stoppage
of passage of the gas and resulting increase of pressure which may arise
from the freezing of the water. Where freezing may be anticipated, steps
should be taken to prevent it.

8. The apparatus should be so constructed that no lime sludge can gain
access to any pipes intended for the passage of gas or circulation of water.

9. The use of glass gauges should be avoided as far as possible, and, where
absolutely necessary, they should be effectively protected against breakage.

10. The air space in a generator before charging should be as small as
possible.

11. The use of copper should be avoided in such parts of the apparatus as
are liable to come in contact with acetylene.

The BRITISH ACETYLENE ASSOCIATION has drawn up the following
list of regulations which, it suggests, shall govern the construction of
generators and the installation of piping and fittings:

1. Generators shall be so constructed that, when used in accordance with
printed instructions, it shall not be possible for any undecomposed carbide
to remain in the sludge removed therefrom.

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2. The limit of pressure in any part of the generator shall not exceed that of
20 inches of water, subject to the exception that if it be shown to the
satisfaction of the Executive of the Acetylene Association that higher
pressures up to 50 inches of water are necessary in certain generators, and
are without danger, the Executive may, with the approval of the Home
Office, grant exemption for such generators, with or without conditions.

3. The limit of pressure in service-pipes, within the house, shall not exceed
10 inches of water.

4. Except when used for special industrial purposes, such as oxy- acetylene
welding, factories, lighthouses, portable apparatus containing not more than
four pounds of carbide, and other special conditions as approved by the
Association, the acetylene plant, such as generators, storage-holders,
purifiers, scrubbers, and for washers, shall be in a suitable and well-
ventilated outhouse, in the open, or in a lean-to, having no direct
communication with a dwelling-house. A blow-off pipe or safety outlet
shall be arranged in such a manner as to carry off into the open air any
overmake of gas and to open automatically if pressure be increased beyond
20 inches water column in the generating chamber or beyond 10 inches in
the gasholder, or beyond the depth of any fluid seal on the apparatus.

5. Generators shall have sufficient storage capacity to make a serious blow-
off impossible.

6. Generators and apparatus shall be made of sufficiently strong material
and be of good workmanship, and shall not in any part be constructed of
unalloyed copper.

7. It shall not be possible under any conditions, even by wrong
manipulation of cocks, to seal the generating chamber hermetically.

8. It shall not be possible for the lime sludge to choke any of the gas- pipes
in the apparatus, nor water-pipes if such be alternately used as safety-
valves.

9. In the use of a generator, regard shall be had to the danger of stoppage of
passage of the gas, and resulting increase of pressure, which may arise from

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the freezing of the water. Where freezing may be anticipated, steps shall be
taken to prevent it.

10. The use of glass gauges shall be avoided as far as possible, and where
absolutely necessary they shall be effectively protected against breakage.

11. The air space in the generator before charging shall be as small as
possible, i.e., the gas in the generating chamber shall not contain more than
8 per cent. of air half a minute after commencement of generation. A sample
of the contents, drawn from the holder any time after generation has
commenced, shall not contain an explosive mixture, i.e., more than 18 per
cent, of air. This shall not apply to the initial charges of the gasholder, when
reasonable precautions are taken.

12. The apparatus shall produce no tarry or other heavy condensation
products from the decomposition of the carbide.

13. The temperature of the gas, immediately on leaving the charge, shall not
exceed 212° F. (100° C.)

14. No generator shall be sold without a card of instructions suitable for
hanging up in some convenient place. Such instructions shall be of the most
detailed nature, and shall not presuppose any expert knowledge whatever on
the part of the operator.

15. Notice to be fixed on Generator House Door, "NO LIGHTS OR
SMOKING ALLOWED."

16. Every generator shall have marked clearly upon the outside a statement
of the maximum number of half cubic foot burners and the charge of
carbide for which it is designed.

17. The Association strongly advise the use of an efficient purifier with
generating plant for indoor lighting.

18. No composition piping shall be used in any part of a permanent
installation.

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19. Before being covered in, all pipe-work (main and branches) shall be
tested in the following manner: A special acetylene generator, giving a
pressure of at least 10 inches water column in a gauge fixed on the furthest
point from the generator, shall be connected to the pipe-work. All points
shall be opened until gas reaches them, when they shall be plugged and the
main cock on the permanent generator turned off, but all intermediate main
cocks shall be open in order to test underground main and all connexions.
The gauge must not show a loss after generator has been turned off for at
least two hours.

20. After the fittings (pendants, brackets, &c.) have been fixed and all
burners lighted, the gas shall be turned off at the burners and the whole
installation shall be re-tested, but a pressure of 5 inches shall be deemed
sufficient, which shall not drop lower than to 4-1/2 inches on the gauge
during one hour's test.

21. No repairs to, or alterations in, any part of a generator, purifier, or other
vessel which has contained acetylene shall be commenced, nor, except for
recharging, shall any such part or vessel be cleaned out until it has been
completely filled with water, so as to expel any acetylene or mixture of
acetylene and air which may remain in the vessel, and may cause a risk of
explosion.

Recommendation.--It being the general practice to store carbide in the
generator-house, the Association recommend that the carbide shall be
placed on a slightly raised platform above the floor level.

THE BRITISH FIRE OFFICES COMMITTEE in the latest revision, dated
July 15, 1907, of its Rules and Regulations re artificial lighting on insured
premises, includes the following stipulations applicable to acetylene:

Any apparatus, except as below, for generating, purifying, enriching,
compressing or storing gas, must be either in the open or in a building used
for such purposes only, not communicating directly with any building
otherwise occupied.

An acetylene portable apparatus is allowed, provided it holds a charge of
not more than 2 lb. of carbide.

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A cylinder containing not more than 20 cubic feet of acetylene compressed
and (or) dissolved in accordance with an Order of Secretary of State under
the Explosives Act, 1875, is allowed.

The use of portable acetylene lamps containing charges of carbide
exceeding the limit of 2 lb. allowed under these Rules (the average charge
being about 18 lb.) is allowed in the open or in buildings in course of
erection.

Liquid acetylene must not be used or stored on the premises.

The pipe, whether flexible or not, connecting an incandescent gas lamp to
the gas-supply must be of metal with metal connexions.

(The reference in these Rules to the storage of carbide has been quoted in
Chapter II. (page 19).)

These rules are liable to revision from time to time.

The GERMAN ACETYLENE VEREIN has drawn up (December 1904) the
following code of rules for the construction, erection, and manipulation of
acetylene apparatus:

I. Rules for Construction.

1. All apparatus for the generation, purification, and storage of acetylene
must be constructed of sheet or cast iron. Holder tanks may be built of
brick.

2. When bare, galvanised, or lead-coated sheet-iron is used, the sides of
generators, purifiers, condensers, holder tanks, and (if present) washers and
driers must be built with the following gauges as minima:

Holder bells. All other
apparatus.

Up to 7 cubic feet capacity 0.75 mm. 1.00 mm.
From 7 to 18 " 1.00 1.25

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From 18 to 53 " 1.25 1.50
Above 53 " 1.50 2.00

When not constructed of cast-iron, the bottoms, covers, and "manhole" lids
must be 0.5 mm. thicker in each respective size.

In all circumstances, the thickness of the walls--especially in the case of
apparatus not circular in horizontal section--must be such that alteration in
shape appears impossible, unless deformation is guarded against in other
ways.

Generators must be so constructed that when they are being charged the
carbide cannot fall into the residue which has already been gasified; and the
residues must always be capable of easy, complete, and safe removal.

3. Generators, purifiers, and holders must be welded, riveted or folded at
the seams; soft solder is only permissible as a tightening material.

4. Pipes delivering acetylene, or uniting the apparatus, must be cast- or
wrought-iron. Unions, cocks, and valves must not be made of copper; but
the use of brass and bronze is permitted.

5. When cast-iron is employed, the rules of the German Gas and Water
Engineers are to be followed.

6. In generators where the whole amount of carbide introduced is not
gasified at one time, it must be possible to add fresh water or carbide in
safety, without interfering with the action of the apparatus. In such
generators the size of the gasholder space is to be calculated according to
the quantity of carbide which can be put into the generator. For every 1
kilogramme of carbide the available gasholder space must be: for the first
50 kilos., 20 litres; for the next 50 kilos., 15 litres; for amounts above 100
kilos., 10 litres per kilo. [One kilogramme may be taken as 2.2 lb., and 28
litres as 1 cubic foot.]

The generator must be large enough to supply the full number of normal
(10-litre) burners with gas for 5 hours; the yield of acetylene being taken at
290 litres per kilo. [4.65 cubic feet per lb.]

Page 156

The gasholder space of apparatus where carbide is not stored must be at
least 30 litres for every normal (10-litre) flame.

7. The gasholder must be fitted with an appliance for removing any gas
which may be generated (especially when the apparatus is first brought into
action) after the available space is full. This vent must have a diameter at
least equal to the inlet pipe of the holder.

8. Acetylene plant must be provided with purifying apparatus which
contains a proper purifying material in a suitable condition.

9. The dimensions of subsidiary apparatus, such as washers, purifiers,
condensers, pipes, and cocks must correspond with the capacity of the
plant.

10. Purifiers and washers must be constructed of materials capable of
resisting the attack of the substances in them.

11. Every generator must bear a plate giving the name of the maker, or the
seller, and the maximum number of l0-litre lights it is intended to supply. If
all the carbide put into the generator is not gasified at one time, the plate
must also state the maximum weight of carbide in the charge. The gasholder
must also bear a plate recording the maker's or seller's name, as well as its
storage capacity.

12. Rules 1 to 11 do not apply to portable apparatus serving up to two
lights, or to portable apparatus used only out of doors for the lighting of
vehicles or open spaces.

II. Rules for Erection

1. Acetylene apparatus must not be erected in or under rooms occupied or
frequented (passages, covered courts, &c.) by human beings. Generators
and holders must only be erected in apartments covered with light roofs,
and separated from occupied rooms, barns, and stables by a fire-proof wall,
or by a distance of 15 feet. Any wall is to be considered fire- proof which is
built of solid brick, without openings, and one side of which is "quite free."

Page 157

Apparatus may be erected in barns and stables, provided the space required
is partitioned off from the remainder by a fire-proof wall.

2. The doors of apparatus sheds must open outwards, and must not
communicate directly with rooms where fires and artificial lights are used.

3. Apparatus for the illumination of showmen's booths, "merry-go-rounds,"
shooting galleries, and the like must be erected outside the tents, and be
inaccessible to the public.

4. Permanent apparatus erected in the open air must be at least 15 feet from
an occupied building.

5. Apparatus sheds must be fitted at their highest points with outlet
ventilators of sufficient size; the ventilators leading straight through the roof
into the open air. They must be so arranged that the escaping gases and
vapours cannot enter rooms or chimneys.

6. The contacts of any electrical warning devices must be outside the
apparatus shed.

7. Acetylene plants must be prevented from freezing by erection in frost-
free rooms, or by the employment of a heating apparatus or other suitable
appliance. The heat must only be that of warm water or steam. Furnaces for
the heating appliance must be outside the rooms containing generators, their
subsidiary apparatus, or holders; and must be separated from such rooms by
fire-proof walls.

8. In one of the walls of the apparatus shed--if possible not that having a
door--a window must be fitted which cannot be opened; and outside that
window an artificial light is to be placed. In the usual way acetylene
lighting may be employed; but a lamp burning paraffin or oil, or a lantern
enclosing a candle, must always be kept ready for use in emergencies. In all
circumstances internal lighting is forbidden.

9. Every acetylene installation must be provided with a main cock, placed
in a conveniently accessible position so that the whole of the service may be
cut off from the plant.

Page 158

10. The seller of an apparatus must provide his customer with a sectional
drawing, a description of the apparatus, and a set of rules for attending to it.
These are to be supplied in duplicate, and one set is to be kept hanging up in
the apparatus shed.

III. Rules for Working the Apparatus.

1. The apparatus must only be opened by daylight for addition of water. If
the generator is one of those in which the entire charge of carbide is not
gasified at once, addition of fresh carbide must only be made by daylight.

2. All work required by the plant, or by any portion of it, and all ordinary
attendance needed must be performed by daylight.

3. All water-seals must be carefully kept full.

4. When any part of an acetylene apparatus or a gas-meter freezes,
notwithstanding the precautions specified in II., 7, it must be thawed only
by pouring hot water into or over it; flames, burning fuel, or red- hot iron
bars must not be used.

5. Alterations to any part of an apparatus which involve the operations of
soldering or riveting, &c., i.e., in which a fire must be used, or a spark may
be produced by the impact of hammer on metal, must only be carried out by
daylight in the open air after the apparatus has been taken to pieces. First of
all the plant must be freed from gas. This is to be done by filling every part
with water till the liquid overflows, leaving the water in it for at least five
minutes before emptying it again.

6. The apparatus house must not be used for any other operation, nor
employed for the storage of combustible articles. It must be efficiently
ventilated, and always kept closed. A notice must be put upon the door that
unauthorised persons are not permitted to enter.

7. It in forbidden to enter the house with a burning lantern or lamp, to strike
matches, or to smoke therein.

8. A search for leaks in the pipes must not be made with the aid of a light.

Page 159

9. Alterations to the service must not be made while the pipes are under
pressure, but only after the main cock has been shut.

10. If portable apparatus, such as described in I., 12, are connected to the
burners with rubber tube, the tube must be fortified with an internal or
external spiral of wire. The tube must be fastened at both ends to the cocks
with thread, copper wire, or with ring clamps.

11. The preparation, storage, and use of compressed or liquefied acetylene
is forbidden. By compressed acetylene, however, is only to be understood
gas compressed to a pressure exceeding one effective atmosphere.
Acetylene compressed into porous matter, with or without acetone, is
excepted from this prohibition.

12. In the case of plants serving 50 lights or less, not more than 100 kilos.
of carbide in closed vessels may be kept in the apparatus house besides the
drum actually in use.

A fresh drum is not to be opened before the previous one has been two-
thirds emptied. Opened drums must be closed with an iron watertight lid
covering the entire top of the vessel.

In the case of apparatus supplying over 500 lights, only one day's
consumption of carbide must be kept in the generator house. In other
respects the store of carbide for such installations is to be treated as a
regular carbide store.

13. Carbide drums must not be opened with the aid of a flame or a red-hot
iron instrument.

14. Acetylene apparatus must only be attended to by trustworthy and
responsible persons.

The rules issued by the AUSTRIAN GOVERNMENT in 1905 for the
installation of acetylene plant and the use of acetylene are divided into
general enactments relating to acetylene, and into special enactments in
regard to the apparatus and installation. The general enactments state that:

Page 160

1. The preparation and use of liquid acetylene is forbidden.

2. Gaseous acetylene, alone, in admixture, or in solution, must not be
compressed above 2 atmospheres absolute except under special permission.

3. The storage of mixtures of acetylene with air or other gases containing or
evolving free oxygen is forbidden.

4. A description of every private plant about to be installed must be
submitted to the local authorities, who, according to its size and character,
may give permission for it to be installed and brought into use either
forthwith or after special inspection. Important alterations to existing plant
must be similarly notified.

5. The firms and fitters undertaking the installation of acetylene plant must
be licensed.

The special enactments fall under four headings, viz., (a) apparatus; (b)
plant houses; (c) pipes; (d) residues.

In regard to apparatus it is enacted that:

1. The type of apparatus to be employed must be one which has been
approved by one of certain public authorities in the country.

2. A drawing and description of the construction of the apparatus and a
short explanation of the method of working it must be fixed in a
conspicuous position under cover in the apparatus house. The notice must
also contain approved general information as to the properties of calcium
carbide and acetylene, precautions that must be observed to guard against
possible danger, and a statement of how often the purifier will require to be
recharged.

3. The apparatus must be marked with the name of the maker, the year of its
construction, the available capacity of the gasholder, and the maximum
generating capacity per hour.

Page 161

4. Each constituent of the plant must be proportioned to the maximum
hourly output of gas and in particular the available capacity of the holder
must be 75 per cent. of the latter. The apparatus must not be driven above
its nominal productive capacity.

5. The productive capacity of generators in which the gasholder has to be
opened or the bell removed before recharging, or for the removal of sludge,
must not exceed 50 litres per hour, nor may the charge of carbide exceed 1
kilo.

6. Generators exceeding 50 litres per hour productive capacity must be
arranged so that they can be freed from air before use.

7. Generators exceeding 1500 litres per hour capacity must be arranged so
that the acetylene, contained in the parts of the apparatus which have to be
opened for recharging or for the removal of sludge, can be removed before
they are opened.

8. Automatic generators of which the decomposing chambers are built
inside the gasholder must not exceed 300 litres per hour productive
capacity.

9. Generators must be arranged so that after-generation cannot produce
objectionable results.

10. The holder of carbide-to-water generators must be large enough to take
all the gas which may be produced by the introduction of one charge of
carbide without undue pressure ensuing.

11. The maximum pressure permissible in any part of the apparatus is 1.1
atmosphere absolute.

12. The temperature in the gas space of a generator must never exceed 80°
C.

13. Generating apparatus, &c., must be constructed in a workmanlike
manner of metal capable of resisting rust and distortion, and, where the
metal comes in contact with carbide or acetylene, it must not be one (copper

Page 162

in particular) which forms an explosive compound with the gas. Cocks and
screw connexions, &c., of brass, bronze, &c., must always be kept clean.
Joints exposed to acetylene under pressure must be made by riveting or
welding except that in apparatus not exceeding 100 litres per hour
productive capacity double bending may be used.

14. Every apparatus must be fitted with a safety-valve or vent-pipe
terminating in a safe place in the open, and of adequate size.

15. Every apparatus must be provided with an efficient purifier so fitted that
it may be isolated from the rest of the plant and with due consideration of
the possible action of the purifying material upon the metal used.

16. Mercury pressure gauges are prohibited. Liquid gauges, if used must be
double the length normally needed, and with a cock which in automatic
apparatus must be kept shut while it is in action.

17. Proper steps must always be taken to prevent the apparatus freezing. In
the absence of other precautions water-seals and pressure-gauges must be
filled with liquid having a sufficiently low freezing-point and without action
on acetylene or the containing vessel.

18. Signal devices to show the position of the gasholder bell must not be
capable of producing sparks inside the apparatus house.

19. Leaks must not be sought for with an open flame and repairs requiring
the use of a blow-pipe, &c., must only be carried out after the apparatus has
been taken to pieces or freed from gas by flooding.

20. Apparatus must only be attended to by trustworthy and responsible
adults.

21. Portable apparatus holding not more than 1 kilo. of carbide and of not
more than 50 litres per hour productive capacity, and apparatus fixed and
used out of doors are exempt from the foregoing regulations except Nos. 11
and 12, and the first part of 13.

In regard to (b), plant houses, it is enacted that:

Page 163

1. Rooms containing acetylene apparatus must be of ample size, used for no
other purpose, have water-tight floors, be warmed without fireplaces or
chimneys, be lighted from outside through an air-tight window by an
independent artificial light, have doors opening outwards, efficient
ventilation and a store of sand or like material for fire extinction. Strangers
must be warned away.

2. Apparatus of not more than 300 litres per hour productive capacity may
be erected in basements or annexes of dwelling houses, but if of over 50
litres per hour capacity must not be placed under rooms regularly
frequented. Rooms regularly frequented and those under the same must not
be used.

3. Apparatus of more than 300 litres per hour productive capacity must be
erected in an independent building at least 15 feet distant from other
property, which building, unless it is at least 30 feet distant, must be of fire-
proof material externally.

4. Gasholders exceeding 280 cubic foot in capacity must be in a detached
room or in the open and inaccessible to strangers, and at least 30 feet from
other property and with lightning conductors.

5. In case of fire the main cock must not be shut until it is ascertained that
no one remains in the room served with the gas.

6. All acetylene installations must be known to the local fire brigade.

In regard to (c), pipes, it is enacted that:

1. Mains for acetylene must be separated from the generating apparatus by a
cock, and under a five-minute test for pressure must not show a fall of over
eight-tenths inch when the pressure is 13.8 inches, or three times the
working pressure, whichever is greater.

2. The pipes must as a rule be of iron, though lead may be used where they
are uncovered and not exposed to risk of injury. Rubber connexions may
only be used for portable apparatus, and attached to a terminal on the metal

Page 164

pipes provided with a cock, and be fastened at both ends so that they will
not slip off the nozzles.

In regard to (d), residues, it is enacted that special open or well-ventilated
pits must be provided for their reception when the apparatus exceeds 300
litres per hour productive capacity. With smaller apparatus they may be
discharged into cesspools if sufficiently diluted. The ITALIAN
GOVERNMENT regulations in regard to acetylene plant are divided into
eight sections. The first of these relates to the production and use of liquid
and compressed acetylene. The production and use of liquid acetylene is
prohibited except under the provisions of the laws relating to explosives.
Neat acetylene must not be compressed to more than l-1/2 atmospheres
except that an absolute pressure of 10 atmospheres is allowed when the gas
is dissolved in acetone or otherwise rendered free from risk. Mixtures of
acetylene with air or oxygen are forbidden, irrespective of the pressure or
proportions. Mixtures of acetylene with hydrocarbons, carbonic oxide,
hydrogen and inert gases are permitted provided the proportion of acetylene
does not exceed 50 per cent. nor the absolute pressure 10 atmospheres.

The second section relates to acetylene installations, which are classified in
four groups, viz., (a) fixed or portable apparatus supplying not more than
thirty burners consuming 20 litres per hour; (b) private installations
supplying between 30 and 200 such burners; (c) public or works
installations supplying between 30 and 200 such burners; (d) installations
supplying more than 200 such burners.

The installations must comply with the following general conditions:

1. No part of the generator when working at its utmost capacity should
attain a temperature of more than 100° C.

2. The carbide must be completely decomposed in the apparatus so that no
acetylene can be evolved from the residue. The residues must be diluted
with water before being discharged into drains or cesspools, and sludge
storage-pits must be in the open.

3. The apparatus must preclude the escape of lime into the gas and water
connexions.

Page 165

4. Glass parts must be adequately protected.

5. Rubber connexions between the generator, gasholder, and main are
absolutely prohibited with installations supplying more than 30 burners.

6. Cocks must be provided for cutting off the main and connexions from the
generator and gasholder.

7. Each burner must have an independent tap.

8. Generators of groups (b), (c), and (d) must be constructed so that no
after-generation of acetylene can take place automatically and that any
surplus gas would in any case be carried out of the generator house by a
vent-pipe.

The third section deals with generator houses, which must be well
ventilated and light; must not be used for any other purpose except to store
one day's consumption of carbide, not exceeding 300 kilos.; must be fire-
proof; must have doors opening outwards; and the vent-pipes must
terminate at a safe place in the open. Apparatus of group (b) must not be
placed in a dwelling-room and only in an adjoining room if the gasholder is
of less than 600 litres capacity. Apparatus of group (c) must be in an
independent building which must be at least 33 feet from occupied premises
if the capacity of the gasholder is 6000 litres and upwards. Half this
distance suffices for gasholders containing 600 to 6000 litres. These
distances may be reduced at the discretion of the local authorities provided
a substantial partition wall at least 1 foot thick is erected. Apparatus of
group (d) must be at least 50 feet from occupied premises and the gasholder
and generator must not be in the same building.

The fourth section deals with the question of authorisation for the
installation of acetylene plant. Apparatus of group (a) may be installed
without obtaining permission from any authorities. In regard to apparatus of
the other groups, permission for installation must be obtained from local or
other authorities.

The fifth section relates to the working of acetylene plant. It makes the
concessionaires and owners of the plant responsible for the manipulation

Page 166

and supervision of the apparatus, and for the employment of suitable
operators, who must not be less than 18 years of age.

The sixth section relates to the inspection of acetylene plant from time to
time by inspectors appointed by the local or other authorities. Apparatus of
group (a) is not subject to these periodical inspections.

The seventh section details the fees payable for the inspection of
installations and carbide stores, and fixes the penalties for non- compliance
with the regulations.

The eighth section refers to the notification of the position and description
of all carbide works, stores, and acetylene installations to the local
authorities.

The HUNGARIAN GOVERNMENT rules for the construction and
examination of acetylene plant forbid the use of copper and of its alloys;
cocks, however, may be made of a copper alloy. The temperature in the gas
space of a fixed generator must not exceed 50° C., in that of a portable
apparatus 80° C. The maximum effective pressure permissible is 0.15
atmosphere.

The CONSEIL D'HYGIÈNE DE LA SEINE IN FRANCE allows a
maximum pressure of 1.5 metres, i.e., 59 inches, of water column in
generators used for the ordinary purposes of illumination; but apparatus
intended to supply gas to the low-pressure oxy-acetylene blowpipe (see
Chapter IX.) may develop up to 2.5 metres, or 98.5 inches of water
pressure, provided copper and its alloys are entirely excluded from the plant
and from the delivery- pipes.

The NATIONAL BOARD OF FIRE UNDERWRITERS OF THE UNITED
STATES OF AMERICA has issued a set of rules and requirements, of
which those relating to acetylene generators and plant are reproduced
below. The underwriters state that, "To secure the largest measure of safety
to life and property, these rules for the installation of acetylene gas
machines must be observed."

Page 167

RULES FOR THE INSTALLATION AND USE OF ACETYLENE GAS
GENERATORS. [Footnote: The "gallon" of these rules is, of course, the
American gallon, which is equal to 0.83 English standard gallon.]

The use of liquid acetylene or gas generated therefrom is absolutely
prohibited.

Failure to observe these rules is as liable to endanger life as property.

To secure the largest measure of safety to life and property, the following
rules for the installation of acetylene gas machines must be observed.

Class A.--Stationary Automatic Apparatus.

1. FOUNDATIONS.--(a) Must, where practicable, be of brick, stone,
concrete or iron. If necessarily of wood they shall be extra heavy, located in
a dry place and open to the circulation of air.

The ordinary board platform is not satisfactory. Wooden foundations shall
be of heavy planking, joists or timbers, arranged so that the air will circulate
around them so as to form a firm base.

(b) Must be so arranged that the machine will be level and unequal strain
will not be placed on the generator or connexions.

2. LOCATION.--(a) Generators, especially in closely built up districts
should preferably be placed outside of insured buildings in generator houses
constructed and located in compliance with Rule 9.

(b) Generators must be so placed that the operating mechanism will have
room for free and full play and can be adjusted without artificial light. They
must not be subject to interference by children or careless persons, and if
for this purpose further enclosure is necessary, it must be furnished by
means of slatted partitions permitting the free circulation of air.

(c) Generators which from their construction are rendered inoperative
during the process of recharging must be so located that they can be
recharged without the aid of artificial light.

Page 168

(d) Generators must be placed where water will not freeze.

3. ESCAPES OR RELIEF-PIPES.--Each generator must be provided with
an escape or relief-pipe of ample size; no such pipe to be less than 3/4- inch
internal diameter. This pipe shall be substantially installed, without traps,
and so that any condensation will drain back to the generator. It must be
carried to a suitable point outside the building, and terminate in an approved
hood located at least 12 feet above ground and remote from windows.

The hood must be constructed in such a manner that it cannot be obstructed
by rain, snow, ice, insects or birds.

4. CAPACITY.--(a) Must be sufficient to furnish gas continuously for the
maximum lighting period to all lights installed. A lighting period of at least
5 hours shall be provided for in every case.

(b) Generators for conditions of service requiring lighting period of more
than 5 hours must be of sufficient capacity to avoid recharging at night. The
following ratings will usually be found advisable.

(i) For dwellings, and where machines are always used intermittently, the
generator must have a rated capacity equal to the total number of burners
installed.

(ii) For stores, opera houses, theatres, day-run factories, and similar service,
the generator must have a rated capacity of from 30 to 50 per cent, in excess
of the total number of burners installed.

(iii) For saloons and all night or continued service, the generator must have
a rated capacity of from 100 to 200 per cent. in excess of the total number
of burners installed.

(c) A small generator must never be installed to supply a large number of
lights, even though it seems probable that only a few lights will be used at a
time. An overworked generator adds to the cost of producing acetylene gas.

5. CARBIDE CHARGES.--Must be sufficient to furnish gas continuously
for the maximum lighting period to all burners installed. In determining

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charges lump carbide must be estimated as capable of producing 4-1/2
cubic foot of gas to the pound, commercial 1/4-inch carbide 4 cubic feet of
gas to the pound, and burners must be considered as requiring at least 25
per cent. more than their rated consumption of gas.

6. BURNERS.--Burners consuming one-half of a cubic foot of gas per hour
are considered standard in rating generators. Those having a greater or less
capacity will decrease or increase the number of burners allowable in
proportion.

Burners usually consume from 25 to 100 per cent. more than their rated
consumption of gas, depending largely on the working pressure. The so-
called 1/2-foot burner when operated at pressures of from 20- to 25- tenths
inches water column (2 to 2-1/2 inches) is usually used with best economy.

7. PIPING.--(a) Connexions from generators to service-pipes must be made
with right and left thread nipples or long thread nipples with lock nuts. All
forms of unions are prohibited.

(b) Piping must, as far as possible, be arranged so that any moisture will
drain back to the generator. If low points occur of necessity in any piping,
they must be drained through tees into drip cups permanently closed with
screw caps or plugs. No pet-cocks shall be used.

(c) A valve and by-pass connexion must be provided from the service-pipe
to the blow-off for removing the gas from the holder in case it should be
necessary to do so.

(d) The schedule of pipe sizes for piping from generators to burners should
conform to that commonly used for ordinary gas, but in no case must the
feeders be smaller than three-eighths inch.

The following schedule is advocated:

3/8 inch pipe, 26 feet, three burners.
1/2 inch pipe, 30 feet, six burners.
3/4 inch pipe, 50 feet, twenty burners.
1 inch pipe, 70 feet, thirty-five burners.

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1-1/4 inch pipe, 100 feet, sixty burners.
1-1/2 inch pipe, 150 feet, one hundred burners.
2 inch pipe, 200 feet, two hundred burners.
2-1/2 inch pipe, 300 feet, three hundred burners.
3 inch pipe, 450 feet, four hundred and fifty burners,
3-1/2 inch pipe, 500 feet, six hundred burners.
4 inch pipe, 600 feet, seven hundred and fifty burners.

(e) Machines of the carbide-feed type must not be fitted with continuous
drain connexions leading to sewers, but must discharge into suitable open
receptacles which may have such connections.

(f) Piping must be thoroughly tested both before and after the burners have
been installed. It must not show loss in excess of 2 inches within twelve
hours when subjected to a pressure equal to that of 15 inches of mercury.

(g) Piping and connexions must be installed by persons experienced in the
installation of acetylene apparatus.

8. CARE AND ATTENDANCE.--In the care of generators designed for a
lighting period of more than five hours always clean and recharge the
generating chambers at regular stated intervals, regardless of the number of
burners actually used.

Where generators are not used throughout the entire year always remove all
water and gas and clean thoroughly at the end of the season during which
they are in service.

It is usually necessary to take the bell portion out and invert it so as to allow
all gas to escape. This should never be done in the presence of artificial
light or fire of any kind.

Always observe a regular time, during daylight hours only, for attending to
and charging the apparatus.

In charging the generating chambers of water-feed machines clean all
residuum carefully from the containers and remove it at once from the
building. Separate from the mass any unslacked carbide remaining and
return it to the containers, adding now carbide as required. Be careful never
to fill the containers over the specified mark, as it is important to allow for

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the swelling of the carbide when it comes in contact with water. The proper
action and economy of the machine are dependent on the arrangement and
amount of carbide placed in the generator. Carefully guard against the
escape of gas.

Whenever recharging with carbide always replenish the water-supply.

Never deposit residuum or exhausted material from water-feed machines in
sewer-pipes or near inflammable material.

Always keep water-tanks and water-seals filled with clean water.

Never test the generator or piping for leaks with a flame, and never apply
flame to an outlet from which the burner has been removed.

Never use a lighted match, lamp, candle, lantern or any open light near the
machine.

Failure to observe the above cautions is as liable to endanger life as
property.

9. OUTSIDE GENERATOR HOUSES.--(a) Outside generator houses
should not be located within 5 feet of any opening into, nor shall they open
toward any adjacent building, and must be kept under lock and key.

(b) The dimensions must be no greater than the apparatus requires to allow
convenient room for recharging and inspection of parts. The floor must be
at least 12 inches above grade and the entire structure thoroughly weather-
proof.

(c) Generator houses must be thoroughly ventilated, and any artificial
heating necessary to prevent freezing shall be done by steam or hot-water
systems.

(d) Generator houses must not be used for the storage of calcium carbide
except in accordance with the rules relating to that subject (vide Chapter
II.).

Class B.--Stationary Non-Automatic Apparatus.

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10. FOUNDATIONS.--(a) Must be of brick, stone or concrete.

(b) Must be so arranged that the machine will be level and so that strain will
not be brought upon the connexions.

11. GAS-HOUSES.--(a) Must be constructed entirely of non- combustible
material and must not be lighted by any system of illumination involving
open flames.

(b) Must be heated, where artificial heating is necessary to prevent freezing,
by steam or hot-water systems, the heater to be located in a separate
building, and no open flames to be permitted within generator enclosures.

(c) Must be kept closed and locked excepting during daylight hours.

(d) Must be provided with a permanent and effective system of ventilation
which will be operative at all times, regardless of the periods of operation
of the plant.

12. ESCAPE-PIPES.--Each generator must be provided with a vent-pipe of
ample size, substantially installed, without traps. It must be carried to a
suitable point outside the building and terminate in an approved hood
located at least 12 feet above ground and remote from windows.

The hood must be constructed in such a manner that it cannot be obstructed
by rain, snow, ice, insects or birds.

13. CARE AND MAINTENANCE.--All charging and cleaning of
apparatus, generation of gas and execution of repairs must be done during
daylight hours only, and generators must not be manipulated or in any way
tampered with in the presence of artificial light.

This will require gasholders of a capacity sufficient to supply all lights
installed for the maximum lighting period, without the necessity of
generation of gas at night or by artificial light.

In the operation of generators of the carbide-feed type it is important that
only a limited amount of carbide be fed into a given body of water. An

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allowance of at least one gallon of generating water per pound of carbide
must be made in every case, and when this limit has been reached the
generator should be drained and flushed, and clean water introduced. These
precautions are necessary to avoid over-heating during generation and
accumulation of hard deposits of residuum in the generating chamber.

(Rule 14, referring to the storage of carbide, has been quoted in Chapter II.
(page 19)).

RULES FOR THE CONSTRUCTION OF GENERATORS.

The following Rules are intended to provide only against the more
hazardous defects usually noted in apparatus of this kind. The Rules do not
cover all details of construction nor the proper proportioning of parts, and
devices which comply with these requirements alone are not necessarily
suitable for listing as permissible for use. These points are often only
developed in the examination required before permission is given for
installation.

Class A.--Stationary Apparatus for Isolated Installations.

15. GENERAL RULES. GENERATORS.--(a) Must be made of iron or
steel, and in a manner and of material to insure stability and durability.

(b) Must be automatically regulated and uniform in their action, producing
gas only as immediate consumption demands, and so designed that gas is
generated without producing sufficient heat to cause yellow discoloration of
residuum (which will occur at about 500° F.) or abnormal pressure at any
stage of the process when using carbide of any degree of fineness.

The presence of excessive heat tends to change the chemical character of
the gas and may even cause its ignition, while in machines of the carbide-
feed type, finely divided carbide will produce excessive pressure unless
provision is made to guard against it.

(c) Must be so arranged that during recharging, back flow of gas from the
gasholder will be automatically prevented, or so arranged that it will be

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impossible to charge the apparatus without first closing the supply-pipe to
the gasholder, and to the other generating chambers if several are used.

This is intended to prevent the dangerous escape of gas.

(d) The water or carbide supply to the generating chamber must be so
arranged that gas will be generated long enough in advance of the
exhaustion of the supply already in the gasholder to allow the using of all
lights without exhausting such supply.

This provides for the continuous working of the apparatus under all
conditions of water-feed and carbide charge, and it obviates the extinction
of lights through intermittent action of the machine.

(e) No valves or pet-cocks opening into the room from the gas- holding part
or parts, the draining of which will allow an escape of gas, are permitted,
and condensation from all parts of the apparatus must be automatically
removed without the use of valves or mechanical working parts.

Such valves and pet-cocks are not essential; their presence increases the
possibility of leakage. The automatic removal of condensation from the
apparatus is essential to the safe working of the machine.

U-traps opening into the room from the gas-holding parts must not be used
for removal of condensation. All sealed drip connexions must be so
arranged as to discharge gas to the blow-off when blown out, and the seals
must be self-restoring upon relief of abnormal pressure.

(f) The apparatus must be capable of withstanding fire from outside causes.

Sheet-metal joints must be double-seamed or riveted and thoroughly
sweated with solder. Pipes must be attached to sheet-metal with lock-nuts or
riveted flanges.

This prohibits the use of wood or of joints relying entirely upon solder.

(g) Gauge glasses, the breakage of which would allow the escape of gas,
must not be used.

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(h) The use of mercury seals is prohibited.

Mercury has been found unreliable as a seal in acetylene apparatus.(i)
Combustible oils must not be used in connexion with the apparatus.

(j) The construction must be such that liquid seals shall not become
thickened by the deposit of lime or other foreign matter.

(k) The apparatus must be constructed so that accidental siphoning of water
will be impossible.

(l) Flexible tubing, swing joints, unions, springs, mechanical check-valves,
chains, pulleys, stuffing-boxes and lead or fusible piping must not be used
on acetylene apparatus except where failure of such parts will not vitally
affect the working or safety of the machine.

Floats must not be used excepting in cases where failure will result only in
rendering the machine inoperative.

(m) Every machine must be plainly marked with the maximum number of
lights it is designed to supply, the amount of carbide necessary for a single
charge, the manufacturer's name and the name of the machine.

16. GENERATING CHAMBERS.--(a) Must be constructed of galvanised
iron or steel not less than No. 24 U.S. Standard gauge in thickness for
capacities up to and including 20 gallons, not less than No. 22 U.S.
Standard gauge for capacities between 20 and 75 gallons, and not less than
No. 20 U.S. Standard gauge for capacities in excess of 75 gallons.

(b) Must each be connected with the gasholder in such a manner that they
will, at all times, give open connexion either to the gasholder or to the
blow-off pipe to the outer air.

This prevents dangerous pressure within or the escape of gas from the
generating chamber.

(c) Must be so constructed that not more than 5 pounds of carbide can be
acted upon at once, in machines which apply water in small quantities to the

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carbide.

This tends to reduce the danger of overheating and excessive after-
generation by providing for division of the carbide charges in machines of
this type.

(d) Must be provided with covers having secure fastenings to hold them
properly in place and those relying on a water-seal must be submerged in at
least 12 inches of water. Water-seal chambers for covers depending on a
water-seal must be 1-1/2 inches wide and 15 inches deep, excepting those
depending upon the filling of the seal chambers for the generation of gas,
where 9 inches will be sufficient.

(e) Must be so designed that the residuum will not clog or affect the
working of the machine and can conveniently be handled and removed.

(f) Must be provided with suitable vent connexions to the blow-off pipe so
that residuum may be removed and the generating water replaced without
causing siphoning or introducing air to the gasholder upon recharging.

This applies to machines of the carbide-feed type.

(g) Feed mechanism for machines of the carbide-feed type must be so
designed that the direct fall of carbide from the carbide holder into the
water of the generator is prevented at all positions of the feed mechanisms;
or, when actuated by the rise and fall of a gas-bell, must be so arranged that
the feed-valve will not remain open after the landing of the bell, and so that
the feed valve remains inoperative as long as the filling opening on the
carbide hopper remains open. Feed mechanisms must always be far enough
above the water-level to prevent clogging from the accumulation of damp
lime. For this purpose the distance should be not less than 10 inches.

17. CARBIDE CHAMBERS.--(a) Must be constructed of galvanised iron
or steel not less than No. 24 U.S. Standard gauge in thickness for capacities
up to and including 50 pounds and not less than No. 22 U.S. Standard gauge
for capacities in excess of 50 pounds.

Page 177

(b) Must have sufficient carbide capacity to supply the full number of
burners continuously and automatically during the maximum lighting
period.

This rule removes the necessity of recharging or attending to the machine at
improper hours. Burners almost invariably require more than their rated
consumption of gas, and carbide is not of staple purity, and there should
therefore be an assurance of sufficient quantity to last as long as light is
needed. Another important consideration is that in some establishments
burners are called upon for a much longer period of lighting than in others,
requiring a generator of greater gas-producing capacity. Machines having
several generating chambers must automatically begin generation in each
upon exhaustion of the preceding chamber.

(c) Must be arranged so that the carbide holders or charges may be easily
and entirely removed in case of necessity.

18. GASHOLDERS.--(a) Must be constructed of galvanised iron or steel
not less than No. 24 U.S. Standard gauge in thickness for capacities up to
and including 20 gallons, not less than No. 22 U.S. Standard gauge for
capacities between 20 and 75 gallons, and not less than No. 20 U.S.
Standard gauge for capacities in excess of 75 gallons.

Gas-bells, if used, may be two gauges lighter than holders.

Condensation chambers, if placed under holders, to be of same gauge as
holders.

(b) Must be of sufficient capacity to contain all gas generated after all lights
have been extinguished.

If the holder is too small and blows off frequently after the lights are
extinguished there is a waste of gas. This may suggest improper working of
the apparatus and encourage tampering.

(c) Must, when constructed on the gasometer principle, be so arranged that
when the gas-bell is filled to its maximum with gas at normal pressure its
lip or lower edge will extend at least 9 inches below the inner water-level.

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(d) Must, when constructed on the gasometer principle, have the
dimensions of the tank portion so related to those of the bell that a pressure
of at least 11 inches will be necessary before gas can be forced from the
holder.

(e) The bell portion of a gasholder constructed on the gasometer principle
must be provided with a substantial guide to its upward movement,
preferably in the centre of the holder, carrying a stop acting to chock the
bell 1 inch above the normal blow-off point.

This tends to insure the proper action of the bell and decreases the liability
of escaping gas.

(f) A space of at least three-quarters of an inch must be allowed between the
sides of the tank and the bell.

(g) All water-seals must be so arranged that the water-level may be readily
seen and maintained.

19. WATER-SUPPLY.--(a) The supply of water to the generator for
generating purposes must not be taken from the water-seal of any gasholder
constructed on the gasometer principle, unless the feed mechanism is so
arranged that the water-seals provided for in Rules 18, (c), (d), and (e) may
be retained under all conditions. This provides for the proper level of water
in the gasholder.

(b) In cases where machines of the carbide-feed type are supplied with
water from city water-mains or house-pipes, the pipe connexion must
discharge into the regularly provided filling trap on the generator and not
through a separate continuous connexion leading into the generating
chamber.

This is to prevent the expulsion of explosive mixtures through the filling
trap in refilling.

20. RELIEFS OR SAFETY BLOW-OFFS.--(a) Must in all cases be
provided, and must afford free vent to the outer air for any over- production
of gas, and also afford relief in case of abnormal pressure in the machine.

Page 179

Both the above-mentioned vents may be connected, with the same escape-
pipe.

(b) Must be of at least 3/4-inch internal diameter and be provided with
suitable means for connecting to the pipe loading outside of the building.

(c) Must be constructed without valves or other mechanical working parts.

(d) Apparatus requiring pressure regulators must be provided with an
additional approved safety blow-off attachment located between the
pressure regulator and the service-pipes and discharging to the outer air.

This is intended to prevent the possibility of undue pressure in the service-
pipes due to failure of the pressure regulator.

21. PRESSURES.--(a) The working pressure at the generator must not vary
more than ten-tenths (1) inch water column under all conditions of carbide
charge and feed, and between the limits of no load and 50 per cent.
overload.

(b) Apparatus not requiring pressure regulators must be so arranged that the
gas pressure cannot exceed sixty-tenths (6) inches water column.

This requires the use of the pressure relief provided for in Rule No. 20 (a).

(c) Apparatus requiring pressure regulators must be so arranged that the gas
pressure cannot exceed three pounds to the square inch.

The pressure limit of 3 pounds is taken since that is the pressure
corresponding to a water column about 6 feet high, which is about, the limit
in point of convenience for water-sealed reliefs.

22. AIR MIXTURES.--Generators must be so arranged as to contain the
minimum amount of air when first started or recharged, and no device or
attachment facilitating or permitting mixture of air with the gas prior to
consumption, except at the burners, shall be allowed.

Owing to the explosive properties of acetylene mixed with air, machines
must be so designed that such mixtures are impossible.

Page 180

23. PURIFIERS.--(a) Must be constructed of galvanised iron or steel not
less than No. 24 U.S. Standard gauge in thickness.

(b) Where installed, purifiers must conform to the general rules for the
construction of other acetylene apparatus and allow the free passage of gas.

(c) Purifiers must contain no carbide for drying purposes.

(d) Purifiers must be located inside of gasholders, or, where necessarily
outside, must have no hand-holes which can be opened without first
shutting off the gas-supply.

24. PRESSURE REGULATORS.--(a) Must conform to the rules for the
construction of other acetylene apparatus so far as they apply and must not
be subject to sticking or clogging.

(b) Must be capable of maintaining a uniform pressure, not varying more
than four-tenths inch water column, at any load within their rating.

(c) Must be installed between valves in such a manner as to facilitate
inspection and repairs.

Class B.--Stationary Apparatus for Central Station Service.

Generators of over 300 lights capacity for central station service are not
required to be automatic in operation. Generators of less than 300 lights
capacity must be automatic in operation and must comply in every respect
with the requirements of Class A.

25. GENERAL RULES. GENERATORS.--(a) Must be substantially
constructed of iron or steel and be protected against depreciation by an
effective and durable preventive of corrosion.

Galvanising is strongly recommended as a protection against oxidation, and
it may to advantage be reinforced by a thorough coating of asphaltum or
similar material.

(b) Must contain no copper or alloy of copper in contact with acetylene,
excepting in valves.

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(c) Must be so arranged that generation will take place without overheating;
temperatures in excess of 500° F. to be considered excessive.

(d) Must be provided with means for automatic removal of condensation
from gas passages.

(e) Must be provided with suitable protection against freezing of any water
contained in the apparatus.

No salt or other corrosive chemical is permissible as a protection against
freezing.

(f) Must in general comply with the requirements governing the
construction of apparatus for isolated installations so far as they are
applicable.

(g) Must be so arranged as to insure correct procedure in recharging and
cleaning.

(h) Generators of the carbide-feed type must be provided with some form of
approved measuring device to enable the attendant to determine when the
maximum allowable quantity of carbide has been fed into the generating
chamber.

In the operation of generators of this type an allowance of at least 1 gallon
of clean generating water per pound of carbide should be made, and the
generator should be cleaned after slaking of every full charge. Where lump
carbide is used the lumps may become embedded in the residuum, if the
latter is allowed to accumulate at the bottom of the generating chamber,
causing overheating from slow and restricted generation, and rendering the
mass more liable to form a hard deposit and bring severe stresses upon the
walls of the generator by slow expansion.

26. GENERATING CHAMBERS.--(a) Must each be connected with the
gasholder in such a manner that they will, at all times, give open connexion
either to the gasholder or to the blow-off pipe into the outer air.

Page 182

(b) Must be so arranged as to guard against appreciable escape of gas to the
room at any time during the introduction of the charges.

(c) Must be so designed that the residuum will not clog or affect the
operation of the machine and can conveniently be handled and removed.

(d) Must be so arranged that during the process of cleaning and recharging
the back-flow of gas from the gasholder or other generating chambers will
be automatically prevented.

27. GASHOLDERS.--(a) Must be of sufficient capacity to contain at least 4
cubic feet of gas per 1/2-foot burner of the rating. This is to provide for the
requisite lighting period without the necessity of making gas at night,
allowance being made for the enlargement of burners caused by the use of
cleaners.

(b) Must be provided with suitable guides to direct the movement of the bell
throughout its entire travel.

28. PRESSURE RELIEFS.--Must in all cases be provided, and must be so
arranged as to prevent pressure in excess of 100-tenths (10) inches water
column in the mains.

29. PRESSURES.--Gasholders must be adjusted to maintain a pressure of
approximately 25-tenths (2.5) inches water column in the mains.

Page 183

CHAPTER V
THE TREATMENT OF ACETYLENE AFTER
GENERATION

IMPURITIES IN CALCIUM CARBIDE.--The calcium carbide
manufactured at the present time, even when of the best quality
commercially obtainable, is by no means a chemically pure substance; it
contains a large number of foreign bodies, some of which evolve gas on
treatment with water. To a considerable extent this statement will probably
always remain true in the future; for in order to make absolutely pure
carbide it would be necessary for the manufacturer to obtain and employ
perfectly pure lime, carbon, and electrodes in an electric furnace which did
not suffer attack during the passage of a powerful current, or he would have
to devise some process for simultaneously or subsequently removing from
his carbide those impurities which were derived from his impure raw
materials or from the walls of his furnace--and either of these processes
would increase the cost of the finished article to a degree that could hardly
be borne. Beside the impurities thus inevitably arising from the calcium
carbide decomposed, however, other impurities may be added to acetylene
by the action of a badly designed generator or one working on a wrong
system of construction; and therefore it may be said at once that the crude
gas coming from the generating plant is seldom fit for immediate
consumption, while if it be required for the illumination of occupied rooms,
it must invariably be submitted to a rigorous method of chemical
purification.

IMPURITIES OF ACETYLENE.--Combining together what may be
termed the carbide impurities and the generator impurities in crude
acetylene, the foreign bodies are partly gaseous, partly liquid, and partly
solid. They may render the gas dangerous from the point of view of possible
explosions; they, or the products derived from them on combustion, may be
harmful to health if inspired, injurious to the fittings and decorations of
rooms, objectionable at the burner orifices by determining, or assisting in,

Page 184

the formation of solid growths which distort the flame and so reduce its
illuminating power; they may give trouble in the pipes by condensing from
the state of vapour in bends and dips, or by depositing, if they are already
solid, in angles, &c., and so causing stoppages; or they may be merely
harmful economically by acting as diluents to the acetylene and, by having
little or no illuminating value of themselves, causing the gas to emit less
light than it should per unit of volume consumed, more particularly, of
course, when the acetylene is not burnt under the mantle. Also, not being
acetylene, or isomeric therewith, they require, even if they are combustible,
a different proportion of oxygen for their perfect combustion; and a good
acetylene jet is only calculated to attract precisely that quantity of air to the
flame which a gas having the constitution C_2H_2 demands. It will be
apparent without argument that a proper system of purification is one that is
competent to remove the carbide impurities from acetylene, so far as that
removal is desirable or necessary; it should not be called upon to extract the
generator impurities, because the proper way of dealing with them is, to the
utmost possible extent, to prevent their formation. The sole exception to this
rule is that of water-vapour, which invariably accompanies the best
acetylene, and must be partially removed as soon as convenient. Vapour of
water almost always accompanies acetylene from the generator, even when
the apparatus does not belong to those systems of working where liquid
water is in excess, this being due to the fact that in a generator where the
carbide is in excess the temperature tends to rise until part of the water is
vapourised and carried out of the decomposing chamber before it has an
opportunity of reacting with the excess of carbide. The issuing gas is
therefore more or less hot, and it usually comes from the generating
chamber saturated with vapour, the quantity needed so to saturate it rising
as the temperature of the gas increases. Practically speaking, there is little
objection to the presence of water-vapour in acetylene beyond the fear of
deposition of liquid in the pipes, which may accumulate till they are
partially or completely choked, and may even freeze and burst them in very
severe weather. Where the chemical purifiers, too, contain a solid material
which accidentally or intentionally acts as a drier by removing moisture
from the acetylene, it is a waste of such comparatively expensive material
to allow gas to enter the purifier wetter than need be.

Page 185

EXTRACTION OF MOISTURE.--In all large plants the extraction of the
moisture may take place in two stages. Immediately after the generator, and
before the washer if the generator requires such an apparatus to follow it, a
condenser is placed. Here the gas is made to travel somewhat slowly
through one or more pipes surrounded with cold air or water, or is made to
travel through a space containing pipes in which cold water is circulating,
the precise method of constructing the condenser being perfectly immaterial
so long as the escaping gas has a temperature not appreciably exceeding
that of the atmosphere. So cooled, however, the gas still contains much
water-vapour, for it remains saturated therewith at the temperature to which
it is reduced, and by the inevitable law of physics a further fall in
temperature will be followed by a further deposition of liquid water from
the acetylene. Manifestly, if the installation is so arranged that the gas can at
no part of the service and on no occasion fall to a lower temperature than
that at which it issues from the condenser, the removal of moisture as
effected by such a condenser will be sufficient for all practical purposes; but
at least in all large plants where a considerable length of main is exposed to
the air, a more complete moisture extractor must be added to the plant, or
water will be deposited in the pipes every cold night in the winter. It is,
however, useless to put a chemical drier, or one more searching in its action
than a water-cooled condenser, at so early a position in the acetylene plant,
because the gas will be subsequently stored in a water- sealed holder, where
it will most probably once again be saturated with moisture from the seal.
When such generators are adopted as require to have a specific washer
placed after them in order to remove the water- soluble impurities, e.g.,
those in which the gas does not actually bubble through a considerable
quantity of liquid in the generating chamber itself, it is doubtful whether a
separate condenser is altogether necessary, because, as the water in the
washer can easily be kept at the atmospheric temperature (by means of
water circulating in pipes or otherwise), the gas will be brought to the
atmospheric temperature in the washer, and at that temperature it cannot
carry with it more than a certain fixed proportion of moisture. The notion of
partially drying a gas by causing it to pass through water may appear
paradoxical, but a comprehension of physical laws will show that it is
possible, and will prove efficient in practice, when due attention is given to
the facts that the gas entering the washer is hot, and that it is subsequently
to be stored over water in a holder.

Page 186

GENERATOR IMPURITIES.--The generator impurities present in the
crudest acetylene consist of oxygen and nitrogen, i.e., the main constituents
of air, the various gaseous, liquid, and semi-solid bodies described in
Chapter II., which are produced by the polymerising and decomposing
action of heat upon the carbide, water, and acetylene in the apparatus, and,
whenever the carbide is in excess in the generator, some lime in the form of
a very fine dust. In all types of water-to-carbide plant, and in some
automatic carbide-feed apparatus, the carbide chamber must be
disconnected and opened each time a fresh charge has to be inserted; and
since only about one-third of the space in the container can be filled with
carbide, the remaining two-thirds are left full of air. It is easy to imagine
that the carbide container of a small generator might be so large, or loaded
with so small a quantity of carbide, or that the apparatus might in other
respects be so badly designed, that the gas evolved might contain a
sufficient proportion of air to render it liable to explode in presence of a
naked light, or of a temperature superior to its inflaming-point. Were a cock,
however, which should have been shut, to be carelessly left open, an escape
of gas from, rather than an introduction of air into, the apparatus would
follow, because the pressure in the generator is above that of the
atmosphere. As is well known, roughly four-fifths by volume of the air
consist of nitrogen, which is non-inflammable and accordingly devoid of
danger- conferring properties; but in all flames the presence of nitrogen is
harmful by absorbing much of the heat liberated, thus lowering the
temperature of that flame, and reducing its illuminating power far more
seriously. On the other hand, a certain quantity of air in acetylene helps to
prevent burner troubles by acting as a mere diluent (albeit an inferior one to
methane or marsh-gas), and therefore it has been proposed intentionally to
add air to the gas before consumption, such a process being in regular use
on the large scale in some places abroad. As Eitner has shown (Chapter VI.)
that in a 3/4-inch pipe acetylene ceases to be explosive when mixed with
less than 47.7 per cent. of air, an amount of, say, 40 per cent. or less may in
theory be safely added to acetylene; but in practice the amount of air added,
if any, would have to be much smaller, because the upper limit of
explosibility of acetylene-air mixtures is not rigidly fixed, varying from
about 50 per cent. of air when the mixture is in a small vessel, and fired
electrically to about 25 per cent. of air in a large vessel approached with a
flame. Moreover, safely to prepare such mixtures, after the proportion of air

Page 187

had been decided upon, would require the employment of some additional
perfectly trustworthy automatic mechanism to the plant to draw into the
apparatus a quantity of air strictly in accordance with the volume of
acetylene made --a pair of meters geared together, one for the gas, the other
for the air--and this would introduce extra complexity and extra expense.
On the whole the idea cannot be recommended, and the action of the British
Home Office in prohibiting the use of all such mixtures except those
unavoidably produced in otherwise good generators, or in burners of the
ordinary injector type, is perfectly justifiable. The derivation and effect of
the other gaseous and liquid generator impurities in acetylene were
described in Chapter II. Besides these, very hot gas has been found to
contain notable amounts of hydrogen and carbon monoxide, both of which
burn with non-luminous flames. The most plausible explanation of their
origin has been given by Lewes, who suggests that they may be formed by
the action of water-vapour upon very hot carbide or upon carbon separated
therefrom as the result of previous dissociation among the gases present; the
steam and the carbon reacting together at a temperature of 500° C. or
thereabouts in a manner resembling that of the production of water-gas. The
last generator impurity is lime dust, which is calcium oxide or hydroxide
carried forward by the stream of gas in a state of extremely fine
subdivision, and is liable to be produced whenever water acts rapidly upon
an excess of calcium carbide. This lime occasionally appears in the
alternative form of a froth in the pipes leading directly from the generating
chamber; for some types of carbide-to-water apparatus, decomposing
certain kinds of carbide, foam persistently when the liquid in them becomes
saturated with lime, and this foam or froth is remarkably difficult to break
up.

FILTERS.--It has just been stated that the purifying system added to an
acetylene installation should not be called upon to remove these generator
impurities; because their appearance in quantity indicates a faulty generator,
which should be replaced by one of better action. On the contrary, with the
exception of the gases which are permanent at atmospheric temperature--
hydrogen, carbon monoxide, nitrogen, and oxygen-- and which, once
produced, must remain in the acetylene (lowering its illuminating value, but
giving no further trouble), extraction of these generator impurities is quite
simple. The dust or froth of lime will be removed in the washer where the

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acetylene bubbles through water--the dust itself can be extracted by merely
filtering the gas through cotton-wool, felt, or the like. The least volatile
liquid impurities will be removed partly in the condenser, partly in the
washer, and partly by the mechanical dry-scrubbing action of the solid
purifying material in the chemical purifier. To some extent the more volatile
liquid bodies will be removed similarly; but a complete extraction of them
demands the employment of some special washing apparatus in which the
crude acetylene is compelled to bubble (in finely divided streams) through a
layer of some non-volatile oil, heavy mineral lubricating oil, &c.; for
though soluble in such oil, the liquid impurities are not soluble in, nor do
they mix with, water; and since they are held in the acetylene as vapours, a
simple passage through water, or through water-cooled pipes, does not
suffice for their recovery. It will be seen that a sufficient removal of these
generator impurities need throw no appreciable extra labour upon the
consumer of acetylene, for he can readily select a type of generator in
which their production is reduced to a minimum; while a cotton-wool or
coke filter for the gas, a water washer, which is always useful in the plant if
only employed as a non-return valve between the generator and the holder,
and the indispensable chemical purifiers, will take out of the acetylene all
the remaining generator impurities which need, and can, be extracted.

CARBIDE IMPURITIES.--Neglecting very minute amounts of carbon
monoxide and hydrogen (which may perhaps come from cavities in the
calcium carbide itself), as being utterly insignificant from the practical point
of view, the carbide impurities of the gas fall into four main categories:
those containing phosphorus, those containing sulphur, those containing
silicon, and those containing gaseous ammonia. The phosphorus in the gas
comes from calcium phosphide in the calcium carbide, which is attacked by
water, and yields phosphoretted hydrogen (or phosphine, as it will be
termed hereafter). The calcium phosphide, in its turn, is produced in the
electric furnace by the action of the coke upon the phosphorus in phosphatic
lime--all commercially procurable lime and some varieties of coke (or
charcoal) containing phosphates to a larger or smaller extent. The sulphur in
the gas comes from aluminium sulphide in the carbide, which is produced
in the electric furnace by the interaction of impurities containing aluminium
and sulphur (clay-like bodies, &c.) present in the lime and coke; this
aluminium sulphide is attacked by water and yields sulphuretted hydrogen.

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Even in the absence of aluminium compounds, sulphuretted hydrogen may
be found in the gases of an acetylene generator; here it probably arises from
calcium sulphide, for although the latter is not decomposed by water, it
gradually changes in water into calcium sulphydrate, which appears to
suffer decomposition. When it exists in the gas the silicon is derived from
certain silicides in the carbide; but this impurity will be dealt with by itself
in a later paragraph. The ammonia arises from the action of the water upon
magnesium, aluminium, or possibly calcium nitride in the calcium carbide,
which are bodies also produced in the electric furnace or as the carbide is
cooling. In the gas itself the ammonia exists as such; the phosphorus exists
mainly as phosphine, partly as certain organic compounds containing
phosphorus, the exact chemical nature of which has not yet been fully
ascertained; the sulphur exists partly as sulphuretted hydrogen and partly as
organic compounds analogous, in all probability, to those of phosphorus,
among which Caro has found oil of mustard, and certain bodies that he
regards as mercaptans. [Footnote: It will be convenient to borrow the phrase
used in the coal-gas industry, calling the compounds of phosphorus other
than phosphine "phosphorus compounds," and the compounds of sulphur
other than sulphuretted hydrogen "sulphur compounds." The "sulphur
compounds" of coal-gas, however, consist mainly of carbon bisulphide,
which is certainly not the chief "sulphur compound" in acetylene, even if
present to any appreciable extent.] The precise way in which these organic
bodies are formed from the phosphides and sulphides of calcium carbide is
not thoroughly understood; but the system of generation employed, and the
temperature obtaining in the apparatus, have much to do with their
production; for the proportion of the total phosphorus and sulphur found in
the crude gas which exists as "compounds" tends to be greater as the
generating plant yields a higher temperature. It should be noted that
ammonia and sulphuretted hydrogen have one property in common which
sharply distinguishes them from the sulphur "compounds," and from all the
phosphorus compounds, including phosphine. Ammonia and sulphuretted
hydrogen are both very soluble in water, the latter more particularly in the
lime-water of an active acetylene generator; while all the other bodies
referred to are completely insoluble. It follows, therefore, that a proper
washing of the crude gas in water should suffice to remove all the ammonia
and sulphuretted hydrogen from the acetylene; and as a matter of fact those
generators in which the gas is evolved in presence of a large excess of

Page 190

water, and in which it has to bubble through such water, yield an acetylene
practically free from ammonia, and containing nearly all the sulphur which
it does contain in the state of "compounds." It must also be remembered that
chemical processes which are perfectly suited to the extraction of
sulphuretted hydrogen and phosphine are not necessarily adapted for the
removal of the other phosphorus and sulphur compounds.

WASHERS.--In designing a washer for the extraction of ammonia and
sulphuretted hydrogen it is necessary to see that the gas is brought into most
intimate contact with the liquid, while yet no more pressure than can
possibly be avoided is lost. Subdivision of the gas stream may be effected
by fitting the mouth of the inlet-pipe with a rose having a large number of
very small holes some appreciable distance apart, or by bending the pipe to
a horizontal position and drilling it on its upper surface with numbers of
small holes. Another method is to force the gas to travel under a series of
partitions extending just below the water- level, forming the lower edges of
those partitions either perfectly horizontal or with small notches like the
teeth of a saw. One volume of pure water only absorbs about three volumes
of sulphuretted hydrogen at atmospheric temperatures, but takes up some
600 volumes of gaseous ammonia; and as ammonia always accompanies
the sulphuretted hydrogen, the latter may be said to be absorbed in the
washer by a solution of ammonia, a liquid in which sulphuretted hydrogen
is much more soluble. Therefore, since water only dissolves about an equal
volume of acetylene, the liquid in the washer will continue to extract
ammonia and sulphuretted hydrogen long after it is saturated with the
hydrocarbon. For this reason, i.e., to avoid waste of acetylene by dissolution
in the clean water of the washer, the plan is sometimes adopted of
introducing water to the generator through the washer, so that practically
the carbide is always attacked by a liquid saturated with acetylene. Provided
the liquid in the generator does not become seriously heated, there is no
objection to this arrangement; but if the water is heated strongly in the
generator it loses much or all of its solvent properties, and the impurities
may be driven back again into the washer. Clearly if the waste lime of the
generator occurs as a dry or damp powder, the plan mentioned is not to be
recommended; but when the waste lime is a thin cream--water being in
large excess--it may be adopted. If the generator produces lime dust among
the gas, and if the acetylene enters the washer through minute holes, a

Page 191

mechanical filter to remove the dust must be inserted between the generator
and the washer, or the orifices of the leading pipe will be choked. Whenever
a water-cooled condenser is employed after the generator, in which the gas
does not come in contact with the water, that liquid may always be used to
charge the generator. For compactness and simplicity of parts the water of
the holder seal is occasionally used as the washing liquid, but unless the
liquid of the seal is constantly renewed it will thus become offensive,
especially if the holder is under cover, and it will also act corrosively upon
the metal of the tank and bell. The water-soluble impurities in acetylene will
not be removed completely by merely standing over the holder seal for a
short time, and it is not good practice to pass unnecessarily impure gas into
a holder. [Footnote: This is not a contradiction of what has been said in
Chapter III. about the relative position of holder and chemical purifiers,
because reference is now being made to ammonia and sulphuretted
hydrogen only.]

HARMFULNESS OF IMPURITIES.--The reasons why the carbide
impurities must be removed from acetylene before it is burned have now to
be explained. From the strictly chemical point of view there are three
compounds of phosphorus, all termed phosphoretted hydrogen or
phosphine: a gas, PH_3; a liquid, P_2H_4; and a solid, P_4H_2. The liquid
is spontaneously inflammable in presence of air; that is to say, it catches fire
of itself without the assistance of spark or flame immediately it comes in
contact with atmospheric oxygen; being very volatile, it is easily carried as
vapour by any permanent gas. The gaseous phosphine is not actually
spontaneously inflammable at temperatures below 100° C.; but it oxidises
so rapidly in air, even when somewhat diluted, that the temperature may
quickly rise to the point of inflammation. In the earliest days of the
acetylene industry, directly it was recognised that phosphine always
accompanies crude acetylene from the generator, it was believed that unless
the proportion were strictly limited by decomposing only a carbide
practically free from phosphides, the crude acetylene might exhibit
spontaneously inflammable properties. Lewes, indeed, has found that a
sample of carbide containing 1 per cent of calcium phosphide gave
(probably by local decomposition--the bulk of the phosphide suffering
attack first) a spontaneously inflammable gas; but when examining
specimens of commercial carbide the highest amount of phosphine he

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discovered in the acetylene was 2.3 per cent, and this gas was not capable
of self-inflammation. According to Bullier, however, acetylene must contain
80 per cent of phosphine to render it spontaneously inflammable. Berdenich
has reported a case of a parcel of carbide which yielded on the average 5.1
cubic foot of acetylene per lb., producing gas which contained only 0.398
gramme of phosphorus in the form of phosphine per cubic metre (or 0.028
per cent. of phosphine) and was spontaneously inflammable. But on
examination the carbide in question was found to be very irregular in
composition, and some lumps produced acetylene containing a very high
proportion of phosphorus and silicon compounds. No doubt the
spontaneous inflammability was due to the exceptional richness of these
lumps in phosphorus. As manufactured at the present day, calcium carbide
ordinarily never contains an amount of phosphide sufficient to render the
gas dangerous on the score of spontaneous inflammability; but should
inferior material ever be put on the markets, this danger might have to be
guarded against by submitting the gas evolved from it to chemical analysis.
Another risk has been suggested as attending the use of acetylene
contaminated with phosphine (and to a minor degree with sulphuretted
hydrogen), viz., that being highly toxic, as they undoubtedly are, the gas
containing them might be extremely dangerous to breathe if it escaped from
the service, or from a portable lamp, unconsumed. Anticipating what will be
said in a later paragraph, the worst kind of calcium carbide now
manufactured will not yield a gas containing more than 0.1 per cent. by
volume of sulphuretted hydrogen and 0.05 per cent. of phosphine.
According to Haldane, air containing 0.07 per cent. of sulphuretted
hydrogen produces fatal results on man if it is breathed for some hours,
while an amount of 0.2 per cent. is fatal in 1- 1/2 minutes. Similar figures
for phosphine cannot be given, because poisoning therewith is very rare or
quite unknown: the cases of "phossy- jaw" in match factories being caused
either by actual contact with yellow phosphorus or by inhalation of its
vapour in the elemental state. However, assuming phosphine to be twice as
toxic as sulphuretted hydrogen, its effect in crude acetylene of the above-
mentioned composition will be equal to that of the sulphuretted hydrogen,
so that in the present connexion the gas may be said to be equally toxic with
a sample of air containing 0.2 per cent. of sulphuretted hydrogen, which
kills in less than two minutes. But this refers only to crude acetylene
undiluted with air; and being a hydrocarbon--being in fact neither oxygen

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nor common air--acetylene is irrespirable of itself though largely devoid of
specific toxic action. Numerous investigations have been made of the
amount of acetylene (apart from its impurities) which can be breathed in
safety; but although these point to a probable recovery after a fairly long-
continued respiration of an atmosphere charged with 30 per cent. of
acetylene, the figure is not trustworthy, because toxicological experiments
upon animals seldom agree with similar tests upon man. If crude acetylene
were diluted with a sufficient proportion of air to remove its suffocating
qualities, the percentage of specifically toxic ingredients would be reduced
to a point where their action might be neglected; and short of such dilution
the acetylene itself would in all probability determine pathological effects
long before its impurities could set up symptoms of sulphur and phosphorus
poisoning.

Ammonia is objectionable in acetylene because it corrodes brass fittings
and pipes, and because it is partially converted (to what extent is uncertain)
into nitrous and nitric acids as it passes through the flame. Sulphur is
objectionable in acetylene because it is converted into sulphurous and
sulphuric anhydrides, or their respective acids, as it passes through the
flame. Phosphorus is objectionable because in similar circumstances it
produces phosphoric anhydride and phosphoric acid. Each of these acids is
harmful in an occupied room because they injure the decorations, helping to
rot book-bindings, [Footnote: It is only fair to state that the destruction of
leather bindings is commonly due to traces of sulphuric acid remaining in
the leather from the production employed in preparing it, and is but seldom
caused directly by the products of combustion coming from gas or oil.]
tarnishing "gold-leaf" ornaments, and spoiling the colours of dyed fabrics.
Each is harmful to the human system, sulphuric and phosphoric anhydrides
(SO_3, and P_4O_10) acting as specific irritants to the lungs of persons
predisposed to affections of the bronchial organs. Phosphorus, however, has
a further harmful action: sulphuric anhydride is an invisible gas, but
phosphoric anhydride is a solid body, and is produced as an extremely fine,
light, white voluminous dust which causes a haze, more or less opaque, in
the apartment. [Footnote: Lewes suggests that ammonia in the gas burnt
may assist in the production of this haze, owing to the formation of solid
ammonium salts in the state of line dust.] Immediately it comes in contact
with atmospheric moisture phosphoric anhydride is converted into

Page 194

phosphoric acid, but this also occurs at first as a solid substance. The
solidity and visibility of the phosphoric anhydride and acid are beneficial in
preventing highly impure acetylene being unwittingly burnt in a room; but,
on the other hand, being merely solids in suspension in the air, the
combustion products of phosphorus are not so easily carried away from the
room by the means provided for ventilation as are the products of the
combustion of sulphur. Phosphoric anhydride is also partly deposited in the
solid state at the burner orifices, perhaps actually corroding the steatite jets,
and always assisting in the deposition of carbon from any polymerised
hydrocarbons in the acetylene; thus helping the carbon to block up or distort
those orifices. Whenever the acetylene is to be burnt on the incandescent
system under a mantle of the Welsbach or other type, phosphorus, and
possibly sulphur, become additionally objectionable, and rigorous
extraction is necessary. As is well known, the mantle is composed of the
oxides of certain "rare earths" which owe their practical value to the fact
that they are non-volatile at the temperature of the gas-flame. When a gas
containing phosphorus is burnt beneath such a mantle, the phosphoric
anhydride attacks those oxides, partially converting them into the respective
phosphates, and these bodies are less refractory. A mantle exposed to the
combustion products of crude acetylene soon becomes brittle and begins to
fall to pieces, occasionally showing a yellowish colour when cold. The
actual advantage of burning acetylene on the incandescent system is not yet
thoroughly established-- in this country at all events; but it is clear that the
process will not exhibit any economy (rather the reverse) unless the plant is
provided with most capable chemical purifiers. Phosphorus, sulphur, and
ammonia are not objectionable in crude acetylene because they confer upon
the gas a nauseous odour. From a well-constructed installation no acetylene
escapes unconsumed: the gas remains wholly within the pipes until it is
burnt, and whatever odour it may have fails to reach the human nostrils. A
house properly piped for acetylene will be no more conspicuous by its
odour than a house properly piped for coal-gas. On the contrary, the fact
that the carbide impurities of acetylene, which, in the absolutely pure state,
is a gas of somewhat faint, hardly disagreeable, odour, do confer upon that
gas a persistent and unpleasant smell, is distinctly advantageous; for, owing
to that odour, a leak in the pipes, an unclosed tap, or a fault in the
generating plant is instantly brought to the consumer's attention. A gas
wholly devoid of odour would be extremely dangerous in a house, and

Page 195

would have to be scented, as is done in the case of non-carburetted water-
gas when it is required for domestic purposes.

AMOUNTS OF IMPURITIES AND SCOPE OF PURIFICATION.--Partly
for the reason which has just been given, and partly on the ground of
expense, a complete removal of the impurities from crude acetylene is not
desirable. All that need be done is to extract sufficient to deprive the gas of
its injurious effects upon lungs, decorations, and burners. As it stands,
however, such a statement is not sufficiently precise to be useful either to
consumers of acetylene or to manufacturers of plant, and some more or less
arbitrary standard must be set up in order to define the composition of
"commercially pure" acetylene, as well as to gauge the efficiency of any
process of purification. In all probability such limit may be reasonably
taken at 0.1 milligramme of either sulphur or phosphorus (calculated as
elementary bodies) per 1 litre of acetylene, i.e., (0.0-1.1 grain per cubic
foot; a quantity which happens to correspond almost exactly with a
percentage by weight of 0.01. Owing to the atomic weights of these
substances, and the very small quantities being considered, the same limit
hardly differs from that of 0.01 per cent. by weight of sulphuretted
hydrogen or of phosphine--it being always recollected that the sulphur and
phosphorus do not necessarily exist in the gas as simple hydrides. Keppeler,
however, has suggested the higher figure of 0.15 milligramme of either
sulphur or phosphorus per litre of acetylene (=0.066 grain per cubic foot)
for the maximum amount of these impurities permissible in purified
acetylene. He adopts this standard on the basis of the results of observations
of the amounts of sulphur and phosphorus present in the gas issuing from a
purifier charged with heratol at the moment when the last layer of the
heratol is beginning to change colour. No limit has been given for the
removal of the ammonia, partly because that impurity can more easily, and
without concomitant disadvantage, be extracted entirely; and partly because
it is usually removed in the washer and not in the true chemical purifier.

According to Lewes, the maximum amount of ammonia found in the
acetylene coming from a dripping generator is 0.95 gramme per litre, while
in carbide-to-water gas it is 0.16 gramme: 417 and 70.2 grains per cubic
foot respectively. Rossel and Landriset have found 4 milligrammes (1.756
grains [Footnote: Milligrammes per litre; grains per cubic foot. It is

Page 196

convenient to remember that since 1 cubic foot of water weighs 62.321 x 16
- 997.14 avoirdupois ounces, grammes per litre are approximately equal to
oz. per cubic foot; and grammes per cubic metre to oz. per 1000 cubic
feet.]) to be the maximum in water-to-carbide gas, and none to occur in
carbide-to-water acetylene. Rossel and Landriset return the minimum
proportion of sulphur, calculated as H_2S, found in the gaseous state in
acetylene when the carbide has not been completely flooded with water at
1.18 milligrammes per litre, or 0.52 grain per cubic foot; and the
corresponding maxima at 1.9 milligrammes, or 0.84 grain. In carbide-to-
water gas, the similar maxima are 0.23 milligramme or 0.1 grain. As
already stated, the highest proportion of phosphine yet found in acetylene is
2.3 per cent. (Lewes), which is equal to 32.2 milligrammes of PH_3 per
litre or 14.13 grains per cubic foot (Polis); but this sample dated from 1897.
Eitner and Keppeler record the minimum proportion of phosphorus,
calculated as PH_3, found in crude acetylene, as 0.45 milligramme per litre,
and the maximum as 0.89 milligramme per litre; in English terms these
figures are 0.2 and 0.4 grain per cubic foot. On an average, however, British
and Continental carbide of the present day may be said to give a gas
containing 0.61 milligramme of phosphorus calculated as PH_3 per litre
and 0.75 milligramme of sulphur calculated as H_2S. In other units these
figures are equal to 0.27 grain of PH_3 and 0.33 grain of H_2S per 1 cubic
foot, or to 0.041 per cent. by volume of PH_3 and 0.052 per cent. of H_2S.
Yields of phosphorus and sulphur much higher than these will be found in
the journals and books, but such analytical data were usually obtained in the
years 1896-99, before the manufacture of calcium carbide had reached its
present degree of systematic control. A commercial specimen of carbide
was seen by one of the authors as late as 1900 which gave an acetylene
containing 1.12 milligramme of elementary sulphur per litre, i.e., 0.096 per
cent, by volume, or 0.102 per cent, by volume of H_2S; but the phosphorus
showed the low figure of 0.36 milligramme per litre (0.031 per cent, of P or
0.034 per cent, of PH_3 by volume).

The British Acetylene Association's regulations relating to carbide of
calcium (vide Chap. XIV.) contain a clause to the effect that "carbide which,
when properly decomposed, yields acetylene containing from all
phosphorus compounds therein more than 0.05 per cent, by volume of
phosphoretted hydrogen, may be refused by the buyer." This limit is

Page 197

equivalent to 0.74 milligramme of phosphorus calculated as PH_3 per litre.
A latitude of 0.01 per cent, is, however, allowed for the analysis, so that the
ultimate limit on which carbide could be rejected is: 0.06 volume per cent.
of PH_3, or 0.89 milligramme of phosphorus per litre.

The existence in appreciable quantity of combined silicon as a normal
impurity in acetylene seems still open to doubt. Calcium carbide frequently
contains notable quantities of iron and other silicides; but although these
bodies are decomposed by acids, yielding hydrogen silicide, or siliciuretted
hydrogen, they are not attacked by plain water. Nevertheless Wolff and
Gerard have found hydrogen silicide in crude acetylene, and Lewes looks
upon it as a common impurity in small amounts. When it occurs, it is
probably derived, as Vigouroux has suggested, from "alloys" of silicon with
calcium, magnesium, and aluminium in the carbide. The metallic
constituents of these substances would naturally be attacked by water,
evolving hydrogen; and the hydrogen, in its nascent state, would probably
unite with the liberated silicon to form hydrogen silicide. Many authorities,
including Keppeler, have virtually denied that silicon compounds exist in
crude acetylene, while the proportion 0.01 per cent. has been given by other
writers as the maximum. Caro, however, has stated that the crude gas
almost invariably contains silicon, sometimes in very small quantities, but
often up to the limit of 0.8 per cent.; the failure of previous investigators to
discover it being due to faulty analytical methods. Caro has seen one
specimen of (bad) carbide which gave a spontaneously inflammable gas
although it contained only traces of phosphine; its inflammability being
caused by 2.1 per cent. of hydrogen silicide. Practically speaking, all the
foregoing remarks made about phosphine apply equally to hydrogen
silicide: it burns to solid silicon oxide (silica) at the burners, is insoluble in
water, and is spontaneously inflammable when alone or only slightly
diluted, but never occurs in good carbide in sufficient proportion to render
the acetylene itself inflammable. According to Caro the silicon may be
present both as hydrogen silicide and as silicon "compounds." A high
temperature in the generator will favour the production of the latter; an
apparatus in which the gas is washed well in lime-water will remove the
bulk of the former. Fraenkel has found that magnesium silicide is not
decomposed by water or an alkaline solution, but that dilute hydrochloric
acid acts upon it and spontaneously inflammable hydrogen silicide results.

Page 198

If it may be assumed that the other silicides in commercial calcium carbide
also behave in this manner it is plain that hydrogen silicide cannot occur in
crude acetylene unless the gas is supposed to be hurried out of the generator
before the alkaline water therein has had time to decompose any traces of
the hydrogen silicide which is produced in the favouring conditions of high
temperature sometimes prevailing. Mauricheau-Beaupré has failed to find
silica in the products of combustion of acetylene from carbide of varying
degrees of purity. He found, however, that a mixture of strong nitric and
hydrochloric acids (aqua regia), if contaminated with traces of phosphoric
acid, dissolved silica from the glass of laboratory vessels. Consequently,
since phosphoric acid results from the phosphine in crude acetylene when
the gas is passed through aqua regia, silica may be found on subsequently
evaporating the latter. But this, silica, he found, was derived from the glass
and not through the oxidation of silicon compounds in the acetylene. It is
possible that some of the earlier observers of the occurrence of silicon
compounds in crude acetylene may have been misled by the solution of
silica from the glass vessels used in their investigations. The improbability
of recognisable quantities of silicon compounds occurring in acetylene in
any ordinary conditions of generation is demonstrated by a recent study by
Fraenkel of the composition of the deposit produced on reflectors exposed
to the products of combustion of a sample of acetylene which afforded a
haze when burnt. The deposit contained 51.07 per cent. of phosphoric acid,
but no silica. The gas itself contained from 0.0672 to 0.0837 per cent. by
volume of phosphine.

PURIFYING MATERIALS.--When acetylene first began to be used as a
domestic illuminant, most generator builders denied that there was any need
for the removal of these carbide impurities from the gas, some going so far
as to assert that their apparatus yielded so much purer an acetylene than
other plant, where purification might be desirable, that an addition of a
special purifier was wholly unnecessary. Later on the more responsible
members of the trade took another view, but they attacked the problem of
purification in a perfectly empirical way, either employing some purely
mechanical scrubber filled with some moist or dry porous medium, or
perhaps with coke or the like wetted with dilute acid, or they simply
borrowed the processes adopted in the purification of coal-gas. At first sight
it might appear that the more simple methods of treating coal-gas should be

Page 199

suitable for acetylene; since the former contains two of the impurities--
sulphuretted hydrogen and ammonia--characteristic of crude acetylene.
After removing the ammonia by washing with water, therefore, it was
proposed to extract the sulphur by passing the acetylene through that variety
of ferric hydroxide (hydrated oxide of iron) which is so serviceable in the
case of coal-gas. The idea, however, was quite unsound: first, because it
altogether ignores the phosphorus, which is the most objectionable impurity
in acetylene, but is not present in coal- gas; secondly, because ferric
hydroxide is used on gasworks to extract in a marketable form the sulphur
which occurs as sulphuretted hydrogen, and true sulphuretted hydrogen
need not exist in well-generated and well- washed acetylene to any
appreciable extent; thirdly, because ferric hydroxide is not employed by
gasmakers to remove sulphur compounds (this is done with lime), being
quite incapable of extracting them, or the analogous sulphur compounds of
crude acetylene.

About the same time three other processes based on somewhat better
chemical knowledge were put forward. Pictet proposed leading the gas
through a strong solution of calcium chloride and then through strong
sulphuric acid, both maintained at a temperature of -20° to -40° C., finally
washing the gas in a solution of some lead salt. Proof that such treatment
would remove phosphorus to a sufficient degree is not altogether
satisfactory; but apart from this the necessity of maintaining such low
temperatures, far below that of the coldest winter's night, renders the idea
wholly inadmissible for all domestic installations. Willgerodt suggested
removing sulphuretted hydrogen by means of potassium hydroxide (caustic
potash), then absorbing the phosphine in bromine water. For many reasons
this process is only practicable in the laboratory. Bergé and Reychler
proposed extracting both sulphuretted hydrogen and phosphine in an acid
solution of mercuric chloride (corrosive sublimate). The poisonousness of
this latter salt, apart from all other objections, rules such a method out.

BLEACHING POWDER.--The next idea, first patented by Smith of
Aberdeen, but fully elaborated by Lunge and Cedercreutz, was to employ
bleaching- powder [Footnote: Bleaching-powder is very usually called
chloride of lime; but owing to the confusion which is constantly arising in
the minds of persons imperfectly acquainted with chemistry between

Page 200

chloride of lime and chloride of calcium--two perfectly distinct bodies--the
less ambiguous expression "bleaching-powder" will be adopted here.] either
in the solid state or as a liquid extract. The essential constituent of
bleaching-powder from the present aspect is calcium hypochlorite, which
readily oxidises sulphuretted hydrogen, and more particularly phosphine,
converting them into sulphuric and phosphoric acids, while the acetylene is
practically unattacked. In simple purifying action the material proved
satisfactory; but since high-grade commercial bleaching-powder contains
some free chlorine, or some is set free from it in the purifier under the
influence of the passing gas, the issuing acetylene was found to contain
chlorine, free or combined; and this, burning eventually to hydrochloric
acid, is hardly less harmful than the original sulphur compounds. Moreover,
a mixture of acetylene, chlorine, and air is liable to catch fire of itself when
exposed to bright sunlight; and therefore the use of a bleaching-powder
purifier, or rather the recharging thereof, was not unattended by danger in
the early days. To overcome these defects, the very natural process was
adopted of diluting the bleaching-powder, such diluent also serving to
increase the porosity of the material. A very unsuitable substance, however,
was selected for the purpose, viz., sawdust, which is hygroscopic organic,
and combustible. Owing to the exothermic chemical action between the
impurities of the acetylene and the bleaching-powder, the purifying mass
became heated; and thus not only were the phenomena found in a bad
generator repeated in the purifying vessel, but in presence of air and light
(as in emptying the purifier), the reaction proceeded so rapidly that the heat
caused inflammation of the sawdust and the gas, at least on one occasion an
actual fire taking place which created much alarm and did some little
damage. For a time, naturally, bleaching-powder was regarded as too
dangerous a material to be used for the purification of crude acetylene; but
it was soon discovered that danger could be avoided by employing the
substance in a proper way.

HERATOL, FRANKOLINE, ACAGINE AND PURATYLENE.--Setting
aside as unworthy of attention certain compositions offered as acetylene
purifying materials whose constitution has not been divulged or whose
action has not been certified by respectable authority, there are now three
principal chemical reagents in regular use. Those are chromic acid, cuprous
chloride (sub- or proto-chloride of copper), and bleaching- powder.

Page 201

Chromic acid is employed in the form of a solution acidified with acetic or
hydrochloric acid, which, in order to obtain the advantages (see below)
attendant upon the use of a solid purifying material, is absorbed in that
highly porous and inert description of silica known as infusorial earth or
"kieselguhr." This substance was first recommended by Ullmann, and is
termed commercially "heratol" As sold it contains somewhere about 136
grammes of chromic acid per kilo. Cuprous chloride is used as a solution in
strong hydrochloric acid mixed with ferric chloride, and similarly absorbed
in kieselguhr. From the name of its proposer, this composition is called
"frankoline." It will be shown in Chapter VI. that the use of metallic copper
in the construction of acetylene apparatus is not permissible or judicious,
because the gas is liable to form therewith an explosive compound known
as copper acetylide; it might seem, therefore, that the employment of a
copper salt for purification courts accident. The objection is not sound,
because the acetylide is not likely to be produced except in the presence of
ammonia; and since frankoline is a highly acid product, the ammonia is
converted into its chloride before any copper acetylide can be produced. As
a special acetylene purifier, bleaching-powder exists in at least two chief
modifications. In one, known as "acagine," it is mixed with 15 per cent. of
lead chromate, and sometimes with about the same quantity of barium
sulphate; the function of the latter being simply that of a diluent, while to
the lead chromate is ascribed by its inventor (Wolff) the power of retaining
any chlorine that may be set free from the bleaching-powder by the
reduction of the chromic acid. The utility of the lead chromate in this
direction has always appeared doubtful; and recently Keppeler has argued
that it can have no effect upon the chlorine, inasmuch as in the spent
purifying material the lead chromate may be found in its original condition
unchanged. The second modification of bleaching-powder is designated
"puratylene," and contains calcium chloride and quick or slaked lime. It is
prepared by evaporating to dryness under diminished pressure solutions of
its three ingredients, whereby the finished material is given a particularly
porous nature.

It will be observed that both heratol and frankoline are powerfully acid,
whence it follows they are capable of extracting any ammonia that may
enter the purifier; but for the same reason they are liable to act corrosively
upon any metallic vessel in which they are placed, and they therefore

Page 202

require to be held in earthenware or enamelled receivers. But since they are
not liquid, the casing of the purifier can be safely constructed of steel or
cast iron. Puratylene also removes ammonia by virtue of the calcium
chloride in it. Acagine would probably pass the ammonia; but this is no real
objection, as the latter can be extracted by a preliminary washing in water.
Heratol changes, somewhat obscurely, in colour as it becomes spent, its
original orange tint, due to the chromic acid, altering to a dirty green,
characteristic of the reduced salts of chromium oxide. Frankoline has been
asserted to be capable of regeneration or revivification, i.e., that when spent
it may be rendered fit for further service by being exposed to the air for a
time, as is done with gas oxide; this, however, may be true to some extent
with the essential constituents of frankoline, but the process is not available
with the commercial solid product. Of all these materials, heratol is the
most complete purifier of acetylene, removing phosphorus and sulphur
most rapidly and thoroughly, and not appreciably diminishing in speed or
efficiency until its chromic acid is practically quite used up. On the other
hand, heratol does act upon pure acetylene to some extent; so that purifiers
containing it should be small in size and frequently recharged. In one of his
experiments Keppeler found that 13 per cent. of the chromic acid in heratol
was wasted by reacting with acetylene. As this waste of chromic acid
involves also a corresponding loss of gas, small purifiers are preferable,
because at any moment they only contain a small quantity of material
capable of attacking the acetylene itself. Frankoline is very efficacious as
regards the phosphorus, but it does not wholly extract the sulphur, leaving,
according to Keppeler, from 0.13 to 0.20 gramme of the latter in every
cubic metre of the gas. It does not attack acetylene itself; and if, owing to its
free hydrochloric acid, it adds any acid vapours to the purified gas, these
vapours may be easily removed by a subsequent passage through a vessel
containing lime or a carbide drier. Both being essentially bleaching-powder,
acagine and puratylene are alike in removing phosphorus to a satisfactory
degree; but they leave some sulphur behind. Acagine evidently attacks
acetylene to a slight extent, as Keppeler has found 0.2 gramme of chlorine
per cubic metre in the issuing gas.

Although some of these materials attack acetylene slightly, and some leave
sulphur in the purified gas, they may be all considered reasonably efficient
from the practical point of view; for the loss of true acetylene is too small to

Page 203

be noticeable, and the quantity of sulphur not extracted too trifling to be
harmful or inconvenient. They may be valued, accordingly, mainly by their
price, proper allowance being made for the quantity of gas purified per unit
weight of substance taken. This quantity of gas must naturally vary with the
proportion of phosphorus and sulphur in the crude acetylene; but on an
average the composition of unpurified gas is what has already been given
above, and so the figures obtained by Keppeler in his investigation of the
subject may be accepted. In the annexed table these are given in two forms:
(1) the number of litres of gas purified by 1 kilogramme of the substance,
(2) the number of cubic feet purified per lb. It should be noted that the
volumes of gas refer to a laboratory degree of purification; in practice they
may all be increased by 10 or possibly 20 per cent.

_________________________________________________
| | | |
| | Litres | Cubic Feet |
| | per Kilogramme. | per Lb. |
|______________|___________________|______________|
| | | |
| Heratol | 5,000 | 80 |
| Frankoline | 9,000 | 144 |
| Puratylene | 10,000 | 160 |
| Acagine | 13,000 | 208 |
|______________|___________________|______________|

Another method of using dry bleaching-powder has been proposed by
Pfeiffer. He suggests incorporating it with a solution of some lead salt, so
that the latter may increase the capacity of the calcium hypochlorite to
remove sulphur. Analytical details as to the efficiency of this process have
not been given. During 1901 and 1902 Bullier and Maquenne patented a
substance made by mixing bleaching-powder with sodium sulphate,
whereby a double decomposition occurs, sodium hypochlorite, which is
equally efficient with calcium hypochlorite as a purifying material, being
produced together with calcium sulphate, which, being identical with
plaster of Paris, sets into a solid mass with the excess of water present, and
is claimed to render the whole more porous. This process seemed open to
objection, because Blagden had shown that a solution of sodium
hypochlorite was not a suitable purifying reagent in practice, since it was
much more liable to add chlorine to the gas than calcium hypochlorite. The

Page 204

question how a solidified modification of sodium hypochlorite would
behave in this respect has been investigated by Keppeler, who found that
the Bullier and Maquenne material imparted more chlorine to the gas which
had traversed it than other hypochlorite purifying agents, and that the partly
foul material was liable to cause violent explosions. About the same time
Rossel and Landriset pointed out that purification might be easily effected
in all generators of the carbide-to-water pattern by adding to the water of
the generator itself a quantity of bleaching-powder equivalent to 5 to 20
grammes for every 1 kilogramme of carbide decomposed, claiming that
owing to the large amount of liquid present, which is usually some 4 litres
per kilogramme of carbide (0.4 gallon per lb.), no nitrogen chloride could
be produced, and that owing to the dissolved lime in the generator, chlorine
could not be added to the gas. The process is characterised by extreme
simplicity, no separate purifier being needed, but it has been found that an
introduction of bleaching-powder in the solid condition is liable to cause an
explosive combination of acetylene and chlorine, while the use of a solution
is attended by certain disadvantages. Granjon has proposed impregnating a
suitable variety of wood charcoal with chlorine, with or without an addition
of bleaching-powder; then grinding the product to powder, and converting it
into a solid porous mass by the aid of cement. The material is claimed to
last longer than ordinary hypochlorite mixtures, and not to add chlorine to
the acetylene.

SUBSIDIARY PURIFYING MATERIALS.--Among minor reagents
suggested as purifying substances for acetylene may be mentioned
potassium permanganate, barium peroxide, potassium bichromate, sodium
plumbate and arsenious oxide. According to Benz the first two do not
remove the sulphuretted hydrogen completely, and oxidise the acetylene to
some extent; while potassium bichromate leaves some sulphur and
phosphorus behind in the gas. Sodium plumbate has been suggested by
Morel, but it is a question whether its action on the impurities would not be
too violent and whether it would be free from action on the acetylene itself.
The use of arsenious oxide dissolved in a strong acid, and the solution
absorbed in pumice or kieselguhr has been protected by G. F. Jaubert. The
phosphine is said to combine with the arsenic to form an insoluble brownish
compound. In 1902 Javal patented a mixture of 1 part of potassium
permanganate, 5 of "sulphuric acid," and 1 of water absorbed in 4 parts of

Page 205

infusorial earth. The acid constantly neutralised by the ammonia of the
crude gas is as constantly replaced by fresh acid formed by the oxidation of
the sulphuretted hydrogen; and this free acid, acting upon the
permanganate, liberates manganese peroxide, which is claimed to destroy
the phosphorus and sulphur compounds present in the crude acetylene.

ÉPURÈNE.--A purifying material to which the name of épurène has been
given has been described, by Mauricheau-Beaupré, as consisting of a
mixture of ferric chloride and ferric oxide in the proportion of 2 molecules,
or 650 parts, of the former with one molecule, or 160 parts, of the latter,
together with a suitable quantity of infusorial earth. In the course of
preparation, however, 0.1 to 0.2 per cent. of mercuric chloride is introduced
into the material. This mercuric chloride is said to form an additive
compound with the phosphine of the crude acetylene, which compound is
decomposed by the ferric chloride, and the mercuric chloride recovered.
The latter therefore is supposed to act only as a carrier of the phosphine to
the ferric chloride and oxide, by which it is oxidised according to the
equation:

8Fe_2Cl_6 + 4Fe_2O_3 + 3PH_3 = 12Fe_2Cl_4 + 3H_3PO_4.

Thus the ultimate products are phosphoric acid and ferrous chloride, which
on exposure to air is oxidised to ferric chloride and oxide. It is said that this
revivification of the fouled or spent épurène takes place in from 20 to 48
hours when it is spread in the open in thin layers, or it may be partially or
wholly revivified in situ by adding a small proportion of air to the crude
acetylene as it enters the purifier. The addition of 1 to 2 per cent. of air,
according to Mauricheau-Beaupré, suffices to double the purifying capacity
of one charge of the material, while a larger proportion would achieve its
continuous revivification. Épurène is said to purify 10,000 to 11,000 litres
of crude acetylene per kilogramme, or, say, 160 to 176 cubic feet per pound,
when the acetylene contains on the average 0.05 per cent, by volume of
phosphine.

For employment in all acetylene installations smaller than those which
serve complete villages, a solid purifying material is preferable to a liquid
one. This is partly due to the extreme difficulty of subdividing a stream of
gas so that it shall pass through a single mass of liquid in small enough

Page 206

bubbles for the impurities to be removed by the time the gas arrives at the
surface. This time cannot be prolonged without increasing the depth of
liquid in the vessel, and the greater the depth of liquid, the more pressure is
consumed in forcing the gas through it. Perfect purification by means of
fluid reagents unattended by too great a consumption of pressure is only to
be effected by a mechanical scrubber such as is used on coal-gas works,
wherein, by the agency of external power, the gas comes in contact with
large numbers of solid surfaces kept constantly wetted; or by the adoption
of a tall tower filled with porous matter or hollow balls over which a
continuous or intermittent stream of the liquid purifying reagent is made to
trickle, and neither of these devices is exactly suited to the requirements of
a domestic acetylene installation. When a solid material having a proper
degree of porosity or aggregation is selected, the stream of gas passing
through it is broken up most thoroughly, and by employing several separate
layers of such material, every portion of the gas is exposed equally to the
action of the chemical reagent by the time the gas emerges from the vessel.
The amount of pressure so consumed is less than that in a liquid purifier
where much fluid is present; but, on the other hand, the loss of pressure is
absolutely constant at all times in a liquid purifier, provided the head of
liquid is maintained at the same point. A badly chosen solid purifying agent
may exhibit excessive pressure absorption as it becomes partly spent. A
solid purifier, moreover, has the advantage that it may simultaneously act as
a drier for the gas; a liquid purifier, in which the fluid is mainly water,
obviously cannot behave in a similar fashion For thorough purification it is
necessary that the gas shall actually stream through the solid material; a
mere passage over its surface is neither efficient nor economical of material.

DISPOSITION OF PURIFYING MATERIAL.--Although much has been
written, and some exaggerated claims made, about the maximum, volume
of acetylene a certain variety of purifying material will treat, little has been
said about the method in which such a material should be employed to
obtain the best results. If 1 lb. of a certain substance will purify 200 cubic
feet of normal crude acetylene, that weight is sufficient to treat the gas
evolved from 40 lb. of carbide; but it will only do so provided it is so
disposed in the purifier that the gas does not pass through it at too high a
speed, and that it is capable of complete exhaustion. In the coal- gas
industry it is usually assumed that four layers of purifying material, each

Page 207

having a superficial area of 1 square foot, are the minimum necessary for
the treatment of 100 cubic feet of gas per hour, irrespective of the nature of
the purifying material and of the impurity it is intended to extract. If there is
any sound basis for this generalization, it should apply equally to the
purification of acetylene, because there is no particular reason to imagine
that the removal of phosphine by a proper substance should occur at an
appreciably different speed from the removal of carbon dioxide,
sulphuretted hydrogen, and carbon bisulphide by lime, ferric oxide, and
sulphided lime respectively, Using the coal gas figures, then, for every 10
cubic feet of acetylene generated per hour, a superficial area of (4 x 144 /
10) 57.6 square inches of purifying material is required. In the course of
Keppeler's research upon different purifying materials it is shown that 400
grammes of heratol, 360 grammes of frankoline, 250 grammes of acagine,
and 230 grammes of puratylene each occupy a space of 500 cubic
centimetres when loosely loaded into a purifying vessel, and from these
data, the following table has been calculated:

__________________________________________________________
| | | | |
| | Weight | Weight | Cubic Inches |
| | per Gallon | per Cubic Foot | Occupied |
| | in Lbs. | in Lbs. | per Lb. |
|_____________|____________|________________|______________|
| | | | |
| Water | 10.0 | 62.321 | 27.73 |
| Heratol | 8.0 | 49.86 | 31.63 |
| Frankoline | 7.2 | 41.87 | 38.21 |
| Acagine | 6.0 | 31.16 | 55.16 |
| Puratylene | 4.6 | 28.67 | 60.28 |
|_____________|____________|________________|______________|

As regards the minimum weight of material required, data have been given
by Pfleger for use with puratylene. He states that 1 Kilogramme of that
substance should be present for every 100 litres of crude acetylene evolved
per hour, 4 kilogrammes being the smallest quantity put into the purifier. In
English units these figures are 1 lb. per 1.5 cubic feet per hour, with 9 lb. as
a minimum, which is competent to treat 1.1 cubic feet of gas per hour. Thus
it appears that for the purification of the gas coming from any generator
evolving up to 14 cubic feet of acetylene per hour a weight of 9 lb of

Page 208

puratylene must be charged into the purifier, which will occupy (60.28 / 9)
542 cubic inches of space; and it must be so spread out as to present a total
superficial area of (4 x 144 x 14 / 100) 80.6 square inches to the passing
gas. It follows, therefore, that the material should be piled to a depth of (542
/ 80.6) 6.7 inches on a support having an area of 80.6 square inches; but
inasmuch as such a depth is somewhat large for a small vessel, and as
several layers are better than one, it would be preferable to spread out these
540 cubic inches of substance on several supports in such a fashion that a
total surface of 80.6 square inches or upwards should be exhibited. These
figures may obviously be manipulated in a variety of ways for the design of
a purifying vessel; but, to give an example, if the ordinary cylindrical shape
be adopted with four circular grids, each having a clear diameter of 8 inches
(i.e., an area of 50.3 square inches), and if the material is loaded to a depth
of 3 inches on each, there would be a total volume of (50.3 x 3 x 4) = 604
cubic inches of puratylene in the vessel, and it would present a total area of
(50.3 x 4) = 201 square inches to the acetylene. At Keppeler's estimation
such an amount of puratylene should weigh roughly 10 lb., and should
suffice for the purification of the gas obtained from 320 lb. of ordinary
carbide; while, applying the coal-gas rule, the total area of 201 square
inches should render such a vessel equal to the purification of acetylene
passing through it at a speed not exceeding (201 / 5.76) = 35 cubic feet per
hour. Remembering that it is minimum area in square inches of purifying
material that must govern the speed at which acetylene may be passed
through a purifier, irrespective probably of the composition of the material;
while it is the weight of material which governs the ultimate capacity of the
vessel in terms of cubic feet of acetylene or pounds of carbide capable of
purification, these data, coupled with Keppeler's efficiency table, afford
means for calculating the dimensions of the purifying vessel to be affixed to
an installation of any desired number of burners. There is but little to say
about the design of the vessel from the mechanical aspect. A circular
horizontal section is more likely to make for thorough exhaustion of the
material. The grids should be capable of being lifted out for cleaning. The
lid may be made tight either by a clamp and rubber or leather washer, or by
a liquid seal. If the purifying material is not hygroscopic, water, calcium
chloride solution, or dilute glycerin may be used for sealing purposes; but if
the material, or any part of it, does absorb water, the liquid in the seal
should be some non-aqueous fluid like lubricating oil. Clamped lids are

Page 209

more suitable for small purifiers, sealed lids for large vessels. Care must be
taken that condensation products cannot collect in the purifying vessel. If a
separate drying material is employed in the same purifier the space it takes
must be considered separately from that needed by the active chemical
reagent. When emptying a foul purifier it should be recollected that the
material may be corrosive, and being saturated with acetylene is likely to
catch fire in presence of a light.

Purifiers charged with heratol are stated, however, to admit of a more rapid
flow of the gas through them than that stated above for puratylene. The
ordinary allowance is 1 lb. of heratol for every cubic foot per hour of
acetylene passing, with a minimum charge of 7 lb. of the material. As the
quantity of material in the purifier is increased, however, the flow of gas per
hour may be proportionately increased, e.g., a purifier charged with 132 lb.
of heratol should purify 144 cubic feet of acetylene per hour.

In the systematic purification of acetylene, the practical question arises as to
how the attendant is to tell when his purifiers approach exhaustion and need
recharging; for if it is undesirable to pass crude gas into the service, it is
equally undesirable to waste so comparatively expensive a material as a
purifying reagent. In Chapter XIV. it will be shown that there are chemical
methods of testing for the presence, or determining the proportion, of
phosphorus and sulphur in acetylene; but these are not suitable for
employment by the ordinary gas-maker. Heil has stated that the purity of the
gas may be judged by an inspection of its atmospheric flame as given by a
Bunsen burner. Pure acetylene gives a perfectly transparent moderately dark
blue flame, which has an inner cone of a pale yellowish green colour; while
the impure gas yields a longer flame of an opaque orange-red tint with a
bluish red inner zone. It should be noted, however, that particles of lime
dust in the gas may cause the atmospheric flame to be reddish or yellowish
(by presence of calcium or sodium) quite apart from ordinary impurities;
and for various other reasons this appearance of the non-luminous flame is
scarcely to be relied upon. The simplest means of ascertaining definitely
whether a purifier is sufficiently active consists in the use of the test-papers
prepared by E. Merck of Darmstadt according to G. Keppeler's prescription.
These papers, cut to a convenient size, are put up in small books from
which they may be torn one at a time. In order to test whether gas is

Page 210

sufficiently purified, one of the papers is moistened with hydrochloric acid
of 10 per cent. strength, and the gas issuing from a pet-cock or burner
orifice is allowed to impinge on the moistened part. The original black or
dark grey colour of the paper is changed to white if the gas contains a
notable amount of impurity, but remains unchanged if the gas is adequately
purified. The paper consists of a specially prepared black porous paper
which has been dipped in a solution of mercuric chloride (corrosive
sublimate) and dried. Moistening the paper with hydrochloric acid provides
in a convenient form for application Bergé's solution for the detection of
phosphine (vide Chapter XIV.). The Keppeler test-papers turn white when
the gas contains either ammonia, phosphine, siliciuretted hydrogen,
sulphuretted hydrogen or organic sulphur compounds, but with carbon
disulphide the change is slow. Thus the paper serves as a test for all the
impurities likely to occur in acetylene. The sensitiveness of the test is such
that gas containing about 0.15 milligramme of sulphur, and the same
amount of phosphorus, per litre (= 0.0655 grain per cubic foot) imparts in
five minutes a distinct white mark to the moistened part of the paper, while
gas containing 0.05 milligramme of sulphur per litre (= 0.022 grain per
cubic foot) gives in two minutes a dull white mark visible only by careful
inspection. If, therefore, a distinct white mark appears on moistened
Keppeler paper when it is exposed for five minutes to a jet of acetylene, the
latter is inadequately purified. If the gas has passed through a purifier, this
test indicates that the material is not efficient, and that the purifier needs
recharging. The moistening of the Keppeler paper with hydrochloric acid
before use is essential, because if not acidified the paper is marked by
acetylene itself. The books of Keppeler papers are put up in a case which
also contains a bottle of acid for moistening them as required and are
obtainable wholesale of E. Merek, 16 Jewry Street, London, E.C., and retail
of the usual dealers in chemicals. If Keppeler's test-papers are not available,
the purifier should be recharged as a matter of routine as soon as a given
quantity of carbide--proportioned to the purifying capacity of the charge of
purifying material--has been used since the last recharging. Thus the
purifier may conveniently contain enough material to purify the gas evolved
from two drums of carbide, in which case it would need recharging when
every second drum of carbide is opened.

Page 211

REGULATIONS AS TO PURIFICATION.--The British Acetylene
Association has issued the following set of regulations as to purifying
material and purifiers for acetylene:

Efficient purifying material and purifiers shall comply with the following
requirements:

(1) The purifying material shall remove phosphorus and sulphur compounds
to a commercially satisfactory degree; i.e., not to a greater degree than will
allow easy detection of escaping gas through its odour.

(2) The purifying material shall not yield any products capable of corroding
the gas-mains or fittings.

(3) The purifying material shall, if possible, be efficient as a drying agent,
but the Association does not consider this an absolute necessity.

(4) The purifying material shall not, under working conditions, be capable
of forming explosive compounds or mixtures. It is understood, naturally,
that this condition does not apply to the unavoidable mixture of acetylene
and air formed when recharging the purifier.

(5) The apparatus containing the purifying material shall be simple in
construction, and capable of being recharged by an inexperienced person
without trouble. It shall be so designed as to bring the gas into proper
contact with the material.

(6) The containers in purifiers shall be made of such materials as are not
dangerously affected by the respective purifying materials used.

(7) No purifier shall be sold without a card of instructions suitable or
hanging up in some convenient place. Such instructions shall be of the most
detailed nature, and shall not presuppose any expert knowledge whatever on
the part of the operator.

Reference also to the abstracts of the official regulations as to acetylene
installations in foreign countries given in Chapter IV. will show that they
contain brief rules as to purifiers.

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DRYING.--It has been stated in Chapter III. that the proper position for the
chemical purifiers of an acetylene plant is after the holder; and they
therefore form the last items in the installation unless a "station" governor
and meter are fitted. It is therefore possible to use them also to remove the
moisture in the gas, if a material hygroscopic in nature is employed to
charge them. This should be true more particularly with puratylene, which
contains a notable proportion of the very hygroscopic body calcium
chloride. If a separate drier is desirable, there are two methods of charging
it. It may be filled either with some hygroscopic substance such as porous
calcium chloride or quicklime in very coarse powder, which retains the
water by combining with it; or the gas may be led through a vessel loaded
with calcium carbide, which will manifestly hold all the moisture, replacing
it by an equivalent quantity of (unpurified) acetylene. The objection is
sometimes urged against this latter method, that it restores to the gas the
nauseous odour and the otherwise harmful impurities it had more or less
completely lost in the purifiers; but as regards the first point, a nauseous
odour is not, as has previously been shown, objectionable in itself, and as
regards the second, the amount of impurities added by a carbide drier, being
strictly limited by the proportion of moisture in the damp gas, is too small
to be noticeable at the burners or elsewhere. As is the case with purification,
absolute removal of moisture is not called for; all that is needed is to extract
so much that the gas shall never reach its saturation-point in the
inaccessible parts of the service during the coldest winter's night. Any
accessible length of main specially exposed to cold may be safeguarded by
itself; being given a steady fall to a certain point (preferably in a frost-free
situation), and there provided with a collecting-box from which the
deposited liquid can be removed periodically with a pump or otherwise.

FILTRATION.--The gas issuing from the purifier or drier is very liable to
hold in suspension fine dust derived from the purifying or drying material
used. It is essential that thin dust should be abstracted before the gas
reaches the burners, otherwise it will choke the orifices and prevent them
functioning properly. Consequently the gas should pass through a sufficient
layer of filtering material after it has traversed the purifying material (and
drier if one is used). This filtering material may be put either as a final layer
in the purifier (or drier), or in a separate vessel known as a filter. Among
filtering materials in common use may be named cotton-wool, fine canvas

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or gauze, felt and asbestos-wool. The gas must be fairly well dried before it
enters the filter, otherwise the latter will become choked with deposited
moisture, and obstruct the passage of the gas.

Having now described the various items which go to form a well-designed
acetylene installation, it may be useful to recapitulate briefly, with the
object of showing the order in which they should be placed. From the
generator the gas passes into a condenser to cool it and to remove any tarry
products and large quantities of water. Next it enters a washing apparatus
filled with water to extract water-soluble impurities. If the generator is of
the carbide-to-water pattern, the condenser may be omitted, and the washer
is only required to retain any lime froth and to act as a water-seal or non-
return valve. If the generator does not wash the gas, the washer must be
large enough to act efficiently as such, and between it and the condenser
should be put a mechanical filter to extract any dust. From the washer the
acetylene travels to the holder. From the holder it passes through one or two
purifiers, and from there travels to the drier and filter. If the holder does not
throw a constant pressure, or if the purifier and drier are liable to cause
irregularities, a governor or pressure regulator must be added after the drier.
The acetylene is then ready to enter the service; but a station meter (the last
item in the plant) is useful as giving a means of detecting any leak in the
delivery-pipes and in checking the make of gas from the amount of carbide
consumed. If the gas is required for the supply of a district, a station meter
becomes quite necessary, because the public lamps will be fed with gas at a
contract rate, and without the meter there would be no control over the
volume of acetylene they consume. Where the gas finally leaves the
generating-house, or where it enters the residence, a full-way stopcock
should be put on the main.

GENERATOR RESIDUES.--According to the type of generator employed
the waste product removed therefrom may vary from a dry or moist powder
to a thin cream or milk of lime. Any waste product which is quite liquid in
its consistency must be completely decomposed and free from particles of
calcium carbide of sensible magnitude; in the case of more solid residues,
the less fluid they are the greater is the improbability (or the less is the
evidence) that the carbide has been wholly spent within the apparatus.
Imperfect decomposition of the carbide inside the generator not only means

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an obvious loss of economy, but its presence among the residues makes a
careful handling of them essential to avoid accident owing to a subsequent
liberation of acetylene in some unsuitable, and perhaps closed, situation. A
residue which is not conspicuously saturated with water must be taken out
of the generator- house into the open air and there flooded with water, being
left in some uncovered receptacle for a sufficient time to ensure all the
acetylene being given off. A residue which is liquid enough to flow should
be run directly from the draw-off cock of the generator through a closed
pipe to the outside; where, if it does not discharge into an open conduit, the
waste-pipe must be trapped, and a ventilating shaft provided so that no gas
can blow back into the generator-house.

DISPOSAL OF RESIDUES.--These residues have now to be disposed of.
In some circumstances they can be put to a useful purpose, as will be
explained in Chapter XII.; otherwise, and always perhaps on the small
scale--certainly always if the generator overheats the gas and yields tar
among the spent lime--they must be thrown into a convenient place. It
should be remembered that although methods of precipitating sewage by
adding lime, or lime water, to it have frequently been used, they have not
proved satisfactory, partly because the sludge so obtained is peculiarly
objectionable in odour, and partly because an excess of lime yields an
effluent containing dissolved lime, which among other disadvantages is
harmful to fish. The plan of running the liquid residues of acetylene
manufacture into any local sewerage system which may be found in the
neighbourhood of the consumer's premises, therefore, is very convenient to
the consumer; but is liable to produce complaints if the sewage is
afterwards treated chemically, or if its effluent is passed untreated into a
highly preserved river; and the same remark applies in a lesser degree if the
residues are run into a private cesspool the liquid contents of which
automatically flow away into a stream. If, however, the cesspool empties
itself of liquid matter by filtration or percolation through earth, there can be
no objection to using it to hold the lime sludge, except in so far as it will
require more frequent emptying. On the whole, perhaps the best method of
disposing of these residues is to run them into some open pit, allowing the
liquid to disappear by evaporation and percolation, finally burying the solid
in some spot where it will be out of the way. When a large carbide-to-water
generator is worked systematically so as to avoid more loss of acetylene by

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solution in the excess of liquid than is absolutely necessary, the liquid
residues coming from it will be collected in some ventilated closed tank
where they can settle quietly. The clear lime-water will then be pumped
back into the generator for further use, and the almost solid sludge will be
ready to be carried to the pit where it is to be buried. Special care must be
taken in disposing of the residues from a generator in which oil is used to
control evolution of gas. Such oil floats on the aqueous liquid; and a very
few drops spread for an incredible distance as an exceedingly thin film,
causing those brilliant rainbow-like colours which are sometimes imagined
to be a sign of decomposing organic matter. The liquid portions of these
residues must be led through a pit fitted with a depending partition
projecting below the level at which the water is constantly maintained; all
the oil then collects on the first side of the partition, only water passing
underneath, and the oil may be withdrawn and thrown away at intervals.

Page 216

CHAPTER VI
THE CHEMICAL AND PHYSICAL PROPERTIES OF
ACETYLENE

It will only be necessary for the purpose of this book to indicate the more
important chemical and physical properties of acetylene, and, in particular,
those which have any bearing on the application of acetylene for lighting
purposes. Moreover, it has been found convenient to discuss fully in other
chapters certain properties of acetylene, and in regard to such properties the
reader is referred to the chapters mentioned.

PHYSICAL PROPERTIES.--Acetylene is a gas at ordinary temperatures,
colourless, and, when pure, having a not unpleasant, so-called "ethereal"
odour. Its density, or specific gravity, referred to air as unity, has been found
experimentally by Leduc to be 0.9056. It is customary to adopt the value
0.91 for calculations into which the density of the gas enters (vide Chapter
VII.). The density of a gas is important not only for the determination of the
size of mains needed to convey it at a given rate of flow under a given
pressure, as explained in Chapter VII., but also because the volume of gas
which will pass through small orifices in a given time depends on its
density. According to Graham's well-known law of the effusion of gases,
the velocity with which a gas effuses varies directly as the square root of the
difference of pressure on the two sides of the opening, and inversely as the
square root of the density of the gas. Hence it follows that the volume of
gas which escapes through a porous pipe, an imperfect joint, or a burner
orifice is, provided the pressure in the gas-pipe is the same, a function of
the square root of the density of the gas. Hence this density has to be taken
into consideration in the construction of burners, i.e., a burner required to
pass a gas of high density must have a larger orifice than one for a gas of
low density, if the rate of flow of gas is to be the same under the same
pressure. This, however, is a question for the burner manufacturers, who
already make special burners for gases of different densities, and it need not
trouble the consumer of acetylene, who should always use burners devised

Page 217

for the consumption of that gas. But the Law of effusion indicates that the
volume of acetylene which can escape from a leaky supply-pipe will be less
than the volume of a gas of lower density, e.g., coal-gas, if the pressure in
the pipe is the same for both. This implies that on an extensive distributing
system, in which for practical reasons leakage is not wholly avoidable, the
loss of gas through leakage will be less for acetylene than for coal-gas,
given the same distributing pressure. If v = the loss of acetylene from a
distributing system and v' = the loss of coal-gas from a similar system
worked at the same pressure, both losses being expressed in volumes (cubic
feet) per hour, and the coal-gas being assumed to have a density of 0.04,
then

(1) (_v_/_v'_) = (0.40 / 0.91)^(1/2) = 0.663

or, _v_ = 0.663_v'_,

which signifies that the loss of acetylene by leakage under the same
conditions of pressure, &c., will be only 0.663 times that of the loss of coal-
gas. In practice, however, the pressures at which the gases are usually sent
through mains are not identical, being greater in the case of acetylene than
in that of coal-gas. Formula (1) therefore requires correction whenever the
pressures are different, and calling the pressure at which the acetylene exists
in the main p, and the corresponding pressure of the coal-gas p', the relative
losses by leakage are--

(2) (_v_/_v'_) = (0.40 / 0.91)^(1/2) x (_p_/_p'_)^(1/2)

_v_ = 0.663_v'_ x (_p_/_p'_)^(1/2)

It will be evident that whenever the value of the fraction (_p_/_p'_)^(1/2), is
less than 1.5, i.e., whenever the pressure of the acetylene does not exceed
double that of the coal-gas present in pipes of given porosity or
unsoundness, the loss of acetylene will be less than that of coal-gas. This is
important, especially in the case of large village acetylene installations,
where after a time it would be impossible to avoid some imperfect joints,
fractured pipes, &c., throughout the extensive distributing mains. The same
loss of gas by leakage would represent a far higher pecuniary value with
acetylene than with coal-gas, because the former must always be more

Page 218

costly per unit of volume than the latter. Hence it is important to recognise
that the rate of leakage, coeteris paribus, is less with acetylene, and it is
also important to observe the economical advantage, at least in terms of gas
or calcium carbide, of sending the acetylene into the mains at as low a
pressure as is compatible with the length of those mains and the character of
the consumers' burners. As follows from what will be said in Chapter VII., a
high initial pressure makes for economy in the prime cost of, and in the
expense of laying, the mains, by enabling the diameter of those mains to be
diminished; but the purchase and erection of the distributing system are
capital expenses, while a constant expenditure upon carbide to meet loss by
leakage falls upon revenue.

The critical temperature of acetylene, i.e., the temperature below which an
abrupt change from the gaseous to the liquid state takes place if the pressure
is sufficiently high, is 37° C., and the critical pressure, i.e., the pressure
under which that change takes place at that temperature, is nearly 68
atmospheres. Below the critical temperature, a lower pressure than this
effects liquefaction of the gas, i.e., at 13.5° C. a pressure of 32.77
atmospheres, at 0° C., 21.53 atmospheres (Ansdell, cf. Chapter XI.). These
data are of comparatively little practical importance, owing to the fact that,
as explained in Chapter XI., liquefied acetylene cannot be safely utilised.

The mean coefficient of expansion of gaseous acetylene between 0° C. and
100° C., is, under constant pressure, 0.003738; under constant volume,
0.003724. This means that, if the pressure is constant, 0.003738 represents
the increase in volume of a given mass of gaseous acetylene when its
temperature is raised one degree (C.), divided by the volume of the same
mass at 0° C. The coefficients of expansion of air are: under constant
pressure, 0.003671; under constant volume, 0.003665; and those of the
simple gases (nitrogen, hydrogen, oxygen) are very nearly the same. Strictly
speaking the table given in Chapter XIV., for facilitating the correction of
the volume of gas measured over water, is not quite correct for acetylene,
owing to the difference in the coefficients of expansion of acetylene and the
simple gases for which the table was drawn up, but practically no
appreciable error can ensue from its use. It is, however, for the correction of
volumes of gases measured at different temperatures to one (normal)
temperature, and, broadly, for determining the change of volume which a

Page 219

given mass of the gas will undergo with change of temperature, that the
coefficient of expansion of a gas becomes an important factor industrially.

Ansdell has found the density of liquid acetylene to range from 0.460 at -7°
C. to 0.364 at +35.8° C., being 0.451 at 0° C. Taking the volume of the
liquid at -7° as unity, it becomes 1.264 at 35.8", and thence Ansdell infers
that the mean coefficient of expansion per degree is 0.00489° for the total
range of pressure." Assuming that the liquid was under the same pressure at
the two temperatures, the coefficient of expansion per degree Centigrade
would be 0.00605, which agrees more nearly with the figure 0.007 which is
quoted, by Fouché As mentioned before, data referring to liquid (i.e.,
liquefied) acetylene are of no practical importance, because the substance is
too dangerous to use. They are, however, interesting in so far as they
indicate the differences in properties between acetylene converted into the
liquid state by great pressure, and acetylene dissolved in acetone under less
pressure; which differences make the solution fit for employment. It may be
observed that as the solution of acetylene in acetone is a liquid, the
acetylene must exist therein as a liquid; it is, in fact, liquid acetylene in a
state of dilution, the diluent being an exothermic and comparatively stable
body. The specific heat of acetylene is given by M. A. Morel at 0.310,
though he has not stated by whom the value was determined. For the
purpose of a calculation in Chapter III. the specific heat at constant pressure
was assumed to be 0.25, which, in the absence of precise information,
appears somewhat more probable as an approximation to the truth. The ratio
(k or C_p/C_v ) of the specific heat at constant pressure to that at constant
volume has been found by Maneuvrier and Fournier to be 1.26; but they did
not measure the specific heat itself. [Footnote: The ratio 1.26 k or
(C_p/C_v) has been given in many text-books as the value of the specific
heat of acetylene, whereas this value should obviously be only about one-
fourth or one-fifth of 1.26.

By employing the ordinary gas laws it is possible approximately to
calculate the specific heat of acetylene from Maneuvrier and Fournier's
ratio. Taking the molecular weight of acetylene as 26, we have

26 C_p - 26 C_v = 2 cal.,

and

Page 220

C_p = 1.26 C_v.

From this it follows that C_p, i.e., the specific heat at constant pressure of
acetylene, should be 0.373.] It will be seen that this value for k differs
considerably from the corresponding ratio in the case of air and many
common gases, where it is usually 1.41; the figure approaches more closely
that given for nitrous oxide. For the specific heat of calcium carbide
Carlson quotes the following figures:

0° 1000° 1500° 2000° 2500° 3000° 3500°
0.247 0.271 0.296 0.325 0.344 0.363 0.381

The molecular volume of acetylene is 0.8132 (oxygen = 1).

According to the international atomic weights adopted in 1908, the
molecular weight of acetylene is 26.016 if O = 16; in round numbers, as
ordinarily used, it is 26. Employing the latest data for the weight of 1 litre
of dry hydrogen and of dry normal air containing 0.04 per cent. of carbon
dioxide at a temperature of 0° C. and a barometric pressure of 760 mm. in
the latitude of London, viz., 0.089916 and 1.29395 grammes respectively
(Castell-Evans), it now becomes possible to give the weight of a known
volume of dry or moist acetylene as measured under stated conditions with
some degree of accuracy. Using 26.016 as the molecular weight of the gas
(O = 16), 1 litre of dry acetylene at 0° C. and 760 mm. weighs 1.16963
grammes, or 1 gramme measures 0.854973 litre. From this it follows that
the theoretical specific gravity of the gas at 0°/0° C. is 0.9039 (air = 1), a
figure which may be compared with Leduc's experimental value of 0.9056.
Taking as the coefficient of expansion at constant pressure the figure
already given, viz., 0.003738, the weights and measures of dry and moist
acetylene observed under British conditions (60° F. and 30 inches of
mercury) become approximately:

Dry. Saturated.
1 litre . . . 1.108 grm. . . 1.102 grm.
1 gramme . . . 0.902 litre. . . 0.907 litre.
1000 cubic feet . 69.18 lb. . . . 68.83 lb.

Page 221

It should be remembered that unless the gas has been passed through a
chemical drier, it is always saturated with aqueous vapour, the amount of
water present being governed by the temperature and pressure. The 1 litre
of moist acetylene which weighs 1.102 gramme at 60° F. and 30 inches of
mercury, contains 0.013 gramme of water vapour; and therefore the weight
of dry acetylene in the 1 litre of moist gas is 1.089 gramme. Similarly, the
68.83 pounds which constitute the weight of 1000 cubic feet of moist
acetylene, as measured under British standard conditions, are composed of
almost exactly 68 pounds of dry acetylene and 0.83 pound of water vapour.
The data required in calculating the mass of vapour in a known volume of a
saturated gas at any observed temperature and pressure, i.e., in reducing the
figures to those which represent the dry gas at any other (standard)
temperature and pressure, will be found in the text-books of physical
chemistry. It is necessary to recollect that since coal-gas is measured wet,
the factors given in the table quoted in Chapter XIV. from the "Notification
of the Gas Referees" simply serve to convert the volume of a wet gas
observed under stated conditions to the equivalent volume of the same wet
gas at the standard conditions mentioned.

HEAT OF COMBUSTION, &C--Based on Berthelot and Matignon's value
for the heat of combustion which is given on a subsequent page, viz., 315.7
large calories per molecular weight of 26.016 grammes, the calorific power
of acetylene under different conditions is shown in the following table:

Dry. Dry. Saturated.
0° C. & 760 mm. 60° F & 30 ins. 60° F. & 30 ins.

1 gramme 12.14 cals. 12.14 cals. 12.0 cals.
1 litre 14.l9 " 13.45 " 13.22 "
1 cubic foot 40.19 " 380.8 " 374.4 "

The figures in the last column refer to the dry acetylene in the gas, no
correction having been made for the heat absorbed by the water vapour
present. As will appear in Chapter X., the average of actual determinations
of the calorific value of ordinary acetylene is 363 large calories or 1440
B.Th.U. per cubic foot. The temperature of ignition of acetylene has been
generally stated to be about 480° C. V. Meyer and Münch in 1893 found

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that a mixture of acetylene and oxygen ignited between 509° and 515° C.
Recent (1909) investigations by H. B. Dixon and H. F. Coward show,
however, that the ignition temperature in neat oxygen is between 416° and
440° (mean 428° C.) and in air between 406° and 440°, with a mean of 429°
C. The corresponding mean temperature of ignition found by the same
investigators for other gases are: hydrogen, 585°; carbon monoxide, moist
664°, dry 692°; ethylene, in oxygen 510°, in air 543°; and methane, in
oxygen between 550° and 700°, and in air, between 650° and 750° C.

Numerous experiments have been performed to determine the temperature
of the acetylene flame. According to an exhaustive research by L. Nichols,
when the gas burns in air it attains a maximum temperature of 1900° C. ±
20°, which is 120° higher than the temperature he found by a similar
method of observation for the coal-gas flame (fish-tail burner). Le Chatelier
had previously assigned to the acetylene flame a temperature between
2100° and 2400°, while Lewes had found for the dark zone 459°, for the
luminous zone 1410°, and for the tip 1517° C, Féry and Mahler have also
made measurements of the temperatures afforded by acetylene and other
fuels, some of their results being quoted below. Féry employed his optical
method of estimating the temperature, Mahler a process devised by Mallard
and Le Chatelier. Mahler's figures all relate to flames supplied with air at a
temperature of 0° C. and a constant pressure of 760 mm.

Hydrogen . . . . . . . . . . . 1900
1960
Carbon monoxide . . . . . . . . . --
2100
Methane . . . . . . . . . . . -- _
1850
Coal-gas (luminous) . . . . . . . . 1712 |
" (atmospheric, with deficient supply of air) . 1812 |
1950
" (atmospheric, with full supply of air) . . 1871 _|
Water-gas . . . . . . . . . . --
2000
Oxy-coal-gas blowpipe . . . . . . . 2200 --
Oxy-hydrogen blowpipe . . . . . . . 2420 --
Acetylene . . . . . . . . . . 2548
2350
Alcohol . . . . . . . . . . . 1705

Page 223

1700
Alcohol (in Denayrouze Bunsen) . . . . . 1862 --
Alcohol and petrol in equal parts . . . . 2053 --
Crude petroleum (American) . . . . . . --
2000
Petroleum spirit " . . . . . . . --
1920
Petroleum oil " . . . . . . . --
1660

Catani has published the following determinations of the temperature
yielded by acetylene when burnt with cold and hot air and also with
oxygen:

Acetylene and cold air . . . . . . 2568° C.
" air at 500° C . . . . 2780° C.
" air at 1000° C . . . . 3000° C.
" oxygen . . . . . . 4160° C.

EXPLOSIVE LIMITS.--The range of explosibility of mixtures of acetylene
and air has been determined by various observers. Eitner's figures for the
lower and upper explosive limits, when the mixture, at 62.6° F., is in a tube
19 mm. in diameter, and contains 1.9 per cent. of aqueous vapour, are 3.35
and 52.3 per cent. of acetylene (cf. Chapter X.). In this case the mixture was
fired by electric spark. In wider vessels, the upper explosive limit, when the
mixture was fired by a Bunsen flame, was found to be as high as 75 per
cent. of acetylene. Eitner also found that when 13 of the 21 volumes of
oxygen in air are displaced by carbon dioxide, a mixture of such "carbon
dioxide air" with acetylene is inexplosive in all proportions. Also that when
carbon dioxide is added to a mixture of acetylene and air, an explosion no
longer occurs when the carbon dioxide amounts to 46 volumes or more to
every 54 volumes of air, whatever may be the proportion of acetylene in the
mixture. [Footnote: According to Caro, if acetylene is added to a mixture
composed of 55 per cent. by volume of air and 45 per cent. of carbon
dioxide, the whole is only explosive when the proportion of acetylene lies
between 5.0 and 5.8 per cent. Caro has also quoted the effect of various
inflammable vapours upon the explosive limits of acetylene, his results
being referred to in Chapter X.] These figures are valuable in connexion
with the prevention of the formation of explosive mixtures of air and
acetylene when new mains or plant are being brought into operation (cf.

Page 224

Chapter VII.). Eitner has also shown, by direct investigation on mixtures of
other combustible gases and air, that the range of explosibility is greatly
reduced by increase in the proportion of aqueous vapour present. As the
proportion of aqueous vapour in gas standing over water increases with the
temperature the range of explosibility of mixtures of a combustible gas and
air is naturally and automatically reduced when the temperature rises,
provided the mixture is in contact with water. Thus at 17.0° C., mixtures of
hydrogen, air, and aqueous vapour containing from 9.3 to 65.0 per cent, of
hydrogen are explosive, whereas at 78.1° C., provided the mixture is
saturated with aqueous vapour, explosion occurs only when the percentage
of hydrogen in the mixture is between 11.2 and 21.9. The range of
explosibility of mixtures of acetylene and air is similarly reduced by the
addition of aqueous vapour (though the exact figures have not been
experimentally ascertained); and hence it follows that when the temperature
in an acetylene generator in which water is in excess, or in a gasholder,
rises, the risk of explosion, if air is mixed with the gas, is automatically
reduced with the rise in temperature by reason of the higher proportion of
aqueous vapour which the gas will retain at the higher temperature. This
fact is alluded to in Chapter II. Acetone vapour also acts similarly in
lowering the upper explosive limit of acetylene (cf. Chapter XI.).

It may perhaps be well to indicate briefly the practical significance of the
range of explosibility of a mixture of air and a combustible gas, such as
acetylene. The lower explosive limit is the lowest percentage of
combustible gas in the mixture of it and air at which explosion will occur in
the mixture if a light or spark is applied to it. If the combustible gas is
present in the mixture with air in less than that percentage explosion is
impossible. The upper explosive limit is the highest percentage of
combustible gas in the mixture of it and air at which explosion will occur in
the mixture if a light or spark is applied to it. If the combustible gas is
present in the mixture with air in more than that percentage explosion is
impossible. Mixtures, however, in which the percentage of combustible gas
lies between these two limits will explode when a light or spark is applied
to them; and the comprehensive term "range of explosibility" is used to
cover all lying between the two explosive limits. If, then, a naked light is
applied to a vessel containing a mixture of a combustible gas and air, in
which mixture the proportion of combustible gas is below the lower limit of

Page 225

explosibility, the gas will not take fire, but the light will continue to burn,
deriving its necessary oxygen from the excess of air present. On the other
hand, if a light is applied to a vessel containing a mixture of a combustible
gas and air, in which mixture the proportion of combustible gas is above the
upper limit of explosibility, the light will be extinguished, and within the
vessel the gaseous mixture will not burn; but it may burn at the open mouth
of the vessel as it comes in contact with the surrounding air, until by
diffusion, &c., sufficient air has entered the vessel to form, with the
remaining gas, a mixture lying within the explosive limits, when an
explosion will occur. Again, if a gaseous mixture containing less of its
combustible constituent than is necessary to attain the lower explosive limit
escapes from an open-ended pipe and a light is applied to it, the mixture
will not burn as a useful compact flame (if, indeed, it fires at all); if the
mixture contains more of its combustible constituent than is required to
attain the upper explosive limit, that mixture will burn quietly at the mouth
of the pipe and will be free from any tendency to fire back into the pipe--
assuming, of course, that the gaseous mixture within the pipe is constantly
travelling towards the open end. If, however, a gaseous mixture containing
a proportion of its combustible constituent which lies between the lower
and the upper explosive limit of that constituent escapes from an open-
ended pipe and a light is applied, the mixture will fire and the flame will
pass back into the pipe, there to produce an explosion, unless the orifice of
the said pipe is so small as to prevent the explosive wave passing (as is the
case with a proper acetylene burner), or unless the pipe itself is so narrow as
appreciably to alter the range of explosibility by lowering the upper
explosive limit from its normal value.

By far the most potent factor in altering the range of explosibility of any gas
when mixed with air is the diameter of the vessel containing or delivering
such mixture. Le Chatelier has investigated this point in the case of
acetylene, and his values are reproduced overleaf; they are comparable
among themselves, although it will be observed that his absolute results
differ somewhat from those obtained by Eitner which are quoted later:

Explosive Limits of Acetylene mixed with Air.--(Le Chatelier.)

___________________________________________________________

Page 226

| | | |
| | Explosive Limits. | |
| Diameter of Tube |_______________________| Range of |
| in Millimetres. | | | Explosibility. |
| | Lower. | Upper. | |
|__________________|___________|___________|________________|
| | | | |
| | Per Cent. | Per Cent. | Per Cent. |
| 40 | 2.9 | 64 | 61.1 |
| 30 | 3.1 | 62 | 58.9 |
| 20 | 3.5 | 55 | 51.5 |
| 6 | 4.0 | 40 | 36.0 |
| 4 | 4.5 | 25 | 20.5 |
| 2 | 5.0 | 15 | 10.0 |
| 0.8 | 7.7 | 10 | 2.3 |
| 0.5 | ... | ... | ... |
|__________________|___________|___________|________________|

Thus it appears that past an orifice or constriction 0.5 mm. in diameter no
explosion of acetylene can proceed, whatever may be the proportions
between the gas and the air in the mixture present.

With every gas the explosive limits and the range of explosibility are also
influenced by various circumstances, such as the manner of ignition, the
pressure, and other minor conditions; but the following figures for mixtures
of air and different combustible gases were obtained by Eitner under similar
conditions, and are therefore strictly comparable one with another. The
conditions were that the mixture was contained in a tube 19 mm. (3/4-inch)
wide, was at about 60° to 65° F., was saturated with aqueous vapour, and
was fired by electric spark.

Table giving the Percentage by volume of Combustible Gas in a Mixture of
that Gas and Air corresponding with the Explosive Limits of such a
Mixture.--(Eitner.)

_______________________________________________________________
_____
| | | |
|
| Description of | Lower | Upper | Difference between
the |

Page 227

| Combustible Gas. | Explosive | Explosive | Lower and Upper
Limits, |
| | Limit. | Limit. | showing the
range |
| | | | covered by the
|
| | | | Explosive
Mixtures. |
|__________________|___________|___________|___________________
______|
| | | |
|
| | Per Cent. | Per Cent. | Per Cent.
|
| Carbon monoxide | 16.50 | 74.95 | 58.45
|
| Hydrogen | 9.45 | 66.40 | 57.95
|
| Water-gas | | |
|
| (uncarburetted) | 12.40 | 66.75 | 54.35
|
| ACETYLENE | 3.35 | 52.30 | 48.95
|
| Coal-gas | 7.90 | 19.10 | 11.20
|
| Ethylene | 4.10 | 14.60 | 10.50
|
| Methane | 6.10 | 12.80 | 6.70
|
| Benzene (vapour) | 2.65 | 6.50 | 3.85
|
| Pentane " | 2.40 | 4.90 | 2.50
|
| Benzoline " | 2.40 | 4.90 | 2.50
|
|__________________|___________|___________|___________________
______|

These figures are of great practical significance. They indicate that a
mixture of acetylene and air becomes explosive (i.e., will explode if a light
is applied to it) when only 3.35 per cent. of the mixture is acetylene, while a
similar mixture of coal-gas and air is not explosive until the coal-gas
reaches 7.9 per cent. of the mixture. And again, air may be added to coal-
gas, and it does not become explosive until the coal-gas is reduced to 19.1

Page 228

per cent. of the mixture, while, on the contrary, if air is added to acetylene,
the mixture becomes explosive as soon as the acetylene has fallen to 52.3
per cent. Hence the immense importance of taking precautions to avoid, on
the one hand, the escape of acetylene into the air of a room, and, on the
other hand, the admixture of air with the acetylene in any vessel containing
it or any pipe through which it passes. These precautions are far more
essential with acetylene than with coal-gas. The table shows further how
great is the danger of explosion if benzene, benzoline, or other similar
highly volatile hydrocarbons [Footnote: The nomenclature of the different
volatile spirits is apt to be very confusing. "Benzene" is the proper name for
the most volatile hydrocarbon derived from coal-tar, whose formula is
C_6H_6. Commercially, benzene is often known as "benzol" or "benzole";
but it would be generally advantageous if those latter words were only used
to mean imperfectly rectified benzene, i.e., mixtures of benzene with
toluene, &c., such as are more explicitly understood by the terms "90.s
benzol" and "50.s benzol." "Gasoline," "carburine," "petroleum ether,"
"benzine," "benzoline," "petrol," and "petroleum spirit" all refer to more or
less volatile (the most volatile being mentioned first) and more or less
thoroughly rectified products obtained from petroleum. They are mixtures
of different hydrocarbons, the greater part of them having the general
chemical formula C_nH_2n+2 where n = 5 or more. None of them is a
definite chemical compound as is benzene; when n = 5 only the product is
pentane. These hydrocarbons are known to chemists as "paraffins,"
"naphthenes" being occasionally met with; while a certain proportion of
unsaturated hydrocarbons is also present in most petroleum spirits. The
hydrocarbons of coal-tar are "aromatic hydrocarbons," their generic formula
being C_nH_2^n-6, where n is never less than 6.] are allowed to vaporise in
a room in which a light may be introduced. Less of the vapour of these
hydrocarbons than of acetylene in the air of a room brings the mixture to
the lower explosive limit, and therewith subjects it to the risk of explosion.
This tact militates strongly against the use of such hydrocarbons within a
house, or against the use of air-gas, which, as explained in Chapter I., is air
more or less saturated with the vapour of volatile hydrocarbons.
Conversely, a combustible gas, such as acetylene, may be safely
"carburetted" by these hydrocarbons in a properly constructed apparatus set
up outside the dwelling-house, as explained in Chapter X., because there
would be no air (as in air-gas) in the pipes, &c., and a relatively large

Page 229

escape of carburetted acetylene would be required to produce an explosive
atmosphere in a room. Moreover, the odour of the acetylene itself would
render the detection of a leak far easier with carburetted acetylene than with
air-gas.

N. Teclu has investigated the explosive limits of mixtures of air with certain
combustible gases somewhat in the same manner as Eitner, viz.: by firing
the mixture in an eudiometer tube by means of an electric spark. He
worked, however, with the mixture dry instead of saturated with aqueous
vapour, which doubtless helps to account for the difference between his and
Eitner's results.

Table giving the Percentages by volume of Combustible Gas in a
Dehydrated Mixture of that Gas and Air between which the Explosive
Limits of such a Mixture lie.--(Teclu).

_______________________________________________________________
_____
| | |
|
| | Lower Explosive Limit. | Upper Explosive
Limit. |
| Description of
|________________________|________________________|
| Combustible Gas. | |
|
| | Per Cent. of Gas. | Per Cent. of
Gas. |
|__________________|________________________|__________________
______|
| | |
|
| ACETYLENE | 1.53-1.77 | 57.95-58.65
|
| Hydrogen | 9.73-9.96 | 62.75-63.58
|
| Coal-gas | 4.36-4.82 | 23.35-23.63
|
| Methane | 3.20-3.67 | 7.46- 7.88
|
|__________________|________________________|__________________
______|

Page 230

Experiments have been made at Lechbruch in Bavaria to ascertain directly
the smallest proportion of acetylene which renders the air of a room
explosive. Ignition was effected by the flame resulting when a pad of
cotton-wool impregnated with benzoline or potassium chlorate was fired by
an electrically heated wire. The room in which most of the tests were made
was 8 ft. 10 in. long, 6 ft. 7 in. wide, and 6 ft. 8 in. high, and had two
windows. When acetylene was generated in this room in normal conditions
of natural ventilation through the walls, the volume generated could amount
to 3 per cent. of the air-space of the room without explosion ensuing on
ignition of the wool, provided time elapsed for equable diffusion, which,
moreover, was rapidly attained. Further, it was found that when the whole
of the acetylene which 2 kilogrammes or 4.4 lb. of carbide (the maximum
permissible charge in many countries for a portable lamp for indoor use)
will yield was liberated in a room, a destructive explosion could not ensue
on ignition provided the air-space exceeded 40 cubic metres or 1410 cubic
feet, or, if the evolved gas were uniformly diffused, 24 cubic metres or 850
cubic feet. When the walls of the room were rendered impervious to air and
gas, and acetylene was liberated, and allowed time for diffusion, in the air
of the room, an explosion was observed with a proportion of only 2-1/2 per
cent. of acetylene in the air.

Solubility of Acetylene in Various Liquids.

_______________________________________________________________
______
| | | |
|
| | | Volumes of |
|
| | Tem- | Acetylene |
|
| Solvent. |perature.|dissolved by|
Authority. |
| | | 100 Vols. |
|
| | | of Solvent.|
|
|___________________________|_________|____________|___________
_______|

Page 231

| | | |
|
| | Degs. C | |
|
| Acetone . . . . | 15 | 2500 | Claude and
Hess |
| " . . . . | 50 | 1250 | "
|
| Acetic acid; alcohol . | 18 | 600 | Berthelot
|
| Benzoline; chloroform . | 18 | 400 | "
|
| Paraffin oil . . . | 0 | 103.3 | E. Muller
|
| " . . . | 18 | 150 | Berthelot
|
| Olive oil . . . . | -- | 48 | Fuchs and
Schiff |
| Carbon bisulphide . . | 18 | 100 | Berthelot
|
| " tetrachloride . | 0 | 25 | Nieuwland
|
| Water (at 4 65 atmospheres| | |
|
| pressure) . . | 0 | 160 | Villard
|
| " (at 755 mm. pressure)| 12 | 118 | Berthelot
|
| " (760 mm. pressure) . | 12 | 106.6 | E. Müller
|
| " " . | 15 | 110 | Lewes
|
| " " . | 18 | 100 | Berthelot
|
| " " . | -- | 100 | E. Davy
(in 1836)|
| " " . | 19.5 | 97.5 | E. Müller
|
| Milk of lime: about 10 | | |
|
| grammes of calcium hy- | 5 | 112 |
Hammerschmidt |
| droxide per 100 c.c. . | | | and
Sandmann |
| " " " | 10 | 95 | "
|
| " " " | 20 | 75 | "
|

Page 232

| " " " | 50 | 38 | "
|
| " " " | 70 | 20 | "
|
| " " " | 90 | 6 | "
|
| Solution of common salt,5%| 19 | 67.9 | "
|
| (sodium chloride) " | 25 | 47.7 | "
|
| " 20%| 19 | 29.6 | "
|
| " " | 25 | 12.6 | "
|
| "(nearly saturated, | | |
|
| 26%) . . | 15 | 20.6 | "
|
| "(saturated, sp. gr.| | |
|
| 1-21) . . | 0 | 22.0 | E. Müller
|
| " " " | 12 | 21.0 | "
|
| " " " | 18 | 20.4 | "
|
| Solution of calcium | | |
Hammerschmidt |
| chloride (saturated) . | 15 | 6.0 | and
Sandmann |
| Bergé and Reychler's re- | | |
|
| agent . . . . | -- | 95 | Nieuwland
|
|___________________________|_________|____________|___________
_______|

SOLUBILITY.--Acetylene is readily soluble in many liquids. It is desirable,
on the one hand, as indicated in Chapter III., that the liquid in the seals of
gasholders, &c., should be one in which acetylene is soluble to the smallest
degree practically attainable; while, on the other hand, liquids in which
acetylene is soluble in a very high degree are valuable agents for its storage
in the liquid state. Hence it is important to know the extent of the solubility
of acetylene in a number of liquids. The tabular statement (p. 179) gives the

Page 233

most trustworthy information in regard to the solubilities under the normal
atmospheric pressure of 760 mm. or thereabouts.

The strength of milk of lime quoted in the above table was obtained by
carefully allowing 50 grammes of carbide to interact with 550 c.c. of water
at 5° C. A higher degree of concentration of the milk of lime was found by
Hammerschmidt and Sandmann to cause a slight decrease in the amount of
acetylene held in solution by it. Hammerschmidt and Sandmann's figures,
however, do not agree well with others obtained by Caro, who has also
determined the solubility of acetylene in lime-water, using first, a clear
saturated lime-water prepared at 20° C. and secondly, a milk of lime
obtained by slaking 10 grammes of quicklime in 100 c.c. of water. As
before, the figures relate to the volumes of acetylene dissolved at
atmospheric pressure by 100 volumes of the stated liquid.

_________________________________________________
| | | |
| Temperature. | Lime-water. | Milk of Lime. |
|_______________|_______________|_________________|
| | | |
| Degs C. | | |
| 0 | 146.2 | 152.6 |
| 5 | 138.5 | -- |
| 15 | 122.8 | 134.8 |
| 50 | 43.9 | 62.6 |
| 90 | 6.2 | 9.2 |
|_______________|_______________|_________________|

Figures showing the solubility of acetylene in plain water at different
temperatures have been published in Landolt-Börnstein's Physico-
Chemical Tables. These are reproduced below. The "Coefficient of
Absorption" is the volume of the gas, measured at 0° C. and a barometric
height of 760 mm. taken up by one volume of water, at the stated
temperature, when the gas pressure on the surface, apart from the vapour
pressure of the water itself, is 760 mm. The "Solubility" is the weight of
acetylene in grammes taken up by 100 grammes of water at the stated
temperature, when the total pressure on the surface, including that of the
vapour pressure of the water, is 760 mm.

Page 234

_____________________________________________
| | | |
| Temperature. | Coefficient of | Solubility. |
| | Absorption. | |
|______________|________________|_____________|
| | | |
| Degs. C. | | |
| 0 | 1.73 | 0.20 |
| 1 | 1.68 | 0.19 |
| 2 | 1.63 | 0.19 |
| 3 | 1.58 | 0.18 |
| 4 | 1.53 | 0.18 |
| 5 | 1.49 | 0.17 |
| 6 | 1.45 | 0.17 |
| 7 | 1.41 | 0.16 |
| 8 | 1.37 | 0.16 |
| 9 | 1.34 | 0.15 |
| 10 | 1.31 | 0.15 |
| 11 | 1.27 | 0.15 |
| 12 | 1.24 | 0.14 |
| 13 | 1.21 | 0.14 |
| 14 | 1.18 | 0.14 |
| 15 | 1.15 | 0.13 |
| 16 | 1.13 | 0.13 |
| 17 | 1.10 | 0.13 |
| 18 | 1.08 | 0.12 |
| 19 | 1.05 | 0.12 |
| 20 | 1.03 | 0.12 |
| 21 | 1.01 | 0.12 |
| 22 | 0.99 | 0.11 |
| 23 | 0.97 | 0.11 |
| 24 | 0.95 | 0.11 |
| 25 | 0.93 | 0.11 |
| 26 | 0.91 | 0.10 |
| 27 | 0.89 | 0.10 |
| 28 | 0.87 | 0.10 |
| 29 | 0.85 | 0.10 |
| 30 | 0.84 | 0.09 |
|______________|________________|_____________|

Advantage is taken, as explained in Chapter XI., of the high degree of
solubility of acetylene in acetone, to employ a solution of the gas in that
liquid when acetylene is wanted in a portable condition. The solubility
increases very rapidly with the pressure, so that under a pressure of twelve
atmospheres acetone dissolves about 300 times its original volume of the

Page 235

gas, while the solubility also increases greatly with a reduction in the
temperature, until at -80° C. acetone takes up 2000 times its volume of
acetylene under the ordinary atmospheric pressure. Further details of the
valuable qualities of acetone as a solvent of acetylene are given in Chapter
XI., but it may here be remarked that the successful utilisation of the
solvent power of acetone depends to a very large extent on the absolute
freedom from moisture of both the acetylene and the acetone, so that
acetone of 99 per cent. strength is now used as the solvent.

Turning to the other end of the scale of solubility, the most valuable liquids
for serving as seals of gasholders, &c., are readily discernible. Far superior
to all others is a saturated solution of calcium chloride, and this should be
selected as the confining liquid whenever it is important to avoid
dissolution of acetylene in the liquid as far as may be. Brine comes next in
order of merit for this purpose, but it is objectionable on account of its
corrosive action on metals. Olive oil should, according to Fuchs and Schiff,
be of service where a saline liquid is undesirable; mineral oil seems useless.
Were they concordant, the figures for milk of lime would be particularly
useful, because this material is naturally the confining liquid in the
generating chambers of carbide-to-water apparatus, and because the
temperature of the liquid rises through the heat evolved during the
generation of the gas (vide Chapters II. and III.). It will be seen that these
figures would afford a means of calculating the maximum possible loss of
gas by dissolution when a known volume of sludge is run off from a
carbide-to- water generator at about any possible temperature.

According to Garelli and Falciola, the depression in the freezing-point of
water caused by the saturation of that liquid with acetylene is 0.08° C., the
corresponding figure for benzene in place of water being 1.40° C. These
figures indicate that 100 parts by weight of water should dissolve 0.1118
part by weight of acetylene at 0° C., and that 100 parts of benzene should
dissolve about 0.687 part of acetylene at 5° C. In other words, 100 volumes
of water at the freezing-point should dissolve 95 volumes of acetylene, and
100 volumes of benzene dissolve some 653 volumes of the gas. The figure
calculated for water in this way is lower than that which might be expected
from the direct determinations at other temperatures already referred to; that
for benzene may be compared with Berthelot's value of 400 volumes at 18°

Page 236

C. Other measurements of the solubility of acetylene in water at 0° C. have
given the figure 0.1162 per cent. by weight.

TOXICITY.--Many experiments have been made to determine to what
extent acetylene exercises a toxic action on animals breathing air containing
a large proportion of it; but they have given somewhat inconclusive results,
owing probably to varying proportions of impurities in the samples of
acetylene used. The sulphuretted hydrogen and phosphine which are found
in acetylene as ordinarily prepared are such powerful toxic agents that they
would always, in cases of "acetylene" poisoning, be largely instrumental in
bringing about the effects observed. Acetylene per se would appear to have
but a small toxic action; for the principal toxic ingredient in coal-gas is
carbon monoxide, which does not occur in sensible quantity in acetylene as
obtained from calcium carbide. The colour of blood is changed by
inhalation of acetylene to a bright cherry-red, just as in cases of poisoning
by carbon monoxide; but this is due to a more dissolution of the gas in the
haemoglobin of the blood, so that there is much more hope of recovery for a
subject of acetylene poisoning than for one of coal-gas poisoning.
Practically the risk of poisoning by acetylene, after it has been purified by
one of the ordinary means, is nil. The toxic action of the impurities of crude
acetylene is discussed in Chapter V.

Acetylene is an "endothermic" compound, as has been mentioned in
Chapter II., where the meaning of the expression endothermic is explained.
It has there been indicated that by reason of its endothermic nature it is
unsafe to have acetylene at either a temperature of 780° C. and upwards, or
at a pressure of two atmospheres absolute, or higher. If that temperature or
that pressure is exceeded, dissociation (i.e., decomposition into its
elements), if initiated at any spot, will extend through the whole mass of
acetylene. In this sense, acetylene at or above 780° C., or at two or more
atmospheres pressure, is explosive in the absence of air or oxygen, and it is
thereby distinguished from the majority of other combustible gases, such as
the components of coal-gas. But if, by dilution with another gas, the partial
pressure of the acetylene is reduced, then the mixture may be subjected to a
higher pressure than that of two atmospheres without acquiring
explosiveness, as is fully shown in Chapter XI. Thus it becomes possible
safely to compress mixtures of acetylene and oil-gas or coal-gas, whereas

Page 237

unadmixed acetylene cannot be safely kept under a pressure of two
atmospheres absolute or more. In a series of experiments carried out by
Dupré on behalf of the British Home Office, and described in the Report on
Explosives for 1897, samples of moist acetylene, free from air, but
apparently not purified by any chemical process, were exposed to the
influence of a bright red-hot wire. When the gas was held in the containing
vessel at the atmospheric pressure then obtaining, viz., 30.34 inches (771
mm.) of mercury, no explosion occurred. When the pressure was raised to
45.34 inches (1150 mm.), no explosion occurred; but when the pressure was
further raised to 59.34 inches (1505 mm., or very nearly two atmospheres
absolute) the acetylene exploded, or dissociated into its elements.

Acetylene readily polymerises when heated, as has been stated in Chapter
II., where the meaning of the term "polymerisation" has been explained.
The effects of the products of the polymerisation of acetylene on the flame
produced when the gas is burnt at the ordinary acetylene burners have been
stated in Chapter VIII., where the reasons therefor have been indicated. The
chief primary product of the polymerisation of acetylene by heat appears to
be benzene. But there are also produced, in some cases by secondary
changes, ethylene, methane, naphthalene, styrolene, anthracene, and
homologues of several of these hydrocarbons, while carbon and hydrogen
are separated. The production of these bodies by the action of heat on
acetylene is attended by a reduction of the illuminative value of the gas,
while owing to the change in the proportion of air required for combustion
(see Chapter VIII.), the burners devised for the consumption of acetylene
fail to consume properly the mixture of gases formed by polymerisation
from the acetylene. It is difficult to compare the illuminative value of the
several bodies, as they cannot all be consumed economically without
admixture, but the following table indicates approximately the maximum
illuminative value obtainable from them either by combustion alone or in
admixture with some non- illuminating or feebly-illuminating gas:

________________________________________________
| | | |
| | | Candles per |
| | | Cubic Foot |
|______________|___________________|_____________|
| | | |

Page 238

| | | (say) |
| Acetylene | C_2H_2 | 50 |
| Hydrogen | H_2 | 0 |
| Methane | CH_4 | 1 |
| Ethane | C_2H_6 | 7 |
| Propane | C_3H_8 | 11 |
| Pentane | C_5H_12 (vapour) | 35 |
| Hexane | C_6H_14 " | 45 |
| Ethylene | C_2H_4 | 20 |
| Propylene | C_3H_6 | 25 |
| Benzene | C_6H_6 (vapour) | 200 |
| Toluene | C_7H_8 " | 250 |
| Naphthalene | C_10H_8 " | 400 |
|______________|___________________|_____________|

It appears from this table that, with the exception of the three hydrocarbons
last named, no substance likely to be formed by the action of heat on
acetylene has nearly so high an illuminative value--volume for volume--as
acetylene itself. The richly illuminating vapours of benzene and
naphthalene (and homologues) cannot practically add to the illuminative
value of acetylene, because of the difficulty of consuming them without
smoke, unless they are diluted with a large proportion of feebly- or non-
illuminating gas, such as methane or hydrogen. The practical effect of
carburetting acetylene with hydrocarbon vapours will be shown in Chapter
X. to be disastrous so far as the illuminating efficiency of the gas is
concerned. Hence it appears that no conceivable products of the
polymerisation of acetylene by heat can result in its illuminative value
being improved--even presupposing that the burners could consume the
polymers properly--while practically a considerable deterioration of its
value must ensue.

The heat of combustion of acetylene was found by J. Thomson to be 310.57
large calories per gramme-molecule, and by Berthelot to be 321.00 calories.
The latest determination, however, made by Berthelot and Matignon shows
it to be 315.7 calories at constant pressure. Taking the heat of formation of
carbon dioxide from diamond carbon at constant pressure as 94.3 calories
(Berthelot and Matignon), which is equal to 97.3 calories from amorphous
carbon, and the heat of formation of liquid water as 69 calories; this value
for the heat of combustion of acetylene makes its heat of formation to be
94.3 x 2 + 69 - 315.7 = -58.1 large calories per gramme-molecule (26

Page 239

grammes) from diamond carbon, or -52.1 from amorphous carbon. It will
be noticed that the heat of combustion of acetylene is greater than the
combined heats of combustion of its constituents; which proves that heat
has been absorbed in the union of the hydrogen and carbon in the molecule,
or that acetylene is endothermic, as elsewhere explained. These
calculations, and others given in Chapter IX., will perhaps be rendered
more intelligible by the following table of thermochemical phenomena:

_______________________________________________________________
| | | |
|
| Reaction. | Diamond | Amorphous |
|
| | Carbon. | Carbon. |
|
|________________________________|_________|___________|_______
_|
| | | |
|
| (1) C (solid) + O . . . | 26.1 | 29.1 | ...
|
| (2) C (solid) + O_2 . . . | 94.3 | 97.3 | ...
|
| (3) CO + O (2 - 1) . . . | ... | ... | 68.2
|
| (4) Conversion of solid carbon | | |
|
| into gas (3 - 1) . . . | 42.1 | 39.1 | ...
|
| (5) C (gas) + O (1 + 4) . . | ... | ... | 68.2
|
| (6) Conversion of amorphous | | |
|
| carbon to diamond . . | ... | ... | 3.0
|
| (7) C_2 + H_2 . . . . | -58.1 | -52.1 | ...
|
| (8) C_2H_2 + 2-1/2O_2 . . | ... | ... | 315.7
|
|________________________________|_________|___________|_______
_|

Page 240

W. G. Mixter has determined the heat of combustion of acetylene to be
312.9 calories at constant volume, and 313.8 at constant pressure. Using
Berthelot and Matignon's data given above for amorphous carbon, this
represents the heat of formation to be -50.2 (Mixter himself calculates it as
-51.4) calories. By causing compressed acetylene to dissociate under the
influence of an electric spark, Mixter measured its heat of formation as
-53.3 calories. His corresponding heats of combustion of ethylene are 344.6
calories (constant volume) and 345.8 (constant pressure); for its heat of
formation he deduces a value -7.8, and experimentally found one of about
-10.6 (constant pressure).

THE ACETYLENE FLAME.--It has been stated in Chapter I. that
acetylene burnt in self-luminous burners gives a whiter light than that
afforded by any other artificial illuminant, because the proportion of the
various spectrum colours in the light most nearly resembles the
corresponding proportion found in the direct rays of the sun. Calling the
amount of monochromatic light belonging to each of the five main
spectrum colours present in the sun's rays unity in succession, and
comparing the amount with that present in the light obtained from
electricity, coal-gas, and acetylene, Münsterberg has given the following
table for the composition of the several lights mentioned:

_______________________________________________________________
_______
| | | |
| |
| | Electricity | Coal-Gas | Acetylene
| |
|
|________________|__________________|_______________|_______|
| Colour | | | | | |
| |
| in | | | | | | With
| |
| Spectrum.| Arc. | Incan- | Lumin- | Incan- | Alone.| 3 per
| Sun- |
| | | descent.| ous. | descent.| | Cent.
| light.|
| | | | | | | Air.
| |

Page 241

|__________|______|_________|________|_________|_______|_______
|_______|
| | | | | | |
| |
| Red | 2.09 | 1.48 | 4.07 | 0.37 | 1.83 | 1.03
| 1 |
| Yellow | 1.00 | 1.00 | 1.00 | 0.90 | 1.02 | 1.02
| 1 |
| Green | 0.99 | 0.62 | 0.47 | 4.30 | 0.76 | 0.71
| 1 |
| Blue | 0.87 | 0.91 | 1.27 | 0.74 | 1.94 | 1.46
| 1 |
| Violet | 1.08 | 0.17 | 0.15 | 0.83 | 1.07 | 1.07
| 1 |
| Ultra- | | | | | |
| |
| Violet | 1.21 | ... | ... | ... | ... | ...
| 1 |
|__________|______|_________|________|_________|_______|_______
|_______|

These figures lack something in explicitness; but they indicate the greater
uniformity of the acetylene light in its proportion of rays of different wave-
lengths. It does not possess the high proportion of green of the Welsbach
flame, or the high proportion of red of the luminous gas- flame. It is
interesting to note the large amount of blue and violet light in the acetylene
flame, for these are the colours which are chiefly concerned in
photography; and it is to their prominence that acetylene has been found to
be so very actinic. It is also interesting to note that an addition of air to
acetylene tends to make the light even more like that of the sun by reducing
the proportion of red and blue rays to nearer the normal figure.

H. Erdmann has made somewhat similar calculation, comparing the light of
acetylene with that of the Hefner (amyl acetate) lamp, and with coal-gas
consumed in an Argand and an incandescent burner. Consecutively taking
the radiation of the acetylene flame as unity for each of the spectrum
colours, his results are:

_______________________________________________________________
___
| | | |

Page 242

|
| | | | Coal-Gas
|
| Colour in | Wave-Lengths, |
|_______________________|
| Spectrum | uu | Hefner Light | |
|
| | | | Argand |
Incandescent |
|___________|_______________|______________|________|__________
____|
| | | | |
|
| Red | 650 | 1.45 | 1.34 | 1.03
|
| Orange | 610 | 1.22 | 1.13 | 1.00
|
| Yellow | 590 | 1.00 | 1.00 | 1.00
|
| Green | 550 | 0.87 | 0.93 | 0.86
|
| Blue | 490 | 0.72 | 1.27 | 0.92
|
| Violet | 470 | 0.77 | 1.35 | 1.73
|
|___________|_______________|______________|________|__________
____|

B. Heise has investigated the light of different flames, including acetylene,
by a heterochromatic photometric method; but his results varied greatly
according to the pressure at which the acetylene was supplied to the burner
and the type of burner used. Petroleum affords light closely resembling in
colour the Argand coal-gas flame; and electric glow-lamps, unless overrun
and thereby quickly worn out, give very similar light, though with a
somewhat greater preponderance of radiation in the red and yellow.

_______________________________________________________________
_____
| | |
|
| | Percent of Total |
|
| Light. | Energy manifested |

Page 243

Observer. |
| | as Light. |
|
|____________________________|___________________|_____________
______|
| | |
|
| Candle, spermaceti . . | 2.1 | Thomsen
|
| " paraffin . . . | 1.53 | Rogers
|
| Moderator lamp . . . | 2.6 | Thomsen
|
| Coal-gas . . . . . | 1.97 | Thomsen
|
| " . . . . . | 2.40 | Langley
|
| " batswing . . . | 1.28 | Rogers
|
| " Argand . . . | 1.61 | Rogers
|
| " incandesce . . | 2 to 7 | Stebbins
|
| Electric glow-lamp . . | about 6 | Merritt
|
| " " . . | 5.5 | Abney and
Festing |
| Lime light (new) . . . | 14 | Orehore
|
| " (old) . . . | 8.4 | Orehore
|
| Electric arc . . . . | 10.4 | Tyndall;
Nakano |
| " . . . . | 8 to 13 | Marks
|
| Magnesium light . . . | 12.5 | Rogers
|
| Acetylene . . . . | 10.5 | Stewart and
Hoxie |
| " (No. 0 slit burner | 11.35 | Neuberg
|
| " (No. 00000 . . | |
|
| Bray fishtail) | 13.8 | Neuberg
|
| " (No. 3 duplex) . | 14.7 | Neuberg
|
| Geissler tube . . . | 32.0 | Staub

Page 244

|
|____________________________|___________________|_____________
______|

Violle and Féry, also Erdmann, have proposed the use of acetylene as a
standard of light. As a standard burner Féry employed a piece of
thermometer tube, cut off smoothly at the end and having a diameter of 0.5
millimetre, a variation in the diameter up to 10 per cent. being of no
consequence. When the height of the flame ranged from 10 to 25
millimetres the burner passed from 2.02 to 4.28 litres per hour, and the
illuminating power of the light remained sensibly proportional to the height
of the jet, with maximum variations from the calculated value of ±0.008. It
is clear that for such a purpose as this the acetylene must be prepared from
very pure carbide and at the lowest possible temperature in the generator.
Further investigations in this direction should be welcome, because it is
now fairly easy to obtain a carbide of standard quality and to purify the gas
until it is essentially pure acetylene from a chemical point of view.

L. W. Hartmann has studied the flame of a mixture of acetylene with
hydrogen. He finds that the flame of the mixture is richer in light of short
wave-lengths than that of pure acetylene, but that the colour of the light
does not appear to vary with the proportion of hydrogen present.

Numerous investigators have studied the optical or radiant efficiency of
artificial lights, i.e., the proportion of the total heat plus light energy emitted
by the flame which is produced in the form of visible light. Some results are
shown in the table on the previous page.

Figures showing the ratio of the visible light emitted by various illuminants
to the amount of energy expended in producing the light and also the energy
equivalent of each spherical Hefner unit evolved have been published by H.
Lux, whose results follow:

_______________________________________________________________
________
| | | | |
|
| | Ratio of | Ratio of | Mean |

Page 245

Energy |
| | Light | Light | Spherical |
Equiva- |
| Light. | emitted to | emitted to | Illuminat- |
lent to 1 |
| | Total | Energy | ing Power. |
Spherical |
| | Radiation. | Impressed. | Hefners. |
Hefner in |
| | | | |
Watts. |
|____________________|____________|____________|____________|__
_________|
| | | | |
|
| | Per Cent. | Per Cent. | |
|
| Hefner lamp | 0.89 | 0.103 | 0.825 |
0.108 |
| Paraffin lamp, 14" | 1.23 | 0.25 | 12.0 |
0.105 |
| ACETYLENE, 7.2 | | | |
|
| litre burner | 6.36 | 0.65 | 6.04 |
0.103 |
| Coal-gas incandes- | | | |
|
| cent, upturned | 2.26-2.92 | 0.46 | 89.6 |
0.037 |
| " incandes- | | | |
|
| cent, inverted | 2.03-2.97 | 0.51 | 82.3 |
0.035 |
| Carbon filament | | | |
|
| glow-lamp | 3.2-2.7 | 2.07 | 24.5 |
0.085 |
| Nernst lamp | 5.7 | 4.21-3.85 | 91.9 |
0.073 |
| Tantalum lamp | 8.5 | 4.87 | 26.7 |
0.080 |
| Osram lamp | 9.1 | 5.36 | 27.4 |
0.075 |
| Direct-current arc | 8.1 | 5.60 | 524 |
0.047 |
| " " enclosed | 2.0 | 1.16 | 295 |
0.021 |
| Flame arc, yellow | 15.7 | 13.20 | 1145 |

Page 246

0.041 |
| " " white | 7.6 | 6.66 | 760 |
0.031 |
| Alternating- | | | |
|
| current arc | 3.7 | 1.90 | 89 |
0.038 |
| Uviol mercury | | | |
|
| vapour lamp | 5.8 | 2.24 | 344 |
0.015 |
| Quartz lamp | 17.6 | 6.00 | 2960 |
0.014 |
|____________________|____________|____________|____________|__
_________|

CHEMICAL PROPERTIES.--It is unnecessary for the purpose of this work
to give an exhaustive account of the general chemical reactions of acetylene
with other bodies, but a few of the more important must be referred to.
Since the gases are liable to unite spontaneously when brought into contact,
the reactions between, acetylene and chlorine require attention, first,
because of the accidents that have occurred when using bleaching- powder
(see Chapter V.) as a purifying material for the crude gas; secondly, because
it has been proposed to manufacture one of the products of the combination,
viz., acetylene tetrachloride, on a large scale, and to employ it as a detergent
in place of carbon tetrachloride or carbon disulphide. Acetylene forms two
addition products with chlorine, C_2H_2Cl_2, and C_2H_2Cl_4. These are
known as acetylene dichloride and tetrachloride respectively, or more
systematically as dichlorethylene and tetrachlorethane. One or both of the
chlorides is apt to be produced when acetylene comes into contact with free
chlorine, and the reaction sometimes proceeds with explosive violence. The
earliest writers, such as E. Davy, Wöhler, and Berthelot, stated that an
addition of chlorine to acetylene was invariably followed by an explosion,
unless the mixture was protected from light; whilst later investigators
thought the two gases could be safely mixed if they were both pure, or if air
was absent. Owing to the conflicting nature of the statements made,
Nieuwland determined in 1905 to study the problem afresh; and the
annexed account is chiefly based on his experiments, which, however, still
fail satisfactorily to elucidate all the phenomena observed. According to
Nieuwland's results, the behaviour of mixtures of acetylene and chlorine

Page 247

appears capricious, for sometimes the gases unite quietly, although
sometimes they explode. Acetylene and chlorine react quite quietly in the
dark and at low temperatures; and neither a moderate increase in
temperature, nor the admission of diffused daylight, nor the introduction of
small volumes of air, is necessarily followed by an explosion. Doubtless the
presence of either light, air, or warmth increases the probability of an
explosive reaction, while it becomes more probable still in their joint
presence; but in given conditions the reaction may suddenly change from a
gentle formation of addition products to a violent formation of substitution
products without any warning or manifest cause. When the gases merely
unite quietly, tetrachlorethane, or acetylene tetrachloride, is produced thus:

C_2H_2 + 2Cl_2 = C_2H_2Cl_4;

but when the reaction is violent some hexachlorethane is formed,
presumably thus:

2C_2H_2 + 5Cl_2 = 4HCl + C_2 + C_2Cl_6.

The heat evolved by the decomposition of the acetylene by the formation of
the hydrochloric acid in the last equation is then propagated amongst the
rest of the gaseous mixture, accelerating the action, and causing the
acetylene to react with the chlorine to form more hydrochloric acid and free
carbon thus;

C_2H_2 + Cl_2 = 2HCl + C_2.

It is evident that these results do not altogether explain the mechanism of
the reactions involved. Possibly the formation of substitution products and
the consequent occurrence of an explosion is brought about by some foreign
substance which acts as a catalytic agent. Such substance may conceivably
be one of the impurities in crude acetylene, or the solid matter of a
bleaching-powder purifying material. The experiments at least indicate the
direction in which safety may be sought when bleaching- powder is
employed to purify the crude gas, viz., dilution of the powder with an inert
material, absence of air from the gas, and avoidance of bright sunlight in the
place where a spent purifier is being emptied. Unfortunately Nieuwland did
not investigate the action on acetylene of hypochlorites, which are

Page 248

presumably the active ingredients in bleaching- powder. As will appear in
due course, processes have been devised and patented to eliminate all
danger from the reaction between acetylene and chlorine for the purpose of
making tetrachlorethane in quantity.

Acetylene combines with hydrogen in the presence of platinum black, and
ethylene and then ethane result. It was hoped at one time that this reaction
would lead to the manufacture of alcohol from acetylene being achieved on
a commercial basis; but it was found that it did not proceed with sufficient
smoothness for the process to succeed, and a number of higher or
condensation products were formed at the same time. It has been shown by
Erdmann that the cost of production of alcohol from acetylene through this
reaction must prove prohibitive, and he has indicated another reaction
which he considered more promising. This is the conversion of acetylene by
means of dilute sulphuric acid (3 volumes of concentrated acid to 7
volumes of water), preferably in the presence of mercuric oxide, to
acetaldehyde. The yield, however, was not satisfactory, and the process does
not appear to have passed beyond the laboratory stage.

It has also been proposed to utilise the readiness with which acetylene
polymerises on heating to form benzene, for the production of benzene
commercially; but the relative prices of acetylene and benzene would have
to be greatly changed from those now obtaining to make such a scheme
successful. Acetylene also lends itself to the synthesis of phenol or carbolic
acid. If the dry gas is passed slowly into fuming sulphuric acid, a sulpho-
derivative results, of which the potash salt may be thrown down by means
of alcohol. This salt has the formula C_2H_4O_2,S_2O_6K_2, and on
heating it with caustic potash in an atmosphere of hydrogen, decomposing
with excess of sulphuric acid, and distilling, phenol results and may be
isolated. The product is, however, generally much contaminated with
carbon, and the process, which was devised by Berthelot, does not appear to
have been pursued commercially. Berthelot has also investigated the action
of ordinary concentrated sulphuric acid on acetylene, and obtained various
sulphonic derivatives. Schröter has made similar investigations on the
action of strongly fuming sulphuric acid on acetylene. These investigations
have not yet acquired any commercial significance.

Page 249

If a mixture of acetylene with either of the oxides of carbon is led through a
red-hot tube, or if a similar mixture is submitted to the action of electric
sparks when confined within a closed vessel at some pressure, a
decomposition occurs, the whole of the carbon is liberated in the free state,
while the hydrogen and oxygen combine to form water. Analogous
reactions take place when either oxide of carbon is led over calcium carbide
heated to a temperature of 200° or 250° C., the second product in this case
being calcium oxide. The equations representing these actions are:

C_2H_2 + CO = H_2O + 3C

2C_2H_2 + CO_2 = 2H_2O + 5C

CaC_2 + CO = CaO + 3C

2CaC_2 + CO_2 = 2CaO + 5C

By urging the temperature, or by increasing the pressure at which the gases
are led over the carbide, the free carbon appears in the graphitic condition;
at lower temperatures and pressures, it is separated in the amorphous state.
These reactions are utilised in Frank's process for preparing a carbon
pigment or an artificial graphite (cf. Chapter XII.).

Parallel decompositions occur between carbon bisulphide and either
acetylene or calcium carbide, all the carbon of both substances being
eliminated, while the by-product is either sulphuretted hydrogen or calcium
(penta) sulphide. Other organic bodies containing sulphur are decomposed
in the same fashion, and it has been suggested by Ditz that if carbide could
be obtained at a suitable price, the process might be made useful in
removing sulphur (i.e., carbon bisulphide and thiophen) from crude benzol,
in purifying the natural petroleum oil which contains sulphur, and possibly
in removing "sulphur compounds" from coal-gas.

COMPOUNDS WITH COPPER. By far the most important chemical
reactions of acetylene in connexion with its use as an illuminant or fuel are
those which it undergoes with certain metals, notably copper. It is known
that if acetylene comes in contact with copper or with one of its salts, in
certain conditions a compound is produced which, at least when dry, is

Page 250

highly explosive, and will detonate either when warmed or when struck or
gently rubbed. The precise mechanism of the reaction, or reactions, between
acetylene and copper (or its compounds), and also the character of the
product, or products, obtained have been studied by numerous investigators;
but their results have been inconclusive and sometimes rather contradictory,
so that it can hardly be said that the conditions which determine or preclude
the formation of an explosive compound and the composition of the
explosive compound are yet known with certainty. Copper is a metal which
yields two series of compounds, cuprous and cupric salts, the latter of
which contain half the quantity of metal per unit of acid constituent that is
found in the former. It should follow, therefore, that there are two
compounds of copper with carbon, or copper carbides: cuprous carbide,
Cu_2C_2, and cupric carbide, CuC_2. Acetylene reacts at ordinary
temperatures with an ammoniacal solution of any cupric salt, forming a
black cupric compound of uncertain constitution which explodes between
50° and 70° C. It is decomposed by dilute acids, yielding some polymerised
substances. At more elevated temperatures other cupric compounds are
produced which also give evidence of polymerisation. Cuprous carbide or
acetylide is the reddish brown amorphous precipitate which is the ultimate
product obtained when acetylene is led into an ammoniacal solution of
cuprous chloride. This body is decomposed by hydrochloric acid, yielding
acetylene; but of itself it is, in all probability, not explosive. Cuprous
carbide, however, is very unstable and prone to oxidation; so that, given the
opportunity, it combines with oxygen or hydrogen, or both, until it produces
the copper acetylide, or acetylene-copper, which is explosive--a body to
which Blochmann's formula C_2H_2Cu_2O is generally ascribed. Thus it
should happen that the exact nature of the copper acetylene compound may
vary according to the conditions in which it has been formed, from a
substance that is not explosive at all at first, to one that is violently
explosive; and the degree of explosiveness should depend on the greater
exposure of the compound to air and moisture, or the larger amount of
oxygen and moisture in the acetylene during its contact with the copper or
copper salt. For instance, Mai has found that freshly made copper acetylide
can be heated to 60° C. or higher without explosion; but that if the
compound is exposed to air for a few hours it explodes on warming, while
if warmed with oxygen it explodes on contact with acetylene. It is said by
Mai and by Caro to absorb acetylene when both substances are dry,

Page 251

becoming so hot as to explode spontaneously. Freund and Mai have also
observed that when copper acetylide which has been dried in contact with
air for four or five hours at a temperature of 50° or 60° C. is allowed to
explode in the presence of a current of acetylene, an explosion accompanied
by light takes place; but it is always local and is not communicated to the
gas, whether the latter is crude or pure. In contact with neutral or acid
solutions of cuprous salts acetylene yields various double compounds
differing in colour and crystallising power; but according to Chavastelon
and to Caro they are all devoid of explosive properties. Sometimes a
yellowish red precipitate is produced in solutions of copper salts containing
free acid, but the deposit is not copper acetylide, and is more likely to be, at
least in part, a copper phosphide--especially if the gas is crude. Hence acid
solutions or preparations of copper salts may safely be used for the
purification of acetylene, as is done in the case of frankoline, mentioned in
Chapter V. It is clear that the amount of free acid in such a material is much
more than sufficient to neutralise all the ammonia which may accompany
the crude acetylene into the purifier until the material is exhausted in other
respects; and moreover, in the best practice, the gas would have been
washed quite or nearly free from ammonia before entering the purifier.

From a practical aspect the possible interaction of acetylene and metallic
copper has been investigated by Gerdes and by Grittner, whose results,
again, are somewhat contradictory. Gerdes exposed neat acetylene and
mixtures of acetylene with oil-gas and coal-gas to a pressure of nine or ten
atmospheres for ten months at ordinary summer and winter temperatures in
vessels made of copper and various alloys. Those metals and alloys which
resisted oxidation in air resisted the attack of the gases, but the more
corrodible substances were attacked superficially; although in no instance
could an explosive body be detected, nor could an explosion be produced
by heating or hammering. In further experiments the acetylene contained
ammonia and moisture and Gerdes found that where corrosion took place it
was due exclusively to the ammonia, no explosive compounds being
produced even then. Grittner investigated the question by leading acetylene
for months through pipes containing copper gauze. His conclusions are that
a copper acetylide is always produced if impure acetylene is allowed to pass
through neutral or ammoniacal solutions of copper; that dry acetylene
containing all its natural impurities except ammonia acts to an equal extent

Page 252

on copper and its alloys, yielding the explosive compound; that pure and
dry gas does not act upon copper or its alloys, although it is possible that an
explosive compound may be produced after a great length of time. Grittner
has asserted that an explosive compound may be produced when acetylene
is brought into contact with such alloys of copper as ordinary brass
containing 64.66 per cent. of copper, or red brass containing 74.46 per cent.
of copper, 20.67 per cent. of zinc, and 4.64 per cent. of tin; whereas none is
obtained when the metal is either "alpaca" containing 64.44 per cent. of
copper, 18.79 per cent. of nickel, and 16.33 per cent. of zinc, or britannia
metal composed of 91.7 per cent. of copper and 8.3 per cent. of tin. Caro
has found that when pure dry acetylene is led for nine months over sheets or
filings of copper, brass containing 63.2 per cent. of copper, red brass
containing 73.8 per cent., so-called "alpaca-metal" containing 65.3 per
cent., and britannia metal containing 90.2 per cent. of copper, no action
whatever takes place at ordinary temperatures; if the gas is moist very small
quantities of copper acetylide are produced in six months, whatever metal is
tested, but the yield does not increase appreciably afterwards. At high
temperatures condensation occurs between acetylene and copper or its
alloys, but explosive bodies are not formed.

Grittner's statement that crude acetylene, with or without ammonia, acts
upon alloys of copper as well as upon copper itself, has thus been
corroborated by Caro; but experience renders it tolerably certain that brass
(and presumably gun-metal) is not appreciably attacked in practical
conditions. Gerdes' failure to obtain an explosive compound in any
circumstances may very possibly be explained by the entire absence of any
oxygen from his cylinders and gases, so that any copper carbide produced
remained unoxidised. Grittner's gas was derived, at least partially, from a
public acetylene supply, and is quite likely to have been contaminated with
air in sufficient quantity to oxidise the original copper compound, and to
convert it into the explosive modification.

For the foregoing reasons the use of unalloyed copper in the construction of
acetylene generators or in the subsidiary items of the plant, as well as in
burner fittings, is forbidden by statute or some quasi-legal enactment in
most countries, and in others the metal has been abandoned for one of its
alloys, or for iron or steel, as the case may be. Grittner's experiments

Page 253

mentioned above, however, probably explain why even alloys of copper are
forbidden in Hungary. (Cf. Chapter IV., page 127.)

When acetylene is passed over finely divided copper or iron (obtained by
reduction of the oxide by hydrogen) heated to from 130° C. to 250° C., the
gas is more or less completely decomposed, and various products, among
which hydrogen predominates, result. Ethane and ethylene are undoubtedly
formed, and certain homologues of them and of acetylene, as well as
benzene and a high molecular hydrocarbon (C_7H_6)_n termed "cuprene,"
have been found by different investigators. Nearly the same hydrocarbons,
and others constituting a mixture approximating in composition to some
natural petroleums, are produced when acetylene is passed over heated
nickel (or certain other metals) obtained by the reduction of the finely
divided oxide. These observations are at present of no technical importance,
but are interesting scientifically because they have led up to the
promulgation of a new theory of the origin of petroleum, which, however,
has not yet found universal acceptance.

Page 254

CHAPTER VII
MAINS AND SERVICE-PIPES--SUBSIDIARY APPARATUS

The process by which acetylene is produced, and the methods employed for
purifying it and rendering it fit for consumption in dwelling-rooms, having
been dealt with in the preceding pages, the present chapter will be devoted
to a brief account of those items in the plant which lie between the purifier
outlet and the actual burner, including the meter, governor, and pressure
gauge; the proper sizes of pipe for acetylene; methods of laying it, joint-
making, quality of fittings, &c.; while finally a few words will be said about
the precautions necessary when bringing a new system of pipes into use for
the first time.

THE METER.--A meter is required either to control the working of a
complete acetylene installation or to measure the volume of gas passing
through one particular pipe, as when a number of consumers are supplied
through separate services under agreement from a central supply plant. The
control which may be afforded by the inclusion of a meter in the equipment
of a domestic acetylene generating plant is valuable, but in practice will
seldom be exercised. The meter records check the yield of gas from the
carbide consumed in a simple and trustworthy manner, and also serve to
indicate when the material in the purifier is likely to be approaching
exhaustion. The meter may also be used experimentally to check the
soundness of the service-pipes or the consumption of a particular burner or
group of burners. Altogether it may be regarded as a useful adjunct to a
domestic lighting plant, provided full advantage is taken of it. If, however,
there is no intention to pay systematic attention to the records of the meter,
it is best to omit it from such an installation, and so save its initial cost and
the slight loss of pressure which its use involves on the gas passing through
it. A domestic acetylene lighting plant can be managed quite satisfactorily
without a meter, and as a multiplication of parts is undesirable in an
apparatus which will usually be tended by someone not versed in technical
operations, it is on the whole better to omit the meter in such an installation.

Page 255

Where the plant is supervised by a technical man, a meter may advisedly be
included in the equipment. Its proper position in the train of apparatus is
immediately after the purifier. A meter must not be used for unpurified or
imperfectly purified acetylene, because the impurities attack the internal
metallic parts and ultimately destroy them. The supply of acetylene to
various consumers from a central generating station entails the fixing of a
meter on each consumer's service-pipe, so that the quantity consumed by
each may be charged for accordingly, just as in the case of public coal-gas
supplies.

There are two types of gas-meter in common use, either of which may,
without essential alteration, be employed for measuring the volume of
acetylene passing through a pipe. It is unnecessary to refer here at length to
their internal mechanism, because their manufacture by other than firms of
professed meter-makers is out of the question, and the user will be justified
in accepting the mechanism as trustworthy and durable. Meters can always
be had stamped with the seal of a local authority or other body having duly
appointed inspectors under the Sales of Gas Act, and the presence of such a
stamp on a meter implies that it has been officially examined and found to
register quantities accurately, or not varying beyond 2 per cent. in favour of
the seller, or 3 per cent, in favour of the consumer. [Footnote: It may be
remarked that when a meter-- wet or dry--begins to register incorrectly by
reason of old age or want of adjustment, its error is very often in the
direction that benefits the customer, i.e., more gas passes through it than the
dials record.] Hence a "stamped" meter may be regarded for practical
purposes as affording a correct register of the quantities of gas passing
through it.

Except that the use of unalloyed copper in any part of the meter where it
may come in contact with the gas must be wholly avoided, for the reason
that copper is inadmissible in acetylene apparatus (see Chapter VI.), the
meters ordinarily employed for coal-gas serve quite well for acetylene.
Obviously, however, since so very much less acetylene than coal-gas is
consumed per burner, comparatively small meters only will be required
even for large installations of acetylene lighting. This fact is now
recognised by meter-makers, and meters of all suitable sizes can be
obtained. It is desirable, if an ordinary coal-gas meter is being bought for

Page 256

use with acetylene, to have it subjected to a somewhat more rigorous test
for soundness than is customary before "stamping" but the makers would
readily be able to carry out this additional test.

The two types of gas-meter are known as "wet" and "dry." The case of the
wet meter is about hall-filled with water or other liquid, the level of which
has to be maintained nearly constant. Several ingenious devices are in use
for securing this constancy of level over a more or less extended period, but
the necessity for occasional inspection and adjustment of the water-level,
coupled with the stoppage of the passage of gas in the event of the water
becoming frozen, are serious objections to the employment of the wet meter
in many situations. The trouble of freezing may be avoided by substituting
for the simple water an aqueous solution of glycerin, or mixture of glycerin
with water, suitable strengths for which may be deduced from the table
relating to the use of glycerin in holder seals given at the close of Chapter
III. The dry meter, on the other hand, is very convenient, because it is not
obstructed by the effects of frost, and because it acts for years without
requiring attention. It is not susceptible of adjustment for measuring with so
high a degree of accuracy as a good wet meter, but its indications are
sufficiently correct to fall well within the legalised deviations already
mentioned. Such errors, perhaps, are somewhat large for so costly and
powerful a gas as acetylene, and they would be better reduced; but it is not
so very often that a dry meter reaches its limit of inaccuracy. Whether wet
or dry, the meter should be fixed in a place where the temperature is
tolerably uniform, otherwise the volumes registered at different times will
not bear the same ratio to the mass of gas (or volume at normal
temperature), and the registrations will be misleading unless troublesome
corrections to compensate for changes of temperature are applied.

THE GOVERNOR, which can be dispensed with in most ordinary domestic
acetylene lighting installations provided with a good gasholder of the
rising-bell type, is designed to deliver the acetylene to a service-pipe at a
uniform pressure, identical with that under which the burners develop their
maximum illuminating efficiency. It must therefore both cheek the pressure
anterior to it whenever that is above the determined limit to which it is set,
and deliver to the efferent service-pipe acetylene at a constant pressure
whether all or any number of the burners down to one only are in use.

Page 257

Moreover, when the pressure anterior to the governor falls to or below the
determined limit, the governor should offer no resistance--entailing a loss of
pressure to the passage of the acetylene. These conditions, which a perfect
governor should fulfil, are not absolutely met by any simple apparatus at
present in use, but so far as practical utility is concerned service governors
which are readily obtainable are sufficiently good. They are broadly of two
types, viz., those having a bell floating in a mercury seal, and those having
a diaphragm of gas-tight leather or similar material, either the bell or the
diaphragm being raised by the pressure of the gas. The action is essentially
the same in both cases: the bell or the diaphragm is so weighted that when
the pressure of the gas exceeds the predetermined limit the diaphragm or
bell is lifted, and, through an attached rod and valve, brings about a partial
closure of the orifice by which the gas flows into the bell or the diaphragm
chamber. The valve of the governor, therefore, automatically throttles the
gas-way more or less according to the difference in pressure before and
after the apparatus, until at any moment the gas-way is just sufficient in area
to pass the quantity of gas which any indefinite number of burners require
at their fixed working pressure; passing it always at that fixed working
pressure irrespective of the number of burners, and maintaining it constant
irrespective of the amount of pressure anterior to the governor, or of any
variations in that anterior pressure. In most patterns of service governor
weights may be added when it is desired to increase the pressure of the
effluent gas. It is necessary, in ordering a governor for an acetylene-supply,
to state the maximum number of cubic feet per hour it will be required to
pass, and approximately the pressure at which it will be required to deliver
the gas to the service-pipe. This will usually be between 3 and 5 inches
(instead of about 1 inch in the case of coal-gas), and if the anterior pressure
is likely to exceed 10 inches, this fact should be stated also. The mercury-
seal governors are usually the more trustworthy and durable, but they are
more costly than those with leather diaphragms. The seal should have twice
or thrice the depth it usually has for coal-gas. The governor should be
placed where it is readily accessible to the man in charge of the installation,
but where it will not be interfered with by irresponsible persons. In large
installations, where a number of separate buildings receive service-pipes
from one long main, each service-pipe should be provided with a governor.

Page 258

GASHOLDER PRESSURE.--In drawing up the specification or scheme of
an acetylene installation, it is frequently necessary either to estimate the
pressure which a bell gasholder of given diameter and weight will throw, or
to determine what should be the weight of the bell of a gasholder of given
diameter when the gas is required to be delivered from it at a particular
pressure. The gasholder of an acetylene installation serves not only to store
the gas, but also to give the necessary pressure for driving it through the
posterior apparatus and distributing mains and service-pipes. In coal-gas
works this office is generally given over wholly or in part to a special
machine, known as the exhauster, but this machine could not be
advantageously employed for pumping acetylene unless the installation
were of very great magnitude. Since, therefore, acetylene is in practice
always forced through mains and service-pipes in virtue of the pressure
imparted to it by the gasholder and since, for reasons already given, only
the rising-bell type of gasholder can be regarded as satisfactory, it becomes
important to know the relations which subsist between the dimensions and
weight of a gasholder bell and the pressure which it "throws" or imparts to
the contained gas.

The bell must obviously be a vessel of considerable weight if it is to
withstand reasonable wear and tear, and this weight will give a certain
hydrostatic pressure to the contained gas. If the weight of the bell is known,
the pressure which it will give can be calculated according to the general
law of hydrostatics, that the weight of the water displaced must be equal to
the weight of the floating body. Supposing for the moment that there are no
other elements which will have to enter into the calculation, then if d is the
diameter in inches of the (cylindrical) bell, the surface of the water
displaced will have an area of d^2 x 0.7854. If the level of the water is
depressed p inches, then the water displaced amounts to p(d^2 x 0.7854)
cubic inches, and its weight will be (at 62° F.):

(0.7854pd^2 x 0.03604) = 0.028302pd^2 lb.

Consequently a bell which is d inches in diameter, and gives a pressure of p
inches of water, will weigh 0.028302pd^2 lb. Or, if W = the weight of the
bell in lb., the pressure thrown by it will be W/0.028302d^2 or
35.333W/d^2. This is the fundamental formula, which is sometimes given

Page 259

as p = 550W/d^2, in which W = the weight of the bell in tons, and d the
diameter in feet. This value of p, however, is actually higher than the holder
would give in practice. Reductions have to be made for two influences, viz.,
the lifting power of the contained gas, which is lighter than air, and the
diminution in the effective weight of so much of the bell as is immersed in
water. The effect of these influences was studied by Pole, who in 1839 drew
up some rules for calculating the pressure thrown by a gasholder of given
dimensions and weight. These rules form the basis of the formula which is
commonly used in the coal-gas industry, and they may be applied, mutatis
mutandis, to acetylene holders. The corrections for both the influences
mentioned vary with the height at which the top of the gasholder bell stands
above the level of the water in the tank. Dealing first with the correction for
the lifting power of the gas, this, according to Pole, is a deduction of h(1 -
d)/828 where d is the specific gravity of the gas and h the height (in inches)
of the top of the gasholder above the water level. This strictly applies only
to a flat-topped bell, and hence if the bell has a crown with a rise equal to
about 1/20 of the diameter of the bell, the value of h here must be taken as
equal to the height of the top of the sides above the water-level (= h'), plus
the height of a cylinder having the same capacity as the crown, and the
same diameter as the bell, that is to say, h=h' + d/40 where d = the diameter
of the bell. The specific gravity of commercially made acetylene being
constantly very nearly 0.91, the deduction for the lifting power of the gas
becomes, for acetylene gasholders, 0.0001086h + 0.0000027d, where h is
the height in inches of the top of the sides of the bell above the water- level,
and d is the diameter of the bell. Obviously this is a negligible quantity, and
hence this correction may be disregarded for all acetylene gasholders,
whereas it is of some importance with coal-gas and other gases of lower
specific gravity. It is therefore wrong to apply to acetylene gasholders
formulæ in which a correction for the lifting power of the gas has been
included when such correction is based on the average specific gravity of
coal-gas, as is the case with many abbreviated gasholder pressure formulæ.

The correction for the immersion of the sides of the bell is of greater
magnitude, and has an important practical significance. Let H be the total
height in inches of the side of the gasholder, h the height in inches of the
top of the sides of the gasholder above the water-level, and w = the weight
of the sides of the gasholder in lb.; then, for any position of the bell, the

Page 260

proportion of the total height of the sides immersed (H - h)/H, and the
buoyancy is (H - h)/H x w/S + pi/4d^2, in which S = the specific gravity of
the material of which the bell is made. Assuming the material to be mild
steel or wrought iron, having a specific gravity of 7.78, the buoyancy is
(4w(H - h)) / (7.78Hpid^2) lb. per square inch (d being inches and w lb.),
which is equivalent to (4w(H - h)) / (0.03604 x 7.78Hpid^2) = (4.54w(H -
h)) / (Hd^2) inches of water. Hence the complete formula for acetylene
gasholders is:

p = 35.333W / d^2 - 4.54w(H - h) / Hd^2

It follows that p varies with the position of the bell, that is to say, with the
extent to which it is filled with gas. It will be well to consider how great this
variation is in the case of a typical acetylene holder, as, if the variation
should be considerable, provision must be made, by the employment of a
governor on the outlet main or otherwise, to prevent its effects being felt at
the burners.

Now, according to the rules of the "Acetylen-Verein" (cf. Chapter IV.), the
bells of holders above 53 cubic feet in capacity should have sides 1.5 mm.
thick, and crowns 0.5 mm. thicker. Hence for a holder from 150 to 160
cubic feet capacity, supposing it to be 4 feet in diameter and about 12 feet
high, the weight of the sides (say of steel No. 16 S.W.G. = 2.66 lb. per
square foot) will be not less than 12 x 4pi x 2.66 = 401 lb. The weight of the
crown (say of steel No. 14 S.W.G. = 3.33 lb. per square foot) will be not
less than about 12.7 x 3.33 = about 42 lb. Hence the total weight of holder =
401 + 42 = 443 lb. Then if the holder is full, h is very nearly equal to H, and
p = (35.333 x 443) / 48^2 = 6.79 inches. If the holder stands only 1 foot
above the water-level, then p = 6.79 - (4.54 x 401 (144 - 12)) / (144 x 48^2)
= 6.79 - 0.72 = 6.07 inches. The same result can be arrived at without the
direct use of the second member of the formula:

For instance, the weight of the sides immersed is 11 x 4pi x 2.66 = 368 lb.,
and taking the specific gravity of mild steel at 7.78, the weight of water
displaced is 368 / 7.78 = 47.3 lb. Hence the total effective weight of the bell
is 443 - 47.3 = 395.7 lb., and p = (35.333 x 395.7) / 48^2 = 6.07 inches.
[Footnote: If the sealing liquid in the gasholder tank is other than simple
water, the correction for the immersion of the sides of the bell requires

Page 261

modification, because the weight of liquid displaced will be s' times as great
as when the liquid is water, if s' is the specific gravity of the sealing liquid.
For instance, in the example given, if the sealing liquid were a 16 per cent.
solution of calcium chloride, specific gravity 1.14 (vide p. 93) instead of
water, the weight of liquid displaced would be 1.14 (368 / 7.78) = 53.9 lb.,
and the total effective weight of the bell = 443 - 53.9 = 389.1 lb. Therefore
p becomes = (35.333 x 389.1) / 48^2 = 5.97 inches, instead of 6.07 inches.]

The value of p for any position of the bell can thus be arrived at, and if the
difference between its values for the highest and for the lowest positions of
the bell exceeds 0.25 inch, [Footnote: This figure is given as an example
merely. The maximum variation in pressure must be less than one capable
of sensibly affecting the silence, steadiness, and economy of the burners
and stoves, &c., connected with the installation.] a governor should be
inserted in the main leading from the holder to the burners, or one of the
more or less complicated devices for equalising the pressure thrown by a
holder as it rises and falls should be added to the holder. Several such
devices were at one time used in connexion with coal-gas holders, and it is
unnecessary to describe them in this work, especially as the governor is
practically the better means of securing uniform pressure at the burners.

It is frequently necessary to add weight to the bell of a small gasholder in
order to obtain a sufficiently high pressure for the distribution of acetylene.
It is best, having regard to the steadiness of the bell, that any necessary
weighting of it should be done near its bottom rim, which moreover is
usually stiffened by riveting to it a flange or curb of heavier gauge metal.
This flange may obviously be made sufficiently stout to give the requisite
additional weighting. As the flange is constantly immersed, its weight must
not be added to that of the sides in computing the value of w for making the
correction of pressure in respect of the immersion of the bell. Its effective
weight in giving pressure to the contained gas is its actual weight less its
actual weight divided by its specific gravity (say 7.2 for cast iron, 7.78 for
wrought iron or mild steel, or 11.4 for lead). Thus if x lb. of steel is added to
the rim its weight in computing the value of W in the formula p = 35.333W
/ d^2 should be taken as x - x / 7.78. If the actual weight is 7.78 lb., the
weight taken for computing W is 7.78 - 1 = 6.78 lb.

Page 262

THE PRESSURE GAUGE.--The measurement of gas pressure is effected
by means of a simple instrument known as a pressure gauge. It comprises a
glass U- tube filled to about half its height with water. The vacant upper
half of one limb is put in communication with the gas-supply of which the
pressure is to be determined, while the other limb remains open to the
atmosphere. The difference then observed, when the U-tube is held vertical,
between the levels of the water in the two limbs of the tube indicates the
difference between the pressure of the gas-supply and the atmospheric
pressure. It is this difference that is meant when the pressure of a gas in a
pipe or piece of apparatus is spoken of, and it must of necessity in the case
of a gas-supply have a positive value. That is to say, the "pressure" of gas in
a service-pipe expresses really by how much the pressure in the pipe
exceeds the atmospheric pressure. (Pressures less than the atmospheric
pressure will not occur in connexion with an acetylene installation, unless
the gasholder is intentionally manipulated to that end.) Gas pressures are
expressed in terms of inches head or pressure of water, fractions of an inch
being given in decimals or "tenths" of an inch. The expression "tenths" is
often used alone, thus a pressure of "six-tenths" means a pressure equivalent
to 0.6 inch head of water.

The pressure gauge is for convenience provided with an attached scale on
which the pressures may be directly read, and with a connexion by which
the one limb is attached to the service-pipe or cock where the pressure is to
be observed. A portable gauge of this description is very useful, as it can be
attached by means of a short piece of flexible tubing to any tap or burner.
Several authorities, including the British Acetylene Association, have
recommended that pressure gauges should not be directly attached to
generators, because of the danger that the glass might be fractured by a
blow or by a sudden access of heat. Such breakage would be followed by an
escape of gas, and might lead to an accident. Fixed pressure gauges,
however, connected with every item of a plant are extremely useful, and
should be employed in all large installations, as they afford great aid in
observing and controlling the working, and in locating the exact position of
any block. All danger attending their use can be obviated by having a
stopcock between the gauge inlet and the portion of the plant to which it is
attached; the said stopcock being kept closed except when it is momentarily
opened to allow of a reading being taken. As an additional precaution

Page 263

against its being left open, the stopcock may be provided with a weight or
spring which automatically closes the gas-way directly the observer's hand
is removed from the tap. In the best practice all the gauges will be collected
together on a board fastened in some convenient spot on the wall of the
generator-house, each gauge being connected with its respective item of the
plant by means of a permanent metallic tube. The gauges must be filled
with pure water, or with a liquid which does not differ appreciably in
specific gravity from pure water, or the readings will be incorrect. Greater
legibility will be obtained by staining the water with a few drops of caramel
solution, or of indigo sulphate (indigo carmine); or, in the absence of these
dyes, with a drop or two of common blue-black writing ink. If they are not
erected in perfectly frost-free situations, the gauges may be filled with a
mixture of glycerin and pure alcohol (not methylated spirit), with or without
a certain proportion of water, which will not freeze at any winter
temperature. The necessary mixture, which must have a density of exactly
1.00, could be procured from any pharmacist.

It is the pressure as indicated by the pressure gauge which is referred to in
this book in all cases where the term "pressure of the gas" or the like is
used. The quantity of acetylene which will flow in a given time from the
open end of a pipe is a function of this pressure, while the quantity of
acetylene escaping through a tiny hole or crack or a burner orifice also
depends on this total pressure, though the ratio in this instance is not a
simple one, owing to the varying influence of friction between the issuing
gas and the sides of the orifice. Where, however, acetylene or other gas is
flowing through pipes or apparatus there is a loss of energy, indicated by a
falling off in the pressure due to friction, or to the performance of work,
such as actuating a gas-meter. The extent of this loss of energy in a given
length of pipe or in a meter is measured by the difference between the
pressures of the gas at the two ends of the pipe or at the inlet and outlet of
the meter. This difference is the "loss" or "fall" of pressure, due to friction
or work performed, and is spoken of as the "actuating" pressure in regard to
the passage of gas through the stretch of pipe or meter. It is a measure of the
energy absorbed in actuating the meter or in overcoming the friction. (Cf.
footnote, Chapter II., page 54.)

Page 264

DIMENSIONS OF MAINS.--The diameter of the mains and service-pipes
for an acetylene installation must be such that the main or pipe will convey
the maximum quantity of the gas likely to be required to feed all the burners
properly which are connected to it, without an excessive actuating pressure
being called for to drive the gas through the main or pipe. The flow of all
gases through pipes is of course governed by the same general principles;
and it is only necessary in applying these principles to a particular gas, such
as acetylene, to know certain physical properties of the gas and to make due
allowance for their influence. The general principles which govern the flow
of a gas through pipes have been exhaustively studied on account of their
importance in relation to the distribution of coal-gas and the supply of air
for the ventilation of places where natural circulation is absent or deficient.
It will be convenient to give a very brief reference to the way in which these
principles have been ascertained and applied, and then to proceed to the
particular case of the distribution of acetylene through mains and service-
pipes.

The subject of "The Motion of Fluids in Pipes" was treated in a lucid and
comprehensive manner in an Essay by W. Pole in the Journal of Gas
Lighting during 1852, and his conclusions have been generally adopted by
gas engineers ever since. He recapitulated the more important points of this
essay in the course of some lectures delivered in 1872, and one or other of
these two sources should be consulted for further information. Briefly, W.
Pole treated the question in the following manner:

The practical question in gas distribution is, what quantity of gas will a
given actuating pressure cause to flow along a pipe of given length and
given diameter? The solution of this question allows of the diameters of
pipes being arranged so that they will carry a required quantity of gas a
given distance under the actuating pressure that is most convenient or
appropriate. There are five quantities to be dealt with, viz.:

(1) The length of pipe = l feet.

(2) The internal diameter of the pipe = d inches.

(3) The actuating pressure = h inches of head of water. (4) The specific
gravity or density of the gas = d times that of air.

Page 265

(5) The quantity of gas passing through the pipe--Q cubic feet per hour.
This quantity is the product of the mean velocity of the gas in the pipe and
the area of the pipe.

The only work done in maintaining the flow of gas along a pipe is that
required to overcome the friction of the gas on the walls of the pipe, or,
rather, the consequential friction of the gas on itself, and the laws which
regulate such friction have not been very exhaustively investigated. Pole
pointed out, however, that the existing knowledge on the point at the time
he wrote would serve for the purpose of determining the proper sizes of
gas-mains. He stated that the friction (1) is proportional to the area of
rubbing surface (viz., pild); (2) varies with the velocity, in some ratio
greater than the first power, but usually taken as the square; and (3) is
assumed to be proportional to the specific gravity of the fluid (viz., s).

Thus the force (f) necessary to maintain the motion of the gas in the pipe is
seen to vary (1) as pild, of which pi is a constant; (2) as v^2, where v = the
velocity in feet per hour; and (3) as s. Hence, combining these and deleting
the constant pi, it appears that

f varies as ldsv^2.

Now the actuating force is equal to f, and is represented by the difference of
pressure at the two ends of the pipe, i.e., the initial pressure, viz., that at the
place whence gas is distributed or issues from a larger pipe will be greater
by the quantity f than the terminal pressure, viz., that at the far end of the
pipe where it branches or narrows to a pipe or pipes of smaller size, or
terminates in a burner. The terminal pressure in the case of service-pipes
must be settled, as mentioned in Chapter II., broadly according to the
pressure at which the burners in use work best, and this is very different in
the case of flat-flame burners for coal-gas and burners for acetylene. The
most suitable pressure for acetylene burners will be referred to later, but
may be taken as equal to p_0 inches head of water. Then, calling the initial
pressure (i.e., at the inlet head of service-pipe) p_1, it follows that p_1 - p_0
= f. Now the cross-section of the pipe has an area (pi/4)d^2, and if h
represents the difference of pressure between the two ends of the pipe per
square inch of its area, it follows that f = h(pi/4)d^2. But since f has been
found above to vary as ldsv^2 , it is evident that

Page 266

h(pi/4)d^2 varies as ldsv^2.

Hence

v^2 varies as hd/ls, and putting in some constant M, the value of which must
be determined by experiment, this becomes

v^2 = Mhd/ls.

The value of M deduced from experiments on the friction of coal-gas in
pipes was inserted in this equation, and then taking Q = pi/4d^2v, it was
found that for coal-gas Q = 780(hd/sl)^(1/2)

This formula, in its usual form, is

Q = 1350d^2(hd/sl)^(1/2)

in which l = the length of main in yards instead of in feet. This is known as
Pole's formula, and has been generally used for determining the sizes of
mains for the supply of coal-gas.

For the following reasons, among others, it becomes prudent to revise
Pole's formula before employing it for calculations relating to acetylene.
First, the friction of the two gases due to the sides of a pipe is very different,
the coefficient for coal-gas being 0.003, whereas that of acetylene,
according to Ortloff, is 0.0001319. Secondly, the mains and service-pipes
required for acetylene are smaller, cateria paribus, than those needed for
coal-gas. Thirdly, the observed specific gravity of acetylene is 0.91, that of
air being unity, whereas the density of coal-gas is about 0.40; and therefore,
in the absence of direct information, it would be better to base calculations
respecting acetylene on data relating to the flow of air in pipes rather than
upon such as are applicable to coal-gas. Bernat has endeavoured to take
these and similar considerations into account, and has given the following
formula for determining the sizes of pipes required for the distribution of
acetylene:

Q = 0.001253d^2(hd/sl)^(1/2)

Page 267

in which the symbols refer to the same quantities as before, but the constant
is calculated on the basis of Q being stated in cubic metres, l in metres, and
d and h in millimetres. It will be seen that the equation has precisely the
same shape as Pole's formula for coal-gas, but that the constant is different.
The difference is not only due to one formula referring to quantities stated
on the metric and the other to the same quantities stated on the English
system of measures, but depends partly on allowance having been made for
the different physical properties of the two gases. Thus Bernat's formula,
when merely transposed from the metric system of measures to the English
(i.e., Q being cubic feet per hour, l feet, and d and h inches) becomes

Q = 1313.5d^2(hd/sl)^(1/2)

or, more simply,

Q = 1313.4(hd^5/sl)^(1/2)

But since the density of commercially-made acetylene is practically the
same in all cases, and not variable as is the density of coal-gas, its value,
viz., 0.91, may be brought into the constant, and the formula then becomes

Q = 1376.9(hd^5/l)^(1/2)

Bernat's formula was for some time generally accepted as the most
trustworthy for pipes supplying acetylene, and the last equation gives it in
its simplest form, though a convenient transposition is

d = 0.05552(Q^2l/h)^(1/5)

Bernat's formula, however, has now been generally superseded by one
given by Morel, which has been found to be more in accordance with the
actual results observed in the practical distribution of acetylene. Morel's
formula is

D = 1.155(Q^2l/h)^(1/5)

in which D = the diameter of the pipe in centimetres, Q = the number of
cubic metres of gas passing per hour, l = the length of pipe in metres, and h

Page 268

= the loss of pressure between the two ends of the pipe in millimetres. On
converting tins formula into terms of the English system of measures (i.e., l
feet, Q cubic feet, and h and d inches) it becomes

(i) d = 0.045122(Q^2l/h)^(1/5)

At first sight this formula does not appear to differ greatly from Bernat's,
the only change being that the constant is 0.045122 instead of 0.05552, but
the effect of this change is very great--for instance, other factors remaining
unaltered, the value of Q by Morel's formula will be 1.68 times as much as
by Bernat's formula. Transformations of Morel's formula which may
sometimes be more convenient to apply than (i) are:

(ii) Q = 2312.2(hd^5/l)^(1/2)

(iii) h = 0.000000187011(Q^2l/d^5)

and (iv) l = 5,346,340(hd^5/Q^2)

In order to avoid as far as possible expenditure of time and labour in
repeating calculations, tables have been drawn up by the authors from
Morel's formulæ which will serve to give the requisite information as to the
proper sizes of pipes to be used in those cases which are likely to be met
with in ordinary practice. These tables are given at the end of this chapter.

When dealing with coal-gas, it is highly important to bear in mind that the
ordinary distributing formulæ apply directly only when the pipe or main is
horizontal, and that a rise in the pipe will be attended by an increase of
pressure at the upper end. But as the increase is greater the lower the
density of the gas, the disturbing influence of a moderate rise in a pipe is
comparatively small in the case of a gas of so high a density as acetylene.
Hence in most instances it will be unnecessary to make any allowance for
increase of pressure due to change of level. Where the change is very great,
however, allowance may advisedly be made on the following basis: The
pressure of acetylene in pipes increases by about one-tenth of an inch (head
of water) for every 75 feet rise in the pipe. Hence where acetylene is
supplied from a gasholder on the ground-level to all floors of a house 75
feet high, a burner at the top of the house will ordinarily receive its supply

Page 269

at a pressure greater by one-tenth of an inch than a burner in the basement.
Such a difference, with the relatively high pressures used in acetylene
supplies, is of no practical moment. In the case of an acetylene-supply from
a central station to different parts of a mountainous district, the variations of
pressure with level should be remembered.

The distributing formulæ also assume that the pipe is virtually straight;
bends and angles introduce disturbing influences. If the bend is sharp, or if
there is a right-angle, an allowance should be made if it is desired to put in
pipes of the smallest permissible dimensions. In the case of the most usual
sizes of pipes employed for acetylene mains or services, it will suffice to
reckon that each round or square elbow is equivalent in the resistance it
offers to the flow of gas to a length of 5 feet of pipe of the same diameter.
Hence if 5 feet is added to the actual length of pipe to be laid for every bond
or elbow which will occur in it, and the figure so obtained is taken as the
value of l in formulæ (i), (ii), or (iii), the values then found for Q, d, or h
will be trustworthy for all practical purposes.

It may now be useful to give an example of the manner of using the
foregoing formulæ when the tables of sizes of pipes are not available. Let it
be supposed that an institution is being equipped for acetylene lighting; that
50 burners consuming 0.70 cubic foot, and 50 consuming 1.00 cubic foot of
acetylene per hour may be required in use simultaneously; that a pressure of
at least 2-1/2 inches is required at all the burners; that for sufficient reasons
it is considered undesirable to use a higher distributing pressure than 4
inches at the gasholder, outlet of the purifiers, or initial governor
(whichever comes last in the train of apparatus); that the gasholder is
located 100 feet from the main building of the institution, and that the trunk
supply-pipe through the latter must be 250 feet in length, and the supplies to
the burners, either singly or in groups, be taken from this trunk pipe through
short lengths of tubing of ample size. What should be the diameter of the
trunk pipe, in which it will be assumed that ten bonds or elbows are
necessary?

In the first instance, it is convenient to suppose that the trunk pipe may be
of uniform diameter throughout. Then the value of l will be 100 (from
gasholder to main building) + 250 (within the building) + 50 (equivalent of

Page 270

10 elbows) = 400. The maximum value of Q will be (50 x 0.7) + (50 x 1.0)
= 85; and the value of h will be 1 - 2.5 - 1.5. Then using formula (i), we
have:

d = 0.045122((85^2 x 400)/1.5)^(1/5) = 0.045122(1,926,667)^(1/5)

= 0.045122 x 18.0713 = 0.8154.

The formula, therefore, shows that the pipe should have an internal
diameter of not less than 0.8154 inch, and consequently 1 inch (the next
size above 0.8154 inch) barrel should be used. If the initial pressure (i.e., at
outlet of purifiers) could be conveniently increased from 4 to 4.8 inches, 3/4
inch barrel could be employed for the service-pipe. But if connexions for
burners were made immediately the pipe entered the building, these burners
would then be supplied at a pressure of 4.2 inches, while those on the
extremity of the pipe would, when all burners were in use, be supplied at a
pressure of only 2.5 inches. Such a great difference of pressure is not
permissible at the several burners, as no type of burner retains its proper
efficiency over more than a very limited range of pressure. It is highly
desirable in the case of the ordinary Naphey type of burner that all the
burners in a house should be supplied at pressures which do not differ by
more than half an inch; hence the pipes should, wherever practicable, be of
such a size that they will pass the maximum quantity of gas required for all
the burners which will ever be in use simultaneously, when the pressure at
the first burner connected to the pipe after it enters the house is not more
than half an inch above the pressure at the burner furthermost removed
from the first one, all the burner-taps being turned on at the time the
pressures are observed. If the acetylene generating plant is not many yards
from the building to be supplied, it is a safe rule to calculate the size of
pipes required on the basis of a fall of pressure of only half an inch from the
outlet of the purifiers or initial governor to the farthermost burner. The extra
cost of the larger size of pipe which the application of this rule may entail
will be very slight in all ordinary house installations.

VELOCITY OF FLOW IN PIPES.--For various purposes, it is often
desirable to know the mean speed at which acetylene, or any other gas, is
passing through a pipe. If the diameter of the pipe is d inches, its cross-
sectional area is d^2 x 0.7854 square inches; and since there are 1728 cubic

Page 271

inches in 1 cubic foot, that quantity of gas will occupy in a pipe whose
diameter is d inches a length of

1728/(d^2 x 0.7854) linear inches or 183/d^2^ linear feet.

If the gas is in motion, and the pipe is delivering Q cubic feet per hour,
since there are 3600 seconds of time in one hour, the mean speed of the gas
becomes

183/d^2 x Q/3600 = Q/(19 x 7d^2) linear feet per second.

This value is interesting in several ways. For instance, taking a rough
average of Le Chatelier's results, the highest speed at which the explosive
wave proceeds in a mixture of acetylene and air is 7 metres or 22 feet per
second. Now, even if a pipe is filled with an acetylene-air mixture of utmost
explosibility, an explosion cannot travel backwards from B to A in that pipe,
if the gas is moving from A to B at a speed of over 22 feet per second.
Hence it may be said that no explosion can occur in a pipe provided

Q/(19.7d^2) = 22 or more;

i.e., Q/d^2=433.4

In plain language, if the number of cubic feet passing through the pipe per
hour divided by the square of the diameter of the pipe is at least 433.4, no
explosion can take place within that pipe, even if the gas is highly explosive
and a light is applied to its exit.

In Chapter VI. are given the explosive limits of acetylene-air mixtures as
influenced by the diameter of the tube containing them. If we possessed a
similar table showing the speed of the explosive wave in mixtures of known
composition, the foregoing formulæ would enable us to calculate the
minimum speed which would insure absence of explosibility in a supply-
pipe of any given diameter throughout its length, or at its narrowest part. It
would not, however, be possible simply by increasing the forward speed of
an explosive mixture of acetylene and air to a point exceeding that of its
explosion velocity to prevent all danger of firing back in an atmospheric
burner tube. A much higher pressure than is usually employed in gas-

Page 272

burners, other than blowpipes, would be needed to confer a sufficient
degree of velocity upon the gas, a pressure which would probably fracture
any incandescent mantle placed in the flame.

SERVICE-PIPES AND MAINS.--The pipes used for the distribution of
acetylene must be sound in themselves, and their joints perfectly tight.
Higher pressures generally prevail in acetylene service-pipes within a house
than in coal-gas service-pipes, while slight leaks are more offensive and
entail a greater waste of resources. Therefore it is uneconomical, as well as
otherwise objectionable, to employ service-pipes or fittings for acetylene
which are in the least degree unsound. Unfortunately ordinary gas-barrel is
none too sound, nor well-threaded, and the taps and joints of ordinary gas-
fittings are commonly leaky. Hence something better should invariably be
used for acetylene. What is known as "water" barrel, which is one gauge
heavier than gas-barrel of the same size, may be adopted for the service-
pipes, but it is better to incur a slight extra initial expense and to use
"steam" barrel, which is of still heavier gauge and is sounder than either gas
or water-pipe. All elbows, tees, &c., should be of the same quality. The
fitters' work in making the joints should be done with the utmost care, and
the sloppy work often passed in the case of coal-gas services must on no
account be allowed. It is no exaggeration to say that the success of an
acetylene installation, from the consumer's point of view, will largely, if not
principally, depend on the tightness of the pipes in his house. The statement
has been made that the "paint" used by gas-fitters, i.e., the mixture of red
and white lead ground in "linseed" oil, is not suitable for employment with
acetylene, and it has been proposed to adopt a similar material in which the
vehicle is castor-oil. No good reason has been given for the preference for
castor-oil, and the troubles which have arisen after using ordinary paint may
be explained partly on the very probable assumption that the oil was not
genuine linseed, and so did not dry, and partly on the fact that almost entire
reliance was placed on the paint for keeping the joint sound. Joints for
acetylene, like those for steam and high-pressure water, must be made tight
by using well-threaded fittings, so as to secure metallic contact between
pipe and socket, &c.; the paint or spun-yarn is only an additional safeguard.
In making a faced joint, washers of (say, 7 lb) lead, or coils of lead-wire arc
extremely convenient and quite trustworthy; the packing can be used
repeatedly.

Page 273

LEAKAGE.--Broadly speaking, it may be said that the commercial success
of any village acetylene-supply--if not that of all large installations--
depends upon the leakage being kept within moderate limits. It follows
from what was stated in Chapter VI. about the diffusion of acetylene, that
from pipes of equal porosity acetylene and coal-gas will escape at equal
rates when the effective pressure in the pipe containing acetylene is double
that in the pipe containing coal-gas. The loss of coal-gas by leakage is
seldom less than 5 per cent. of the volume passed into the main at the
works; and provided a village main delivering acetylene is not unduly long
in proportion to the consumption of gas--or, in other words, provided the
district through which an acetylene distributing main passes is not too
sparsely populated--the loss of acetylene should not exceed the same figure.
Caro holds that the loss of gas by leakage from a village installation should
be quoted in absolute figures and not as a percentage of the total make as
indicated by the works meter, because that total make varies so largely at
different periods of the year, while the factors which determine the
magnitude of the leakage are always identical; and therefore whereas the
actual loss of gas remains the same, it is represented to be more serious in
the summer than in the winter. Such argument is perfectly sound, but the
method of returning leakage as a percentage of the make has been
employed in the coal-gas industry for many years, and as it does not appear
to have led to any misunderstanding or inconvenience, there is no particular
reason for departing from the usual practice in the case of acetylene where
the conditions as to uniform leakage and irregular make are strictly
analogous.

Caro has stated that a loss of 15 to 20 litres per kilometre per hour (i.e., of
0.85 to 1.14 cubic feet per mile per hour) from an acetylene distributing
main is good practice; but it should be noted that much lower figures have
been obtained when conditions are favourable and when due attention has
been devoted to the fitters' work. In one of the German village acetylene
installations where the matter has been carefully investigated (Döse, near
Cuxhaven), leakage originally occurred at the rate of 7.3 litres per kilometre
per hour in a main 8.5 kilometres, or 5.3 miles, long and 4 to 2 inches in
diameter; but it was reduced to 5.2 litres, and then to 3.12 litres by
tightening the plugs of the street lantern and other gas cocks. In British
units, these figures are 0.415, 0.295, and 0.177 cubic foot per mile per hour.

Page 274

By calculation, the volume of acetylene generated in this village would
appear to have been about 23,000 cubic feet per mile of main per year, and
therefore it may be said that the proportion of gas lost was reduced by
attending to the cocks from 15.7 per cent, to 11.3 per cent, and then to 6.8
per cent. At another village where the main was 2.5 kilometres long, tests
extending over two months, when the public lamps were not in use, showed
the leakage to be 4.4 litres per kilometre per hour, i.e., 1.25 cubic foot per
mile per hour, when the annual make was roughly 46,000 cubic feet per
mile of main. Here, the loss, calculated from the direct readings of the
works motor, was 4.65 per cent.

When all the fittings, burners excepted, have been connected, the whole
system of pipes must be tested by putting it under a gas (or air) pressure of
9 or 12 inches of water, and observing on an attached pressure gauge
whether any fall in pressure occurs within fifteen minutes after the main
inlet tap has been shut. The pressure required for this purpose can be
obtained by temporarily weighting the holder, or by the employment of a
pump. If the gauge shows a fall of pressure of one quarter of an inch or
more in these circumstances, the pipes must be examined until the leak is
located. In the presence of a meter, the installation can conveniently be
tested for soundness by throwing into it, through the meter, a pressure of 12
inches or so of water from the weighted holder, then leaving the inlet cock
open, and observing whether the index hand on the lowest dial remains
perfectly stationary for a quarter of an hour--movement of the linger again
indicating a leak. The search for leaks must never be made with a light; if
the pipes are full of air this is useless, if full of gas, criminal in its stupidity.
While the whole installation is still under a pressure of 12 inches thrown
from the loaded holder, whether it contains air or gas, first all the likely
spots (joints, &c.), then the entire length of pipe is carefully brushed over
with strong soapy water, which will produce a conspicuous "soap- bubble"
wherever the smallest flaw occurs. The tightness of a system of pipes put
under pressure from a loaded holder cannot be ascertained safely by
observing the height of the bell, and noting if it falls on standing. Even if
there is no issue of gas from the holder, the position of the bell will alter
with every variation in temperature of the stored gas or surrounding air, and
with every movement of the barometer, rising as the temperature rises and
as the barometer falls, and vice versâ, while, unless the water in the seal is

Page 275

saturated with whatever gas the holder contains, the bell will steadily drop a
little an part of its contents are lost by dissolution in the liquid.

PIPES AND FITTINGS.--As a general rule it is unadvisable to use lead or
composition pipe for permanent acetylene connexions. If exposed, it is
liable to be damaged, and perhaps penetrated by a blow, and if set in the
wall and covered with paper or panel it is liable to be pierced if nails or
tacks should at any time be driven into the wall. There is also an increased
risk in case of fire, owing to its ready fusibility. If used at all--and it has
obvious advantages--lead or composition piping should be laid on the
surface of the walls, &c., and protected from blows, &c., by a light wooden
casing, outwardly resembling the wooden coverings for electric lighting
wires. It has been a common practice, in laying the underground mains
required for supplying the villages which are lighted by means of acetylene
from a central works in different parts of France, to employ lead pipes. The
plan is economical, but in view of the danger that the main might be
flattened by the weight of heavy traction-engines passing over the roads, or
that it might settle into local dips from the same cause or from the action of
subterranean water, in which dips water would be constantly condensing in
cold weather, the use of lead for this purpose cannot be recommended.
Steam-barrel would be preferable to cast pipe, because permanently sound
joints are easier to make in the former, and because it is not so brittle.

Page 276

The fittings used for acetylene must have perfectly sound joints and taps,
for the same reasons that the service-pipes must be quite sound. Common
gas-fittings will not do, the joints, taps, ball-sockets, &c., are not accurately
enough ground to prevent leakage. They may in many cases be improved by
regrinding, but often the plug and barrel are so shallow that it is almost
impossible to ensure soundness. It is therefore better to procure fittings
having good taps and joints in the first instance; the barrels should be long,
fairly wide, and there should be no sensible "play" between plug and barrel
when adjusted so that the plug turns easily when lightly lubricated. Fittings
are now being specially made for acetylene, which is a step in the right
direction, because, in addition to superior taps and joints being essential,
smaller bore piping and smaller through-ways to the taps than are required
for coal-gas serve for acetylene. It is perhaps advisable to add that wherever
a rigid bracket or fitting will answer as well as a jointed one, the latter
should on no account be used; also water-slide pendants should never be
employed, as they are fruitful of accidents, and their apparent advantages
are for the most part illusory. Ball-sockets also should be avoided if
possible; if it is absolutely necessary to have a fitting with a ball-socket, the
latter should have a sleeve made of a short length of sound rubber-tubing of
a size to give a close fit, slipped over so as to join the ball portion to the
socket portion. This sleeve should be inspected once a quarter at least, and
renewed immediately it shows signs of cracking. Generally speaking all the
fittings used should be characterised by structural simplicity; any
ornamental or decorative effects desired may be secured by proper design
without sacrifice of the simplicity which should always mark the essential
and operative parts of the fitting. Flexible connexions between the fixed
service-pipe and a semi-portable or temporary burner may at times be
required. If the connexion is for permanent use, it must not be of rubber, but
of the metallic flexible tubing which is now commonly employed for such
connexions in the case of coal-gas. There should be a tap between the
service-pipe and the flexible connexion, and this tap should be turned off
whenever the burner is out of use, so that the connexion is not at other times
under the pressure which is maintained in the service-pipes. Unless the
connexion is very short--say 2 feet or less--there should also be a tap at the
burner. These flexible connexions, though serviceable in the case of table-
lamps, &c., of which the position may have to be altered, are undesirable,

Page 277

as they increase the risk attendant on gas (whether acetylene or other
illuminating gas) lighting, and should, if possible, be avoided. Flexible
connexions may also be required for temporary use, such as for conveying
acetylene to an optical lantern, and if only occasionally called for, the cost
of the metallic flexible tubing will usually preclude its use. It will generally
be found, however, that the whole connexion in such a case can be of
composition or lead gas-piping, connected up at its two ends by a few
inches of flexible rubber tubing. It should be carried along the walls or over
the heads of people who may use the room, rather than across the floor, or
at a low level, and the acetylene should be turned on to it only when
actually required for use, and turned off at the fixed service-pipe as soon as
no longer required. Quite narrow composition tubing, say 1/4-inch, will
carry all the acetylene required for two or three burners. The cost of a
composition temporary connexion will usually be less than one of even
common rubber tubing, and it will be safer. The composition tubing must
not, of course, be sharply bent, but carried by easy curves to the desired
point, and it should be carefully rolled in a roll of not less than 18 inches
diameter when removed. If these precautions are observed it may be used
very many times.

Acetylene service-pipes should, wherever possible, be laid with a fall,
which may be very slight, towards a small closed vessel adjoining the
gasholder or purifier, in order that any water deposited from the gas owing
to condensation of aqueous vapour may run out of the pipe into that
apparatus. Where it is impossible to secure an uninterrupted fall in that
direction, there should be inserted in the service-pipe, at the lowest point of
each dip it makes, a short length of pipe turned downwards and terminating
in a plug or sound tap. Water condensing in this section of the service-pipe
will then run down and collect in this drainage-pipe, from which it can be
withdrawn at intervals by opening the plug or tap for a moment. The
condensed water is thus removed from the service-pipe, and does not
obstruct its through-way. Similar drainage devices may be used at the
lowest points of all dips in mains, though there are special seal-pots which
take the place of the cock or plug used to seal the end of the drainage-pipe.
Such seal-pots or "syphons" are commonly used on ordinary gas-
distributing systems, and might be applied in the case of large acetylene

Page 278

installations, as they offer facilities for removing the condensed water from
time to time in a convenient and expeditious manner.

EXPULSION OF AIR FROM MAINS.--After a service-pipe system has
been proved to be sound, it is necessary to expel the air from it before
acetylene can be admitted to it with a view to consumption. Unless the
system is a very large one, the expulsion of air is most conveniently
effected by forcing from the gasholder preliminary batches of acetylene
through the pipes, while lights are kept away from the vicinity. This
precaution is necessary because, while the acetylene is displacing the air in
the pipes, they will for some time contain a mixture of air and acetylene in
proportions which fall within the explosive limits of such a mixture. If the
escaping acetylene caught fire from any adjacent light under these
conditions, a most disastrous explosion would ensue and extend through all
the ramifications of the system of pipes. Therefore the first step when a new
system of pipes has to be cleared of air is to see that there are no lights in or
about the house--either fires, lamps, cigars or pipes, candles or other flames.
Obviously this work must be done in the daytime and finished before
nightfall. Burners are removed from two or more brackets at the farthest
points in the system from the gasholder, and flexible connexions are
temporarily attached to them, and led through a window or door into the
open air well clear of the house. One of the brackets selected should as a
rule be the lowest point supplied in the house. The gasholder having been
previously filled with acetylene, the tap or taps on the pipe leading to the
house are turned on, and the acetylene is passed under slight pressure into
the system of pipes, and escapes through the aforesaid brackets, of which
the taps have been turned on, into the open. The taps of all other brackets
are kept closed. The gas should be allowed to flow thus through the pipes
until about five times the maximum quantity which all the burners on the
system would consume in an hour has escaped from the open brackets. The
taps on these brackets are then closed, and the burners replaced. Flexible
tubing is then connected in place of the burners to all the other brackets in
the house, and acetylene is similarly allowed to escape into the open air
from each for a quarter of an hour. All taps are then closed, and the burners
replaced; all windows in the house are left open wide for half an hour to
allow of the dissipation of any acetylene which may have accumulated in
any part of it, and then, while full pressure from the gasholder is

Page 279

maintained, a tap is turned on and the gas lighted. If it burns with a good,
fully luminous flame it may be concluded that the system of pipes is
virtually free from air, and the installation may be used forthwith as
required. If, however, the flame is very feebly luminous, or if the escaping
gas does not light, lights must be extinguished, and the pipes again blown
through with acetylene into the open air. The burner must invariably be in
position when a light is applied, because, in the event of the pipes still
containing an explosive mixture, ignition would not be communicated
through the small orifices of the burner to the mixture in the pipes, and the
application of the light would not entail any danger of an explosion.

Gasfitters familiar with coal-gas should remember, when putting a system
of acetylene pipes into use for the first time, that the range over which
mixtures of acetylene and air are explosive is wider than that over which
mixtures of coal-gas and air are explosive, and that greater care is therefore
necessary in getting the pipes and rooms free from a dangerous mixture.

The mains for very large installations of acetylene--e.g., for lighting a small
town--may advisedly be freed from air by some other plan than simple
expulsion of the air by acetylene, both from the point of view of economy
and of safety. If the chimney gases from a neighbouring furnace are found
on examination to contain not more than about 8 per cent of oxygen, they
may be drawn into the gasholder and forced through the pipes before
acetylene is admitted to them. The high proportion of carbon dioxide and
the low proportion of oxygen in chimney gases makes a mixture of
acetylene and chimney gases non-explosive in any proportions, and hence if
the air is first wholly or to a large extent expelled from a pipe, main, or
apparatus, by means of chimney gases, acetylene may be admitted, and a
much shorter time allowed for the expulsion by it of the contents of the
pipe, before a light is applied at the burners, &c. This plan, however, will
usually only be adopted in the case of very large pipes, &c.; but on a
smaller scale the air may be swept out of a distributing system by bringing
it into connexion with a cylinder of compressed or liquefied carbon dioxide,
the pressure in which will drive the gas to any spot where an outlet is
provided. As these cylinders of "carbonic acid" are in common employment
for preparing aerated waters and for "lifting" beer, &c., they are easy to hire
and use.

Page 280

TABLE (B).

Giving the Sizes of Pipe which should be used in practice for Acetylene
when the fall of pressure in the Pipe is not to exceed 0.1 inch. (Based on
Morel's formula.)

_________________________________________________________
| | |
| Cubic Feet of | Diameters of Pipe to be used up to |
| Acetylene | the lengths indicated. |
| which the Pipe |_______________________________________|
| is required to | | | | | |
| pass in | 1/4 | 3/8 | 1/2 | 3/4 | 1 |
| One Hour. | inch. | inch. | inch. | inch. | inch. |
|________________|_______|_______|_______|_______|_______|
| | | | | | |
| | Feet. | Feet. | Feet. | Feet. | Feet. |
| 1 | 520 | 3960 | 16700 | ... | ... |
| 2 | 130 | 990 | 4170 | ... | ... |
| 3 | 58 | 440 | 1850 | ... | ... |
| 4 | 32 | 240 | 1040 | ... | ... |
| 5 | 21 | 150 | 660 | 5070 | ... |
| 6 | 14 | 110 | 460 | 3520 | ... |
| 7 | 10 | 80 | 340 | 2590 | ... |
| 8 | ... | 62 | 260 | 1980 | ... |
| 9 | ... | 49 | 200 | 1560 | ... |
| 10 | ... | 39 | 160 | 1270 | 5340 |
| 15 | ... | 17 | 74 | 560 | 2370 |
| 20 | ... | 10 | 41 | 310 | 1330 |
| 25 | ... | ... | 26 | 200 | 850 |
| 30 | ... | ... | 18 | 140 | 590 |
| 35 | ... | ... | 13 | 100 | 430 |
| 40 | ... | ... | 10 | 79 | 330 |
| 45 | ... | ... | ... | 62 | 260 |
| 50 | ... | ... | ... | 50 | 210 |
|________________|_______|_______|_______|_______|_______|

TABLE (A).

Showing the Quantities [Q] (in cubic feet) of Acetylene which will pass in
One Hour through Pipes of various diameters (in inches) under different
Falls of Pressure. (Based on Morel's formula.)

Page 281

_______________________________________________________________
_____
| | | | | | | | | | |
| |
| Diameter | | | | | | | | | |
| |
| of Pipe | 1/4| 3/8| 1/2| 3/4 | 1 | 1 | 1 | 1 | 2 | 2
| 3 |
| [_d_] = | | | | | | 1/4 | 1/2| 3/4| |
1/2| |
| inches | | | | | | | | | |
| |
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|
| |
|
| Length |
|
| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.10 inch.
|
| Feet |
|
|__________|___________________________________________________
______|
| | | | | | | | | | |
| |
| 10 | 7.2|19.9|40.8|112 |230 |405 | 635|
935|1305|2285|3600|
| 25 | 4.5|12.6|25.8| 71.2|146 |255 | 400| 590|
825|1445|2280|
| 50 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420|
585|1020|1610|
| 100 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410|
720|1140|
| 200 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290|
510| 805|
| 300 | 1.3| 3.6| 7.4| 20.5| 42.2| 73.7| 116| 171| 240|
415| 655|
| 400 | 1.1| 3.1| 6.4| 17.8| 36.5| 63.8| 100| 148| 205|
360| 570|
| 500 | 1.0| 2.8| 5.8| 15.9| 32.7| 57.1| 90| 132| 185|
320| 510|
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|

Page 282

| |
|
| Length |
|
| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.25 inch.
|
| Feet |
|
|__________|___________________________________________________
______|
| | | | | | | | | | |
| |
| 25 | 7.2|19.9|40.8|112 |230 |405 | 635|
935|1305|2285|3600|
| 50 | 5.1|14.1|28.9| 79.6|163 |285 | 450| 660|
925|1615|2550|
| 100 | 3.6| 9.9|20.4| 56.3|115 |200 | 320| 470|
655|1140|1800|
| 250 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410|
720|1140|
| 500 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290|
510| 805|
| 1000 | 1.1| 3.1| 6.4| 17.8| 36.5| 63.8| 100| 148| 205|
360| 570|
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|
| |
|
| Length |
|
| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.50 inch.
|
| Feet |
|
|__________|___________________________________________________
______|
| | | | | | | | | | |
| |
| 25 |10.2|28.1|57.8|159 |325 |570 |
900|1325|1850|3230|5095|
| 50 | 7.2|19.9|40.8|112 |230 |405 | 635|
935|1305|2285|3600|
| 100 | 5.1|14.1|28.9| 79.6|163 |285 | 450| 660|
925|1615|2550|

Page 283

| 250 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420|
585|1020|1610|
| 500 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410|
720|1140|
| 1000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290|
510| 805|
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|
| |
|
| Length |
|
| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.75 inch.
|
| Feet |
|
|__________|___________________________________________________
______|
| | | | | | | | | | |
| |
| 50 | 8.8|24.4|50.0|138 |280 |495 |
780|1145|1160|2800|4410|
| 100 | 6.2|17.2|35.4| 97.5|200 |350 | 550|
810|1130|1980|3120|
| 250 | 3.9|10.9|22.4| 61.7|126 |220 | 350| 510|
715|1250|1975|
| 500 | 2.8| 7.7|15.8| 43.6| 89.5|156 | 245| 360| 505|
885|1395|
| 1000 | 2.0| 5.4|11.2| 30.8| 63.3|110 | 174| 255| 360|
625| 985|
| 2000 | 1.4| 3.8| 7.9| 21.8| 44.8| 78.2| 123| 181| 250|
440| 695|
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|
| |
|
| Length |
|
| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 1.0 inch.
|
| Feet |
|
|__________|___________________________________________________
______|

Page 284

| | | | | | | | | | |
| |
| 100 | 7.2|19.9|40.8|112 |230 |405 | 635|
935|1305|2285|3600|
| 250 | 4.5|12.6|25.8| 71.2|146 |255 | 400| 590|
825|1445|2280|
| 500 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420|
585|1020|1610|
| 1000 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410|
720|1140|
| 2000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290|
510| 805|
| 3000 | 1.3| 3.6| 7.4| 20.5| 42.2| 73.7| 116| 171| 240|
415| 655|
|__________|___________________________________________________
______|
| |
|
| Length |
|
| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 1.5 inch.
|
| Feet |
|
|__________|___________________________________________________
______|
| | | | | | | | | | |
| |
| 250 | 5.6|15.4|31.6| 87.2|179 |310 | 495|
725|1010|1770|2790|
| 500 | 3.9|10.9|22.4| 61.7|126 |220 | 350| 510|
715|1250|1975|
| 1000 | 2.8| 7.7|15.8| 43.6| 89.5|156 | 245| 360| 505|
885|1395|
| 2000 | 2.0| 5.4|11.2| 30.8| 63.3|110 | 174| 255| 360|
625| 985|
| 3000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290|
510| 805|
| 4000 | 1.4| 3.8| 7.9| 21.8| 44.8| 78.2| 123| 181| 250|
440| 695|
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|
| |
|
| Length |
|

Page 285

| of Pipe |
|
| [_l_] = | Fall of Pressure in the Pipe [_h_] = 2.0 inches.
|
| Feet |
|
|__________|___________________________________________________
______|
| | | | | | | | | | |
| |
| 500 | 4.5|12.6|25.8| 71.2|146 |255 | 400| 590|
825|1445|2280|
| 1000 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420|
585|1020|1610|
| 2000 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410|
720|1140|
| 3000 | 1.8| 5.1|10.5| 29.1| 59.7|104 | 164| 240| 335|
590| 930|
| 4000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290|
510| 805|
| 5000 | 1.4| 4.0| 8.1| 22.5| 46.2| 80.8| 127| 187| 260|
455| 720|
| 6000 | 1.3| 3.6| 7.4| 20.5| 42.2| 73.7| 116| 171| 240|
415| 655|
|__________|____|____|____|_____|_____|_____|____|____|____|___
_|____|

NOTE.--In order not to impart to the above table the appearance of the
quantities having been calculated to a degree of accuracy which has no
practical significance, quantities of less than 5 cubic feet have been ignored
when the total quantity exceeds 200 cubic feet, and fractions of a cubic foot
have been included only when the total quantity is less than 100 cubic feet.

TABLE (C).

Giving the Sizes of Pipe which should be used in practice for Acetylene
when the fall of pressure in the Pipe is not to exceed 0.25 inch. (Based on
Morel's formula.)

_______________________________________________________________
_____
| |
|

Page 286

| Cubic feet |
|
| of |
|
| Acetylene | Diameters of Pipe to be used up to the lengths
stated.|
| which the |
|
| Pipe is |
|
| required
|_______________________________________________________|
| to pass | | | | | | | |
|
| in One | 1/4 | 1/2 | 3/4 | 1 | 1-1/4| 1-1/2| 1-3/4|
2 |
| Hour | inch.| inch.| inch.| inch.| inch.| inch.| inch.|
inch.|
|____________|______|______|______|______|______|______|______|
______|
| | | | | | | | |
|
| | Feet.| Feet.| Feet.| Feet.| Feet.| Feet.| Feet.|
Feet.|
| 2-1/2 | 1580 | 6680 | 50750| ... | ... | ... | ... |
... |
| 5 | 390 | 1670 | 12690| 53160| ... | ... | ... |
... |
| 7-1/2 | 175 | 710 | 5610| 23760| ... | ... | ... |
... |
| 10 | 99 | 410 | 3170| 13360| 40790| ... | ... |
... |
| 15 | 41 | 185 | 1410| 5940| 18130| 45110| ... |
... |
| 20 | 24 | 105 | 790| 3350| 10190| 25370| 54840|
... |
| 25 | 26 | 67 | 500| 2130| 6520| 16240| 35100|
... |
| 30 | 11 | 46 | 350| 1480| 4530| 11270| 24370|
47520|
| 35 | ... | 34 | 260| 1090| 3330| 8280| 17900|
34910|
| 40 | ... | 26 | 195| 830| 2550| 6340| 13710|
26730|
| 45 | ... | 20 | 155| 660| 2010| 5010| 10830|
21120|
| 50 | ... | 16 | 125| 530| 1630| 4060| 8770|
17110|

Page 287

| 60 | ... | 11 | 88| 370| 1130| 2880| 6090|
11880|
| 70 | ... | ... | 61| 270| 830| 2070| 4470|
8730|
| 80 | ... | ... | 49| 210| 630| 1580| 3420|
6680|
| 90 | ... | ... | 39| 165| 500| 1250| 2700|
5280|
| 100 | ... | ... | 31| 130| 400| 1010| 2190|
4270|
| 150 | ... | ... | 14| 59| 180| 450| 970|
1900|
| 200 | ... | ... | ... | 33| 100| 250| 540|
1070|
| 250 | ... | ... | ... | 21| 65| 160| 350|
680|
| 500 | ... | ... | ... | ... | 16| 40| 87|
170|
| 1000 | ... | ... | ... | ... | ... | 10| 22|
42|
|____________|______|______|______|______|______|______|______|
______|

TABLE (D).

Giving the Sizes of Pipe which should be used in practice for Acetylene
Mains when the fall of pressure in the Main is not to exceed 0.5 inch,
(Based on Morel's formula.)

_______________________________________________________________
_____
| |
|
| Cubic feet |
|
| of |
|
| Acetylene | Diameters of Pipe to be used up to the lengths
stated.|
| which the |
|
| Main is |
|
| required

Page 288

|_______________________________________________________|
| to pass | | | | | | | |
|
| in One | 3/4 | 1 | 1-1/4| 1-1/2| 1-3/4| 2 | 2-1/2|
3 |
| Hour | inch.| inch.| inch.| inch.| inch.| inch.| inch.|
inch.|
|____________|______|______|______|______|______|______|______|
______|
| | | | | | | | |
|
|
|Miles.|Miles.|Miles.|Miles.|Miles.|Miles.|Miles.|Miles.|
| 10 | 5.05 | ... | ... | ... | ... | ... | ... |
... |
| 25 | 0.80 | 2.45 | 6.15 | ... | ... | ... | ... |
... |
| 50 | 0.20 | 0.60 | 1.50 | 3.30 | 6.45 | ... | ... |
... |
| 100 | 0.05 | 0.15 | 0.35 | 0.80 | 1.60 | 4.95 |12.30 |
... |
| 200 | ... | 0.04 | 0.09 | 0.20 | 0.40 | 1.20 | 3.05
|12.95 |
| 300 | ... | ... | 0.04 | 0.09 | 0.18 | 0.55 | 1.35 |
5.75 |
| 400 | ... | ... | ... | 0.05 | 0.10 | 0.30 | 0.75 |
3.25 |
| 500 | ... | .. | ... | 0.03 | 0.06 | 0.20 | 0.50 |
2.05 |
| 750 | ... | ... | ... | ... | 0.03 | 0.08 | 0.20 |
0.80 |
| 1100 | ... | ... | ... | ... | ... | 0.05 | 0.12 |
0.50 |
| 1500 | ... | ... | ... | ... | ... | 0.02 | 0.05 |
0.23 |
| 2000 | ... | ... | ... | ... | ... | ... | 0.03 |
0.13 |
| 2500 | ... | ... | ... | ... | ... | ... | 0.02 |
0.08 |
| 5000 | ... | ... | ... | ... | ... | ... | ... |
0.03 |
|____________|______|______|______|______|______|______|______|
______|

TABLE (E).

Page 289

Giving the Sizes of Pipe which should be used in practice for Acetylene
Mains when the fall of pressure in the Main is not to exceed 1.0 inch.
(Based on Morel's formula.)

_______________________________________________________________
___
| |
|
| Cubic feet |
|
| of |
|
| Acetylene |Diameters of Pipe to be used up to the lengths
stated|
| which the |
|
| Main is |
|
| required
|_____________________________________________________|
| to pass | | | | | | | | |
|
| in One | 3/4 | 1 |1-1/4|1-1/2|1-3/4| 2 |2-1/2| 3 |
4 |
| Hour
|inch.|inch.|inch.|inch.|inch.|inch.|inch.|inch.|inch.|
|____________|_____|_____|_____|_____|_____|_____|_____|_____|_
____|
| | | | | | | | | |
|
|
|Miles|Miles|Miles|Mile.|Miles|Miles|Miles|Miles|Miles|
| 10 | 2.40|10.13|30.90| ... | ... | ... | ... | ... |
... |
| 25 | 0.38| 1.62| 4.94|12.30| ... | ... | ... | ... |
... |
| 50 | 0.09| 0.40| 1.23| 3.07| 6.65|12.96| ... | ... |
... |
| 100 | 0.02| 0.10| 0.30| 0.77| 1.66| 3.24| 9.88| ... |
... |
| 200 | ... | 0.02| 0.07| 0.19| 0.41| 0.81| 2.47| 6.15|
... |
| 300 | ... | 0.01| 0.03| 0.08| 0.18| 0.36| 1.09|
2.73|11.52|
| 400 | ... | ... | 0.0 | 0.05| 0.10| 0.20| 0.61| 1.53|

Page 290

6.48|
| 500 | ... | ... | 0.0 | 0.03| 0.06| 0.13| 0.39| 0.98|
4.14|
| 750 | ... | ... | ... | 0.01| 0.03| 0.05| 0.17| 0.43|
1.84|
| 1000 | ... | ... | ... | ... | 0.01| 0.03| 0.10| 0.24|
1.03|
| 1500 | ... | ... | ... | ... | ... | 0.01| 0.01| 0.11|
0.46|
| 2000 | ... | ... | ... | ... | ... | ... | 0.02| 0.06|
0.26|
| 2500 | ... | ... | ... | ... | ... | ... | 0.01| 0.04|
0.16|
| 5000 | ... | ... | ... | ... | ... | ... | ... | 0.01|
0.04|
|____________|_____|_____|_____|_____|_____|_____|_____|_____|_
____|

Page 291

CHAPTER VIII
COMBUSTION OF ACETYLENE IN LUMINOUS
BURNERS--THEIR DISPOSITION

NATURE OF LUMINOUS FLAMES.--When referring to methods of
obtaining artificial light by means of processes involving combustion or
oxidation, the term "incandescence" is usually limited to those forms of
burner in which some extraneous substance, such as a "mantle," is raised to
a brilliant white heat. Though convenient, the phrase is a mere convention,
for all artificial illuminants, even including the electric light, which exhibit
a useful degree of intensity depend on the same principle of incandescence.
Adopting the convention, however, an incandescent burner is one in which
the fuel burns with a non-luminous or atmospheric flame, the light being
produced by causing that flame to play upon some extraneous refractory
body having the property of emitting much light when it is raised to a
sufficiently high temperature; while a luminous burner is one in which the
fuel is allowed to combine with atmospheric oxygen in such a way that one
or more of the constituents in the gas evolves light as it suffers combustion.
From the strictly chemical point of view the light-giving substance in the
incandescent flame lasts indefinitely, for it experiences no change except in
temperature; whereas the light-giving substance in a luminous flame lasts
but for an instant, for it only evolves light during the act of its combination
with the oxygen of the atmosphere. Any fluid combustible which burns with
a flame can be made to give light on the incandescent system, for all such
materials either burn naturally, or can be made to burn with a non- luminous
flame, which can be employed to raise the temperature of some mantle; but
only those fuels can be burnt on the self-luminous system which contain
some ingredient that is liberated in the elemental state in the flame, the said
ingredient being one which combines energetically with oxygen so as to
liberate much local heat. In practice, just as there are only two or three
substances which are suitable for the construction of an incandescent
mantle, so there is only one which renders a flame usefully self-luminous,
viz., carbon; and therefore only such fuels as contain carbon among their

Page 292

constituents can be burnt so as to produce light without the assistance of the
mantle. But inasmuch as it is necessary for the evolution of light by the
combustion of carbon that that carbon shall be in the free state, only those
carbonaceous fuels yield light without the mantle in which the
carbonaceous ingredient is dissociated into its elements before it is
consumed. For instance, alcohol and carbon monoxide are both
combustible, and both contain carbon; but they yield non-luminous flames,
for the carbon burns to carbon dioxide in ordinary conditions without
assuming the solid form; ether, petroleum, acetylene, and some of the
hydrocarbons of coal-gas do emit light on combustion, for part of their
carbon is so liberated. The quantity of light emitted by the glowing
substance increases as the temperature of that substance rises: the gain in
light being equal to the fifth or higher power of the gain in heat; [Footnote:
Calculated from absolute zero.] therefore unnecessary dissipation of heat
from a flame is one of the most important matters to be guarded against if
that flame is to be an economical illuminant. But the amount of heat
liberated when a certain weight (or volume) of a particular fuel combines
with a sufficient quantity of oxygen to oxidise it wholly is absolutely fixed,
and is exactly the same whether that fuel is made to give a luminous or a
non-luminous flame. Nevertheless the atmospheric flame given by a certain
fuel may be appreciably hotter than its luminous flame, because the former
is usually smaller than the latter. Unless the luminous flame of a rich fuel is
made to expose a wide surface to the air, part of its carbon may escape
ultimate combustion; soot or smoke may be produced, and some of the most
valuable heat-giving substance will be wasted. But if the flame is made to
expose a large surface to the air, it becomes flat or hollow in shape instead
of being cylindrical and solid, and therefore in proportion to its cubical
capacity it presents to the cold air a larger superficies, from which loss of
heat by radiation, &c., occurs. Being larger, too, the heat produced is less
concentrated.

It does not fall within the province of the present book to discuss the
relative merits of luminous and incandescent lighting; but it may be
remarked that acetylene ranks with petroleum against coal-gas, carburetted
or non-carburetted water-gas, and semi-water-gas, in showing a
comparatively small degree of increased efficiency when burnt under the
mantle. Any gas which is essentially composed of carbon monoxide or

Page 293

hydrogen alone (or both together) burns with a non-luminous flame, and
can therefore only be used for illuminating purposes on the incandescent
system; but, broadly speaking, the higher is the latent illuminating power of
the gas itself when burnt in a non-atmospheric burner, the less marked is the
superiority, both from the economical and the hygienic aspect, of its
incandescent flame. It must be remembered also that only a gas yields a
flame when it is burnt; the flame of a paraffin lamp and of a candle is due to
the combustion of the vaporised fuel. Methods of burning acetylene under
the mantle are discussed in Chapter IX.; here only self-luminous flames are
being considered, but the theoretical question of heat economy applies to
both processes.

Heat may be lost from a flame in three several ways: by direct radiation and
conduction into the surrounding air, among the products of combustion, and
by conduction into the body of the burner. Loss of heat by radiation and
conduction to the air will be the greater as the flame exposes a larger
surface, and as a more rapid current of cold air is brought into proximity
with the flame. Loss of heat by conduction, into the burner will be the
greater as the material of which the burner is constructed is a better
conductor of heat, and as the mass of material in that burner is larger. Loss
of heat by passage into the combustion products will also be greater as these
products are more voluminous; but the volume of true combustion products
from any particular gas is a fixed quantity, and since these products must
leave the flame at the temperature of that flame--where the highest
temperature possible is requisite--it would seem that no control can be had
over the quantity of heat so lost. However, although it is not possible in
practice to supply a flame with too little air, lest some of its carbon should
escape consumption and prove a nuisance, it is very easy without
conspicuous inconvenience to supply it with too much; and if the flame is
supplied with too much, there is an unnecessary volume of air passing
through it to dilute the true combustion products, which air absorbs its own
proper proportion of heat. It is only the oxygen of the air which a flame
needs, and this oxygen is mixed with approximately four times its volume
of nitrogen; if, then, only a small excess of oxygen (too little to be
noticeable of itself) is admitted to a flame, it is yet harmful, because it
brings with it four times its volume of nitrogen, which has to be raised to
the same temperature as the oxygen. Moreover, the nitrogen and the excess

Page 294

of oxygen occupy much space in the flame, making it larger, and
distributing that fixed quantity of heat which it is capable of generating over
an unnecessarily large area. It is for this reason that any gas gives so much
brighter a light when burnt in pure oxygen than in air, (1) because the flame
is smaller and its heat more concentrated, and (2) because part of its heat is
not being wasted in raising the temperature of a large mass of inert nitrogen.
Thus, if the flame of a gas which naturally gives a luminous flame is
supplied with an excess of air, its illuminating value diminishes; and this is
true whether that excess is introduced at the base of the actual flame, or is
added to the gas prior to ignition. In fact the method of adding some air to a
naturally luminous gas before it arrives at its place of combustion is the
principle of the Bunsen burner, used for incandescent lighting and for most
forms of warming and cooking stoves. A well-made modern atmospheric
burner, however, does not add an excess of air to the flame, as might appear
from what has been said; such a burner only adds part of the air before and
the remainder of the necessary quantity after the point of first ignition--the
function of the primary supply being merely to insure thorough admixture
and to avoid the production of elemental carbon within the flame.

ILLUMINATING POWER.--It is very necessary to observe that, as the
combined losses of heat from a flame must be smaller in proportion to the
total heat produced by the flame as the flame itself becomes larger, the
more powerful and intense any single unit of artificial light is, the more
economical does it become, because economy of heat spells economy of
light. Conversely, the more powerful and intense any single unit of light is,
the more is it liable to injure the eyesight, the deeper and, by contrast, the
more impenetrable are the shadows it yields, and the less pleasant and
artistic is its effect in an occupied room. For economical reasons, therefore,
one large central source of light is best in an apartment, but for
physiological and æsthetic reasons a considerable number of
correspondingly smaller units are preferable. Even in the street the
economical advantage of the single unit is outweighed by the inconvenience
of its shadows, and by the superiority of a number of evenly distributed
small sources to one central large source of light whenever the natural
transmission of light rays through the atmosphere is interfered with by mist
or fog. The illuminating power of acetylene is commonly stated to be "240
candles" (though on the same basis Wolff has found it to be about 280

Page 295

candles). This statement means that when acetylene is consumed in the
most advantageous self-luminous burner at the most advantageous rate, that
rate (expressed in cubic feet per hour) is to 5 in the same ratio as the
intensity of the light evolved (expressed in standard candles) is to the said
"illuminating power." Thus, Wolff found that when acetylene was burnt in
the "0000 Bray" fish- tail burner at the rate of 1.377 cubic feet per hour, a
light of 77 candle-power was obtained. Hence, putting x to represent the
illuminating power of the acetylene in standard candles, we have:

1.377 / 5 = 77 / x hence x = 280.

Therefore acetylene is said to have, according to Wolff, an illuminating
power of about 280 candles, or according to other observers, whose results
have been commonly quoted, of 240 candles. The same method of
calculating the nominal illuminating power of a gas is applied within the
United Kingdom in the case of all gases which cannot be advantageously
burnt at the rate of 5 cubic feet per hour in the standard burner (usually an
Argand). The rate of 5 cubic feet per hour is specified in most Acts of
Parliament relating to gas-supply as that at which coal-gas is to be burnt in
testings of its illuminating power; and the illuminating power of the gas is
defined as the intensity, expressed in standard candles, of the light afforded
when the gas is burnt at that rate. In order to make the values found for the
light evolved at more advantageous rates of consumption by other
descriptions of gas--such as oil-gas or acetylene--comparable with the
"illuminating power" of coal- gas as defined above, the values found are
corrected in the ratio of the actual rate of consumption to 5 cubic feet per
hour.

In this way the illuminating power of 240 candles has been commonly
assigned to acetylene, though it would be clearer to those unfamiliar with
the definition of illuminating power in the Acts of Parliament which
regulate the testing of coal-gas, if the same fact were conveyed by stating
that acetylene affords a maximum illuminating power of 48 candles (i.e.,
240 / 5) per cubic foot. Actually, by misunderstanding of the accepted
though arbitrary nomenclature of gas photometry, it has not infrequently
been assorted or implied that a cubic foot of acetylene yields a light of 240
candle-power instead of 48 candle-power. It should, moreover, be

Page 296

remembered that the ideal illuminating power of a gas is the highest
realisable in any Argand or flat-flame burner, while the said burner may not
be a practicable one for general use in house lighting. Thus, the burners
recommended for general use in lighting by acetylene do not develop a light
of 48 candles per cubic foot of gas consumed, but considerably less, as will
appear from the data given later in this chapter.

It has been stated that in order to avoid loss of heat from a flame through
the burner, that burner should present only a small mass of material (i.e., be
as light in weight as possible), and should be constructed of a bad heat-
conductor. But if a small mass of a material very deficient in heat-
conducting properties comes in contact with a flame, its temperature rises
seriously and may approach that of the base of the flame itself. In the case
of coal-gas this phenomenon is not objectionable, is even advantageous,
and it explains why a burner made of steatite, which conducts heat badly, in
always more economical (of heat and therefore of light) than an iron one. In
the case of acetylene the same rule should, and undoubtedly does, apply
also; but it is complicated, and its effect sometimes neutralised, by a
peculiarity of the gas itself. It has been shown in Chapters II. and VI. that
acetylene polymerises under the influence of heat, being converted into
other bodies of lower illuminating power, together with some elemental
carbon. If, now, acetylene is fed into a burner which, being composed of
some material like steatite possessed of low heat-conducting and radiating
powers, is very hot, and if the burner comprises a tube of sensible length,
the gas that actually arrives at the orifice may no longer be pure acetylene,
but acetylene diluted with inferior illuminating agents, and accompanied by
a certain proportion of carbon. Neglecting the effect of this carbon, which
will be considered in the following paragraph, it is manifest that the
acetylene issuing from a hot burner--assuming its temperature to exceed the
minimum capable of determining polymerisation-- may emit less light per
unit of volume than the acetylene escaping from a cold burner. Proof of this
statement is to be found in some experiments described by Bullier, who
observed that when a small "Manchester" or fish-tail burner was allowed to
become naturally hot, the quantity of gas needed to give the light of one
candle (uncorrected) was 1.32 litres, but when the burner was kept cool by
providing it with a jacket in which water was constantly circulating, only

Page 297

1.13 litres of acetylene were necessary to obtain the same illuminating
value, this being an economy of 16 per cent.

EARLY BURNERS.--One of the chief difficulties encountered in the early
days of the acetylene industry was the design of a satisfactory burner which
should possess a life of reasonable length. The first burners tried were
ordinary oil-gas jets, which resemble the fish-tails used with coal- gas, but
made smaller in every part to allow for the higher illuminating power of the
oil-gas or acetylene per unit of volume. Although the flames they gave were
very brilliant, and indeed have never been surpassed, the light quickly fell
off in intensity owing to the distortion of their orifices caused by the
deposition of solid matter at the edges. Various explanations have been
offered to account for the precipitation of solid matter at the jets. If the
acetylene passes directly to the burner from a generator having carbide in
excess without being washed or filtered in any way, the gas may carry with
it particles of lime dust, which will collect in the pipes mainly at the points
where they are constricted; and as the pipes will be of comparatively large
bore until the actual burner is readied, it will be chiefly at the orifices where
the deposition occurs. This cause, though trivial, is often overlooked. It will
be obviated whenever the plant is intelligently designed. As the phosphoric
anhydride, or pentoxide, which is produced when a gas containing
phosphorus burns, is a solid body, it may be deposited at the burner jets.
This cause may be removed, or at least minimised, by proper purification of
the acetylene, which means the removal of phosphorus compounds. Should
the gas contain hydrogen silicide siliciuretted hydrogen), solid silica will be
produced similarly, and will play its part in causing obstruction. According
to Lewes the main factor in the blocking of the burners is the presence of
liquid polymerised products in the acetylene, benzene in particular; for he
considers that these bodies will be absorbed by the porous steatite, and will
be decomposed under the influence of heat in that substance, saturating the
steatite with carbon which, by a "catalytic" action presumably, assists in the
deposition of further quantities of carbon in the burner tube until distortion
of the flame results. Some action of this character possibly occurs; but were
it the sole cause of blockage, the trouble would disappear entirely if the gas
were washed with some suitable heavy oil before entering the burners, or if
the latter were constructed of a non-porous material. It is certainly true that
the purer is the acetylene burnt, both as regards freedom from phosphorus

Page 298

and absence of products of polymerisation, the longer do the burners last;
and it has been claimed that a burner constructed at its jets of some non-
porous substance, e.g., "ruby," does not choke as quickly as do steatite ones.
Nevertheless, stoppages at the burners cannot be wholly avoided by these
refinements. Gaud has shown that when pure acetylene is burnt at the
normal rate in 1-foot Bray jets, growths of carbon soon appear, but do not
obstruct the orifices during 100 hours' use; if, however, the gas-supply is
checked till the flame becomes thick, the growths appear more quickly, and
become obstructive after some 60 hours' burning. On the assumption that
acetylene begins to polymerise at a temperature of 100° C., Gaud calculates
that polymerisation cannot cause blocking of the burners unless the speed of
the passing gas is so far reduced that the burner is only delivering one- sixth
of its proper volume. But during 1902 Javal demonstrated that on heating in
a gas-flame one arm of a twin, non-injector burner which had been and still
was behaving quite satisfactorily with highly purified acetylene, growths
were formed at the jet of that arm almost instantaneously. There is thus little
doubt that the principal cause of this phenomenon is the partial dissociation
of the acetylene (i.e., decomposition into its elements) as it passes through
the burner itself; and the extent of such dissociation will depend, not at all
upon the purity of the gas, but upon the temperature of the burner, upon the
readiness with which the heat of the burner is communicated to the gas, and
upon the speed at which the acetylene travels through the burner.

Some experiments reported by R. Granjon and P. Mauricheau-Beaupré in
1906 indicate, however, that phosphine in the gas is the primary cause of
the growths upon non-injector burners. According to these investigators the
combustion of the phosphine causes a deposit at the burner orifices of
phosphoric acid, which is raised by the flame to a temperature higher than
that of the burner. This hot deposit then decomposes some acetylene, and
the carbon deposited therefrom is rendered incombustible by the phosphoric
acid which continues to be produced from the combustion of the phosphine
in the gas. The incombustible deposit of carbon and phosphoric acid thus
produced ultimately chokes the burner.

It will appear in Chapter XI. that some of the first endeavours to avoid
burner troubles were based on the dilution of the acetylene with carbon
dioxide or air before the gas reached the place of combustion; while the

Page 299

subsequent paragraphs will show that the same result is arrived at more
satisfactorily by diluting the acetylene with air during its actual passage
through the burner. It seems highly probable that the beneficial effect of the
earliest methods was due simply or primarily to the dilution, the molecules
of the acetylene being partially protected from the heat of the burner by the
molecules of a gas which was not injured by the high temperature, and
which attracted to itself part of the heat that would otherwise have been
communicated to the hydrocarbon. The modern injector burner exhibits the
same phenomenon of dilution, and is to the same extent efficacious in
preventing polymerisation; but inasmuch as it permits a larger proportion of
air to be introduced, and as the addition is made roughly half-way along the
burner passage, the cold air is more effectual in keeping the former part of
the tip cool, and in jacketing the acetylene during its travel through the
latter part, the bore of which is larger than it otherwise would be.

INJECTOR AND TWIN-FLAME BURNERS.--In practice it is neither
possible to cool an acetylene burner systematically, nor is it desirable to
construct it of such a large mass of some good heat conductor that its
temperature always remains below the dissociation point of the gas. The
earliest direct attempts to keep the burner cool were directed to an
avoidance of contact between the flame of the burning acetylene and the
body of the jet, this being effected by causing the current of acetylene to
inject a small proportion of air through lateral apertures in the burner below
the point of ignition. Such air naturally carries along with it some of the
heat which, in spite of all precautions, still reaches the burner; but it also
apparently forms a temporary annular jacket round the stream of gas,
preventing it from catching fire until it has arrived at an appreciable
distance from the jet. Other attempts were made by placing two non-
injector jets in such mutual positions that the two streams of gas met at an
angle, there to spread fan-fashion into a flat flame. This is really nothing but
the old fish-tail coal-gas burner--which yields its flat flame by identical
impingement of two gas streams--modified in detail so that the bulk of the
flame should be at a considerable distance from the burner instead of
resting directly upon it. In the fish-tail the two orifices are bored in the one
piece of steatite, and virtually join at their external ends; in the acetylene
burner, two separate pieces of steatite, three-quarters of an inch or more
apart, carried by completely separate supports, are each drilled with one

Page 300

hole, and the flame stands vertically midway between them. The two
streams of gas are in one vertical plane, to which the vertical plane of the
flame is at right angles. Neither of these devices singly gave a solution of
the difficulty; but by combining the two--the injector and the twin-flame
principle--the modern flat-flame acetylene burner has been evolved, and is
now met with in two slightly different forms known as the Billwiller and
the Naphey respectively. The latter apparently ought to be called the Dolan.

The essential feature of the Naphey burner is the tip, which is shown in
longitudinal section at A in Fig. 8. It consists of a mushroom headed
cylinder of steatite, drilled centrally with a gas passage, which at its point is
of a diameter suited to pass half the quantity of acetylene that the entire
burner is intended to consume. The cap is provided with four radial air
passages, only two of which are represented in the drawing; these unite in
the centre of the head, where they enter into the longitudinal channel,
virtually a continuation of the gas-way, leading to the point of combustion
by a tube wide enough to pass the introduced air as well as the gas. Being
under some pressure, the acetylene issuing from the jet at the end of the
cylindrical portion of the tip injects air through the four air passages, and
the mixture is finally burnt at the top orifice. As pointed out in Chapter VII.,
the injector jet is so small in diameter that even if the service-pipes leading
to the tip contain an explosive mixture of acetylene and air, the explosion
produced locally if a light is applied to the burner cannot pass backwards
through that jet, and all danger is obviated. One tip only of this description
evidently produces a long, jet-like flame, or a "rat-tail," in which the latent
illuminating power of the acetylene is not developed economically. In
practice, therefore, two of these tips are employed in unison, one of the
commonest methods of holding them being shown at B. From each tip
issues a stream of acetylene mixed with air, and to some extent also

Page 301

surrounded by a jacket of air; and at a certain point, which forms the apex
of an isosceles right-angled triangle having its other angles at the orifices of
the tips, the gas streams impinge, yielding a flat flame, at right- angles, as
mentioned before, to the plane of the triangle. If the two tips are three-
quarters of an inch apart, and if the angle of impingement is exactly 90°, the
distance of each tip from the base of the flame proper will be a trifle over
half an inch; and although each stream of gas does take fire and burn
somewhat before meeting its neighbour, comparatively little heat is
generated near the body of the steatite. Nevertheless, sufficient heat is
occasionally communicated to the metal stems of these burners to cause
warping, followed by a want of alignment in the gas streams, and this
produces distortion of the flame, and possibly smoking. Three methods of
overcoming this defect have been used: in one the arms are constructed
entirely of steatite, in another they are made of such soft metal as easily to
be bent back again into position with the fingers or pliers, in the third each
arm is in two portions, screwing the one into the other. The second type is
represented by the original Phôs burner, in which the curved arms of B are
replaced by a pair of straight divergent arms of thin, soft tubing, joined to a
pair of convergent wider tubes carrying the two tips. The third type is met
with in the Drake burner, where the divergent arms are wide and have an
internal thread into which screws an external thread cut upon lateral
prolongations of the convergent tubes. Thus both the Phôs and the Drake
burner exhibit a pair of exposed elbows between the gas inlet and the two
tips; and these elbows are utilised to carry a screwed wire fastened to an
external milled head by means of which any deposit of carbon in the burner
tubes can be pushed out. The present pattern of the Phôs burner is shown in
Fig. 9, in which A is the burner tip, B the wire or needle, and C the milled
head by which the wire is screwed in and out of the burner tube.

Page 302

Page 303

In the original Billwiller burner, the injector gas orifice was brought
centrally under a somewhat larger hole drilled in a separate sheet of
platinum, the metal being so carried as to permit entry of air. In order to
avoid the expense of the platinum, the same principle was afterwards used
in the design of an all-steatite head, which is represented at D in Fig. 8. The
two holes there visible are the orifices for the emission of the mixture of
acetylene with indrawn air, the proper acetylene jets lying concentrically
below these in the thicker portions of the heads. These two types of burner
have been modified in a large number of ways, some of which are shown at
C, E, and F; the air entering through saw- cuts, lateral holes, or an annular
channel. Burners resembling F in outward form are made with a pair of
injector jets and corresponding air orifices on each head, so as to produce a
pair of names lying in the same plane, "end-on" to one another, and

Page 304

projecting at either side considerably beyond the body of the burner; these
have the advantage of yielding no shadow directly underneath. A burner of
this pattern, viz., the "Wonder," which is sold in this country by Hannam's,
Ltd., is shown in Fig. 10, alongside the single-flame "Wonder" burner,
which is largely used, especially in the United States. Another two-flame
burner, made of steatite, by J. von Schwarz of Nuremberg, and sold by L.
Wiener of London, is shown in Fig. 11. Burners of the Argand type have
also been manufactured, but have been unsuccessful. There are, of course,
endless modifications of flat-flame burners to be found on the markets, but
only a few need be described. A device, which should prove useful where it
may be convenient to be able to turn one or more burners up or down from
the same common distant spot, has been patented by Forbes. It consists of
the usual twin-injector burner fitted with a small central pinhole jet; and
inside the casing is a receptacle containing a little mercury, the level of
which is moved by the gas pressure by an adaptation of the displacement
principle. When the main is carrying full pressure, both of the jets proper
are alight, and the burner behaves normally, but if the pressure is reduced to
a certain point, the movement of the mercury seals the tubes leading to the
main jets, and opens that of the pilot flame, which alone remains alight till
the pressure is increased again. Bray has patented a modification of the
Naphey injector tip, which is shown in Fig. 12. It will be observed that the
four air inlets are at right-angles to the gas-way; but the essential feature of
the device is the conical orifice. By this arrangement it is claimed that firing
back never occurs, and that the burner can be turned down and left to give a
small flame for considerable periods of time without fear of the apertures
becoming choked or distorted. As a rule burners of the ordinary type do not
well bear being turned down; they should either be run at full power or
extinguished completely. The "Elta" burner, made by Geo. Bray and Co.,
Ltd., which is shown in Fig. 13, is an injector or atmospheric burner which
may be turned low without any deposition of carbon occurring on the tips.
A burner of simple construction but which cannot be turned low is the
"Luta," made by the same firm and shown in Fig. 14. Of the non-
atmospheric type the "Sansair," also made by Geo. Bray and Co., Ltd., is
extensively used. It is shown in Fig. 15. In order to avoid the warping,
through the heat of the flame, of the arms of burners which sometimes
occurs when they are made of metal, a number of burners are now made
with the arms wholly of steatite. One of the best-known of these, of the

Page 305

injector type, is the "Kona," made by Falk, Stadelmann and Co., of London.
It is shown in Fig. 16, fitted with a screw device for adjusting the flow of
gas, so that when this adjuster has been set to give a flame of the proper
size, no further adjustment by means of the gas-tap is necessary. This saves
the trouble of manipulating the tap after the gas is lighted. The same
adjusting device may also be had fitted to the Phôs burner (Fig. 9) or to the
"Orka" burner (Fig. 17), which is a steatite- tip injector burner with metal
arms made by Falk, Stadelmann and Co., Ltd. A burner with steatite arms,
made by J. von Schwarz of Nuremberg, and sold in this country by L.
Wiener of London, is shown in Fig. 18.

ILLUMINATING DUTY.--The illuminating value of ordinary self-
luminous acetylene burners in different sizes has been examined by various
photometrists. For burners of the Naphey type Lewes gives the following
table:

___________________________________________________________
| | | | | |
| | | Gas | | Candles |
| Burner. | Pressure, | Consumed, | Light in | per |
| | Inches | Cubic Feet | Candles. | Cubic Foot. |

Page 306

| | | per Hour. | | |
|_________|___________|____________|__________|_____________|
| | | | | |
| No. 6 | 2.0 | 0.155 | 0.794 | 5.3 |
| " 8 | 2.0 | 0.27 | 3.2 | 11.6 |
| " 15 | 2.0 | 0.40 | 8.0 | 20.0 |
| " 25 | 2.0 | 0.65 | 17.0 | 26.6 |
| " 30 | 2.0 | 0.70 | 23.0 | 32.85 |
| " 42 | 2.0 | 1.00 | 34.0 | 34.0 |
|_________|___________|____________|__________|_____________|

From burners of the Billwiller type Lewes obtained in 1899 the values:

___________________________________________________________
| | | | | |
| | | Gas | | Candles |
| Burner. | Pressure, | Consumed, | Light in | per |
| | Inches | Cubic Feet | Candles. | Cubic Foot. |
| | | per Hour. | | |
|_________|___________|____________|__________|_____________|
| | | | | |
| No. 1 | 2.0 | 0.5 | 7.0 | 11.0 |
| " 2 | 2.0 | 0.75 | 21.0 | 32.0 |
| " 3 | 2.0 | 0.75 | 28.0 | 37.3 |
| " 4 | 3.0 | 1.2 | 48.0 | 40.0 |
| " 5 | 3.5 | 2.0 | 76.0 | 38.0 |
|_________|___________|____________|__________|_____________|

Neuberg gives these figures for different burners (1900) as supplied by
Pintsch:

_______________________________________________________________
_______
| | | | |
|
| | Gas | | Candles |
|
| Burner. | Pressure, | Consumed, | Light in |
per |
| | Inches | Cubic Feet | Candles. |
Cubic Foot. |
| | | per Hour. | |
|

Page 307

|____________________|___________|____________|__________|_____
________|
| | | | |
|
| No. 0, slit burner | 3.9 | 1.59 | 59.2 |
37.3 |
| " 00000 fishtail | 1.6 | 0.81 | 31.2 |
38.5 |
| Twin burner No. 1 | 3.2 | 0.32 | 13.1 |
40.8 |
| " " " 2 | 3.2 | 0.53 | 21.9 |
41.3 |
| " " " 3 | 3.2 | 0.74 | 31.0 |
41.9 |
| " " " 4 | 3.2 | 0.95 | 39.8 |
41.9 |
|____________________|___________|____________|__________|_____
________|

The actual candle-power developed by each burner was not quoted by
Neuberg, and has accordingly been calculated from his efficiency values. It
is noteworthy, and in opposition to what has been found by other
investigators as well as to strict theory, that Neuberg represents the
efficiencies to be almost identical in all sizes of the same description of
burner, irrespective of the rate at which it consumes gas.

Writing in 1902, Capelle gave for Stadelmann's twin injector burners the
following figures; but as he examined each burner at several different
pressures, the values recorded in the second, third, and fourth columns are
maxima, showing the highest candle-power which could be procured from
each burner when the pressure was adjusted so as to cause consumption to
proceed at the most economical rate. The efficiency values in the fifth
column, however, are the mean values calculated so as to include all the
data referring to each burner. Capelle's results have been reproduced from
the original on the basis that 1 bougie décimale equals 0.98 standard
English candle, which is the value he himself ascribes to it (1 bougie
décimale equals 1.02 candles is the value now accepted).

_______________________________________________________________
______

Page 308

| | | | |
|
| Nominal | Best | Actual Consumption | Maximum |
Average |
| Consumption,| Pressure| at Stated Pressure. | Light in |
Candles per|
| Litres. | Inches. | Cubic Feet per Hour.| Candles. |
Cubic Foot.|
|_____________|_________|_____________________|__________|_____
_______|
| | | | |
|
| 10 | 3.5 | 0.40 | 8.4 |
21.1 |
| 15 | 2.8 | 0.46 | 16.6 |
33.3 |
| 20 | 3.9 | 0.64 | 25.1 |
40.0 |
| 25 | 3.5 | 0.84 | 37.8 |
46.1 |
| 30 | 3.5 | 0.97 | 48.2 |
49.4 |
|_____________|_________|_____________________|__________|_____
_______|

Some testings of various self-luminous burners of which the results were
reported by R. Granjon in 1907, gave the following results for the duty of
each burner, when the pressure was regulated for each burner to that which
afforded the maximum illuminating duty. The duty in the original paper is
given in litres per Carcel-hour. The candle has been taken as equal to 0.102
Carcel for the conversion to candles per cubic foot.

_______________________________________________________________
____
| | | |
|
| | Nominal | Best | Duty.
Candles |
| Burner. | Consumption.| Pressure. | per cubic
foot. |
|_______________________|_____________|__________
|_________________|
| | | |
|

Page 309

| | Litres. | Inches. |
|
| Twin . . . . | 10 | 2.76 | 21.2
|
| " . . . . | 20 | 2.76 | 23.5
|
| " . . . . | 25 | 3.94 | 30.2
|
| " . . . . | 30 | 3.94-4.33 | 44.8
|
| ", (pair of flames) | 35 | 3.55-3.94 | 45.6
|
| Bray's "Manchester" | 6 | 1.97 | 18.8
|
| " | 20 | 1.97 | 35.6
|
| " | 40 | 2.36 | 42.1
|
| Rat-tail . . . | 5 | 5.5 | 21.9
|
| " . . . | 8 | 4.73 | 25.0
|
| Slit or batswing . | 30 | 1.97-2.36 | 37.0
|
|_______________________|_____________|___________|____________
_____|

Granjon has concluded from his investigations that the Manchester or fish-
tail burners are economical when they consume 0.7 cubic foot per hour and
when the pressure is between 2 and 2.4 inches. When these burners are used
at the pressure most suitable for twin burners their consumption is about
one-third greater than that of the latter per candle-hour. The 25 to 35 litres-
per-hour twin burners should be used at a pressure higher by about 1 inch
than the 10 to 20 litres-per-hour twin burners.

At the present time, when the average burner has a smaller hourly
consumption than 1 foot per hour, it is customary in Germany to quote the
mean illuminating value of acetylene in self-luminous burners as being 1
Hefner unit per 0.70 litre, which, taking

1 Hefner unit = 0.913 English candle

1 English candle = 1.095 Hefner units,

Page 310

works out to an efficiency of 37 candles per foot in burners probably
consuming between 0.5 and 0.7 foot per hour.

Even when allowance is made for the difficulties in determining
illuminating power, especially when different photometers, different
standards of light, and different observers are concerned, it will be seen that
these results are too irregular to be altogether trustworthy, and that much
more work must be done on this subject before the economy of the
acetylene flame can be appraised with exactitude. However, as certain fixed
data are necessary, the authors have studied those and other determinations,
rejecting some extreme figures, and averaging the remainder; whence it
appears that on an average twin-injector burners of different sizes should
yield light somewhat as follows:

_______________________________________________________
| | | |
| Size of Burner in | Candle-power | Candles |
| Cubic Feet per Hour. | Developed. | per Cubic Foot. |
|______________________|______________|_________________|
| | | |
| 0.5 | 18.0 | 35.9 |
| 0.7 | 27.0 | 38.5 |
| 1.0 | 45.6 | 45.6 |
|______________________|______________|_________________|

In the tabular statement in Chapter I. the 0.7-foot burner was taken as the
standard, because, considering all things, it seems the best, to adopt for
domestic purposes. The 1-foot burner is more economical when in the best
condition, but requires a higher gas pressure, and is rather too powerful a
unit light for good illuminating effect; the 0.5 burner naturally gives a better
illuminating effect, but its economy is surpassed by the 0.7-foot burner,
which is not too powerful for the human eye.

For convenience of comparison, the illuminating powers and duties of the
0.5- and 0.7-foot acetylene burners may be given in different ways:

ILLUMINATING POWER OF SELF-LUMINOUS ACETYLENE.

_0.7-foot Burner._ | _Half-foot Burner._

Page 311

|
1 litre = 1.36 candles. | 1 litre = 1.27
candles.
1 cubic foot = 38.5 candles. | 1 cubic foot = 35.9
candles.
1 candle = 0.736 litre. | 1 candle = 0.79
litre.
1 candle = 0.026 cubic foot. | 1 candle = 0.028
cubic foot.

If the two streams of gas impinge at an angle of 90°, twin-injector burners
for acetylene appear to work best when the gas enters them at a pressure of
2 to 2.5 inches; for a higher pressure the angle should be made a little acute.
Large burners require to have a wider distance between the jets, to be
supplied with acetylene at a higher pressure, and to be constructed with a
smaller angle of impingement. Every burner, of whatever construction and
size, must always be supplied with gas at its proper pressure; a pressure
varying from time to time is fatal.

It is worth observing that although injector burners are satisfactory in
practice, and are in fact almost the only jets yet found to give prolonged
satisfaction, the method of injecting air below the point of combustion in a
self-luminous burner is in some respects wrong in principle. If acetylene
can be consumed without polymerisation in burners of the simple fish-tail
or bat's-wing type, it should show a higher illuminating efficiency. In 1902
Javal stated that it was possible to burn thoroughly purified acetylene in
twin non-injector burners, provided the two jets, made of steatite as usual,
were arranged horizontally instead of obliquely, the two streams of gas then
meeting at an angle of 180°, so as to yield an almost circular flame.
According to Javal, whereas carbonaceous growths were always produced
in non-injector acetylene burners with either oblique or horizontal jets, in
the former case the growths eventually distorted the gas orifices, but in the
latter the carbon was deposited in the form of a tube, and fell off from the
burner by its own weight directly it had grown to a length of 1.2 or 1.5
millimetres, leaving the jets perfectly clear and smooth. Javal has had such
a burner running for 10 or 12 hours per day for a total of 2071 hours; it did
not need cleaning out on any occasion, and its consumption at the end of the
period was the same as at first. He found that it was necessary that the tips
should be of steatite, and not of metal or glass; that the orifices should be

Page 312

drilled in a flat surface rather than at the apex of a cone, and that the
acetylene should be purified to the utmost possible extent. Subsequent
experience has demonstrated the possibility of constructing non-injector
burners such as that shown in Fig. 13, which behave satisfactorily even
though the jets are oblique. But with such burners trouble will inevitably
ensue unless the gas is always purified to a high degree and is tolerably dry
and well filtered. Non-injector burners should not be used unless special
care is taken to insure that the installation is consistently operated in an
efficient manner in these respects.

GLOBES, &C.--It does not fall within the province of the present volume
to treat at length of chimneys, globes, or the various glassware which may
be placed round a source of light to modify its appearance. It should be
remarked, however, that obedience to two rules is necessary for complete
satisfaction in all forms of artificial illumination. First, no light much
stronger in intensity than a single candle ought ever to be placed in such a
position in an occupied room that its direct rays can reach the eye, or the
vision will be temporarily, and may be permanently, injured. Secondly,
unless economy is to be wholly ignored, no coloured or tinted globe or
shade should ever be put round a source of artificial light. The best material
for the construction of globes is that which possesses the maximum of
translucency coupled with non-transparency, i.e., a material which passes
the highest proportion of the light falling upon it, and yet disperses that
light in such different directions that the glowing body cannot be seen
through the globe. Very roughly speaking, plain white glass, such as that of
which the chimneys of oil-lamps and incandescent gas-burners are
composed, is quite transparent, and therefore affords no protection to the
eyesight; a protective globe should be rather of ground or opal glass, or of
plain glass to which a dispersive effect has been given by forming small
prisms on its inner or outer surface, or both. Such opal, ground, or
dispersive shades waste much light in terms of illuminating power, but
waste comparatively little in illuminating effect well designed, they may
actually increase the illuminating effect in certain positions; a tinted globe,
even if quite plain in figure, wastes both illuminating power and effect, and
is only to be tolerated for so-believed aesthetic reasons. Naturally no globe
must be of such figure, or so narrow at either orifice, as to distort the shape
of the unshaded acetylene flame--it is hardly necessary to say this now, but

Page 313

some years ago coal-gas globes were constructed with an apparent total
disregard of this fundamental point.

Page 314

CHAPTER IX
INCANDESCENT BURNERS--HEATING APPARATUS--
MOTORS--AUTOGENOUS SOLDERING

MERITS OF LIGHTING BY INCANDESCENT MANTLES.--It has
already been shown that acetylene bases its chief claim for adoption as an
illuminant in country districts upon the fact that, when consumed in simple
self- luminous burners, it gives a light comparable in all respects save that
of cost to the light of incandescent coal-gas. The employment of a mantle is
still accompanied by several objections which appear serious to the average
householder, who is not always disposed either to devote sufficient attention
to his burners to keep them in a high state of efficiency or to contract for
their maintenance by the gas company or others. Coal-gas cannot be burnt
satisfactorily on the incandescent system unless the glass chimneys and
shades are kept clean, unless the mantles are renewed as soon as they show
signs of deterioration, and, perhaps most important of all, unless the burners
are frequently cleared of the dust which collects round the jets. For this
reason luminous acetylene ranks with luminous coal-gas in convenience
and simplicity, while ranking with incandescent coal-gas in hygienic value.
Very similar remarks apply to paraffin, and, in certain countries, to
denatured alcohol. Since those latter illuminants are also available in rural
places where coal-gas is not laid on, luminous acetylene is a less
advantageous means of procuring artificial light than paraffin (and on
occasion than coal-gas and alcohol when the latter fuels are burnt under the
mantle), if the pecuniary aspect of the question is the only one considered.
Such a comparison, however, is by no means fair; for if coal- gas, paraffin,
and alcohol can be consumed on the incandescent system, so can acetylene;
and if acetylene is hygienically equal to incandescent coal-gas, it is superior
thereto when also burnt under the mantle. Nevertheless there should be one
minor but perfectly irremediable defect in incandescent acetylene, viz., a
sacrifice of that characteristic property of the luminous gas to emit a light
closely resembling that of the sun in tint, which was mentioned in Chapter
1. Self-luminous acetylene gives the whitest light hitherto procurable

Page 315

without special correction of the rays, because its light is derived from
glowing particles of carbon which happen to be heated (because of the high
flame temperature) to the best possible temperature for the emission of pure
white light. The light of any combustible consumed on the "incandescent"
system is derived from glowing particles of ceria, thoria, or similar metallic
oxides; and the character or shade of the light they emit is a function, apart
from the temperature to which they are raised, of their specific chemical
nature. Still, the light of incandescent acetylene is sufficiently pleasant, and
according to Caro is purer white than that of incandescent coal-gas; but
lengthy tests carried out by one of the authors actually show it to be
appreciably inferior to luminous acetylene for colour-matching, in which
the latter is known almost to equal full daylight, and to excel every form of
artificial light except that of the electric arc specially corrected by means of
glass tinted with copper salts.

CONDITIONS FOR INCANDESCENT ACETYLENE LIGHTING.--For
success in the combustion of acetylene on the incandescent system,
however, several points have to be observed. First, the gas must be
delivered at a strictly constant pressure to the burner, and at one which
exceeds a certain limit, ranging with different types and different sizes of
burner from 2 to 4 or 5 inches of water. (The authors examined, as long ago
as 1903, an incandescent burner of German construction claimed to work at
a pressure of 1.5 inches, which it was almost impossible to induce to fire
back to the jets however slowly the cock was manipulated, provided the
pressure of the gas was maintained well above the point specified. But
ordinarily a pressure of about 4 inches is used with incandescent acetylene
burners.) Secondly, it is necessary that the acetylene shall at all times be
free from appreciable admixture with air, even 0.5 per cent, being highly
objectionable according to Caro; so that generators introducing any
noteworthy amount of air into the holder each time their decomposing
chambers are opened for recharging are not suitable for employment when
incandescent burners are contemplated. The reason for this will be more
apparent later on, but it depends on the obvious fact that if the acetylene
already contains an appreciable proportion of air, when a further quantity is
admitted at the burner inlets, the gaseous mixture contains a higher
percentage of oxygen than is suited to the size and design of the burner, so
that flashing back to the injector jets is imminent at any moment, and may

Page 316

be determined by the slightest fluctuation in pressure--if, indeed, the flame
will remain at the proper spot for combustion at all. Thirdly, the fact that the
acetylene which is to be consumed under the mantle must be most
rigorously purified from phosphorus compounds has been mentioned in
Chapter V. Impure acetylene will often destroy a mantle in two or three
hours; but with highly purified gas the average life of a mantle may be
taken, according to Giro, at 500 or 600 hours. It is safer, however, to
assume a rather shorter average life, say 300 to 400 burning hours. Fourthly,
owing to the higher pressure at which acetylene must be delivered to an
incandescent burner and to the higher temperature of the acetylene flame in
comparison with coal-gas, a mantle good enough to give satisfactory results
with the latter does not of necessity answer with acetylene; in fact, the
authors have found that English Welsbach coal-gas mantles of the small
sizes required by incandescent acetylene burners are not competent to last
for more than a very few hours, although, in identical conditions, mantles
prepared specially for use with acetylene have proved durable. The
atmospheric acetylene flame, too, differs in shape from an atmospheric
flame of coal-gas, and it does not always happen that a coal- gas mantle
contracts to fit the former; although it usually emits a better light (because it
fits better) after some 20 hours use than at first. Caro has stated that to
derive the best results a mantle needs to contain a larger proportion of ceria
than the 1 per cent. present in mantles made according to the Welsbach
formula, that it should be somewhat coarser in mesh, and have a large
orifice at the head. Other authorities hold that mantles for acetylene, should
contain other rare earths besides the thoria and ceria of which the coal-gas
mantles almost wholly consist. It seems probable, however, that the
composition of the ordinary impregnating fluid need not be varied for
acetylene mantles provided it is of the proper strength and the mantles are
raised to a higher temperature in manufacture than coal-gas mantles by the
use of either coal-gas at very high pressure or an acetylene flame. The
thickness of the substance of the mantle cannot be greatly increased with a
view to attaining greater stability without causing a reduction in the light
afforded. But the shape should be such that the mantle conforms as closely
as possible to the acetylene Bunsen flame, which differs slightly with
different patterns of incandescent burner heads. According to L. Cadenel,
the acetylene mantle should be cylindrical for the lower two- thirds of its
length, and slightly conical above, with an opening of moderate size at the

Page 317

top. The head of the mantle should be of slighter construction than that of
coal-gas mantles. Fifthly, generators belonging to the automatic variety,
which in most forms inevitably add more or less air to the acetylene every
time they are cleaned or charged, appear to have achieved most popularity
in Great Britain; and these frequently do not yield a gas fit for use with the
mantle. This state of affairs, added to what has just been said, makes it
difficult to speak in very favourable terms of the incandescent acetylene
light for use in Great Britain. But as the advantages of an acetylene not
contaminated with air are becoming more generally recognised, and
mantles of several different makes are procurable more cheaply,
incandescent acetylene is now more practicable than hitherto. Carburetted
acetylene or "carburylene," which is discussed later, is especially suitable
for use with mantle burners.

ATMOSPHERIC ACETYLENE BURNERS.--The satisfactory employment
of acetylene in incandescent burners, for boiling, warming, and cooking
purposes, and also to some extent as a motive power in small engines,
demands the production of a good atmospheric or non-luminous flame, i.e.,
the construction of a trustworthy burner of the Bunsen type. This has been
exceedingly difficult to achieve for two reasons: first, the wide range over
which mixtures of acetylene and air are explosive; secondly, the high speed
at which the explosive wave travels through such a mixture. It has been
pointed out in Chapter VIII. that a Bunsen burner is one in which a certain
proportion of air is mixed with the gas before it arrives at the actual point of
ignition; and as that proportion must be such that the mixture falls between
the upper and lower limits of explosibility, there is a gaseous mixture in the
burner tube between the air inlets and the outlet which, if the conditions are
suitable, will burn with explosive force: that is to say, will fire back to the
air jets when a light is applied to the proper place for combustion. Such an
explosion, of course, is far too small in extent to constitute any danger to
person or property; the objection to it is simply that the shock of the
explosion is liable to fracture the fragile incandescent mantle, while the gas,
continuing to burn within the burner tube (in the case of a warming or
cooking stove), blocks up that tube with carbon, and exhibits the other well-
known troubles of a coal-gas stove which has "fired back."

Page 318

It has been shown, however, in Chapter VI. that the range over which
mixtures of acetylene and air are explosive depends on the size of the
vessel, or more particularly on the diameter of the tube, in which they are
stored; so that if the burner tube between the air inlets and the point of
ignition can be made small enough in diameter, a normally explosive
mixture will cease to exhibit explosive properties. Manifestly, if a tube is
made very small in diameter, it will only pass a small volume of gas, and it
may be useless for the supply of an atmospheric burner; but Le Chatelier's
researches have proved that a tube may be narrowed at one spot only, in
such fashion that the explosive wave refuses to pass the constriction, while
the virtual diameter of the tube, as far as passage of gas is concerned,
remains considerably larger than the size of the constriction itself.
Moreover, inasmuch as the speed of propagation of the explosion is strictly
fixed by the conditions prevailing, if the speed at which the mixture, of
acetylene and air travels from the air inlets to the point of ignition is more
rapid than the speed at which the explosion tends to travel from the point of
ignition to the air inlets, the said mixture of acetylene and air will burn
quietly at the orifice without attempting to fire backwards into the tube. By
combining together these two devices: by delivering the acetylene to the
injector jet at a pressure sufficient to drive the mixture of gas and air
forward rapidly enough, and by narrowing the leading tube either wholly or
at one spot to a diameter small enough, it is easy to make an atmospheric
burner for acetylene which behaves perfectly as long as it is fairly alight,
and the supply of gas is not checked; but further difficulties still remain,
because at the instant of lighting and extinguishing, i.e., while the tap is
being turned on or off, the pressure of the gas is too small to determine a
flow of acetylene and air within the tube at a speed exceeding that of the
explosive wave; and therefore the act of lighting or extinguishing is very
likely to be accompanied by a smart explosion severe enough to split the
mantle, or at least to cause the burner to fire back. Nevertheless, after
several early attempts, which were comparative failures, atmospheric
acetylene burners have been constructed that work quite satisfactorily, so
that the gas has become readily available for use under the mantle, or in
heating stoves. Sometimes success has been obtained by the employment of
more than one small tube leading to a common place of ignition, sometimes
by the use of two or more fine wire- gauze screens in the tube, sometimes
by the addition of an enlarged head to the burner in which head alone

Page 319

thorough mixing of the gas and air occurs, and sometimes by the
employment of a travelling sleeve which serves more or less completely to
block the air inlets.

DUTY OF INCANDESCENT ACETYLENE BURNERS.--Granting that
the petty troubles and expenses incidental to incandescent lighting are not
considered prohibitive--and in careful hands they are not really serious--
and that mantles suitable for acetylene are employed, the gas may be
rendered considerably cheaper to use per unit of light evolved by
consuming it in incandescent burners. In Chapter VIII. it was shown that the
modern self-luminous, l/2-foot acetylene burner emits a light of about 1.27
standard English candles per litre-hour. A large number of incandescent
burners, of German and French construction, consuming from 7.0 to 22.2
litres per hour at pressures ranging between 60 and 120 millimetres have
been examined by Caro, who has found them to give lights of from 10.8 to
104.5 Hefner units, and efficiencies of from 2.40 to 5.50 units per litre-hour.
Averaging his results, it may be said that incandescent burners consuming
from 10 to 20 litres per hour at pressures of 80 or 100 millimetres yield a
light of 4.0 Hefner units per litre- hour. Expressed in English terms,
incandescent acetylene burners consuming 0.5 cubic foot per hour at a
pressure of 3 or 4 inches give the duties shown in the following table, which
may advantageously be compared with that printed in Chapter VIII., page
239, for the self-luminous gas:

ILLUMINATING POWER OF INCANDESCENT ACETYLENE. HALF-
FOOT BURNERS.

1 litre = 3.65 candles | 1 candle = 0.274 litre.
1 cubic foot = 103.40 candles. | 1 candle = 0.0097 cubic
foot.

A number of tests of the Güntner or Schimek incandescent burners of the 10
and 15 litres-per-hour sizes, made by one of the authors in 1906, gave the
following average results when tested at a pressure of 4 inches:

_______________________________________________________________

Page 320

__
| | | |
|
| Nominal size | Rate of Consumption per | Light in | Duty
|
| of Burner. | Hour | Candles | Candles
per |
| | | | Cubic
Foot |
|______________|_________________________|__________|__________
___|
| | | | |
|
| Litres. | Cubic Foot | Litres | |
|
| 10 | 0.472 | 13.35 | 46.0 | 97.4
|
| 15 | 0.663 | 18.80 | 70.0 | 105.5
|
|______________|____________|____________|__________|__________
___|

These figures indicate that the duty increases slightly with the size of the
burner. Other tests showed that the duty increased more considerably with
an increase of pressure, so that mantles used, or which had been previously
used, at a pressure of 5 inches gave duties of 115 to 125 candles per cubic
foot.

It should be noted that the burners so far considered are small, being
intended for domestic purposes only; larger burners exhibit higher
efficiencies. For instance, a set of French incandescent acetylene burners
examined by Fouché showed:

_______________________________________________________________
__
| | | | |
|
| Size of Burner | Pressure | Cubic Feet | Light in | Candles
per |
| in Litres. | Inches. | per Hour. | Candles. | Cubic
Feet. |
|________________|__________|____________|__________|__________
___|

Page 321

| | | | |
|
| 20 | 5.9 | 0.71 | 70 | 98.6
|
| 40 | 5.9 | 1.41 | 150 | 106.4
|
| 70 | 5.9 | 2.47 | 280 | 113.4
|
| 120 | 5.9 | 4.23 | 500 | 118.2
|
|________________|__________|____________|__________|__________
___|

By increasing the pressure at which acetylene is introduced into burners of
this type, still larger duties may be obtained from them:

_______________________________________________________________
__
| | | | |
|
| Size of Burner | Pressure | Cubic Feet | Light in | Candles
per |
| in Litres. | Inches. | per Hour. | Candles. | Cubic
Feet. |
|________________|__________|____________|__________|__________
___|
| | | | |
|
| 55 | 39.4 | 1.94 | 220 | 113.4
|
| 100 | 39.4 | 3.53 | 430 | 121.8
|
| 180 | 39.4 | 6.35 | 820 | 129.1
|
| 260 | 27.6 | 9.18 | 1300 | 141.6
|
|________________|__________|____________|__________|__________
___|

High-power burners such as these are only fit for special purposes, such as
lighthouse illumination, or optical lantern work, &c.; and they naturally
require mantles of considerably greater tenacity than those intended for
employment with coal-gas. Nevertheless, suitable mantles can be, and are

Page 322

being, made, and by their aid the illuminating duty of acetylene can be
raised from the 30 odd candles per foot of the common 0.5-foot self-
luminous jet to 140 candles or more per foot, which is a gain in efficiency
of 367 per cent., or, neglecting upkeep and sundries and considering only
the gas consumed, an economy of nearly 79 per cent.

In 1902, working apparently with acetylene dissolved under pressure in
acetone (cf. Chapter XI.), Lewes obtained the annexed results with the
incandescent gas:

________________________________________________________
| | | | |
| Pressure. | Cubic Feet | Candle Power | Candles per |
| Inches. | per Hour. | Developed. | Cubic Foot. |
|___________|_____________|______________|______________|
| | | | |
| 8 | 0.883 | 65 | 73.6 |
| 9 | 0.94 | 72 | 76.0 |
| 10 | 1.00 | 146 | 146.0 |
| 12 | 1.06 | 150 | 141.2 |
| 15 | 1.25 | 150 | 120.0 |
| 20 | 1.33 | 166 | 124.8 |
| 25 | 1.50 | 186 | 123.3 |
| 40 | 2.12 | 257 | 121.2 |
|___________|_____________|______________|______________|

It will be seen that although the total candle-power developed increases
with the pressure, the duty of the burner attained a maximum at a pressure
of 10 inches. This is presumably due to the fact either that the same burner
was used throughout the tests, and was only intended to work at a pressure
of 10 inches or thereabouts, or that the larger burners were not so well
constructed as the smaller ones. Other investigators have not given this
maximum of duty with a medium-sized or medium-driven burner; but
Lewes has observed a similar phenomenon in the case of 0.7 to 0.8 cubic
foot self-luminous jets.

Figures, however, which seem to show that the duty of incandescent
acetylene does not always rise with the size of the burner or with the
pressure at which the gas is delivered to it, have been published in
connexion with the installation at the French lighthouse at Chassiron, the

Page 323

northern point of the Island of Oléron. Here the acetylene is generated in
hand-fed carbide-to-water generators so constructed as to give any pressure
up to nearly 200 inches of water column; purified by means of heratol, and
finally delivered to a burner composed of thirty- seven small tubes, which
raises to incandescence a mantle 55 millimetres in diameter at its base. At a
pressure of 7.77 inches of water, the burner passes 3.9 cubic feet of
acetylene per hour, and at a pressure of 49.2 inches (the head actually used)
it consumes 20.06 cubic feet per hour. As shown by the following table,
such increment of gas pressure raises the specific intensity of the light, i.e.,
the illuminating power per unit of incandescent surface, but it does not
appreciably raise the duty or economy of the gas. Manifestly, in terms of
duty alone, a pressure of 23.6 inches of water-column is as advantageous as
the higher Chassiron figures; but since intensity of light is an important
matter in a lighthouse, it is found better on the whole to work the generators
at a pressure of 49.2 inches. In studying these figures referring to the French
lighthouse, it is interesting to bear in mind that when ordinary six-wick
petroleum oil burners wore used in the same place, the specific intensity of
the light developed was 75 candle-power per square inch, and when that
plant was abandoned in favour of an oil-gas apparatus, the incandescent
burner yielded 161 candle-power per square inch; substitution of
incandescent acetylene under pressure has doubled the brilliancy of the
light.

___________________________________________________________
| | | |
| | Duty. | Intensity. |
| Pressure in Inches. | Candle-power per | Candle-power per |
| | Cubic Foot. | Square Inch. |
|_____________________|__________________|__________________|
| | | |
| 7.77 | 105.5 | 126.0 |
| 23.60 | 106.0 | 226.0 |
| 31.50 | 110.0 | 277.0 |
| 39.40 | 110.0 | 301.0 |
| 47.30 | 106.0 | 317.0 |
| 49.20 | 104.0 | 324.9 |
| 196.80 | 110.0 | 383.0 |
|_____________________|__________________|__________________|

Page 324

When tested in modern burners consuming between 12 and 18 litres per
hour at a pressure of 100 millimetres (4 inches), some special forms of
incandescent mantles constructed of ramie fibre, which in certain respects
appears to be better suited than cotton for use with acetylene, have shown
the following degree of loss in illuminating power after prolonged
employment (Caro):

_Luminosity in Hefner Units._

________________________________________________________
| | | | | |
| Mantle. | New. | After | After | After |
| | | 100 Hours. | 200 Hours. | 400 Hours. |
|_________|_______|____________|____________|____________|
| | | | | |
| No. 1. | 53.2 | 51.8 | 50.6 | 49.8 |
| No. 2. | 76.3 | 75.8 | 73.4 | 72.2 |
| No. 3. | 73.1 | 72.5 | 70.1 | 68.6 |
|_________|_______|____________|____________|____________|

It will be seen that the maximum loss of illuminating power in 400 hours
was 6.4 per cent., the average loss being 6.0 per cent.

TYPICAL INCANDESCENT BURNERS.--Of the many burners for
lighting by the use of incandescent mantles which have been devised, a few
of the more widely used types may be briefly referred to. There is no doubt
that finality in the design of these burners has not yet been reached, and that
improvements in the direction of simplification of construction and in
efficiency and durability will continue to be made.

Among the early incandescent burners, one made by the Allgemeine Carbid
und Acetylen Gesellschaft of Berlin in 1900 depended on the narrowness of
the mixing tube and the proportioning of the gas nipple and air inlets to
prevent lighting-back. There was a wider concentric tube round the upper
part of the mixing tube, and the lower part of the mantle fitted round this.
The mouth of the mixing tube of this 10-litres-per-hour burner was 0.11
inch in diameter, and the external diameter of the middle cylindrical part of
the mixing tube was 0.28 inch. There was no gauze diaphragm or stuffing,
and firing-back did not occur until the pressure was reduced to about 1.5

Page 325

inches. The same company later introduced a burner differing in several
important particulars from the one just described. The comparatively
narrow stem of the mixing tube and the proportions of the gas nipple and air
inlets were retained, but the mixing tube was surmounted by a wide
chamber or burner head, in which naturally there was a considerable
reduction in the rate of flow of the gas. Consequently it was found
necessary to introduce a gauze screen into the burner head to prevent firing
back. The alterations have resulted in the lighting duty of the burner being
considerably improved. Among other burners designed about 1900 may be
mentioned the Ackermann, the head of which consisted of a series of tubes
from each of which a jet of flame was produced, the Fouché, the Weber, and
the Trendel. Subsequently a tubular-headed burner known as the Sirius has
been produced for the consumption of acetylene at high pressure (20 inches
and upwards).

The more recent burners which have been somewhat extensively used
include the "Schimek," made by W. Güntner of Vienna, which is shown in
Fig. 19. It consists of a tapering narrow injecting nozzle within a conical
chamber C which is open below, and is surmounted by the mixing tube over
which telescopes a tube which carries the enlarged burner head G, and the
chimney gallery D. There are two diaphragms of gauze in the burner head
to prevent firing back, and one in the nozzle portion of the burner. The
conical chamber has a perforated base-plate below which is a circular plate
B which rotates on a screw cut on the lower part of the nozzle portion A of
the burner. This plate serves as a damper to control the amount of air
admitted through the base of the conical chamber to the mixing tube. There
are six small notches in the lower edge of the conical chamber to prevent
the inflow of air being cut of entirely by the damper. The mixing tube in
both the 10-litre and the 15-litre burner is about 0.24 inch in internal
diameter but the burner head is nearly 0.42 inch in the 10-litre and 0.48 inch
in the 15-litre burner. The opening in the head of the burner through which
the mixture of gas and air escapes to the flame is 0.15 and 0.17 inch in
diameter in these two sizes respectively. The results of some testings made
with Schimek burners have been already given.

Page 326

The "Knappich" burner, made by the firm of Keller and Knappich of
Augsburg, somewhat resembles the later pattern of the Allgemeine Carbid
und Acetylen Gesellschaft. It has a narrow mixing tube, viz., 0.2 inch in
internal diameter, and a wide burner head, viz., 0.63 inch in internal
diameter for the 25-litre size. The only gauze diaphragm is in the upper part
of the burner head. The opening in the cap of the burner head, at which the
gas burns, is 0.22 inch in diameter. The gas nipple extends into a domed
chamber at the base of the mixing tube, and the internal air is supplied
through four holes in the base-plate of that chamber. No means of
regulating the effective area of the air inlet holes are provided.

The "Zenith" burner, made by the firm of Gebrüder Jacob of Zwickau, more
closely resembles the Schimek, but the air inlets are in the side of the lower
widened portion of the mixing tube, and are more or less closed by means
of an outside loose collar which may be screwed up and down on a thread
on a collar fixed to the mixing tube. The mixing tube is 0.24 inch, and the
burner head 0.475 inch in internal diameter. The opening in the cap of the
burner is 0.16 inch in diameter. There is a diaphragm of double gauze in the
cap, and this is the only gauze used in the burner.

All the incandescent burners hitherto mentioned ordinarily have the gas
nipple made in brass or other metal, which is liable to corrosion, and the
orifice to distortion by heat or if it becomes necessary to remove any
obstruction from it. The orifice in the nipple is extremely small-- usually

Page 327

less than 0.015 inch--and any slight obstruction or distortion would alter to
a serious extent the rate of flow of gas through it, and so affect the working
of the burner. In order to overcome this defect, inherent to metal nipples,
burners are now constructed for acetylene in which the nipple is of hard
incorrodible material. One of these burners has been made on behalf of the
Office Central de l'Acétylène of Paris, and is commonly known as the
"O.C.A." burner. In it the nipple is of steatite. On the inner mixing tube of
this burner is mounted an elongated cone of wire wound spirally, which
serves both to ensure proper admixture of the gas and air, and to prevent
firing-back. There is no gauze in this burner, and the parts are readily
detachable for cleaning when required. Another burner, in which metal is
abolished for the nipple, is made by Geo. Bray and Co., Ltd., of Leeds, and
is shown in Fig. 20. In this burner the injecting nipple is of porcelain.

ACETYLENE FOR HEATING AND COOKING.--Since the problem of
constructing a trustworthy atmospheric burner has been solved, acetylene is
not only available for use in incandescent lighting, but it can also be
employed for heating or cooking purposes, because all boiling, most
warming, and some roasting stoves are simply arrangements for utilising
the heat of a non-luminous flame in one particular way. With suitable
alterations in the dimensions of the burners, apparatus for consuming coal-
gas may be imitated and made fit to burn acetylene; and as a matter of fact

Page 328

several firms are now constructing such appliances, which leave little or
nothing to be desired. It may perhaps be well to insist upon the elementary
point which is so frequently ignored in practice, viz., that no stove, except
perhaps a small portable boiling ring, ought ever to be used in an occupied
room unless it is connected with a chimney, free from down- draughts, for
the products of combustion to escape into the outer air; and also that no
chimney, however tall, can cause an up-draught in all states of the weather
unless there is free admission of fresh air into the room at the base of the
chimney. Still, at the prices for coal, paraffin oil, and calcium carbide which
exist in Great Britain, acetylene is not an economical means of providing
artificial heat. If a 0.7 cubic foot luminous acetylene burner gives a light of
27 candles, and if ordinary country coal-gas gives light of 12 to 13 candles
in a 5-foot burner, one volume of acetylene is equally valuable with 15 or
16 volumes of coal-gas when both are consumed in self-luminous jets; and
if, with the mantle, acetylene develops 99 candles per cubic foot, while
coal-gas gives in common practice 15 to 20 candles, one volume of
acetylene is equally valuable with 5 to 6-1/2 volumes of coal-gas when both
are consumed on the incandescent system; whereas, if the acetylene is burnt
in a flat flame, and the coal-gas under the mantle, 1 volume of the former is
equally efficient with 2 volumes of coal-gas as an artificial illuminant. This
last method of comparison being manifestly unfair, acetylene may be said to
be at least five times as efficient per unit of volume as coal-gas for the
production of light. But from the table given on a later page it appears that
as a source of artificial heat, acetylene is only equal to about 2-3 times its
volume of ordinary coal-gas. Nevertheless, the domestic advantages of gas
firing are very marked; and when a properly constructed stove is properly
installed, the hygienic advantages of gas-firing are alone equally
conspicuous--for the disfavor with which gas-firing is regarded by many
physicians is due to experience gained with apparatus warming principally
by convection [Footnote: Radiant heat is high-temperature heat, like the
heat emitted by a mass of red-hot coke; convected heat is low-temperature
heat, invisible to the eye. Radiant heat heats objects first, and leaves them to
warm the air; convected heat is heat applied directly to air, and leaves the
air to warm objects afterwards. On all hygienic grounds radiant heat is
better than convected heat, but the latter is more economical. By an absurd
and confusing custom, that particular warming apparatus (gas, steam, or hot
water) which yields practically no radiant heat, and does all its work by

Page 329

convection, is known to the trade as a "radiator."] instead of radiation; or to
acquaintance with intrinsically better stoves either not connected to any
flues or connected to one deficient in exhausting power. In these
circumstances, whenever an installation of acetylene has been laid down for
the illumination of a house or district, the merit of convenience may
outweigh the defect of extravagance, and the gas may be judiciously
employed in a boiling ring, or for warming a bedroom; while, if pecuniary
considerations are not paramount, the acetylene may be used for every
purpose to which the townsman would apply his cheaper coal-gas.

The difficulty of constructing atmospheric acetylene burners in which the
flame would not be likely to strike back to the nipple has already been
referred to in connexion with the construction atmospheric burners for
incandescent lighting. Owing, however, to the large proportions of the
atmospheric burners of boiling rings and stove and in particular to the larger
bore of their mixing tube, the risk of the flame striking back is greater with
them, than with incandescent lighting burners. The greatest trouble is
presented at lighting, and when the pressure of the gas-supply is low. The
risk of firing-back when the burner is lighted is avoided in some forms of
boiling rings, &c., by providing a loose collar which can be slipped over the
air inlets of the Bunsen tube before applying a light to the burner, and
slipped clear of them as soon as the burner is alight. Thus at the moment of
lighting, the burner is converted temporarily into one of the non-
atmospheric type, and after the flame has thus been established at the head
or ring of the burner, the internal air-supply is started by removing the loose
collar from the air inlets, and the flame is thus made atmospheric. In these
conditions it does not travel backwards to the nipple. In other heating
burners it is generally necessary to turn on the gas tap a few seconds before
applying a light to the burner or ring or stove; the gas streaming through the
mixing tube then fills it with acetylene and air mixed in the proper working
proportions, and when the light is applied, there is no explosion in the
mixing tube, or striking-back of the flame to the nipple.

Single or two-burner gas rings for boiling purposes, or for heating cooking
ovens, known as the "La Belle," made by Falk Stadelmann and Co., Ltd., of
London, may be used at as low a gas pressure as 2 inches, though they give
better results at 3 inches, which is their normal working pressure. The gas-

Page 330

inlet nozzle or nipple of the burner is set within a spherical bulb in which
are four air inlets. The mixing tube which is placed at a proper distance in
front of the nipple, is proportioned to the rate of flow of the gas and air, and
contains a mixing chamber with a baffling pillar to further their admixture.
A fine wire gauze insertion serves to prevent striking-back of the flame. A
"La Belle" boiling ring consumes at 3 inches pressure about 48 litres or 1.7
cubic feet of acetylene per hour.

ACETYLENE MOTORS.--The question as to the feasibility of developing
"power" from acetylene, i.e., of running an engine by means of the gas, may
be answered in essentially identical terms. Specially designed gas-engines
of 1, 3, 6, or even 10 h.p. work perfectly with acetylene, and such motors
are in regular employment in numerous situations, more particularly for
pumping water to feed the generators of a large village acetylene
installation. Acetylene is not an economical source of power, partly for the
theoretical reason that it is a richer fuel even than coal-gas, and gas-engines
would appear usually to be more efficient as the fuel they burn is poorer in
calorific intensity, i.e., in heating power (which is explosive power) per unit
of volume. The richer, or more concentrated, any fuel in, the more rapidly
does the explosion in a mixture of that fuel with air proceed, because a rich
fuel contains a smaller proportion of non-inflammable gases which tend to
retard explosion than a poor one; and, in reason, a gas-engine works better
the more slowly the mixture of gas and air with which it is fed explodes.
Still, by properly designing the ports of a gas-engine cylinder, so that the
normal amount of compression of the charge and of expansion of the
exploded mixture which best suit coal-gas are modified to suit acetylene,
satisfactory engines can be constructed; and wherever an acetylene
installation for light exists, it becomes a mere question of expediency
whether the same fuel shall not be used to develop power, say, for pumping
up the water required in a large country house, instead of employing hand
labour, or the cheaper hot-air or petroleum motor. Taking the mean of the
results obtained by numerous investigators, it appears that 1 h.p.-hour can
be obtained for a consumption of 200 litres of acetylene; whence it may be
calculated that that amount of energy costs about 3d. for gas only,
neglecting upkeep, lubricating material (which would be relatively
expensive) and interest, &c.

Page 331

Acetylene Blowpipes--The design of a satisfactory blowpipe for use with
acetylene had at first proved a matter of some difficulty, since the jet, like
that of an ordinary self-luminous burner, usually exhibited a tendency to
become choked with carbonaceous growths. But when acetylene had
become available for various purposes at considerable pressure, after
compression into porous matter as described in Chapter XI, the troubles
were soon overcome; and a new form of blowpipe was constructed in which
acetylene was consumed under pressure in conjunction with oxygen. The
temperature given by this apparatus exceeds that of the familiar oxy-
hydrogen blowpipe, because the actual combustible material is carbon
instead of hydrogen. When 2 atoms of hydrogen unite with 1 of oxygen to
form 1 molecule of gaseous water, about 59 large calories are evolved, and
when 1 atom of solid amorphous carbon unites with 2 atoms of oxygen to
form 1 molecule of carbon dioxide, 97.3 calories are evolved. In both cases,
however, the heat attainable is limited by the fact that at certain
temperatures hydrogen and oxygen refuse to combine to form water, and
carbon and oxygen refuse to form carbon dioxide--in other words, water
vapour and carbon dioxide dissociate and absorb heat in the process at
certain moderately elevated temperatures. But when 1 atom of solid
amorphous carbon unites with 1 atom of oxygen to form carbon monoxide,
29.1 [Footnote: Cf. Chapter VI., page 185.] large calories are produced, and
carbon monoxide is capable of existence at much higher temperatures than
either carbon dioxide or water vapour. In any gaseous hydrocarbon, again,
the carbon exists in the gaseous state, and when 1 atom of the hypothetical
gaseous carbon combines with 1 atom of oxygen to produce 1 molecule of
carbon monoxide, 68.2 large calories are evolved. Thus while solid
amorphous carbon emits more heat than a chemically equivalent quantity of
hydrogen provided it is enabled to combine with its higher proportion of
oxygen, it emits less if only carbon monoxide is formed; but a higher
temperature can be attained in the latter case, because the carbon monoxide
is more permanent or stable. Gaseous carbon, on the other hand, emits more
heat than an equivalent quantity of hydrogen, [Footnote: In a blowpipe
flame hydrogen can only burn to gaseous, not liquid, water.] even when it is
only converted into the monoxide. In other words, a gaseous fuel which
consists of hydrogen alone can only yield that temperature as a maximum at
which the speed of the dissociation of the water vapour reaches that of the
oxidation of the hydrogen; and were carbon dioxide the only oxide of

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carbon, a similar state of affairs would be ultimately reached in the flame of
a carbonaceous gas. But since in the latter case the carbon dioxide does not
tend to dissociate completely, but only to lose one atom of oxygen, above
the limiting temperature for the formation of carbon dioxide, carbon
monoxide is still produced, because there is less dissociating force opposed
to its formation. Thus at ordinary temperatures the heat of combustion of
acetylene is 315.7 calories; but at temperatures where water vapour and
carbon dioxide no longer exist, there is lost to that quantity of 315.7 calories
the heat of combustion of hydrogen (69.0) and twice that of carbon
monoxide (68.2 x 2 = 136.4); so that above those critical temperatures, the
heat of combustion of acetylene is only 315.7 - (69.0 + 136.4) = 110.3.
[Footnote: When the heat of combustion of acetylene is quoted as 315.7
calories, it is understood that the water formed is condensed into the liquid
state. If the water remains gaseous, as it must do in a flame, the heat of
formation is reduced by about 10 calories. This does not affect the above
calculation, because the heat of combustion of hydrogen when the water
remains gaseous is similarly 10 calories less than 69, i.e., 59, as mentioned
above in the text. Deleting the heat of liquefaction of water, the calculation
referred to becomes 305.7 - (59.0 + l36.4) = 110.3 as before.] This value of
110.3 calories is clearly made up of the heat of formation of acetylene itself,
and twice the heat of conversion of carbon into carbon monoxide, i.e., for
diamond carbon, 58.1 + 26.1 x 2 = 110.3; or for amorphous carbon, 52.1 +
29.1 x 2 = 110.3. From the foregoing considerations, it may be inferred that
the acetylene-oxygen blowpipe can be regarded as a device for burning
gaseous carbon in oxygen; but were it possible to obtain carbon in the state
of gas and so to lead it into a blowpipe, the acetylene apparatus should still
be more powerful, because in it the temperature would be raised, not only
by the heat of formation of carbon monoxide, but also by the heat attendant
upon the dissociation of the acetylene which yields the carbon.

Acetylene requires 2.5 volumes of oxygen to burn it completely; but in the
construction of an acetylene-oxygen blowpipe the proportion of oxygen is
kept below this figure, viz., at 1.1 to 1.8 volumes, so that the deficiency is
left to be made up from the surrounding air. Thus at the jet of the blowpipe
the acetylene dissociates and its carbon is oxidised, at first no doubt to
carbon monoxide only, but afterwards to carbon dioxide; and round the
flame of the gaseous carbon is a comparatively cool, though absolutely very

Page 333

hot jacket of hydrogen burning to water vapour in a mixture of oxygen and
air, which protects the inner zone from loss of heat. As just explained,
theoretical grounds support the conclusions at which Fouché has arrived,
viz., that the temperature of the acetylene-oxygen blowpipe flame is above
that at which hydrogen will combine with oxygen to form water, and that it
can only be exceeded by those found in a powerful electric furnace. As the
hydrogen dissociated from the acetylene remains temporarily in the free
state, the flame of the acetylene blowpipe, possesses strong reducing
powers; and this, coupled probably with an intensity of heat which is
practically otherwise unattainable, except by the aid of a high-tension
electric current, should make the acetylene-oxygen blowpipe a most useful
piece of apparatus for a large variety of metallurgical, chemical, and
physical operations. In Fouché's earliest attempts to design an acetylene
blowpipe, the gas was first saturated with a combustible vapour, such as
that of petroleum spirit or ether, and the mixture was consumed with a blast
of oxygen in an ordinary coal-gas blow-pipe. The apparatus worked fairly
well, but gave a flame of varying character; it was capable of fusing iron,
raised a pencil of lime to a more brilliant degree of incandescence than the
eth-oxygen burner, and did not deposit carbon at the jet. The matter,
however, was not pursued, as the blowpipe fed with undiluted acetylene
took its place. The second apparatus constructed by Fouché was the high-
pressure blowpipe, the theoretical aspect of which has already been studied.
In this, acetylene passing through a water-seal from a cylinder where it is
stored as a solution in acetone (cf. Chapter XI.), and oxygen coming from
another cylinder, are each allowed to enter the blowpipe at a pressure of 118
to 157 inches of water column (i.e., 8.7 to 11.6 inches of mercury; 4.2 to 5.7
lb. per square inch, or 0.3 to 0.4 atmosphere). The gases mix in a chamber
tightly packed with porous matter such as that which is employed in the
original acetylene reservoir, and finally issue from a jet having a diameter
of 1 millimetre at the necessary speed of 100 to 150 metres per second.
Finding, however, that the need for having the acetylene under pressure
somewhat limited the sphere of usefulness of his apparatus, Fouché finally
designed a low-pressure blowpipe, in which only the oxygen requires to be
in a state of compression, while the acetylene is drawn directly from any
generator of the ordinary pattern that does not yield a gas contaminated
with air. The oxygen passes through a reducing valve to lower the pressure
under which it stands in the cylinder to that of 1 or 1.5 effective

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atmosphere, this amount being necessary to inject the acetylene and to give
the previously mentioned speed of escape from the blowpipe orifice. The
acetylene is led through a system of long narrow tubes to prevent it firing-
back.

AUTOGENOUS SOLDERING AND WELDING.--The blowpipe is
suitable for the welding and for the autogenous soldering or "burning" of
wrought or cast iron, steel, or copper. An apparatus consuming from 600 to
1000 litres of acetylene per hour yields a flame whose inner zone is 10 to 15
millimetres long, and 3 to 4 millimetres in diameter; it is sufficiently
powerful to burn iron sheets 8 to 9 millimetres thick. By increasing the
supply of acetylene in proportion to that of the oxygen, the tip of the inner
zone becomes strongly luminous, and the flame then tends to carburise iron;
when the gases are so adjusted that this tip just disappears, the flame is at its
best for heating iron and steel. The consumption of acetylene is about 75
litres per hour for each millimetre of thickness in the sheet treated, and the
normal consumption of oxygen is 1.7 times as much; a joint 6 metres long
can be burnt in 1 millimetre plate per hour, and one of 1.5 metres in 10
millimetre plate. In certain cases it is found economical to raise the metal to
dull redness by other means, say with a portable forge of the usual
description, or with a blowpipe consuming coal-gas and air. There are other
forms of low- pressure blowpipe besides the Fouché, in some of which the
oxygen also is supplied at low pressure. Apart from the use of cylinders of
dissolved acetylene, which are extremely convenient and practically
indispensable when the blowpipe has to be applied in confined spaces (as in
repairing propeller shafts on ships in situ), acetylene generators are now
made by several firms in a convenient transportable form for providing the
gas for use in welding or autogenous soldering. It is generally supposed that
the metal used as solder in soldering iron or steel by this method must be
iron containing only a trifling proportion of carbon (such as Swedish iron),
because the carbon of the acetylene carburises the metal, which is heated in
the oxy-acetylene flame, and would thereby make ordinary steel too rich in
carbon. But the extent to which the metal used is carburised in the flame
depends, as has already been indicated, on the proper adjustment of the
proportion of oxygen to acetylene. Oxy-acetylene autogenous soldering or
welding is applicable to a great variety of work, among which may be
mentioned repairs to shafts, locomotive frames, cylinders, and to joints in

Page 335

ships' frames, pipes, boilers, and rails. The use of the process is rapidly
extending in engineering works generally. Generators for acetylene
soldering or welding must be of ample size to meet the quickly fluctuating
demands on them and must be provided with water-seals, and a washer or
scrubber and filter capable of arresting all impurities held mechanically in
the crude gas, and with a safety vent- pipe terminating in the open at a
distance from the work in hand. The generator must be of a type which
affords as little after-generation as possible, and should not need recharging
while the blowpipe is in use. There should be a main tap on the pipe
between the generator and the blowpipe. It does not appear conclusively
established that the gas consumed should have been chemically purified,
but a purifier of ample size and charged with efficient material is
undoubtedly beneficial. The blowpipe must be designed so that it remains
sufficiently cool to prevent polymerisation of the acetylene and deposition
of the resultant particles of carbon or soot within it.

It is important to remember that if a diluent gas, such as nitrogen, is present,
the superior calorific power of acetylene over nearly all gases should avail
to keep the temperature of the flame more nearly up to the temperature at
which hydrogen and oxygen cease to combine. Hence a blowpipe fed with
air and acetylene would give a higher temperature than any ordinary
(atmospheric) coal-gas blowpipe, just as, as has been explained in Chapter
VI., an ordinary acetylene flame has a higher temperature than a coal-gas
flame. It is likely that a blowpipe fed with "Lindé-air" (oxygen diluted with
less nitrogen than in the atmosphere) and acetylene would give as high a
limelight effect as the oxy-hydrogen or oxy-coal-gas blowpipe.

Page 336

CHAPTER X
CARBURETTED ACETYLENE

Now that atmospheric or Bunsen burners for the consumption of acetylene
for use in lighting by the incandescent system and in heating have been so
much improved that they seem to be within measurable reach of a state of
perfection, there appears to be but little use at the present time for a
modified or diluted acetylene which formerly seemed likely to be valuable
for heating and certain other purposes. Nevertheless, the facts relating to
this so-called carburetted acetylene are in no way traversed by its failure to
establish itself as an active competitor with simple acetylene for heating
purposes, and since it is conceivable that the advantages which from the
theoretical standpoint the carburetted gas undoubtedly possesses in certain
directions may ultimately lead to its practical utilisation for special
purposes, it has been deemed expedient to continue to give in this work an
account of the principles underlying the production and application of
carburetted acetylene.

It has already been explained that acetylene is comparatively a less efficient
heating agent than it is an illuminating material, because, per unit of
volume, its calorific power is not so much greater than that of coal-gas as is
its illuminating capacity. It has also been shown that the high upper
explosive limit of mixtures of acetylene and air--a limit so much higher than
the corresponding figure with coal-gas and other gaseous fuels--renders its
employment in atmospheric burners (either for lighting or for heating)
somewhat troublesome, or dependent upon considerable skill in the design
of the apparatus. If, therefore, either the upper explosive limit of acetylene
could be reduced, or its calorific value increased (or both), by mixing with
it some other gas or vapour which should not seriously affect its price and
convenience as a self-luminous illuminant, acetylene would compare more
favourably with coal-gas in its ready applicability to the most various
purposes. Such a method has been suggested by Heil, and has been found
successful on the Continent. It consists in adding to the acetylene a certain

Page 337

proportion of the vapour of a volatile hydrocarbon, so as to prepare what is
called "carburetted acetylene." In all respects the method of making
carburetted acetylene is identical with that of making "air-gas," which was
outlined in Chapter I., viz., the acetylene coming from an ordinary
generating plant is led over or through a mass of petroleum spirit, or other
similar product, in a vessel which exposes the proper amount of superficial
area to the passing gas. In all respects save one the character of the product
is similar to that of air-gas, i.e., it is a mixture of a permanent gas with a
vapour; the vapour may possibly condense in part within the mains if they
are exposed to a falling temperature, and if the product is to be led any
considerable distance, deposition of liquid may occur (conceivably
followed by blockage of the mains) unless the proportion of vapour added
to the gas is kept below a point governed by local climatic and similar
conditions. But in one most important respect carburetted acetylene is
totally different from air-gas: partial precipitation of spirit from air-gas
removes more or less of the solitary useful constituent of the material,
reducing its practical value, and causing the residue to approach or overpass
its lower explosive limit (cf. Chapter I.); partial removal of spirit from
carburetted acetylene only means a partial reconversion of the material into
ordinary acetylene, increasing its natural illuminating power, lowering its
calorific intensity somewhat, and causing the residue to have almost its
primary high upper explosive limit, but essentially leaving its lower
explosive limit unchanged. Thus while air-gas may conceivably become
inefficient for every purpose if supplied from any distance in very cold
weather, and may even pass into a dangerous explosive within the mains;
carburetted acetylene can never become explosive, can only lose part of its
special heating value, and will actually increase in illuminating power.

It is manifest that, like air-gas, carburetted acetylene is of somewhat
indefinite composition, for the proportion of vapour, and the chemical
nature of that vapour, may vary. 100 litres of acetylene will take up 40
grammes of petroleum spirit to yield 110 litres of carburetted acetylene
evidently containing 9 per cent. of vapour, or 100 litres of acetylene may be
made to absorb as much as 250 grammes of spirit yielding 200 litres of
carburetted acetylene containing 50 per cent. of vapour; while the
petroleum spirit may be replaced, if prices are suitable, by benzol or
denatured alcohol.

Page 338

The illuminating power of acetylene carburetted with petroleum spirit has
been examined by Caro, whose average figures, worked out in British units,
are:

ILLUMINATING POWER OF CARBURETTED ACETYLENE. HALF-
FOOT BURNERS.

Self-luminous. | Incandescent
1 litre = 1.00 candle. | 1 litre = 3.04
candles.
1 cubic foot = 28.4 candles. | 1 cubic foot = 86.2
candles.
1 candle = 1.00 litre. | 1 candle = 0.33
litre.
1 candle = 0.035 cubic foot. | 1 candle = 0.012
cubic foot.

Those results may be compared with those referring to air-gas, which emits
in incandescent burners from 3.0 to 12.4 candles per cubic foot according to
the amount of spirit added to the air and the temperature to which the gas is
exposed.

The calorific values of carburetted acetylene (Caro), and those of other
gaseous fuels are:

Large
Calories per
_ Cubic
Foot.
| (Lewes) . 320
| (Gand) . 403
Ordinary acetylene . . | (Heil) . 365
| ___
|_Mean . .
363

| Maximum . 680
Carburetted acetylene . . | Minimum . 467
(petroleum spirit) | ___
|_Mean . .
573

Page 339

Carburetted acetylene (50 per cent. benzol by volume)
685
Carburetted acetylene (50 per cent. alcohol by volume)
364
Coal-gas (common, unenriched) . . . . .
150
_
| Maximum . 178
Air-gas, self-luminous flame | Minimum . 57
| ___
|_Mean . . .
114
_
| Maximum . 26
Air-gas, non-luminous flame | Minimum . 18
| ___
|_Mean . . .
22

Water-gas (Strache) from coke . . . . .
71
Mond gas (from bituminous coal) . . . . .
38
Semi-water-gas from coke or anthracite . . .
36
Generator (producer) gas . . . . . .
29

Besides its relatively low upper explosive limit, carburetted acetylene
exhibits a higher temperature of ignition than ordinary acetylene, which
makes it appreciably safer in presence of a naked light. It also possesses a
somewhat lower flame temperature and a slower speed of propagation of
the explosive wave when mixed with air. These data are:

_______________________________________________________________
_______
| | | |
|
| | Explosive | Temperature. |
|
| | Limits. | Degrees C. |

Page 340

Explosive |
| |19 mm. Tube. | |
Explosive |
| |_____________|__________________|
Wave. |
| | | | | |
Metres per |
| | | |Of Igni-| |
Second. |
| |Lower.|Upper.| tion. |Of Flame.|
|
|________________________|______|______|________|_________|____
________|
| | | | | |
|
| Acetylene (theoretical)| --- | --- | --- |1850-2420|
--- |
| " (observed) | 3.35 | 52.3 | 480 |1630-2020|
0.18-100 |
| Carburetted \ from | 2.5 | 10.2 | 582 | 1620 |
3.2 |
| acetylene / . . to | 5.4 | 30.0 | 720 | 1730 |
5.3 |
| Carburetted acetylene\ | 3.4 | 22.0 | --- | 1820 |
1.3 |
| (benzol) . . . / | | | | |
|
| Carburetted acetylene\ | 3.1 | 12.0 | --- | 1610 |
1.1 |
| (alcohol) . . . / | | | | |
|
| Air-gas, self-luminous\|15.0 | 50.0 | --- |1510-1520|
--- |
| flame . . . . /| | | | |
|
| Coal-gas . . . | 7.9 | 19.1 | 600 | --- |
--- |
|________________________|______|______|________|_________|____
________|

In making carburetted acetylene, the pressure given by the ordinary
acetylene generator will be sufficient to drive the gas through the
carburettor, and therefore there will be no expense involved beyond the cost
of the spirit vaporised. Thus comparisons may fairly be made between
ordinary and carburetted acetylene on the basis of material only, the
expense of generating the original acetylene being also ignored. In Great

Page 341

Britain the prices of calcium carbide, petroleum spirit, and 90s benzol
delivered in bulk in country places may be taken at 15£ per ton, and 1s. per
gallon respectively, petroleum spirit having a specific gravity of 0.700 and
benzol of 0.88. On this basis, a unit volume (100 cubic metres) of plain
acetylene costs 1135d., of "petrolised" acetylene containing 66 per cent. of
acetylene costs 1277d., and of "benzolised" acetylene costs 1180d. In other
words, 100 volumes of plain acetylene, 90 volumes of petrolised acetylene,
and 96 volumes of benzolised acetylene are of equal pecuniary value.
Employing the data given in previous tables, it appears that 38.5 candles
can be won from plain acetylene in a self-luminous burner, and 103 candles
therefrom in an incandescent burner at the same price as 25.5-29.1 and 78-
87 candles can be obtained from carburetted acetylene; whence it follows
that at English prices petrolised acetylene is more expensive as an
illuminant in either system of combustion than the simple gas, while
benzolised acetylene, burnt under the mantle only, is more nearly equal to
the simple gas from a pecuniary aspect. But considering the calorific value,
it appears that for a given sum of money only 363 calories can be obtained
from plain acetylene, while petrolised acetylene yields 516, and benzolised
acetylene 658; so that for all heating or cooking purposes (and also for
driving small motors) carburetted acetylene exhibits a notable economy.
Inasmuch as the partial saturation of acetylene with any combustible vapour
is an operation of extreme simplicity, requiring no power or supervision
beyond the occasional recharging of the carburettor, it is manifest that the
original main coming from the generator supplying any large establishment
where much warming, cooking (or motor driving) might conveniently be
done with the gas could be divided within the plant-house, one branch
supplying all, or nearly all, the lighting burners with plain acetylene, and
the other branch communicating with a carburettor, so that all, or nearly all,
the warming and cooking stoves (and the motor) should be supplied with
the more economical carburetted acetylene. Since any water pump or
similar apparatus would be in an outhouse or basement, and the most
important heating stove (the cooker) be in the kitchen, such an arrangement
would be neither complicated nor involve a costly duplication of pipes.

It follows from the fact that even a trifling proportion of vapour reduces the
upper limit of explosibility of mixtures of acetylene with air, that the gas
may be so lightly carburetted as not appreciably to suffer in illuminating

Page 342

power when consumed in self-luminous jets, and yet to burn satisfactorily
in incandescent burners, even if it has been generated in an apparatus which
introduces some air every time the operation of recharging is performed. To
carry out this idea, Caro has suggested that 5 kilos. of petroleum spirit
should be added to the generator water for every 50 cubic metres of gas
evolved, i.e., 1 lb. per 160 cubic feet, or, say, 1 gallon per 1000 cubic feet,
or per 200 lb. of carbide decomposed. Caro proposed this addition in the
case of central installations supplying a district where the majority of the
consumers burnt the gas in self-luminous jets, but where a few preferred the
incandescent system; but it is clearly equally suitable for employment in all
private plants of sufficient magnitude.

A lowering of the upper limit of explosibility is also produced by the
presence of the acetone which remains in acetylene when obtained from a
cylinder holding the compressed gas (cf. Chapter XI.). According to Wolff
and Caro such gas usually carries with it from 30 to 60 grammes of acetone
vapour per cubic metre, i.e., 1.27 grammes per cubic foot on an average;
and this amount reduces the upper limit of explosibility by about 16 per
cent., so that to this extent the gas behaves more smoothly in an
incandescent burner of imperfect design.

Lépinay has described some experiments on the comparative technical
value of ordinary acetylene, carburetted acetylene, denatured alcohol and
petroleum spirit as fuels for small explosion engines. One particular motor
of 3 (French) h.p. consumed 1150 grammes of petroleum spirit per hour at
full load; but when it was supplied with carburetted acetylene its
consumption fell to 150 litres of acetylene and 700 grammes of spirit
(specific gravity 0.680). A 1-1/4 h.p. engine running light required 48
grammes of 90 per cent. alcohol per horse-power-hour and 66 litres of
acetylene; at full load it took 220 grammes of alcohol and 110 litres of
acetylene. A 6 h.p. engine at full load required 62 litres of acetylene
carburetted with 197 grammes of petroleum spirit per horse-power-hour
(uncorrected); while a similar motor fed with low-grade Taylor fuel-gas
took 1260 litres per horse-power-hour, but on an average developed the
same amount of power from 73 litres when 10 per cent. of acetylene was
added to the gas. Lépinay found that with pure acetylene ignition of the
charge was apt to be premature; and that while the consumption of

Page 343

carburetted acetylene in small motors still materially exceeded the
theoretical, further economics could be attained, which, coupled with the
smooth and regular running of an engine fed with the carburetted gas, made
carburetted acetylene distinctly the better power-gas of the two.

Page 344

CHAPTER XI
COMPRESSED AND DISSOLVED ACETYLENE--
MIXTURES WITH OTHER GASES

In all that was said in Chapters II., III., IV., and V. respecting the generation
and employment of acetylene, it was assumed that the gas would be
produced by the interaction of calcium carbide and water, either by the
consumer himself, or in some central station delivering the acetylene
throughout a neighbourhood in mains. But there are other methods of using
the gas, which have now to be considered.

COMPRESSED ACETYLENE.--In the first place, like all other gases,
acetylene is capable of compression, or even of conversion into the liquid
state; for as a gas, the volume occupied by any given weight of it is not
fixed, but varies inversely with the pressure under which it is stored. A steel
cylinder, for instance, which is of such size as to hold a cubic foot of water,
also holds a cubic foot of acetylene at atmospheric pressure, but holds 2
cubic feet if the gas is pumped into it to a pressure of 2 atmospheres, or 30
lb. per square inch; while by increasing the pressure to 21.53 atmospheres
at 0° C. (Ansdell, Willson and Suckert) the gas is liquefied, and the vessel
may then contain 1 cubic foot of liquid acetylene, which is equal to some
400 cubic feet of gaseous acetylene at normal pressure. It is clear that for
many purposes acetylene so compressed or liquefied would be convenient,
for if the cylinders could be procured ready charged, all troubles incidental
to generation would be avoided. The method, however, is not practically
permissible; because, as pointed out in Chapters II. and VI., acetylene does
not safely bear compression to a point exceeding 2 atmospheres; and the
liability to spontaneous dissociation or explosion in presence of spark or
severe blow, which is characteristic of compressed gaseous acetylene, is
greatly enhanced if compression has been pushed to the point of
liquefaction.

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However, two methods of retaining the portability and convenience of
compressed acetylene with complete safety have been discovered. In one,
due to the researches of Claude and Hess, the gas is pumped under pressure
into acetone, a combustible organic liquid of high solvent power, which
boils at 56° C. As the solvent capacity of most liquids for most gases rises
with the pressure, a bottle partly filled with acetone may be charged with
acetylene at considerable effective pressure until the vessel contains much
more than its normal quantity of gas; and when the valve is opened the
surplus escapes, ready for employment, leaving the acetone practically
unaltered in composition or quantity, and fit to receive a fresh charge of gas.
In comparison with liquefied acetylene, its solution in acetone under
pressure is much safer; but since the acetone expands during absorption of
gas, the bottle cannot be entirely filled with liquid, and therefore either at
first, or during consumption (or both), above the level of the relatively safe
solution, the cylinder contains a certain quantity of gaseous acetylene,
which is compressed above its limit of safety. The other method consists in
pumping acetylene under pressure into a cylinder apparently quite full of
some highly porous solid matter, like charcoal, kieselguhr, unglazed brick,
&c. This has the practical result that the gas is held under a high state of
compression, or possibly as a liquid, in the minute crevices of the material,
which are almost of insensible magnitude; or it may be regarded as stored in
vessels whose diameter is less than that in which an explosive wave can be
propagated (cf. Chapter VI.).

DISSOLVED ACETYLENE.--According to Fouché, the simple solution of
acetylene in acetone has the same coefficient of expansion by heat as that of
pure acetone, viz., 0.0015; the corresponding coefficient of liquefied
acetylene is 0.007 (Fouché), or 0.00489 (Ansdell) i.e., three or five times as
much. The specific gravity of liquid acetylene is 0.420 at 16.4° C.
(Ansdell), or 0.528 at 20.6° C. (Willson and Suckert); while the density of
acetylene dissolved in acetone is 0.71 at 15° C. (Claude). The tension of
liquefied acetylene is 21.53 atmospheres at 0° C., and 39.76 atmospheres at
20.15° C. (Ansdell); 21.53 at 0° C., and 39.76 at 19.5° C. (Willson and
Suckert); or 26.5 at 0° C., and 42.8 at 20.0° C. (Villard). Averaging those
results, it may be said that the tension rises from 23.2 atmospheres at 0° C.
to 40.77 at 20° C., which is an increment of 1/26 or 0.88 atmosphere, per 1°
Centigrade; while, of course, liquefied acetylene cannot be kept at all at a

Page 346

temperature of 0° unless the pressure is 21 atmospheres or upwards. The
solution of acetylene in acetone can be stored at any pressure above or
below that of the atmosphere, and the extent to which the pressure will rise
as the temperature increases depends on the original pressure. Berthelot and
Vieille have shown that when (a) 301 grammes of acetone are charged with
69 grammes of acetylene, a pressure of 6.74 atmospheres at 14.0° C. rises to
10.55 atmospheres at 35.7° C.; (b) 315 grammes of acetone are charged
with 118 grammes of acetylene, a pressure of 12.25 atmospheres at 14.0° C.
rises to 19.46 at 36.0° C.; (c) 315 grammes of acetone are charged with 203
grammes of acetylene, a pressure of 19.98 atmospheres at 13.0° C. rises to
30.49 at 36.0° C. Therefore in (a) the increase in pressure is 0.18
atmosphere, in (b) O.33 atmosphere, and in (c) 0.46 atmosphere per 1°
Centigrade within the temperature limits quoted. Taking case (b) as the
normal, it follows that the increment in pressure per 1° C. is 1/37 (usually
quoted as 1/30); so that, measured as a proportion of the existing pressure,
the pressure in a closed vessel containing a solution of acetylene in acetone
increases nearly as much (though distinctly less) for a given rise in
temperature as does the pressure in a similar vessel filled with liquefied
acetylene, but the absolute increase is roughly only one-third with the
solution as with the liquid, because the initial pressure under which the
solution is stored is only one-half, or less, that at which the liquefied gas
must exist.

Supposing, now, that acetylene contained in a closed vessel, either as
compressed gas, as a solution in acetone, or as a liquid, were brought to
explosion by spark or shock, the effects capable of production have to be
considered. Berthelot and Vieille have shown that if gaseous acetylene is
stored at a pressure of 11.23 kilogrammes per square centimetre, [Footnote:
1 kilo. per sq. cm. is almost identical with 1 atmosphere, or 15 lb. per sq.
inch.] the pressure after explosion reaches 92.33 atmospheres on an
average, which is an increase of 8.37 times the original figure; if the gas is
stored at 21.13 atmospheres, the mean pressure after explosion is 213.15
atmospheres, or 10.13 times the original amount. If liquid acetylene is
tested similarly, the original pressure, which must clearly be more than
21.53 atmospheres (Ansdell) at 0° C., may rise to 5564 kilos, per square
centimetre, as Berthelot and Vieille observed when a steel bomb having a
capacity of 49 c.c. was charged with 18 grammes of liquefied acetylene. In

Page 347

the case of the solution in acetone, the magnitudes of the pressures set up
are of two entirely different orders according as the original pressure 20
atmospheres or somewhat less; but apart from this, they vary considerably
with the extent to which the vessel is filled with the liquid, and they also
depend on whether the explosion is produced in the solution or in the gas
space above. Taking the lower original pressure first, viz., 10 atmospheres,
when a vessel was filled with solution to 33 per cent. of its capacity, the
pressure after explosion reached about 95 atmospheres if the spark was
applied to the gas space; but attained 117.4 atmospheres when the spark
was applied to the acetone. When the vessel was filled 56 per cent. full, the
pressures after explosion reached about 89, or 155 atmospheres, according
as the gas or the liquid was treated with the spark. But when the original
pressure was 20 atmospheres, and the vessel was filled to 35 per cent. of its
actual capacity with solution, the final pressures ranged from 303 to 568
atmospheres when the gas was fired, and from 2000 to 5100 when the spark
was applied to the acetone. Examining these figures carefully, it will be
seen that the phenomena accompanying the explosion of a solution of
acetylene in acetone resemble those of the explosion of compressed gaseous
acetylene when the original pressure under which the solution is stored is
about 10 atmospheres; but resemble those of the explosion of liquefied
acetylene when the original pressure of the solution reaches 20
atmospheres, this being due to the fact that at an original pressure of 10
atmospheres the acetone itself does not explode, but, being exothermic,
rather tends to decrease the severity of the explosion; whereas at an original
pressure of 20 atmospheres the acetone does explode (or burn), and adds its
heat of combustion to the heat evolved by the acetylene. Thus at 10
atmospheres the presence of the acetone is a source of safety; but at 20
atmospheres it becomes an extra danger.

Since sound steel cylinders may easily be constructed to boar a pressure of
250 atmospheres, but would be burst by a pressure considerably less than
5000 atmospheres, it appears that liquefied acetylene and its solution in
acetone at a pressure of 20 atmospheres are quite unsafe; and it might also
seem that both the solution at a pressure of 10 atmospheres and the simple
gas compressed to the same limit should be safe. But there is an important
difference here, in degree if not in kind, because, given a cylinder of known
capacity containing (1) gaseous acetylene compressed to 10 atmospheres, or

Page 348

(2) containing the solution at the same pressure, if an explosion were to
occur, in case (1) the whole contents would participate in the
decomposition, whereas in case (2), as mentioned already, only the small
quantity of gaseous acetylene above the solution would be dissociated.

It is manifest that of the three varieties of compressed acetylene now under
consideration, the solution in acetone is the only one fit for general
employment; but it exhibits the grave defects (a) that the pressure under
which it is prepared must be so small that the pressure in the cylinders can
never approach 20 atmospheres in the hottest weather or in the hottest
situation to which they may be exposed, (b) that the gas does not escape
smoothly enough to be convenient from large vessels unless those vessels
are agitated, and (c) that the cylinders must always be used in a certain
position with the valve at the top, lest part of the liquid should run out into
the pipes. For these reasons the simple solution of acetylene in acetone has
not become of industrial importance; but the processes of absorbing either
the gas, or better still its solution in acetone, in porous matter have already
achieved considerable success. Both methods have proved perfectly safe
and trustworthy; but the combination of the acetone process with the porous
matter makes the cylinders smaller per unit volume of acetylene they
contain. Several varieties of solid matter appear to work satisfactorily, the
only essential feature in their composition being that they shall possess a
proper amount of porosity and be perfectly free from action upon the
acetylene or the acetone (if present). Lime does attack acetone in time, and
therefore it is not a suitable ingredient of the solid substance whenever
acetylene is to be compressed in conjunction with the solvent; so that at
present either a light brick earth which has a specific gravity of 0.5 is
employed, or a mixture of charcoal with certain inorganic salts which has a
density of 0.3, and can be introduced through a small aperture into the
cylinder in a semi-fluid condition. Both materials possess a porosity of 80
per cent., that is to say, when a cylinder is apparently filled quite full, only
20 per cent, of the space is really occupied by the solid body, the remaining
80 per cent, being available for holding the liquid or the compressed gas. If
all comparisons as to degree of explosibility and effects of explosion are
omitted, an analogy may be drawn between liquefied acetylene or its
compressed solution in acetone and nitroglycerin, while the gas or solution
of the gas absorbed in porous matter resembles dynamite. Nitroglycerin is

Page 349

almost too treacherous a material to handle, but as an explosive (which in
reason absorbed or dissolved acetylene is not) dynamite is safe, and even
requires special arrangements to explode it.

In Paris, where the acetone process first found employment on a large scale,
the company supplying portable cylinders to consumers uses large storage
vessels filled, as above mentioned, apparently full of porous solid matter,
and also charged to about 43 per cent, of their capacity with acetone, thus
leaving about 37 per cent. of the apace for the expansion which occurs as
the liquid takes up the gas. Acetylene is generated, purified, and thoroughly
dried according to the usual methods; and it is then run through a double-
action pump which compresses it first to a pressure of 3.5 kilos., next to a
pressure of 3.5 x 3.5 = 12 kilos, per square centimetre, and finally drives it
into the storage vessels. Compression is effected in two stages, because the
process is accompanied by an evolution of much heat, which might cause
the gas to explode during the operation; but since the pump is fitted with
two cylinders, the acetylene can be cooled after the first compression. The
storage vessels then contain 100 times their apparent volume of acetylene;
for as the solubility of acetylene in acetone at ordinary temperature and
pressure is about 25 volumes of gas in 1 of liquid, a vessel holding 100
volumes when empty takes up 25 x 43 = 1000 volumes of acetylene roughly
at atmospheric pressure; which, as the pressure is approximately 10
atmospheres, becomes 1000 x 10 = 10,000 volumes per 100 normal
capacity, or 100 times the capacity of the vessel in terms of water. From
these large vessels, portable cylinders of various useful dimensions,
similarly loaded with porous matter and acetone, are charged simply by
placing them in mutual contact, thus allowing the pressure and the surplus
gas to enter the small one; a process which has the advantage of renewing
the small quantity of acetone vaporised from the consumers' cylinders as the
acetylene is burnt (for acetone is somewhat volatile, cf. Chapter X.), so that
only the storage vessels ever need to have fresh solvent introduced.

Where it is procurable, the use of acetylene compressed in this fashion is
simplicity itself; for the cylinders have only to be connected with the house
service-pipes through a reducing valve of ordinary construction, set to give
the pressure which the burners require. When exhausted, the bottle is
simply replaced by another. Manifestly, however, the cost of compression,

Page 350

the interest on the value of the cylinders, and the carriage, &c., make the
compressed gas more expensive per unit of volume (or light) than acetylene
locally generated from carbide and water; and indeed the value of the
process does not lie so much in the direction of domestic illumination as in
that of the lighting, and possibly driving, of vehicles and motor-cars--more
especially in the illumination of such vehicles as travel constantly, or for
business purposes, over rough road surfaces and perform mostly out-and-
home journeys. Nevertheless, absorbed acetylene may claim close attention
for one department of household illumination, viz., the portable table-lamp;
for the base of such an apparatus might easily be constructed to imitate the
acetone cylinder, and it could be charged by simple connexion with a larger
one at intervals. In this way the size of the lamp for a given number of
candle-hours would be reduced below that of any type of actual generator,
and the troubles of after-generation, always more or less experienced in
holderless generators, would be entirely done away with. Dissolved
acetylene is also very useful for acetylene welding or autogenous soldering.

The advantages of compressed and absorbed acetylene depend on the small
bulk and weight of the apparatus per unit of light, on the fact that no
amount of agitation can affect the evolution of gas (as may happen with an
ordinary acetylene generator), on the absence of any liquid which may
freeze in winter, and on there being no need for skilled attention except
when the cylinders are being changed. These vessels weigh between 2.5 and
3 kilos, per 1 litre capacity (normal) and since they are charged with 100
times their apparent volume of acetylene, they may be said to weigh 1 kilo,
per 33 litres of available acetylene, or roughly 2 lb. per cubic foot, or, again,
if half-foot burners are used, 2 lb. per 36 candle- hours. According to
Fouché, if electricity obtained from lead accumulators is compared with
acetylene on the basis of the weight of apparatus needed to evolve a certain
quantify of light, 1 kilo, of acetylene cylinder is equal to 1.33 kilos, of lead
accumulator with arc lamps, or to 4 kilos. of accumulator with glow lamps;
and moreover the acetylene cylinder can be charged and discharged,
broadly speaking, as quickly or as slowly as may be desired; while, it may
be added, the same cylinder will serve one or more self-luminous jets, one
or more incandescent burners, any number and variety of heating apparatus,
simultaneously or consecutively, at any pressure which may be required.
From the aspect of space occupied, dissolved acetylene is not so

Page 351

concentrated a source of artificial light as calcium carbide; for 1 volume of
granulated carbide is capable of omitting as much light as 4 volumes of
compressed gas; although, in practice, to the 1 volume of carbide must be
added that of the apparatus in which it is decomposed.

LIQUEFIED ACETYLENE.--In most civilised countries the importation,
manufacture, storage, and use of liquefied acetylene, or of the gas
compressed to more than a fraction of one effective atmosphere, is quite
properly prohibited by law. In Great Britain this has been done by an Order
in Council dated November 26, 1897, which specifies 100 inches of water
column as the maximum to which compression may be pushed. Power
being retained, however, to exempt from the order any method of
compressing acetylene that might be proved safe, the Home Secretary
issued a subsequent Order on March 28, 1898, permitting oil-gas containing
not more than 20 per cent, by volume of acetylene (see below) to be
compressed to a degree not exceeding 150 lb. per square inch, i.e., to about
10 atmospheres, provided the gases are mixed together before compression;
while a third Order, dated April 10, 1901, allows the compression of
acetylene into cylinders filled as completely as possible with porous matter,
with or without the presence of acetone, to a pressure not exceeding 150 lb.
per square inch provided the cylinders themselves have been tested by
hydraulic pressure for at least ten minutes to a pressure not less than double
[Footnote: In France the cylinders are tested to six times and in Russia to
five times their working pressure.] that which it is intended to use, provided
the solid substance is similar in every respect to the samples deposited at
the Home Office, provided its porosity does not exceed 80 per cent.,
provided air is excluded from every part of the apparatus before the gas is
compressed, provided the quantity of acetone used (if used at all) is not
sufficient to fill the porosity of the solid, provided the temperature is not
permitted to rise during compression, and provided compression only takes
place in premises approved by H.M.'s Inspectors of Explosives.

DILUTED ACETYLENE.--Acetylene is naturally capable of admixture or
dilution with any other gas or vapour; and the operation may be regarded in
either of two ways; (1) as a, means of improving the burning qualities of the
acetylene itself, or (2) as a means of conferring upon some other gas
increased luminosity. In the early days of the acetylene industry, generation

Page 352

was performed in so haphazard a fashion, purification so generally omitted,
and the burners were so inefficient, that it was proposed to add to the gas a
comparatively small proportion of some other gaseous fluid which should
be capable of making it burn without deposition of carbon while not
seriously impairing its latent illuminating power. One of the first diluents
suggested was carbon dioxide (carbonic acid gas), because this gas is very
easy and cheap to prepare; and because it was stated that acetylene would
bear an addition of 5 or even 8 per cent, of carbon dioxide and yet develop
its full degree of luminosity. This last assertion requires substantiation; for it
is at least a grave theoretical error to add a non-inflammable gas to a
combustible one, as is seen in the lower efficiency of all flames when
burning in common air in comparison with that which they exhibit in
oxygen; while from the practical aspect, so harmful is carbon dioxide in an
illuminating gas, that coal-gas and carburetted water-gas are frequently
most rigorously freed from it, because a certain gain in illuminating power
may often thus be achieved more cheaply than by direct enrichment of the
gas by addition of hydrocarbons. Being prepared from chalk and any cheap
mineral acid, hydrochloric by preference, in the cold, carbon dioxide is so
cheap that its price in comparison with that of acetylene is almost nil; and
therefore, on the above assumption, 105 volumes of diluted acetylene might
be made essentially for the same price as 100 volumes of neat acetylene,
and according to supposition emit 5 per cent. more light per unit of volume.

It is reported that several railway trains in Austria are regularly lighted with
acetylene containing 0.4 to 1.0 per cent. of carbon dioxide in order to
prevent deposition of carbon at the burners. The gas is prepared according
to a patent process which consists in adding a certain proportion of a
"carbonate" to the generator water. In the United Kingdom, also, there are
several installations supplying an acetylene diluted with carbon dioxide, the
gas being produced by putting into that portion of a water-to-carbide
generator which lies nearest to the water- supply some solid carbonate like
chalk, and using a dilute acid to attack the material. Other inventors have
proposed placing a solid acid, like oxalic, in the former part of a generator
and decomposing it with a carbonate solution; or they have suggested
putting into the generator a mixture of a solid acid and a solid soluble
carbonate, and decomposing it with plain water.

Page 353

Clearly, unless the apparatus in which such mixtures as these are intended
to be prepared is designed with considerable care, the amount of carbon
dioxide in the gas will be liable to vary, and may fall to zero. If any quantity
of carbide present has been decomposed in the ordinary way, there will be
free calcium hydroxide in the generator; and if the carbon dioxide comes
into contact with this, it will be absorbed, unless sufficient acid is employed
to convert the calcium carbonate (or hydroxide) into the corresponding
normal salt of calcium. Similarly, during purification, a material containing
any free lime would tend to remove the carbon dioxide, as would any
substance which became alkaline by retaining the ammonia of the crude
gas.

It cannot altogether be granted that the value of a process for diluting
acetylene with carbon dioxide has been established, except in so far as the
mere presence of the diluent may somewhat diminish the tendency of the
acetylene to polymerise as it passes through a hot burner (cf. Chapter VIII.).
Certainly as a fuel-gas the mixture would be less efficient, and the extra
amount of carbon dioxide produced by each flame is not wholly to be
ignored. Moreover, since properly generated and purified acetylene can be
consumed in proper burners without trouble, all reason for introducing
carbon dioxide has disappeared.

MIXTURES OF ACETYLENE AND AIR.--A further proposal for diluting
acetylene was the addition to it of air. Apart from questions of explosibility,
this method has the advantage over that of adding carbon dioxide that the
air, though not inflammable, is, in virtue of its contained oxygen, a
supporter of combustion, and is required in a flame; whereas carbon dioxide
is not only not a supporter of combustion, but is actually a product thereof,
and correspondingly more objectionable. According to some experiments
carried out by Dufour, neat acetylene burnt under certain conditions evolved
between 1.0 and 1.8 candle-power per litre- hour; a mixture of 1 volume of
acetylene with 1 volume of air evolved 1.4 candle-power; a mixture of 1
volume of acetylene with 1.2 volumes of air, 2.25 candle-power; and a
mixture of 1 volume of acetylene with 1.3 volumes of air, 2.70 candle-
power per litre-hour of acetylene in the several mixtures. Averaging the
figures, and calculating into terms of acetylene (only) burnt, Dufour found
neat acetylene to develop 1.29 candle-power per litre-hour, and acetylene

Page 354

diluted with air to develop 1.51 candle-power. When, however, allowance is
made for the cost and trouble of preparing such mixtures the advantage of
the process disappears; and moreover it is accompanied by too grave risks,
unless conducted on a largo scale and under most highly skilled
supervision, to be fit for general employment.

Fouché, however, has since found the duty, per cubic foot of neat acetylene
consumed in a twin injector burner at the most advantageous rate of 3.2
inches, to be as follows for mixtures with air in the proportions stated:

Percentage of air 0 17 27 33.5
Candles per cubic feet 38.4 36.0 32.8 26.0

At lower pressures, the duty of the acetylene when diluted appears to be
relatively somewhat higher. Figures which have been published in regard to
a mixture of 30 volumes of air and 70 volumes of acetylene obtained by a
particular system of producing such a mixture, known as the "Molet-
Boistelle," indicate that the admixture of air causes a slight increase in the
illuminating duty obtained from the acetylene in burners of various sizes.
The type of burner and the pressure employed in these experiments were
not, however, stated. This system has been used at certain stations on the
"Midi" railway in France. Nevertheless even where the admixture of air to
acetylene is legally permissible, the risk of obtaining a really dangerous
product and the nebulous character of the advantages attainable should
preclude its adoption.

In Great Britain the manufacture, importation, storage, and use of acetylene
mixed with air or oxygen, in all proportions and at all pressures, with or
without the presence of other substances, is prohibited by an Order in
Council dated July 1900; to which prohibition the mixture of acetylene and
air that takes place in a burner or contrivance in which the mixture is
intended to be burnt, and the admixture of air with acetylene that may
unavoidably occur in the first use or recharging of an apparatus (usually a
water-to-carbide generator), properly designed and constructed with a view
to the production of pure acetylene, are the solitary exceptions.

Page 355

MIXED CARBIDES.--In fact the only processes for diluting acetylene
which possess real utility are that of adding vaporised petroleum spirit or
benzene to the gas, as was described in Chapter X. under the name of
carburetted acetylene, and one other possible method of obtaining a diluted
acetylene directly from the gas-generator, to which a few words will now be
devoted. [Footnote: Mixtures of acetylene with relatively large proportions
of other illuminating gases, such as are referred to on subsequent pages, are
also, from one aspect, forms of diluted acetylene.] Calcium carbide is only
one particular specimen of a large number of similar metallic compounds,
which can be prepared in the electric furnace, or otherwise. Some of those
carbides yield acetylene when treated with water, some are not attacked,
some give liquid products, and some yield methane, or mixtures of methane
and hydrogen. Among the latter is manganese carbide. If, then, a mixture of
manganese carbide and calcium carbide is put into an ordinary acetylene
generator, the gas evolved will be a mixture of acetylene with methane and
hydrogen in proportions depending upon the composition of the carbide
mixture. It is clear that a suitable mixture of the carbides might be made by
preparing them separately and bulking the whole in the desired proportions;
while since manganese carbide can be won in the electric furnace, it might
be feasible to charge into such a furnace a mixture of lime, coke, and
manganese oxide calculated to yield a simple mixture of the carbides or a
kind of double carbide. Following the lines which have been adopted in
writing the present book, it is not proposed to discuss the possibility of
making mixed carbides; but it may be said in brief that Brame and Lewes
have carried out several experiments in this direction, using charges of lime
and coke containing (a) up to 20 per cent. of manganese oxide, and (b)
more than 60 per cent. of manganese oxide. In neither case did they succeed
in obtaining a material which gave a mixture of acetylene and methane
when treated with water; in case (a) they found the gas to be practically
pure acetylene, so that the carbide must have been calcium carbide only; in
case (b) the gas was mainly methane and hydrogen, so that the carbide must
have been essentially that of manganese alone. Mixed charges containing
between 20 and 60 per cent. of manganese oxide remain to be studied; but
whether they would give mixed carbides or no, it would be perfectly simple
to mix ready-made carbides of calcium and manganese together, if any
demand for a diluted acetylene should arise on a sufficiently large scale. It
is, however, somewhat difficult to appreciate the benefits to be obtained

Page 356

from forms of diluted acetylene other than those to which reference is made
later in this chapter.

There is, nevertheless, one modification of calcium carbide which, in a
small but important sphere, finds a useful rôle. It has been pointed out that a
carbide containing much calcium phosphide is usually objectionable,
because the gas evolved from it requires extra purification, and because
there is the (somewhat unlikely) possibility that the acetylene obtained from
such material before purification may be spontaneously inflammable. If,
now, to the usual furnace charge of lime and coke a sufficient quantity of
calcium phosphate is purposely added, it is possible to win a mixture of
calcium phosphide and carbide, or, as Bradley, Read, and Jacobs call it, a
"carbophosphide of calcium," having the formula Ca_5C_6P_2, which
yields a spontaneously inflammable mixture of acetylene, gaseous
phosphine, and liquid phosphine when treated with water, and which,
therefore, automatically gives a flame when brought into contact with the
liquid. The value of this material will be described in Chapter XIII.

GAS-ENRICHING.--Other methods of diluting acetylene consist in adding
a comparatively small proportion of it to some other gas, and may be
considered rather as processes for enriching that other gas with acetylene.
Provided the second gas is well chosen, such mixtures exhibit properties
which render them peculiarly valuable for special purposes. They have,
usually, a far lower upper limit of explosibility than that of neat acetylene,
and they admit of safe compression to an extent greatly exceeding that of
acetylene itself, while they do not lose illuminating power on compression.
The second characteristic is most important, and depends on the phenomena
of "partial pressure," which have been referred to in Chapter VI. When a
single gas is stored at atmospheric pressure, it is insensibly withstanding on
all sides and in all directions a pressure of roughly 15 lb. per square inch,
which is the weight of the atmosphere at sea-level; and when a mixture of
two gases, X and Y, in equal volumes is similarly stored it, regarded as an
entity, is also supporting a pressure of 15 lb. per square inch. But in every 1
volume of that mixture there is only half a volume of X and Y each; and,
ignoring the presence of its partner, each half-volume is evenly distributed
throughout a space of 1 volume. But since the volume of a gas stands in
inverse ratio to the pressure under which it is stored, the half-volume of X

Page 357

in the 1 volume of X + Y apparently stands at a pressure of half an
atmosphere, for it has expanded till it fills, from a chemical and physical
aspect, the space of 1 volume: suitable tests proving that it exhibits the
properties which a gas stored at a pressure of half an atmosphere should do.
Therefore, in the mixture under consideration, X and Y are both said to be
at a "partial pressure" of half an atmosphere, which is manifestly 7.5 lb. per
square inch. Clearly, when a gas is an entity (either an element or one single
chemical compound) partial and total pressure are identical. Now, it has
been shown that acetylene ceases to be a safe gas to handle when it is stored
at a pressure of 2 atmospheres; but the limit of safety really occurs when the
gas is stored at a partial pressure of 2 atmospheres. Neat acetylene,
accordingly, cannot be compressed above the mark 30 lb. shown on a
pressure gauge; but diluted acetylene (if the diluent is suitable) may be
compressed in safety till the partial pressure of the acetylene itself reaches 2
atmospheres. For instance, a mixture of equal volumes of X and Y (X being
acetylene) contains X at a partial pressure of half the total pressure, and
may therefore be compressed to (2 / 1/2 =) 4 atmospheres before X reaches
the partial pressure of 2 atmospheres; and therewith the mixture is brought
just to the limit of safety, any effect of Y one way or the other being
neglected. Similarly, a mixture of 1 volume of acetylene with 4 volumes of
Y may be safely compressed to a pressure of (2 / 1/5 =) 10 atmospheres, or,
broadly, a mixture in which the percentage of acetylene is x may be safely
compressed to a pressure not exceeding (2 / x/100) atmospheres. This fact
permits acetylene after proper dilution to be compressed in the same fashion
as is allowable in the case of the dissolved and absorbed gas described
above.

If the latent illuminating power of acetylene is not to be wasted, the diluent
must not be selected without thought. Acetylene burns with a very hot
flame, the luminosity of which is seriously decreased if the temperature is
lowered. As mentioned in Chapter VIII., this may be done by allowing too
much air to enter the flame; but it may also be effected to a certain extent by
mixing with the acetylene before combustion some combustible gas or
vapour which burns at a lower temperature than acetylene itself. Manifestly,
therefore, the ideal diluent for acetylene is a substance which possesses as
high a flame temperature as acetylene and a certain degree of intrinsic
illuminating power, while the lower the flame temperature of the diluent

Page 358

and the less its intrinsic illuminating power, the less efficiently will the
acetylene act as an enriching material. According to Love, Hempel,
Wedding, and others, if acetylene is mixed with coal-gas in amounts up to 8
per cent. or thereabouts, the illuminating power of the mixture increases
about 1 candle for every 1 per cent. of acetylene present: a fact which is
usually expressed by saying that with coal-gas the enrichment value of
acetylene is 1 candle per 1 per cent. Above 8 per cent., the enrichment value
of acetylene rises, Love having found an increase in illuminating power, for
each 1 per cent. of acetylene in the mixture, of 1.42 candles with 11.28 per
cent. of acetylene; and of 1.54 candles with 17.62 per cent. of acetylene.
Theoretically, if the illuminating power of acetylene is taken at 240 candles,
its enrichment value should be (240 / 100 =) 2.4 candles per 1 per cent.; and
since, in the case of coal-gas, its actual enrichment value falls seriously
below this figure, it is clear that coal-gas is not an economical diluent for it.
Moreover, coal-gas can be enriched by other methods much more cheaply
than with acetylene. Simple ("blue") water-gas, according to Love, requires
more than 10 per cent. of acetylene to be added to it before a luminous
flame is produced; while a mixture of 20.3 per cent. of acetylene and 79.7
per cent. of water-gas had an illuminating power of 15.47 candles. Every
addition to the proportion of acetylene when it amounted to 20 per cent. and
upwards of the mixture had a very appreciable effect on the illuminating
power of the latter. Thus with 27.84 per cent. of acetylene, the illuminating
power of the mixture was 40.87 candles; with 38.00 per cent. of acetylene it
was 73.96 candles. Acetylene would not be an economical agent to employ
in order to render water-gas an illuminating gas of about the quality of coal-
gas, but the economy of enrichment of water-gas by acetylene increases
rapidly with the degree of enrichment demanded of it. Carburetted water-
gas which, after compression under 16 atmospheres pressure, had an
illuminating power of about 17.5 candles, was enriched by additions of
acetylene. 4.5 per cent. of acetylene in the mixture gave an illuminating
power of 22.69 candles; 8.4 per cent., 29.54 candles; 11.21 per cent., 35.05
candles; 15.06 per cent., 42.19 candles; and 21.44 per cent., 52.61 candles.
It is therefore evident that the effect of additions of acetylene on the
illuminating power of carburetted water-gas is of the same order as its effect
on coal-gas. The enrichment value of the acetylene increases with its
proportion in the mixture; but only when the proportion becomes quite
considerable, and, therefore, the gas of high illuminating power, does

Page 359

enrichment by acetylene become economical. Methane (marsh-gas), owing
to its comparatively high flame temperature, and to the fact that it has an
intrinsic, if small, illuminating power, is a better diluent of acetylene than
carbon monoxide or hydrogen, in that it preserves to a greater extent the
illuminative value of the acetylene.

Actually comparisons of the effect of additions of various proportions of a
richly illuminating gas, such as acetylene, on the illuminative value of a gas
which has little or no inherent illuminating power, are largely vitiated by the
want of any systematic method for arriving at the representative
illuminative value of any illuminating gas. A statement that the illuminating
power of a gas is x candles is, strictly speaking, incomplete, unless it is
supplemented by the information that the gas during testing was burnt (1) in
a specified type of burner, and (2) either at a specified fixed rate of
consumption or so as to afford a light of a certain specified intensity. There
is no general agreement, even in respect of the statutory testing of the
illuminating power of coal-gas supplies, as to the observance of uniform
conditions of burning of the gas under test, and in regard to more highly
illuminating gases there is even greater diversity of conditions. Hence
figures such as those quoted above for the enrichment value of acetylene
inevitably show a certain want of harmony which is in reality due to the
imperfection or incompleteness of the modes of testing employed.
Relatively to another, one gas appears advantageously merely in virtue of
the conditions of assessing illuminating power having been more favourable
to it. Therefore enrichment values, such as those given, must always be
regarded as only approximately trustworthy in instituting comparisons
between either different diluent gases or different enriching agents.

ACETYLENE MIXTURES FOR RAILWAY-CARRIAGE LIGHTING.--In
modern practice, the gases which are most commonly employed for diluents
of acetylene, under the conditions now being considered, are cannel-coal
gas (in France) and oil-gas (elsewhere). Fowler has made a series of
observations on the illuminating value of mixtures of oil-gas and acetylene.
13.41 per cent. of acetylene improved the illuminating power of oil-gas
from 43 to 49 candles. Thirty-nine-candle-power oil-gas had its illuminating
power raised to about 60 candles by an admixture of 20 per cent. of
acetylene, to about 80 candles by 40 per cent. of acetylene, and to about 110

Page 360

candles by 60 per cent. of acetylene. The difficulty of employing mixtures
fairly rich in acetylene, or pure acetylene, for railway- carriage lighting, lies
in the poor efficiency of the small burners which yield from such rich gas a
light of 15 to 20 candle-power, such as is suitable for the purpose. For the
lighting of railway carriages it is seldom deemed necessary to have a flame
of more than 20 candle-power, and it is somewhat difficult to obtain such a
flame from oil-gas mixtures rich in acetylene, unless the illuminative value
of the gas is wasted to a considerable extent. According to Bunte, 15
volumes of coal-gas, 8 volumes of German oil-gas, and 1.5 volumes of
acetylene all yield an equal amount of light; from which it follows that 1
volume of acetylene is equivalent to 5.3 volumes of German oil-gas.

A lengthy series of experiments upon the illuminating power of mixtures of
oil-gas and acetylene in proportions ranging between 10 and 50 per cent. of
the latter, consumed in different burners and at different pressures, has been
carried out by Borck, of the German State Railway Department. The figures
show that per unit of volume such mixtures may give anything up to 6.75
times the light evolved by pure oil-gas; but that the latent illuminating
power of the acetylene is less advantageously developed if too much of it is
employed. As 20 per cent. of acetylene is the highest proportion which may
be legally added to oil- gas in this country, Borck's results for that mixture
may be studied:

_______________________________________________________________
_______
| | | | | | |
|
| | | | | | |
Propor- |
| | | | Consump- | | Consump- |
tionate |
| Kind of | No. of | Pres- | tion per | Candle- | tion per |
Illum- |
| Burner. | Burner | sure. | Hour. | Power. | Candle- |
inating |
| | | mm. | Litres. | | Hour. |
Power |
| | | | | | Litres. |
to Pure |

Page 361

| | | | | | |
Oil-Gas.|
|___________|________|_______|__________|_________|__________|_
________|
| | | | | | |
|
| Bray | 00 | 42 | 82 | 56.2 | 1.15 |
3.38 |
| " | 000 | 35 | 54 | 28.3 | 1.91 |
4.92 |
| " | 0000 | 35 | 43.3 | 16 | 2.71 |
4.90 |
| Oil-gas | | | | | |
|
| burner | 15 | 24 | 21 | 7.25 | 2.89 |
4.53 |
| " " | 30 | 15 | 22 | 10.5 | 2.09 |
3.57 |
| " " | 40 | 16 | 33.5 | 20.2 | 1.65 |
3.01 |
| " " | 60 | 33 | 73 | 45.2 | 1.62 |
3.37 |
|
|
| The oil-gas from which this mixture was prepared showing:
|
|
|
| Bray | 00 | 34 | 73.5 | 16.6 | 4.42 |
... |
| " | 000 | 30 | 48 | 6.89 | 6.96 |
... |
| " | 0000 | 28 | 39 | 3.26 | 11.6 |
... |
| Oil-gas | | | | | |
|
| burner | 15 | 21 | 19 | 1.6 | 11.8 |
... |
| " " | 30 | 14 | 21.5 | 2.94 | 7.31 |
... |
| " " | 40 | 15 | 33 | 6.7 | 4.92 |
... |
| " " | 60 | 25 | 60 | 13.4 | 4.40 |
... |
|___________|________|_______|__________|_________|__________|_
________|

Page 362

It will be seen that the original oil-gas, when compressed to 10
atmospheres, gave a light of 1 candle-hour for an average consumption of
7.66 litres in the Bray burners, and for a consumption of 7.11 litres in the
ordinary German oil-gas jets; while the mixture containing 20 per cent. of
acetylene evolved the same amount of light for a consumption of 2.02 litres
in Bray burners, or of 2.06 litres in the oil-gas jets. Again, taking No. 40 as
the most popular and useful size of burner, 1 volume of acetylene oil-gas
may be said to be equal to 3 volumes of simple oil-gas, which is the value
assigned to the mixture by the German Government officials, who, at the
prices ruling there, hold the mixture to be twice as expensive as plain oil-
gas per unit of volume, which means that for a given outlay 50 per cent.
more light may be obtained from acetylene oil-gas than from oil-gas alone.

This comparison of cost is not applicable, as it stands, to compressed oil-
gas, with and without enrichment by acetylene, in this country, owing to the
oils from which oil-gas is made being much cheaper and of better quality
here than in Germany, where a heavy duty is imposed on imported
petroleum. Oil-gas as made from Scotch and other good quality gas-oil in
this country, usually has, after compression, an illuminating duty of about 8
candles per cubic foot, which is about double that of the compressed
German oil-gas as examined by Borck.

Hence the following table, containing a summary of results obtained by H.
Fowler with compressed oil-gas, as used on English railways, must be
accepted rather than the foregoing, in so far as conditions prevailing in this
country are concerned. It likewise refers to a mixture of oil-gas and
acetylene containing 20 per cent. of acetylene.

_______________________________________________________________
_______
| | | | | |
|
| | | | | |
Ratio of |
| | |Consumption| |Candles per|
Illuminating |
| Burner. |Pressure.| per Hour. |Candle| Cubic Foot| Power
to that |

Page 363

| | Inches. |Cubic Feet.|Power.| per Hour. |of Oil-
gas [1] |
| | | | | | in
the same |
| | | | | |
Burner. |
|_____________|_________|___________|______|___________|_______
________|
| | | | | |
|
| Oil-gas . . | 0.7 | 0.98 | 12.5 | 12.72 |
1.65 |
| Bray 000 . | 0.7 | 1.17 | 14.4 | 12.30 |
1.57 |
| " 0000 . | 0.7 | 0.97 | 10.4 | 10.74 |
1.41 |
| " 00000 | 0.7 | 0.78 | 5.6 | 7.16 |
1.08 |
| " 000000 | 0.7 | 0.55 | 1.9 | 3.52 |
1.14 |
|_____________|_________|___________|______|___________|_______
________|

[Footnote 1: Data relating to the relative pecuniary values of acetylene
(carburetted or not), coal-gas, paraffin, and electricity as heating or
illuminating agents, are frequently presented to British readers after simple
recalculation into English equivalents of the figures which obtain in France
and Germany. Such a method of procedure is utterly incorrect, as it ignores
the higher prices of coal, coal-gas, and especially petroleum products on the
Continent of Europe, which arise partly from geographical, but mainly from
political causes.]

The mixture was tried also at higher pressures in the same burners, but with
less favourable results in regard to the duty realised. The oil-gas was also
tried at various pressures, and the most favourable result is taken for
computing the ratio in the last column. It is evident from this table that 1
volume of this acetylene-oil-gas mixture is equal at the most to 1.65 volume
of the simple oil-gas. Whether the mixture will prove cheaper under
particular conditions must depend on the relative prices of gas-oil and
calcium carbide at the works where the gas is made and compressed. At the
prevailing prices in most parts of Britain, simple oil-gas is slightly cheaper,
but an appreciable rise in the price of gas- oil would render the mixture with

Page 364

acetylene the cheaper illuminant. The fact remains, however, that per unit
weight or volume of cylinder into which the gas is compressed, acetylene
oil-gas evolves a higher candle- power, or the same candle-power for a
longer period, than simple, unenriched British oil-gas. Latterly, however,
the incandescent mantle has found application for railway-carriage lighting,
and poorer compressed gases have thereby been rendered available. Thus
coal-gas, to which a small proportion of acetylene has been added, may
advantageously displace the richer oil-gas and acetylene mixtures.

Patents have been taken out by Schwander for the preparation of a mixture
of acetylene, air, and vaporised petroleum spirit. A current of naturally
damp, or artificially moistened, air is led over or through a mass of calcium
carbide, whereby the moisture is replaced by an equivalent quantity of
acetylene; and this mixture of acetylene and air is carburetted by passing it
through a vessel of petroleum spirit in the manner adopted with air-gas. No
details as to the composition, illuminating power, and calorific values of the
gas so made have been published. It would clearly tend to be of highly
indefinite constitution and might range between what would be virtually
inferior carburetted acetylene, and a low-grade air-gas. It is also doubtful
whether the combustion of such gas would not be accompanied by too
grave risks to render the process useful.

Page 365

CHAPTER XII
SUNDRY USES

There are sundry uses for acetylene, and to some extent for carbide, which
are not included in what has been said in previous chapters of this book;
and to them a few words may be devoted.

In orchards and market gardens enormous damage is frequently done to the
crops by the ravages of caterpillars of numerous species. These caterpillars
cannot be caught by hand, and hitherto it has proved exceedingly difficult to
cope with them. However, when they have changed into the perfect state,
the corresponding butterflies and moths, like most other winged insects, are
strongly attracted by a bright light. As acetylene can easily be burnt in a
portable apparatus, and as the burners can be supplied with gas at such
comparatively high pressure that the flames are capable of withstanding
sharp gusts of wind even when not protected by glass, the brilliant light
given by acetylene forms an excellent method of destroying the insects
before they have had time to lay their eggs. Two methods of using the light
have been tried with astonishing success: in one a naked flame is supported
within some receptacle, such as a barrel with one end knocked out, the
interior of which is painted heavily with treacle; in the other the flame is
supported over an open dish filled with some cheap heavy oil (or perhaps
treacle would do equally well). In the first case the insects are attracted by
the light and are caught by the adhesive surfaces; in the second they are
attracted and singed, and then drowned in, or caught by, the liquid. Either a
well-made, powerful, vehicular lamp with its bull's- eye (if any) removed
could be used for this purpose, or a portable generator of any kind might be
connected with the burner through a flexible tube. It is necessary that the
lights should be lit just before dusk when the weather is fine and the nights
dark, and for some twenty evenings in June or July, exactly at the period of
the year when the perfect insects are coming into existence. In some of the
vineyards of Beaujolais, in France, where great havoc has been wrought by
the pyralid, a set of 10-candle-power lamps were put up during July 1901,

Page 366

at distances of 150 yards apart, using generators containing 6 oz. of carbide,
and dishes filled with water and petroleum 18 or 20 inches in diameter. In
eighteen nights, some twenty lamps being employed, the total catch of
insects was 170,000, or an average of 3200 per lamp per night. At French
prices, the cost is reported to have been 8 centimes per night, or 32
centimes per hectare (2.5 acres). In Germany, where school children are
occasionally paid for destroying noxious moths, two acetylene lamps
burning for twelve evenings succeeded in catching twice as many insects as
the whole juvenile population of a village during August 1902. A similar
process has been recommended for the destruction of the malarial mosquito,
and should prove of great service to mankind in infected districts. The
superiority of acetylene in respect of brilliancy and portability will at once
suggest its employment as the illuminant in the "light" moth-traps which
entomologists use for entrapping moths. In these traps, the insects, attracted
by the light, flutter down panes of glass, so inclined that ultimate escape is
improbable; while they are protected from injury through contact with the
flame by moans of an intervening sheet of glass.

Methods of spraying with carbide dust have been found useful in treating
mildew in vines; while a process of burying small quantities of carbide at
the roots has proved highly efficacious in exterminating phylloxera in the
French and Spanish vineyards. It was originally believed that the impurities
of the slowly formed acetylene, the phosphine in particular, acted as toxic
agents upon the phylloxera; and therefore carbide containing an extra
amount of decomposable phosphides was specially manufactured for the
vine-growers. But more recently it has been argued, with some show of
reason, that the acetylene itself plays a part in the process, the effects
produced being said to be too great to be ascribed wholly to the phosphine.
It is well known that many hydrocarbon vapours, such as the vapour of
benzene or of naphthalene, have a highly toxic action on low organisms,
and the destructive effect of acetylene on phylloxera may be akin to this
action.

As gaseous acetylene will bear a certain amount of pressure in safety--a
pressure falling somewhat short of one effective atmosphere--and as
pressure naturally rises in a generating apparatus where calcium carbide
reacts with water, it becomes possible to use this pressure as a source of

Page 367

energy for several purposes. The pressure of the gas may, in fact, be
employed either to force a stream of liquid through a pipe, or to propel
certain mechanism. An apparatus has been constructed in France on the
lines of some portable fire-extinguishing appliances in which the pressure
set up by the evolution of acetylene in a closed space produces a spray of
water charged with lime and gas under the pressure obtaining; the liquid
being thrown over growing vines or other plants in order to destroy
parasitic and other forms of life. The apparatus consists of a metal cylinder
fitted with straps so that it can be carried by man or beast. At one end it has
an attachment for a flexible pipe, at the other end a perforated basket for
carbide introduced and withdrawn through a "man-hole" that can be tightly
closed. The cylinder is filled with water to a point just below the bottom of
the basket when the basket is uppermost; the carbide charge is then inserted,
and the cover fastened down. As long as the cylinder is carried in the same
position, no reaction between the carbide and the water occurs, and
consequently no pressure arises; but on inverting the vessel, the carbide is
wetted, and acetylene is liberated in the interior. On opening the cock on the
outlet pipe, a stream of liquid issues and may be directed as required. By
charging the cylinder in the first place with a solution of copper sulphate,
the liquid ejected becomes a solution and suspension of copper and calcium
salts and hydroxides, resembling "Bordeaux mixture," and may be
employed as such. In addition, it is saturated with acetylene which adds to
its value as a germicide.

The effective gas pressure set up in a closed generator has also been
employed in Italy to drive a gas-turbine, and so to produce motion. The
plant has been designed for use in lighthouses where acetylene is burnt, and
where a revolving or flashing light is required. The gas outlet from a
suitably arranged generator communicates with the inlet of a gas- turbine,
and the outlet of the turbine is connected to a pipe leading to the acetylene
burners. The motion of the turbine is employed to rotate screens, coloured
glasses, or any desired optical arrangements round the flames; or, in other
situations, periodically to open and close a cock on the gas-main leading to
the burners. In the latter case, a pilot flame fed separately is always alight,
and serves to ignite the gas issuing from the main burners when the cock is
opened.

Page 368

Another use for acetylene, which is only dependent upon a suitably lowered
price for carbide to become of some importance, consists in the preparation
of a black pigment to replace ordinary lampblack. One method for this
purpose has been elaborated by Hubou. Acetylene is prepared from carbide
smalls or good carbide, according to price, and the gas is pumped into small
steel cylinders to a pressure of 2 atmospheres. An electric spark is then
passed, and the gas, standing at its limit of safety, immediately dissociates,
yielding a quantitative amount of hydrogen and free carbon. The hydrogen
is drawn off, collected in holders, and used for any convenient purpose; the
carbon is withdrawn from the vessel, and is ready for sale. At present the
pigment is much too expensive, at least in British conditions, to be available
in the manufacture of black paint; but its price would justify its employment
in the preparation of the best grades of printers' ink. One of the authors has
examined an average sample and has found it fully equal in every way to
blacks, such as those termed "spirit blacks," which fetch a price
considerably above their real value. It has a pure black cast of tint, is free
from greasy matter, and can therefore easily be ground into water, or into
linseed oil without interfering with the drying properties of the latter.
Acetylene black has also been tried in calico printing, and has given far
better results in tone and strength than other blacks per unit weight of
pigment. It may be added that the actual yield of pigment from creosote
oils, the commonest raw material for the preparation of lampblack
("vegetable black"), seldom exceeds 20 or 25 per cent., although the oil
itself contains some 80 per cent, of carbon. The yield from acetylene is
clearly about 90 per cent., or from calcium carbide nearly 37.5 per cent, of
the original weight.

An objection urged against the Hubou process is that only small quantities
of the gas can be treated with the spark at one time; if the cylinders are too
large, it is stated, tarry by-products are formed. A second method of
preparing lampblack (or graphite) from acetylene is that devised by Frank,
and depends on utilising the reactions between carbon monoxide or dioxide
and acetylene or calcium carbide, which have already been sketched in
Chapter VI. When acetylene is employed, the yield is pure carbon, for the
only by-product is water vapour; but if the carbide process is adopted, the
carbon remains mixed with calcium oxide. Possibly such a material as
Frank's carbide process would give, viz., 36 parts by weight of carbon

Page 369

mixed with 56 parts of quicklime or 60 parts of carbon mixed with 112
parts of quicklime, might answer the purpose of a pigment in some black
paints where the amount of ash left on ignition is not subject to
specification. Naturally, however, the lime might be washed away from the
carbon by treatment with hydrochloric acid; but the cost of such a purifying
operation would probably render the residual pigment too expensive to be
of much service except (conceivably) in the manufacture of certain grades
of printers' ink, for which purpose it might compete with the carbon
obtainable by the Hubou process already referred to.

Acetylene tetrachloride, or tetrachlorethane, C_2H_2Cl_4, is now produced
for sale as a solvent for chlorine, sulphur, phosphorus, and organic
substances such as fats. It may be obtained by the direct combination of
acetylene and chlorine as explained in Chapter VI., but the liability of the
reaction to take place with explosive violence would preclude the direct
application of it on a commercial scale. Processes free from such risk have
now, however, been devised for the production of tetrachlorethane. One
patented by the Salzbergwerk Neu-Stassfurt consists in passing acetylene
into a mixture of finely divided iron and chloride of sulphur. The iron acts
as a catalytic. The liquid is kept cool, and as soon as the acetylene passes
through unabsorbed, its introduction is stopped and chlorine is passed in.
Acetylene and chlorine are then passed in alternately until the liquid finally
is saturated with acetylene. The tetrachlorethane, boiling at 147° C., is then
distilled off, and the residual sulphur is reconverted to the chloride for use
again in the process. A similar process in which the chlorine is used in
excess is applicable also to the production of hexachlorethane.

Dependent upon price, again, are several uses for calcium carbide as a
metallurgical or reducing reagent; but as those are uses for carbide only as
distinguished from acetylene, they do not fall within the purview of the
present book.

When discussing, in Chapter III., methods for disposing of the lime sludge
coming from an acetylene generator, it was stated that on occasion a use
could be found for this material. If the carbide has been entirely
decomposed in an apparatus free from overheating, the waste lime is
recovered as a solid mass or as a cream of lime practically pure white in

Page 370

colour. Sometimes, however, as explained in Chapter II., the lime sludge is
of a bluish grey tint, even in cases where the carbide decomposed was of
good quality and there was no overheating in the generator. Such
discoloration is of little moment for most of the uses to which the sludge
may be put. The residue withdrawn from a carbide-to-water generator is
usually quite fluid; but when allowed to rest in a suitable pit or tank, it
settles down to a semi-solid or pasty mass which contains on a rough
average 47 per cent. of water and 53 per cent. of solid matter, the amount of
lime present, calculated as calcium oxide, being about 40 per cent. Since 64
parts by weight of pure calcium carbide yield 74 parts of dry calcium
hydroxide, it may be said that 1 part of ordinary commercial carbide should
yield approximately 1.1 parts of dry residue, or 2.1 parts of a sludge
containing 47 per cent. of moisture; and sludge of this character has been
stated by Vogel to weigh about 22.5 cwt. per cubic yard.

Experience has shown that those pasty carbide residues can be employed
very satisfactorily, and to the best advantage from the maker's point of view,
by builders and decorators for the preparation of ordinary mortar or lime-
wash. The mortar made from acetylene lime has been found equal in
strength and other properties to mortar compounded from fresh slaked lime;
while the distemper prepared by diluting the sludge has been used most
successfully in all places where a lime-wash is required, e.g., on fruit-trees,
on cattle-pens, farm-buildings, factories, and the "offices" of a residence.
Many of the village installations abroad sell their sludge to builders for the
above-mentioned purposes at such a price that their revenue accounts are
materially benefited by the additional income. The sludge is also found
serviceable for softening the feed-water of steam boilers by the common
liming process; although it has been stated that the material contains certain
impurities--notably "fatty matter"--which becomes hydrolysed by the steam,
yielding fatty acids that act corrosively upon the boiler-plates. This
assertion would appear to require substantiation, but a patent has been taken
out for a process of drying the sludge at a temperature of 150° to 200° C. in
order to remove the harmful matter by the action of the steam evolved. So
purified, it is claimed, the lime becomes fit for treating any hard potable or
boiler- feed water. It is very doubtful, however, whether the intrinsic value
of acetylene lime is such in comparison with the price of fresh lime that,

Page 371

with whatever object in view, it would bear the cost of any method of
artificial drying if obtained from the generators in a pasty state.

When, on the other hand, the residue is naturally dry, or nearly so, it is
exactly equal to an equivalent quantity of quick or slaked lime as a dressing
for soil. In this last connexion, however, it must be remembered that only
certain soils are improved by an addition of lime in any shape, and therefore
carbide residues must not be used blindly; but if analysis indicates that a
particular plot of ground would derive benefit from an application of lime,
acetylene lime is precisely as good as any other description. Naturally a
residue containing unspent carbide, or contaminated with tarry matter, is
essentially valueless (except as mentioned below); while it must not be
forgotten that a solid residue if it is exposed to air, or a pasty residue if not
kept under water, will lose many of its useful properties, because it will be
partially converted into calcium carbonate or chalk.

Nevertheless, in some respects, the residue from a good acetylene generator
is a more valuable material, agriculturally speaking, than pure lime. It
contains a certain amount of sulphur, &c., and it therefore somewhat
resembles the spent or gas lime of the coal-gas industry. This sulphur,
together, no doubt, with the traces of acetylene clinging to it, renders the
residue a valuable material for killing the worms and vermin which tend to
infest heavily manured and under-cultivated soil. Acetylene lime has been
found efficacious in exterminating the "finger-and-toe" of carrots, the
"peach-curl" of peach-trees, and in preventing cabbages from being
"clubbed." It may be applied to the ground alone, or after admixture with
some soil or stable manure. The residue may also be employed, either alone
or mixed with some agglomerate, in the construction of garden paths and
the like.

If the residues are suitably diluted with water and boiled with (say) twice
their original weight of flowers of sulphur, the product consists of a mixture
of various compounds of calcium and sulphur, or calcium sulphides--which
remain partly in solution and partly in the solid state. This material, used
either as a liquid spray or as a moist dressing, has been said to prove a
useful garden insecticide and weed-killer.

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There are also numerous applications of the acetylene light, each of much
value, but involving no new principle which need be noticed. The light is so
actinic, or rich in rays acting upon silver salts, that it is peculiarly useful to
the photographer, either for portraiture or for his various positive printing
operations. Acetylene is very convenient for optical lantern work on the
small scale, or where the oxy-hydrogen or oxy-coal-gas light cannot be
used. Its intensity and small size make its self-luminous flame preferable on
optical grounds to the oil-lamp or the coal-gas mantle; but the illuminating
surface is nevertheless too large to give the best results behind such
condensers as have been carefully worked to suit a source of light scarcely
exceeding the dimensions of a point. For lantern displays on very large
screens, or for the projection of a powerful beam of light to great distances
in one direction (as in night signalling, &c.), the acetylene blowpipe fed
with pure oxygen, or with air containing more than its normal proportion of
oxygen, which is discussed in Chapter IX., is specially valuable, more
particularly if the ordinary cylinder of lime is replaced by one of magnesia,
zirconia, or other highly refractory oxide.

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CHAPTER XIII
PORTABLE ACETYLENE LAMPS AND PLANT

It will be apparent from what has been said in past chapters that the
construction of a satisfactory generator for portable purposes must be a
problem of considerable complexity. A fixed acetylene installation tends to
work the more smoothly, and the gas evolved therefrom to burn the more
pleasantly, the more technically perfect the various subsidiary items of the
plant are; that is to say, the more thoroughly the acetylene is purified, dried,
and delivered at a strictly constant pressure to the burners and stoves.
Moreover, the efficient behaviour of the generator itself will depend more
upon the mechanical excellence and solidity of its construction than (with
one or two exceptions) upon the precise system to which it belongs. And,
lastly, the installation will, broadly speaking, work the better, the larger the
holder is in proportion to the demands ever made upon it; while that holder
will perform the whole duty of a gasholder more effectually if it belongs to
the rising variety than if it is a displacement holder. All these requirements
of a good acetylene apparatus have to be sacrificed to a greater or less
extent in portable generators; and since the sacrifice becomes more serious
as the generator is made smaller and lighter in weight, it may be said in
general terms that the smaller a portable (or, indeed, other) acetylene
apparatus is, the less complete or permanent satisfaction will it give its user.
Again, small portable apparatus are only needed to develop intensities of
light insignificant in comparison with those which may easily be won from
acetylene on a larger scale; they are therefore fitted with smaller burners,
and those burners are not merely small in terms of consumption and
illuminating power, but not infrequently are very badly constructed, and are
relatively deficient in economy or duty. Thus any comparisons which may
be made on lines similar to those adopted in Chapter I., or between unit
weights, volumes, or monetary equivalents of calcium carbide, paraffin,
candles, and colza oil, become utterly incorrect if the carbide is only
decomposed in a small portable generator fitted with an inefficient jet; first,
because the latent illuminating power of the acetylene evolved is largely

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wasted; secondly, because any gas produced over and above that capable of
instant combustion must be blown off from a vent-pipe; and thirdly, because
the carbide itself tends to be imperfectly decomposed, either through a
defect in the construction of the lamp, or through the brief and interrupted
requirements of the consumer.

In several important respects portable acetylene apparatus may be divided
into two classes from a practical point of view. There is the portable table or
stand lamp intended for use in an occupied room, and there is the hand or
supported lamp intended for the illumination of vehicles or open-air spaces.
Economy apart, no difficulty arises from imperfect combustion or escape of
unburnt gas from an outdoor lamp, but in a room the presence of unburnt
acetylene must always be offensive even if it is not dangerous; while the
combustion products of the impurities--and in a portable generator
acetylene cannot be chemically purified--are highly objectionable. It is
simply a matter of good design to render any form of portable apparatus
safe against explosion (employment of proper carbide being assumed), for
one or more vent-pipes can always be inserted in the proper places; but
from an indoor lamp those vent-pipes cannot be made to discharge into a
place of safety, while, as stated before, a generator in which the vent-pipes
come into action with any frequency is but an extravagant piece of
apparatus for the decomposition of so costly a material as calcium carbide.
Looked at from one aspect the holder of a fixed apparatus is merely an
economical substitute for the wasteful vent- pipe, because it is a place in
which acetylene can be held in reserve whenever the make exceeds the
consumption in speed. It is perhaps possible to conceive of a large table
acetylene lamp fitted with a water- sealed rising holder; but for vehicular
purposes the displacement holder is practically the only one available, and
in small apparatus it becomes too minute in size to be of much service as a
store for the gas produced by after-generation. Other forms of holder have
been suggested by inventors, such as a collapsible bag of india-rubber or the
like; but rubber is too porous, weak, and perishable a material to be
altogether suitable. If it is possible, by bringing carbide and water into
mutual contact in predetermined quantities, to produce gas at a uniform
rate, and at one which corresponds with the requirements of the burner, in a
small apparatus--and experience has shown it to be possible within
moderately satisfactory limits--it is manifest that the holder is only needed

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to take up the gas of after-generation; and in Chapters II. and III. it was
pointed out that after-generation only occurs when water is brought into
contact with an excess of carbide. If, then, the opposite system of
construction is adopted, and carbide is fed into water mechanically, no
after-generation can take place; and provided the make of gas can be
controlled in a small carbide-feed generator as accurately as is possible in a
small water-to-carbide generator, the carbide-feed principle will exhibit
even greater advantages in portable apparatus than it does in plant of
domestic size. Naturally almost every variety of carbide-feeding gear,
especially when small, requires or prefers granulated (or granulated and
"treated") carbide; and granulated carbide must inevitably be considerably
more expensive per unit of light evolved than the large material, but
probably in the application to which the average portable acetylene
apparatus is likely to be put, strict economy is not of first consequence. In
portable acetylene generators of the carbide-feed type, the supply is
generally governed by the movements of a mushroom-headed or conical
valve at the mouth of a conical carbide vessel; such movements occurring
in sympathy with the alterations in level of the water in the decomposing
chamber, which is essentially a small displacement holder also, or being
produced by the contraction of a flexible chamber through which the gas
passes on its way to the burner. So far as it is safe to speak definitely on a
matter of this kind, the carbide-feed device appears to work satisfactorily in
a stationary (e.g., table) lamp; but it is highly questionable whether it could
be applied to a vehicular apparatus exposed to any sensible amount of
vibration. The device is satisfactory on the table of an occupied room so far,
be it understood, as any small portable generators can be: it has no holder,
but since no after-generation occurs, no holder is needed; still the
combustion products contaminate the room with all the sulphur and
phosphorus of the crude acetylene.

For vehicular lamps, and probably for hand lanterns, the water-to-carbide
system has practically no alternative (among actual generators), and safety
and convenience have to be gained at the expense of the carbide. In such
apparatus the supply of water is usually controlled ultimately by pressure,
though a hand-operated needle-valve is frequently put on the water tube.
The water actually reaches the carbide either by dropping from a jet, by
passing along, upwards or downwards, a "wick" such as is used in oil-

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lamps, or by percolating through a mass of porous material like felt. The
carbide is held in a chamber closed except at the gas exit to the burner and
at the inlet from the water reservoir: so that if gas is produced more rapidly
than the burner takes it, more water is prevented from entering, or the water
already present is driven backwards out of the decomposing chamber into
some adjoining receptacle. It is impossible to describe in detail all the lamps
which have been constructed or proposed for vehicular use; and therefore
the subject must be approached in general terms, discussing simply the
principles involved in the design of a safe portable generator.

In all portable apparatus, and indeed in generators of larger dimensions, the
decomposing chamber must be so constructed that it can never, even by
wrong manipulation, be sealed hermetically against the atmosphere. If there
is a cock on the water inlet tube which is capable of being completely shut,
there must be no cock between the decomposing chamber and the burner. If
there is a cock between the carbide vessel and the burner, the water inlet
tube must only be closed by the water, being water-sealed, in fact, so that if
pressure rises among the carbide the surplus gas may blow the seal or
bubble through the water in the reservoir. If the water-supply is mainly
controlled by a needle-valve, it is useful to connect the burner with the
carbide vessel through a short length of rubber tube; and if this plan is
adopted, a cock can, if desired, be put close to the burner. The rubber should
not be allowed to form a bend hanging down, or water vapour, &c., may
condense and extinguish the flame. In any case there should be a steady fall
from the burner to the decomposing chamber, or to some separate catch-pit
for the products of condensation. Much of the success attainable with small
generators will depend on the water used. If it is contaminated with
undissolved matter, the dirt will eventually block the fine orifices,
especially the needle-valve, or will choke the pores of the wick or the felt
pad. If the water contains an appreciable amount of "temporary hardness,"
and if it becomes heated much in the lamp, fur will be deposited sooner or
later, and will obviously give trouble. Where the water reservoir is at the
upper part of the lamp, and the liquid is exposed to the heat of the flame, fur
will appear quickly if the water is hard. Considerable benefit would accrue
to the user of a portable lamp by the employment of rain water filtered, if
necessary, through fabric or paper. The danger of freezing in very severe
weather may be prevented by the use of calcium chloride, or preferably,

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perhaps, methylated spirit in the water (cf. Chapter III., p. 92). The
disfavour with which cycle and motor acetylene lamps are frequently
regarded by nocturnal travellers, other than the users thereof, is due to
thoughtless design in the optical part of such lamps, and is no argument
against the employment of acetylene. By proper shading or deflection of the
rays, the eyes of human beings and horses can be sufficiently protected
from the glare, and the whole of the illumination concentrated more
perfectly on the road surface and the lower part of approaching objects--a
beam of light never reaching a height of 5 feet above the ground is all that
is needed to satisfy all parties.

As the size of the generator rises, conditions naturally become more suited
to the construction of a satisfactory apparatus; until generators intended to
supply light to the whole of (say) a railway carriage, or the head and cab
lamps of a locomotive, or for the outside and inside lighting of an omnibus
are essentially generators of domestic dimensions somewhat altered in
internal construction to withstand vibration and agitation. As a rule there is
plenty of space at the side of a locomotive to carry a generator fitted with a
displacement holder of sufficient size, which is made tall rather than wide,
to prevent the water moving about more than necessary. From the boiler,
too, steam can be supplied to a coil to keep the liquid from freezing in
severe weather. Such apparatus need not be described at length, for they can
be, and are, made on lines resembling those of domestic generators, though
more compactly, and having always a governor to give a constant pressure.
For carriage lighting any ordinary type of generator, preferably, perhaps,
fitted with a displacement holder, can be erected either in each corridor
carriage, or in a brake van at the end of the train. Purifiers may be added, if
desired, to save the burners from corrosion; but the consumption of
unpurified gas will seldom be attended by hygienic disadvantages, because
the burners will be contained in closed lamps, ventilating into the outside
air. The generator, also, may conveniently be so constructed that it is fed
with carbide from above the roof, and emptied of lime sludge from below
the floor of the vehicle. It can hardly be said that the use of acetylene
generated on board adds a sensible risk in case of collision. In the event of a
subsequent fire, the gas in the generator would burn, but not explode; but in
view of the greater illuminating power per unit volume of carbide than per
equal volume of compressed oil- gas, a portable acetylene generator should

Page 378

be somewhat less objectionable than broken cylinders of oil-gas if a fire
should follow a railway accident of the usual kind. More particularly by the
use of "cartridges" of carbide, a railway carriage generator can be
constructed of sufficient capacity to afford light for a long journey, or even
a double journey, so that attention would be only required (in the ordinary
way) at one end of the line.

Passing on from the generators used for the lighting of vehicles and for
portable lamps for indoor lighting to the considerably larger portable
generators now constructed for the supply of acetylene for welding
purposes and for "flare" lamps, it will be evident that they may embody
most or all of the points which are essential to the proper working of a fixed
generator for the supply of a small establishment. The holder will generally
be of the displacement type, but some of these larger portable generators are
equipped with a rising holder. The generators are, naturally, automatic in
action, but may be either of the water-to-carbide or carbide-to-water type--
the latter being preferable in the larger sizes intended for use with the oxy-
acetylene blow-pipe for welding, &c., for which use a relatively large
though intermittent supply of acetylene is called for. The apparatus is either
carried by means of handles or poles attached to it, or is mounted on a
wheelbarrow or truck for convenience of transport to the place where it is to
be used. The so called "flare" lamps, which are high power burners
mounted, with or without a reflector, above a portable generator, are
extremely useful for lighting open spaces where work has to be carried on
temporarily after nightfall, and are rapidly displacing oil-flares of the
Lucigen type for such purposes.

The use of "cartridges" of calcium carbide has already been briefly referred
to in Chapters II. and III. These cartridges are usually either receptacles of
thin sheet-metal, say tin plate, or packages of carbide wrapped up in grease
proof paper or the like. If of metal, they may have a lid which is detached or
perforated before they are put into the generator, or the generator (when
automatic and of domestic size) may be so arranged that a cartridge is
punctured in one or more places whenever more gas is required. If wrapped
in paper, the cartridges may be dropped into water by an automatic
generator at the proper times, the liquid then loosening the gum and so
gaining access to the interior; or one spot may be covered by a drape of

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porous material (felt) only, through which the water penetrates slowly. The
substance inside the cartridge may be ordinary, granulated, or "treated"
carbide. Cartridges or "sticks" of carbide are also made without wrappings,
either by moistening powdered carbide with oil and compressing the whole
into moulds, or by compressing dry carbide dust and immersing the sticks
in oil or molten grease. The former process is said to cause the carbide to
take up too much oil, so that sticks made by the second method are reputed
preferable. All these cartridges have the advantage over common carbide of
being more permanent in damp air, of being symmetrical in shape, of
decomposing at a known speed, and of liberating acetylene in known
quantity; but evidently they are more expensive, owing to the cost of
preparing them, &c. They may be made more cheaply from the dust
produced in the braking of carbide, but in that case the yield of gas will be
relatively low.

It is manifest that, where space is to spare, purifiers containing the materials
mentioned in Chapter V. can be added to any portable acetylene apparatus,
provided also that the extra weight is not prohibitive. Cycle lamps and
motor lamps must burn an unpurified gas unpurified from phosphorus and
sulphur; but it is always good and advisable to filter the acetylene from dust
by a plug of cotton wool or the like, in order to keep the burners as clear as
may be. A burner with a screwed needle for cleaning is always
advantageous. Formerly the burners used on portable acetylene lamps were
usually of the single jet or rat-tail, or the union jet or fish tail type, and
exhibited in an intensified form, on account of their small orifices, all the
faults of these types of burners for the consumption of acetylene (see
Chapter VIII.). Now, however, there are numerous special burners adapted
for use in acetylene cycle and motor lamps, &c., and many of these are of
the impinging jet type, and some have steatite heads to prevent distortion by
the heat. One such cycle- lamp burner, as sold in England by L. Wiener, of
Fore Street, London, is shown in Fig. 21. A burner constructed like the
"Kona" (Chapter VIII.) is made in small sizes (6, 8 and 10 litres per hour)
for use in vehicular lamps, under the name of the "Konette," by Falk,
Stadelmann and Co., Ltd., of London, who also make a number of other
small impinging jet burners. A single jet injector burner on the "Phôs"
principle is made in small sizes by the Phôs Co., of London, specially for
use in lamps on vehicles.

Page 380

Nevertheless, although satisfactory medium-sized vehicular lamps for the
generation of acetylene have been constructed, the best way of using
acetylene for all such employments as these is to carry it ready made in a
state of compression. For railway purposes, where an oil-gas plant is in
existence, and where it is merely desired to obtain a somewhat brighter
light, the oil-gas may be enriched with 20 per cent. of acetylene, and the
mixed gas pumped into the same cylinders to a pressure of 10 atmospheres,
as mentioned in Chapter XI.; the only alteration necessary being the
substitution of suitable small burners for the common oil-gas jets. As far as
the plant is concerned, all that is required is a good acetylene generator,
purifier, and holder from which the acetylene can be drawn or forced
through a meter into a larger storage holder, the meter being connected by
gearing with another meter on the pipe leading from the oil-gas holder to
the common holder, so that the necessary proportions of the two gases shall
be introduced into the common holder simultaneously. From this final
holder the enriched gas will be pumped into the cylinders or into a storage
cylinder, by means of a thoroughly cooled pump, so that the heat set free by
the compression may be safely dissipated.

Whenever still better light is required in railway carriages, as also for the
illumination of large, constantly used vehicles, such as omnibuses, the
acetone process (cf. Chapter XI.) exhibits notable advantages. The light so
obtained is the light of neat acetylene, but the gas is acetylene having an
upper limit of explosibility much lower than usual because of the vapour of
acetone in it. In all other respects the presence of the acetone will be
unnoticeable, for it is a fairly pure organic chemical body, which burns in
the flame completely to carbon dioxide and water, exactly as acetylene

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itself does. If the acetylene is merely compressed into porous matter
without acetone, the gas burnt is acetylene simply; but per unit of volume or
weight the cylinders will not be capable of developing so much light.

In the United States, at least one railway system (The Great Northern) has a
number of its passenger coaches lighted by means of plain acetylene carried
in a state of compression in cylinders without porous matter. The gas is
generated, filtered from dust, and stored in an ordinary rising holder at a
factory alongside the line; being drawn from this holder through a drier to
extract moisture, and through a safety device, by a pump which, in three
stages, compresses the acetylene into large storage reservoirs. The safety
device consists of a heavy steel cylinder filled with some porous substance
which, like the similar material of the acetone cylinders, prevents any
danger of the acetylene contained in the water-sealed holder being
implicated in an explosion starting backwards from the compression, by
extinguishing any spark which might be produced there. The plant on the
trains comprises a suitable number of cylinders, filled by contact with the
large stores of gas to a pressure of 10 atmospheres, pipes of fusible metal
communicating with the lamps, and ordinary half-foot acetylene burners.
The cylinders are provided with fusible plugs, so that, in the event of a fire,
they and the service- pipes would melt, allowing the gas to escape freely
and burn in the air, instead of exploding or dissociating explosively within
the cylinders should the latter be heated by any burning woodwork or the
like. It is stated that this plan of using acetylene enables a quantity of gas to
be carried under each coach which is sufficient for a run of from 53 to 70
hours' duration, or of over 3600 miles; that is to say, enables the train, in the
conditions obtaining on the line in question, to make a complete "round
trip" without exhaustion of its store of artificial light. The system has been
in operation for some years, and appears to have been so carefully managed
that no accident has arisen; but it is clear that elements of danger are present
which are eliminated when the cylinders are loaded with porous matter and
acetone. The use of a similar system of compressed acetylene train lighting
in South America has been attended with a disastrous explosion, involving
loss of life.

It may safely be said that the acetone system, or less conveniently perhaps
the mere compression into porous matter, is the best to adopt for the table-

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lamp which is to be used in occupied rooms Small cylinders of such shapes
as to form an elegant base for a table-lamp on more or less conventional
lines would be easy to make. They would be perfectly safe to handle. If
accidentally or wilfully upset, no harm would arise. By deliberate ill-
treatment they might be burst, or the gas-pipe fractured below the reducing
valve, so that gas would escape under pressure for a time; but short of this
they would be as devoid of extra clangor in times of fire as the candle or the
coal-gas burner. Moreover, they would only contaminate the air with carbon
dioxide and water vapour, for the gas is purified before compression; and
modern investigations have conclusively demonstrated that the ill effects
produced in the air of an imperfectly ventilated room by the extravagant
consumption of coal-gas depend on the accumulation of the combustion
products of the sulphur in the gas rather than upon the carbon dioxide set
free.

One particular application of the portable acetylene apparatus is of special
interest. As calcium carbide evolves an inflammable gas when it merely
comes into contact with water, it becomes possible to throw into the sea or
river, by hand or by ejection from a mortar, a species of bomb or portable
generator which is capable of emitting a powerful beam of light if only
facilities are present for inflaming the acetylene generated; and it is quite
easy so to arrange the interior of such apparatus that they can be kept ready
for instant use for long periods of time without sensible deterioration, and
that they can be recharged after employment. Three methods of firing the
gas have been proposed. In one the shock or contact with the water brings a
small electric battery into play which produces a spark between two
terminals projecting across the burner orifice; in the second, a cap at the
head of the generator contains a small quantity of metallic potassium, which
decomposes water with such energy that the hydrogen liberated catches fire;
and in the third a similar cap is filled with the necessary quantity of calcium
phosphide, or the "carbophosphide of calcium" mentioned in Chapter XI.,
which yields a flame by the immediate ignition of the liquid phosphine
produced on the attack of water. During the two or three seconds consumed
in the production of the spark or pilot flame, the water is penetrating the
main charge of calcium carbide in the interior of the apparatus, until the
whole is ready to give a bright light for a time limited only by the capacity
of the generator. It is obvious that such apparatus may be of much service at

Page 383

sea: they may be thrown overboard to illuminate separate lifebuoys in case
of accident, or be attached to the lifebuoys they are required to illuminate,
or be used as lifebuoys themselves if fitted with suitable chains or ropes;
they may be shot ahead to illuminate a difficult channel, or to render an
enemy visible in time of war. Several such apparatus have already been
constructed and severely tested; they appear to give every satisfaction. They
are, of course, so weighted that the burner floats vertically, while buoyancy
is obtained partly by the gas evolved, and partly by a hollow portion of the
structure containing air. Cartridges of carbide and caps yielding a self-
inflammable gas can be carried on board ship, by means of which the
torches or lifebuoys may be renewed after service in a few minutes' time.

Page 384

CHAPTER XIV
VALUATION AND ANALYSIS OF CARBIDE

The sale and purchase of calcium carbide in this country will, under
existing conditions, usually be conducted in conformity with the set of
regulations issued by the British Acetylene Association, of which a copy,
revised to date, is given below:

"REGULATIONS AS TO CARBIDE OF CALCIUM."

1. The carbide shall be guaranteed by the seller to yield, when broken to
standard size, i.e., in lumps varying from 1 to 2-1/2 inches or larger, not less
than 4.8 cubic feet per lb., at a barometric pressure of 30 inches and
temperature of 60° Fahr. (15.55° Centigrade). The actual gas yield shall be
deemed to be the gas yield ascertained by the analyst, plus 5 per cent.

"Carbide yielding less than 4.8 cubic feet in the sizes given above shall be
paid for in proportion to the gas yield, i.e., the price to be paid shall bear the
same relation to the contract price as the gas yield bears to 4.8 cubic feet
per lb.

"2. The customer shall have the right to refuse to take carbide yielding in
the sizes mentioned above less than 4.2 cubic foot, per lb., and it shall lie, in
case of refusal and as from the date of the result, of the analysis being made
known to either party, at the risk and expense of the seller.

"3. The carbide shall not contain higher figures of impurities than shall from
time to time be fixed by the Association.

"4. No guarantee shall be given for lots of less than 3 cwt., or for carbide
crushed to smaller than the above sizes.

"5. In case of dispute as to quality, either the buyer or the seller shall have
the right to have one unopened drum per ton of carbide, or part of a ton,

Page 385

sent for examination to one of the analysts appointed by the Association,
and the result of the examination shall be held to apply to the whole of the
consignment to which the drum belonged. "6. A latitude of 5 per cent, shall
be allowed for analysis; consequently differences of 5 per cent. above or
below the yields mentioned in 1 and 2 shall not be taken into consideration.

"7. Should the yield of gas be less than 4.8 cubic feet less 5 per cent., the
carriage of the carbide to and from the place of analysis and the cost of the
analysis shall be paid for by the seller. Should the yield be more than 4.8
cubic feet less 5 per cent., the carriage and costs of analysis shall be borne
by the buyer, who, in addition, shall pay an increase of price for the carbide
proportionate to the gas yield above 4.8 cubic feet plus 5 per cent.

"8. Carbide of 1 inch mesh and above shall not contain more than 5 per
cent. of dust, such dust to be defined as carbide capable of passing through
a mesh of one-sixteenth of an inch.

"9. The seller shall not be responsible for deterioration of quality caused by
railway carriage in the United Kingdom, unless he has sold including
carriage to the destination indicated by the buyer.

"10. Carbide destined for export shall, in case the buyer desires to have it
tested, be sampled at the port of shipment, and the guarantee shall cease
after shipment.

"11. The analyst shall take a sample of not less than 1 lb. each from the top,
centre, and bottom of the drum. The carbide shall be carefully broken up
into small pieces, due care being taken to avoid exposure to the air as much
as possible, carefully screened and tested for gas yield by decomposing it in
water, previously thoroughly saturated by exposure to acetylene for a period
of not less than 48 hours.

"12. Carbide which, when properly decomposed, yields acetylene
containing from all phosphorus compounds therein more than .05 per cent.
by volume of phosphoretted hydrogen, may be refused by the buyer, and
any carbide found to contain more than this figure, with a latitude of .01 per
cent. for the analysis, shall lie at the risk and expense of the seller in the
manner described in paragraph 2.

Page 386

"The rules mentioned in paragraph 7 shall apply as regards the carriage and
costs of analysis; in other words, the buyer shall pay these costs if the figure
is below 0.05 per cent. plus 0.01 per cent., and the seller if the figure is
above 0.05 per cent. plus 0.01 per cent. "The sampling shall take place in
the manner prescribed in paragraphs 5 and 11, and the analytical
examination shall be effected in the manner prescribed by the Association
and obtainable upon application to the Secretary."

The following is a translation of the corresponding rules issued by the
German Acetylene Association (Der Deutsche Acetylenverein) in regard to
business dealings in calcium carbide, as put into force on April 1, 1909:

"REGULATIONS OF THE GERMAN ACETYLENE ASSOCIATION
FOR TRADE IN CARBIDE.

"Price.

"The price is to be fixed per 100 kilogrammes (= 220 lb.) net weight of
carbide in packages containing about 100 kilogrammes.

"By packages containing about 100 kilogrammes are meant packages
containing within 10 per cent. above or below that weight.

"The carbide shall be packed in gas- and water-tight vessels of sheet- iron
of the strength indicated in the prescriptions of the carrying companies.

"The prices for other descriptions of packing must be specially stated.

"Place of Delivery.

"For consignment for export, the last European shipping port shall be taken
as the place of delivery.

"Quality.

"Commercial carbide shall be of such quality that in the usual lumps of 15
to 80 mm. (about 3/5 to 3 inches) diameter it shall afford a yield of at least

Page 387

300 litres at 15° C. and 760 mm. pressure of crude acetylene per
kilogramme for each consignment (= 4.81 cubic feet at 60° F. and 30 inches
per lb.). A margin of 2 per cent. shall be allowed for the analysis. Carbide
which yields less than 300 litres per kilogramme, but not less than 270 litres
(= 4.33 cubic feet) of crude acetylene per kilogramme (with the above-
stated 2 per cent. margin for analysis) must be accepted by the buyer. The
latter, however, is entitled to make a proportionate deduction from the price
and also to deduct the increased freight charges to the destination or, if the
latter is not settled at the time when the transaction is completed, to the
place of delivery. Carbide which yields less than 270 litres of crude
acetylene per kilogramme need not be accepted.

"Carbide must not contain more than 5 per cent. of dust. By dust is to be
understood all which passes through a screen of 1 mm. (0.04 inch) square,
clear size of holes.

"Small carbide of from 4 to 15 mm. (= 1/6 to 3/5 inch) in size (and
intermediate sizes) must yield on the average for each delivery at least 270
litres at 15° C. and 760 mm. pressure of crude acetylene per kilogramme (=
4.33 cubic feet at 60° F. and 30 inches per lb.) A margin of 2 per cent. shall
be allowed for the analysis. Small carbide of from 4 to 15 mm. in size (and
intermediate sizes) which yields less than 270 litres but not less than 250
litres (= 4.01 cubic feet per lb.) of crude acetylene per kilogramme (with the
above-stated 2 per cent. margin for analysis) must be accepted by the buyer.
The latter, however, is entitled to make a proportionate deduction from the
price and also to deduct the increased freight charges to the destination or, if
the latter is not settled at the time when the transaction is completed, to the
place of delivery. Small carbide of from 4 to 15 mm. in size (and
intermediate sizes) which yields less than 250 litres per kilogramme need
not be accepted.

"Carbide shall only be considered fit for delivery if the proportion of
phosphoretted hydrogen in the crude acetylene does not amount to more
than 0.04 volume per cent. A margin of 0.01 volume per cent. shall be
allowed for the analysis for phosphoretted hydrogen. The whole of the
phosphorus compounds contained in the gas are to be calculated as
phosphoretted hydrogen.

Page 388

"Period for Complaints.

"An interval of four weeks from delivery shall be allowed for complaints
for consignments of 5000 kilogrammes (= 5 tons) and over, and an interval
of two weeks for smaller consignments. A complaint shall refer only to a
quantity of carbide remaining at the time of taking the sample.

"Determination of Quality.

"1. In case the parties do not agree that the consignee is to send to the
analyst for the determination of the quality one unopened and undamaged
drum when the consignment is less than 5000 kilogrammes, and two such
drums when it is over 5000 kilogrammes, a sample for the purpose of
testing the quality is to be taken in the following manner:

"A sample having a total weight of at least 2 kilogrammes (= 4.4 lb.) is to
be taken. If the delivery to be tested does not comprise more than ten
drums, the sample is to be taken from an unopened and undamaged drum
selected at random. With deliveries of more than ten drums, the sample is to
be drawn from not fewer than 10 per cent, of the lot, and from each of the
unopened and undamaged drums drawn for the purpose not less than 1
kilogramme (= 2.2 lb.) is to be taken.

"The sampling is to be carried out by a trustworthy person appointed by the
two parties, or by one of the experts regularly recognised by the German
Acetylene Association, thus: Each selected drum, before opening, is to be
turned over twice (to got rid of any local accumulation of dust) and the
requisite quantity is to he withdrawn with a shovel (not with the hand) from
any part of it. These samples are immediately shot into one or more vessels
which are closed air- and water-tight. The lid is secured by a seal. No other
description of package, such as cardboard cases, boxes, &c., is permissible.

"If there is disagreement as to the choice of a trustworthy person, each of
the two parties is to take the required quantity, as specified above.

"2. The yield of gas and the proportion of phosphoretted hydrogen
contained in it are to be determined by the methods prescribed by the
German Acetylene Association. If there are different analyses giving non-

Page 389

concordant results, an analysis is to be made by the German Acetylene
Association, which shall be accepted as final and binding.

"In cases, however, where the first analysis has been made in the
Laboratory of the German Acetylene Association and arbitration is required,
the decisive analysis shall be made by the Austrian Acetylene Association.
If one of the parties prevents the arbitrator's analysis being carried out, the
analysis of the other party shall be absolutely binding on him.

"3. The whole of the cost of sampling and analysis is to be borne by the
party in the wrong."

The corresponding regulations issued by the Austrian Acetylene Association
(Der Oesterreichische Acetylenverein) are almost identical with those of the
German Association. They contain, however, provisions that the price is to
include packing, that the carbide must not be delivered in lumps larger than
the fist, that the sample may be sealed in a glass vessel with well-ground
glass stopper, that the sample is to be transmitted to the testing laboratory
with particulars of the size of the lots and the number of drums drawn for
sampling, and that the whole of it is to be gasified in lots of upwards of 1
kilogramme (= 2.2 lb.) apiece.

In Italy, it is enacted by the Board of Agriculture, Commerce and Industry
that by calcium carbide is to be understood for legal purposes also any other
carbide, or carbide-containing mixture, which evolves acetylene by
interaction with water. Also that only calcium carbide, which on admixture
with water yields acetylene containing less than 1 per cent. of its volume of
sulphuretted hydrogen and phosphoretted hydrogen taken together, may be
put on the market.

It is evident from the regulations quoted that the determination of the
volume of gas which a particular sample of calcium carbide is capable of
yielding, when a given weight of it is decomposed under the most
favourable conditions, is a matter of the utmost practical importance to all
interested in the trafficking of carbide, i.e., to the makers, vendors, brokers,
and purchasers of that material, as well as to all makers and users of
acetylene generating plant. The regulations of the British Association do

Page 390

not, however, give details of the method which the analyst should pursue in
determining the yield of acetylene; and while this may to a certain extent be
advantageously left to the discretion of the competent analyst, it is desirable
that the results of the experience already won by those who have had
special opportunities for practising this branch of analytical work should be
embodied in a set of directions for the analysis of carbide, which may be
followed in all ordinary analyses of that material. By the adoption of such a
set of directions as a provisional standard method, disputes as to the
quantity of carbide will be avoided, while it will still be open to the
competent analyst to modify the method of procedure to meet the
requirements of special cases. It would certainly be unadvisable in the
present state of our analytical methods to accept any hard and fast of rules
for analysis for determining the quality of carbide, but it is nevertheless
well to have the best of existing methods codified for the guidance of
analysts. The substance of the directions issued by the German Association
(Der Deutsche Acetylenverein) is reproduced below.

"METHODS FOR THE DETERMINATION OF TILE YIELD OF GAS
FROM CALCIUM CARBIDE.

"The greatest precision is attained when the whole of the sample submitted
to the analyst is gasified in a carbide-to-water apparatus, and the gas
evolved is measured in an accurately graduated gasholder.

"The apparatus used for this analysis must not only admit of all the
precautionary rules of gas-analytical work being observed, but must also
fulfil certain other experimental conditions incidental to the nature of the
analysis.

"(a) The apparatus must be provided with an accurate thermometer to show
the temperature of the confining water, and with a pressure gauge, which is
in communication with the gasholder.

"(b) The generator must either be provided with a gasholder which is
capable of receiving the quantity of gas evolved from the whole amount of
carbide, or the apparatus must be so constructed that it becomes possible
with a gasholder which in not too large (up to 200 litres = say 7 cubic feet
capacity) to gasify a larger amount of carbide.

Page 391

"(c) The generator must be constructed so that escape of the evolved gas
from it to the outer air is completely avoided.

"(d) The gasholder must be graduated in parts up to 1/4 per cent. of its
capacity, must travel easily, and be kept, as far as may be in suspension by
counterweighting.

"(e) The water used for decomposing the carbide and the confining water
must be saturated, before use, with acetylene, and, further, the generator
must, before the analysis proper, be put under the pressure of the confining
(or sealing) liquid."

The following is a description of a typical form of apparatus corresponding
with the foregoing requirements:

"The apparatus, shown in the annexed figure, consists of the generator A,
the washer B, and the gasholder C.

"The generator A consists of a cylindrical vessel with sloping bottom,
provided with a sludge outlet a, a gas exit-pipe b, and a lid b' fastened by
screws. In the upper part ten boxes c are installed for the purpose of
receiving the carbide. The bottoms of those boxes are flaps which rest
through their wire projections on a revolvable disc d, which is mounted on a
shaft l. This shaft passes through a stuffing-box to the outside of the
generator and can be rotated by moans of the chains f, the pulleys g and h,
and the winch i. Its rotation causes rotation of the disc d. The disc d, on
which the bottoms of the carbide- holders are supported, is provided with a
slot e. On rotating the disc, on which the supporting wires of the bottoms of
the carbide-holders rest, the slot is brought beneath these wires in
succession; and the bottoms, being thus deprived of their support, drop

Page 392

down. It is possible in this way to effect the discharge of the several
carbide-holders by gradual turning of the winch i.

"The washer B is provided with a thermometer m passing through a sound
stuffing-box and extending into the water.

"The gasholder C is provided with a scale and pointer, which indicate how
much gas there is in it. It is connected with the pressure-gauge n, and is
further provided with a control thermometer o. The gas exit-pipe q can be
shut off by a cock. There is a cock between the gasholder and the washer
for isolating one from the other.

"The dimensions of the apparatus are such that each carbide-holder can
contain readily about half a kilogramme (say l lb.) of carbide. The gasholder
is of about 200 litres (say 7 cubic feet) capacity; and if the bell is 850 mm.
(= 33-1/2 inches) high, and 550 mm. (= 21-1/2 inches) in diameter it will
admit of the position being read off to within half a litre (say 0.02 cubic
foot)."

The directions of the German Association for sampling a consignment of
carbide packed in drums each containing 100 kilogrammes (say 2 cwt.)
have already been given in the rules of that body. They differ somewhat
from those issued by the British Association (vide ante), and have evidently
been compiled with a view to the systematic and rapid sampling of larger
consignments than are commonly dealt with in this country. Drawing a
portion of the whole sample from every tenth drum is substantially the same
as the British Association's regulations for cases of dispute, viz., to have one
unopened drum (i.e., one or two cwt.) per ton of carbide placed at the
analyst's disposal for sampling. Actually the mode of drawing a portion of
the whole sample from every tenth vessel, or lot, where a large number is
concerned, is one which would naturally be adopted by analysts accustomed
to sampling any other products so packed or stored, and there in no reason
why it should be departed from in the case of large consignments of
carbide. For lots of less than ten drums, unless there is reason to suspect
want of uniformity, it should usually suffice to draw the sample from one
drum selected at random by the sampler. The analyst, or person who
undertakes the sampling, must, however, exercise discretion as to the
scheme of sampling to be followed, especially if want of uniformity of the

Page 393

several lots constituting the consignment in suspected. The size of the
lumps constituting a sample will be referred to later.

The British Association's regulations lead to a sample weighing about 3 lb.
being obtained from each drum. If only one drum is sampled, the quantity
taken from each position may be increased with advantage so as to give a
sample weighing about 10 lb., while if a large number of drums is sampled,
the several samples should be well mixed, and the ordinary method of
quartering and re-mixing followed until a representative portion weighing
about 10 lb. remains.

A sample representative of the bulk of the consignment having been
obtained, and hermetically sealed, the procedure of testing by means of the
apparatus already described may be given from the German Association's
directions:

"The first carbide receptacle is filled with 300 to 400 grammes (say 3/4 lb.)
of any readily decomposable carbide, and is hung up in the apparatus in
such a position with regard to the slot e on the disc d that it will be the first
receptacle to be discharged when the winch i is turned. The tin or bottle
containing the sample for analysis is then opened and weighed on a balance
capable of weighing exactly to 1/2 gramme (say 10 grains). The carbide in
it is then distributed quickly, and as far as may be equally, into the nine
remaining carbide receptacles, which are then shut and hung up quickly in
the generator. The lid b' is then screwed on the generator to close it, and the
empty tin or bottle, from which the sample of carbide has been removed, is
weighed.

"The contents of the first carbide receptacle are then discharged by turning
the winch i. Their decomposition ensures on the one hand that the sealing
water and the generating water are saturated with acetylene, and on the
other hand that the dead space in the generator is brought under the pressure
of the seal, so that troublesome corrections which would otherwise be
entailed are avoided. After the carbide is completely decomposed, but not
before two hours at least have elapsed, the cock p is shut, and the gasholder
is run down to the zero mark by opening the cock q. The cock q is then
shut, p is opened, and the analytical examination proper is begun by
discharging the several carbide receptacles by turning the winch i. After the

Page 394

first receptacle has been discharged, five or ten minutes are allowed to
elapse for the main evolution of gas to occur, and the cock p is then shut.
Weights are added to the gasholder until the manometer n gives the zero
reading; the position of the gasholder C is then read off, and readings of the
barometer and of the thermometer o are made. The gasholder is then
emptied down to the zero mark by closing the cock p and opening q. When
this is done q is closed and p is opened, and the winch i is turned until the
contents of the next carbide receptacle are discharged. This procedure is
followed until the carbide from the last receptacle has been gasified; then,
after waiting until all the carbide has been decomposed, but in any case not
less than two hours, the position of the gasholder is read, and readings of
the barometer and thermometer are again taken. The total of the values
obtained represents the yield of gas from the sample examined."

The following example is quoted:

Weight of the tin received, with its contained |
carbide . . . . . ._| = 6325
grammes.
Weight of the empty tin . . . . = 1485 "
_______
Carbide used . . . = 4840 " =
10670 lb.

The carbide in question was distributed among the nine receptacles and
gasified. The readings were:

________________________________________________
| | | | |
| No. | Litres. | Degrees C. | Millimetres. |
|______|__________|______________|_______________|
| | | | |
| 1 | 152.5 | 13 | 762 |
| 2 | 136.6 | " | " |
| 3 | 138.5 | " | " |
| 4 | 161.0 | " | " |
| 5 | 131.0 | " | " |
| 6 | 182.5 | 13.5 | " |
| 7 | 146.0 | " | " |
| 8 | 163.0 | 14.0 | " |

Page 395

| 9 | 178.5 | " | " |
|______|__________|______________|_______________|

After two hours, the total of the readings was 1395.0 litres at 13.5° C. and
762 mm., which is equivalent to 1403.7 litres (= 49.57 cubic feet) at 15° C.
and 760 mm. (or 60° F. and 30 inches; there is no appreciable change of
volume of a gas when the conditions under which it is measured are altered
from 15° C. and 760 mm. to 60° F. and 30 inches, or vice versâ).

The yield of gas from this sample is therefore 1403.7/4.840 = 290 litres at
15° C. and 760 mm. per kilogramme, or 49.57/10.67 = 4.65 cubic feet at
60° F. and 30 inches per pound of carbide. The apparatus described can, of
course, be used when smaller samples of carbide only are available for
gasification, but the results will be less trustworthy if much smaller
quantities than those named are taken for the test.

Other forms of carbide-to-water apparatus may of course be devised, which
will equally well fulfil the requisite conditions for the test, viz., complete
decomposition of the whole of the carbide without excessive rise of
temperature, and no loss of gas by solution or otherwise.

An experimental wet gas-motor, of which the water-line has been accurately
set (by means of the Gas Referees' 1/12 cubic foot measure, or a similar
meter-proving apparatus), may be used in place of the graduated gasholder
for measuring the volume of the gas evolved, provided the rate of flow of
the gas does not exceed 1/6 cubic foot, or say 5 litres per minute. If the
generation of gas is irregular, as when an apparatus of the type described
above is used, it is advisable to insert a small gasholder or large bell-
governor between the washer and the meter. The meter must be provided
with a thermometer, according to the indications of which the observed
volumes must be corrected to the corresponding volume at normal
temperature.

If apparatus such as that described above is not available, fairly trustworthy
results for practical purposes may be obtained by the decomposition of
smaller samples in the manner described below, provided these samples are
representative of the average composition of the larger sample or bulk, and
a number of tests are made in succession and the results of individual tests

Page 396

do not differ by more than 10 litres of gas per kilogramme (or 0.16 cubic
foot per pound) of carbide.

It is necessary at the outset to reduce large lumps of carbide in the sample to
small pieces, and this must be done with as little exposure as possible to the
(moist) air. Failing a good pulverising machine of the coffee-mill or similar
type, which does its work quickly, the lumps must be broken as rapidly as
possible in a dry iron mortar, which may with advantage be fitted with a
leather or india-rubber cover, through a hole in which the pestle passes. As
little actual dust as possible should be made during pulverisation. The
decomposition of the carbide is best effected by dropping it into water and
measuring the volume of gas evolved with the precautions usually practised
in gas analysis. An example of one of the methods of procedure described
by the German Association will show how this test can be satisfactorily
carried out:

"A Woulff's bottle, a in the annexed figure, of blown glass and holding
about 1/4 litre is used as the generating vessel. One neck, about 15 mm. in
internal diameter, is connected by flexible tubing with a globular vessel b,
having two tubulures, and this vessel is further connected with a conical
flask c, holding about 100 c.c. The other neck is provided with tubing d,
serving to convey the gas to the inlet-tube, with tap e, of the 20-litre
measuring vessel f, which is filled with water saturated with acetylene, and
communicates through its lower tubulure with a similar large vessel g. The
generating vessel a is charged with about 150 c.c. of water saturated with
acetylene. The vessel f is filled up to the zero mark by raising the vessel g;
the tap e is then shut, and connexion is made with the tube d. Fifty grammes
(or say 2 oz.) of the pulverised carbide are then weighed into the flask c and
this is connected by the flexible tubing with the vessel b. The carbide is
then decomposed by bringing it in small portions at a time into the bulb b
by raising the flask c, and letting it drop from b into the generating vessel a,
after having opened the cock e and slightly raised the vessel f. After the last
of the carbide has been introduced two hours are allowed to elapse, and the
volume of gas in f is then read while the water stands at the same level in f
and g, the temperature and pressure being noted simultaneously."

Page 397

A second, but less commendable method of decomposing the carbide is by
putting it in a dry two-necked bottle, one neck of which is connected with e,
and dropping water very slowly from a tap-funnel, which enters the other
neck, on to the carbide. The generating bottle should be stood in water, in
order to keep it cool, and the water should be dropped in at the rate of about
50 c.c. in one hour. It will take about three hours completely to gasify the
50 grammes of carbide under these conditions. The gas is measured as
before.

Cedercreutz has carried out trials to show the difference between the yields
found from large and small carbide taken from the same drum. One sample
consisted of the dust and smalls up to about 3/5 inch in size, while the other
contained large carbide as well as the small. The latter sample was broken
to the same size as the former for the analysis. Tests were made both with a
large testing apparatus, such as that shown in Fig. 22, and with a small
laboratory apparatus, such as that shown in Fig. 23. The dust was screened
off for the tests made in the large apparatus. Two sets of testings were made
on different lots of carbide, distinguished below as "A" and "B," and about
80 grammes wore taken for each determination in the laboratory apparatus,
and 500 grammes in the large apparatus. The results are stated in litres (at
normal temperature and pressure) per kilogramme of carbide.

_______________________________________________________________
____
| | |
|
| | "A" |
"B" |
|_____________________________________________________|______|_
_____|
| | |
|
| Lot

Page 398

|Litres|Litres|
| Small carbide, unscreened, in laboratory \ (1) | 276 |
267 |
| apparatus . . . . . / (2) | 273 |
270 |
| Average sample of carbide, unscreened, in \ (1) | 318 |
321 |
| laboratory apparatus . . . / (2) | 320 |
321 |
| Small carbide, dust freed, in large apparatus (1) | 288 |
274 |
| Average sample of carbide, dust freed, in \ (2) | 320 |
322 |
| large apparatus . . . . / | |
|
|_____________________________________________________|______|_
_____|

As the result of the foregoing researches Cedercreutz has recommended that
in order to sample the contents of a drum, they should be tipped out, and
about a kilogramme (say 2 to 3 lb.) taken at once from them with a shovel,
put on an iron base and broken with a hammer to pieces of about 2/5 inch,
mixed, and the 500 grammes required for the analysis in the form of testing
plant which he employs taken from this sample. Obviously a larger sample
can be taken in the same manner. On the other hand the British and German
Associations' directions for sampling the contents of a drum, which have
already been quoted, differ somewhat from the above, and must generally
be followed in cases of dispute.

Cedercreutz's figures, given in the above table, show that it would be very
unfair to determine the gas-making capacity of a given parcel of carbide in
which the lumps happened to vary considerably in size by analysing only
the smalls, results so obtained being possibly 15 per cent. too low. This is
due to two causes: first, however carefully it be stored, carbide deteriorates
somewhat by the attack of atmospheric moisture; and since the superficies
of a lump (where the attack occurs) is larger in proportion to the weight of
the lump as the lump itself is smaller, small lumps deteriorate more on
keeping than large ones. The second reason, however, is more important.
Not being a pure chemical substance, the commercial material calcium
carbide varies in hardness; and when it is merely crushed (not reduced
altogether to powder) the softer portions tend to fall into smaller fragments

Page 399

than the hard portions. As the hard portions are different in composition
from the soft portions, if a parcel is sampled by taking only the smalls,
practically that sample contains an excess of the softer part of the original
material, and as such is not representative. Originally the German Acetylene
Association did not lay down any rules as to the crushing of samples by the
analyst, but subsequently they specified that the material should be tested in
the size (or sizes) in which it was received. The British Association, on the
contrary, requires the sample to be broken in small pieces. If the original
sample is taken in such fashion as to include large and small lumps as
accurately as possible in the same proportion as that in which they occur in
the main parcel, no error will be introduced if that sample is crushed to a
uniform size, and then subdivided again; but a small deficiency in gas yield
will be produced, which will be in the consumer's favour. It is not altogether
easy to see the advantage of the British idea of crushing the sample over the
German plan of leaving it alone; because the analytical generator will easily
take, or its parts could be modified to take, the largest lumps met with. If
the sample is in very large masses, and is decomposed too quickly,
polymerisation of gas may be set up; but on the other hand, the crushing
and re-sampling will cause wastage, especially in damp weather, or when
the sampling has to be done in inconvenient places. The British Association
requires the test to be made on carbide parcels ranging between 1 and 2-1/2
inches or larger, because that is the "standard" size for this country, and
because no guarantee is to be had or expected from the makers as to the
gas-producing capacity of smaller material. Manifestly, if a consumer
employs such a form of generator that he is obliged to use carbide below
"standard" size, analyses may be made on his behalf in the ordinary way;
but he will have no redress if the yield of acetylene is less than the normal.
This may appear a defect or grievance; but since in many ways the use of
small carbide (except in portable lamps) is not advantageous--either
technically or pecuniarily--the rule simply amounts to an additional
judicious incentive to the adoption of apparatus capable of decomposing
standard-sized lumps. The German and Austrian Associations' regulations,
however, provide a standard for the quality of granulated carbide.

It has been pointed out that the German Association's direction that the
water used in the testing should be saturated with acetylene by a
preliminary decomposition of 1/2 kilogramme of carbide is not wholly

Page 400

adequate, and it has been suggested that the preliminary decomposition
should be carried out twice with charges of carbide, each weighing not less
than 1 per cent. of the weight of water used. A further possible source of
error lies in the fact that the generating water is saturated at the prevailing
temperature of the room, and liberates some of its dissolved acetylene when
the temperature rises during the subsequent generation of gas. This error, of
course, makes the yield from the sample appear higher than it actually is. Its
effects may be compensated by allowing time for the water in the generator
or gasholder to cool to its original temperature before the final reading is
made.

With regard to the measurement of the temperature of the evolved gas in the
bell gasholder, it is usual to assume that the reading of a thermometer which
passes through the crown of the gasholder suffices. If the thermometer has a
very long stem, so that the bulb is at about the mid-height of the filled bell,
this plan is satisfactory, but if an ordinary thermometer is used, it is better to
take, as the average temperature of the gas in the holder, the mean of the
readings of the thermometer in the crown, and of one dipping into the water
of the holder seal.

The following table gives factors for correcting volumes of gas observed at
any temperature and pressure falling within its range to the normal
temperature (60° F.) and normal barometric height (30 inches). The normal
volume thus found is, as already stated, not appreciably different from the
volume at 15° C. and 760 mm. (the normal conditions adopted by
Continental gas chemists). To use the table, find the observed temperature
and the observed reading of the barometer in the border of the table, and in
the space where these vertical and horizontal columns meet will be found a
number by which the observed volume of gas is to be multiplied in order to
find the corresponding volume under normal conditions. For intermediate
temperatures, &c., the factors may be readily inferred from the table by
inspection. This table must only be applied when the gas is saturated with
aqueous vapour, as is ordinarily the case, and therefore a drier must not be
applied to the gas before measurement.

Hammerschmidt has calculated a similar table for the correction of volumes
of gas measured at temperatures ranging from 0° to 30° C., and under

Page 401

pressures from 660 to 780 mm., to 15° C. and 760 mm. It is based on the
coefficient of expansion of acetylene given in Chapter VI., but, as was there
pointed out, this coefficient differs by so little from that of the permanent
gases for which the annexed table was compiled, that no appreciable error
results from the use of the latter for acetylene also. A table similar to the
annexed but of more extended range is given in the "Notification of the Gas
Referees," and in the text-book on "Gas Manufacture" by one of the
authors.

The determination of the amounts of other gases in crude or purified
acetylene is for the most part carried out by the methods in vogue for the
analysis of coal-gas and other illuminating gases, or by slight modifications
of them. For an account of these methods the textbook on "Gas
Manufacture" by one of the authors may be consulted. For instance, two of
the three principal impurities in acetylene, viz., ammonia and sulphuretted
hydrogen, may be detected and estimated in that gas in the same manner as
in coal gas. The detection and estimation of phosphine are, however,
analytical operations peculiar to acetylene among common illuminating
gases, and they must therefore be referred to.

Table to facilitate the Correction of the Volume of Gas at different
Temperatures and under different Atmospheric Pressures.

_____________________________________________________
| | |
| | THERMOMETER. |
| BAR.|_______________________________________________|
| | | | | | | |
| | 46° | 48° | 50° | 52° | 54° | 56° |
|_____|_______|_______|_______|_______|_______|_______|
| | | | | | | |
|28.4 | 0.979 | 0.974 | 0.970 | 0.965 | 0.960 | 0.955 |
|28.5 | 0.983 | 0.978 | 0.973 | 0.968 | 0.964 | 0.959 |
|28.6 | 0.986 | 0.981 | 0.977 | 0.972 | 0.967 | 0.962 |
|28.7 | 0.990 | 0.985 | 0.980 | 0.975 | 0.970 | 0.966 |
|28.8 | 0.993 | 0.988 | 0.984 | 0.979 | 0.974 | 0.969 |
|28.9 | 0.997 | 0.992 | 0.987 | 0.982 | 0.977 | 0.973 |
|29.0 | 1.000 | 0.995 | 0.990 | 0.986 | 0.981 | 0.976 |
|29.1 | 1.004 | 0.999 | 0.994 | 0.989 | 0.984 | 0.979 |
|29.2 | 1.007 | 1.002 | 0.997 | 0.992 | 0.988 | 0.982 |
|29.3 | 1.011 | 1.005 | 1.001 | 0.996 | 0.991 | 0.986 |

Page 402

|29.4 | 1.014 | 1.009 | 1.004 | 0.999 | 0.995 | 0.990 |
|29.5 | 1.018 | 1.013 | 1.008 | 1.003 | 0.998 | 0.993 |
|29.6 | 1.021 | 1.016 | 1.011 | 1.006 | 1.001 | 0.996 |
|29.7 | 1.025 | 1.019 | 1.015 | 1.010 | 1.005 | 1.000 |
|29.8 | 1.028 | 1.023 | 1.018 | 1.013 | 1.008 | 1.003 |
|29.9 | 1.031 | 1.026 | 1.022 | 1.017 | 1.012 | 1.007 |
|30.0 | 1.035 | 1.030 | 1.025 | 1.020 | 1.015 | 1.010 |
|30.1 | 1.038 | 1.033 | 1.029 | 1.024 | 1.019 | 1.014 |
|30.2 | 1.042 | 1.037 | 1.032 | 1.027 | 1.022 | 1.017 |
|30.3 | 1.045 | 1.040 | 1.036 | 1.030 | 1.025 | 1.020 |
|30.4 | 1.049 | 1.044 | 1.039 | 1.034 | 1.029 | 1.024 |
|30.5 | 1.052 | 1.047 | 1.042 | 1.037 | 1.032 | 1.027 |
|_____|_______|_______|_______|_______|_______|_______|
_____________________________________________________
| | |
| | THERMOMETER. |
| BAR.|_______________________________________________|
| | | | | | | |
| | 58° | 60° | 62° | 64° | 66° | 68° |
|_____|_______|_______|_______|_______|_______|_______|
| | | | | | | |
|28.5 | 0.954 | 0.949 | 0.944 | 0.939 | 0.934 | 0.929 |
|28.6 | 0.958 | 0.953 | 0.947 | 0.943 | 0.938 | 0.932 |
|28.7 | 0.961 | 0.956 | 0.951 | 0.946 | 0.941 | 0.936 |
|28.8 | 0.964 | 0.959 | 0.954 | 0.949 | 0.944 | 0.939 |
|28.9 | 0.968 | 0.963 | 0.958 | 0.953 | 0.948 | 0.942 |
|29.0 | 0.971 | 0.966 | 0.961 | 0.956 | 0.951 | 0.946 |
|29.1 | 0.975 | 0.969 | 0.964 | 0.959 | 0.954 | 0.949 |
|29.2 | 0.978 | 0.973 | 0.968 | 0.963 | 0.958 | 0.952 |
|29.3 | 0.981 | 0.976 | 0.971 | 0.966 | 0.961 | 0.956 |
|29.4 | 0.985 | 0.980 | 0.975 | 0.969 | 0.964 | 0.959 |
|29.5 | 0.988 | 0.983 | 0.978 | 0.973 | 0.968 | 0.962 |
|29.6 | 0.992 | 0.986 | 0.981 | 0.976 | 0.971 | 0.966 |
|29.7 | 0.995 | 0.990 | 0.985 | 0.980 | 0.974 | 0.969 |
|29.8 | 0.998 | 0.993 | 0.988 | 0.983 | 0.978 | 0.972 |
|29.9 | 1.002 | 0.997 | 0.991 | 0.986 | 0.981 | 0.976 |
|30.0 | 1.005 | 1.000 | 0.995 | 0.990 | 0.985 | 0.979 |
|30.1 | 1.009 | 1.003 | 0.998 | 0.993 | 0.988 | 0.983 |
|30.2 | 1.012 | 1.007 | 1.002 | 0.996 | 0.991 | 0.986 |
|30.3 | 1.015 | 1.010 | 1.005 | 1.000 | 0.995 | 0.989 |
|30.4 | 1.019 | 1.014 | 1.008 | 1.003 | 0.998 | 0.993 |
|30.5 | 1.022 | 1.017 | 1.012 | 1.006 | 1.001 | 0.996 |
|_____|_______|_______|_______|_______|_______|_______|
_____________________________________________
| | |
| | THERMOMETER. |
| BAR.|_______________________________________|
| | | | | | |

Page 403

| | 70° | 72° | 74° | 76° | 78° |
|_____|_______|_______|_______|_______|_______|
| | | | | | |
|28.4 | 0.921 | 0.915 | 0.910 | 0.905 | 0.900 |
|28.5 | 0.924 | 0.919 | 0.914 | 0.908 | 0.903 |
|28.6 | 0.927 | 0.922 | 0.917 | 0.912 | 0.906 |
|28.7 | 0.931 | 0.925 | 0.920 | 0.915 | 0.909 |
|28.8 | 0.934 | 0.929 | 0.924 | 0.918 | 0.913 |
|28.9 | 0.937 | 0.932 | 0.927 | 0.921 | 0.916 |
|29.0 | 0.941 | 0.935 | 0.930 | 0.925 | 0.919 |
|29.1 | 0.944 | 0.939 | 0.933 | 0.928 | 0.923 |
|29.2 | 0.947 | 0.942 | 0.937 | 0.931 | 0.926 |
|29.3 | 0.950 | 0.945 | 0.940 | 0.935 | 0.929 |
|29.4 | 0.954 | 0.949 | 0.943 | 0.938 | 0.932 |
|29.5 | 0.957 | 0.952 | 0.947 | 0.941 | 0.936 |
|29.6 | 0.960 | 0.955 | 0.950 | 0.944 | 0.939 |
|29.7 | 0.964 | 0.959 | 0.953 | 0.948 | 0.942 |
|29.8 | 0.967 | 0.962 | 0.957 | 0.951 | 0.946 |
|29.9 | 0.970 | 0.965 | 0.960 | 0.954 | 0.949 |
|30.0 | 0.974 | 0.968 | 0.963 | 0.958 | 0.952 |
|30.1 | 0.977 | 0.972 | 0.966 | 0.961 | 0.955 |
|30.2 | 0.980 | 0.975 | 0.970 | 0.964 | 0.959 |
|30.3 | 0.984 | 0.978 | 0.973 | 0.968 | 0.962 |
|30.4 | 0.987 | 0.982 | 0.976 | 0.971 | 0.965 |
|30.5 | 0.990 | 0.985 | 0.980 | 0.974 | 0.969 |
|_____|_______|_______|_______|_______|_______|

For the detection of phosphine, Bergé's solution may be used. It is a
"solution of 8 to 10 parts of corrosive sublimate in 80 parts of water and 20
parts of 30 per cent. hydrochloric acid." It becomes cloudy when gas
containing phosphine is passed into it. It is, however, applied most
conveniently in the form of Keppeler's test-papers, which have been
described in Chapter V. Test-papers for phosphine, the active body in which
has not yet been divulged, have recently been produced for sale by F. B.
Gatehouse.

The estimation of phosphine will usually require to be carried out either (1)
on gas directly evolved from carbide in order to ascertain if the carbide in
question yields an excessive proportion of phosphine, or (2) upon acetylene
which is presumably purified, drawn either from the outlet of the purifier or
from the service-pipes, with the object of ascertaining whether an adequate
purification in regard to phosphine has been accomplished. In either case,
the method of estimation is the same, but in the first, acetylene should be

Page 404

specially generated from a small representative sample of the carbide and
led directly into the apparatus for the absorption of the phosphine. If the
acetylene passes into the ordinary gasholder, the amount of phosphine in
gas drawn off from the holder will vary from time to time according to the
temperature and the degree of saturation of the water in the holder-tank with
phosphine, as well as according to the amount of phosphine in the gas
generated at the time.

A method frequently employed for the determination of phosphine in
acetylene is one devised by Lunge and Cedercreutz. If the acetylene is to be
evolved from a sample of carbide in order to ascertain how much phosphine
the latter yields to the gas, about 50 to 70 grammes of the carbide, of the
size of peas, are brought into a half-litre flask, and a tap-funnel, with the
mouth of its stem contracted, is passed through a rubber plug fitting the
mouth of the flask. A glass tube passing through the plug serves to convey
the gas evolved to an absorption apparatus, which is charged with about 75
c.c. of a 2 to 3 per cent. solution of sodium hypochlorite. The absorption
apparatus may be a ten-bulbed absorption tube or any convenient form of
absorption bulbs which subject the gas to intimate contact with the solution.
If acetylene from a service-pipe is to be tested, it is led direct from the
nozzle of a gas- tap to the absorption tube, the outlet of which is connected
with an aspirator or the inlet of an experimental meter, by which the volume
of gas passed through the solution is measured. But if the generating flask is
employed, water is allowed to drop from the tap-funnel on to the carbide in
the flask at the rate of 6 to 7 drops a minute (the tap-funnel being filled up
from time to time), and all the carbide will thus be decomposed in 3 to 4
hours. The flask is then filled to the neck with water, and disconnected from
the absorption apparatus, through which a little air is then drawn. The
absorbing liquid is then poured, and washed out, into a beaker; hydrochloric
acid is added to it, and it is boiled in order to expel the liberated chlorine. It
is then usual to precipitate the sulphuric acid by adding solution of barium
chloride to the boiling liquid, allowing it to cool and settle, and then
filtering. The weight of barium sulphate obtained by ignition of the filter
and its contents, multiplied by 0.137, gives the amount of sulphur present in
the acetylene in the form of sulphuretted hydrogen. The filtrate and
washings from this precipitate are rendered slightly ammoniacal, and a
small excess of "magnesia mixture" is added; the whole is stirred, left to

Page 405

stand for 12 hours, filtered, the precipitate washed with water rendered
slightly ammoniacal, dried, ignited, and weighed. The weight so found
multiplied by 0.278 gives the weight of phosphorus in the form of
phosphine in the volume of gas passed through the absorbent liquid.

Objection may rightly be raised to the Lunge and Cedercreutz method of
estimating the phosphine in crude acetylene on the ground that explosions
are apt to occur when the gas is being passed into the hypochlorite solution.
Also it must be borne in mind that it aims at estimating only the phosphorus
which is contained in the gas in the form of phosphine, and that there may
also be present in the gas organic compounds of phosphorus which are not
decomposed by the hypochlorite. But when the acetylene is evolved from
the carbide in proper conditions for the avoidance of appreciable heating it
appears fairly well established that phosphorus compounds other than
phosphine exist in the gas only in practically negligible amount, unless the
carbide decomposed is of an abnormal character. Various methods of
burning the acetylene and estimating the phosphorus in the products of
combustion have, however been proposed for the purpose of determining
the total amount of phosphorus in acetylene. Some of them are applicable to
the simultaneous determination of the total sulphur in the acetylene, and in
this respect become akin to the Gas Referees' method for the determination
of the sulphur compounds in coal-gas.

Eitner and Keppeler have proposed to burn the acetylene on which the
estimation is to be made in a current of neat oxygen. But this procedure is
rather inconvenient, and by no means essential. Lidholm liberated acetylene
slowly from 10 grammes of carbide by immersing the carbide in absolute
alcohol and gradually adding water, while the gas mixed with a stream of
hydrogen leading to a burner within a flask. The flow of hydrogen was
reduced or cut off entirely while the acetylene was coming off freely, but
hydrogen was kept burning for ten minutes after the flame had ceased to be
luminous in order to ensure the burning of the last traces of acetylene. The
products of combustion were aspirated through a condenser and a washing
bottle, which at the close were rinsed out with warm solution of ammonia.
The whole of the liquid so obtained was concentrated by evaporation,
filtered in order to remove particles of soot or other extraneous matter, and

Page 406

acidified with nitric acid. The phosphoric acid was then precipitated by
addition of ammonium molybdate.

J. W. Gatehouse burns the acetylene in an ordinary acetylene burner of from
10 to 30 litres per hour capacity, and passes the products of combustion
through a spiral condensing tube through which water is dropped at the rate
of about 75 c.c. per hour, and collected in a beaker. The burner is placed in
a glass bell-shaped combustion chamber connected at the top through a
right-angled tube with the condenser, and closed below by a metal base
through which the burner is passed. The amount of gas burnt for one
determination is from 50 to 100 litres. When the gas is extinguished, the
volume consumed is noted, and after cooling, the combustion chamber and
condenser are washed out with the liquid collected in the beaker and finally
with distilled water, and the whole, amounting to about 400 c.c., is
neutralised with solution of caustic alkali (if decinormal alkali is used, the
total acidity of the liquid thus ascertained may be taken as a convenient
expression of the aggregate amount of the sulphuric, phosphoric and silicic
acids resulting from the combustion of the total corresponding impurities in
the gas), acidified with hydrochloric acid, and evaporated to dryness with
the addition towards the end of a few drops of nitric acid. The residue is
taken up in dilute hydrochloric acid; and silica filtered off and estimated if
desired. To the filtrate, ammonia and magnesia mixture are added, and the
magnesium pyrophosphate separated and weighed with the usual
precautions. Sulphuric acid may, if desired, be estimated in the filtrate, but
in that case care must be taken that the magnesia mixture used was free
from it.

Mauricheau-Beaupré has elaborated a volumetric method for the estimation
of the phosphine in crude acetylene depending on its decomposition by a
known volume of excess of centinormal solution of iodine, addition of
excess of standard solution of sodium thiosulphate, and titrating back with
decinormal solution of iodine with a few drops of starch solution as an
indicator. One c.c. of centinormal solution of iodine is equivalent to 0.0035
c.c. of phosphine. This method of estimation is quickly carried out and is
sufficiently accurate for most technical purposes.

Page 407

In carrying out these analytical operations many precautions have to be
taken with which the competent analyst is familiar, and they cannot be
given in detail in this work, which is primarily intended for ordinary users
of acetylene, and not for the guidance of analysts. It may, however, be
pointed out that many useful tests in connexion with acetylene supply can
be conducted by a trained analyst, which are not of a character to be
serviceable to the untrained experimentalist. Among such may be named the
detection of traces of phosphine in acetylene which has passed through a
purifier with a view to ascertaining if the purifying material is exhausted,
and the estimation of the amount of air or other diluents in stored acetylene
or acetylene generated in a particular manner. Advice on these points should
be sought from competent analysts, who will already have the requisite
information for the carrying out of any such tests, or know where it is to be
found. The analyses in question are not such as can be undertaken by
untrained persons. The text-book on "Gas Manufacture" by one of the
authors gives much information on the operations of gas analysis, and may
be consulted, along with Hempel's "Gas Analysis" and Winkler and Lunge's
"Technical Gas Analysis."

Page 408

APPENDIX
DESCRIPTIONS OF A NUMBER OF ACETYLENE GENERATORS AS
MADE IN THE YEAR 1909

(The purpose of this Appendix is explained in Chapter IV., page 111, and a
special index to it follows the general index at the end of this book.)

AMERICA--CANADA.

Maker: SICHE GAS CO., LTD., GEORGETOWN, ONTARIO.

Type: Automatic; carbide-to-water.

The "Siche" generator made by this firm consists of a water-tank A, having
at the bottom a sludge agitator N and draw-off faucet O, and rigidly secured
within it a bell-shaped generating chamber B, above which rises a barrel
containing the feed chamber C, surmounted by the carbide chamber D. The
carbide used is granulated or of uniform size. In the generating chamber B
is an annular float E, nearly filling the area of the chamber, and connected,
by two rods passing, with some lateral play, through apertures in the conical
bottom of the feed chamber C, to the T-shaped tubular valve F.
Consequently when the float shifts vertically or laterally the rods and valves
at once move with it. The angle of the cone of the feed chamber and the
curve of the tubular valve are based on the angle of rest of the size of
carbide used, with the object of securing sensitiveness of the feed. The feed
is thus operated by a very small movement of the float, and consequently
there is but very slight rise and fall of the water in the generating chamber.
Owing to the lateral play, the feed valve rarely becomes concentric with its
seat. There is a cover G over the feed valve F, designed to distribute the
carbide evenly about the feed aperture and to prevent it passing down the
hollow of the valve and the holes through which the connecting-rods pass.
It also directs the course of the evolved gas on its way to the service-pipe
through the carbide in the feed chamber C, whereby the gas is dried. The
carbide chamber D has at its bottom a conical valve, normally open, but

Page 409

closed by means of the spindle H, which is engaged at its upper end by the
closing screw-cap J, which is furnished with a safelocking device to prevent
its removal until the conical valve is closed and the hopper chamber D
thereby cut off from the gas-supply. The cap J, in addition to a leather
washer to make a gas-tight joint when down, has a lower part fitting to
make an almost gas-tight joint. Thus when the cap is off; the conical valve
fits gas-tight; when it is on and screwed down it is gas-tight; and when on
but not screwed down, it is almost gas-tight. Escape of gas is thus avoided.
A special charging funnel K, shown in half-scale, is provided for inserting
in place of the screw cap. The carbide falls from the funnel into the
chamber D when the chain is pulled. A fresh charge of carbide may be put
in while the apparatus is in action. The evolved gas goes into the chamber C
through a pipe, with cock, to a dust-arrester L, which contains a knitted
stocking lightly filled with raw sheep's wool through which the gas passes
to the service- pipe. The dust-arrester needs its contents renewing once in
one, two, or three years, according to the make of gas. The pressure of the
gas is varied as desired by altering the height of water in the tank A. When
cleaning the machine, the water must never be run below the top of the
generating chamber.

AMERICA--UNITED STATES.

Maker: J. B. COLT CO., 21 BARCLAY STREET, NEW YORK.

Type: Automatic; carbide-to-water.

Page 410

The "Colt" generator made by this firm comprises a carbide hopper
mounted above a generating tank containing water, and an equalising bell
gasholder mounted above a seal-pot having a vent-pipe C communicating
with the outer air. The carbide hopper is charged with 1/4 x 1/12 inch
carbide, which is delivered from it into the water in the generating tank in
small portions at a time through a double valve, which is actuated through
levers connected to the crown of the equalising gasholder. As the bell of the
gasholder falls the lever rotates a rock shaft, which enters the carbide
hopper, and through a rigidly attached lever raises the inner plunger of the
feed-valve. The inner plunger in turn raises the concentric outer stopper,
thereby leaving an annular space at the base of the carbide hopper, through
which a small delivery of carbide to the water in the generating tank then
ensues. The gas evolved follows the course shown by the arrows in the
figure into the gasholder, and raises the bell, thereby reversing the action of
the levers and allowing the valve to fall of its own weight and so cut off the
delivery of carbide. The outer stopper of the valve descends before the inner
plunger and so leaves the conical delivery mouth of the hopper free from
carbide. The inner plunger, which is capped at its lower end with rubber,
then falls and seats itself moisture-tight on the clear delivery mouth of the
hopper. The weight of the carbide in the hopper is taken by its sides and a
projecting flange of the valve casing, so that the pressure of the carbide at
the delivery point is slight and uniform. The outside of the delivery mouth
is finished by a drip collar with double lip to prevent condensed moisture
creeping upwards to the carbide in the hopper. A float in the generating
tank, by its descent when the water falls below a certain level, automatically
draws a cut off across the delivery mouth of the carbide hopper and so
prevents the delivery of carbide either automatically or by hand until the
water in the generating tank has been restored to its proper level.
Interlocking levers, (11) and (12) in the figure, prevent the opening of the
feed valve while the cap (10) of the carbide hopper is open for recharging
the hopper. There is a stirrer actuated by a handle (9) for preventing the
sludge choking the sludge cock. The gas passes into the gasholder through a
floating seal, which serves the dual purpose of washing it in the water of the
gasholder tank and of preventing the return of gas from the holder to the
generating tank. From the gasholder the gas passes to the filter (6) where it
traverses a strainer of closely woven cotton felt for the purpose of the
removal of any lime.

Page 411

Drip pipes (30) and (31) connected to the inlet- and outlet-pipes of the
gasholder are sealed in water to a depth of 6 inches, so that in the event of
the pressure in the generator or gasholder rising above that limit the surplus
gas blows through the seal and escapes through the vent-pipe C. There is
also a telescopic blow-off (32) and (33), which automatically comes into
play if the gasholder bell rises above a certain height.

Maker: DAVIS ACETYLENE CO., ELKHARDT, INDIANA.

Type: Automatic; carbide-to-water.

The "Davis" generator made by this firm comprises an equalising bell
gasholder with double walls, the inner wall surrounding a central tube rising
from the top of the generating chamber, in which is placed a water-sealed
carbide chamber with a rotatory feeding mechanism which is driven by a
weight motor. The carbide falls from the chamber on to a wide disc from
which it is pushed off a lump at a time by a swinging displacer, so arranged
that it will yield in every direction and prevent clogging of the feeding
mechanism. Carbide falls from the disk into the water of the generating
chamber, and the evolved gas raises the bell and so allows a weighted lever
to interrupt the action of the clockwork, until the bell again descends. The
gas passes through a washer in the gasholder tank, and then through an
outside scrubber to the service-pipe. There is an outside chamber connected
by a pipe with the generating chamber, which automatically prevents over-
filling with water, and also acts as a drainage chamber for the service- and
blow-off-pipes. There is an agitator for the residuum and a sludge-cock
through which to remove same. The feeding mechanism permits the
discharge of lump carbide, and the weight motor affords independent power
for feeding the carbide, at the same time indicating the amount of
unconsumed carbide and securing uniform gas pressure.

Page 412

Maker: SUNLIGHT GAS MACHINE CO., 49 WARREN STREET, NEW
YORK.

Type: Automatic; carbide-to-water.

The "Omega" apparatus made by this firm consists of a generating tank
containing water, and surmounted by a hopper which is filled with carbide
of 1/4-inch size. The carbide is fed from the hopper into the generating tank
through a mechanism consisting of a double oscillating cup so weighted
that normally the feed is closed. The fall of the bell of the equalising
gasholder, into which the gas evolved passes, operates a lever B, which
rotates the weighted cup in the neck of the hopper and so causes a portion
of carbide to fall into the water in the generating tank. The feed-cup consists
of an upper cup into which the carbide is first delivered. It is then tipped
from the upper cup into the lower cup while, at the same time, further
delivery from the hopper is prevented. Thus only the portion of carbide
which has been delivered into the lower cup is emptied at one discharge
into the generator. There is a safety lock to the hopper cap which prevents
the feeding mechanism coming into operation until the hopper cap is
screwed down tightly. Provision is made for a limited hand-feed of carbide
to start the apparatus. The gasholder is fitted with a telescoping vent-pipe,
by which gas escapes to the open in the event of the bell being raised above
a certain height. There is also an automatic cut-off of the carbide feed,
which comes into operation it the gas is withdrawn too rapidly whether
through leakage in the pipes or generating plant, or through the
consumption being increased above the normal generating capacity of the

Page 413

apparatus. The gas evolved passes into a condensing or washing chamber
placed beneath the gasholder tank and thence it travels to the gasholder.
From the gasholder it goes through a purifier containing "chemically treated
coke and cotton" to the supply-pipe.

1 Vent-cock handle. 2 Residuum-cock handle. 3 Agitator handle. 4 Filling
funnel. 5 Water overflow. 6 Hopper cap and lever. 7 Starting feed. 8 Rocker
arm. 9 Feed connecting-rod. A Pawl. B Lever for working feed mechanism.
C Guide frame. D Residuum draw-off cock. G Chain from hopper cap to
feed mechanism. H Blow-off and vent-pipe connexion. I Gas outlet from
generator. J Gas service-cock. K Filling funnel for gasholder tank. L Funnel
for condensing chamber. M Gas outlet at top of purifier. N Guides on gas-
bell. O Crosshead on swinging pawl. P Crane carrying pawl. Q Shaft
connecting feed mechanism. R Plug in gas outlet-pipe. S Guide-frame
supports. U Removable plate to clean purifier. Z Removable plate to expose
feed-cups for cleaning same.

AUSTRIA-HUNGARY

Maker: RICH. KLINGER, GUMPOLDSKIRCHEN, NEAR VIENNA.

Type: Non-automatic; carbide-to-water.

The generating plant made by this firm consists of the generator A which is
supported in a concrete water and sludge tank B, a storage gasholder J, and
purifiers K. In the top of the generator are guide-ways F, through each of
which is passed a plunger C containing a perforated cage charged with
about 8 lb. of lump carbide. The plungers are supported by ropes passing
over pulleys D, and when charged they are lowered through the guide-ways
F into the water in the tank B. The charge of carbide is thus plunged at once

Page 414

into the large body of water in the tank, and the gas evolved passes through
perforations in the washer G to the condenser H and thence to the storage
gasholder J. After exhaustion of the charge the plungers are withdrawn and
a freshly charged cage of carbide inserted ready for lowering into the
generating tank. There is a relief seal f through which gas will blow and
escape by a pipe g to the open should the pressure within the apparatus
exceed the depth of the seal, viz., about 9 inches. There is a syphon pot N
for the collection and withdrawal of condensed water. The sludge is allowed
to accumulate in the bottom of the concrete tank B until it becomes
necessary to remove it at intervals of about three months. Water is added to
the tank daily to replace that used up in the generation of the gas. The gas
passes from the storage holder through one of the pair of purifiers K, with
water-sealed lids, which are charged with a chemical preparation for the
removal of phosphoretted hydrogen. This purifying material also acts as a
desiccating agent. From the purifiers the gas passes through the meter L to
the service- pipes.

BELGIUM.

Maker: SOC. AN. DE L'ACÉTYLITHE, 65 RUE DU MARCHE,
BRUSSELS.

Type: Automatic; contact.

The generating apparatus made by this firm uses, instead of ordinary
carbide, a preparation known as "acétylithe," which is carbide treated
specially with mineral oil, glucose and sugar. The object of using this
treated carbide is to avoid the effects of the attack of atmospheric humidity
or water vapour, which, with ordinary carbide, give rise to the phenomena
of after-generation. The generator comprises a water-tank A with conical
base, a basket C containing the treated carbide inserted within a cylindrical
case B which is open at the bottom and is surmounted by a cylindrical filter
D. At starting, the tank A is filled with water to the level N N'. The water

Page 415

rises within the cylindrical case until it comes in contact with the treated
carbide, which thereupon begins to evolve gas. The gas passes through the
filter D, which is packed with dry cotton-wool, and escapes through the tap
M. As soon as the contained air has been displaced by gas the outlet of the
tap M is connected by a flexible tube to the pipe leading to a purifier and
the service-pipe. When the tap M is closed, or when the rate of evolution of
the gas exceeds the rate of consumption, the evolved gas accumulates
within the cylindrical case B and begins to displace the water, the level of
which within the case is lowered from S S', first to S1 S'1 and ultimately to,
say, S2 S'2. The evolution of gas is thereby gradually curtailed or stopped
until more is required for consumption. The water displacement causes the
water-level in the outer tank to rise to N1 N'1 and ultimately to, say N2 N'2.
The lime formed by the decomposition of the carbide is loosened from the
unattacked portion and taken more or less into solution as sucrate of lime,
which is a soluble salt which the glucose or sugar in the treated carbide
forms with lime. The solution is eventually run off through the cock R. The
cover T of the filter is screwed down on rubber packing until gas- tight. The
purifier is charged with puratylene or other purifying material.

Maker: L. DEBRUYNE, 22 PLACE MASUI, BRUSSELS.

Type: (1) Automatic; carbide-to-water.

The generating plant made by this firm, using granulated carbide, comprises
an equalising gasholder E alongside a generating tank B, which is
surmounted by a closed carbide receptacle A and a distributing appliance.

Page 416

The carbide receptacle is filled with granulated carbide and the lid N
screwed down; the carbide is then withdrawn from the base of the
receptacle by the distributing appliance and discharged in measured
quantities as required into the water in the generating tank. The distributing
appliance is actuated by a weighted cord H attached to the bell I of the
gasholder and discharges at each time a quantity of carbide only sufficient
nearly to fill the gasholder with acetylene. The gas passes from the
generator through the pipe J and seal-pot D, or bypass F, to the gasholder.
The generating tank is provided with a funnel G for replacing the water
consumed, a sludge-stirrer and a draw-off cock L, and a water-level cock C.
The gas passes from the gasholder through a purifier K, charged with
heratol, to the service-pipe.

(2) Automatic; carbide-to-water.

The "Debruyne" generator comprises an equalising bell gasholder A placed
alongside a generating tank B containing water into which lump carbide is
discharged as necessary from each in turn of a series of chambers mounted
in a ring above the generating tank. The chambers are removable for
refilling, and when charged are hermetically sealed until opened in turn
above the shoot C, through which their contents are discharged into the
generating tank. The carbide contained in each chamber yields sufficient
gas nearly to fill the gasholder. The discharging mechanism is operated
through an arm E attached to the bell G of the gasholder, which sets the
mechanism in motion when the bell has fallen nearly to its lowest position.
The lip L serves for renewing the water in the generator, and the gas
evolved goes through the pipe K with tap F to the gasholder. There is an
eccentric stirrer for the sludge and a large-bore cock for discharging it. The
gas passes from the gasholder through the pipe J to the purifier H, charged
with heratol, and thence to the service-pipe.

Page 417

Maker: DE SMET VAN OVERBERGE, ALOST.

Type: (1) Automatic; carbide-to-water.

This generating apparatus comprises an equalising gasholder A placed
alongside a generating tank B, above which is mounted on a rotating spindle
a series of chambers C, arranged in a circle, which are filled with carbide.
The generating tank is closed at the top, but on one side there is a shoot D
through which the carbide is discharged from the chambers in turn into the
water in the tank. The series of chambers are rotated by means of a cord
passing round a pulley E and having a weight F at one end, and being
attached to the bell of the gasholder at the other. When the bell falls, owing
to the consumption of gas, to a certain low position, the carbide chamber,
which has been brought by the rotation of the pulley over the shoot, is
opened at the bottom by the automatic liberation of a catch, and its contents
are discharged into the generating tank. The contents of one carbide
chamber suffice to fill the gasholder to two-thirds of its total capacity. The
carbide chambers after filling remain hermetically closed until the bottom is
opened for the discharge of the carbide. There is a sludge-cock G at the
bottom of the generating tank. The gas passes from the gasholder through a
purifier H, which is ordinarily charged with puratylene.

(2) Non-automatic; carbide-to-water. This apparatus comprises a storage
bell gasholder J placed alongside a generating tank in the top of which is a
funnel E with a counter-weighted lever pivoted on the arm B. The base of

Page 418

the funnel is closed by a flap valve C hinged at D. When it is desired to
generate gas the counter-weight A of the lever is raised and the valve at the
bottom of the funnel is thereby opened. A charge of carbide is then tipped
into the funnel and drops into the water in the generating tank. The valve is
then closed and the gas evolved goes through the pipe G to the gasholder,
whence it passes through a purifier to the service-pipe. There is a sludge-
cock on the generating tank.

Maker: SOC. AN. BELGE DE LA PHOTOLITHE, 2 RUE DE HUY,
LIÉGE.

Type: Automatic; carbide-to-water.

The "Photolithe" generating plant made by this firm comprises an
equalising bell gasholder A in the tank O, alongside a generating tank B
which is surmounted by a carbide storage receptacle divided into a number
of compartments. These compartments are fitted with flap bottoms secured
by catches, and are charged with carbide. Through the middle of the storage
receptacle passes a spindle, to the upper end of which is attached a pulley b.
Round the pulley passes a chain, one end of which carries a weight n, while
in the other direction it traverses guide pulleys and is attached to a loop on
the crown of the gasholder bell. When the bell falls below a certain point
owing to the consumption of gas, it pulls the chain and rotates the pulley b
and therewith an arm d, which liberates the catch supporting the flap-
bottom of the next in order of the carbide compartments. The contents of
this compartment are thereby discharged through the shoot C into the
generating tank B. The gas evolved passes through the cock R and the pipe
T into the gasholder, the rise of the bell of which takes the pull off the chain
and allows the weight at its other end to draw it up until it is arrested by the
stop f. The arm d is thereby brought into position to liberate the catch of the
next carbide receptacle. The generating tank is enlarged at its base to form a
sludge receptacle E, which is provided with a sludge draw-off cock S and a

Page 419

hand-hole P. Between the generating tank proper and the sludge receptacle
is a grid, which is cleaned by means of a rake with handle L. The gas passes
from the gasholder through a purifier H charged with puratylene, to the
service-pipe.

The same firm also makes a portable generating apparatus in which the
carbide is placed in a basket in the crown of the bell of the gasholder. This
apparatus is supplied on a trolley for use in autogenous soldering or
welding.

FRANCE.

Maker: LA SOC. DES APPLICATIONS DE L'ACÉTYLÈNE, 26 RUE
CADET, PARIS.

Type: Automatic; carbide-to-water.

The "Javal" generating plant made by this firm consists of an equalising bell
gasholder A in the tank B with a series of buckets D, with removable
bottoms h, mounted on a frame F round the guide framing of the holder.
Alongside the gasholder stands the generating tank H with shoot K, into
which the carbide discharged from the buckets falls. On top of the generator
is a tipping water-bucket I supplied with water through a ball cock. The bell
of the gasholder is connected by chains a and c, and levers b and d with an
arm which, when the bell descends to a certain point, comes in contact with
the catch by which the bottom of the carbide bucket is held in place, and,
liberating the same, allows the carbide to fall into the shoot. When the bell
rises, in consequence of the evolved gas, the ring of carbide buckets is
rotated sufficiently to bring the next bucket over the shoot. Thus the buckets
are discharged in turn as required through the rise and fall of the gasholder
bell.

Page 420

The carbide falling from the opened bucket strikes the end i of the lever k,
and thereby tips the water-bucket I and discharges its contents into the shoot
of the generator. The rise in the level of the water in the generator, due to
the discharge of the water from the bucket I, lifts the float L and therewith,
through the attached rod and chain u, the ball s of the valve t. The sludge,
which has accumulated in the base N of the generator from the
decomposition of the previous portion of carbide, is thereby discharged
automatically into a special drain. The discharge- valve closes automatically
when the float L has sunk to its original level. The gas evolved passes from
the generator through the seal-pot M and the pipe r with cock q into the
gasholder, from which it passes through the pipe x; with condensation
chamber and discharge tap y into the purifier R, which is charged with
heratol.

Maker: L'HERMITE, LOUVIERS, EURE.

Type: (1) Automatic; carbide-to-water.

The generating plant known as "L'Éclair," by this firm comprises an
equalising bell gasholder A floating in an annular water-seal N, formed in
the upper part of a generating tank B into which carbide enters through the
shoot K. Mounted at the side of the tank is the carbide delivery device,
which consists of the carbide containers J supported on an axis beneath the
water-sealed cover H. The containers are filled with ordinary lump carbide
when the cover H is removed. The tappet O attached to the bell of the
gasholder come in contact with a pawl when the gasholder bell descends to
a certain level and thereby rotates a pinion on the protruding end of the axis
which carries the carbide containers J. Each time the bell falls and the

Page 421

tappet strikes the pawl, one compartment of the carbide containers
discharges its contents down the shoot K into the generating tank B. The gas
evolved passes upwards and causes the bell A to rise. The gas is prevented
from rising into the shoot by the deflecting plates G. The natural level of the
water in the generating tank, when the apparatus is in use, is shown by the
dotted lines L. The lime sludge is discharged from time to time through the
cock E, being stirred up by means of the agitator C with handle D. When
the sludge is discharged water is added through M to the proper level. The
gas evolved passes from the holder through the pipe with tap F to the
service-pipe. A purifier is supplied if desired.

References

A Gasholder. B Generator. C Agitator. D Handle of agitator. E Sludge-cock.
F Gas outlet. G Deflecting plates. H Cover. I Carbide. J Automatic
distributor. K Shoot. L Water-level. M Water-inlet. N Water-seal. O Tappet.

(2) Automatic; water-to-carbide; contact.

A generating plant known as "L'Étoile" made by this firm. A tappet on the
bell of an equalising gasholder depresses a lever which causes water to flow
into a funnel, the outlet of which leads to a generating chamber containing
carbide.

Maker: MAISON SIRIUS, FR. MANGIAMELI & CO., 34 RUE DES
PETITS- HÔTELS, PARIS.

Page 422

Type: (1) Automatic; carbide-to-water.

The generating plant made by this firm comprises a drum-shaped carbide
holder mounted above a generating tank, a condenser, a washer, an
equalising gasholder, and a purifier. The drum A is divided into eight
chambers a each closed by a fastening on the periphery of the drum. These
chambers are packed with lump carbide, which is discharged from them in
turn through the funnel B into the generating tank, which is filled with
water to the level of the overflow cock b. A deflecting plate d in the tank
distributes the carbide and prevents the evolved gas passing out by way of
the funnel B. The gas evolved passes through the pipe O into the condenser,
which is packed with coke, through which the gas goes to the pipe E and so
to the washer P through the water, in which it bubbles and issues by the
pipe G into the gasholder. The bell L of the gasholder is connected by a
chain C to the axis of the drum A, on which is a pinion with pawl so
arranged that the pull on the chain caused by the fall of the bell of the
gasholder rotates the drum by 1/8 of a turn. The catch on the outside of the
carbide chamber, which has thereby been brought to the lowest position, is
at the same time freed, so that the contents of the chamber are discharged
through the funnel B. The evolved gas causes the bell to rise and the drum
remains at rest until, owing to the consumption of gas, the bell again falls
and rotates the drum by another 1/8 of a turn. Each chamber of the drum
holds sufficient carbide to make a volume of gas nearly equal to the
capacity of the gasholder. Thus each discharge of carbide very nearly fills
the gasholder, but cannot over-fill it. The bell is provided with a vent-pipe i,
which comes into operation should the bell rise so high that it is on the
point of becoming unsealed. From the gasholder the gas passes through the
pipe J, with cock e, to the purifier, which is charged with frankoline,
puratylene, or other purifying material, whence it passes to the pipe N
leading to the place of combustion. The generating tank is provided with a
sludge-cock g, and a cleaning opening with lid f. This generating plant has
been primarily designed for the use of acetylene for autogenous welding,
and is made also mounted on a suitable trolley for transport for this
purpose.

Page 423

(2) Automatic; carbide-to-water.

A later design of generating plant, known as the Type G, also primarily
intended for the supply of acetylene for welding, has the carbide store
mounted in the crown of the bell of the equalising gasholder, to the framing
of the tank of which are attached a purifier, charged with frankoline, and a
safety water-seal or valve. The whole plant is mounted on a four-legged
stand, and is provided with handles for carrying as a whole without
dismounting. It is made in two sizes, for charges of 5-1/2 and 11 lb. of
carbide respectively.

GERMANY.

Maker: KELLER AND KNAPPICH, G.m.b.H., AUGSBURG.

Type: Non-automatic; carbide-to-water.

The "Knappich" generating plant made by this firm embodies a generating
tank, one-half of which is closed, and the other half of which is open at the
top, containing water. A small drum containing carbide is attached by a
clamp to the end of a lever which projects above the open half of the tank.
The lever is fastened to a horizontal spindle which is turned through 180°
by means of a counter-weighted lever handle. The carbide container is thus
carried into the water within the closed half of the tank, and is opened
automatically in transit. The carbide is thus exposed to the water and the
evolved gas passes through a pipe from the top of the generating tank to a
washer acting on the Livesey principle, and thence to a storage gasholder.
The use of closed carbide containers in charging is intended to preclude the
introduction of air into the generator, and the evolution and escape of gas to
the air while the carbide is being introduced. Natural circulation of the
water in the generating tank is encouraged with a view to the dissipation of

Page 424

heat and washing of the evolved gas. From the gasholder the gas passes in a
downward direction through two purifiers arranged in series, charged with a
material supplied under the proprietary name of "Carburylen." This material
is stated to act as a desiccating as well as a purifying agent. The general
arrangement of the plant is shown in the illustration. (Fig. 38).

Maker: NORDISCHE AZETYLEN-INDUSTRIE; ALTONA-OTTENSEN.

Type: Automatic; water-to-carbide; "drawer."

The apparatus made by this firm consists of an equalising gasholder with
bell D and tank E, a water-tank O, and two drawer generators C situated in
the base of the gasholder tank. The water-supply from the tank O through
the pipe P with valve Q is controlled by the rise and fall of the bell through
the medium of the weight J attached to the bell. When the bell descends this
weight rests on K and so moves a counter-weighted lever, which opens the
valve Q. The water then flows through the nozzle B into one division of the
funnel A and down the corresponding pipe to one of the generators. The
generators contain trays with compartments intended to be half filled with
carbide. The gas evolved passes up the pipe T and through the seal U into
the bell of the gasholder. There is a safety pipe F, the upper end of which is
carried outside the generator house. From the gasholder the gas is delivered
through the cock M to a purifier charged with a special purifying material
mixed with cork waste and covered with wadding. There is a drainage cock
N at the base of the purifier. The nozzle B of the water-supply pipe is shifted
to discharge into either compartment of the funnel A, according to which of
the two generators is required to be in action. The other generator may then
be recharged without interfering with the continuous working of the plant.

Page 425

GREAT BRITAIN AND IRELAND.

Maker: THE ACETYLENE CORPORATION OF GREAT BRITAIN LTD.,
49 VICTORIA STREET, LONDON, S.W.

Type: (1) Automatic; water-to-carbide; contact, superposed pans.

The "A1" generating plant made by this firm comprises a bell gasholder,
with central guide, standing alongside the generator. The generator consists
of a rectangular tank in which is a generating chamber having a water-
sealed lid with pressure test-cock I. Into the generating chamber fit a
number of pans J, which are charged with carbide. Water is supplied to the
generating chamber from an overhead tank B through the starting tap D and
the funnel E. It flows out of the supply-pipe near the top of the generating
chamber through a slot in the side of the pipe facing the corner of the
chamber, so that it runs down the latter without splashing the carbide in the
upper pans. It enters first the lowest carbide pan through the perforations,
which are at different levels in the side of the pan. It thus attacks the carbide
from the bottom upwards. The evolved gas passes from the generating
chamber through a pipe opening near the top of the same to the washer A,
which forms the base of the generating tank. It bubbles through the water in
the washer, which therefore also serves as a water-seal, and passes thence to
the gasholder. On the bell of the gasholder is an arm C which, when the
holder descends nearly to its lowest point, depresses the rod C, which is
connected by a chain to a piston in the outlet-pipe from the water-tank B.
The fall of the gasholder thereby raises the piston and allows water to flow
out of the tank B through the tap D to the funnel E. The generating tank is
connected by a pipe, with tap G, with the washer A, and the water in the
generating tank is run off through this pipe each time the generating
chamber is opened for recharging, thereby flushing out the washer A and
renewing the water in the same. There is a sludge discharging tap F. With a

Page 426

view to the ready dissipation of the heat of generation the generating
chamber is made rectangular and is placed in a water-tank as described.
Some of the heat of generation is also communicated to the underlying
washer and warms the water in it, so that the washing of the gas is effected
by warm water. Water condensing in the gasholder inlet-pipe falls
downwards to the washer. There is a water lip H by which the level of the
water in the washer is automatically kept constant. The gasholder is
provided with a safety-pipe K, which allows gas to escape through it to the
open before the sides of the holder become unsealed, should the holder for
any reason become over-filled. The holder is of a capacity to take the whole
of the gas evolved from the carbide in one pan, and the water- tank B holds
just sufficient water for the decomposition of one charge of the generator.
From the gasholder the gas passes through a purifier, which is ordinarily
charged with "Klenzal," and a baffle-box for abstraction of dust, to the
service-pipe. With plants intended to supply more than forty lights for six
hours, two or more generating chambers are employed, placed in separate
compartments of one rectangular generating tank. The water delivery from
the water-tank B then takes place into a trough with outlets at different
levels for each generating chamber. By inspection of this trough it may be
seen at once whether the charge in any generating chamber is unattacked, in
course of attack, or exhausted.

(2) Automatic; water-to-carbide; contact.

The same firm also makes the "Corporation Flexible-Tube Generator,"
which is less costly than the "A1" (vide supra). The supply of water to the
generating vessels takes place from the tank of the equalising bell gasholder

Page 427

and is controlled by a projection on the bell which depresses a flexible tube
delivering into the generating vessels below the level of the water inlet to
the tube.

(3) Automatic; water-to-carbide; "drawer."

The same firm also makes a generator known as the "A-to-Z," which is less
costly than either of the above. In it water is supplied from the tank of a bell
gasholder to a drawer type of generator placed in the base of the gasholder
tank. The supply of water is controlled by an external piston- valve actuated
through the rise and fall of the bell of the gasholder. The flow of water to
the generator is visible.

Maker: THE ACETYLENE GAS AND CARBIDE OF CALCIUM CO.,
PONTARDAWE, R.S.O., GLAM.

Type: Automatic; water-to-carbide; flooded compartment.

The "Owens" generator made by this firm comprises an equalising bell
gasholder alongside which are placed two or more inclined generating
cylinders. The front lower end of each cylinder is fitted with a lid which is
closed by a screw clamp. There is inserted in each cylinder a cylindrical
trough, divided into ten compartments, each of which contains carbide.
Water is supplied to the upper ends of the cylinders from a high-level tank
placed at the back of the gasholder. In the larger sizes the tank is
automatically refilled from a water service through a ball-cock. The outlet-
valve of this tank is operated through a counter- weighted lever, the
unweighted end of which is depressed by a loop, attached to the crown of
the gasholder bell, when the bell has nearly reached its lowest position. This
action of the bell on the lever opens the outlet-valve of the tank and allows
water to flow thence into one of the generating cylinders. It is discharged
into the uppermost of the compartments of the carbide trough, and when the
carbide in that compartment is exhausted it flows over the partition into the
next compartment, and so on until the whole trough is flooded. The gas
passes from the generating cylinders through a water-seal and a baffle plate
condenser placed within the water link of the gasholder to the bell of the
latter. There is a water seal on the water supply-pipe from the tank to the
generators, which would be forced should the pressure within the generators

Page 428

for any reason become excessive. There is also a sealed vent- pipe which
allows of the escape of gas from the holder to the open should the holder for
any reason be over filled. The gas passes from the holder through a purifier
charged with "Owens" purifying material to the service pipe. The plant is
shown in Fig 41.

Maker ACETYLENE ILLUMINATING CO, LTD, 268-270 SOUTH
LAMBETH ROAD, LONDON, SW

Type (1) Non automatic, carbide to water

The generator A of this type made by this firm is provided with a loading
box B, with gas tight lid, into which the carbide is put. It is then discharged
by moving a lever which tilts the hinged bottom D of the box B, and so tips
the carbide through the shoot E on to the conical distributor F and into the
water in the generating chamber. There is a sludge cock G at the base of the
generator. Gas passes as usual from the generator to a washer and storage
gasholder. Heratol is the purifying material supplied.

Page 429

(2) Non-automatic; water-to-carbide; contact.

The generator A is provided with a carbide container with perforated base,
and water is supplied to it from a delivery-pipe through a scaled overflow.
The gas evolved passes through the pipe E to the washer B, which contains
a distributor, and thence to the storage gasholder G. There is a sludge-cock
F at the base of the generator. From the gasholder the gas passes through
the purifier D, charged with heratol, to the service-pipe.

Maker: THE ALLEN CO., 106 VICTORIA STREET, LONDON, S.W.

Type: Automatic; water-to-carbide; contact, superposed trays.

The generating plant made by this firm comprises an equalising bell
gasholder, from the tank of which water is supplied through a flexible tube
to the top of a water-scaled generating chamber in which is a vertical

Page 430

cylinder containing a cage packed with carbide. The open end of the
flexible tube is supported by a projection from the bell of the gasholder, so
that as the bell rises it is raised above the level of the water in the tank and
so ceases to deliver water to the generator until the bell again falls. The
water supplied flows by way of the water-seal of the cover of the generating
chamber to the cylinder containing the carbide cage. Larger sizes have two
generating chambers, and the nozzle of the water delivery-pipe may be
switched over from one to the other. There is an overflow connexion which
brings the second chamber automatically into action when the first is
exhausted. One chamber may be recharged while the other is in action.
Spare cylinders and cages are provided for use when recharging. There is a
cock for drawing off water condensing in the outlet-pipe from the
gasholder. The gas passes from the holder to the lower part of a purifier
with water-scaled cover, through the purifying material in which it rises to
the outlet leading to the service-pipe. Purifying material under the
proprietary name of the "Allen" compound is supplied. The plant is shown
in Fig. 44.

Maker: THE BON-ACCORD ACETYLENE GAS CO., 285 KING
STREET, ABERDEEN.

Type: Automatic; water-to-carbide; contact, superposed trays.

Page 431

The "Bon Accord" generating plant made by this firm comprises an
equalising displacement gasholder B immersed in a water-tank A. Alongside
the tank are placed two water-jacketed generating chambers G1 and G2
containing cages K charged with carbide. Water passes from within the
gasholder through the water inlet- pipes L1 L2, the cock H, and the pipes F1
F2 to the generating chambers, from which the gas evolved travels to the
holder B, in which it displaces water until the water-level falls below the
mouths of the pipes L1 and L2, and so cuts off the supply of water to the
generating chambers. The gas passes from the holder B through the pipe
with outlet-cock T to a washer containing an acid solution for the
neutralisation of ammonia, then through a purifier containing a "special
mixture of chloride of lime." After that through a tower packed with lime,
and finally through a pressure regulator, the outlet of which is connected to
the service-pipe. There is an indicator I to show the amount of gas in the
holder. One generator may be charged while the other is in action.

Maker: FREDK. BRABY AND CO., LTD., ASHTON GATE WORKS,
BRISTOL; AND 352-364 EUSTON ROAD, LONDON.

Type: (I) Automatic; carbide-to-water.

The "A" type of generator made by this firm comprises an equalising bell
gasholder, round the bell of which are arranged a series of buckets which
are charged with carbide. Those buckets are discharged in turn as the bell
falls from time to time through a mechanism operated by a weight
suspended from a wire cord on a revolving spindle. The carbide is
discharged on to a different spot in the generating tank from each bucket.
There is a cock for the periodical removal of sludge. Gas passes through a
purifier charged with puratylene to the service-pipe. The disposition of the
parts of the plant and the operating mechanism arc shown in the
accompanying figure, which represents the generating apparatus partly in

Page 432

elevation and partly in section. The carbide buckets (1) are loosely hooked
on the flat ring (2) bolted to the gasholder tank (3). The buckets discharge
through the annular water-space (4) between the tank and the generator (5).
The rollers (6), fitted on the generator, support a ring (7) carrying radial
pins (8) projecting outwards, one pin for each bucket. The ring can travel
round on the rollers. Superposed on the ring is a tray (9) closed at the
bottom except for an aperture beneath the throat (11), on which is mounted
an inclined striker (12), which strikes the projecting tongues (1a) of the lids
of the buckets in turn. There is fixed to the sides of the generator a funnel
(13) with open bottom (13a) to direct the carbide, on to the rocking grid
(14) which is farther below the funnel than appears from the figure. Gas
passing up behind the funnel escapes through a duct (15) to the gasholder.
The ring (7) is rotated through the action of the weight (16) suspended by
the chain or rope (17) which passes round the shaft (18), which is supported
by the bracket (19) and has a handle for winding up. An escapement, with
upper limb (20a) and lower limb (20b), is pivotally centred at (21) in the
bracket (19) and normally restrains the turning of the shaft by the weight.
There is a fixed spindle (24) supported on the bracket (23)--which is fixed
to the tank or one of the guide-rods--having centred on it a curved bar or
quadrant (25) running loose on the spindle (24) and having a crank arm (26)
to which is connected one end of a rod (27) which, at the other end, is
connected to the arm (28) of the escapement. The quadrant bears at both
extremities against the flat bar (29) when the bell (22) is sufficiently raised.
The bar (29) extends above the bell and carries an arm (30) on which is a
finger (30a). There is fixed on the shaft (18) a wheel (31), with diagonal
divisions or ways extending from side to side of its rim, and stop-pins (32)
on one side at each division. A clutch prevents the rotation of the wheel
during winding up.

Page 433

(2) Automatic; water-to-carbide; contact, superposed trays.

The type "B" generator made by this firm comprises an equalising bell
gasholder, a crescent-shaped feed water-tank placed on one side of the
gasholder, and mechanism for controlling a tap on the pipe by which the
feed water passes to a washer whence it overflows through a seal into a
horizontal generating chamber containing cells packed with carbide. The
mechanism controlling the water feed embodies the curved bar (25),
connecting-rod (27) and flat guide-bar (29) as used for controlling the
carbide feed in the "A" type of generator (Fig. 46). When the bell descends
water is fed into the washer, and the water-level of the seal is thus
automatically maintained. The gas evolved passes through a pipe,
connecting the seal on the top of the generating chamber with the washer,
into the gasholder. Plants of large size have two generating chambers with
connexions to a single washer.

Maker: THE DARGUE ACETYLENE GAS CO., 57 GREY STREET,
NEWCASTLE-ON- TYNE.

Type: Automatic; water-to-carbide; "drawer."

The "Dargue" acetylene generator made by this firm comprises an
equalising bell gasholder B floating in a water-tank A, which is deeper than
is necessary to submerge the bell of the gasholder. In the lower part of this
tank are placed two or more horizontal generating chambers which receive
carbide-containing trays divided by partitions into a number of

Page 434

compartments which are half filled with carbide. Water is supplied from the
gasholder tank through the tap E and pipe F to the generating chambers in
turn. It rises in the latter and floods the first compartment containing
carbide before gaining access to the second, and so on throughout the series
of compartments. As soon as the carbide in the first generating chamber is
exhausted, the water overflows from it through the pipe with by-pass tap J
to the second generating chamber. The taps G and H serve to disconnect one
of the generating chambers from the water-supply during recharging or
while another chamber is in action. The gas evolved passes from each
generating chamber through a pipe L, terminating in the dip-pipe M, which
is provided with a baffle-plate having very small perforations by which the
stream of gas is broken up, thereby subjecting it to thorough washing by the
upper layers of water in the gasholder tank. The washed gas, which thus
enters the gasholder, passes from it through the pipe N with main cock R to
the service- pipes. The water-supply to the generator is controlled through
the tap E, which is operated by a chain connected to an arm attached to the
bell of the gasholder.

The water in the gasholder tank is accordingly made to serve for the supply
of the generating chambers, for the washing of the gas, and as a jacket to
the generating chambers. The heat evolved by the decomposition of the
carbide in the latter creates a circulation of the water, ensuring thereby
thorough mixing of the fresh water, which is added from time to time to
replace that removed for the decomposition of the carbide, with the water
already in the tank. Thus the impurities acquired by the water from the
washing of the gas do not accumulate in it to such an extent as to render it
necessary to run off the whole of the water and refill, except at long
intervals. A purifier, ordinarily charged with puratylene, is inserted in many
cases after the main cock R. The same firm makes an automatic generator
on somewhat similar lines, specially designed for use in autogenous
welding, the smaller sizes of which are readily portable.

Page 435

Maker: J. AND J. DRUMMOND, 162 MARKET STREET, ABERDEEN.

Type: Automatic; water-to-carbide; contact.

The generating plant made by this firm comprises two or more generating
vessels B in which carbide is contained in removable cases perforated at
different levels. Water is supplied to these generating vessels, entering them
at the bottom, from an elevated tank A through a pipe C, in which is a tap F
connected by a lever and chain L with the bell G of the equalising gasholder
H, into which the evolved gas passes. The lever of the tap F is counter-
weighted so that when the bell G descends the tap is opened, and when the
bell rises the tap is closed. The gas passes from the generating chambers B
through the pipe D to the washer-cooler E and thence to the gasholder.
From the latter it passes through the dry purifier J to the service-pipe. The
gasholder bell is sealed in oil contained in an annular tank instead of in the
usual single-walled tank containing water. The purifying material ordinarily
supplied is puratylene. The apparatus is also made to a large extent in a
compact form specially for use on board ships.

Agents: FITTINGS, LTD., 112 VICTORIA STREET, S.W.

Page 436

Type: Automatic; carbide-to-water.

The "Westminster" generator supplied by this firm is the "Davis" generator
described in the section of the United States. The rights for the sale of this
generator in Great Britain are held by this firm.

Maker: LOCKERBIE AND WILKINSON, TIPTON, STAFFS.

Type: (1) Automatic; water-to-carbide; contact, superposed trays.

The "Thorscar" generator of this firm comprises an equalising gasholder,
the gas-space of the bell B of which is reduced by conical upper walls.
When the bell descends and this lining enters the water in the tank A the
displacement of water is increased and its level raised until it comes above
the mouths of the pipes E, through which a portion then flows to the
generators D. The evolution of the gas in the latter causes the bell to rise
and the conical lining to be lifted out of the water, the level of which
thereupon falls below the mouths of the pipes E in consequence of the
reduced displacement of the bell. The supply of water to the generators is
thus cut off until the bell again falls and the level of the water in the tank is
raised above the mouths of the pipes E. The generating chambers D are
provided with movable cages F in which the carbide is arranged on trays.
The gas evolved travels through a scrubbing-box G containing charcoal,
and the pipe J with drainage-pipe P to the water-seal or washer K inside the
holder, into which it then passes. The outlet-pipe for gas from the holder
leads through the condensing coil L immersed in the water in the tank to the
condensed water-trap N, and thence by the tap Q to the supply-pipe. The
generating chambers are water-jacketed and provided with gauge-glasses H
to indicate when recharging is necessary, and also with sludge-cocks M. The
object of the displacement cone in the upper part of the bell is to obtain
automatic feed of water to the carbide without the use of cocks or movable
parts. There is a funnel- shaped indicator in front of the tank for regulating
the height of water to a fixed level, and also an independent purifier, the
purifying material or which is supplied under the proprietary name of
"Thorlite."

Page 437

(2) Non-automatic; water-to-carbide; "drawer."

This generating plant, the "Thorlite," comprises a water-tank A from which
water is admitted to the drawer generating chambers B, one of which may
be recharged while the other is in operation. The gas evolved passes
through a seal C to the gasholder D, whence it issues as required for use
through the purifier E to the supply-pipe. For the larger sixes a vertical
generating chamber is used. The purifier and purifying material are the
same as for the automatic plant of the same firm.

Maker: THE MANCHESTER ACETYLENE GAS CO., LTD., ACRE
WORKS, CLAYTON, MANCHESTER.

Type: Automatic; water-to-carbide; "drawer."

The plant made by this firm comprises an equalising gasholder A from the
tank of which water is supplied to generating cylinders B placed at the side
of the tank, the number of which varies with the capacity of the plant. The
cylinders receive tray carbide-containers divided into compartments
perforated at different levels so that they are flooded in turn by the
inflowing water. A weight C carried by a chain D from one end of a lever E

Page 438

pivoted to the framing of the gasholder is supported by the bell of the
gasholder when the latter rises; but when the holder falls the weight C,
coming upon the lever E, raises the rod F, which thereupon opens the valve
G, which then allows water to flow from the gasholder tank through the
pipe H to one of the generating cylinders. When the carbide in the first
cylinder is exhausted, the water passes on to a second. One generating
cylinder may be recharged while another is in action. The rising of the
holder, due to the evolved gas, causes the bell to support the weight C and
thus closes the water supply-valve G. The gas evolved passes through
vertical condensers J into washing- boxes K, which are placed within the
tank. The gas issues from the washing-boxes into the gasholder bell,
whence it is withdrawn through the pipe L which leads to the purifier.
Puratylene is the purifying material ordinarily supplied by this firm.

Maker: R,. J. MOSS AND SONS, 98 SNOW HILL, BIRMINGHAM.

Type: (1) Automatic; water-to-carbide; superposed trays.

The "Moss" generator, "Type A," made by this firm comprises an equalising
gasholder, four, three, or two generating chambers, and an intermediate
water-controlling chamber. Each generating chamber consists of a frame in
which are arranged about a central tube trays half filled with carbide,
having water inlet-holes at several different levels, and each divided into
two compartments. Over this frame is put a bell-shaped cover or cap, and
the whole is placed in an outer tank or bucket, in the upper part of which is
a water inlet-orifice. The water entering by this orifice passes down the
outside of the bell, forming a water-seal, and rises within the bell to the
perforations in the carbide trays from the lowest upwards, and so reaches

Page 439

the carbide in successive layers until the whole has been exhausted. The gas
evolved passes through the central tube to a water- seal and condensing
tank, through which it escapes to the controlling chamber, which consists of
a small water displacement chamber, the gas outlet of which is connected to
the equalising gasholder. The bell of the equalising gasholder is weighted or
balanced so that when it rises to a certain point the pressure is increased to a
slight extent and consequently the level of the water in the displacement
controlling chamber is lowered. In this chamber is a pipe perforated at
about the water-level, so that when the level is lowered through the
increased pressure thrown by the rising gasholder the water is below the
perforations and cannot enter the pipe. The pipe leads to the water inlet-
orifices of the generating tanks and when the equalising gasholder falls, and
so reduces the pressure within the controlling chamber, the water in the
latter rises and flows through the pipe to the generating tanks. The water
supplied to the carbide is thus under the dual control of the controlling
chamber and of the differential pressure within the generating tank. The
four generators are coupled so that they come into action in succession
automatically, and their order of operation is naturally reversed after each
recharging. An air-cock is provided in the crown of the bell of each
generator and, in case there should be need of examination when charged,
cocks are provided in other parts of the apparatus for withdrawing water.
There is a sludge-cock on each generator. The gas passes from the
equalising gasholder through a purifier, for which the material ordinarily
supplied is puratylene.

The "Moss Type B" generator is smaller and more compact than "Type A."
It has ordinarily only two generating chambers, and the displacement water
controlling chamber is replaced by a bell governor, the bell of which is
balanced through a lever and chains by a weight suspended over the bell of
the equalising gasholder, which on rising supports this counter-weight and

Page 440

so allows the governor bell to fall, thereby cutting off the flow of water to
the generating chambers.

The "Moss Type C" generator is smaller than either "Type A" or "B," and
contains only one generating chamber, which is suspended in a pocket in
the crown of the equalising gasholder. Water enters through a hole near the
top of the bucket of the generating chamber, when it descends with the
holder through the withdrawal of gas from the latter.

(2) Semi-automatic; water-to-carbide; superposed trays.

The "Moss Semi-Non-Auto" generating plant resembles the automatic plant
described above, but a storage gasholder capable of holding the gas evolved
from one charging of the whole of the generating chambers is provided in

Page 441

place of the equalising gasholder, and the generation of gas proceeds
continuously at a slow rate.

The original form of the "Acetylite" generator (vide infra) adapted for
lantern use is also obtainable of R. J. Moss and Sons.

Maker: WM. MOYES AND SONS, 115 BOTHWELL STREET,
GLASGOW.

Type: Automatic; carbide-to-water. The "Acetylite" generator made by this
firm consists of an equalising gasholder and one or more generating tanks
placed alongside it. On the top of each generating tank is mounted a
chamber, with conical base, charged with granulated carbide 1/8 to 1/2 inch
in size. There is an opening at the bottom of the conical base through which
passes a rod with conical head, which, when the rod is lowered, closes the
opening. The rod is raised and lowered through levers by the rise and fall of
the bell of the equalising gasholder, which, when it has risen above a certain
point, supports a counter-weight, the pull of which on the lever keeps the
conical feed-valve open. The gas evolved in the generating tanks passes
through a condensing chamber situated at the base of the tank into the
equalising gasholder and so automatically controls the feed of carbide and
the evolution of gas according to the rate of withdrawal of the gas from the
holder to the service-pipes. The water in the gasholder tank acts as a
scrubbing medium to the gas. The generating tanks are provided with
sludge-cocks and a tap for drawing off condensed water. The gas passes
from the equalising gasholder, through a purifier and dryer charged with
heratol or other purifying material to the service-pipes. The original form of
the "Acetylite" generator is shown in elevation and vertical section in Fig.
55. Wm. Moyes and Sons now make it also with a detached equalising
gasholder connected with the generator by a pipe in which is inserted a
lever cock actuated automatically through a lever and cords by a weight
above the bell of the gasholder. Some other changes have been made with a
view to securing constancy of action over long periods and uniformity of
pressure. In this form the apparatus is also made provided with a clock-
work mechanism for the supply of lighthouses, in which the light is flashed
on periodically. The flasher is operated through a pilot jet, which serves to

Page 442

ignite the gas at the burners when the supply is turned on to them at the
prescribed intervals by the clock- work mechanism.

Maker: THE PHÔS CO., 205 AND 207 BALLS POND ROAD, LONDON,
N. Type: Non-automatic; water-to-carbide; drip.

The type "E" generator made by this firm consists of a generating chamber
placed below a water chamber having an opening with cap E for refilling.
The generating chamber in closed by a door B, with rubber washer C, held
in position by the rod A, the ends of which pass into slots, and the screw A'.
The movable carbide chamber D has its upper perforated part half filled
with carbide, which is pressed upwards by a spring D'. The carbide chamber
when filled is placed in the generating chamber, which is closed, and the
lever F of one of the taps F' is turned from "off" to "on," whereupon water
drips from the tank on to the carbide. The evolution of gas is stopped by
reversing the lever of the tap. The second tap is provided for use when the
evolution of gas, through the water-supply from the first tap, has been
stopped and it is desired to start the apparatus without waiting for water
from the first tap to soak through a layer of spent carbide. The two taps are
not intended for concurrent use. The evolved gas passes through a purifier
containing any suitable purifying material to the pipes leading to the
burners.

Page 443

Maker: ROSCO ACETYLENE COMPANY, BELFAST.

Type: Non-automatic; carbide-to-water

The "Rosco" generating plant made by this firm comprises a generating
tank A which is filled with water to a given level by means of the funnel-
mouthed pipe B and the overflow O. On the top of the water-sealed lid of
the generating tank is mounted the carbide feed-valve L, which consists of a
hollow plug-tap with handle M. When the handle M is turned upwards the
hollow of the tap can be filled from the top of the barrel with carbide. On
giving the tap a third of a turn the hollow of the plug is cut off from the
outer air and is opened to the generating tank so that the carbide contained
in it is discharged over a distributor E on to the tray N in the water in the
generating tank. The gas evolved passes through the scrubber and seal-pot J
to the storage gasholder Q. From the latter the gas passes through the dry
purifier T to the service-pipe. A sludge- cock P is provided at the bottom of
the generating tank and is stated to be available for use while generation of
gas is proceeding. The purifying material ordinarily supplied is
"Roscoline."

Maker: THE RURAL DISTRICTS GAS LIGHT CO., 28 VICTORIA
STREET, S.W.

Type: Automatic; water-to-carbide; contact, superposed trays.

The "Signal-Arm" generating apparatus made by this firm comprises a bell
gasholder A, from the tank B of which water is supplied through a swivelled
pipe C to a generating chamber D. One end of the swivelled pipe is
provided with a delivery nozzle, the other end is closed and counter-
weighted, so that normally the open end of the pipe is raised above the level
of the water in the tank. A tappet E on the bell of the gasholder comes into
contact with, and depresses, the open end of the swivelled pipe when the

Page 444

bell falls below a certain point. As soon as the open end of the swivelled
pipe has thus been lowered below the level of the water in the tank, water
flows through it into the funnel-shaped mouth F of a pipe leading to the
bottom of the generating chamber. The latter is filled with cages containing
carbide, which is attacked by the water rising in the chamber. The gas
evolved passing into and raising the bell of the gasholder causes the open
end of the swivelled pipe to rise, through the weight of the counterpoise G,
above the level of the water in the tank and so cuts off the supply of water
to the generating chamber until the bell again descends and depresses the
swivelled pipe. The tappet on the bell also displaces a cap H which covers
the funnel-shaped mouth of the pipe leading to the generating chamber,
which cap, except when the swivelled supply-pipe is being brought into
play, prevents any extraneous moisture or other matter entering the mouth
of the funnel. Between the generating chamber and the gasholder is a three-
way cock J in the gas connexion, which, when the gasholder is shut off
from the generator, brings the latter into communication with a vent-pipe K
leading to the open. The gas passes from the holder to a chamber L under
grids packed with purifying material, through which it passes to the outlet
of the purifier and thence to the service-pipe. Either heratol or chloride of
lime is used in the purifier, the lid of which, like the cover of the generator,
is water-sealed.

Maker: ST. JAMES' ILLUMINATING CO., LTD., 3 VICTORIA STREET,
LONDON, S.W.

Type: (1) Automatic; water-to-carbide; contact, superposed trays.

This plant consists of the generators A, the washer B, the equalising
gasholder C, the purifier D, and the water-tank E. The carbide is arranged in
baskets in the generators to which water is supplied from the cistern E

Page 445

through the pipe F. The supply is controlled by means of the valve H, which
is actuated through the rod G by the rise and fall of the gasholder C. Gas
travels from the gasholder through the purifier D to the service-pipe. The
purifier is packed with heratol resting on a layer of pumice. The washer B
contains a grid, the object of which is to distribute the stream of gas through
the water. There is a syphon-pot J for the reception of condensed moisture.
Taps K are provided for shutting off the supply of water from the generators
during; recharging, and there is an overflow connexion L for conveying the
water to the second generator as soon as the first is exhausted. There is a
sludge-cock M at the base of each generator.

(2) Non-automatic; water-to-carbide; contact, superposed trays.

This resembles the preceding plant except that the supply of water from the
cistern to the generators takes place directly through the pipe N (shown in
dotted lines in the diagram) and is controlled by hand through the taps K.
The automatic control-valve H and the rod G are omitted. The gasholder C
is increased in size so that it becomes a storage holder capable of containing
the whole of the gas evolved from one charging.

Maker: THE STANDARD ACETYLENE CO., 123 VICTORIA STREET,
LONDON, S.W.

Type: (1) Non-automatic; carbide-to-water.

This plant comprises the generator A, the washer B, the storage gasholder C,
and the purifier D. The generator is first filled with water to the crown of
the cover, and carbide is then thrown into the water by hand through the
gas-tight lock, which is opened and closed as required by the horizontal
handle P. A cast-iron grid prevents the lumps of carbide falling into the
sludge in the conical base of the generator. At the base of the cone is a

Page 446

sludge-valve G. The gas passes from the generator through the pipe H into
the washer B, and after bubbling through the water therein goes by way of
the pipe K into the gasholder C. The syphon- pot E is provided for the
reception of condensed moisture, which is removed from time to time by
the pump M. From the gasholder the gas flows through the valve R to the
purifier D, whence it passes to the service-pipes. The purifier is charged
with material supplied under the proprietary name of "Standard."

(2) Automatic; water-to-carbide; contact, superposed trays.

This plant comprises the generators A, the washer B, the equalising
gasholder C, the purifier D, and the water-tank E. The carbide is arranged
on a series of wire trays in each generator, to which water is supplied from
the water-tank E through the pipe Y and the control-tap U. The gas passes
through the pipes H to the washer B and thence to the holder C. The supply
of water to the generators is controlled by the tap U which is actuated by the
rise and fall of the gasholder bell through the rod F. The gas passes, as in
the non-automatic plant, through a purifier D to the service-pipes. Taps W
are provided for cutting off the flow of water to either of the generators
during recharging and an overflow pipe h serves to convey the water to the
second generator as soon as the carbide in the first is exhausted. A sludge-
cook G is put at the base of each generator.

(3) Non-automatic; water-to-carbide; contact, superposed-trays.

This apparatus resembles the preceding except that the supply of water to
the generators is controlled by hand through the taps W, the control valve U

Page 447

being omitted, and the gasholder C being a storage holder of sufficient
dimensions to contain the whole of the acetylene evolved from one
charging.

Maker: THORN AND HODDLE ACETYLENE CO., 151 VICTORIA
STREET, S.W.

Type: Automatic; water-to-carbide; "drawer."

The "Incanto" generating plant made by this firm consists of a rising bell
gasholder which acts mainly on an equaliser. The fall of the bell depresses a
ball valve immersed in the tank, and so allows water to flow from the tank
past an outside tap, which is closed only during recharging, to a generating
chamber. The generating chamber is horizontal and is fixed in the base of
the tank, so that its outer case is surrounded by the water in the tank, with
the object of keeping it cool. The charge of carbide is placed in a partitioned
container, and is gradually attacked on the flooding principle by the water
which enters from the gasholder tank when the ball valve is depressed. The
gas evolved passes from the generating chamber by a pipe which extends
above the level of the water in the tank, and is then bent down so that its
end dips several inches below the level of the water. The gas issuing from
the end of the pipe is thus washed by the water in the gasholder tank. From
the gasholder the gas is taken off as required for use by a pipe, the mouth of
which is just below the crown of the holder. There is a lip in the upper edge
of the gasholder tank into which water is poured from time to time to
replace that consumed in the generation of the gas. There are from one to
three generating chambers in each apparatus according to its size. The
purifier is independent, and a purifying mixture under the proprietary name
of "Curazo" is supplied for use in it.

Page 448

Maker: WELDREN AND BLERIOT, 54 LONG ACRE, LONDON, W.C.

Type: Automatic; contact.

This firm supplies the "Acétylithe" apparatus (see Belgium).

Page 449

INDEX

Absorbed acetylene,
Acagine,
Accidents, responsibility for,
Acetone, effect of, on acetylene,
solution of acetylene in,
Acetylene-copper,
Acetylene-oil-gas,
Acetylene Association (Austrian)--regulations as to carbide,
Acetylene Association (British)--analysis of carbide,
generator rules,
pressure gauges,
purification rules,
Acetylene Association (German)--analysis of carbide,
holders,
generator rules,
standard carbide,
Acetylene tetrachloride, production of,
Ackermann burner,
Advantages of acetylene, general,
hygienic,
intrinsic,
pecuniary,
"After generation,"
Air, admission of, to burners,
and acetylene, ignition temperature of,
composition of,
dilution of acetylene with, before combustion,
effect of acetylene lighting on,
coal-gas lighting on,
on illuminating power of acetylene,
paraffin lighting on,
in acetylene,
in flames, effect of,
in generators, danger of,
objections to,
in incandescent acetylene,
in service-pipes,
proportion of, rendering acetylene explosive,
removing, from pipes,
specific gravity of,

Page 450

sterilised by flames,
Air-gas,
and acetylene, comparison between,
and carburetted acetylene, comparison between,
effect of cold on,
illuminating power of,
Alcohol, action of, on carbide,
for carburetting acetylene,
holder seals,
from acetylene, production of,
Allgemeine Carbid und Acetylen Gesellschaft burner,
Alloys, fusible, for testing generators,
Alloys of copper. See Copper (alloyed)
Aluminium sulphide, in carbide
America (U.S.), regulations of the National Board of Fire
Underwriters,
American gallon, value of,
Ammonia, in acetylene,
in coal-gas,
removal of,
solubility of, in water,
Analysis of carbide,
Ansdell, compressed and liquid acetylene,
Anthracene, formation of, from acetylene,
Anti-freezing agents,
Area of purifiers,
Argand burners,
Aromatic hydrocarbons,
Arrangement of generating plant,
Arsenious oxide purifier,
Atkins, dry process of generation,
Atmospheric moisture and carbide,
Atomic weights,
Attention needed by generators,
Austrian Acetylene Association, regulations as to carbide,
Austrian Government Regulations,
Autogenous soldering and welding,
Automatic generators. See Generators (automatic)

B

Baking of carbide
Ball-sockets for acetylene,
Barium peroxide purifier,
sulphate in bleaching-powder,
Barrel, gas, for acetylene, quality of

Page 451

Bell gasholders. See Holders (rising)
Benz purifying material,
Benzene,
for carburetting acetylene,
production of, from acetylene,
Benzine. See Petroleum spirit
Bergé, detection of phosphorus,
and Reychler, purification of acetylene,
and Reychler's reagent, solubility of acetylene in,
Bernat, formula for mains and pipes,
Berthelot, addition of chlorine to acetylene,
sodium acetate,
sulphuric acid and acetylene,
Berthelot and Matignon, thermochemical data,
and Vieille, dissolved acetylene,
Billwiller burners,
Black, acetylene,
Blagden, sodium hypochlorite,
Bleaching-powder purifier (simple),
Blochmann, copper acetylide,
Blow-off pipes. See Vent-pipes
Blowpipe, acetylene,
Boiling-ring,
Boistelle. See Molet
Borek, enrichment of oil-gas,
Bougie décimale,
Brackets for acetylene,
Bradley, Read, and Jacobs, calcium carbophosphide,
Brame and Lewes, manganese carbide,
Bray burners,
British Acetylene Association. See Acetylene Association
(British),
Fire Offices Committee Regulations,
regulations. See Acetylene Association (British); Home
Office;
Orders in Council
Bromine-water purifier,
Bullier, effect of heat on burners,
phosphorus in acetylene,
and Maquenne purifier,
Bunsen burner, principle of,
Bunte, enrichment of oil-gas,
Burner orifices and gas density,
Burners,
atmospheric,
principle of,
design of,
glassware for,

Page 452

heating,
incandescent,
Ackermann,
Allgemeine Carbid und Acetylen Gesellschaft,
Bray,
firing back in,
Fouché,
Günther's,
illuminating power of,
Jacob, Gebrüder,
Keller and Knappich,
Knappich,
O.C.A.,
pressure for,
principles of construction of,
Schimek,
Sirius,
Trendel,
typical,
Weber,
Zenith,
self-luminous,
Argand,
as standard of light,
Billwiller,
Bray,
choking of,
corrosion of,
cycle,
Falk, Stadelmann and Co.'s,
Konette,
Phôs,
Wiener's,
Dolan,
Drake,
effect of heat on,
Elta,
Falk, Stadelmann and Co.'s,
firing back in,
fish-tail,
Forbes,
Hannam's,
illuminating power of,
self-luminous injector,
Javal,
Kona,
Luta,
Naphey,

Page 453

Orka,
Phôs,
Pintsch,
pressure for,
rat-tail,
Sansair,
Schwarz's,
Stadelmann,
Suprema,
twin, angle of impingement in,
injector,
non-injector,
warping of,
Wiener's,
Wonder,
By-products, See also Residues

C

Cadenel, shape of incandescent acetylene mantle,
"Calcidum,"
Calcium carbide, action of heat on,
action of non-aqueous liquids on,
analysis of,
and carbon bisulphide, reaction between,
and hydroxide, reaction between,
and ice, reaction between,
and steam, reaction between,
and water, reaction between,
as drying material,
baking of,
balls and cartridges. See Cartridges
bulk of,
chemical properties of,
crushing of,
decomposition of,
by solids containing water,
heat evolved during,
imperfect,
speed of,
temperature attained during,
deterioration of, on storage,
drums of,
dust in,

Page 454

explosibility of,
fire, risk of,
formula for,
granulated,
heat-conducting power of,
of formation of,
impurities in,
inertness of,
in residues,
physical properties of,
purity of,
quality, regulations as to,
sale and purchase of, regulations as to,
scented,
shape of lumps of,
sizes of,
small, yield of gas from,
specific gravity of,
heat of,
standard, British,
German,
"sticks,"
storage regulations for,
subdivided charges of,
sundry uses of,
swelling of, during decomposition,
"treated,"
yield of acetylene from,
Calcium carbophosphide,
Calcium chloride, cause of frothing in generators,
for seals,
purifier,
solubility of acetylene in,
Calcium hydroxide,
adhesion of, to carbide,
and carbide, reaction between,
milk of, solubility of acetylene in,
physical properties of,
space occupied by,
Calcium hypochlorite,
Calcium oxide,
and water, reaction between,
hydration of,
hygroscopic nature of,
physical properties of,
Calcium phosphide,
Calcium sulphide,
Calorie, definition of,

Page 455

Calorific power of acetylene,
various gases,
Candle-power. See Illuminating power
Capelle, illuminating power of acetylene,
Carbide. See Calcium carbide
Carbide-containers,
air in,
filling of,
partitions in,
water-jacketing,
Carbide-feed generators. See Generators (carbide-to-water)
Carbide impurities in acetylene,
Carbide-to-water generators. See Generators (carbide-to-water)
Carbides, mixed,
Carbolic acid, production of, from acetylene,
Carbon, combustion of, in flames,
deposition of, in burners,
gaseous, heat of combustion of,
heat of combustion of,
vaporisation of,
pigment, production of,
Carbon bisulphide and acetylene, reaction between,
and calcium carbide, reaction between,
in coal-gas,
Carbon dioxide, addition of, to acetylene,
dissociation of,
effect of, on explosibility of acetylene,
for removing air from pipes,
heat of formation of,
produced by respiration,
benzene,
coal-gas,
in flame of acetylene,
Carbon monoxide, in acetylene,
heat of combustion of,
formation of,
temperature of ignition of,
Carbonic acid. See Carbon dioxide
Carburetted acetylene, composition of,
effect of cold on,
illuminating power of,
manufacture of,
pecuniary value of,
Carburetted water-gas, enrichment of,
Carburine. See Petroleum spirit
Carlson, specific heat of carbide,
Caro, acetone vapour in acetylene,
addition of petroleum spirit to generator water,

Page 456

air in incandescent acetylene,
calorific power of gases,
colour of incandescent acetylene,
composition of mantles,
durability of mantles,
heat production in generators,
illuminating power of carburetted acetylene,
of incandescent acetylene,
oil of mustard,
silicon in crude acetylene,
Caro and Saulmann, "Calcidum,"
Carriage, cost of, and artificial lighting,
Cartridges of carbide,
Cast-iron pipe for acetylene,
Castor oil for acetylene joints,
Catani, temperature of acetylene flame,
Caustic potash purifier,
Cedercreutz, yield of gas from carbide,
and Lunge, purification,
Ceilings, blackening of,
Ceria, proportion of, in mantles,
Cesspools for residues,
Chandeliers, hydraulic, for acetylene,
Charcoal and chlorine purifier,
Charging generators after dark,
at irregular intervals,
Chassiron lighthouse,
Chemical formulæ, meaning of,
Chemical reactions and heat,
of acetylene,
Chimneys for stoves, &c.,
glass, for burners,
Chloride of lime. See Bleaching-powder
Chlorine and acetylene, compounds of,
and charcoal purifier,
in acetylene,
Chromic acid purifier,
Cigars, lighted, danger of,
Claude and Hess, dissolved acetylene,
Coal-gas, enrichment of, with acetylene,
illuminating power of,
impurities in,
vitiation of air by,
Cocks, hand-worked, in generators,
Coefficient of expansion of acetone,
air,
dissolved acetylene,
gaseous acetylene,

Page 457

liquid acetylene,
simple gases,
Coefficient of friction of acetylene,
of coal-gas,
Coke filters for acetylene,
Cold, effect of, on acetylene,
on air-gas,
on carburetted acetylene,
on generation,
Colour judging by acetylene,
of acetylene flame,
of air-gas flame,
Colour of atmospheric acetylene flame,
of coal-gas flame,
of electric light,
of incandescent acetylene flame,
of spent carbide,
Combustion of acetylene,
deposit from,
Composition pipe for acetylene,
Compounds, endo- and exo-thermic,
explosive, of acetylene and copper,
"Compounds," of phosphorus and sulphur,
silicon,
Compressed acetylene,
Condensed matter in pipes, removal of,
Condensers,
Connexions, flexible, for acetylene,
Construction of generators, principles of,
regulations as to,
Contact generators,
Convection of heat,
Cooking-stoves,
Copper acetylide,
(alloyed) in acetylene apparatus,
(unalloyed) in acetylene apparatus,
and acetylene, reactions between,
carbides,
chloride purifier
Corrosion in apparatus,
avoidance of,
Corrosive sublimate purifier,
as test for phosphorus
Cost of acetylene lighting,
Cotton-wool filters for acetylene,
Council, Orders in. See Orders in Council
Counterpoises for rising holders,
Couples, galvanic,

Page 458

Coward. See Dixon
Critical pressure and temperature of acetylene,
Crushing of carbide,
"Cuprene,"
Cuprous chloride purifier,
Cycle lamps,
burners for,
dilute alcohol for,
Cylinders for absorbed acetylene,

D

Davy, addition of chlorine to acetylene,
Davy's lamp for generator sheds,
Decomposing vessels. See Carbide containers
Decomposition of acetylene,
of carbide, See Calcium carbide (decomposition of)
De Forcrand, heat of formation of carbide,
Density. See Specific gravity
Deposit at burner orifices,
on reflectors from combustion of acetylene,
Deterioration of carbide in air,
Diameter of pipes and explosive limits,
Diaphragms, flexible, in generators,
Diffusion through gasholder seals,
Diluted acetylene,
Dimensions of mains and pipes,
Dipping generators,
Displacement gasholders. See Holders (displacement)
Dissociation of acetylene,
carbon dioxide,
water vapour,
Dissolution of acetylene, depression of freezing-point by,
of gas in generators,
Dissolved acetylene,
Dixon and Coward, ignition temperature of acetylene,
of various gases,
Dolan burners,
Doors of generator sheds,
Drainage of mains,
Drake burners,
Driers, chemical,
Dripping generators,
Drums of carbide,

Page 459

Dry process of generation,
Dufour, addition of air to acetylene,
"Dummies" in gasholder tanks,
Dust and incandescent lighting,
in acetylene,
carbide,

E

Effusion of gases,
Eitner, explosive limits of acetylene,
and Keppeler, estimation of phosphine,
phosphorus in crude acetylene,
Electric lamps in generator sheds,
lighting, cost, and efficiency of,
Elta burner,
Endothermic compounds,
nature of acetylene,
Engines, use of acetylene in,
Enrichment, value of acetylene for,
with acetylene,
épurène purifying material,
Equations, chemical, meaning of,
Erdmann, acetylene as a standard of light,
colour of acetylene flame,
production of alcohol,
Ethylene, formation of from acetylene,
heats of formation and combustion of,
ignition temperature of,
Exhaustion of air by flames,
Exothermic compounds,
Expansion of gaseous acetylene, coefficient of,
of liquid acetylene coefficient of,
various coefficients of,
Explosibility of carbide,
Explosion of chlorine and acetylene,
of compressed acetylene,
Explosive compounds of acetylene and copper,
effects of acetylene dissociation,
limits, meaning of term,
of acetylene,
of various gases,
nature of acetylene,
wave, speed of, in gases,

Page 460

Expulsion of air from mains,

F

Faced joints for acetylene,
Falk, Stadelmann and Co., boiling-ring,
burners,
cycle-lamp burner,
Ferric hydroxide purifier,
Féry, temperature of flames,
and Violle, acetylene as standard of light,
Filters for acetylene,
Filtration,
Fire Offices Committee Regulations (British),
risks of acetylene apparatus,
carbide,
flame illuminants,
Underwriters, United States, Regulations,
"Firing back" in incandescent burners,
self-luminous burners,
Fish, action of lime on,
Fittings for acetylene, quality of,
Flame, colour of, air-gas,
atmospheric acetylene,
coal-gas,
incandescent, acetylene,
self-luminous acetylene,
Flame illuminants, risk of fire with,
of acetylene containing air,
steadiness of acetylene,
Flame temperature of acetylene,
temperature of various gases,
Flames, distortion of, by solid matter,
effect of air on,
nitrogen on,
evolution of heat in,
light in,
jumping of,
liberation of carbon from,
loss of heat from,
shading of acetylene,
size of,
Flare lamps,
Flash-point of paraffin,

Page 461

Flexible connexions for acetylene,
Floats in holder seals,
Flooded-compartment generators,
Flow of gases in pipes,
Flues for heating burners,
Fog, transmission of light through,
Forbes burner,
Foreign regulations,
Formulæ, meaning of chemical,
Fouché, absorbed acetylene,
burner,
dissolved acetylene,
illuminating power of acetylene air mixtures,
incandescent acetylene,
liquid acetylene,
oxy-acetylene blowpipe,
Fournier. See Maneuvrier
Fowler, enrichment of oil-gas,
Fraenkel, deposit on reflectors from combustion of acetylene,
silicon in acetylene,
France, regulations of the Conseil d'Hygiène de la Seine,
village acetylene mains in,
Frank, freezing-point of calcium chloride solutions,
preparation of black pigment,
purifier,
Frankoline,
Freezing of generators,
of holder seals,
Freezing of portable lamps,
of pressure-gauges,
Freezing-point, depression of by dissolution of acetylene,
of calcium chloride solutions,
of dilute alcohol,
of dilute glycerin,
Freund and Mai, copper acetylide,
Friction of acetylene, coefficient of,
coal-gas, coefficient of,
gas in pipes,
Frost, effect of, on air-gas,
on carburetted acetylene,
Froth, lime, in acetylene,
Frothing in generators,
Fuchs and Schiff, olive oil,
Furnace gases for removing air from pipes,

G

Page 462

Gallon, American, value of,
Galvanic action,
Garelli and Falciola, depression of freezing-point by
dissolution of
acetylene,
Gas barrel for acetylene, objection to,
drying of,
engines, acetylene for,
escape of, from generators,
firing, effects of,
volumes, correction of, for temperature and pressure,
yield of, from carbide,
determining,
standard,
Gases, calorific value of,
effusion of,
explosive limits of,
flame temperature of,
illuminating power of,
inflammable properties of,
speed of explosive wave in,
temperature of ignition of,
Gasfitters' paint,
Gasholders. See Holders
Gatehouse, F. B., test-papers,
J. W., estimation of phosphine,
Gaud, blocking of burners,
polymerisation of acetylene,
Generation, dry process of,
Generating plant, regulations as to construction of,
Generator impurities in acetylene,
pressure, utilisation of,
sheds,
lighting of,
smoking in,
water, addition of bleaching-powder to,
of petroleum spirit to,
Generators and holders, isolation of,
attention needed by,
Generators, charging after dark,
chemical reactions in,
construction of,
copper in,
corrosion in,
dissolution of gas in,

Page 463

effect of tarry matter in,
escape of gas from,
failure of,
for analytical purposes,
for welding,
frothing in,
frozen, thawing of,
gauge of sheet-metal for,
heat dissipation in,
economy in,
produced in,
high temperatures and impurities in,
instructions for using,
joints in, making,
"lagging" for,
lead solder in,
materials for construction of,
maximum pressure in,
output of gas from,
overheating in,
polymerisation in,
pressure in,
protection of, from frost,
purchase of,
regulations as to,
American (National Board of Fire Underwriters),
Austrian Government,
British Acetylene Association,
Fire Offices Committee,
Home Office Committee(1901),
French (Council d' Hygiene de la Seine),
German Acetylene Association,
Hungarian Government,
Italian Government,
responsibility for accidents with,
selection of,
temperatures in,
typical,
vent-pipes for,
waste-pipes for,
water-jackets for,
water-scale in,
Generators (automatic),
advantages of,
carbide-to-water,
definition of,
flexible diaphragms for,
holders of,

Page 464

interlocking in,
mechanism for,
pressure thrown by,
speed of reaction in,
store of gas in,
supply of water to,
use of oil in,
water-to-carbide,
worked by holder bell,
by pressure,
Generators (carbide-to-water),
advantages of,
frothing of,
grids for,
loss of gas in,
maximum temperature in,
pressure in,
quantity of water required by,
Generators (contact),
(dipping),
temperatures in,
(dripping),
temperatures in,
(flooded compartment),
(non-automatic),
advantages of,
carbide-to-water,
hand-charging of,
water required for,
definition of,
speed of reaction in,
water-to-carbide,
(portable),
(shoot),
(water-to-carbide),
overheating in,
with carbide in excess,
with water in excess,
Gerard, silicon in crude acetylene,
Gerdes, acetylene copper,
German Acetylene Association. (See Acetylene Association,
German
Gin, heat of formation of carbide,
Glassware, for burners,
Glow-lamps, electric, in generator sheds,
Glucose for treatment of carbide,
Glycerin for holder-seals,
for wet meters,

Page 465

Governor, displacement holder as,
Governors,
Graham, effusion of gases,
Gramme-molecules,
Granjon, illuminating power of self-luminous burners,
phosphine in acetylene,
pressure,
purifier,
Granulated carbide. See Calcium carbide, (granulated)
Graphite, artificial, production of,
Grease for treatment of carbide,
Grids for carbide-to-water generators,
in purifiers,
Grittner, acetylene, and copper,
Guides for rising holders,
Güntner burner,

H

Haber, effect of heat on acetylene,
Haldane, toxicity of sulphuretted hydrogen,
Hammcrschmidt, correction of gas volumes,
and Sandmann, milk of lime,
Hannam's Ltd., burners,
Hartmann, acetylene flame,
Haze, on combustion of acetylene,
Heat absorbed during change of physical state,
action on acetylene. See Overheating
carbide,
and temperature, difference between,
conducting power of carbide
iron and steel,
water,
convected,
developed by acetylene lighting,
coal-gas lighting,
electric lighting,
paraffin lighting,
dissipation of, in generators,
economy in generators,
effect of, on acetylene. (See Overheating)
on burners,
evolution of, in flames,
expansion of gaseous acetylene by,

Page 466

liquid acetylene by,
from acetylene, production of,
latent. See Latent heat
loss of, from flames,
of chemical reactions,
of combustion of acetylene,
carbon,
carbon monoxide,
ethylene,
of formation of acetylene,
calcium carbide,
hydroxide,
oxide,
carbon dioxide,
monoxide,
ethylene,
water,
of hydration of calcium oxide,
of reaction between carbide and calcium hydroxide,
between carbide and water,
of solution of calcium hydroxide,
of vaporisation of carbon,
water,
radiant,
specific. See Specific heat
Heating apparatus for generator sheds,
Hefner unit,
Heil, atmospheric acetylene flame,
carburetted acetylene,
Heise, acetylene flame,
Hempel, enrichment of coal-gas,
Heratol,
Hess. See Claude
Hexachlorethane, production of,
High houses, supply of acetylene to,
Holder-bells, for testing mains,
supplying water to automatic generators,
weighting of,
Holder-seals, freezing of,
level of liquid in,
liquids in,
and pressure,
solubility of acetylene in,
use of floats in,
liquids in, for decomposing carbide,
oil in,
water in, for washing the gas,
Holders (gas) and generators, isolation of,

Page 467

and pressure, relationship between,
and purifiers, relative position of,
exposed, roofs over,
false interiors for,
freezing of,
gauge of sheet-metal for,
loss of pressure in,
moistening of gas in,
of automatic generators,
preservation of, from corrosion,
situation of,
size of,
vent-pipes for,
value of,
Holders (displacement),
action of,
pressure given by,
(rising),
guides and counterpoises for,
pressure thrown by,
equalisation of,
tanks for,
Home Office, maximum pressure permitted by,
prohibition of air in acetylene by,
Committee, 1901, recommendations,
report,
Home Secretary's Orders. See Orders in Council
Hoxie. See Stewart,
Hubou, acetylene black,
Hungarian rules for apparatus,
Hydraulic pendants for acetylene,
Hydrocarbons formed by polymerisation,
illuminating power of,
volatile, names of,
Hydrochloric acid in purified acetylene,
Hydrogen and acetylene, reactions between,
effect of, on acetylene flame,
ignition temperature of,
in acetylene,
liberated by heat from acetylene,
silicide in crude acetylene,
Hygienic advantages of acetylene,

I

Page 468

Ice, reaction between carbide and,
Ignition temperature of acetylene,
various gases,
Illuminating power and illuminating effect,
definition of,
of acetylene, after storage,
carburetted,
effect of air on,
incandescent,
nominal,
self-luminous,
of acetylene-oil-gas,
of air-gas,
of polymerised acetylene,
of candles,
of coal-gas,
of electric lamps,
of hydrocarbons, various,
of paraffin,
Illumination, amount of, required in rooms,
of lighthouses,
of optical lanterns,
Impurities in acetylene, carbide,
detection and estimation of,
effect of, on air,
generator,
harmfullness of,
water soluble,
See also Ammonia and Sulphuretted hydrogen
in coal-gas,
in purified acetylene,
maximum limits of,
Incandescent acetylene,
burners. See Burners (incandescent)
mantles,
Inertness of carbide,
Inflaming-point of acetylene,
Inflammability, spontaneous,
Installations, new, removal of air from,
Interlocking of automatic generators,
Iron and acetylene, reactions between,
and steel, heat-conducting power of,
silicide in carbide,
Insecticide, carbide residues as,
Isolation of apparatus parts,
Intensity, specific, of acetylene light,
of oil light,

Page 469

Italian Government rules,

J

Jackets for generators,
Jacob, Gebrüder, burner,
Jacobs. See Bradley
Jaubert, arsenious oxide purifier,
Javal burners,
blocking of,
purifier,
Jet photometer of acetylene,
Joint-making in generators,
pipes,

K

Keller and Knappich burner,
Keppeler, lead chromate in acagine,
Keppeler, purification,
silicon in acetylene,
test-papers,
See also Eitner
Kerosene. See Paraffin oil
Klinger, vent-pipes,
Knappich burner,
Kona burner,
Konette cycle-lamp burner,

L

La Belle boiling ring,
Labour required in acetylene lighting,
Lagging for generators,
Lamps for generator sheds
paraffin,

Page 470

portable,
acetone process for,
Landolt-Börnstein, solubility of acetylene in water,
Landriset. See Rossel
Lantern, optical, illumination of,
Latent heat,
Lead chromate in bleaching-powder,
objection to, in generators,
pipes for acetylene,
salts in bleaching-powder,
wire, &c., for faced joints,
Leakage of acetylene,
Leaks, search for,
Le Chatelier, explosive limits,
temperature of acetylene flame,
thermo-couple
Leduc, specific gravity of acetylene,
Lépinay, acetylene for engines,
Level alteration and pressure in mains,
Lewes, ammonia in crude acetylene,
blocking of burners,
haze,
heat of decomposition of carbide,
production in generators,
illuminating power of acetylene,
phosphorus in crude acetylene,
polymerisation of acetylene,
presence of hydrogen and carbon monoxide in acetylene,
reaction between carbide and calcium hydroxide,
silicon in crude acetylene,
temperature of acetylene flame,
Lewes and Brame, manganese carbide,
Lidholm, estimation of phosphine,
Lifebuoys, acetylene for,
Lifetime of burners,
mantles,
Lifting power of acetylene in holders,
Light, acetylene as a standard of,
colour of acetylene, incandescent,
self-luminous,
evolution of, in flames,
from acetylene, production of,
transmission of through fog,
Lights, single, disadvantages of,
strong and weak, comparison between,
Lighthouse illumination,
Lighting by acetylene, scope of,
of generator sheds,

Page 471

Lime dust in acetylene,
reaction with sodium carbonate,
sludge. See Residues
solubility of, in sugar solutions,
water, solubility of gas in,
Lime-light, acetylene for the,
Limits, explosive, of acetylene,
Lindé-air,
Linseed oil for acetylene joints,
Liquid acetylene, properties of,
condensation in pipes,
in holder-seals and pressure,
in pressure-gauge,
Liquids, corrosive action of, on metals,
for seals,
purification by,
solubility of acetylene in,
Locomotive lighting,
Loss of gas in generators,
of pressure in holders,
in mains,
in purifiers,
on distribution,
Love, enrichment by acetylene,
Lubricating oil for seals,
Luminous burners. See Burners, self-luminous
Lunge and Cedercreutz, determination of phosphorus in
acetylene,
purification,
Luta burner,
Lutes for holders. See Seals

M

Mahler, temperature of flames,
Mai and Freund, copper acetylide,
Mains, deposition of liquid in,
diameter of, and explosive limits,
dimensions of,
escapes from,
friction in,
laying of,
lead,
quality of,

Page 472

removing air from,
testing of,
Make of acetylene from carbide,
in generators,
Manchester burners,
Maneuvrier and Fournier, specific heat of acetylene,
Manganese carbide,
Mantles for acetylene,
Manure for generator protection,
Manurial value of generator residue,
Maquenne. See Bullier
Marsh gas, enrichment with acetylene,
formed from acetylene,
Matignon. See Berthelot,
Mauricheau-Beaupré, épurène,
estimation of phosphine,
frothing in generators,
phosphine in acetylene,
silicon in acetylene,
Mechanism for automatic generators,
Mercaptans in acetylene,
Mercuric chloride purifier,
test for phosphorus,
Merck test-papers,
Metals for generators,
gauge of,
Meters for acetylene,
Methane, enrichment with acetylene,
formed from acetylene,
ignition temperature of,
Methylated spirit for generators,
for holder seals,
Meyer and Münch, ignition temperatures,
Mildew in vines, use of acetylene in,
Milk of lime, solubility of acetylene in,
Mineral oil for lighting. (See Paraffin oil)
for seals,
Miner's lamp for generator sheds,
Mist, transmission of light through,
Mixter, thermo-chemical data,
Mixtures of acetylene and air,
illuminating duty of,
Moisture, effect of, on carbide,
in acetylene,
Molecular volume of acetylene,
weight of acetylene,
weights, various,
Molet-Boistelle acetylene-air mixture,

Page 473

Morel, formula for acetylene pipes,
sodium plumbate purifier,
specific heat of acetylene,
of carbide,
Mosquitoes, destruction of,
Moths, catching of,
Motion of fluids in pipes,
Motors, acetylene for,
Münch. See Meyer
Münsterberg, acetylene flame,
Mustard, oil of,

N

Naphey burners,
Naphthalene, formation of, from acetylene,
Neuberg, illuminating power of acetylene,
radiant efficiency of acetylene,
Nieuwland, mixtures of acetylene and chlorine,
Nichols, illuminating power of acetylene after storage,
temperature of acetylene flame,
Nickel and acetylene, reactions between,
Nipples, burner, materials for,
Nitrides in carbide,
Nitrogen in flames, effect of,
Non-automatic generators. See Generators (non-automatic)
Non-luminous acetylene flame, appearance of,
burners. See Burners (atmospheric)
Non-return valves,

O

O. C. A. burner,
Odour of acetylene,
Oil, action of, on carbide,
castor, for acetylene joints,
in generators,
in residues,
in seals,
linseed, for acetylene joints,

Page 474

mustard,
olive, for seals,
(See also Paraffin oil)
Olive oil for seals,
Oil-gas, enrichment of,
Optical efficiency of acetylene,
Orders in Council, air in acetylene,
compression of absorbed acetylene,
acetylene-oil-gas,
neat acetylene,
Origin of petroleum,
Orka burner,
Ortloff, friction of acetylene,
Overheating in generators,
See also Polymerisation
Oxide of iron purifier,
Oxy-acetylene blowpipe,
Oxygen required for combustion of acetylene,
of benzene,
combustion of acetylene with,
flames burning in,

P

Paint, cause of frothing in generators,
gas-fitters',
Paraffin oil,
action of, on carbide,
flash-point of,
illuminating power of,
in residues,
lamps,
lighting, effect of on air,
heat developed by,
quality of different grades of,
use of in automatic generators,
seals,
Paraffin wax, treatment of carbide with,
Partial pressure,
Pendants, water-slide for acetylene,
Petroleum oil. See Paraffin oil
spirit, addition of, to generator water,
composition of,
for carburetted acetylene,

Page 475

spirits, nomenclature of,
theory of origin of,
Pfeiffer, purifier,
Pfleger, puratylene,
Phenol, production of, from acetylene,
Phôs burners,
Phosphine, cause of deposit at burner orifices,
composition of,
in crude acetylene,
amount of,
toxicity of,
Phosphoretted hydrogen. See Phosphine
Phosphorus and incandescent mantles,
"compounds,"
in crude acetylene,
in purified acetylene,
detection and determination of,
removal of,
"Phossy-jaw,"
Photometer, jet of acetylene,
Phylloxera, use of acetylene for,
Physical properties of acetylene,
Pickering, freezing-points of calcium chloride solutions,
Pictet, freezing-points of dilute alcohol,
purification of acetylene,
Pintsch burners,
Pipes, blow-off. See Vent-pipes
diameter of, and explosive limits,
vent. See Vent-pipes (See also Mains)
Plant, acetylene, fire risks of,
order of items in,
Platinum in burners,
Poisonous nature of acetylene,
Pole, motion of fluids in pipes,
pressure thrown by holders,
Polymerisation, definition of,
of acetylene,
See also Overheating
Porous matter, absorption of acetylene in,
Portable lamps,
acetone process for,
temperature in,
Potassium bichromate purifier,
hydroxide purifier,
permanganate purifier,
Power from acetylene, production of,
Precautions with generators,
with new installations,

Page 476

Presence of moisture in acetylene,
Pressure and leakage,
after explosions of acetylene,
atmospheric,
automatic generators working by,
correction of gas volumes for,
critical, of acetylene,
definition of (gas),
for incandescent burners,
self-luminous burners,
gauge,
liquid for,
given by displacement holders,
rising holders,
in generators,
utilisation of,
in mains and pipes,
in purifiers, loss of,
irregular, caused by vent-pipes,
maximum safe, for acetylene,
necessity for regular,
partial,
regulators. See Governors
Protection of generators from frost,
holders from frost,
Puratylene,
Purchase of a generator,
carbide, regulations as to,
Purification by liquids and solids,
in portable lamps,
necessary extent of,
reasons for,
regulations as to,
speed of,
Purified acetylene, chlorine in,
hydrochloric acid in,
phosphorus in,
sulphur in,
Purifiers and holder, relative positions of,
construction of,
duplication of,
exhaustion of,
foul, emptying of,
loss of pressure in,
mechanical, for acetylene,
Purifying materials, density of,
efficiency of,
quantity required,

Page 477

Pyralid, destruction of the,

Q

Quality of carbide, regulations as to,
Quicklime. See Calcium oxide

R

Radiant efficiency of acetylene,
heat,
Railway lighting by acetylene,
Ramie mantles for acetylene,
Range of explosibility, meaning of term,
of acetylene,
Rat-tail burner,
Reactions between copper and acetylene,
chemical, of acetylene,
physical, of acetylene,
Reaction grids in generators,
Read and Jacobs. See Bradley
Rod lead for acetylene joints,
Regulations, American (National Board of Fire Underwriters of
U.S.A.),
Austrian Acetylene Association,
Government,
British Acetylene Association,
Fire Offices Committee,
Home Office Committee (1901),
for analysis of carbide,
for construction of generating plant,
for generators,
for purification,
for sale and purchase of carbide,
for sampling carbide,
for storing carbide,
French (Conseil d'Hygiène de la Seine),
German Acetylene Association,
Hungarian Government,
Italian Government,

Page 478

Residue from dry process of generation,
Residues, carbide in,
colour of,
composition of,
consistency of,
disposal of,
containing oil,
manurial value of,
utilisation of,
Respiration of acetylene,
Reversibility of reaction between calcium oxide and water,
Reychler. See Bergé
Rising holders. See Holders (rising)
Rossel and Landriset, ammonia in crude acetylene,
purifier,
sulphur in crude acetylene,
Roofs over exposed holders,
Rooms, amount of illumination required in,
Rubber tubes for acetylene,
Ruby for burners,
Rules. See Regulations

S

Safety lamp, Davy's, for generator sheds,
valves. See Vent-pipes
Sale of carbide, regulations as to,
Salt, common, in holder-seals,
Salzbergwerk Neu Stassfurt, production of tetrachlorethane,
Sampling carbide,
Sandmann. See Hammerschmidt
Sansair burner,
Saulmann. See Caro
Sawdust in bleaching-powder,
Scale, water, in generators,
Scented carbide,
Schiff. See Fuchs
Schimek burner,
Schwander, carburetted acetylene,
Schwarz burners,
Seal-pots,
Seals (holder). See Holder-seals
Seams in generator-making,
Self-luminous burners. See Burners (self-luminous)

Page 479

Sensible heat,
Separation of holder from generator,
Service-pipes. See Mains
Shoot generators,
Silicon compounds,
in acetylene,
in carbide,
Sirius burner,
Slaked lime. See Calcium hydroxide
Sludge. See Residues
Sludge-cocks, automatic locking of,
Sludge-pipes, blocked, clearance of,
Smell of crude and purified acetylene,
Smith, purification,
Smoke, production of, by flames,
Smoking, danger of, in generator sheds,
Soap, use of, in testing pipes,
Soda, washing, for decomposing carbide,
Sodium acetate solution for generator jackets,
Sodium carbonate and lime, reaction between,
crystallised, for decomposing carbide,
chloride for holder-seals,
solubility of acetylene in,
hypochlorite purifier,
plumbate purifier,
sulphate in bleaching-powder,
Soil, carbide residues as dressing for,
Solder in generators,
Soldering, autogenous,
Solids containing water, decomposition of carbide by,
purification by,
Solubility of acetylene,
in generators,
in holders,
in liquids,
Soot, production by, of flames,
Space occupied by purifying materials,
Sparks from steel tools, danger of,
Specific gravity and holder pressure,
leakage,
of acetylene, dissolved,
gaseous,
liquid,
of air,
of carbide,
of gases, and burner construction,
of water,
heat of acetylene,

Page 480

of carbide,
heats, various,
intensity. See Intensity, specific
Speed of reactions between carbide, water, and calcium
hydroxide,
of purification,
Spent lime. See Residues
Spontaneous inflammability,
Spraying apparatus,
Stable manure for warming generators,
Stadelmann burners,
Standard of illumination in rooms,
of light, acetylene as,
Steam, latent heat of, use of,
specific heat of,
reaction between carbide and,
Steam-barrel for acetylene mains,
Steatite for burners,
Steel, heat-conducting power of,
tools, danger of
Sterilisation of air by flames,
Stewart and Hoxie, radiant efficiency of acetylene,
Storage regulations for carbide,
vessels for carbide, temporary,
Styrolene. formation of, from acetylene,
Suckert. See Willson
Suffocation by acetylene,
Sugar solutions, solubility of lime in,
Sulphur "compounds,"
in coal-gas,
in crude acetylene,
in purified acetylene,
removal of,
Sulphuretted hydrogen, solubility of, in water,
toxicity of,
Sulphuric acid and acetylene, reactions between
as purifying material,
Superficial area in purifiers,
Supply of water to automatic generators,
Suprenia burners,
Swelling of carbide during decomposition,
Symbols, chemical, meaning of,
Syphons for removing water,

T

Page 481

Table-lamps, acetone process for,
Tabular numbers,
Tanks for rising holders, construction of,
"Tantalus Cup,"
Taps for acetylene pipes,
Tar, cause of frothing in generators,
Tarry matter in generators,
Telescopic gasholders. See Holder (rising)
Temperature and heat, difference between,
correction of volumes for,
critical, of acetylene,
high, effect of, on acetylene. See Polymerization
of acetylene blowpipe,
flame,
of dissociation of acetylene,
of ignition of acetylene,
various gases,
of reaction between carbide and calcium hydroxide,
between carbide and water,
Temperatures in generators,
calculation of,
determination of,
Tension of liquid acetylene,
Test-papers,
Tetrachlorethane, production of,
Tetrachloride, acetylene, production of,
Thawing of frozen apparatus,
Thermo-chemical data,
Thermo-couple, Le Chatelier's,
Thomson, radiant efficiency of acetylene,
thermo-chemical data,
Tools, steel or iron, danger of,
Town supplies,
Toxicity of acetylene,
of sulphur and phosphorus compounds,
Train-lighting by acetylene,
Treated carbide. See Calcium carbide (treated)
Trondol burner,
Tubes, diameter of, and explosive limits,
Tubes for acetylene. See Mains
Tubing, flexible, for acetylene,
Typical generators,

U

Page 482

Ullmax purifier,
Unaccounted-for gas,
Underwriters, United States Fire,
United States. See America
Uses, sundry, for acetylene,

V

Valuation of carbide,
Value of acetylene, hygienic,
enriching,
pecuniary,
of purifying materials,
Valves, screw-down, for generators,
Vapour, water, in acetylene, objections to,
removal of,
value of,
Vehicular lamps,
Ventilation of generator sheds,
Vent-pipes, economy of,
for carbide vessels,
generators,
holders,
noise in,
position of mouths of,
size of,
Vibration and incandescent lighting,
Vieille, dissolved acetylene,
Vigouroux, silicon in acetylene,
Village installations, mains for,
leakage in,
supplies,
Villard, liquid acetylene,
Vines, treatment by acetylene of, for mildew and phylloxera,
Violle and Féry, acetylene as standard of light,
Vitiation of air by flames,
Volume, alteration of, on dissociation,
and weight of acetylene,
molecular, of acetylene,
Volume of acetylene passing through pipes,
Volumes, gas, correction for temperature and pressure,

Page 483

W

Washers, oil,
water,
Waste-pipes of generators,
Water and calcium oxide, reaction between,
and carbide, heat of reaction between,
boiling-point, evolution of gas at,
condensation of, in pipes,
consumption of, in generators,
convection currents in,
freezing-point, evolution of gas at,
heat absorbed in warming,
conducting power of,
of formation of,
in excess, generators with,
in holders, freezing of,
use for decomposition,
use for washing,
jackets for generators,
quality of, for portable generators,
quantity required in carbide-to-water generators,
scale in generators,
solubility of acetylene in,
of impurities in,
of load in,
specific gravity of,
supply for automatic generators,
non-automatic generators,
yield of gas per unit of,
Water-gas, enrichment with acetylene,
Water-seals, as not-return valves,
setting water-level in,
Water-slide pendants for acetylene,
Water-soluble impurities in acetylene,
See also Ammonia and Sulphuretted hydrogen
Water-to-carbide generators. See Generators (water-to-carbide)
Water-vapour, dissociation of,
existence of, at low temperatures,
in acetylene, objections to,
removal of,
value of,
reaction between carbide and,

Page 484

Weber burner,
Wedding, enrichment of coal-gas,
Weed-killer, carbide residues as,
Weight and volume of acetylene,
Weights, atomic,
molecular,
Welding, acetylene,
White lead, for acetylene joints,
Wiener burners,
Willgerodt, purification,
Willson and Suckert, liquid acetylene,
Windows in generator sheds,
Winter, manipulation of generators during,
Wöhler, addition of chlorine to acetylene,
Wolff, acetone in acetylene,
illuminating power of acetylene,
purifier,
silicon in acetylene,
Wonder burner,
Work done in actuating automatic generators,

Y

Yield of gas, deficient, cause of,
from carbide,
determining,
(British standard),
(German standard),
from water,

Z

Zenith burner,

Page 485

INDEX TO APPENDIX

A

"A" Generator (of Braby and Co., Ltd.),
"A1" generator (of Acetylene Corporation of Great Britain),
"A-to-Z" generator (of Acetylene Corporation of Great Britain),
Acetylene Corporation of Great Britain,
Acetylene Gas and Carbide of Calcium Co.,
Acetylene Illuminating Co., Ltd.,
"Acetylite" generator,
"Acétylithe" generator,
Acétylithe, Soc. An. de l',
Allen Co.,
"Allen" Flexible-tube generator,
"Allen" purifying material,
American generators,
Applications de l'Acétylène, La Soc. des.,
Austrian generator,
Automatic generators,

B

"B" generator (of Braby and Co., Ltd.),
Belgian generators,
Bon Accord Acetylene Gas Co.,
"Bon Accord" generator,
Braby, Frederick and Co., Ltd.,
British generators,

C

Page 486

Canadian generators,
Carbide-to-water generators,
"Carburlen" purifying material,
Chloride of lime purifying material,
Colt Co., J. G.,
"Colt" generator,
Compartment, flooded, generator,
Contact generators,
Cork waste and wadding purifying material,
"Corporation Flexible Tube Generator,"
"Curaze" purifying material,

D

"Dargue" generator,
Dargue Acetylene Gas Co.,
Davis Acetylene Co.,
"Davis" generator,
Debruyne, L.,
Debruyne's generators,
Drawer generators,
Drip generator,
Drummond, J. and J.,

E

English generators,

F

Flooded compartment generator,
Fittings, Ltd.,
Frankoline purifying material,
French generators,

Page 487

G

German generators,

H

Heratol, purifying material,

I

"Incanto" generator,
Irish generator,

J

"Javal" generator,

K

Keller and Knappich, G.m.b.H.,
"Klenzal" purifying material,
Klinger, Rich.,
Klinger's generator,
"Knappich" generator,

L

Page 488

"L'Éclair" generator,
"L'Étoile" generator,
L'Hermite,
Lockerbie and Wilkinson,

M

Manchester Acetylene Gas Col., Ltd.,
Mangiameli, Fr. and Co.,
Moss, R. J. and Sons,
"Semi-Non-Auto" generator,
"Type A" generator,
"Type B" generator,
"Type C" generator,
Moyes Wm., and Sons,

N

Non-automatic generators,
Nordische Azetylen Industrie,

O

"Omega" generator,
Overberge, De Smet van,
"Owens" generator,
"Owens" purifying material,

P

Page 489

Phôs Co.,
"Phôs Type E" generator,
"Photolithe" generator,
Photolithe, Soc. An. Belg de la,
Pumice purifying material,
Puratylene purifying material,
Purifying material, "Allen,"
"Carburylen,"
chloride of lime,
coke and cotton, chemically treated,
cork waste and wadding,
"Curaze,"
frankoline,
heratol,
"Klenzal,"
"Owens,"
pumice,
puratylene,
"Roscoline,"
"Standard,"
"Thorlite,"

R

Rosco Acetylene Co.,
"Rosco" generator,
"Roscoline" purifying material,
Rural Districts Gas Light Co.,

S

St. James' Illuminating Co., Ltd.,
Scotch generators,
Semi-automatic generator,
Siche Gas Co., Ltd.,
"Siche" generator,
"Signal-Arm" generator,
"Sirius" generator,
Sirius, Maison,

Page 490

Standard Acetylene Co.,
"Standard" purifying material,
Sunlight Gas Machine Co.,
Superposed pans or trays,

T

"Thorlite" generator,
purifying material,
Thorn and Hoddle Co.,
"Thorscar" generator,
Trays, superposed,

U

United States generators,

W

Wadding and cork waste purifying material,
Water-to-carbide generators,
Weldhen and Bleriot,
Welsh generator,
"Westminster" generator,

Page 491

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