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Title: The handbook of soap manufacture

Author: W. H. Simmons
H. A. Appleton

Release date: June 7, 2007 [eBook #21724]
Most recently updated: January 2, 2021

Language: English

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*** START OF THE PROJECT GUTENBERG EBOOK THE HANDBOOK
OF SOAP MANUFACTURE ***

THE HANDBOOK OF

SOAP MANUFACTURE
BY

W. H. SIMMONS, B.Sc. (Lond.), F.C.S.
AND

H. A. APPLETON
WITH TWENTY-SEVEN ILLUSTRATIONS
LONDON
SCOTT, GREENWOOD & SON
"THE OIL AND COLOUR TRADES JOURNAL" OFFICES
8 BROADWAY, LUDGATE HILL, E.C.
1908
[All rights reserved]

Transcriber's note:
Footnotes have been moved to the end of the chapter and minor typos have
been corrected.

PREFACE
In the general advance of technical knowledge and research during the last
decade, the Soap Industry has not remained stationary. While there has not
perhaps been anything of a very revolutionary character, steady progress has
still been made in practically all branches, and the aim of the present work is to
describe the manufacture of Household and Toilet Soaps as carried out to-day
in an up-to-date and well-equipped factory.
In the more scientific portions of the book, an acquaintance with the principles
of elementary chemistry is assumed, and in this we feel justified, as in these
days of strenuous competition, no soap-maker can hope to compete
successfully with his rivals unless he has a sound theoretical as well as
practical knowledge of the nature of the raw materials he uses, and the
reactions taking place in the pan, or at other stages of the manufacture. We also
venture to hope that the work may prove useful to Works' Chemists and other
Analysts consulted in connection with this Industry.
At the same time, in the greater part of the book no chemical knowledge is
necessary, the subject being treated in such a way that it is hoped those who
are not directly engaged in the manufacture of soap, but who desire a general
idea of the subject, will find it of value.
In the sections dealing with the composition and analysis of materials,
temperatures are expressed in degrees Centigrade, these being now almost
invariably used in scientific work. In the rest of the book, however, they are
given in degrees Fahrenheit (the degrees Centigrade being also added in
brackets), as in the majority of factories these are still used.
As regards strengths of solution, in some factories the use of Baumé degrees is
preferred, whilst in others Twaddell degrees are the custom, and we have
therefore given the two figures in all cases.
In the chapter dealing with Oils and Fats, their Saponification Equivalents are
given in preference to Saponification Values, as it has been our practice for
some years to express our results in this way, as suggested by Allen in

Commercial Organic Analysis, and all our records, from which most of the
figures for the chief oils and fats are taken, are so stated.
For the illustrations, the authors are indebted to Messrs. E. Forshaw & Son,
Ltd., H. D. Morgan, and W. J. Fraser & Co., Ltd.
W. H. S.
H. A. A.

London, September, 1908.

CONTENTS
PAGE

CHAPTER I.

Introduction. 1

Definition of Soap—Properties—Hydrolysis—Detergent Action.

CHAPTER II.

Constitution of Oils and Fats, and their Saponification 6

Researches of Chevreul and Berthelot—Mixed Glycerides—Modern Theories
of Saponification—Hydrolysis accelerated by (1) Heat or Electricity, (2)
Ferments, Castor-seed Ferment, Steapsin, Emulsin, and (3) Chemical
Reagents, Sulphuric Acid, Twitchell's Reagent, Hydrochloric Acid, Lime,
Magnesia, Zinc Oxide, Soda and Potash.

CHAPTER III.

Raw Materials used in Soap-making 24

Fats and Oils—Waste Fats—Fatty Acids—Less-known Oils and Fats of
Limited Use—Various New Fats and Oils Suggested for Soap-making—Rosin
—Alkali (Caustic and Carbonated)—Water—Salt—Soap-stock.

CHAPTER IV.

Bleaching and Treatment of Raw Materials intended for Soap-making 41

Palm Oil—Cotton-seed Oil—Cotton-seed "Foots"—Vegetable Oils—Animal
Fats—Bone Fat—Rosin.

CHAPTER V.

Soap-making 45

Classification of Soaps—Direct combination of Fatty Acids with Alkali—Cold
Process Soaps—Saponification under Increased or Diminished Pressure—Soft
Soap—Marine Soap—Hydrated Soaps, Smooth and Marbled—Pasting or
Saponification—Graining Out—Boiling on Strength—Fitting—Curd Soaps—
Curd Mottled—Blue and Grey Mottled Soaps—Milling Base—Yellow
Household Soaps—Resting of Pans and Settling of Soap—Utilisation of
Nigres—Transparent soaps—Saponifying Mineral Oil—Electrical Production
of Soap.

CHAPTER VI.

Treatment of Settled Soap 60

Cleansing—Crutching—Liquoring of Soaps—Filling—Neutralising,
Colouring and Perfuming—Disinfectant Soaps—Framing—Slabbing—
Barring—Open and Close Piling—Drying—Stamping—Cooling.

CHAPTER VII.

Toilet, Textile and Miscellaneous Soaps 77

Toilet Soaps—Cold Process soaps—Settled Boiled Soaps—Remelted Soaps—
Milled Soaps—Drying—Milling and Incorporating Colour, Perfume, or
Medicament—Perfume—Colouring matter—Neutralising and Superfatting
Material—Compressing—Cutting—Stamping—Medicated Soaps—Ether
Soap—Floating Soaps—Shaving Soaps—Textile Soaps—Soaps for Woollen,
Cotton and Silk Industries—Patent Textile Soaps—Miscellaneous Soaps.

CHAPTER VIII.

Soap Perfumes 95

Essential Oils—Source and Preparation—Properties—Artificial and Synthetic
Perfumes.

CHAPTER IX.

Glycerine Manufacture and Purification 111

Treatment of Lyes—Evaporation to Crude Glycerine—Distillation—Distilled
and Dynamite Glycerine—Chemically Pure Glycerine—Animal Charcoal for
Decolorisation—Glycerine obtained by other methods of Saponification—
Yield of Glycerine from Fats and Oils.

CHAPTER X.

Analysis of Raw Materials, Soap, and Glycerine 117

Fats and Oils—Alkalies and Alkali Salts—Essential Oils—Soap—Lyes—
Crude Glycerine.

CHAPTER XI.

Statistics of the Soap Industry 140

APPENDIX A.

Comparison of Degrees, Twaddell and Baumé, with Actual Densities 147

APPENDIX B.

Comparison of Different Thermometric Scales 148

APPENDIX C.

Table of the Specific Gravities of Solutions of Caustic Soda 149

APPENDIX D.

Table of Strength of Caustic Potash Solutions at 60° F. 151

Index 153

CHAPTER I.
INTRODUCTION.

Definition of Soap—Properties—Hydrolysis—Detergent Action.
It has been said that the use of soap is a gauge of the civilisation of a nation,
but though this may perhaps be in a great measure correct at the present day,
the use of soap has not always been co-existent with civilisation, for according
to Pliny (Nat. Hist., xxviii., 12, 51) soap was first introduced into Rome from
Germany, having been discovered by the Gauls, who used the product obtained
by mixing goats' tallow and beech ash for giving a bright hue to the hair. In
West Central Africa, moreover, the natives, especially the Fanti race, have been
accustomed to wash themselves with soap prepared by mixing crude palm oil
and water with the ashes of banana and plantain skins. The manufacture of
soap seems to have flourished during the eighth century in Italy and Spain, and
was introduced into France some five hundred years later, when factories were
established at Marseilles for the manufacture of olive-oil soap. Soap does not
appear to have been made in England until the fourteenth century, and the first
record of soap manufacture in London is in 1524. From this time till the
beginning of the nineteenth century the manufacture of soap developed very
slowly, being essentially carried on by rule-of-thumb methods, but the classic
researches of Chevreul on the constitution of fats at once placed the industry
upon a scientific basis, and stimulated by Leblanc's discovery of a process for
the commercial manufacture of caustic soda from common salt, the production
of soap has advanced by leaps and bounds until it is now one of the most
important of British industries.
Definition of Soap.—The word soap (Latin sapo, which is cognate with Latin
sebum, tallow) appears to have been originally applied to the product obtained
by treating tallow with ashes. In its strictly chemical sense it refers to
combinations of fatty acids with metallic bases, a definition which includes not
only sodium stearate, oleate and palmitate, which form the bulk of the soaps of
commerce, but also the linoleates of lead, manganese, etc., used as driers, and
various pharmaceutical preparations, e.g., mercury oleate (Hydrargyri
oleatum), zinc oleate and lead plaster, together with a number of other metallic

salts of fatty acids. Technically speaking, however, the meaning of the term
soap is considerably restricted, being generally limited to the combinations of
fatty acids and alkalies, obtained by treating various animal or vegetable fatty
matters, or the fatty acids derived therefrom, with soda or potash, the former
giving hard soaps, the latter soft soaps.
The use of ammonia as an alkali for soap-making purposes has often been
attempted, but owing to the ease with which the resultant soap is decomposed,
it can scarcely be looked upon as a product of much commercial value.
H. Jackson has, however, recently patented (Eng. Pat. 6,712, 1906) the use of
ammonium oleate for laundry work. This detergent is prepared in the wash-tub
at the time of use, and it is claimed that goods are cleansed by merely
immersing them in this solution for a short time and rinsing in fresh water.
Neither of the definitions given above includes the sodium and potassium salts
of rosin, commonly called rosin soap, for the acid constituents of rosin have
been shown to be aromatic, but in view of the analogous properties of these
resinates to true soap, they are generally regarded as legitimate constituents of
soap, having been used in Great Britain since 1827, and receiving legislative
sanction in Holland in 1875.
Other definitions of soap have been given, based not upon its composition, but
upon its properties, among which may be mentioned that of Kingzett, who says
that "Soap, considered commercially, is a body which on treatment with water
liberates alkali," and that of Nuttall, who defines soap as "an alkaline or
unctuous substance used in washing and cleansing".
Properties of Soap.—Both soda and potash soaps are readily soluble in either
alcohol or hot water. In cold water they dissolve more slowly, and owing to
slight decomposition, due to hydrolysis (vide infra), the solution becomes
distinctly turbid. Sodium oleate is peculiar in not undergoing hydrolysis except
in very dilute solution and at a low temperature. On cooling a hot soap
solution, a jelly of more or less firm consistence results, a property possessed
by colloidal bodies, such as starch and gelatine, in contradistinction to
substances which under the same conditions deposit crystals, due to
diminished solubility of the salt at a lower temperature.
Krafft (Journ. Soc. Chem. Ind., 1896, 206, 601; 1899, 691; and 1902, 1301)
and his collaborators, Wiglow, Strutz and Funcke, have investigated this
property of soap solutions very fully, the researches extending over several

years. In the light of their more recent work, the molecules, or definite
aggregates of molecules, of solutions which become gelatinous on cooling
move much more slowly than the molecules in the formation of a crystal, but
there is a definite structure, although arranged differently to that of a crystal. In
the case of soda soaps the colloidal character increases with the molecular
weight of the fatty acids.
Soda soaps are insoluble in concentrated caustic lyes, and, for the most part, in
strong solutions of sodium chloride, hence the addition of caustic soda or brine
to a solution of soda soap causes the soap to separate out and rise to the
surface. Addition of brine to a solution of potash soap, on the other hand,
merely results in double decomposition, soda soap and potassium chloride
being formed, thus:—

C17H35COOK + NaCl = C17H35COONa + KCl
potassium stearate sodium chloride sodium stearate potassium chloride

The solubility of the different soaps in salt solution varies very considerably.
Whilst sodium stearate is insoluble in a 5 per cent. solution of sodium chloride,
sodium laurate requires a 17 per cent. solution to precipitate it, and sodium
caproate is not thrown out of solution even by a saturated solution.
Hydrolysis of Soap.—The term "hydrolysis" is applied to any resolution of a
body into its constituents where the decomposition is brought about by the
action of water, hence when soap is treated with cold water, it is said to
undergo hydrolysis, the reaction taking place being represented in its simplest
form by the equation:—

2NaC18H35O2 + H2O = NaOH + HNa(C18H35O2)2
sodium stearate water caustic soda acid sodium stearate

The actual reaction which occurs has been the subject of investigation by many
chemists, and very diverse conclusions have been arrived at. Chevreul, the
pioneer in the modern chemistry of oils and fats, found that a small amount of
alkali was liberated, as appears in the above equation, together with the
formation of an acid salt, a very minute quantity of free fatty acid remaining in
solution. Rotondi (Journ. Soc. Chem. Ind., 1885, 601), on the other hand,
considered that a neutral soap, on being dissolved in water, was resolved into a
basic and an acid salt, the former readily soluble in both hot and cold water,

the latter insoluble in cold water, and only slightly soluble in hot water. He
appears, however, to have been misled by the fact that sodium oleate is readily
soluble in cold water, and his views have been shown to be incorrect by Krafft
and Stern (Ber. d. Chem. Ges., 1894, 1747 and 1755), who from experiments
with pure sodium palmitate and stearate entirely confirm the conclusions
arrived at by Chevreul.
The extent of dissociation occurring when a soap is dissolved in water depends
upon the nature of the fatty acids from which the soap is made, and also on the
concentration of the solution. The sodium salts of cocoa-nut fatty acids (capric,
caproic and caprylic acids) are by far the most easily hydrolysed, those of oleic
acid and the fatty acids from cotton-seed oil being dissociated more readily
than those of stearic acid and tallow fatty acids. The decomposition increases
with the amount of water employed.
The hydrolytic action of water on soap is affected very considerably by the
presence of certain substances dissolved in the water, particularly salts of
calcium and magnesium. Caustic soda exerts a marked retarding effect on the
hydrolysis, as do also ethyl and amyl alcohols and glycerol.
Detergent Action of Soap.—The property possessed by soap of removing dirt
is one which it is difficult to satisfactorily explain. Many theories, more or less
complicated, have been suggested, but even now the question cannot be
regarded as solved.
The explanation commonly accepted is that the alkali liberated by hydrolysis
attacks any greasy matter on the surface to be cleansed, and, as the fat is
dissolved, the particles of dirt are loosened and easily washed off. Berzelius
held this view, and considered that the value of a soap depended upon the ease
with which it yielded free alkali on solution in water.
This theory is considered by Hillyer (Journ. Amer. Chem. Soc., 1903, 524),
however, to be quite illogical, for, as he points out, the liberated alkali would
be far more likely to recombine with the acid or acid salt from which it has
been separated, than to saponify a neutral glyceride, while, further,
unsaponifiable greasy matter is removed by soap as easily as saponifiable fat,
and there can be no question of any chemical action of the free alkali in its
case. Yet another argument against the theory is that hydrolysis is greater in
cold and dilute solutions, whereas hot concentrated soap solutions are
generally regarded as having the best detergent action.

Rotondi (Journ. Soc. Chem. Ind., 1885, 601) was of the opinion that the basic
soap, which he believed to be formed by hydrolysis, was alone responsible for
the detergent action of soap, this basic soap dissolving fatty matter by
saponification, but, as already pointed out, his theory of the formation of a
basic soap is now known to be incorrect, and his conclusions are therefore
invalid.
Several explanations have been suggested, based on the purely physical
properties of soap solutions. Most of these are probably, at any rate in part,
correct, and there can be little doubt that the ultimate solution of the problem
lies in this direction, and that the detergent action of soap will be found to
depend on many of these properties, together with other factors not yet known.
Jevons in 1878 in some researches on the "Brownian movement" or "pedesis"
of small particles, a movement of the particles which is observed to take place
when clay, iron oxide, or other finely divided insoluble matter is suspended in
water, found that the pedetic action was considerably increased by soap and
sodium silicate, and suggested that to this action of soap might be attributed
much of its cleansing power.
Alder Wright considered that the alkali liberated by hydrolysis in some way
promoted contact of the water with the substance to be cleansed, and Knapp
regarded the property of soap solutions themselves to facilitate contact of the
water with the dirt, as one of the chief causes of the efficacy of soap as a
detergent.
Another way in which it has been suggested that soap acts as a cleanser is that
the soap itself or the alkali set free by hydrolysis serves as a lubricant, making
the dirt less adherent, and thus promoting its removal.
The most likely theory yet advanced is that based on the emulsifying power of
soap solutions. The fact that these will readily form emulsions with oils has
long been known, and the detergent action of soap has frequently been
attributed to it, the explanation given being that the alkali set free by the water
emulsifies the fatty matter always adhering to dirt, and carries it away in
suspension with the other impurities. Experiments by Hillyer (loc. cit.) show,
however, that while N/10 solution of alkali will readily emulsify a cotton-seed
oil containing free acidity, no emulsion is produced with an oil from which all
the acidity has been removed, or with kerosene, whereas a N/10 solution of

sodium oleate will readily give an emulsion with either, thus proving that the
emulsification is due to the soap itself, and not to the alkali.
Plateau (Pogg. Ann., 141, 44) and Quincke (Wiedmann's. Ann., 35, 592) have
made very complete researches on the emulsification and foaming of liquids
and on the formation of bubbles. The former considers that there are two
properties of a liquid which play an important part in the phenomenon, (1) it
must have considerable viscosity, and (2) its surface tension must be low.
Quincke holds similar views, but considers that no pure liquid will foam.
Soap solution admirably fulfils Plateau's second condition, its surface tension
being only about 40 per cent. of that of water, while its cohesion is also very
small; and it is doubtless to this property that its emulsifying power is chiefly
due. So far as viscosity is concerned, this can have but little influence, for a 1
per cent. solution of sodium oleate, which has a viscosity very little different
from that of pure water, is an excellent emulsifying agent.
Hillyer, to whose work reference has already been made, investigated the
whole question of detergent action very exhaustively, and, as the result of a
very large number of experiments, concludes that the cleansing power of soap
is largely or entirely to be explained by the power which it has of emulsifying
oily substances, of wetting and penetrating into oily textures, and of
lubricating texture and impurities so that these may be removed easily. It is
thought that all these properties may be explained by taking into account the
low cohesion of the soap solutions, and their strong attraction or affinity to oily
matter, which together cause the low surface tension between soap solution
and oil.

CHAPTER II.
CONSTITUTION OF OILS AND FATS, AND THEIR
SAPONIFICATION.

Researches of Chevreul and Berthelot—Mixed Glycerides—
Modern Theories of Saponification—Hydrolysis accelerated by (1)
Heat or Electricity, (2) Ferments; Castor-seed Ferment, Steapsin,
Emulsin, and (3) Chemical Reagents; Sulphuric Acid, Twitchell's
Reagent, Hydrochloric Acid, Lime, Magnesia, Zinc Oxide, Soda
and Potash.
The term oil is of very wide significance, being applied to substances of vastly
different natures, both organic and inorganic, but so far as soap-making
materials are concerned, it may be restricted almost entirely to the products
derived from animal and vegetable sources, though many attempts have been
made during the last few years to also utilise mineral oils for the preparation of
soap. Fats readily become oils on heating beyond their melting points, and may
be regarded as frozen oils.
Although Scheele in 1779 discovered that in the preparation of lead plaster
glycerol is liberated, soap at that time was regarded as a mere mechanical
mixture, and the constitution of oils and fats was not properly understood. It
was Chevreul who showed that the manufacture of soap involved a definite
chemical decomposition of the oil or fat into fatty acid and glycerol, the fatty
acid combining with soda, potash, or other base, to form the soap, and the
glycerol remaining free. The reactions with stearin and palmitin (of which
tallow chiefly consists) and with olein (found largely in olive and cotton-seed
oils) are as follows:—

CH2OOC18H35 CH2OH
| |
CHOOC18H35 + 3NaOH = 3NaOOC18H35 + CHOH
| |
CH2OOC18H35 CH2OH

stearin sodium hydroxide sodium stearate glycerol

CH2OOC16H31 CH2OH
| |
CHOOC16H31 + 3NaOH = 3NaOOC16H31 + CHOH
| |
CH2OOC16H31 CH2OH
palmitin sodium hydroxide sodium palmitate glycerol

CH2OOC18H33 CH2OH
| |
CHOOC18H33 + 3NaOH = 3NaOOC18H33 + CHOH
| |
CH2OOC18H33 CH2OH
olein sodium hydroxide sodium oleate glycerol

Berthelot subsequently confirmed Chevreul's investigations by directly
synthesising the fats from fatty acids and glycerol, the method he adopted
consisting in heating the fatty acids with glycerol in sealed tubes. Thus, for
example:—

3C18H35O2H + C3H5(OH)3 = C3H5(C18H35O2)3
stearic acid glycerol tristearin

Since glycerol is a trihydric alcohol, i.e., contains three hydroxyl (OH) groups,
the hydrogen atoms of which are displaceable by acid radicles, the above
reaction may be supposed to take place in three stages. Thus, we may have:—

(1) C18H35O2H + C3H5(OH)3 = C3H5(OH)2C18H35O2 + H2O
monostearin
(2) C18H35O2H + C3H5(OH)2C18H35O2 = C3H5(OH)(C18H35O2)2 + H2O

distearin
(3) C18H35O2H + C3H5(OH)(C18H35O2)2 = C3H5(C18H35O2)3 + H2O
tristearin

There are two possible forms of monoglyceride and diglyceride, according to
the relative position of the acid radicle, these being termed alpha and beta
respectively, and represented by the following formulæ, where R denotes the
acid radicle:—
Monoglyceride:—

CH2OR CH2OH
| |
(alpha) CHOH and (beta) CHOR
| |
CH2OH CH2OH

Diglyceride:—

CH2OR CH2OR
| |
(alpha) CHOH and (beta) CHOR
| |
CH2OR CH2OH

According to the relative proportions of fatty acid and glycerol used, and the
temperature to which they were heated, Berthelot succeeded in preparing
mono-, di- and triglycerides of various fatty acids.
Practically all the oils and fats used in soap-making consist of mixtures of
these compounds of glycerol with fatty acids, which invariably occur in nature
in the form of triglycerides.
It was formerly considered that the three acid radicles in any naturally
occurring glyceride were identical, corresponding to the formula—
CH2OR
|
CHOR

|
CH2OR

where R denotes the acid radicle. Recent work, however, has shown the
existence of several so-called mixed glycerides, in which the hydroxyls of the
same molecule of glycerol are displaced by two or sometimes three different
acid radicles.
The first mixed glyceride to be discovered was oleodistearin,
C3H5(OC18H35O)(OC18H35O)2, obtained by Heise in 1896 from Mkani fat.
Hansen has since found that tallow contains oleodipalmitin, C3H5(OC18H35O)
(OC16H31O), stearodipalmitin, C3H5(OC18H35O)(OC16H31O),
oleopalmitostearin, C3H5(OC18H33O)(OC16H31O) (OC18H35O) and
palmitodistearin, CH(OC16H31O)(OC18H35O)2, the latter of which has also
been obtained by Kreis and Hafner from lard, while Holde and Stange have
shown that olive oil contains from 1 to 2 per cent. of oleodidaturin,
C3H5(OC18H33O)(OC17H33O)2, and Hehner and Mitchell have obtained
indications of mixed glycerides in linseed oil (which they consider contains a
compound of glycerol with two radicles of linolenic acid and one radicle of
oleic acid), also in cod-liver, cod, whale and shark oils.
In some cases the fatty acids are combined with other bases than glycerol. As
examples may be cited beeswax, containing myricin or myricyl palmitate, and
spermaceti, consisting chiefly of cetin or cetyl palmitate, and herein lies the
essential difference between fats and waxes, but as these substances are not
soap-making materials, though sometimes admixed with soap to accomplish
some special object, they do not require further consideration.
The principal pure triglycerides, with their formulæ and chief constants, are
given in the following table:—

Melting Refractive
Chief Saponification
Glyceride. Formula. Point, Index at
Occurrence. Equivalent.
°C. 60° C.
Liquid at
Butyrin C3H5(O.C4H7O)3 Butter fat 1.42015 100.7
-60
Porpoise,
Isovalerin C3H5(O.C5H9O)3 ... ... 114.7
dolphin

Cocoa-nut
Caproin C3H5(O.C6H11O)3 and palm- -25 1.42715 128.7
nut oils
Caprylin C3H5(O.C8H15O)3 Do. do. -8.3 1.43316 156.7
Caprin C3H5(O.C10H19O)3 Do. do. 31.1 1.43697 184.7
Laurin C3H5(O.C12H23O)3 Do. do. 45 1.44039 212.7
Nutmeg
Myristin C3H5(O.C14H27O)3 56.5 1.44285 240.7
butter
Palm oil,
Palmitin C3H5(O.C16H31O)3 63-64 ... 268.7
lard
Tallow,
Stearin C3H5(O.C18H35O)3 lard, cacao 71.6 ... 296.7
butter
Olein C3H5(O.C18H33O)3 Olive and Solidifies ... 294.7
almond oils at -6
Ricinolein C3H5(O.C18H33O2)3 Castor oil ... ... 310.7

Of the above the most important from a soap-maker's point of view are stearin,
palmitin, olein and laurin, as these predominate in the fats and oils generally
used in that industry. The presence of stearin and palmitin, which are solid at
the ordinary temperature, gives firmness to a fat; the greater the percentage
present, the harder the fat and the higher will be the melting point, hence
tallows and palm oils are solid, firm fats. Where olein, which is liquid, is the
chief constituent, we have softer fats, such as lard, and liquid oils, as almond,
olive and cotton-seed.
Stearin (Tristearin) can be prepared from tallow by crystallisation from a
solution in ether, forming small crystals which have a bright pearly lustre. The
melting point of stearin appears to undergo changes and suggests the existence
of distinct modifications. When heated to 55° C. stearin liquefies; with
increase of temperature it becomes solid, and again becomes liquid at 71.6° C.
If this liquid be further heated to 76° C., and allowed to cool, it will not
solidify until 55° C. is reached, but if the liquid at 71.6° C. be allowed to cool,
solidification will occur at 70° C.
Palmitin (Tripalmitin) may be obtained by heating together palmitic acid and
glycerol, repeatedly boiling the resulting product with strong alcohol, and
allowing it to crystallise. Palmitin exists in scales, which have a peculiar pearly

appearance, and are greasy to the touch. After melting and solidifying, palmitin
shows no crystalline fracture; when heated to 46° C. it melts to a liquid which
becomes solid on further heating, again liquefying when 61.7° C. is reached,
and becoming cloudy, with separation of crystalline particles. At 63° C. it is
quite clear, and this temperature is taken as the true melting point. It has been
suggested that the different changes at the temperatures mentioned are due to
varying manipulation, such as rate at which the temperature is raised, and the
initial temperature of the mass when previously cool.
Olein (Triolein) is an odourless, colourless, tasteless oil, which rapidly absorbs
oxygen and becomes rancid. It has been prepared synthetically by heating
glycerol and oleic acid together, and may be obtained by submitting olive oil to
a low temperature for several days, when the liquid portion may be further
deprived of any traces of stearin and palmitin by dissolving in alcohol. Olein
may be distilled in vacuo without decomposition taking place.
Laurin (Trilaurin) may be prepared synthetically from glycerol and lauric acid.
It crystallises in needles, melting at 45°-46° C., which are readily soluble in
ether, but only slightly so in cold absolute alcohol. Scheij gives its specific
gravity, d60°/4° = 0.8944. Laurin is the chief constituent of palm-kernel oil,
and also one of the principal components of cocoa-nut oil.
Fatty Acids.—When a fat or oil is saponified with soda or potash, the resulting
soap dissolved in hot water, and sufficient dilute sulphuric acid added to
decompose the soap, an oily layer gradually rises to the surface of the liquid,
which, after clarifying by warming and washing free from mineral acid, is
soluble in alcohol and reddens blue litmus paper. This oily layer consists of the
"fatty acids" or rather those insoluble in water, acids like acetic, propionic,
butyric, caproic, caprylic and capric, which are all more or less readily soluble
in water, remaining for the most part dissolved in the aqueous portion. All the
acids naturally present in oils and fats, whether free or combined, are
monobasic in character, that is to say, contain only one carboxyl—CO.OH
group. The more important fatty acids may be classified according to their
chemical constitution into five homologous series, having the general formulæ:
—
I. Stearic series CnH2n+1COOH
II. Oleic series CnH2n-1COOH
III. Linolic series CnH2n-3COOH

IV. Linolenic series CnH2n-5COOH
V. Ricinoleic series CnH2n-7COOH

I. Stearic Series.—The principal acids of this series, together with their
melting points and chief sources, are given in the following table:—

Melting
Acid. Formula. Found in
Point, °C.
Acetic CH3COOH 17 Macassar oil.
Butyric C3H7COOH ... Butter, Macassar oil.
Isovaleric C4H9COOH ... Porpoise and dolphin oils.
Caproic C5H11COOH ... Butter, cocoa-nut oil.
C7H15COOH 15 Butter, cocoa-nut oil, Limburg
Caprylic
cheese.
Capric C9H19COOH 30 Butter, cocoa-nut oil.
Lauric C11H23COOH 44 Cocoa-nut oil, palm-kernel oil.
Ficocerylic C12H25COOH ... Pisang wax.
C13H27COOH 54 Nutmeg butter, liver fat, cocoa-
Myristic
nut oil, dika fat, croton oil.
Palmitic C15H31COOH 62.5 Palm oil, most animal fats.
Daturic C16H33COOH ... Oil of Datura Stramonium.
C17H35COOH 69 Tallow, lard, most solid animal
Stearic
fats.
Arachis or earth-nut oil, rape and
Arachidic C19H39COOH 75
mustard-seed oils.
C21H43COOH ... Ben oil, black mustard-seed oil,
Behenic
rape oil.
Lignoceric C23H47COOH 80.5 Arachis oil.
Carnaubic C23H47COOH ... Carnauba wax.
Pisangcerylic C23H47COOH ... Pisang wax.
Hyænic C24H49COOH ... Hyæna fat.
Cerotic C25H51COOH 78 Beeswax, China wax, spermaceti.
Melissic C29H59COOH 89 Beeswax.
Psyllostearylic C32H65COOH ... Psylla wax.

Theobromic C63H127COOH ... Cacao butter

Medullic and margaric acids, which were formerly included in this series, have
now been shown to consist of mixtures of stearic and palmitic, and stearic
palmitic and oleic acids respectively.
The acids of this group are saturated compounds, and will not combine directly
with iodine or bromine. The two first are liquid at ordinary temperatures, distil
without decomposition, and are miscible with water in all proportions; the next
four are more or less soluble in water and distil unchanged in the presence of
water, as does also lauric acid, which is almost insoluble in cold water, and
only slightly dissolved by boiling water. The higher acids of the series are
solid, and are completely insoluble in water. All these acids are soluble in
warm alcohol, and on being heated with solid caustic alkali undergo no
change.
II. Oleic Series:—

Melting Point,
Acid. Formula. Found in
°C.
Tiglic C4H7COOH 64.5 Croton oil.
Moringic C14H27COOH 0 Ben oil.
Physetoleic C15H29COOH 30 Sperm oil.
Hypogæic C15H29COOH 33 Arachis and maize oils.
Oleic C17H33COOH 14 Most oils and fats.
Rapic C17H33COOH ... Rape oil.
Doeglic C18H35COOH ... Bottle-nose oil.
Mustard oils, marine animal oils,
Erucic C21H41COOH 34
rape oil.

The unsaturated nature of these acids renders their behaviour with various
reagents entirely different from that of the preceding series. Thus, they readily
combine with bromine or iodine to form addition compounds, and the lower
members of the series are at once reduced, on treatment with sodium amalgam
in alkaline solution, to the corresponding saturated acids of Series I.
Unfortunately, this reaction does not apply to the higher acids such as oleic
acid, but as the conversion of the latter into solid acids is a matter of some

technical importance from the point of view of the candle-maker, a number of
attempts have been made to effect this by other methods.
De Wilde and Reychler have shown that by heating oleic acid with 1 per cent.
of iodine in autoclaves up to 270°-280° C., about 70 per cent. is converted into
stearic acid, and Zürer has devised (German Patent 62,407) a process whereby
the oleic acid is first converted by the action of chlorine into the dichloride,
which is then reduced with nascent hydrogen. More recently Norman has
secured a patent (English Patent 1,515, 1903) for the conversion of unsaturated
fatty acids of Series II. into the saturated compounds of Series I., by reduction
with hydrogen or water-gas in the presence of finely divided nickel, cobalt or
iron. It is claimed that by this method oleic acid is completely transformed into
stearic acid, and that the melting point of tallow fatty acids is raised thereby
about 12° C.
Another method which has been proposed is to run the liquid olein over a
series of electrically charged plates, which effects its reduction to stearin.
Stearic acid is also formed by treating oleic acid with fuming hydriodic acid in
the presence of phosphorus, while other solid acids are obtained by the action
of sulphuric acid or zinc chloride on oleic acid.
Acids of Series II. may also be converted into saturated acids by heating to
300°C. with solid caustic potash, which decomposes them into acids of the
stearic series with liberation of hydrogen. This reaction, with oleic acid, for
example, is generally represented by the equation—
C18H34O2 + 2KOH = KC2H3O2 + KC16H31O2 + H2,

though it must be really more complex than this indicates, for, as Edmed has
pointed out, oxalic acid is also formed in considerable quantity. The process on
a commercial scale has now been abandoned.
One of the most important properties of this group of acids is the formation of
isomeric acids of higher melting point on treatment with nitrous acid, generally
termed the elaidin reaction. Oleic acid, for example, acted upon by nitrous
acid, yields elaidic acid, melting at 45°, and erucic acid gives brassic acid,
melting at 60°C. This reaction also occurs with the neutral glycerides of these
acids, olein being converted into elaidin, which melts at 32°C.

The lead salts of the acids of this series are much more soluble in ether, and the
lithium salts more soluble in alcohol than those of the stearic series, upon both
of which properties processes have been based for the separation of the solid
from the liquid fatty acids.
III. Linolic Series:—

Melting Point,
Acid. Formula. Found in
°C.
Elæomargaric C16H29COOH ... Chinese-wood oil.
Elæostearic C16H29COOH 71 Chinese-wood oil.
C17H31COOH Fluid Linseed, cotton-seed and maize
Linolic
oils.
Tariric C17H31COOH 50.5 Tariri-seed oil.
Telfairic C17H31COOH Fluid Telfairia oil.

These acids readily combine with bromine, iodine, or oxygen. They are
unaffected by nitrous acid, and their lead salts are soluble in ether.
IV. Linolenic Series:—

Acid. Formula. Found in
Linolenic C17H29COOH Linseed oil.
Isolinolenic C17H29COOH Linseed oil.
Jecoric C17H29COOH Cod-liver and marine animal oils.

These acids are similar in properties to those of Class III., but combine with
six atoms of bromine or iodine, whereas the latter combine with only four
atoms.
V. Ricinoleic Series:—

Acid. Formula. Melting Point, °C. Found in
Ricinoleic C17H22(OH)COOH 4-5 Castor oil.

This acid combines with two atoms of bromine or iodine, and is converted by
nitrous acid into the isomeric ricinelaidic acid, which melts at 52°-53° C. Pure

ricinoleic acid, obtained from castor oil, is optically active, its rotation being
αd +6° 25'.

Hydrolysis or Saponification of Oils and Fats.—The decomposition of a
triglyceride, brought about by caustic alkalies in the formation of soap, though
generally represented by the equation already given (pp. 6 and 7)—
C3H5(OR) + 3NaOH = C3H5(OH)3 + 3RONa,

is not by any means such a simple reaction.
In the first place, though in this equation no water appears, the presence of the
latter is found to be indispensable for saponification to take place; in fact, the
water must be regarded as actually decomposing the oil or fat, caustic soda or
potash merely acting as a catalytic agent. Further, since in the glycerides there
are three acid radicles to be separated from glycerol, their saponification can
be supposed to take place in three successive stages, which are the converse of
the formation of mono- and diglycerides in the synthesis of triglycerides from
fatty acids and glycerine. Thus, the above equation may be regarded as a
summary of the following three:—

{ OR { OH
(i.) C3H5 { OR + NaOH = C3H5 { OR + RONa
{ OR { OR

{ OH { OH
(ii.) C3H5 { OR + NaOH = C3H5 { OR + RONa
{ OR { OH

{ OH { OH
(iii.) C3H5 { OR + NaOH = C3H5 { OH + RONa
{ OH { OH

Geitel and Lewkowitsch, who have studied this question from the physical and
chemical point of view respectively, are of opinion that when an oil or fat is
saponified, these three reactions do actually occur side by side, the soap-pan
containing at the same time unsaponified triglyceride, diglyceride,
monoglyceride, glycerol and soap.
This theory is not accepted, however, by all investigators. Balbiano and
Marcusson doubt the validity of Lewkowitsch's conclusions, and Fanto,
experimenting on the saponification of olive oil with caustic potash, is unable
to detect the intermediate formation of any mono- or diglyceride, and
concludes that in homogeneous solution the saponification is practically
quadrimolecular. Kreeman, on the other hand, from physico-chemical data,
supports the view of Geitel and Lewkowitsch that saponification is
bimolecular, and though the evidence seems to favour this theory, the matter
cannot be regarded as yet definitely settled.
Hydrolysis can be brought about by water alone, if sufficient time is allowed,
but as the process is extremely slow, it is customary in practice to accelerate
the reaction by the use of various methods, which include (i.) the application
of heat or electricity, (ii.) action of enzymes, and (iii.) treatment with
chemicals; the accelerating effect of the two latter methods is due to their
emulsifying power.
The most usual method adopted in the manufacture of soap is to hydrolyse the
fat or oil by caustic soda or potash, the fatty acids liberated at the same time
combining with the catalyst, i.e., soda or potash, to form soap. Hitherto the
other processes of hydrolysis have been employed chiefly for the preparation
of material for candles, for which purpose complete separation of the glycerol
in the first hydrolysis is not essential, since the fatty matter is usually subjected
to a second treatment with sulphuric acid to increase the proportion of solid
fatty acids. The colour of the resulting fatty acids is also of no importance, as
they are always subjected to distillation.
During the last few years, however, there has been a growing attempt to first
separate the glycerol from the fatty acids, and then convert the latter into soap
by treatment with the carbonates of soda or potash, which are of course
considerably cheaper than the caustic alkalies, but cannot be used in the actual
saponification of a neutral fat. The two processes chiefly used for this purpose
are those in which the reaction is brought about by enzymes or by Twitchell's
reagent.

I. Application of Heat or Electricity.—Up to temperatures of 150° C. the effect
of water on oils and fats is very slight, but by passing superheated steam
through fatty matter heated to 200°-300° C. the neutral glycerides are
completely decomposed into glycerol and fatty acids according to the equation
—
C3H5(OR)3 + 3H.OH = C3H5(OH)3 + 3ROH.

The fatty acids and glycerol formed distil over with the excess of steam, and
by arranging a series of condensers, the former, which condense first, are
obtained almost alone in the earlier ones, and an aqueous solution of glycerine
in the later ones. This method of preparation of fatty acids is extensively used
in France for the production of stearine for candle-manufacture, but the
resulting product is liable to be dark coloured, and to yield a dark soap. To
expose the acids to heat for a minimum of time, and so prevent discoloration,
Mannig has patented (Germ. Pat. 160,111) a process whereby steam under a
pressure of 8 to 10 atmospheres is projected against a baffle plate mounted in a
closed vessel, where it mixes with the fat or oil in the form of a spray, the rate
of hydrolysis being thereby, it is claimed, much increased.
Simpson (Fr. Pat. 364,587) has attempted to accelerate further the
decomposition by subjecting oils or fats to the simultaneous action of heat and
electricity. Superheated steam is passed into the oil, in which are immersed the
two electrodes connected with a dynamo or battery, the temperature not being
allowed to exceed 270° C.
II. Action of Enzymes.—It was discovered by Muntz in 1871 (Annales de
Chemie, xxii.) that during germination of castor seeds a quantity of fatty acid
was developed in the seeds, which he suggested might be due to the
decomposition of the oil by the embryo acting as a ferment. Schutzenberger in
1876 showed that when castor seeds are steeped in water, fatty acids and
glycerol are liberated, and attributed this to the hydrolytic action of an enzyme
present in the seeds. No evidence of the existence of such a ferment was
adduced, however, till 1890, when Green (Roy. Soc. Proc., 48, 370) definitely
proved the presence in the seeds of a ferment capable of splitting up the oil
into fatty acid and glycerol.
The first experimenters to suggest any industrial application of this enzymic
hydrolysis were Connstein, Hoyer and Wartenburg, who (Berichte, 1902, 35,
pp. 3988-4006) published the results of a lengthy investigation of the whole

subject. They found that tallow, cotton-seed, palm, olive, almond, and many
other oils, were readily hydrolysed by the castor-seed ferment in the presence
of dilute acid, but that cocoa-nut and palm-kernel oils only decomposed with
difficulty. The presence of acidity is essential for the hydrolysis to take place,
the most suitable strength being one-tenth normal, and the degree of hydrolysis
is proportional to the quantity of ferment present. Sulphuric, phosphoric, acetic
or butyric acids, or sodium bisulphate, may be used without much influence on
the result. Butyric acid is stated to be the best, but in practice is too expensive,
and acetic acid is usually adopted. The emulsified mixture should be allowed
to stand for twenty-four hours, and the temperature should not exceed 40° C.;
at 50° C. the action is weakened, and at 100° C. ceases altogether.
Several investigators have since examined the hydrolysing power of various
other seeds, notably Braun and Behrendt (Berichte, 1903, 36, 1142-1145,
1900-1901, and 3003-3005), who, in addition to confirming Connstein, Hoyer
and Wartenburg's work with castor seeds, have made similar experiments with
jequirity seeds (Abrus peccatorius) containing the enzyme abrin, emulsin from
crushed almonds, the leaves of Arctostaphylos Uva Ursi, containing the
glucoside arbutin, myrosin from black mustard-seed, gold lac (Cheirantus
cheiri) and crotin from croton seeds. Jequirity seeds were found to have a
stronger decomposing action on lanoline and carnauba wax than the castor
seed, but only caused decomposition of castor oil after the initial acidity was
first neutralised with alkali. Neither emulsin, arbutin nor crotin have any
marked hydrolytic action on castor oil, but myrosin is about half as active as
castor seeds, except in the presence of potassium myronate, when no
decomposition occurs.
S. Fokin (J. russ. phys. chem. Ges., 35, 831-835, and Chem. Rev. Fett. u. Harz.
Ind., 1904, 30 et seq.) has examined the hydrolytic action of a large number of
Russian seeds, belonging to some thirty different families, but although more
than half of these brought about the hydrolysis of over 10 per cent. of fat, he
considers that in only two cases, viz., the seeds of Chelidonium majus and
Linaria vulgaris, is the action due to enzymes, these being the only two seeds
for which the yield of fatty acids is proportional to the amount of seed
employed, while in many instances hydrolysis was not produced when the
seeds were old. The seeds of Chelidonium majus were found to have as great,
and possibly greater, enzymic activity than castor seeds, but those of Linaria
are much weaker, twenty to thirty parts having only the same lipolytic activity
as four to five parts of castor seeds.

The high percentage of free acids found in rice oil has led C. A. Brown, jun.
(Journ. Amer. Chem. Soc., 1903, 25, 948-954), to examine the rice bran, which
proves to have considerable enzymic activity, and rapidly effects the
hydrolysis of glycerides.
The process for the utilisation of enzymic hydrolysis in the separation of fatty
acids from glycerine on the industrial scale, as originally devised by Connstein
and his collaborators, consisted in rubbing a quantity of the coarsely crushed
castor seeds with part of the oil or fat, then adding the rest of the oil, together
with acidified water (N/10 acetic acid). The quantities employed were 6-1/2
parts of decorticated castor beans for every 100 parts of oil or fat, and 50 to 60
parts of acetic acid. After stirring until an emulsion is formed, the mixture is
allowed to stand for twenty-four hours, during which hydrolysis takes place.
The temperature is then raised to 70°-80° C., which destroys the enzyme, and a
25 per cent. solution of sulphuric acid, equal in amount to one-fiftieth of the
total quantity of fat originally taken, added to promote separation of the fatty
acids. In this way three layers are formed, the one at the top consisting of the
clear fatty acids, the middle one an emulsion containing portions of the seeds,
fatty acids and glycerine, and the bottom one consisting of the aqueous
glycerine. The intermediate layer is difficult to treat satisfactorily; it is
generally washed twice with water, the washings being added to glycerine
water, and the fatty mixture saponified and the resultant soap utilised.
The process has been the subject of a considerable amount of investigation,
numerous attempts having been made to actually separate the active fat-
splitting constituent of the seeds, or to obtain it in a purer and more
concentrated form than is furnished by the seeds themselves. Nicloux
(Comptes Rendus, 1904, 1112, and Roy. Soc. Proc., 1906, 77 B, 454) has
shown that the hydrolytic activity of castor seeds is due entirely to the
cytoplasm, which it is possible to separate by mechanical means from the
aleurone grains and all other cellular matter. This active substance, which he
terms "lipaseidine," is considered to be not an enzyme, though it acts as such,
following the ordinary laws of enzyme action; its activity is destroyed by
contact with water in the absence of oil. This observer has patented (Eng. Pat.
8,304, 1904) the preparation of an "extract" by triturating crushed castor or
other seeds with castor oil, filtering the oily extract, and subjecting it to
centrifugal force. The deposit consists of aleurone and the active enzymic
substance, together with about 80 per cent. of oil, and one part of it will effect
nearly complete hydrolysis of 100 parts of oil in twenty-four hours. In a

subsequent addition to this patent, the active agent is separated from the
aleurone by extraction with benzene and centrifugal force. By the use of such
an extract, the quantity of albuminoids brought into contact with the fat is
reduced to about 10 per cent. of that in the original seeds, and the middle layer
between the glycerine solution and fatty acids is smaller and can be saponified
directly for the production of curd soap, while the glycerine solution also is
purer.
In a further patent Nicloux (Fr. Pat. 349,213, 1904) states that the use of an
acid medium is unnecessary, and claims that even better results are obtained by
employing a neutral solution of calcium sulphate containing a small amount of
magnesium sulphate, the proportion of salts not exceeding 0.5 per cent. of the
fat, while in yet another patent, jointly with Urbain (Fr. Pat. 349,942, 1904), it
is claimed that the process is accelerated by the removal of acids from the oil
or fat to be treated, which may be accomplished by either washing first with
acidulated water, then with pure water, or preferably by neutralising with
carbonate of soda and removing the resulting soap.
Lombard (Fr. Pat. 350,179, 1904) claims that acids act as stimulating agents in
the enzymic hydrolysis of oils, and further that a simple method of obtaining
the active product is to triturate oil cake with its own weight of water, allow
the mixture to undergo spontaneous proteolytic hydrolysis at 40° C. for eight
days, and then filter, the filtrate obtained being used in place of water in the
enzymic process.
Hoyer, who has made a large number of experiments in the attempt to isolate
the lipolytic substance from castor seeds, has obtained a product of great
activity, which he terms "ferment-oil," by extracting the crushed seeds with a
solvent for oils.
The Verein Chem. Werke have extended their original patent (addition dated
11th December, 1905, to Fr. Pat. 328,101, Oct., 1902), which now covers the
use of vegetable ferments in the presence of water and manganese sulphate or
other metallic salt. It is further stated that acetic acid may be added at the
beginning of the operation, or use may be made of that formed during the
process, though in the latter case hydrolysis is somewhat slower.
Experiments have been carried out by Lewkowitsch and Macleod (Journ. Soc.
Chem. Ind., 1903, 68, and Proc. Roy. Soc., 1903, 31) with ferments derived
from animal sources, viz., lipase from pig's liver, and steapsin from the pig or

ox pancreas. The former, although it has been shown by Kastle and Loevenhart
(Amer. Chem. Journ., 1900, 49) to readily hydrolyse ethyl butyrate, is found to
have very little fat-splitting power, but with steapsin more favourable results
have been obtained, though the yield of fatty acids in this case is considerably
inferior to that given by castor seeds. With cotton-seed oil, 83-86 per cent. of
fatty acids were liberated as a maximum after fifty-six days, but with lard only
46 per cent. were produced in the same time. Addition of dilute acid or alkali
appeared to exert no influence on the decomposition of the cotton-seed oil, but
in the case of the lard, dilute alkali seemed at first to promote hydrolysis,
though afterwards to retard it.
Fokin (Chem. Rev. Fett. u. Harz. Ind., 1904, 118-120 et seq.) has attempted to
utilise the pancreatic juice on a technical scale, but the process proved too slow
and too costly to have any practical use.
Rancidity.—The hydrolysing power of enzymes throws a good deal of light on
the development of rancidity in oils and fats, which is now generally regarded
as due to the oxidation by air in the presence of light and moisture of the free
fatty acids contained by the oil or fat. It has long been known that whilst
recently rendered animal fats are comparatively free from acidity, freshly
prepared vegetable oils invariably contain small quantities of free fatty acid,
and there can be no doubt that this must be attributed to the action of enzymes
contained in the seeds or fruit from which the oils are expressed, hence the
necessity for separating oils and fats from adhering albuminous matters as
quickly as possible.
Decomposition of Fats by Bacteria.—Though this subject is not of any
practical interest in the preparation of fatty acids for soap-making, it may be
mentioned, in passing, that some bacteria readily hydrolyse fats. Schriber
(Arch. f. Hyg., 41, 328-347) has shown that in the presence of air many
bacteria promote hydrolysis, under favourable conditions as to temperature and
access of oxygen, the process going beyond the simple splitting up into fatty
acid and glycerol, carbon dioxide and water being formed. Under anærobic
conditions, however, only a slight primary hydrolysis was found to take place,
though according to Rideal (Journ. Soc. Chem. Ind., 1903, 69) there is a
distinct increase in the amount of free fatty acids in a sewage after passage
through a septic tank.
Experiments have also been made on this subject by Rahn (Centralb.
Bakteriol, 1905, 422), who finds that Penicillium glaucum and other penicillia

have considerable action on fats, attacking the glycerol and lower fatty acids,
though not oleic acid. A motile bacillus, producing a green fluorescent
colouring matter, but not identified, had a marked hydrolytic action and
decomposed oleic acid. The name "lipobacter" has been proposed by De
Kruyff for bacteria which hydrolyse fats.
III. Use of Chemical Reagents.—Among the chief accelerators employed in
the hydrolysis of oils are sulphuric acid and Twitchell's reagent (benzene- or
naphthalene-stearosulphonic acid), while experiments have also been made
with hydrochloric acid (Journ. Soc. Chem. Ind., 1903, 67) with fairly
satisfactory results, and the use of sulphurous acid, or an alkaline bisulphite as
catalyst, has been patented in Germany. To this class belong also the bases,
lime, magnesia, zinc oxide, ammonia, soda and potash, though these latter
substances differ from the former in that they subsequently combine with the
fatty acids liberated to form soaps.
Sulphuric Acid.—The hydrolysing action of concentrated sulphuric acid upon
oils and fats has been known since the latter part of the eighteenth century, but
was not applied on a practical scale till 1840 when Gwynne patented a process
in which sulphuric acid was used to liberate the fatty acids, the latter being
subsequently purified by steam distillation. By this method, sulpho-compounds
of the glyceride are first formed, which readily emulsify with water, and, on
treatment with steam, liberate fatty acids, the glycerol remaining partly in the
form of glycero-sulphuric acid. The process has been investigated by Fremy,
Geitel, and more recently by Lewkowitsch (J. Soc. of Arts, "Cantor Lectures,"
1904, 795 et seq.), who has conducted a series of experiments on the
hydrolysis of tallow with 4 per cent. of sulphuric acid of varying strengths,
containing from 58 to 90 per cent. sulphuric acid, H2SO4. Acid of 60 per cent.
or less appears to be practically useless as a hydrolysing agent, while with 70
per cent. acid only 47.7 per cent. fatty acids were developed after twenty-two
hours' steaming, and with 80 and 85 per cent. acid, the maximum of 89.9 per
cent. of fatty acids was only reached after fourteen and fifteen hours' steaming
respectively. Using 98 per cent. acid, 93 per cent. of fatty acids were obtained
after nine hours' steaming, and after another seven hours, only 0.6 per cent.
more fatty acids were produced. Further experiments have shown that dilute
sulphuric acid has also scarcely any action on cotton-seed, whale, and rape
oils.

According to Lant Carpenter, some 75 per cent. of solid fatty acids may be
obtained from tallow by the sulphuric acid process, owing to the conversion of
a considerable quantity of oleic acid into isoleic acid (vide p. 12), but in the
process a considerable proportion of black pitch is obtained. C. Dreymann has
recently patented (Eng. Pat. 10,466, 1904) two processes whereby the
production of any large amount of hydrocarbons is obviated. In the one case,
after saponification with sulphuric acid, the liberated fatty acids are washed
with water and treated with an oxide, carbonate, or other acid-fixing body, e.g.,
sodium carbonate, prior to distillation. In this way the distillate is much clearer
than by the ordinary process, and is almost odourless, while the amount of
unsaponifiable matter is only about 1.2 per cent. The second method claimed
consists in the conversion of the fatty acids into their methyl esters by
treatment with methyl alcohol and hydrochloric acid gas, and purification of
the esters by steam distillation, the pure esters being subsequently decomposed
with superheated steam, in an autoclave, with or without the addition of an
oxide, e.g., 0.1 per cent. zinc oxide, to facilitate their decomposition.
Twitchell's Reagent.—In Twitchell's process use is made of the important
discovery that aqueous solutions of fatty aromatic sulphuric acids, such as
benzene- or naphthalene-stearosulphonic acid, readily dissolve fatty bodies,
thereby facilitating their dissociation into fatty acids and glycerol. These
compounds are stable at 100° C., and are prepared by treating a mixture of
benzene or naphthalene and oleic acid with an excess of sulphuric acid, the
following reaction taking place:—
C6H6 + C18H34O2 + H2SO4 = C6H4(SO3H)C18H35O + H2O.

On boiling the resultant product with water two layers separate, the lower one
consisting of a clear aqueous solution of sulphuric acid and whatever benzene-
sulphonic acid has been formed, while the upper layer, which is a viscous oil,
contains the benzene-stearosulphonic acid. This, after washing first with
hydrochloric acid and then rapidly with petroleum ether, and drying at 100° C.
is then ready for use; the addition of a small quantity of this reagent to a
mixture of fat (previously purified) and water, agitated by boiling with open
steam, effects almost complete separation of the fatty acid from glycerol.
The process is generally carried out in two wooden vats, covered with closely
fitting lids, furnished with the necessary draw-off cocks, the first vat
containing a lead coil and the other a brass steam coil.

In the first vat, the fat or oil is prepared by boiling with 1 or 2 per cent. of
sulphuric acid (141° Tw. or 60° B.) for one or two hours and allowed to rest,
preferably overnight; by this treatment the fat is deprived of any dirt, lime or
other impurity present. After withdrawing the acid liquor, the fat or oil is
transferred to the other vat, where it is mixed with one-fifth of its bulk of water
(condensed or distilled), and open steam applied. As soon as boiling takes
place, the requisite amount of reagent is washed into the vat by the aid of a
little hot water through a glass funnel, and the whole is boiled continuously for
twelve or even twenty-four hours, until the free fatty acids amount to 85-90 per
cent. The amount of reagent used varies with the grade of material, the smaller
the amount consistent with efficient results, the better the colour of the finished
product; with good material, from 1/2 to 3/4 per cent. is sufficient, but for
materials of lower grade proportionately more up to 2 per cent. is required. The
reaction appears to proceed better with materials containing a fair quantity of
free acidity.
When the process has proceeded sufficiently far, the boiling is stopped and
free steam allowed to fill the vat to obviate any discoloration of the fatty acids
by contact with the air, whilst the contents of the vat settle.
The settled glycerine water, which should amount in bulk to 50 or 60 per cent.
of the fatty matter taken, and have a density of 7-1/2° Tw. (5° B.), is removed
to a receptacle for subsequent neutralisation with milk of lime, and, after the
separation of sludge, is ready for concentration.
The fatty acids remaining in the vat are boiled with a small quantity (0.05 per
cent., or 1/10 of the Twitchell reagent requisite) of commercial barium
carbonate, previously mixed with a little water; the boiling may be prolonged
twenty or thirty minutes, and at the end of that period the contents of the vat
are allowed to rest; the water separated should be neutral to methyl-orange
indicator.
It is claimed that fatty acids so treated are not affected by the air, and may be
stored in wooden packages.
Hydrochloric Acid.—Lewkowitsch (Journ. Soc. Chem. Ind., 1903, 67) has
carried out a number of experiments on the accelerating influence of
hydrochloric acid upon the hydrolysis of oils and fats, which show that acid of
a specific gravity of 1.16 has a very marked effect on most oils, cocoa-nut,
cotton-seed, whale and rape oils, tallow and lard being broken up into fatty

acid and glycerol to the extent of some 82-96 per cent. after boiling 100 grams
of the oil or fat with 100 c.c. of acid for twenty-four hours. The maximum
amount of hydrolysis was attained with cocoa-nut oil, probably owing to its
large proportion of the glycerides of volatile fatty acids. Castor oil is abnormal
in only undergoing about 20 per cent. hydrolysis, but this is attributed to the
different constitution of its fatty acids, and the ready formation of
polymerisation products. Experiments were also made as to whether the
addition of other catalytic agents aided the action of the hydrochloric acid;
mercury, copper sulphate, mercury oxide, zinc, zinc dust, aluminium chloride,
nitrobenzene and aniline being tried, in the proportion of 1 per cent. The
experiments were made on neutral lard and lard containing 5 per cent. of free
fatty acids, but in no case was any appreciable effect produced.
So far this process has not been adopted on the practical scale, its chief
drawback being the length of time required for saponification. Undoubtedly
the hydrolysis would be greatly facilitated if the oil and acid could be made to
form a satisfactory emulsion, but although saponin has been tried for the
purpose, no means of attaining this object has yet been devised.
Sulphurous Acid or Bisulphite.—The use of these substances has been patented
by Stein, Berge and De Roubaix (Germ. Pat. 61,329), the fat being heated in
contact with the reagent for about nine hours at 175°-180° C. under a pressure
of some 18 atmospheres, but the process does not appear to be of any
considerable importance.
Lime.—The use of lime for the saponification of oils and fats was first adopted
on the technical scale for the production of candle-making material, by De
Milly in 1831. The insoluble lime soap formed is decomposed by sulphuric
acid, and the fatty acids steam distilled.
The amount of lime theoretically necessary to hydrolyse a given quantity of a
triglyceride, ignoring for the moment any catalytic influence, can be readily
calculated; thus with stearin the reaction may be represented by the equation:
—

CH2OOC18H35 CH2OH
| |
2CHOOC18H35 + 3Ca(OH)2 = 3Ca(OOC18H35)2 + 2CHOH
| |

CH2OOC18H35 CH2OH
stearin milk of lime calcium stearate glycerol

In this instance, since the molecular weight of stearin is 890 and that of milk of
lime is 74, it is at once apparent that for every 1,780 parts of stearin, 222 parts
of milk of lime or 168 parts of quick-lime, CaO, would be required. It is found
in practice, however, that an excess of 3-5 per cent. above the theoretical
quantity of lime is necessary to complete the hydrolysis of a fat when carried
on in an open vessel at 100°-105° C., but that if the saponification be
conducted under pressure in autoclaves the amount of lime necessary to secure
almost perfect hydrolysis is reduced to 2-3 per cent. on the fat, the treatment of
fats with 3 per cent. of lime under a pressure of 10 atmospheres producing a
yield of 95 per cent. of fatty acids in seven hours. The lower the pressure in the
autoclave, the lighter will be the colour of the resultant fatty acids.
Magnesia.—It has been proposed to substitute magnesia for lime in the
process of saponification under pressure, but comparative experiments with
lime and magnesia, using 3 per cent. of lime and 2.7 per cent. of magnesia
(Journ. Soc. Chem. Ind., xii., 163), show that saponification by means of
magnesia is less complete than with lime, and, moreover, the reaction requires
a higher temperature and therefore tends to darken the product.
Zinc Oxide.—The use of zinc oxide as accelerating agent has been suggested
by two or three observers. Poullain and Michaud, in 1882, were granted a
patent for this process, the quantity of zinc oxide recommended to be added to
the oil or fat being 0.2 to 0.5 per cent. Rost, in 1903, obtained a French patent
for the saponification of oils and fats by steam under pressure in the presence
of finely divided metals or metallic oxides, and specially mentions zinc oxide
for the purpose.
It has also been proposed to use zinc oxide in conjunction with lime in the
autoclave to obviate to some extent the discoloration of the fatty acids.
Other catalytic agents have been recommended from time to time, including
strontianite, lead oxide, caustic baryta, aluminium hydrate, but none of these is
of any practical importance.
Soda and Potash.—Unlike the preceding bases, the soaps formed by soda and
potash are soluble in water, and constitute the soap of commerce. These
reagents are always used in sufficient quantity to combine with the whole of

the fatty acids contained in an oil or fat, though doubtless, by the use of
considerably smaller quantities, under pressure, complete resolution of the
fatty matter into fatty acids and glycerol could be accomplished. They are, by
far, the most important saponifying agents from the point of view of the
present work, and their practical use is fully described in Chapter V.

CHAPTER III.
RAW MATERIALS USED IN SOAP-MAKING.

Fats and Oils—Waste Fats—Fatty Acids—Less-known Oils and
Fats of Limited Use—Various New Fats and Oils Suggested for
Soap-making—Rosin—Alkali (Caustic and Carbonated)—Water—
Salt—Soap-stock.
Fats and Oils.—All animal and vegetable oils and fats intended for soap-
making should be as free as possible from unsaponifiable matter, of a good
colour and appearance, and in a sweet, fresh condition. The unsaponifiable
matter naturally present as cholesterol, or phytosterol, ranges in the various
oils and fats from 0.2 to 2.0 per cent. All oils and fats contain more or less free
acidity; but excess of acidity, though it may be due to the decomposition of the
glyceride, and does not always denote rancidity, is undesirable in soap-making
material. Rancidity of fats and oils is entirely due to oxidation, in addition to
free acid, aldehydes and ketones being formed, and it has been proposed to
estimate rancidity by determining the amount of these latter produced. It is
scarcely necessary to observe how very important it is that the sampling of fats
and oils should be efficiently performed, so that the sample submitted to the
chemist may be a fairly representative average of the parcel.
In the following short description of the materials used, we give, under each
heading, figures for typical samples of the qualities most suitable for soap-
making.
Tallows.—Most of the imported tallow comes from America, Australia and
New Zealand. South American mutton tallow is usually of good quality; South
American beef tallow is possessed of a deep yellow colour and rather strong
odour, but makes a bright soap of a good body and texture. North American
tallows are, as a general rule, much paler in colour than those of South
America, but do not compare with them in consistence. Most of the
Australasian tallows are of very uniform quality and much in demand.
Great Britain produces large quantities of tallow which comes into the market
as town and country tallow, or home melt. Owing to the increasing demand for

edible fat, much of the rough fat is carefully selected, rendered separately, and
the product sold for margarine-making. Consequently the melted tallow for
soap-making is of secondary importance to the tallow melter.
The following are typical samples of tallow:—

Saponification Acidity (as Oleic Titre,
Equivalent. Acid) Per Cent. °C.
Australian mutton 285 0.85 45
Australian mutton 284.4 0.48 48.3
Australian beef 284.2 1.68 43.9
Australian beef 283.6 0.85 42.6
Australian mixed 285.1 3.52 44
Australian mixed 284.6 1.89 43.5
South American mutton 284.5 1.11 47
South American mutton 285 0.90 47.4
South American beef 284.7 0.81 45
South American beef 284 0.94 44
North American mutton 284.3 1.32 44
North American mutton 85 2.18 43.2
North American beef,
284.5 1.97 41.5
fine
North American beef,
283.8 4.30 42
good
North American
285.2 5.07 41.75
ordinary
North American prime
286 1.01 41.2
city
Selected English mutton 283.9 1.45 47
Selected English beef 284.2 2.40 44
Home-rendered or
284.6 5.1 43
country tallow
Town tallow 285.3 7.4 42.5

Tallow should absorb from 39 to 44 per cent. iodine.
Lard.—Lard is largely imported into this country from the United States of
America. The following is a typical sample of American hog's fat offered for

soap-making:—

Saponification Acidity (as Oleic Acid) Titre, Refractive Index at
Equivalent. Per Cent. °C. 60° C.
286 0.5 37.5 1.4542

Lard should absorb 59 to 63 per cent. iodine.
Cocoa-nut Oil.—The best known qualities are Cochin and Ceylon oils, which
are prepared in Cochin (Malabar) or the Philippine Islands and Ceylon
respectively.
The dried kernels of the cocoa-nut are exported to various ports in Europe, and
the oil obtained comes on the market as Continental Coprah Oil, with the
prefix of the particular country or port where it has been crushed, e.g., Belgian,
French and Marseilles Coprah Oil. Coprah is also imported into England, and
the oil expressed from it is termed English Pressed Coprah.
The following are typical examples from bulk:—

Saponification Acidity (as Oleic Titre, Refractive Index
Equivalent. Acid) Per Cent. °C. at 25° C.
Cochin oil 215.5 1.5 23.5 1.4540
Cochin oil 214.3 2.6 22.1 1.4541
Ceylon oil 214.6 5.47 23 1.4535
Ceylon oil 216 3.95 22.75 1.4535
Belgian
214.2 1.65 23 1.4541
coprah
Belgian
215 2.60 22.1 1.4540
coprah
French
214.2 6.55 23 1.4535
coprah
French
214.8 7.42 22 1.4540
coprah
Pressed
215.8 7.45 22.2 1.4542
coprah
Pressed
216 9.41 22 1.4555
coprah

Cocoa-nut oil should absorb 8.9 to 9.3 per cent. iodine.
Palm-nut Oil.—The kernels of the palm-tree fruit are exported from the west
coast of Africa to Europe, and this oil obtained from them. Typical samples of
English and Hamburg oils tested:—

Saponification Acidity (as Oleic Acid) Titre, Refractive Index at
Equivalent. Per Cent. °C. 25° C.
225 4.4 24 1.4553
227 7.7 23.8 1.4553

Palm-nut oil should absorb 10 to 13 per cent. iodine.
Olive Oil.—The olive is extensively grown in Southern Europe and in portions
of Asia and Africa bordering the Mediterranean Sea. The fruit of this tree
yields the oil.
The free fatty acid content of olive oil varies very considerably. Very fine oils
contain less than 1 per cent. acidity; commercial oils may be graded according
to their free acidity, e.g., under 5 per cent., under 10 per cent., etc., and it
entirely depends upon the desired price of the resultant soap as to what grade
would be used. The following is a typical sample for use in the production of
high-class toilet soap:—

Saponification Acidity (as Oleic Acid) Titre, Refractive Index at
Equivalent. Per Cent. °C. 15° C.
288 1.8 21 1.4704

Olive oil should absorb 80 to 83 per cent. iodine.
Olive-kernel oil, more correctly termed Sulphur olive oil.
The amount of free fatty acids is always high and ranges from 40-70 per cent.,
and, of course, its glycerol content is proportionately variable. The free acidity
increases very rapidly, and is, doubtless, due to the decomposition of the
neutral oil by the action of hydrolytic ferment.
A representative sample of a parcel tested:—

Saponification Acidity (as Oleic Acid) Per Refractive Index at 20°
Equivalent. Cent. C.

298 40.96 1.4666

Palm oil is produced from the fruit of palm trees, which abound along the west
coast of Africa. Lagos is the best quality, whilst Camaroons, Bonny, Old
Calabar and New Calabar oils are in good request for bleaching purposes.
Analysis of typical samples of crude palm oil has given:—

Saponification Acidity (as Oleic Acid) Titre, Water and Impurities,
Equivalent. Per Cent. °C. Per Cent.
278 10.7 45 1.6
280 31.2 44.5 2.8

Palm oil should absorb 51 to 56 per cent. iodine.
In the lower qualities we have examples of the result of hydrolytic
decomposition by enzymes, the free acidity often amounting to 70 per cent.
Cotton-seed Oil.—This oil is expressed from the seeds separated from the
"wool" of the various kinds of cotton tree largely cultivated in America and
Egypt.
In its crude state cotton-seed oil is a dark fluid containing mucilaginous and
colouring matter, and is not applicable for soap-making. The following figures
are representative of well-refined cotton-seed oils:—

Specific
Saponification Acidity (as Oleic Titre, Refractive Index
Gravity at 15°
Equivalent. Acid) Per Cent. °C. at 20° C.
C.
0.9229 290 0.24 33.6 1.4721
0.924 299 0.39 35 1.4719

Cotton-seed oil should absorb 104 to 110 per cent. iodine.
Cotton-seed Stearine.—The product obtained by pressing the deposit which
separates on chilling refined cotton-seed oil.
A typical sample tested:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent. Titre, °C.
285.1 0.05 38

Arachis Oil.—The earth-nut or ground-nut, from which arachis oil is obtained,
is extensively cultivated in North America, India and Western Africa. Large
quantities are exported to Marseilles where the oil is expressed. Arachis oil
enters largely into the composition of Marseilles White Soaps.
Representative samples of commercial and refined oils tested:—

Specific Acidity (as Refractive
Saponification Titre,
Gravity at Oleic Acid) Index at 20°
Equivalent °C.
15° C. Per Cent. C.
Commercial 0.9184 298 2.6 28.6 ...
Refined 0.9205 285 0.22 24.0 1.4712

Arachis oil should absorb 90 to 98 per cent. iodine.
Maize Oil.—America (U.S.) produces very large quantities of maize oil.
Typical samples of crude and refined oil gave these figures:—

Specific Acidity (as
Saponification Titre, Refractive
Gravity at Oleic Acid)
Equivalent °C. Index at 20° C.
15° C. Per Cent.
Crude 0.9246 294 1.41 15 ...
Refined 0.9248 294.1 0.40 17.2 1.4766

Maize oil should absorb 120 to 128 per cent. iodine.
Sesame Oil.—Sesame oil is very largely pressed in Southern France from the
seeds of the sesame plant which is cultivated in the Levant, India, Japan and
Western Africa.
A fairly representative sample of French expressed oil tested:—

Specific
Saponification Acidity (as Oleic Titre, Refractive Index
Gravity at 15°
Equivalent Acid) Per Cent. °C. at 20° C.
C.
0.9227 295.2 1.84 22.8 1.4731

Sesame oil should absorb 108 to 110 per cent. iodine.

Linseed Oil.—Russia, India, and Argentine Republic are the principal
countries which extensively grow the flax plant, from the seeds of which
linseed oil is pressed. It is used to a limited extent in soft-soap making.
A good sample gave on analysis:—

Specific
Saponification Acidity (as Oleic Titre, Refractive Index
Gravity at 15°
Equivalent Acid) Per Cent. °C. at 15° C.
C.
0.935 292 1.2 20 1.4840

Linseed oil should absorb 170 to 180 per cent. iodine.
Hemp-seed oil is produced from the seeds of the hemp plant which grows in
Russia. This oil is used in soft soap-making, more particularly on the
Continent.
A typical sample gave the following figures:—

Specific Gravity at 15° C. Saponification Equivalent. Titre, °C. Iodine No.
0.926 292.6 15.8 143

Sunflower oil is produced largely in Russia.
A specimen tested:—

Specific Gravity Saponification Acidity (as Oleic Titre, Iodine
at 15° C. Equivalent. Acid) Per Cent. °C. No.
0.9259 290.7 0.81 17 126.2

Castor Oil.—The castor oil plant is really a native of India, but it is also
cultivated in the United States (Illinois) and Egypt.
A typical commercial sample tested:—

Acidity (as
Saponification Titre, Iodine Optical Refractive
Oleic Acid) Per Rotation α
Equivalent. °C. No. D Index at 25° C.
Cent.
310 1.5 2.8 84.1 + 4° 50' 1.4787

Fish and Marine Animal Oils.—Various oils of this class have, until recently,
entered largely into the composition of soft soaps, but a demand has now
arisen for soft soaps made from vegetable oils.
We quote a few typical analyses of these oils:—

Specific Acidity (as
Saponification Titre, Unsaponifiable
Gravity at Oleic Acid)
Equivalent. °C. Matter Per Cent.
15° C. Per Cent.
Pale seal
0.9252 289 0.947 15.5 0.8
oil
Straw
0.9231 288 4.77 15.8 1.2
seal oil
Brown
0.9253 291 16.38 16.2 1.9
seal oil
Whale
0.9163 297 1.49 16.1 1.8
oil
Dark
whale 0.9284 303 12.60 21.8 2.4
oil
Japan
0.9336 296 4.79 26 0.67
fish oil
Japan
0.9325 302 10.43 28 1.55
fish oil
Brown
0.9260 313 14.91 21.8 1.9
cod oil
Pure
herring 0.9353 288 11.39 21.6 1.5
oil
Kipper
0.9271 297 5.14 22.7 3.25
oil

Waste Fats.—Under this classification may be included marrow fat, skin
greases, bone fats, animal grease, melted stuff from hotel and restaurant refuse,
and similar fatty products. The following is a fair typical selection:—

Saponification Acidity (as Oleic Acid) Per Titre,
Equivalent. Cent. °C.

Marrow fat 283.3 3.6 38.7
White skin
287.2 4.3 36.4
grease
Pale skin
286.3 9.87 35.7
grease
Pale bone fat 289.7 8.8 40.7
Brown bone fat 289.1 11.0 41
Brown bone fat 292 20.5 40.2
Animal grease 289.4 38.1 40.4
Melted stuff 286.3 12.8 37.7

The materials in the above class require to be carefully examined for the
presence of unsaponifiable matter, lime salts and other impurities.
Fatty Acids.—We have already described the various methods of liberating
fatty acids by hydrolysis or saponification.
Under this heading should also be included stearines produced by submitting
distilled fat to hydraulic pressure, the distillates from e from unsaponifiable
matter, cocoa-nut oleine, a bye-product from the manufacture of edible cocoa-
nut butter and consisting largely of free acids, and palm-nut oleine obtained in
a similar manner from palm-nut oil.
These are all available for soap-making.

Less-known Oils and Fats of Limited Use.

Shea Butter.—Shea butter is extracted from the kernels of the Bassia Parkii
and exported from Africa and Eastern India. This fat is somewhat tough and
sticky, and the amount of unsaponifiable matter present is sometimes
considerable. Samples examined by us gave the following data:—

Saponification Acidity (as Oleic Acid) Titre, Refractive Index at
Equivalent. Per Cent. °C. 60° C.
313 8.2 53.2 1.4566
303 7.33 53 1.4558
1.4471 (F. Acids)

Mowrah-seed Oil.—The mowrah-seed oil now offered for soap-making is
derived from the seeds of Bassia longifolia and Bassia latifolia. It is largely
exported from India to Belgium, France and England. The following are the
results of some analyses made by us:—

Saponification Acidity (as Oleic Acid) Titre, Refractive Index at
Equivalent. Per Cent. °C. 60° C.
291 10 43.4 1.4518
291.5 7.1 42.7 ...
291.2 9.9 43.8 ...
292 11.26 40.5 ...

Chinese vegetable tallow is the name given to the fat which is found coating
the seeds of the "tallow tree" (Stillingia sebifera) which is indigenous to China
and has been introduced to India where it flourishes. The following is a typical
sample:—

Saponification Equivalent Acidity Per Cent. Titre, °C.
280.2 5.24 52.5

The seeds of the "tallow tree" yield an oil (stillingia oil) having drying
properties.
Borneo Tallow.—The kernels of several species of Hopea (or Dipterocarpus),
which flourish in the Malayan Archipelago, yield a fat known locally as
Tangawang fat. This fat is moulded (by means of bamboo canes) into the form
of rolls about 3 inches thick, and exported to Europe as Borneo Tallow.
A sample tested by one of us gave the following data:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent. Titre, °C.
292 36 50.8

Kapok oil is produced from a tree which is extensively grown in the East and
West Indies. The Dutch have placed it on the market and the figures given by
Henriques (Chem. Zeit., 17, 1283) and Philippe (Monit. Scient., 1902, 730),
although varying somewhat, show the oil to be similar to cotton-seed oil.

Various New Fats and Oils Suggested for Soap-making.

Carapa or Andiroba oil, derived from the seeds of a tree (Carapa Guianensis)
grown in West Indies and tropical America, has been suggested as suitable for
soap-making. Deering (Imperial Institute Journ., 1898, 313) gives the
following figures:—

Saponification Equivalent. Acidity Per Cent. Melting Point of Fatty Acids, °C.
287 12 89

Another observer (Rev. Chem. Ind., 13, 116) gives the setting point of the fatty
acids as 56.4° C.
Candle-nut oil obtained from the seeds of a tree flourishing in India and also
the South Sea Islands.
The following figures have been published:—

Saponification Titre, Iodine
Observers. References.
Equivalent.[1] °C. No.
136.3- Chem. Centr., 1898, p.
299-304.9 13 De Negri
139.3 493.
Chem. Revue, 1901, p.
291 ... 163.7 Lewkowitsch
156.
Farben-Zeitung, 1903,
296 12.5 152.8 Kassler
p. 359.

Curcas oil is produced in Portugal from the seeds of the "purging nut tree,"
which is similar to the castor oil plant, and is cultivated in Cape Verde Islands
and other Portuguese Colonies.
The following data have been observed:—

Saponification Titre, Iodine
Observers. References.
Equivalent.[2] °C. No.
J. S. C. Ind., 1898, p.
291.4 0.36 99.5 Archbut
1010.
Chem. Revue, 1898, p.
290.3 4.46 98.3 Lewkowitsch
211.
Zeits. angew. Chem.,
283.1 0.68 107.9 Klein
1898, p. 1012.

The titre is quoted by Lewkowitsch as 28.6° C.
Goa butter or Kokum butter is a solid fat obtained from the seeds of
Garcinia indica, which flourishes in India and the East Indies. Crossley and
Le Sueur (Journ. Soc. Chem. Industry, 1898, p. 993) during an investigation
of Indian oils obtained these results:—

Saponification Equivalent.[3] Acidity Per Cent. Iodine No.
300 7.1 34.2

Safflower oil is extracted from the seeds of the Carthamus tinctorius,
which, although indigenous to India and the East Indies, is extensively
cultivated in Southern Russia (Saratowa) and German East Africa. Its use
has been suggested for soft-soap making. The following figures have been
published:—

Saponification Titre, Iodine
Observers. References.
Equivalent.[4] °C. No.
J. S. C. Ind., 1898, p.
Average of Twelve Crossley and
295.5 141.29 992; J. S. C. Ind., 1900,
Samples Le Sueur
p. 104.
Chem. Revue, 1901, p.
287.1 141.6 Shukoff
250.
Chem. Revue, 1902, p.
289.2 130 Tylaikow
106.
Chem. Zeitung, 1904, p.
293.7 142.2 Fendler
867.

Maripa fat is obtained from the kernels of a palm tree flourishing in the
West Indies, but, doubtless, the commercial fat is obtained from other trees
of the same family. It resembles cocoa-nut oil and gives the following
figures:—

Saponification Iodine Melting Point of
Observer. Reference.
Equivalent.[5] No. Fatty Acids, °C.
J. S. C. Ind.,
217 9.49 25 Bassière
1903, p. 1137.

Niam fat, obtained from the seeds of Lophira alata, which are found
extensively in the Soudan. The fat, as prepared by natives, has been
examined by Lewkowitsch, and more recently Edie has published the
results of an analysis. The figures are as follows:—

Saponification Titre, Iodine
Observers. References.
Equivalent.[6] °C. No.
J. S. C. Ind., 1907, p.
295.1 78.12 42.5 Lewkowitsch
1266.
Quart. J. Inst. Comm.
287.7 75.3 Edïe.
Research in Tropics.

Cohune-nut oil is produced from the nuts of the cohune palm, which
flourishes in British Honduras. This oil closely resembles cocoa-nut and
palm-nut oils and is stated to saponify readily and yield a soap free from
odour. The following figures, obtained in the Laboratory of the Imperial
Institute, are recorded in the official Bulletin, 1903, p. 25:—

Saponification Equivalent.Iodine No. Melting Point of Fatty Acids, °C.
253.9-255.3 12.9-13.6 27-30

Mafoureira or Mafura tallow from the nuts of the mafoureira tree, which
grows wild in Portuguese East Africa. The following figures are published:
—

Saponification Iodine
References.
Equivalent. No.

Titre, °C.
De Negri and Fabris, Annal. del
253.8 44-48 46.14 Lab. Chim. Delle Gabelle,
1891-2, p. 271.
Acidity (as
Oleic Acid) Per
Cent.
47.8-
232.8-233.7 21.26 Bulletin Imp. Inst., 1903, p. 27.
55.8

Pongam oil, obtained from the beans of the pongam tree, which flourishes
in East India, has been suggested as available for the soap industry, but the
unsaponifiable matter present would militate against its use. Lewkowitsch
(Analyst, 1903, pp. 342-44) quotes these results:—

Saponification Iodine Acidity, Per Unsaponifiable, Per
Equivalent.[7] No. Cent. Cent.
Oil extracted in
315 94 3.05 9.22
laboratory
Indian specimen 306 89.4 0.5 6.96

Margosa oil is obtained from the seeds of Melia azedarach, a tree which is
found in most parts of India and Burma.
Lewkowitsch (Analyst, 1903, pp. 342-344) gives these figures:—

Saponification Equivalent.[8] Iodine No. Titre, °C.
284.9 69.6 42

Dika fat or Wild Mango oil is obtained from the seed kernels of various
kinds of Irvingia by boiling with water. Lemarié (Bulletin Imp. Inst., 1903,
p. 206) states that this fat is used in the place of cocoa-nut oil in the
manufacture of soap. Lewkowitsch (Analyst, 1905, p. 395) examined a large
sample of dika fat obtained from seeds of Irvingia bateri (South Nigeria)
and gives the following data:—

Saponification Equivalent. Iodine Titre, Unsaponifiable, Per
[9] No. °C. Cent.
229.4 5.2 34.8 0.73

Baobab-seed Oil.—Balland (Journ. Pharm. Chem., 1904, p. 529, abstracted
in Journ. Soc. Chem. Ind., 1905, p. 34) states that the natives of Madagascar
extract, by means of boiling water, from the seeds of the baobab tree, a
whitish solid oil, free from rancidity, and possessed of an odour similar to
Tunisian olive oil. He suggests that it may, with advantage, replace cocoa-
nut oil in soap manufacture.
Persimmon-seed Oil.—Lane (J. S. C. Ind., 1905, p. 390) gives constants for
this oil which he describes as semi-drying, of brownish yellow colour, and
having taste and odour like pea-nut (arachis) oil. The following are taken
from Lane's figures:—

Saponification Equivalent.[10] Iodine No. Titre, °C.
298.4 115.6 20.2

Wheat oil, extracted from the wheat germ by means of solvents, has been
suggested as applicable for soap-making (H. Snyder, abstr. J. S. C. Ind.,
1905, p. 1074). The following figures have been published:—

Saponification Acidity, Iodine Titre,
Observers. References.
Equivalent.[11] Per Cent. No. °C.
Chem. Zeit.,
306 5.65 115.17 29.7 De Negri. 1898(abstr. J. S. C.,
1898, p. 1155).
J. Amer. C. Soc.,
Frankforter 1899, 758-769
297 20 115.64 ...
& Harding (abstr. in J. S. C. I.,
1899, p. 1030).

Tangkallah fat, from the seeds of a tree growing in Java and the
neighbouring islands, is suitable for soap-making. Schroeder (Arch. Pharm.,
1905, 635-640, abstracted in J. S. C. Ind., 1906, p. 128) gives these values:
—

Saponification Acidity, Per Iodine Unsaponifiable, Per
Equivalent.[12] Cent. No. Cent.
209 1.67 2.28 1.44

It is a hard fat, nearly white, possessing neither taste nor characteristic
odour and solidifying at about 27° C.
Oil of Inoy-kernel.—(Bulletin Imp. Inst., 1906, p. 201). The seeds of Poga
oleosa from West Africa yield on extraction an oil which gives the figures
quoted below, and is suggested as a soap-maker's material:—

Saponification Equivalent. Iodine No. Titre, °C.
304 89.75 22

Rosin.

Rosin is the residuum remaining after distillation of spirits of turpentine
from the crude oleo-resin exuded by several species of the pine, which
abound in America, particularly in North Carolina, and also flourish in
France and Spain. The gigantic forests of the United States consist
principally of the long-leaved pine, Pinus palustris (Australis), whilst the
French and Spanish oleo-resin is chiefly obtained from Pinus pinaster,
which is largely cultivated.
Rosin is a brittle, tasteless, transparent substance having a smooth shining
fracture and melting at about 135° C. (275° F.). The American variety
possesses a characteristic aromatic odour, which is lacking in those from
France and Spain. It is graded by samples taken out of the top of every
barrel, and cut into 7/8 of an inch cubes, which must be uniform in size—
the shade of colour of the cube determines its grade and value.
The grades are as follows:—
W. W. (Water white.)
W. G. (Window glass.)
N. (Extra pale.)
M. (Pale.)
K. (Low pale.)

I. (Good No. 1.)
H. (No. 1.)
G. (Low No. 1.)
F. (Good No. 2.)
E. (No. 2.)
D. (Good strain.)
C. (Strain.)
B. (Common strain.)
A. (Common.)
Unsaponifiable matter is present in rosin in varying amounts.
Below are a few typical figures taken from a large number of collated
determinations:—

Saponification Total Acid Free Acid Iodine
Equivalent. No. No. No.
American W.
330.5 169.7 119.1 126.9
W.
American N. 312.3 179.6 161.4 137.8
French 320.5 175 168 120.7
Spanish 313.4 179 160 129.8

Alkali (Caustic and Carbonated).

The manufacture of alkali was at one time carried on in conjunction with
soap-making, but of late years it has become more general for the soap
manufacturer to buy his caustic soda or carbonated alkali from the alkali-
maker.
Although there are some alkali-makers who invoice caustic soda and soda
ash in terms of actual percentage of sodium oxide (Na2O), it is the trade
custom to buy and sell on what is known as the English degree, which is
about 1 per cent. higher than this.
The English degree is a survival of the time when the atomic weight of
sodium was believed to be twenty-four instead of twenty-three, and, since

the error on 76 per cent. Na2O due to this amounts to about 1 per cent., may
be obtained by adding this figure to the sodium oxide really present.
Caustic soda (sodium hydrate) comes into commerce in a liquid form as
90° Tw. (and even as high as 106° Tw.), and other degrees of dilution, and
also in a solid form in various grades as 60°, 70°, 76-77°, 77-78°. These
degrees represent the percentage of sodium oxide (Na2O) present plus the 1
per cent. The highest grade, containing as it does more available caustic
soda and less impurities, is much more advantageous in use.
Carbonate of soda or soda ash, 58°, also termed "light ash," and "refined
alkali". This is a commercially pure sodium carbonate containing about 0.5
per cent. salt (NaCl). The 58° represents the English degrees and
corresponds to 99 per cent. sodium carbonate (Na2CO3).

Soda ash, 48°, sometimes called "caustic soda ash," often contains besides
carbonate of soda, 4 per cent. caustic soda (sodium hydrate), and 10 per
cent. salt (sodium chloride), together with water and impurities.
The 48 degrees refers to the amount of alkali present in terms of sodium
oxide (Na2O), but expressed as English degrees.

Caustic potash (potassium hydrate) is offered as a liquid of 50-52° B. (98-
103° Tw.) strength, and also in solid form as 75-80° and 88-92°. The
degrees in the latter case refer to the percentage of potassium hydrate
(KHO) actually present.
Carbonate of Potash.—The standard for refined carbonate of potash is 90-
92 per cent. of actual potassium carbonate (K2CO3) present, although it can
be obtained testing 95-98 per cent.

Other Materials.

Water.—Water intended for use in soap-making should be as soft as
possible. If the water supply is hard, it should be treated chemically; the
softening agents may be lime and soda ash together, soda ash alone, or
caustic soda. There are many excellent plants in vogue for water softening,
which are based on similar principles and merely vary in mechanical

arrangement. The advantages accruing from the softening of hard water
intended for steam-raising are sufficiently established and need not be
detailed here.
Salt (sodium chloride or common salt, NaCl) is a very important material to
the soap-maker, and is obtainable in a very pure state.
Brine, or a saturated solution of salt, is very convenient in soap-making,
and, if the salt used is pure, will contain 26.4 per cent. sodium chloride and
have a density of 41.6° Tw. (24.8° B.).
The presence of sulphates alters the density, and of course the sodium
chloride content.
Salt produced during the recovery of glycerine from the spent lyes often
contains sulphates, and the density of the brine made from this salt ranges
higher than 42° Tw. (25° B.).
Soapstock.—This substance is largely imported from America, where it is
produced from the dark-coloured residue, termed mucilage, obtained from
the refining of crude cotton-seed oil. Mucilage consists of cotton-seed oil
soap, together with the colouring and resinous principles separated during
the treatment of the crude oil. The colouring matter is removed by boiling
the mucilage with water and graining well with salt; this treatment is
repeated several times until the product is free from excess of colour, when
it is converted into soap and a nigre settled out from it.
Soapstock is sold on a fatty acid basis; the colour is variable.

FOOTNOTES:
[1] Calculated by us from saponification value.
[2] Calculated by us from saponification value.
[3] Calculated by us from saponification value.
[4] Calculated by us from saponification value.
[5] Calculated by us from saponification value.
[6] Calculated by us from saponification value.

[7] Calculated by us from saponification value.
[8] Calculated by us from saponification value.
[9] Calculated by us from saponification value.
[10] Calculated by us from saponification value.
[11] Calculated by us from saponification value.
[12] Calculated by us from saponification value.

CHAPTER IV.
BLEACHING AND TREATMENT OF RAW MATERIALS
INTENDED FOR SOAP-MAKING.

Palm Oil—Cotton-seed Oil—Cotton-seed "Foots"—Vegetable
Oils—Animal Fats—Bone Fat—Rosin.
Having described the most important and interesting oils and fats used or
suggested for use in the manufacture of soap, let us now consider briefly the
methods of bleaching and treating the raw materials, prior to their
transference to the soap-pan.
Crude Palm Oil.—Of the various methods suggested for bleaching palm
oil, the bichromate process originated by Watts is undoubtedly the best. The
reaction may be expressed by the following equation, though in practice it
is necessary to use twice the amount of acid required by theory:—
K2Cr2O7 + 14HCl = 2KCl + Cr2Cl6 + 7H2O + 6Cl.

6Cl + 3H2O = 6HCl + 3O.

The palm oil, freed from solid impurities by melting and subsidence, is
placed in the bleaching tank, and washed with water containing a little
hydrochloric acid. Having allowed it to rest, and drawn off the liquor and
sediment (chiefly sand), the palm oil is ready for treatment with the
bleaching reagent, which consists of potassium bichromate and commercial
muriatic acid. For every ton of oil, 22 to 28 lb. potassium bichromate and
45 to 60 lb. acid will be found sufficient to produce a good bleached oil.
The best procedure is to act upon the colouring matter of the oil three
successive times, using in the first two treatments one-third of the average
of the figures just given, and in the final treatment an appropriate quantity
which can be easily gauged by the appearance of a cooled sample of the oil.

The potassium bichromate is dissolved in hot water and added to the crude
palm oil, previously heated to 125° F. (52° C.), the requisite amount of
muriatic acid being then run in and the whole well agitated by means of air.
The bright red colour of the oil gradually changes to dark brown, and soon
becomes green. The action having proceeded for a few minutes, agitation is
stopped, and, after allowing to settle, the green liquor is withdrawn.
When sufficiently bleached the oil is finally washed (without further
heating) with hot water (which may contain salt), to remove the last traces
of chrome liquor.
If the above operation is carried out carefully, the colouring matter will be
completely oxidised.
It is important, however, that the temperature should not be allowed to rise
above 130° F. (54° C.) during the bleaching of palm oil, otherwise the
resultant oil on saponification is apt to yield a soap of a "foxy" colour. The
bleached oil retains the characteristic violet odour of the original oil.
It has been suggested to use dilute sulphuric acid, or a mixture of this and
common salt, in the place of muriatic acid in the above process.
Crude Cotton-seed Oil.—The deep colouring matter of crude cotton-seed
oil, together with the mucilaginous and resinous principles, are removed by
refining with caustic soda lye.
The chief aim of the refiner is to remove these impurities without
saponifying any of the neutral oil. The percentage of free fatty acids in the
oil will determine the quantity of caustic lye required, which must only be
sufficient to remove this acidity.
Having determined the amount of free acidity, the quantity of caustic soda
lye necessary to neutralise it is diluted with water to 12° or 15° Tw. (8° or
10° B.), and the refining process carried out in three stages. The oil is
placed in a suitable tank and heated by means of a closed steam coil to 100°
F. (38° C.), a third of the necessary weak caustic soda lye added in a fine
stream or by means of a sprinkler, and the whole well agitated with a
mechanical agitator or by blowing a current of air through a pipe laid on the
bottom of the tank.

Prolonged agitation with air has a tendency to oxidise the oil, which
increases its specific gravity and refractive index, and will be found in the
soap-pan to produce a reddish soap. As the treatment proceeds, the
temperature may be carefully raised, by means of the steam coil, to 120° F.
(49° C.).
The first treatment having proceeded fifteen minutes, the contents of the
tank are allowed to rest; the settling should be prolonged as much as
possible, say overnight, to allow the impurities to precipitate well, and carry
down the least amount of entangled oil. Having withdrawn these coloured
"foots," the second portion of the weak caustic soda solution is agitated
with the partially refined oil, and, when the latter is sufficiently treated, it is
allowed to rest and the settled coloured liquor drawn off as before. The oil
is now ready for the final treatment, which is performed in the same manner
as the two previous ones. On settling, a clear yellow oil separates.
If desired, the oil may be brightened and filtered, after refining to produce a
marketable article, but if it is being refined for own use in the soap-house,
this may be omitted.
The residue or "foots" produced during the refining of crude cotton-seed oil,
known in the trade as "mucilage," may be converted into "soapstock" as
mentioned in the preceding chapter, or decomposed by a mineral acid and
made into "black grease" ready for distillation by superheated steam.
Vegetable Oils.—The other vegetable oils come to the soap-maker's hand in
a refined condition; occasionally, however, it is desirable to remove a
portion of the free fatty acids, which treatment also causes the colouring
matter to be preciptated. This is effected by bringing the oil and a weak
solution of caustic lye into intimate contact. Cocoa-nut oil is often treated in
this manner. Sometimes it is only necessary to well agitate the oil with 1-
1/2 per cent. of its weight of a 12° Tw. (8° B.) solution of caustic soda and
allow to settle. The foots are utilised in the soap-pan.
Animal Fats.—Tallows are often greatly improved by the above alkaline
treatment at 165° F. (73° C.). It is one of the best methods and possesses
advantages over acid processes—the caustic soda removes the free acid and
bodies of aldehyde nature, which are most probably the result of oxidation

or polymerisation, whereas the neutral fat is not attacked, and further, the
alkaline foots can be used in the production of soap.
Bone fat often contains calcium (lime) salts, which are very objectionable
substances in a soap-pan. These impurities must be removed by a treatment
with hydrochloric or sulphuric acid. The former acid is preferable, as the
lime salt formed is readily soluble and easily removed. The fat is agitated
with a weak solution of acid in a lead-lined tank by blowing in steam, and
when the treatment is complete and the waste liquor withdrawn, the last
traces of acid are well washed out of the liquid fat with hot water.
Rosin.—Several methods have been suggested for bleaching rosin; in some
instances the constitution of the rosin is altered, and in others the cost is too
great or the process impracticable.
The aim of these processes must necessarily be the elimination of the
colouring matter without altering the original properties of the substance.
This is best carried out by converting the rosin into a resinate of soda by
boiling it with a solution of either caustic soda or carbonated alkali. The
process is commenced by heating 37 cwt. of 17° Tw. (11° B.) caustic soda
lye, and adding 20 cwt. of rosin, broken into pieces, and continuing the
boiling until all the resinate is homogeneous, when an addition of 1-1/2 cwt.
of salt is made and the boiling prolonged a little. On resting, the coloured
liquor rises to the surface of the resinate, and may be siphoned off (or
pumped away through a skimmer pipe) and the resinate further washed with
water containing a little salt.
The treatment with carbonated alkali is performed in a similar manner. A
solution, consisting of 2-3/4 cwt. of soda ash (58°), in about four times its
weight of water, is heated and 20 cwt. of rosin, broken into small pieces,
added. The whole is heated by means of the open steam coil, and care must
be taken to avoid boiling over. Owing to the liberation of CO2 gas, frothing
takes place. A large number of patents have been granted for the preparation
of resinate of soda, and many methods devised to obviate the boiling over.
Some suggest mixing the rosin and soda ash (or only a portion of the soda
ash) prior to dissolving in water; others saponify in a boiler connected with
a trap which returns the resinate to the pan and allows the carbonic-acid gas
to escape or to be collected.

With due precaution the method can be easily worked in open vessels, and,
using the above proportions, there will be sufficient uncombined rosin
remaining to allow the resultant product to be pumped into the soap with
which it is intended to intermix it, where it will be finally saponified
thoroughly.
The salt required, which, in the example given, would be 1-1/2 cwt., may be
added to the solution prior to the addition of rosin or sprinkled in towards
the finish of the boiling. When the whole has been sufficiently boiled and
allowed to rest, the liquor containing the colouring matter will float over the
resinate, and, after removal, may be replaced by another washing.
Many other methods have been suggested for the bleaching, refining and
treatment of materials intended for saponification, but the above practical
processes are successfully employed.
All fats and oils after being melted by the aid of steam must be allowed to
thoroughly settle, and the condensed water and impurities withdrawn
through a trap arrangement for collecting the fatty matter. The molten
settled fatty materials en route to the soap-pan should be passed through
sieves sufficiently fine to free them from suspended matter.

CHAPTER V.
SOAP-MAKING.

Classification of Soaps—Direct Combination of Fatty Acids with
Alkali—Cold Process Soaps—Saponification under Increased or
Diminished Pressure—Soft Soap—Marine Soap—Hydrated
Soaps, Smooth and Marbled—Pasting or Saponification—
Graining Out—Boiling on Strength—Fitting—Curd Soaps—
Curd Mottled—Blue and Grey Mottled Soaps—Milling Base—
Yellow Household Soaps—Resting of Pans and Settling of Soap
—Utilisation of Nigres—Transparent Soaps—Saponifying
Mineral Oil—Electrical Production of Soap.
Soaps are generally divided into two classes and designated "hard," and
"soft," the former being the soda salts, and the latter potash salts, of the
fatty acids contained in the material used.
According to their methods of manufacture, soaps may, however, be more
conveniently classified, thus:—
(A) Direct combination of fatty acids with alkali.
(B) Treatment of fat with definite amount of alkali and no separation of
waste lye.
(C) Treatment of fat with indefinite amount of alkali and no separation of
waste lye.
(D) Treatment of fat with indefinite amount of alkali and separation of
waste lye.
(A) Direct Combination of Fatty Acids with Alkali.—This method consists
in the complete saturation of fatty acids with alkali, and permits of the use
of the deglycerised products mentioned in chapter ii., section 2, and of
carbonated alkalies or caustic soda or potash. Fatty acids are readily
saponified with caustic soda or caustic potash of all strengths.

The saponification by means of carbonated alkali may be performed in an
open vat containing a steam coil, or in a pan provided with a removable
agitator.
It is usual to take soda ash (58°), amounting to 19 per cent. of the weight of
fatty acids to be saponified, and dissolve it in water by the aid of steam until
the density of the solution is 53° Tw. (30° B.); then bring to the boil, and,
whilst boiling, add the molten fatty acids slowly, but not continuously.
Combination takes place immediately with evolution of carbonic acid gas,
which causes the contents of the vat or pan to swell, and frequently to boil
over. The use of the agitator, or the cessation of the flow of fatty acids, will
sometimes tend to prevent the boiling over. It is imperative that the steam
should not be checked but boiling continued as vigorously as possible until
all the alkali has been absorbed and the gas driven off.
The use of air to replace steam in expelling the carbonic acid gas has been
patented (Fr. Pat. 333,974, 1903).
A better method of procedure, however, is to commence with a solution of
64° Tw. (35° B.) density, made from half the requisite soda ash (9-1/2 per
cent.), and when this amount of alkali has all been taken up by the fatty
acids (which have been added gradually and with continuous boiling), the
remaining quantity of soda ash is added in a dry state, being sprinkled over
each further addition of fatty acid.
This allows the process to be more easily controlled and boiling over is
avoided.
It is essential that the boiling by steam should be well maintained
throughout the process until all carbonic acid gas has been thoroughly
expelled; when that point is reached, the steam may be lessened and the
contents of the vat or pan gently boiled "on strength" with a little caustic lye
until it ceases to absorb caustic alkali, the soap being finished in the manner
described under (D).
It is extremely difficult to prevent discoloration of fatty acids, hence the
products of saponification in this way do not compare favourably in
appearance with those produced from the original neutral oil or fat.

(B) Treatment of Fat with Definite Amount of Alkali and no Separation of
Waste Lye.—Cold-process soap is a type of this class, and its method of
production is based upon the characteristic property which the glycerides of
the lower fatty acids (members of the cocoa-nut-oil class) possess of readily
combining with a strong caustic soda solution at a low temperature, and
evolving sufficient heat to complete the saponification.
Sometimes tallow, lard, cotton-seed oil, palm oil and even castor oil are
used in admixture with cocoa-nut oil. The process for such soap is the same
as when cocoa-nut oil is employed alone, with the slight alteration in
temperature necessary to render the fats liquid, and the amount of caustic
lye required will be less. Soaps made of these blends closely resemble, in
appearance, milled toilet soaps. In such mixtures the glycerides of the lower
fatty acids commence the saponification, and by means of the heat
generated induce the other materials, which alone would saponify with
difficulty or only with the application of heat, to follow suit.
It is necessary to use high grade materials; the oils and fats should be free
from excess of acidity, to which many of the defects of cold-process soaps
may be traced. Owing to the rapidity with which free acidity is neutralised
by caustic soda, granules of soap are formed, which in the presence of
strong caustic lye are "grained out" and difficult to remove without
increasing the heat; the soap will thus tend to become thick and gritty and
sometimes discoloured.
The caustic lye should be made from the purest caustic soda, containing as
little carbonate as possible; the water used for dissolving or diluting the
caustic soda should be soft (i.e., free from calcium and magnesium salts),
and all the materials carefully freed from particles of dirt and fibre by
straining.
The temperature, which, of course, must vary with the season, should be as
low as is consistent with fluidity, and for cocoa-nut oil alone may be 75° F.
(24° C.), but in mixtures containing tallow 100° to 120° F. (38° to 49° C.).
The process is generally carried out as follows:—
The fluid cocoa-nut oil is stirred in a suitable vessel with half its weight of
71.4° Tw. (38° B.) caustic soda lye at the same temperature, and, when

thoroughly mixed, the pan is covered and allowed to rest. It is imperative
that the oils and fats and caustic lye should be intimately incorporated or
emulsified. The agitating may be done mechanically, there being several
machines specially constructed for the purpose. In one of the latest designs
the caustic lye is delivered through a pipe which rotates with the stirring
gear, and the whole is driven by means of a motor.
The agitation being complete, chemical action takes place with the
generation of heat, and finally results in the saponification of the fats.
At first the contents of the pan are thin, but in a few hours they become a
solid mass. As the process advances the edges of the soap become more
transparent, and when the transparency has extended to the whole mass, the
soap is ready, after perfuming, to be framed and crutched.
The admixture of a little caustic potash with the caustic soda greatly
improves the appearance of the resultant product, which is smoother and
milder.
The glycerine liberated during the saponification is retained in the soap.
Although it is possible, with care, to produce neutral soaps of good
appearance and firm touch by this method, cold-process soaps are very
liable to contain both free alkali and unsaponified fat, and have now fallen
considerably into disrepute.
Saponification under Increased or Diminished Pressure.—Soaps made by
boiling fats and oils, under pressure and in vacuo, with the exact quantity of
caustic soda necessary for complete combination, belong also to this class.
Amongst the many attempts which have at various times been made to
shorten the process of soap-making may be mentioned Haywood's Patent
No. 759, 1901, and Jourdan's French Patent No. 339,154, 1903.
In the former, saponification is carried out in a steam-jacketed vacuum
chamber provided with an elaborate arrangement of stirrers; in the other
process fat is allowed to fall in a thin stream into the amount of lye required
for saponification, previously placed in the saponification vessel, which is
provided with stirring gear.

When the quantities have been added, steam is admitted and saponification
proceeds.
(C) Treatment of Fat with Indefinite Amount of Alkali and no Separation of
Waste Lye.—Soft soap is representative of this class. The vegetable fluid
oils (linseed, olive, cotton-seed, maize) are for the most part used in making
this soap, though occasionally bone fats and tallow are employed. Rosin is
sometimes added, the proportion ranging, according to the grade of soap
required, from 5 to 15 per cent. of the fatty matter.
The Soft Soap Manufacturers' Convention of Holland stipulate that the
materials used in soft-soap making must not contain more than 5 per cent.
rosin; it is also interesting to note that a patent has been granted (Eng. Pat.
17,278, 1900) for the manufacture of soft soap from material containing 50
per cent. rosin.
Fish or marine animal oils—whale, seal, etc., once largely used as raw
material for soft soap, have been superseded by vegetable oils.
The materials must be varied according to the season; during hot weather,
more body with a less tendency to separate is given by the introduction of
oils and fats richer in stearine; these materials also induce "figging".
The most important material, however, is the caustic potash lye which
should average 40° Tw. (24° B.), i.e., if a weak solution is used to
commence saponification, a stronger lye must be afterwards employed to
avoid excess of water in the soap, and these average 40° Tw. (24° B.). The
potash lye must contain carbonates, which help to give transparency to the
resultant soap. If the lye is somewhat deficient in carbonates, they may be
added in the form of a solution of refined pearl ash (potassium carbonate).
Caustic soda lye is sometimes admixed, to the extent of one-fourth, with
potash lye to keep the soap firmer during hot weather, but it requires great
care, as a slight excess of soda gives soft soap a bad appearance and a
tendency to separate.
The process is commenced by running fatty matter and weak potash lyes
into the pan or copper, and boiling together, whilst the introduction of oil
and potash lye is continued.

The saponification commences when an emulsion forms, and the lye is then
run in more quickly to prevent the mass thickening.
Having added sufficient "strength" for complete saponification, the boiling
is continued until the soap becomes clear.
The condition of the soap is judged by observing the behaviour of a small
sample taken from the pan and dropped on glass or iron. If the soap is
satisfactory it will set firm, have a short texture and slightly opaque edge,
and be quite clear when held towards the light. If the cooled sample draws
out in threads, there is an excess of water present. If an opaque edge
appears and vanishes, the soap requires more lye. If the sample is turbid and
somewhat white, the soap is too alkaline and needs more oil.
The glycerine liberated during saponification is contained in the soap and
no doubt plays a part in the production of transparency.
Hydrated soaps, both smooth and marbled, are included in this
classification, but are soda soaps. Soap made from cocoa-nut oil and palm-
kernel oil will admit of the incorporation of large quantities of a solution of
either salt, carbonate of soda, or silicate of soda, without separation, and
will retain its firmness. These materials are, therefore, particularly adapted
for the manufacture of marine soaps, which often contain as much as 80 per
cent. of water, and, being soluble in brine, are capable of use in sea-water.
For the same reason, cocoa-nut oil enters largely into the constitution of
hydrated soaps, but the desired yield or grade of soap allows of a variation
in the choice of materials. Whilst marine soap, for example, is usually made
from cocoa-nut oil or palm-kernel oil only, a charge of 2/3 cocoa-nut oil and
1/3 tallow, or even 2/3 tallow and 1/3 cocoa-nut oil, will produce a paste
which can carry the solutions of silicate, carbonate, and salt without
separation, and yield a smooth, firm soap.
The fatty materials, carefully strained and freed from particles of dirt and
fibre, are boiled with weak caustic soda lye until combination has taken
place. Saponification being complete, the solution of salt is added, then the
carbonate of soda solution, and finally the silicate of soda solution, after
which the soap is boiled. When thoroughly mixed, steam is shut off, and the
soap is ready for framing.

The marbled hydrated soap is made from cocoa-nut oil or a mixture of
palm-kernel oil and cocoa-nut oil with the aid of caustic soda lye 32-1/2°
Tw. (20° B.). As soon as saponification is complete, the brine and carbonate
of soda solution are added, and the pan allowed to rest.
The soap is then carefully tasted as to its suitability for marbling by taking
samples and mixing with the colouring solution (ultramarine mixed with
water or silicate of soda solution). If the sample becomes blue throughout,
the soap is too alkaline; if the colour is precipitated, the soap is deficient in
alkali. The right point has been reached when the marbling is distributed
evenly. Having thus ascertained the condition of the pan, and corrected it if
necessary, the colour, mixed in water or in silicate of soda solution, is added
and the soap framed.
(D) Treatment of Fat with Indefinite Amount of Alkali and Separation of
Waste Lye.—This is the most general method of soap-making. The various
operations are:—
(a) Pasting or saponification.
(b) Graining out or separation.
(c) Boiling on strength.
And in the case of milling soap base and household soaps,
(d) Fitting.
(a) Pasting or Saponification.—The melted fats and oils are introduced into
the soap-pan and boiled by means of open steam with a caustic soda lye 14°
to 23.5° Tw. (10° to 15° B.). Whether the fatty matters and alkali are run
into the pan simultaneously or separately is immaterial, provided the alkali
is not added in sufficient excess to retard the union.
The commencement of the saponification is denoted by the formation of an
emulsion. Sometimes it is difficult to start the saponification; the presence
of soap will often assist this by emulsifying the fat and thus bringing it into
intimate contact with the caustic soda solution.
When the action has started, caustic soda lye of a greater density, 29° to 33°
Tw. (18° to 20° B.), is frequently added, with continued boiling, in small

quantities as long as it is being absorbed, which is ascertained by taking out
samples from time to time and examining them.
There should be no greasiness in the sample, but when pressed between
finger and thumb it must be firm and dry.
Boiling is continued until the faint caustic taste on applying the cooled
sample to the tongue is permanent, when it is ready for "graining out". The
pasty mass now consists of the soda salts of the fat (as imperfect soap,
probably containing emulsified diglycerides and monoglycerides), together
with water, in which is dissolved the glycerine formed by the union of the
liberated glyceryl radicle from the fat with the hydroxyl radicle of the
caustic soda, and any slight excess of caustic soda and carbonates. The
object of the next operation is to separate this water (spent lye) from the
soap.
(b) Graining Out or Separation.—This is brought about by the use of
common salt, in a dry form or in solution as brine, or by caustic soda lye.
Whilst the soap is boiling, the salt is spread uniformly over its surface, or
brine 40° Tw. (24° B.) is run in, and the whole well boiled together. The
soap must be thoroughly boiled after each addition of salt, and care taken
that too large a quantity is not added at once.
As the soap is gradually thrown out of solution, it loses its smooth
transparent appearance, and becomes opaque and granular.
When a sample, taken out on a wooden trowel, consists of distinct grains of
soap and a liquid portion, which will easily separate, sufficient salt or brine
has been added; the boiling is stopped and the spent lye allowed to settle
out, whilst the soap remains on the surface as a more or less thick mass.
The separated spent lye consists of a solution of common salt, glycerine,
and alkaline salts; the preparation of crude glycerine therefrom is
considered in chapter ix.
The degree of separation of water (spent lye) depends upon the amount of
precipitant used. The aim is to obtain a maximum amount of spent lye
separated by the use of a minimum quantity of salt.

The amount of salt required for "graining out" varies with the raw material
used. A tallow soap is the most easily grained, more salt is required for
cotton-seed oil soap, whereas soaps made from cocoa-nut and palm-kernel
oils require very large amounts of salt to grain out thoroughly. Owing to the
solubility in weak brine of these latter soaps, it is preferable to grain them
with caustic soda lye. This is effected by adding, during boiling, sufficient
caustic lye (32-1/2° Tw., 20° B.) to produce the separation of the granules of
soap. The whole is allowed to rest; the separated half-spent lye is
withdrawn and may be used for the pasting of fresh materials.
After the removal of the settled lye, the grained mass is boiled with
sufficient water to dissolve the grain and make it smooth ("close" it), and is
now ready for the next operation of "boiling on strength".
(c) Boiling on Strength or Clear Boiling.—This is the most important
operation and is often termed "making the soap". The object is to harden the
soap and to ensure complete saponification.
Caustic soda lye (32-1/2° Tw., 20° B.) is gradually added until the soap is
again opened or grained, and boiling continued by the use of the dry steam
coil. As soon as the caustic soda lye is absorbed, another portion is slowly
added, and this is continued until the caustic soda or "strength" remains
permanent and the soapy mass, refusing to absorb more, is thrown out of
solution and grained. The granular mass will boil steadily, and the boiling
should be prolonged, as the last traces of neutral oil are difficult to
completely saturate with alkali. Thorough saponification takes place
gradually, and the operation cannot be hurried; special care has to be
bestowed upon this operation to effect the complete combination of fat and
alkali.
After resting for several hours, half-spent lye settles to the bottom of the
pan. In the case of yellow soaps or milling bases the settled lye is removed
to a suitable receptacle and reserved for use in the saponification of other
material, and the soap is then ready for the final operation of "fitting".
(d) Fitting.—If the operations just described have been properly performed,
the fitting should present no difficulty. The soap is boiled with open steam,
and water added until the desired degree of closing is attained. As the water
is thoroughly intermixed throughout the mass the thick paste gradually

becomes reduced to a smooth, thin consistence. Samples are tested from
time to time as to their behaviour in dropping off a hot trowel held
sideways; the thin layer should drop off in two or three flakes and leave the
surface of the trowel clean and dry. The soap is then in a condition to allow
the impurities to gravitate. According to the required soap, the fit may be
"coarse" ("open") when the flakes drop off the trowel readily, or "fine"
("close") when the flakes only leave the trowel with difficulty.
If the dilution with water has been allowed to proceed too far, and too fine a
fit is produced, which would be denoted by the layer of soap not leaving the
trowel, a little caustic lye or brine may be very carefully added and the
whole well boiled until the desired condition is obtained.
A good pressure of steam is now applied to the pan, causing the contents to
swell as high as possible, this greatly facilitating the settling of impurities;
steam is then turned off, the pan covered, and the boil allowed to rest for
several days.
The art of fitting consists in leaving the contents of the pan in such a
condition that, on standing, all the impurities precipitate, and the settled
soap, containing the correct amount of water, is clear and bright.
The above is a general practical outline of the ordinary soap-boiling
process. It may be modified or slightly altered according to the fancy of the
individual soap-maker or the particular material it is desired to use. Fats and
oils not only vary in the amount of alkali they absorb during saponification,
but also differ in the strength of the alkali they require. Tallow and palm oil
require lye of a density of 15° to 18° Tw. (10° to 12° B.), but cocoa-nut oil
alone would not saponify unless the lye was more concentrated, 33° to 42°
Tw. (20° to 25° B.). Cotton-seed oil requires weak lyes for saponification,
and, being difficult to saponify alone even with prolonged boiling, is
generally mixed with animal fat.
When fats are mixed together, however, their varying alkali requirements
become modified, and once the saponification is begun with weak lye, other
materials are induced to take up alkali of a strength with which alone they
would not combine.

It is considered the best procedure to commence the pasting or
saponification with weak lye.
In order to economise tank space, it is the general practice to store strong
caustic lye (60° to 70° Tw., 33° to 37° B.) and to dilute it as it is being
added to the soap-pan by the simultaneous addition of water.
Many manufacturers give all their soap a "brine wash" to remove the last
traces of glycerine and free the soap from carbonates. This operation takes
place prior to "fitting"; sufficient water is added to the boiling soap to
"close" it and then brine is run in to "grain" it.
After resting, the liquor is withdrawn.
Having described the necessary operations in general, we will now consider
their application to the preparation of various kinds of hard soap.
Curd Soaps.—Tallow is largely used in the manufacture of white curd
soaps, but cocoa-nut oil sometimes enters into their composition.
The first three operations above described, viz., pasting, graining out, and
boiling on strength, are proceeded with; the clear boiling by means of a
closed steam coil is continued until the "head" is boiled out and the soap is
free from froth. A sample taken and cooled should be hard. Boiling is then
stopped, and, after covering, the pan is allowed to rest for eight to ten hours,
when the soap is ready for filling into frames, where it is crutched until
perfectly smooth.
Curd mottled is usually made from melted kitchen stuff and bone grease.
Its preparation is substantially the same as for curd soap, but the clear
boiling is not carried so far. The art of curd mottled soap-making lies in the
boiling. If boiled too long the mottling will not form properly, and, on the
other hand, insufficient boiling will cause the soap to contain an excess of
entangled lye. Having boiled it to its correct concentration the pan is
allowed to rest about two hours, after which the soap is ready for framing,
which should be done expeditiously and the frames covered up.
Some lye, containing the impurities from the fats used, remains in the
interstices of the curd, unable to sink, and as the soap cools it is enclosed

and forms the mottling. The mottling may, therefore, be considered as a
crystallisation of the soap, in which the impurity forms the colour.
Blue and Grey Mottled Soaps.—These are silicated or liquored soaps in
which the natural mottling, due to the impure materials used in the early
days of soap-making, is imitated by artificial mottling, and are,
consequently, entirely different to curd mottled soaps.
The materials employed in making mottled soap comprise bleached palm
oil, tallow, bone fat, cocoa-nut oil, palm-kernel oil, cotton-seed oil, and, in
some instances, rosin.
The choice of a charge will naturally depend upon the cost; the property of
absorbing a large amount of liquor, which is characteristic of soaps made
from cocoa-nut oil and palm-kernel oil, is taken advantage of, as are also
the physical properties of the various fats and oils, with a view to the
crystallisation of the resultant soap and the development of the mottle. The
fat is saponified, grained and boiled on strength, as previously described.
After withdrawing the half-spent lye, the soap is just closed by boiling with
water, and is then ready for the silicate or other saline additions.
Soap intended to be liquored with silicate of soda should be distinctly
strong in free alkali; the crystalline nature of the soap is increased thereby,
and the mottled effect intensified. Some makers, however, fit the soap
coarsely and allow a nigre to deposit; then, after removing the nigre, or
transferring the settled soap to another copper, containing scraps of mottled
soap, get the soap into a condition for mottling, and add the silicate of soda
solution. To every 1 cwt. of soap, 28 lb. of silicate of soda solution, 32-1/2°
Tw. (20° B.) is added, whilst boiling; the strength of the silicate solution,
however, will depend upon the proportion of cocoa-nut oil and palm-kernel
oil present in the charge. Many soap-makers use 20° Tw. (13° B.) (cold)
silicate solution, whilst others prefer 140° Tw. (59.5° B.), with the gradual
addition of water to the soap, kept boiling, until the product is in the correct
mottling condition, and others, again, use bleach liquor, soda crystals, pearl
ash, and salt, together with silicate solution.
Considerable skill and experience is necessary to discern when the soap
acquires the correct mottling state. It should drop off the spatula in large

thick flakes, take considerable time to set, and the surface should not be
glossy.
When this mottling condition has been obtained, the colouring matter,
which would be ultramarine for the blue mottled and manganese dioxide for
the grey mottled soap (3-4 lb. ultramarine or 1-3 lb. manganese dioxide
being sufficient for 1 ton of soap), is mixed with a little water and added to
the boiling soap—the boiling is continued until all is thoroughly
amalgamated, and when the steam is shut off the contents of the pan are
ready for cleansing.
Mottled soap is run into wooden frames, which, when full, are covered over
and allowed to cool very gradually. On cooling slowly, large crystals are
produced which result in a distinct bold mottle; if the cooling is too rapid, a
small crystal is obtained and the mottle is not distributed, resulting in either
a small mottle, or no mottle at all, and merely a general coloration. In fact,
the entire art of mottling soap consists in properly balancing the saline
solutions and colouring matter, so that the latter is properly distributed
throughout the soap, and does not either separate in coloured masses at the
bottom of the frame, or uniformly colour the whole mass.
A sample of the soap should test 45 per cent. fatty acids, and the amount of
salt would range from 1/2 to 1 per cent.
Some of the English mottled soaps, especially those made from materials
which give a yellow-coloured ground, are bleached by soaking in brine, or
pickling in brine containing 2 per cent. of bleach liquor. The resultant soap
has a white ground and is firm. The bleach liquor may be made by mixing 1
cwt. bleaching powder with 10 cwts. of soda ash solution (15° Tw., 10° B.),
allowing to settle, and using the clear liquid, or by mixing 2 parts soda ash
solution with 1 part of bleaching powder solution, both solutions being 30°
Tw. (18.8° B.).
Milling-base.—The materials generally used are tallows and cocoa-nut oils
of the finest quality. The tallow is thoroughly saponified first, and the
graining is performed by the aid of caustic soda lye in preference to salt.
The half-spent lyes are withdrawn, and the cocoa-nut oil added to the pan.
This is saponified, and when the saponification is complete, "boiling-on-
strength" is proceeded with. Special care should be devoted to the "boiling-

on-strength" operation—its value in good soap-making cannot be over-rated
—and perfect saponification must be ensured. The half-spent lyes are
allowed to deposit during the night, and the soap must be carefully
examined next morning to ascertain if any alkali has been absorbed. If the
caustic taste is permanent the strengthening operation is complete, but
should any caustic have been absorbed, further addition of alkali must be
made and the boiling continued. These remarks apply equally to all soaps.
The soap, when ready, is fitted.
Bleached palm oil, olive oil, castor oil and lard are also employed in the
production of special milling soap bases, a palm oil soap being specially
suitable for the production of a violet-scented toilet soap.
Yellow Household Soaps. (a) Bar Soaps.—These are made from tallow with
an admixture of from 15-25 per cent. rosin. The best quality is known in the
South and West of England as Primrose Soap, but is designated in the North
of England by such names as Golden Pale, Imperial Pale, Gold Medal Pale,
etc. Tallow alone produces a very hard soap of inferior lathering qualities;
but rosin combines with alkali to form a soft body, which, although not a
soap in the strict sense of the term, is readily soluble in water, and in
admixture with the durable tallow soap renders it more soluble in water and
thereby increases its lathering properties.
The rosin may be added to the soap-pan after a previous partial
saponification with soda ash, and removal of colouring matter, and finally
saponified with caustic soda lye, or, as is more generally adopted, as a rosin
change. The pan is opened with caustic soda lye and saturation of the rosin
takes place rapidly; when completely saponified it is grained with salt, and
the coloured lye allowed to deposit and finally withdrawn.
The four operations already detailed apply to this soap.
Cheaper pale soaps may be made from lower grades of tallow and rosin and
are generally silicated.
(b) Tablet or Washer Type.—A demand has arisen for soap of free lathering
qualities, which has become very popular for general household use. This
soap is usually made from a mixture of cotton-seed oil, tallow, and cocoa-
nut oil, with a varying amount of rosin. The tallow yields firmness and

durability whilst the other constituents all assist in the more ready
production of a copious lather.
As to what amount of rosin can be used to yield a finished soap of sufficient
body and satisfactory colour, this naturally depends upon the grade of raw
material at the soap-makers' disposal. Those fats and oils which yield firm
soaps, will, of course, allow a greater proportion of rosin to be incorporated
with them than materials producing soaps of less body. Rosin imparts
softness to a soap, and also colour.
This is a fitted soap and full details of manufacture have already been
given.
Cheaper soaps are produced from lower grade materials hardened with
alkaline solutions.
Resting of Pans and Settling of Soap.—The fitted soap is allowed to settle
from four to six days. The period allowed for resting is influenced,
however, not only by the size of the boil, and the season, but also by the
composition of the soap, for if the base has been made from firm stock it is
liable to cool quicker than a soap produced from soft-bodied materials.
On subsidence, the contents of the pan will have divided into the following:
—
First. On top, a thin crust of soap, with perhaps a little light coloured fob,
which is returned to the pan after the removal of the good soap.
Second. The good settled soap, testing 62-63 per cent. fatty acids. The
subject of removing and treatment of this layer is fully dealt with in the next
chapter.
Third. A layer of darker weak soap, termed "nigre," which on an average
tests 33 per cent. fatty acids, and, according to the particular fit employed,
will amount to from 15-20 per cent. of the total quantity of soap in the pan.
The quantity of nigre may vary not only with the amount of water added
during finishing, but is also influenced by the amount of caustic alkali
remaining in the soap paste prior to fitting. If the free caustic alkali-content
is high, the soap will require a large amount of water to attain the desired

fit. This water renders the caustic into a lye sufficiently weak to dissolve a
quantity of soap, consequently, as the "nigre" is a weak solution of soap
together with any excess of alkali (caustic or carbonate) and salt which
gravitates during the settling, the quantity is increased.
Fourth. A solution containing alkaline salts, mostly carbonates and
chlorides, with a little caustic.
The amount of the layer is very variable, and doubtless, under certain
physical conditions, this liquor has separated from the nigre.
Utilisation of Nigres.—The nigres are boiled and the liquor separated by
graining with salt. Nigre may be utilised in various ways.
(1) It may be used several times with new materials. This particularly refers
to soaps of the "Washer" type. The colour of the nigre will determine the
number of times it can be employed.
(2) It may be incorporated with a soap of a lower grade than the one from
which it was obtained. In this case a system is generally adopted; for
example, soap of the best quality is made in a clean pan, the nigre
remaining is worked up with fresh material for soap of the next quality, the
nigre from that boil, in its turn, is admixed with a charge to produce a batch
of third quality, and the deposited nigre from this is again used for a fourth
quality soap—the nigre obtained from this latter boil would probably be
transferred into the cheapened "washer" or perhaps if it was dark in colour
into the brown soap-pan.
(3) The nigre may be fitted and produce a soap similar to the original soap
from which it was deposited. It is advisable to saponify a little fat with it.
(4) Nigres from several boils of the same kind of soap can be collected,
boiled, and fitted. The settled portion may be incorporated with a new
charging to keep the resultant soap uniform in colour—unless this is done,
the difference in colour between boils from new materials alone, and those
containing nigre, is very noticeable. The nigre settled from this fitted nigre
boil would be utilised in brown soap.
(5) According to its colour, and consistence, a nigre may be suitable for the
production of disinfectant, or cold-water soaps.

(6) Nigre may be bleached by treatment with a 20 per cent. solution of
stannous chloride—1 cwt. of this solution (previously heated) is sufficient
to bleach 20 tons of nigre.
Transparent Soaps.—The production of transparent soaps has recently been
fully studied, from a theoretical point of view, by Richardson (J. Amer.
Chem. Soc., 1908, pp. 414-20), who concludes that the function of
substances inducing transparency, is to produce a jelly and retard
crystallisation.
The old-fashioned transparent soap is prepared by dissolving, previously
dried, genuine yellow soap in alcohol, and allowing the insoluble saline
impurities to be deposited and removed. The alcoholic soap solution is then
placed in a distillation apparatus, or the pan containing the solution is
attached by means of a still head to a condenser, and the alcohol distilled,
condensed and regained. The remaining liquid soap, which may be coloured
and perfumed, is run into frames and allowed to solidify.
The resultant mass is somewhat turbid, but after storage in a room at 95° F.
(35° C.) for several months, becomes transparent.
The formation of the transparency is sometimes assisted and hastened by
the addition of glycerine or a solution of cane-sugar.
A patent has been granted to A. Ruch (Fr. Pat. 327,293, 1902) for the
manufacture of transparent glycerine soap by heating in a closed vessel
fatty acids together with the requisite quantity of alcoholic caustic soda
solution necessary for saponification, and cooling the resultant soap. It is
also proposed to add sugar solution.
Cheaper qualities of transparent soaps are made by the cold process with or
without the aid of alcohol and castor oil, and with the assistance of
glycerine or cane-sugar.
With the continual demand for cheaper production, sugar solution has
gradually, in conjunction with castor oil, which produces transparency,
superseded the use of alcohol and glycerine.
For a small batch, 56 lb. Cochin cocoa-nut oil and 56 lb. sweet edible tallow
may be taken, melted at 130° F. (54° C.), and carefully strained into a small

steam-jacketed pan. It is imperative that the materials should be of the
highest quality and perfectly clean. Twenty-three lb. of pure glycerine and
56 lb. of bright caustic soda solution made from high grade caustic and
having a density of 72° Tw. (38° B.) are crutched into the fat; the alcohol,
which would be 45 lb. in this example, is then added. The whole must be
most intimately incorporated, and the pan covered and allowed to rest for
one hour or one and a half hours. Saponification should ensue.
To produce a transparent glycerine soap with the aid of castor oil, and with
or without the use of alcohol, the following is the procedure:—
Cochin cocoa-nut oil, sweet edible tallow, and castor oil, of each 56 lb. are
taken, warmed to 130° F. (54° C.), and carefully strained into the jacketed
pan. If it is desired to use glycerine and cane sugar solution, and no alcohol,
the glycerine (25 lb.) is now stirred into the fats together with the requisite
(83 lb.) caustic soda solution 72° Tw. (38° B.). If it is intended to use
alcohol and sugar, and no glycerine, the latter is replaced by 47 lb. of
alcohol, and added after the incorporation of the caustic soda lye.
The whole being thoroughly crutched, the pan is covered and saponification
allowed to proceed for one hour or one and a half hours. Should the
saponification for some reason be retarded, a little steam may be very
cautiously admitted to the jacket of the pan, the mass well crutched until the
reaction commences, and the whole allowed to rest the specified time.
Whilst saponification is proceeding, the "sugar solution" is prepared by
dissolving 50 lb. cane sugar in 50 lb. water, at 168° F. (76° C.), to which
may be added 5 lb. soda crystals, and any necessary colouring matter. The
water used for this solution should be as soft as possible, as hard water is
liable to produce opaque streaks of lime soap.
It is absolutely necessary before proceeding further to ensure that
saponification is complete. A greasy, soft feel and the presence of "strength"
(caustic) would denote incomplete saponification—this can only be
remedied by further heating and crutching. Deficiency of caustic alkali
should also be avoided, and, if more lye is required, great care must be
exercised in its addition.

Saponification being completed, the sugar solution is carefully and
gradually crutched into the soap; when the contents of the pan have become
a homogeneous and syrupy mass, the crutching is discontinued, and the pan
is covered for one hour. The heat of the soap in the pan should not exceed
170° F. (77° C.).
Having rested the necessary period, the soap will have a slight froth on the
surface, but will be clear underneath and appear dark. Samples may now be
withdrawn, cooled, and examined prior to framing. If the process has been
successfully performed the soap will be firm and transparent, of uniform
colour, and possess only a faintly alkaline taste.
If the sample be firm but opaque, more sugar solution is required; this
should be added very carefully whilst crutching, an excess being specially
guarded against. If the sample be soft, although transparent, and the alkaline
taste not too pronounced, the soap evidently contains an excess of water,
which may be remedied by the addition of a small quantity of soda ash; too
much soda ash (carbonates) must be avoided, lest it should produce
efflorescence.
Having examined the soap and found it to be correct, or having remedied its
defects, the soap in the pan is allowed to cool to 145° F. (63° C.) and
perfume added. The soap is now quickly filled into narrow frames and
allowed to cool rapidly.
The blocks of soap should not be stripped until quite cold throughout, and
they should be allowed to stand open for a while before slabbing. When
freshly cut into tablets, the soap may appear somewhat turbid, but the
brightness comes with the exposure it will receive prior to stamping and
wrapping.
Saponifying Mineral Oil.—This sounds somewhat incongruous, as mineral
oil is entirely unsaponifiable. Most of the suggestions for this purpose
consist of the incorporation of mineral oil, or mineral oil emulsified by aid
of Quillaia bark, with a cocoa-nut oil soap, and in all these instances the
hydrocarbon merely exists in suspension.
G. Reale (Fr. Pat. 321,510, 1902), however, proposes to heat mineral oil
together with spermaceti and strong alkali, and states that he transforms the

hydrocarbons into alcohols, and these, absorbing oxygen, become fatty
acids, which are converted into soap by means of the alkali.
In this connection may be quoted the interesting work of Zelinsky (Russ.
Phys. Chem. Ges. Zeits. Angew. Chem., 1903, 37). He obtained substances,
by acting with carbon dioxide upon magnesia compounds of chlorinated
fractions of petroleum, which when decomposed by dilute sulphuric acid,
yielded various organic acids. One of these acids on heating with glycerine
formed tri-octin, which had the properties of a fat.
Dr. Engler, in confirmation of the theory of the animal origin of some
petroleums, obtained what might be described as petroleum (for it contained
almost all the hydrocarbons present in the natural mineral oil) by distilling
animal fats and oils under pressure.
Electrical Production of Soap.—Attempts have been made to produce soap
electrically by Messrs. Nodon, Brettonneau and Shee (Eng. Pat. 22,129,
1897), and also by Messrs. Merry and Noble (Eng. Pat. 2,372, 1900).
In the former patent, a mixture of soda-lye and fat is agitated by electricity
at a temperature of 194°-212° F. (90°-100° C.), while in the latter caustic
alkali is electrolytically produced from brine, and deposited on wire-netting
in the presence of fat, which is thereby saponified.

CHAPTER VI.
TREATMENT OF SETTLED SOAP.

Cleansing—Crutching—Liquoring of Soaps—Filling—
Neutralising, Colouring and Perfuming—Disinfectant Soaps—
Framing—Slabbing—Barring—Open and Close Piling—Drying
—Stamping—Cooling.
Cleansing.—After completion of saponification, and allowing the contents
of the pan to settle into the various layers, as described in the preceding
chapter, the actual soap, forming the second layer, is now transferred to the
frames, this being generally termed "cleansing" the soap. The thin crust or
layer at the top of the pan is gently removed, and the soap may be either
ladled out and conveyed to the frames, or withdrawn by the aid of a pump
from above the nigre through a skimmer (Fig. 1), and pipe, attached by
means of a swivel joint (Fig. 2) (which allows the skimmer pipe to be raised
or lowered at will by means of a winch, Fig. 3), to a pipe fitted in the side of
the pan as fully shown in Fig. 4, or the removal may be performed by
gravitation through some mechanical device from the side of the copper.

Fig. 1.—Skimmer, with flange for
attachment to skimmer-pipe.
Every precaution is taken to avoid the presence of nigre in the soap being
cleansed.

Fig. 2.—Swivel-joint.
The temperature at which soap may be cleansed depends on the particular
grade—soaps requiring to be liquored should not be cleansed too hot or a
separation will take place, 150° F. (66° C.) may be taken as a suitable
temperature for this class of soap; in the case of firm soaps, such as milling
base, where cooling is liable to take place in the pan (and thus affect the
yield), the temperature may be 165°-170° F. (74°-77° C.). This latter class
of soap is generally run direct to the frames and crutched by hand, or, to
save manual labour, it may be run into a power-driven crutching pan
(neutralising material being added if necessary) and stirred a few times
before framing.

Fig. 3.—Winch.

Fig. 4.—Soap-boiling pan, showing
skimmer pipe, swivel and winch.

Fig. 5.—Hand crutch.

Fig. 6.—Mechanical crutcher.
Crutching.—This consists of stirring the hot soap in the frames by hand
crutches (Fig. 5) until the temperature is sufficiently lowered and the soap
begins to assume a "ropiness". Crutching may also be performed
mechanically. There are various types of mechanical crutchers, stationary
and travelling. They may be cylindrical pans, jacketed or otherwise, in the
centre of which is rotated an agitator, consisting of a vertical or horizontal

shaft carrying several blades (Fig. 6) or the agitator may take the form of an
Archimedean screw working in a cylinder (Fig. 7).

Fig. 7.—Mechanical crutcher.
The kind of soap to be crutched, whether thin or stiff, will determine the
most suitable type for the purpose. The former class includes "washer" soap
which is generally neutralised, and coloured and perfumed, if necessary, in
these crutching pans, and in that case they are merely used for mixing the
liquids with the hot soap prior to its passage along wooden spouts (Fig. 8)
provided with outlets over the frames, in which the crutching is continued
by hand. In the case of stiff soaps requiring complete incorporation of
liquor, the screw type is preferable, the soap being forced upwards by the
screw, and descending between the cylinder and the sides of the pan, while
the reverse action can also be brought into play. The completion of
crutching is indicated by the smoothness and stiffness of the soap when
moved with a trowel, and a portion taken out at this point and cooled should
present a rounded appearance. When well mixed the resultant product is
emptied directly into wheel-frames placed underneath the outlet of the pan.
It is important that the blades or worm of the agitating gear be covered with
soap to avoid the occlusion of air and to prevent the soap becoming soft and
spongy.

Fig. 8.—Wooden soap spout.
Liquoring of Soaps.—This consists of the addition of various alkaline
solutions to soap to produce different qualities, and is best performed in the
crutching machines, although it is in some instances carried out in the
frames. In the history of soap-making a large number and variety of
substances have been suggested for the purpose of accomplishing some real
or supposed desirable effect when added to soap. Many of these have had
only a very short existence, and others have gradually fallen out of use.
Amongst the more practical additions most frequently adopted may be
mentioned carbonate of soda, silicate of soda, and pearl ash (impure
carbonate of potash). The carbonate of soda may be used in the form of
"soda crystals," which, containing 62.9 per cent. of water, dissolves in its
own water of crystallisation on heating, and is in that manner added to the
hot soap. In the case of weak-bodied soap, this addition gives firmness and
tends to increase the detergent qualities.
The soda carbonate may also be added to soap as a solution of soda ash (58°
alkali) either concentrated, 62° Tw. (34° B.), or of various strengths from
25° Tw. (16° B.) upwards. This solution stiffens and hardens soap, and the
addition, which must not be excessive, or efflorescence will occur, is
generally made at a temperature of 140° F. (60° C.). Care should always be
taken in the choice of solutions for liquoring. Strong soda ash solution with
a firm soap will result in a brittle product, whereas the texture of a weak
soap would be greatly improved by such addition.
A slight addition of a weak solution of pearl ash, 4°-8° Tw. (2.7-5.4° B.),
improves the appearance of many soaps intended for household purposes.
For yellow soaps, containing a low percentage of fatty acids, solutions of
silicate of soda of varying strengths are generally used.
It is always advisable to have a test sample made with the soap to ascertain
what proportion and what strength of sodium silicate solution is best suited

for the grade of soap it is desired to produce. It is important that the soap to
be "silicated" should be distinctly alkaline (i.e., have a distinct caustic
taste), or the resultant soap is liable to become like stone with age. The
alkaline silicate of soda (140° Tw., 59.5° B.) is the quality most convenient
for yellow soaps; this may be diluted to the desired gravity by boiling with
water. For a reduction of 3-4 per cent. fatty acids content, a solution of 6°
Tw. (4° B.) (boiling) is most suitable, and if the reduction desired is greater,
the density of the silicate solution should be increased; for example, to
effect a reduction of 20 per cent. fatty acids content, a solution of 18° Tw.
(12° B.) (boiling) would probably be found to answer.
In some instances 140° Tw. (59.5° B.) silicate may be added; experiment
alone will demonstrate the amount which can be satisfactorily incorporated
without the soap becoming "open," but 1/10 of the quantity of soap taken is
practically a limit, and it will be found that the temperature should be low;
the same quantity of silicate at different temperatures does not produce the
same result. Various other strengths of sodium silicate are employed,
depending upon the composition and body of the soap base—neutral
silicate 75° Tw. (39.4° B.) also finds favour with some soap-makers.
Mixtures of soda crystals or soda ash solution with silicate of soda solution
are used for a certain grade of soap, which is crutched until smooth and
stiff. Glauber's salt (sodium sulphate) produces a good smooth surface when
added to soap, but, owing to its tendency to effloresce more quickly than
soda carbonate, it is not so much used as formerly.
Common salt sometimes forms an ingredient in liquoring mixtures.
Potassium chloride and potassium silicate find a limited use for intermixing
with soft soaps.
It will be readily understood that hard and fast rules cannot be laid down for
"liquoring" soap, and the correct solution to be employed can only be
ascertained by experiment and experience, but the above suggestions will
prove useful as a guide towards good results. A smooth, firm soap of clear,
bright, glossy appearance is what should be aimed at.
Filling.—Some low-grade soaps contain filling, which serves no useful
purpose beyond the addition of weight. Talc is the most frequently used
article of this description. It consists of hydrated silicate of magnesium and,

when finely ground, is white and greasy to the touch. The addition of this
substance to the hot soap is made by suspending it in silicate of soda
solution.
Whatever filling material is used, it is important that the appearance of the
soap should not be materially altered.
Neutralising, Colouring and Perfuming.—The free caustic alkali in soap,
intended for toilet or laundry purposes, is usually neutralised during the
cleansing, although some soap manufacturers prefer to accomplish this
during the milling operation. Various materials have been recommended for
the purpose, those in most general use being sodium bicarbonate, boric
acid, cocoa-nut oil, stearic acid, and oleic acid.
The best method is the addition of an exact quantity of sodium bicarbonate
(acid sodium carbonate), which converts the caustic alkali into carbonate.
The reaction may be expressed by the equation:—

NaOH + NaHCO3 = Na2>CO3 + H2O
Caustic soda Bicarbonate of soda Carbonate of soda Water

Boric acid in aqueous or glycerine solutions, and borax (biborate of soda)
are sometimes used, but care is necessary in employing these substances, as
any excess is liable to decompose the soap.
The addition of cocoa-nut oil is unsatisfactory, the great objection being
that complete saponification is difficult to ensure, and, further, there is
always the liability of rancidity developing. Stearic and oleic acids are more
suitable for the purpose, but oleic acid has the disadvantage that oleates are
very liable to go rancid.
A large number of other substances have been proposed, and in many
instances patented, for neutralising the free caustic alkali. Among these may
be mentioned—Alder Wright's method of using an ammoniacal salt, the
acid radicle of which neutralises the caustic alkali, ammonia being
liberated; the use of sodium and potassium bibasic phosphate (Eng. Pat.
25,357, 1899); a substance formed by treating albumen with formalin (Eng.
Pat., 8,582, 1900); wheat glutenin "albuminoses" (albumen after acid or
alkaline treatment); malt extract; and egg, milk, or vegetable albumen.

The colouring matter used may be of either vegetable or coal-tar origin, and
is dissolved in the most suitable medium (lye, water, or fat). The older types
of colouring matter—such as cadmium yellow, ochres, vermilion, umbers—
have been superseded.
In the production of washer household soaps, a small quantity of perfume is
sometimes added.
Disinfectant Soaps.—To the soap base, which must be strong to taste, is
added from 3 to 4 per cent. of coal-tar derivatives, such as carbolic acid,
cresylic acid, creosote, naphthalene, or compounds containing carbolic acid
and its homologues. The incorporation is made in the crutching pan, and
further crutching may be given by hand in the frames.
Framing.—The object of framing is to allow the soap to solidify into
blocks. The frames intended for mottled soaps, which require slow cooling,
are constructed of wood, often with a well in the base to allow excess of lye
to accumulate—for other soaps, iron frames are in general use. The frame
manufactured by H. D. Morgan of Liverpool is shown in Fig. 9.
As soon as the frame is filled, or as soon as the crutching in the frame is
finished, the soap is smoothed by means of a trowel, leaving in the centre a
heap which slopes towards the sides. Next day the top of the soap is
straightened or flattened with a wooden mallet, this treatment assisting in
the consolidation.

Fig. 9.—Soap frame.

Fig. 10.—Slabbing machine.
The length of time the soap should remain in frames is dependent on the
quality, quantity, and season or temperature, and varies usually from three
to seven days. When the requisite period has elapsed, the sides and ends of
the frames are removed, and there remains a solid block of soap weighing
from 10 to 15 cwt. according to the size of frame used. The blocks, after
scraping and trimming, are ready for cutting into slabs.

Slabbing.—This may be done mechanically by pushing the block of soap
through a framework containing pianoforte wires fixed at equi-distances
(Fig. 10, which shows a machine designed by E. Forshaw & Son, Ltd.), or
the soap may be out by hand by pulling a looped wire through the mass
horizontally along lines previously scribed, or, for a standard sized slab, the
wire may be a fixture in a box-like arrangement, which is passed along the
top of the soap, and the distance of the wire from the top of the box will be
the thickness of the slab (Fig. 11).

Fig. 11.—Banjo slabber.
All tallow soaps should be slabbed whilst still warm, cut into bars, and
open-piled immediately; if this type of soap is cold when slabbed its
appearance will be very much altered.
Barring.—The slabs are out transversely into bars by means of the looped
wire, or more usually by a machine (Fig. 12), the lower framework of
which, containing wires, is drawn through the soap placed on the base-
board; the framework is raised, and the bars fall upon the shelf, ready for
transference into piles. It has long been the custom in England to cut bars of
soap 15 inches long, and weighing 3 lb. each, or 37-1/2 bars of soap to the
cwt., but in recent years a demand has arisen for bars of so many various
weights that it must be sometimes a difficult matter to know what sizes to
stock.
In another type of barring machine, portions of the slab, previously cut to
size, are pushed against a framework carrying wires, and the bars slide
along a table ready for handling (Fig. 13).
In cutting machines, through which "washer" household soap is being
passed, the bar is pushed at right angles through another frame containing
wires, which divides it into tablets; these may be received upon racks and
are ready for drying and stamping. It is needless to say that the slabs and
tablets are cut with a view to reducing the amount of waste to the lowest

possible limit. Such a machine, made by E. Forshaw & Son, Ltd., is shown
in Fig. 14.

Fig. 12.—Barring machine.

Fig. 13.—Bar-cutting machine.

Fig. 14.—Tablet-cutting machine.
Open- and Close-piling.—As remarked previously, tallow soaps should be
cut whilst warm, and the bars "open-piled," or stacked across each other in

such a way that air has free access to each bar for a day. The bar of soap
will skin or case-harden, and next day may be "close-piled," or placed in the
storage bins, where they should remain for two or three weeks, when they
will be in perfect condition for packing into boxes ready for distribution.

Fig. 15.—Soap stamp.
Drying.—"Oil soaps," as soaps of the washer type are termed, do not skin
sufficiently by the open-piling treatment, and are generally exposed on
racks to a current of hot air in a drying chamber in order to produce the
skin, which prevents evaporation of water, and allows of an impression
being given by the stamp without the soap adhering to the dies. It is of
course understood that heavily liquored soaps are, as a rule, unsuitable for
the drying treatment, as the bars become unshapely, and lose water rapidly.
Stamping.—Bar soaps are usually stamped by means of a hand-stamp
containing removable or fixed brass letters (Fig. 15), with a certain brand or
designation of quality and the name of the manufacturer or vendor, and are
now ready for packing into boxes.
A very large bulk of the soap trade consists of the household quality in
tablet form, readily divided into two cakes. These are stamped in the
ordinary box moulds with two dies—top and bottom impressions—the die-
plates, being removable, allow the impressions to be changed. This type of
mould (Fig. 16) can be adjusted for the compression of tablets of varying

thickness, the box preventing the escape of soap. We are indebted to E.
Forshaw & Son, Ltd., for this illustration.

Fig. 16.—Box mould.
The stamping machine may be worked by hand (Fig. 17) or power driven.
Where large quantities of a particular tablet have to be stamped, one of the
many automatic mechanical stampers in existence may be employed, the
tablets being conveyed to and from the dies by means of endless belts. Such
a machine is shown in the accompanying illustration (Fig. 18).
If necessary, the soap is transferred to racks and exposed to the air, after
which it is ready for wrapping, which is generally performed by manual
labour, although in some instances automatic wrapping machines are in use.
Cardboard cartons are also used for encasing the wrapped tablets, the object
being that these are more conveniently handled by tradesmen and may be
advantageously used to form an attractive window display.
Cooling.—Many attempts have been made to shorten the time required for
the framing and finishing of soap, by cooling the liquid soap as it leaves the
pan.

Fig. 17.—Soap-stamping
machine, showing box mould.
With milling base, this is successfully accomplished in the Cressonnières'
plant, by allowing the hot soap to fall upon the periphery of a revolving
drum which can be cooled internally by means of water.

Fig. 18.—Automatic stamper.
In the case of household soaps, where the resultant product must be of good
appearance and have a firm texture, the difficulty is to produce a bar fit for
sale after the cooling has been performed, as soap which has been suddenly
chilled lacks the appearance of that treated in the ordinary way. Several
patents have been granted for various methods of moulding into bars in
tubes, where the hot soap is cooled by being either surrounded by running
water in a machine of similar construction to a candle machine, or rotated
through a cooling medium; and numerous claims have been made both for
mechanical appliances and for methods of removing or discharging the bars
after cooling. In many instances these have proved unsatisfactory, owing to
fracture of the crystalline structure. Moreover, in passing through some of
the devices for solidification after chilling, the soap is churned by means of
a worm or screw, and this interferes with the firmness of the finished bar,
for, as is well known, soap which has been handled too much, does not
regain its former firmness, and its appearance is rendered unsatisfactory.
A form of apparatus which is now giving satisfactory results is the
Leimdoerfer continuous cooler (Fig. 19). This consists of a fixed charging
hopper, A, a portable tank, B, containing tubes, and a detachable box, C,
which can be raised or lowered by means of a screw, D. The bottom of the
hopper is fitted with holes corresponding with the cooling tubes, e, and

closed by plugs c, attached to a frame b, which terminates above in a screw
spindle a, by means of which the frame and plugs can be raised and lowered
so as to permit or stop the outflow of soap into the cooling tubes. The tubes
are closed at the bottom by slides d, and the box B, in which they are
mounted, is carried on a truck running on rails. The charging hopper can be
connected with the soap-pan by a pipe, and when the hopper is filled with
liquid soap the plugs c are raised and the air in the box C exhausted, thus
causing the soap to descend into the cooling tubes.

Fig. 19.—Leimdoerfer cooler.
The slides d are closed, the screw D released, and the box B moved away to
make room for another. At the end of the rail track is an ejecting device
which pushes the cooled soap out of the tubes, and the truck is run back on
a side track to the machine for use over again. In this way the apparatus can
be worked continuously, the soap being received from the cooling pipes on
a suitable arrangement for transport to the press or store room.

A similar idea has been made the subject of a patent by Holoubek (Eng. Pat.
24,440, 1904, Fig. 20). The soap is run into frames or moulds having open
sides, which are closed by being clamped with screws and pressure plates
between cooling tubes through which water circulates.

Fig. 20.—Holoubek's cooler.

CHAPTER VII.
TOILET, TEXTILE AND MISCELLANEOUS SOAPS.

Toilet Soaps—Cold Process Soaps—Settled Boiled Soaps—
Remelted Soaps—Milled Soaps—Drying—Milling and
Incorporating Colour, Perfume, or Medicament—Perfume—
Colouring Matter—Neutralising and Superfatting Material—
Compressing—Cutting—Stamping—Medicated Soaps—Ether
Soap—Floating Soaps—Shaving Soaps—Textile Soaps—Soaps
for Woollen, Cotton and Silk Industries—Patent Textile Soaps—
Miscellaneous Soaps.
Toilet Soaps.—By the term "toilet soap" is inferred a soap specially adapted
for toilet use by reason not only of its good detergent and lathering
qualities, but also on account of its freedom from caustic alkali and any
other ingredient likely to cause irritation or injury to the skin.
Toilet soaps may be simply classified according to their method of
preparation into the following four classes:—
(1) Cold process soaps.
(2) Settled boiled soaps.
(3) Remelted soaps.
(4) Milled soaps.
Soaps of the first class are of comparatively trifling importance, having
been superseded by the other qualities. Details of the "cold process" have
already been given on page 46; it is only necessary to add the desired
perfume and colouring matter to the soap.
The second class consists of good quality settled soaps, direct from the
copper, to which have been added, prior to framing, suitable perfume and
colouring matter, also, if necessary, dealkalising materials.

The third class is represented by soaps made by the old English method of
remelting, which are often termed "perfumers'," or "little pan" soaps. The
soap-base or mixture of various kinds of soap is remelted in a steam-
jacketed pan, or pan provided with steam coils, and agitated. The agitation
must not be too vigorous or lengthy, or the soap will become aerated. When
all the soap is molten, additions of pearl ash solution are made to give it a
finer and smoother texture, render it more transparent, and increase its
lathering properties. The necessary colour, in a soluble form, is well
incorporated, and lastly the perfume. Owing to volatilisation, much of the
perfume is lost when added to hot soap, and it is necessary to add a large
quantity to get the desired odour; hence the cheaper essential oils have to be
used, so that the perfume of this class of soap is not so delicate as that of
milled soaps, although it is quite possible to produce remelted soaps as free
from uncombined alkali as a milled toilet soap.
Palm-oil soap often forms the basis for yellow and brown toilet soaps of
this class. The old-fashioned Brown Windsor soap was originally a curd
soap that with age and frequent remelting had acquired a brown tint by
oxidation of the fatty acids—the oftener remelted the better the resultant
soap.
Medicaments are sometimes added to these soaps, e.g., camphor, borax,
coal-tar, or carbolic. Oatmeal and bran have been recommended in
combination with soap for toilet purposes, and a patent (Eng. Pat. 26,396,
1896) has been granted for the use of these substances together with wood-
fibre impregnated with boric acid.
After cooling in small frames, the soap is slabbed, and cut into blocks, and
finally into portions suitable for stamping in a press (hand or steam driven)
with a design or lettering on each side.
Milled Toilet Soaps.—Practically all high-class soaps now on the market
pass through the French or milling process. This treatment, as its name
implies, was first practised by the French who introduced it to this country,
and consists briefly of (i.) drying, (ii.) milling and incorporating colour,
perfume or medicament, (iii.) compressing, and (iv.) cutting and stamping.
The advantages of milled soap over toilet soap produced by other methods
are that the former, containing less water and more actual soap, is more

economical in use, possesses a better appearance, and more elegant finish,
does not shrink or lose its shape, is more uniform in composition, and
essential oils and delicate perfumes may be incorporated without fear of
loss or deterioration.
Only soap made from best quality fats is usually milled, a suitable base
being that obtained by saponifying a blend of the finest white tallow with a
proportion, not exceeding 25 per cent., of cocoa-nut oil, and prepared as
described in Chapter V.
The first essential of a milling base is that the saponification should be
thorough and complete; if this is not ensured, rancidity is liable to occur and
a satisfactory toilet soap cannot be produced. The soap must not be short in
texture or brittle and liable to split, but of a firm and somewhat plastic
consistency.
(i.) Drying.—The milling-base, after solidification in the frames, contains
almost invariably from 28 to 30 per cent. of water, and this quantity must be
reduced to rather less than half before the soap can be satisfactorily milled.
Cutting the soap into bars or strips and open piling greatly facilitates the
drying, which is usually effected by chipping the soap and exposing it on
trays to a current of hot air at 95-105° F. (35-40° C.).
There are several forms of drying chambers in which the trays of chips are
placed upon a series of racks one above another, and warm air circulated
through, and Fig. 21 shows a soap drying apparatus with fan made by W. J.
Fraser & Co., Ltd., London.
The older method of heating the air by allowing it to pass over a pipe or
flue through which the products of combustion from a coke or coal fire are
proceeding under the floor of the drying chamber to a small shaft, has been
superseded by steam heat. The air is either drawn or forced by means of
quickly revolving fans through a cylinder placed in a horizontal position
and containing steam coils, or passed over steam-pipes laid under the iron
grating forming the floor of the chamber.

Fig. 21.—Soap-drying apparatus.
It will be readily understood that in the case of a bad conductor of heat, like
soap-chippings, it is difficult to evaporate moisture without constantly
moving them and exposing fresh surfaces to the action of heat.
In the Cressonnières' system, where the shavings of chilled soap are dried
by being carried through a heated chamber upon a series of endless bands
(the first discharging the contents on to a lower belt which projects at the
end, and is moving in the opposite direction, and so on), this is performed
by intercepting milling rollers in the system of belts (Eng. Pat. 4,916, 1898)
whereby the surfaces exposed to the drying are altered, and it is claimed
that the formation of hardened crust is prevented.
In the ordinary methods of drying, the chips are frequently moved by hand
to assist uniform evaporation.
The degree of saturation of the air with moisture must be taken into
consideration in regulating the temperature and flow of air through the
drying chamber, and for this purpose the use of a hygrometer is
advantageous.
It is very important that the correct amount of moisture should be left in the
soap, not too much, nor too little; the exact point can only be determined by
judgment and experience, and depends to a considerable extent upon the
nature of the soap, and also on the amount of perfume or medicament to be
added, but speaking generally, a range of 11 to 14 per cent. gives good
results. If the soap contains less than this amount it is liable to crumble

during the milling, will not compress satisfactorily, and the finished tablet
may have a tendency to crack and contain gritty particles so objectionable
in use. If, on the other hand, the soap is left too moist, it is apt to stick to the
rollers and mill with difficulty, and during compression the surface assumes
a blistered and sticky appearance.
(ii.) Milling and Incorporation of Colour, Perfume or Medicament.—The
object of milling is to render the soap perfectly homogeneous, and to reduce
it to a state in which colour, perfume, or any necessary neutralising material
or other substance may be thoroughly incorporated. The milling machine
consists of smooth granite rollers, fitted with suitable gearing and working
in an iron framework (Fig. 22). The rollers are connected in such a manner
that they rotate at different speeds, and this increases the efficiency of the
milling, and ensures that the action of the rollers is one of rubbing rather
than crushing.
By means of suitably arranged screws the pressure of the rollers on one
another can be adjusted to give the issuing soap any desired thickness; care
should be taken that the sheets of soap are not unnecessarily thick or the
colour and odour will not be uniform.
The soap, in the form of chips, is introduced on to the rollers through a
hopper, and after one passage through the mill, from bottom to top, one of
the serrated knife edges is applied and the ribbons of the soap are delivered
into the top of the hopper where the colour, perfume, and any other desired
admixture is added, and the milling operation repeated three or four times.
When the incorporation is complete the other scraper is fixed against the
top roller and the soap ribbon passed into the receptacle from which it is
conveyed to the compressor. A better plan, however, especially in the case
of the best grade soaps, where the perfumes added are necessarily more
delicate and costly, is to make the addition of the perfume when the colour
has been thoroughly mixed throughout the mass. Another method is to mill
once and transfer the mass to a rotary mixing machine, fitted with internal
blades, of a peculiar form, which revolve in opposite directions one within
the other as the mixer is rotated. The perfume, colouring matter, etc., are
added and the mixer closed and set in motion, when, after a short time, the
soap is reduced to a fine granular condition, with the colour and perfume
evenly distributed throughout the whole. By the use of such machines, the

loss of perfume by evaporation, which during milling is quite appreciable,
is reduced to a minimum, and the delicacy of the aroma is preserved
unimpaired.

Fig. 22.—Milling machine.
Prolonged milling, especially with a suitable soap base, tends to produce a
semi-transparent appearance, which is admired by some, but the increased
cost of production by the repeated milling is not accompanied by any real
improvement in the soap.
Perfume.—The materials used in perfuming soap will be dealt with fully in
the next chapter. The quantity necessary to be added varies considerably
with the nature of the essential oils, and also the price at which the soap is
intended to be sold. In the cheaper grades of milled soaps the quantity will
range from 10-30 fluid ozs. per cwt., and but rarely exceeds 18-20 ozs.,
whereas in more costly soaps as much as 40-50 fluid ozs. are sometimes
added to the cwt.
Colouring Matter.—During recent years an outcry has been made against
highly coloured soaps, and the highest class soaps have been manufactured
either colourless or at the most with only a very delicate tint. It is obvious
that a white soap guarantees the use of only the highest grade oils and fats,
and excludes the introduction of any rosin, and, so far, the desire for a white
soap is doubtless justified. Many perfumes, however, tend to quickly
discolour a soap, hence the advantage of giving it a slight tint. For this

purpose a vegetable colouring matter is preferable, and chlorophyll is very
suitable.

Fig. 23.—Compressor.
A demand still exists for brightly coloured soaps, and this is usually met by
the use of coal-tar dyes. The quantity required is of course extremely small,
so that no harm or disagreeable result could possibly arise from their use.
Neutralising and Superfatting Material.—If desired, the final neutralisation
of free alkali can be carried out during the milling process, any superfatting
material being added at the same time. The chief neutralising reagents have
already been mentioned in Chapter VI.
With regard to superfatting material, the quantity of this should be very
small, not exceeding 6-8 ozs. per cwt: The most suitable materials are
vaseline, lanoline, or spermaceti.

Fig. 24—Hand soap-stamping
press.
(iii.) Compressing.—The next stage is the compression and binding of the
soap ribbons into a solid bar suitable for stamping, and the plant used (Fig.
23) for this purpose is substantially the same in all factories. The soap is fed
through a hopper into a strong metal conical-shaped tube like a cannon,
which tapers towards the nozzle, and in which a single or twin screw is
moving, and the soap is thereby forced through a perforated metallic disc,
subjected to great pressure, and compressed. The screws must be kept
uniformly covered with shavings during compression to obviate air bubbles
in the soap.

Fig. 25.—Screw press.
The soap finally emerges through the nozzle (to which is attached a cutter
of suitable shape and size according to the form it is intended the final
tablet to take) as a long, polished, solid bar, which is cut with a knife or
wire into lengths of 2 or 3 feet, and if of satisfactory appearance, is ready
for cutting and stamping. The nozzle of the plodder is heated by means of a
Bunsen burner to about 120° or 130° F. (49°-55° C.) to allow the soap to be
easily forced out, and this also imparts a good gloss and finish to the ejected
bar—if the nozzle is too hot, however, the soap will be blistered, whereas
insufficient heat will result in streaky soap of a poor and dull appearance.
(iv.) Cutting and Stamping.—In cutting the soap into sections for stamping,
the cutter should shape it somewhat similar to the required finished tablet.
Many manufacturers cut the soap into sections having concave ends, and in
stamping, the corners are forced into the concavity, with the result that
unsightly markings are produced at each end of the tablet. It is preferable to
have a cutter with convex ends, and if the stamping is to be done in a pin
mould the shape should be a trifle larger than the exact size of the desired
tablet.

Fig. 26—Pin mould.
The stamping may be performed by a hand stamper (Fig. 24), a screw press
(Fig. 25), or by a steam stamper. The screw press works very satisfactorily
for toilet soaps.
There are two kinds of moulds in use for milled soaps:—
(a) Pin Moulds in which tablets of one size and shape only can be produced
(Fig. 25). The edges of the mould meet very exactly, the upper part of the
die carries two pins attached to the shoulder, and these are received into two
holes in the shoulder of the bottom plate. The superfluous soap is forced out
as the dies meet.
(b) Band or Collar Moulds.—In this form (Fig, 27) the mould may be
adjusted to stamp various sized tablets, say from 2 ozs. to 5-1/3 ozs. and
different impressions given by means of removable die plates. The band or
collar prevents the soap squeezing out sideways. We are indebted to R.
Forehaw & Son, Ltd., for the loan of this illustration.
It is usual to moisten the soap or mould with a dilute solution of glycerine if
it should have a tendency to stick to the die plates.
The soap is then ready for final trimming, wrapping, and boxing.

Fig. 27—Band Mould.

Medicated Soaps.

The inherent cleansing power of soap renders it invaluable in combating
disease, while it also has distinct germicidal properties, a 2 per cent.
solution proving fatal to B. coli communis in less than six hours, and even a
1 per cent. solution having a marked action on germs in fifteen minutes.
Many makers, however, seek more or less successfully to still further
increase the value of soap in this direction by the incorporation of various
drugs and chemicals; and the number of medicated soaps on the market is
now very large. Such soaps may consist of either hard or soft soaps to
which certain medicaments have been added, and can be roughly divided
into two classes, (a) those which contain a specific for various definite
diseases, the intention being that the remedy should be absorbed by the
pores of the skin and thus penetrate the system, and (b) those impregnated
with chemicals intended to act as antiseptics or germicides, or, generally, as
disinfectants.
The preparation of medicinal soaps appears to have been first taken up in a
scientific manner by Unna of Hamburg in 1886, who advocated the use of
soap in preference to plasters as a vehicle for the application of certain
remedies.
Theoretically, he considered a soap-stock made entirely from beef tallow
the most suitable for the purpose, but in practice found that the best results
were obtained by using a superfatted soap made from a blend of one part of
olive oil with eight parts of beef tallow, saponified with a mixture of two

parts of soda to one part of potash, sufficient fat being employed to leave an
excess of 3 or 4 per cent. unsaponified. Recent researches have shown,
however, that even if a superfatted soap-base is beneficial for the
preparation of toilet soaps (a point which is open to doubt), it is quite
inadmissible for the manufacture of germicidal and disinfectant soaps, the
bactericidal efficiency of which is much restricted by the presence of free
fat.
Many of the medicaments added to soaps require special methods of
incorporation therein, as they otherwise react with the soap and decompose
it, forming comparatively inert compounds. This applies particularly to salts
of mercury, such as corrosive sublimate or mercuric chloride, and biniodide
of mercury, both of which have very considerable germicidal power, and are
consequently frequently added to soaps. If simply mixed with the soap in
the mill, reaction very quickly takes place between the mercury salt and the
soap, with formation of the insoluble mercury compounds of the fatty acids,
a change which can be readily seen to occur in such a soap by the rapid
development on keeping, of a dull slaty-green appearance. Numerous
processes have been suggested, and in some cases patented, to overcome
this difficulty. In the case of corrosive sublimate, Geissler suggested that the
soap to which this reagent is to be added should contain an excess of fatty
acids, and would thereby be rendered stable. This salt has also been
incorporated with milled soap in a dry state in conjunction with ammonio-
mercuric chloride, β-naphthol, methyl salicylate, and eucalyptol. It is
claimed that these bodies are present in an unchanged condition, and
become active when the soap is added to water as in washing. Ehrhardt
(Eng. Pat. 2,407, 1898) patented a method of making antiseptic mercury
soap by using mercury albuminate—a combination of mercuric chloride
and casein, which is soluble in alkali, and added to the soap in an alkaline
solution.
With biniodide of mercury the interaction can be readily obviated by adding
to the biniodide of mercury an equal weight of potassium iodide. This
process, devised and patented by J. Thomson in 1886, has been worked
since that time with extremely satisfactory results. Strengths of 1/2, 1, and 3
per cent. biniodide are sold, but owing to the readiness with which it is
absorbed by the skin a soap containing more than 1/2 per cent. should only
be used under medical advice.

A similar combination of bromide of mercury with potassium, sodium, or
ammonium bromide has recently been patented by Cooke for admixture
with liquid, hard, or soft soaps.
Zinc and other Metallic Salts.—At various times salts of metals other than
mercury have been added to soap, but, owing to their insolubility in water,
their efficiency as medicaments is very trifling or nil. Compounds have
been formed of metallic oxides and other salts with oleic said, and mixtures
made with vaseline and lanoline, and incorporated with soap, but they have
not met with much success.
Another chemical commonly added to soap is Borax. In view of its alkaline
reaction to litmus, turning red litmus blue, this salt is no doubt generally
regarded as alkaline, and, as such, without action on soap. On the contrary,
however, it is an acid salt containing an excess of boric acid over the soda
present, hence when it is added to soap, fatty acids are necessarily liberated,
causing the soap to quickly become rancid. As a remedy for this it has been
proposed to add sufficient alkali to convert the borax into neutral mono-
borate of soda which is then added to the soap. This process is patented and
the name "Kastilis" has been given to the neutral salt. The incorporation of
borax with the addition of gum tragasol forms the subject of two patents
(Eng. Pats. 4,415, 1904; and 25,425, 1905); increased detergent and lasting
properties are claimed for the soap. Another patented process (Eng. Pat.
17,218, 1904) consists of coating the borax with a protective layer of fat or
wax before adding to the soap with the idea that reaction will not take place
until required. Boric acid possesses the defects of borax in a greater degree,
and would, of course, simply form sodium borate with liberation of fatty
acids, so should never be added to a neutral soap.
Salicylic Acid is often recommended for certain skin diseases, and here
again the addition of the acid to soap under ordinary conditions results in
the formation of sodium salicylate and free fatty acids.
To overcome this a process has recently been patented for rubbing the acid
up with vaseline before addition to soap, but the simplest way appears to be
to add the soda salt of the acid to soap.
Amongst the more common milled medicated toilet soaps may be
mentioned, in addition to the above:—

Birch Tar Soap, containing 5 or 10 per cent. birch tar, which has a
characteristic pungent odour and is recommended as a remedy for eczema
and psoriasis.
Carbolic Soap.—A toilet soap should not contain more than 3 per cent. of
pure phenol, for with larger quantities irritation is likely to be experienced
by susceptible skins.
Coal Tar.—These soaps contain, in addition to carbolic acid and its
homologues, naphthalene and other hydrocarbons derived from coal,
naphthol, bases, etc. Various blends of different fractions of coal tar are
used, but the most valuable constituents from a disinfectant point of view
are undoubtedly the phenols, or tar acids, though in this case as with
carbolic and cresylic soaps, the amount of phenols should not exceed 3 per
cent. in a toilet soap. An excess of naphthalene should also be avoided,
since, on account of its strong odour, soaps containing much of it are
unpopular. The odour of coal tar is considerably modified by and blends
well with a perfume containing oils of cassia, lavender, spike, and red
thyme.
Formaldehyde.—This substance is one of the most powerful disinfectants
known, and it may be readily introduced into soap without undergoing any
decomposition, by milling in 2-3 per cent. of formalin, a 40 per cent.
aqueous solution of formaldehyde, which is a gas. White soaps containing
this chemical retain their whiteness almost indefinitely.
New combinations of formaldehyde with other bodies are constantly being
brought forward as disinfectants. Among others the compound resulting
from heating lanoline with formaldehyde has been patented (Eng. Pat.
7,169, 1898), and is recommended as an antiseptic medicament for
incorporation with soap.
Glycerine.—Nearly all soaps contain a small quantity of this body which is
not separated in the lyes. In some cases, however, a much larger quantity is
desired, up to some 6 or 8 per cent. To mill this in requires great care,
otherwise the soap tends to blister during compression. The best way is to
dry the soap somewhat further than usual, till it contains say only 9 or 10
per cent. moisture and then mill in the glycerine.

Ichthyol or Ammonium-Ichthyol-Sulphonate is prepared by treating with
sulphuric acid, and afterwards with ammonia, the hydrocarbon oil
containing sulphur obtained by the dry distillation of the fossil remains of
fish and sea-animals, which form a bituminous mineral deposit in Germany.
This product has been admixed with soap for many years, the quantity
generally used being about 5 per cent.; the resultant soap is possessed of a
characteristic empyreumatic smell, very dark colour, and is recommended
for rosacea and various skin diseases, and also as an anti-rheumatic.
Ichthyol has somewhat changed its character during recent years, being now
almost completely soluble in water, and stronger in odour than formerly.
Iodine.—A soap containing iodine is sometimes used in scrofulous skin
diseases. It should contain some 3 per cent. iodine, while potassium iodide
should also be added to render the iodine soluble.
Lysol.—This name is applied to a soap solution of cresol, "Lysol Soap"
being simply another form of coal-tar soap. The usual strength is 10 per
cent. lysol, and constitutes a patented article (Fr. Pat. 359,061, 1905).
Naphthol.—β-Naphthol, also a coal-tar derivative, is a good germicide, and,
incorporated in soap to the extent of 3 per cent. together with sulphur, is
recommended for scabies, eczema and many other cutaneous affections.
Sulphur.—Since sulphur is insoluble in water, its action when used in
conjunction with soap can be but very slow and slight. Sulphur soaps are,
however, very commonly sold, and 10 per cent. is the strength usually
advocated, though many so-called sulphur soaps actually contain very little
sulphur. They are said to be efficacious for acne and rosacea.
Sulphur soaps, when dissolved in water, gradually generate sulphuretted
hydrogen, which, although characteristic, makes their use disagreeable and
lessens their popular estimation.
Terebene.—The addition of this substance to soap, though imparting a very
refreshing and pleasant odour, does not materially increase the disinfectant
value of the soap. A suitable strength is 5 per cent.
Thymol.—This furnishes a not unpleasant, and very useful antiseptic soap,
recommended especially for the cleansing of ulcerated wounds and
restoring the skin to a healthy state. The normal strength is 3 per cent. It is

preferable to replace part of the thymol with red thyme oil, the thymene of
which imparts a sweeter odour to the soap than if produced with thymol
alone. A suitable blend is 2-1/2 per cent. of thymol crystals and 1-1/2 per
cent. of a good red thyme oil.
Of the vast number of less known proposed additions to toilet soaps,
mention may be made in passing of:—
Fluorides.—These have been somewhat popular during recent years for the
disinfection of breweries, etc., and also used to some extent as food
preservatives. Of course only neutral fluorides are available for use in soap,
acid fluorides and soap being obviously incompatible. In the authors'
experience, however, sodium fluoride appears to have little value as a
germicide when added to soap, such soaps being found to rapidly become
rancid and change colour.
Albumen.—The use of albumen—egg, milk, and vegetable—in soap has
been persistently advocated in this country during the past few years. The
claims attributed to albumen are, that it neutralises free alkali, causes the
soap to yield a more copious lather, and helps to bind it more closely, and a
further inducement held out is that it allows more water to be left in the
soap without affecting its firmness. Experiments made by the authors did
not appear to justify any enthusiasm on the subject, and the use of albumen
for soap-making in this country appears to be very slight, however popular
it may be on the Continent. Numerous other substances have been proposed
for addition to soaps, including yeast, tar from peat (sphagnol), Swedish
wood tar, permanganate of potash, perborates and percarbonates of soda
and ammonia, chlorine compounds, but none of these has at present come
much into favour, and some had only ephemeral existence. Of the many
drugs that it has been suggested to admix in soap for use in allaying an
irritable condition of the skin, the majority are obviously better applied in
the form of ointments, and we need not consider them further.
Ether Soap.—Another form of medicated soap made by a few firms is a
liquid ether soap containing mercuric iodide, and intended for surgeons'
use. This, as a rule, consists of a soap made from olive oil and potash,
dissolved in alcohol and mixed with ether, the mercuric iodide being

dissolved in a few drops of water containing an equal weight of potassium
iodide, and this solution added to the alcohol-ether soap.
Floating Soaps.—Attempts have been made to produce tablets of soap that
will float upon the surface of water, by inserting cork, or floats, or a
metallic plate in such a manner that there is an air space between the metal
and the soap. The more usual method is to incorporate into hot soap
sufficient air, by means of a specially designed self-contained jacketed
crutcher, in which two shafts carrying small blades or paddles rotate in
opposite directions, to reduce the density of the soap below that of water
and so enable the compressed tablet to float. The difference in weight of a
tablet of the same size before and after aerating amounts to 10 per cent.
Ordinary milling soap is used as a basis for this soap; the settled soap direct
from the copper at 170° F. (77° C.) is carefully neutralised with bicarbonate
of sodium, oleic or stearic acids, or boro-glyceride, perfumed and aerated.
Floating soap, which is usually white (some are of a cream tint), cannot be
recommended as economical, whilst its deficiency in lathering properties,
owing to occluded air, is a serious drawback to its popularity as a toilet
detergent.
Shaving Soaps.—The first essential of a shaving soap, apart from its
freedom from caustic alkali or any substance exerting an irritating effect
upon the skin, is the quick production of a profuse creamy lather which is
lasting. Gum tragacanth is used in some cases to give lasting power or
durability, but is not necessary, as this property is readily attained by the use
of a suitable proportion of potash soap. The best shaving soaps are mixtures
of various proportions of neutral soda and potash soaps, produced by the
combination of ordinary milling base with a white potash soap, either
melted or milled together. Glycerine is sometimes added, and is more
satisfactorily milled in.
Every precaution should be taken to ensure thorough saponification of the
soaps intended for blending in shaving soap, otherwise there will be a
tendency to become discoloured and develop rancidity with age. Shaving
soaps are delicately perfumed, and are placed on the market either in the
form of sticks which are cut from the bar of soap as it leaves the
compressor, or stamped in flat cakes.

Shaving creams and pastes are of the same nature as shaving soaps, but
usually contain a larger proportion of superfatting material and considerably
more water.

Textile Soaps.

In the woollen, cloth, and silk textile industries, the use of soap for
detergent and emulsifying purposes is necessary in several of the processes,
and the following is a brief description of the kinds of soap successfully
employed in the various stages.
1. Woollen Industry.—The scouring of wool is the most important operation
—it is the first treatment raw wool is subjected to, and if it is not performed
in an efficient manner, gives rise to serious subsequent troubles to
manufacturer, dyer, and finisher.
The object of scouring wool is to remove the wool-fat and wool
perspiration (exuded from the skin of sheep), consisting of cholesterol and
isocholesterol, and potassium salts of fatty acids, together with other salts,
such as sulphates, chlorides, and phosphates. This is effected by washing in
a warm dilute soap solution, containing in the case of low quality wool, a
little carbonate of soda; the fatty matter is thereby emulsified and easily
removed.
Soap, to be suitable for the purpose, must be free from uncombined caustic
alkali, unsaponified fat, silicates, and rosin.
Wool can be dissolved in a moderately dilute solution of caustic soda, and
the presence of this latter in soap, even in small quantities, is therefore
liable to injure the fibres and make the resultant fabric possess a harsh
"feel," and be devoid of lustre.
Unsaponified fat denotes badly made soap—besides reducing the
emulsifying power of the liberated alkali, this fat may be absorbed by the
fibres and not only induce rancidity but also cause trouble in dyeing.
Soaps containing silicates may have a deleterious action upon the fibres,
causing them to become damaged and broken.

By general consent soaps containing rosin are unsuitable for use by woollen
manufacturers, as they produce sticky insoluble lime and magnesia
compounds which are deposited upon the fibres, and give rise to
unevenness in the dyeing.
A neutral olive-oil soft soap is undoubtedly the best for the purpose of wool
scouring, as, owing to its ready solubility in water, it quickly penetrates the
fibres, is easily washed out, and produces a good "feel" so essential in the
best goods, and tends to preserve the lustre and pliability of the fibre.
The high price of olive-oil soap, however, renders its use prohibitive for
lower class goods, and in such cases no better soap can be suggested than
the old-fashioned curd mottled or curd soaps (boiled very dry), as free as
possible from uncombined caustic alkali. The raw wool, after this cleansing
operation, is oiled with olive oil or oleine, prior to spinning; after spinning
and weaving, the fabric, in the form of yarn or cloth, has to be scoured to
free it from oil. The soap in most general use for scouring woollen fabrics is
neutral oleine-soda soap. Some manufacturers prefer a cheap curd soap,
such as is generally termed "second curd," and in cases where lower grades
of wools are handled, the user is often willing to have soap containing rosin
(owing to its cheapness) and considers a little alkalinity desirable to assist
in removing the oil.
Another operation in which soap is used, is that of milling or fulling,
whereby the fabric is made to shrink and thus becomes more compact and
closer in texture. The fabric is thoroughly cleansed, for which purpose the
soap should be neutral and free from rosin and silicates, otherwise a harsh
feeling or stickiness will be produced. Curd soaps or finely-fitted soaps
made from tallow or bleached palm oil, with or without the addition of
cocoa-nut oil, give the best results. All traces of soap must be carefully
removed if the fabric is to be dyed.
The woollen dyer uses soap on the dyed pieces to assist the milling, and
finds that a good soap, made from either olive oil, bleached palm oil, or
tallow, is preferable, and, although it is generally specified to be free from
alkali, a little alkalinity is not of consequence, for the woollen goods are, as
a rule, acid after dyeing, and this alkalinity would be instantly neutralised.

2. Cotton Industry.—Cotton fibres are unacted upon by caustic alkali, so
that the soap used in cleaning and preparing cotton goods for dyeing need
not be neutral, in fact alkalinity is a distinct advantage in order to assist the
cleansing.
Any curd soap made from tallow, with or without the addition of a small
quantity of cocoa-nut oil, may be advantageously used for removing the
natural oil.
In cotton dyeing, additions of soap are often made to the bath, and in such
cases the soap must be of good odour and neutral, lest the colours should be
acted upon and tints altered. Soaps made from olive oil and palm oil are
recommended. The same kind of soap is sometimes used for soaping the
dyed cotton goods.
The calico-printer uses considerable quantities of soap for cleansing the
printed-cloths. The soap not only cleanses by helping to remove the gummy
and starchy constituents of the adhering printing paste, but also plays an
important part in fixing and brightening the colours. Soaps intended for this
class of work must be quite neutral (to obviate any possible alteration in
colour by the action of free alkali), free from objectionable odour and rosin,
and readily soluble in water. These qualities are possessed by olive-oil
soaps, either soft or hard. A neutral olive-oil soft soap, owing to its
solubility in cold water, may be used for fibres coloured with most delicate
dyes, which would be fugitive in hot soap solutions, and this soap is
employed for the most expensive work.
Olive-oil curd (soda) soaps are in general use; those made from palm oil are
also recommended, although they are not so soluble as the olive-oil soaps.
Tallow curd soaps are sometimes used, but the difficulty with which they
dissolve is a drawback, and renders them somewhat unsuitable.
3. Silk Industry.—Silk is secured to remove the sericin or silk-glue and
adhering matter from the raw silk, producing thereby lustre on the softened
fibre and thus preparing it for the dyer.
The very best soap for the purpose is an olive-oil soft soap; olive-oil and
oleine hard soaps may also be used. The soap is often used in conjunction
with carbonate of soda to assist the removal of the sericin, but, whilst

carbonates are permissible, it is necessary to avoid an excess of caustic
soda.
Tallow soaps are so slowly soluble that they are not applicable to the
scouring of silk.
The dyer of silk requires soap, which is neutral and of a pleasant odour. The
preference is given to neutral olive-oil soft soap, but hard soaps (made from
olive oil, oleine, or palm oil) are used chiefly on account of cheapness. It is
essential, however, that the soap should be free from rosin on account of its
frequent use and consequent decomposition in the acid dye bath, when any
liberated rosin acids would cling to the silk fibres and produce disagreeable
results.
Patent Textile Soaps.—Stockhausen (Eng. Pat. 24,868, 1897) makes special
claim for a soap, termed Monopole Soap, to be used in place of Turkey-red
oils in the dyeing and printing of cotton goods and finishing of textile
fabrics. The soap is prepared by heating the sulphonated oil (obtained on
treatment of castor oil with sulphuric acid) with alkali, and it is stated that
the product is not precipitated when used in the dye-bath as is ordinary
soap, nor is it deposited upon the fibres.
Another patent (Eng. Pat. 16,382, 1897), has for its object the obviating of
the injurious effects upon wool, of alkali liberated from a solution of soap.
It is proposed to accomplish this by sulphonating part of the fat used in
making the soap.
Miscellaneous Soaps.—Under this heading may be classed soaps intended
for special purposes and consisting essentially of ordinary boiled soap to
which additions of various substances have been made.
With additions of naphtha, fractions of petroleum, and turpentine, the
detergent power of the soap is increased by the action of these substances in
removing grease.
Amongst the many other additions may be mentioned: ox-gall or
derivatives therefrom (for carpet-cleaning soap), alkali sulphides (for use of
lead-workers), aniline colours (for home-dyeing soaps), pumice and tripoli
(motorists' soaps), pine-needle oil, in some instances together with lanoline
(for massage soaps), pearl-ash (for soap intended to remove oil and tar

stains), magnesia, rouge, ammonium carbonate, chalk (silversmiths' soap),
powdered orris, precipitated chalk, magnesium carbonate (tooth soaps).
Soap powders or dry soaps are powdered mixtures of soap, soda ash, or
soda crystals, and other chemicals, whilst polishing soaps often contain
from 85 to 90 per cent. siliceous matter, and can scarcely be termed soap.

CHAPTER VIII.
SOAP PERFUMES.

Essential Oils—Source and Preparation—Properties—Artificial
and Synthetic Perfumes.
The number of raw materials, both natural and artificial, at the disposal of
the perfumer, has increased so enormously during recent years that the
scenting of soaps has now become an art requiring very considerable skill,
and a thorough knowledge of the products to be handled. Not only does the
all-important question of odour come into consideration, but the action of
the perfumes on the soap, and on each other, has also to be taken into
account. Thus, many essential oils and synthetic perfumes cause the soap to
darken rapidly on keeping, e.g., clove oil, cassia oil, heliotropin, vanillin.
Further, some odoriferous substances, from their chemical nature, are
incompatible with soap, and soon decompose any soap to which they are
added, while in a few cases, the blending of two unsuitable perfumes
results, by mutual reaction, in the effect of each being lost. In the case of
oils like bergamot oil, the odour value of which depends chiefly on their
ester content, it is very important that these should not be added to soaps
containing much free alkali, as these esters are readily decomposed thereby.
Some perfumes possess the property of helping the soap to retain other and
more delicate odours considerably longer than would otherwise be possible.
Such perfumes are known as "fixing agents" or "fixateurs," and among the
most important of these may be mentioned musk, both natural and artificial,
civet, the oils of Peru balsam, sandalwood, and patchouli, and benzyl
benzoate.
The natural perfumes employed for addition to soaps are almost entirely of
vegetable origin, and consist of essential oils, balsams, and resins, animal
perfumes such as musk, civet, and ambergris being reserved principally for
the preparation of "extraits".
As would be expected with products of such diverse character, the methods
employed for the preparation of essential oils vary considerably. Broadly
speaking, however, the processes may be divided into three classes—(1)
expression, used for orange, lemon, and lime oils; (2) distillation, employed
for otto of rose, geranium, sandalwood, and many other oils; and (3)
extraction, including enfleurage, by which the volatile oil from the flowers
is either first absorbed by a neutral fat such as lard, and then extracted

therefrom by maceration in alcohol, or directly extracted from the flowers
by means of a volatile solvent such as benzene, petroleum ether, or
chloroform. The last process undoubtedly furnishes products most nearly
resembling the natural floral odours, and is the only one which does not
destroy the delicate fragrance of the violet and jasmine. The yield, however,
is extremely small, and concrete perfumes prepared in this way are
therefore somewhat costly.
The essential oils used are derived from upwards of twenty different
botanical families, and are obtained from all parts of the world. Thus, from
Africa we have geranium and clove oils; from America, bay, bois de rose,
Canadian snake root, cedarwood, linaloe, peppermint, petitgrain, and
sassafras; from Asia, camphor, cassia, cinnamon, patchouli, sandalwood,
star anise, ylang-ylang, and the grass oils, viz., citronella, lemongrass,
palmarosa, and vetivert; from Australia, eucalyptus; while in Europe there
are the citrus oils, bergamot, lemon, and orange, produced by Sicily, aspic,
lavender, neroli, petitgrain, and rosemary by France, caraway and clove by
Holland, anise by Russia, and otto of rose by Bulgaria.
Attempts have been made to classify essential oils either on a botanical
basis or according to their chemical composition, but neither method is very
satisfactory, and, in describing the chief constituents and properties of the
more important oils, we have preferred therefore to arrange them
alphabetically, as being simpler for reference.
It is a matter of some difficulty to judge the purity of essential oils, not only
because of their complex nature, but owing to the very great effect upon
their properties produced by growing the plants in different soils and under
varying climatic conditions, and still more to the highly scientific methods
of adulteration adopted by unscrupulous vendors. The following figures will
be found, however, to include all normal oils.
Anise Stell, or Star Anise, from the fruit of Illicium verum, obtained from
China. Specific gravity at 15° C., 0.980-0.990; optical rotation, faintly
dextro- or lævo-rotatory, +0° 30' to -2°; refractive index at 20° C., 1.553-
1.555; solidifying point, 14°-17° C.; solubility in 90 per cent. alcohol, 1 in 3
or 4.

The chief constituents of the oil are anethol, methyl chavicol, d-pinene, l-
phellandrene, and in older oils, the oxidation products of anethol, viz. anisic
aldehyde and anisic acid. Since anethol is the most valuable constituent, and
the solidifying point of the oil is roughly proportional to its anethol content,
oils with a higher solidifying point are the best.
Aspic oil, from the flowers of Lavandula spica, obtained from France and
Spain, and extensively employed in perfuming household and cheap toilet
soaps; also frequently found as an adulterant in lavender oil. Specific
gravity at 15° C., 0.904-0.913; optical rotation, French, dextro-rotatory up
to +4°, rarely up to +7°, Spanish, frequently slightly lævo-rotatory to -2°, or
dextro-rotatory up to +7°; esters, calculated as linalyl acetate, 2 to 6 per
cent.; most oils are soluble in 65 per cent. alcohol 1 in 4, in no case should
more than 2.5 volumes of 70 per cent. alcohol be required for solution.
The chief constituents of the oil are: linalol, cineol, borneol, terpineol,
geraniol, pinene, camphene and camphor.
Bay oil, distilled from the leaves of Pimenta acris, and obtained from St.
Thomas and other West Indian Islands. It is used to some extent as a
perfume for shaving soaps, but chiefly in the Bay Rhum toilet preparation.
Specific gravity at 15° C., 0.965-0.980; optical rotation, slightly lævo-
rotatory up to -3°; phenols, estimated by absorption with 5 per cent. caustic
potash solution, from 45 to 60 per cent.; the oil is generally insoluble in 90
per cent. alcohol, though when freshly distilled it dissolves in its own
volume of alcohol of this strength.
The oil contains eugenol, myrcene, chavicol, methyl eugenol, methyl
chavicol, phellandrene, and citral.
Bergamot oil, obtained by expression from the fresh peel of the fruit of
Citrus Bergamia, and used very largely for the perfuming of toilet soaps.
Specific gravity at 15° C., 0.880-0.886; optical rotation, +10° to +20°;
esters, calculated as linalyl acetate, 35-40 per cent., and occasionally as
high as 42-43 per cent.; frequently soluble in 1.5 parts of 80 per cent.
alcohol, or failing that, should dissolve in one volume of 82.5 or 85 per
cent. alcohol. When evaporated on the water-bath the oil should not leave
more than 5-6 per cent. residue.

Among the constituents of this oil are: linalyl acetate, limonene, dipentene,
linalol, and bergaptene.
Bitter Almond Oil.—The volatile oil obtained from the fruit of Amygdalus
communis. Specific gravity at 15° C., 1.045-1.06; optically inactive;
refractive index at 20° C., 1.544-1.545; boiling point, 176-177° C.; soluble
in 1 or 1.5 volumes of 70 per cent. alcohol.
The oil consists almost entirely of benzaldehyde which may be estimated by
absorption with a hot saturated solution of sodium bisulphite. The chief
impurity is prussic acid, which is not always completely removed. This may
be readily detected by adding to a small quantity of the oil two or three
drops of caustic soda solution, and a few drops of ferrous sulphate solution
containing ferric salt. After thoroughly shaking, acidulate with dilute
hydrochloric acid, when a blue coloration will be produced if prussic acid is
present.
The natural oil may frequently be differentiated from artificial
benzaldehyde by the presence of chlorine in the latter. As there is now on
the market, however, artificial oil free from chlorine, it is no longer
possible, by chemical means, to distinguish with certainty between the
natural and the artificial product. To test for chlorine in a sample, a small
coil of filter paper, loosely rolled, is saturated with the oil, and burnt in a
small porcelain dish, covered with an inverted beaker, the inside of which is
moistened with distilled water. When the paper is burnt, the beaker is rinsed
with water, filtered, and the filtrate tested for chloride with silver nitrate
solution.
Canada snake root oil, from the root of Asarum canadense. Specific gravity
at 15° C., 0.940-0.962; optical rotation, slightly lævo-rotatory up to -4°;
refractive index at 20° C., 1.485-1.490; saponification number, 100-115;
soluble in 3 or 4 volumes of 70 per cent. alcohol.
The principal constituents of the oil are a terpene, asarol alcohol, another
alcohol, and methyl eugenol. The oil is too expensive to be used in other
than high-class toilet soaps.
Cananga or Kananga oil, the earlier distillate from the flowers of Cananga
odorata, obtained chiefly from the Philippine Islands. Specific gravity at

15° C., 0.910-0.940; optical rotation, -17° to -30°; refractive index at 20°
C., 1.4994-1.5024; esters, calculated as linalyl benzoate, 8-15 per cent.;
soluble in 1.5 to 2 volumes of 95 per cent. alcohol, but becoming turbid on
further addition.
The oil is qualitatively similar in composition to Ylang-Ylang oil, and
contains linalyl benzoate and acetate, esters of geraniol, cadinene, and
methyl ester of p-cresol.
Caraway oil, distilled from the seeds of Carum carui. Specific gravity at
15° C., 0.907-0.915; optical rotation, +77° to +79°; refractive index at 20°
C., 1.485-1.486; soluble in 3 to 8 volumes of 80 per cent. alcohol. The oil
should contain 50-60 per cent. of carvone, which is estimated by absorption
with a saturated solution of neutral sodium sulphite. The remainder of the
oil consists chiefly of limonene.
Cassia oil, distilled from the leaves of Cinnamomum cassia, and shipped to
this country from China in lead receptacles. Specific gravity at 15° C.,
1.060-1.068; optical rotation, slightly dextro-rotatory up to +3° 30';
refractive index at 20° C., 1.6014-1.6048; soluble in 3 volumes of 70 per
cent. alcohol as a general rule, but occasionally requires 1 to 2 volumes of
80 per cent. alcohol.
The value of the oil depends upon its aldehyde content, the chief constituent
being cinnamic aldehyde. This is determined by absorption with a hot
saturated solution of sodium bisulphite. Three grades are usually offered,
the best containing 80-85 per cent. aldehydes, the second quality, 75-80 per
cent., and the lowest grade, 70-75 per cent.
Other constituents of the oil are cinnamyl acetate and cinnamic acid. This
oil gives the characteristic odour to Brown Windsor soap, and is useful for
sweetening coal-tar medicated soaps.
Cedarwood oil, distilled from the wood of Juniperus virginiana. Specific
gravity at 15° C., 0.938-0.960; optical rotation, -35° to -45°; refractive
index at 20° C., 1.5013-1.5030. The principal constituents are cedrene and
cedrol.
Cinnamon oil, distilled from the bark of Cinnamomum zeylanicum.
Specific gravity at 15° C., 1.00-1.035; optical rotation, lævo-rotatory up to

-2°; usually soluble in 2 to 3 volumes of 70 per cent. alcohol, but sometimes
requires 1 volume of 80 per cent. alcohol for solution; aldehydes, by
absorption with sodium bisulphite solution, 55-75 per cent.; and phenols, as
measured by absorption with 5 per cent. potash, not exceeding 12 per cent.
The value of this oil is not determined entirely by its aldehyde content as is
the case with cassia oil, and any oil containing more than 75 per cent.
aldehydes must be regarded with suspicion, being probably admixed with
either cassia oil or artificial cinnamic aldehyde. The addition of cinnamon
leaf oil which has a specific gravity at 15° C. of 1.044-1.065 is detected by
causing a material rise in the proportion of phenols. Besides cinnamic
aldehyde the oil contains eugenol and phellandrene.
Citronella Oil.—This oil is distilled from two distinct Andropogon grasses,
the Lana Batu and the Maha pangiri, the former being the source of the bulk
of Ceylon oil, and the latter being cultivated in the Straits Settlements and
Java. The oils from these three localities show well-defined chemical
differences.
Ceylon Citronella oil has the specific gravity at 15° C., 0.900-0.920; optical
rotation, lævo-rotatory up to -12°; refractive index at 20° C., 1.480-1.484;
soluble in 1 volume of 80 per cent. alcohol; total acetylisable constituents,
calculated as geraniol, 54-70 per cent.
Singapore Citronella Oil.—Specific gravity at 15° C., 0.890-0.899; optical
rotation, usually slightly lævo-rotatory up to -3°; refractive index at 20° C.,
1.467-1.471; soluble in 1 to 1.5 volumes of 80 per cent. alcohol; total
acetylisable constituents, calculated as geraniol, 80-90 per cent.
Java Citronella Oil.—Specific gravity at 15° C., 0.890-0.901; optical
rotation, -1° to -6°; total acetylisable constituents, calculated as geraniol,
75-90 per cent.; soluble in 1-2 volumes of 80 per cent. alcohol.
The chief constituents of the oil are geraniol, citronellal, linalol, borneol,
methyl eugenol, camphene, limonene, and dipentene. It is very largely used
for perfuming cheap soaps, and also serves as a source for the production of
geraniol.
Bois de Rose Femelle oil, or Cayenne linaloe oil, distilled from wood of
trees of the Burseraceæ species. Specific gravity at 15° C., 0.874-0.880;

optical rotation, -11° 30' to -16°; refractive index at 20° C., 1.4608-1.4630;
soluble in 1.5 to 2 volumes of 70 per cent. alcohol.
The oil consists almost entirely of linalol, with traces of saponifiable
bodies, but appears to be free from methyl heptenone, found by Barbier and
Bouveault in Mexican linaloe oil. This oil is distinctly finer in odour than
the Mexican product.
Clove oil, distilled from the unripe blossoms of Eugenia caryophyllata, the
chief source of which is East Africa (Zanzibar and Pemba). Specific gravity
at 15° C., 1.045-1.061; optical rotation, slightly lævo-rotatory up to -1° 30';
phenols, estimated by absorption with 5 per cent. potash solution, 86-92 per
cent.; refractive index at 20° C., 1.5300-1.5360; soluble in 1 to 2 volumes
of 70 per cent. alcohol.
The principal constituent of the oil is eugenol, together with caryophyllene
and acet-eugenol. While within certain limits the value of this oil is
determined by its eugenol content, oils containing more than 93 per cent.
phenols are usually less satisfactory in odour, the high proportion of
phenols being obtained at the expense of the decomposition of some of the
sesquiterpene. Oils with less than 88 per cent. phenols will be found
somewhat weak in odour. This oil is extensively used in the cheaper toilet
soaps and is an important constituent of carnation soaps. As already
mentioned, however, it causes the soap to darken in colour somewhat
rapidly, and must not therefore be used in any quantity, except in coloured
soaps.
Concrete orris oil, a waxy substance obtained by steam distillation of
Florentine orris root.
Melting point, 35-45° C., usually 40-45° C.; free acidity, calculated as
myristic acid, 50-80 per cent.; ester, calculated as combined myristic acid,
4-10 per cent.
The greater part of the product consists of the inodorous myristic acid, the
chief odour-bearing constituent being irone. The high price of the oil
renders its use only possible in the very best quality soaps.
Eucalyptus Oil.—Though there are some hundred or more different oils
belonging to this class, only two are of much importance to the soap-maker.

These are:—
(i.) Eucalyptus citriodora. Specific gravity at 15° C., 0.870-0.905; optical
rotation, slightly dextro-rotatory up to +2°; soluble in 4-5 volumes of 70 per
cent. alcohol.
The oil consists almost entirely of citronellic aldehyde, and on absorption
with saturated solution of sodium bisulphite should leave very little oil
unabsorbed.
(ii.) Eucalyptus globulus, the oil used in pharmacy, and containing 50-65
per cent. cineol. Specific gravity at 15° C., 0.910-0.930; optical rotation,
+1° to +10°; soluble in 2 to 3 parts of 70 per cent. alcohol; cineol (estimated
by combination with phosphoric acid, pressing, decomposing with hot
water, and measuring the liberated cineol), not less than 50 per cent.
Besides cineol, the oil contains d-pinene, and valeric, butyric, and caproic
aldehydes. It is chiefly used in medicated soaps.
Fennel (sweet) oil, obtained from the fruit of Fœniculum vulgare, grown in
Germany, Roumania, and other parts of Europe. Specific gravity at 15° C.,
0.965-0.985; optical rotation, +6° to +25°; refractive index at 20° C., 1.515-
1.548; usually soluble in 2-6 parts 80 per cent. alcohol, but occasionally
requires 1 part of 90 per cent. alcohol.
The chief constituents of the oil are anethol, fenchone, d-pinene, and
dipentene.
Geranium oils, distilled from plants of the Pelargonium species. There are
three principal kinds of this oil on the market—the African, obtained from
Algeria and the neighbourhood, the Bourbon, distilled principally in the
Island of Réunion, and the Spanish. The oil is also distilled from plants
grown in the South of France, but this oil is not much used by soap-makers.
A specially fine article is sold by a few essential oil firms under the name of
"Geranium-sur-Rose," which as its name implies, is supposed to be
geranium oil distilled over roses. This is particularly suitable for use in
high-class soaps. The following are the general properties of these oils. It
will be seen that the limits for the figures overlap to a considerable extent.

African. Bourbon. Spanish. French.

Specific gravity at 15°
.890-.900 .888-.895 .895-.898 .897-.900
C.
Optical rotation. -6° to -10° -9° to -18° -8° to -11° -8° to -11°
Esters, calculated as 20-27 per 27-32 per 20-27 per 18-23 per
geranyl tiglate cent. cent. cent. cent.
Total alcohols, as 68-75 per 70-80 per 65-75 per 66-75 per
geraniol. cent. cent. cent. cent.
Solubility in 70 per
1 in 1.5-2 1 in 1.5-2 1 in 2-3 1 in 1.5-2
cent. alcohol.

The oil contains geraniol and citronellol, both free, and combined with
tiglic, valeric, butyric, and acetic acids; also l-menthone. The African and
Bourbon varieties are the two most commonly used for soap-perfurmery,
the Spanish oil being too costly for extensive use.
Ginger-grass oil, formerly regarded as an inferior kind of palma-rosa but
now stated to be from an entirely different source. Specific gravity at 15°
C., 0.889-0.897; optical rotation, +15°.
The oil contains a large amount of geraniol, together with di-hydrocumin
alcohol, d-phellandrene, d-limonene, dipentene, and l-carvone.
Guaiac wood oil, distilled from the wood of Bulnesia sarmienti. Specific
gravity at 30° C., 0.967-0.975; optical rotation, -4° 30' to -7°; refractive
index at 20° C., 1.506-1.507; soluble in 3 to 5 volumes of 70 per cent.
alcohol.
The principal constituent of the oil is guaiac alcohol, or gusiol. This oil,
which has what is generally termed a "tea-rose odour," is occasionally used
as an adulterant for otto of rose.
Lavender oil, distilled from the flowers of Lavandula vera, grown in
England, France, Italy and Spain. The English oil is considerably the most
expensive, and is seldom, if ever, used in soap. The French and Italian oils
are the most common, the Spanish oil being a comparatively new article, of
doubtful botanical origin, and more closely resembling aspic oil.
English Oil.—Specific gravity at 15° C., 0.883-0.900; optical rotation, -4°
to -10°; esters, calculated as linalyl acetate, 5-10 per cent.; soluble in 3

volumes of 70 per cent. alcohol.
French and Italian Oils.—Specific gravity at 15° C., 0.885-0.900; optical
rotation, -2° to -9°; refractive index at 20° C., 1.459-1.464; esters,
calculated as linalyl acetate, 20-40 per cent., occasionally higher; soluble in
1.5-3 volumes of 70 per cent. alcohol.
There was at one time a theory that the higher the proportion of ester the
better the oil, but this theory has now to a very large extent become
discredited, and there is no doubt that some of the finest oils contain less
than 30 per cent. of esters.
Spanish Oil.—Specific gravity at 15° C., 0.900-0.915; optical rotation, -2°
to +7°; esters, calculated as linalyl acetate, 2-6 per cent.; soluble in 1-2
volumes of 70 per cent. alcohol.
The chief constituents of lavender oil are linalyl acetate, linalol, geraniol,
and linalyl butyrate, while the English oil also contains a distinct amount of
cineol.
Lemon oil, prepared by expressing the peel of the nearly ripe fruit of Citrus
limonum, and obtained almost entirely from Sicily and Southern Italy.
Specific gravity at 15° C., 0.856-0.860; optical rotation, +58° to +63°;
refractive index at 20° C., 1.4730-1.4750; aldehydes (citral), 2.5 to 4 per
cent.
The principal constituents of the oil are limonene and citral, together with
small quantities of pinene, phellandrene, octyl and nonyl aldehydes,
citronellal, geraniol, geranyl acetate, and the stearopten, citraptene.
Lemon-grass (so-called verbena) oil, distilled from the grass Andropogon
citratus, which is grown in India and, more recently, in the West Indies. The
oils from these two sources differ somewhat in their properties, and also in
value, the former being preferred on account of its greater solubility in
alcohol.
East Indian.—Specific gravity at 15° C., 0.898-0.906; optical rotation, -0°
30' to -6°; aldehydes, by absorption with bisulphite of soda solution, 65 to
78 per cent.; refractive index at 20° C., 1.485-1.487; soluble in 2-3 volumes
of 70 per cent. alcohol.

West Indian.—Specific gravity at 15° C., 0.886-0.893; optical rotation,
faintly lævo-gyrate; refractive index at 20° C., 1.4855-1.4876; soluble in 0.5
volume of 90 per cent. alcohol.
Lime oil, obtained by expression or distillation of the peel of the fruit of
Citrus medica, and produced principally in the West Indies.
Expressed Oil.—Specific gravity at 15° C., 0.870-0.885; optical rotation,
+38° to +50°. Its most important constituent is citral.
Distilled Oil.—This is entirely different in character to the expressed oil. Its
specific gravity at 15° C. is 0.854-0.870; optical rotation, +38° to +54°;
soluble in 5-8 volumes of 90 per cent. alcohol.
Linaloe oil, distilled from the wood of trees of the Burseraceæ family, and
obtained from Mexico. Specific gravity at 15° C., 0.876-0.892; optical
rotation, usually lævo-rotatory, -3° to -13°, but occasionally dextro-rotatory
up to +5° 30'; esters, calculated as linalyl acetate, 1-8 per cent.; total
alcohols as linalol, determined by acetylation, 54-66 per cent.; soluble in 1-
2 volumes of 70 per cent. alcohol.
This oil consists mainly of linalol, together with small quantities of methyl
heptenone, geraniol, and d-terpineol.
Marjoram oil, distilled from Origanum majoranoides, and obtained entirely
from Cyprus. Specific gravity at 15° C., 0.966; phenols, chiefly carvacrol,
estimated by absorption with 5 per cent. caustic potash solution, 80-82 per
cent.; soluble in 2-3 volumes of 70 per cent. alcohol.
This oil is used in soap occasionally in place of red thyme oil.
Neroli Bigarade oil, distilled from the fresh blossoms of the bitter orange,
Citrus bigaradia. Specific gravity at 15° C., 0.875-0.882; optical rotation,
+0° 40' to +10°, and occasionally much higher; refractive index at 20° C.,
1.468-1.470; esters, calculated as linalyl acetate, 10-18 per cent.; soluble in
0.75-1.75 volumes of 80 per cent. alcohol, becoming turbid on further
addition of alcohol.
The chief constituents of the oil are limonene, linalol, linalyl acetate,
geraniol, methyl anthranilate, indol, and neroli camphor.

Orange (sweet) oil, expressed from the peel of Citrus aurantium. Specific
gravity at 15° C., 0.849-0.852; optical rotation, +95° to +99°; refractive
index at 20° C., 1.4726-1.4732.
The oil contains some 90 per cent. limonene, together with nonyl alcohol,
d-linalol, d-terpineol, citral, citronellal, decyl aldehyde, and methyl
anthranilate.
Palmarosa, or East Indian geranium oil, distilled from Andropogon
Schœnanthus, a grass widely grown in India. Specific gravity at 15° C.,
0.888-0.895; optical rotation, +1° to -3°; refractive index at 20° C., 1.472-
1.476; esters, calculated as linalyl acetate, 7-14 per cent.; total alcohols, as
geraniol, 75-93 per cent.; solubility in 70 per cent. alcohol, 1 in 3.
The oil consists chiefly of geraniol, free, and combined with acetic and
caproic acids, and dipentene. It is largely used in cheap toilet soaps,
particularly in rose soaps. It is also a favourite adulterant for otto of rose,
and is used as a source of geraniol.
Patchouli oil, distilled from the leaves of Pogostemon patchouli, a herb
grown in India and the Straits Settlements. Specific gravity at 15° C., 0.965-
0.990; optical rotation, -45° to -63°; refractive index at 20° C., 1.504-1.511;
saponification number, up to 12; sometimes soluble in 0.5 to 1 volume of
90 per cent. alcohol, becoming turbid on further addition. The solubility of
the oil in alcohol increases with age. The oil consists to the extent of 97 per
cent. of patchouliol and cadinene, which have little influence on its odour,
and the bodies responsible for its persistent and characteristic odour have
not yet been isolated.
Peppermint oil, distilled from herbs of the Mentha family, the European and
American from Mentha piperita, and the Japanese being generally supposed
to be obtained from Mentha arvensis. The locality in which the herb is
grown has a considerable influence on the resulting oil, as the following
figures show:—
English.—Specific gravity at 15° C., 0.900-0.910; optical rotation, -22° to
-33°; total menthol, 55-66 per cent.; free menthol, 50-60 per cent.; soluble
in 3-5 volumes of 70 per cent. alcohol.

American.—Specific gravity at 15° C., 0.906-0.920; optical rotation, -20°
to -33°; total menthol, 50-60 per cent.; free menthol, 40-50 per cent. The
Michigan oil is soluble in 3-5 volumes of 70 per cent. alcohol, but the better
Wayne County oil usually requires 1-2 volumes of 80 per cent. alcohol, and
occasionally 0.5 volume of 90 per cent. alcohol.
French.—Specific gravity at 15° C., 0.917-0.925; optical rotation, -6° to
-10°; total menthol, 45-55 per cent.; free menthol, 35-45 per cent.; soluble
in 1 to 1.5 volumes of 80 per cent.
Japanese.—Specific gravity at 25° C., 0.895-0.900; optical rotation, lævo-
rotatory up to -43°; solidifies at 17 to 27° C.; total menthol, 70-90 per cent.,
of which 65-85 per cent. is free; soluble in 3-5 volumes of 70 per cent.
alcohol.
The dementholised oil is fluid at ordinary temperatures, has a specific
gravity of 0.900-0.906 at 15° C., and contains 50-60 per cent. total menthol.
Some twenty different constituents have been found in American
peppermint oil, including menthol, menthone, menthyl acetate, cineol, amyl
alcohol, pinene, l-limonene, phellandrene, dimethyl sulphide, menthyl
isovalerianate, isovalerianic aldehyde, acetaldehyde, acetic acid, and
isovalerianic acid.
Peru balsam oil, the oily portion (so-called "cinnamein") obtained from
Peru balsam. Specific gravity at 15° C., 1.100-1.107; optical rotation,
slightly dextro-rotatory up to +2°; refractive index at 20° C., 1.569 to 1.576;
ester, calculated as benzyl benzoate, 80-87 per cent.; soluble in 1 volume of
90 per cent. alcohol.
The oil consists chiefly of benzyl benzoate and cinnamate, together with
styracin, or cinnamyl cinnamate, and a small quantity of free benzoic and
cinnamic acids.
Petitgrain oil, obtained by distillation of the twigs and unripe fruit of Citrus
bigaradia. There are two varieties of the oil, the French and the South
American, the former being the more valuable. Specific gravity at 15° C.,
0.886-0.900; optical rotation, -3° to +6°; refractive index at 20° C., 1.4604-
1.4650; esters, calculated as linalyl acetate, 40-55 per cent., for the best
qualities usually above 50 per cent.; soluble as a rule in 2-3 volumes of 70

per cent. alcohol, but occasionally requires 1-2 volumes of 80 per cent.
alcohol.
Among its constituents are limonene, linalyl acetate, geraniol and geranyl
acetate.
Pimento oil (allspice), distilled from the fruit of Pimenta officinalis, which
is found in the West Indies and Central America. Specific gravity at 15° C.,
1.040-1.060; optical rotation, slightly lævo-rotatory up to -4°; refractive
index at 20° C., 1.529-1.536; phenols, estimated by absorption with 5 per
cent. potash solution, 68-86 per cent.; soluble in 1-2 volumes of 70 per cent.
alcohol.
The oil contains eugenol, methyl eugenol, cineol, phellandrene, and
caryophyllene.
Rose oil (otto of rose), distilled from the flowers of Rosa damascena,
though occasionally the white roses (Rosa alba) are employed. The
principal rose-growing district is in Bulgaria, but a small quantity of rose oil
is prepared from roses grown in Anatolia, Asia Minor. An opinion as to the
purity of otto of rose can only be arrived at after a very full chemical
analysis, supplemented by critical examination of its odour by an expert.
The following figures, however, will be found to include most oils which
can be regarded as genuine. Specific gravity at 30° C., 0.850-0.858; optical
rotation at 30° C., -1° 30' to -3°; refractive index at 20° C., 1.4600-1.4645;
saponification value, 7-11; solidifying point, 19-22° C.; iodine number,
187-194; stearopten content, 14-20 per cent.; melting point of stearopten,
about 32° C.
A large number of constituents have been isolated from otto of rose, many
of which are, however, only present in very small quantities. The most
important are geraniol, citronellol, phenyl ethyl alcohol, together with nerol,
linalol, citral, nonylic aldehyde, eugenol, a sesquiterpene alcohol, and the
paraffin stearopten.
Rosemary oil, distilled from the herb Rosemarinus officinalis, and obtained
from France, Dalmatia, and Spain. The herb is also grown in England, but
the oil distilled therefrom is rarely met with in commerce. The properties of
the oils vary with their source, and also with the parts of the plant distilled,

distillation of the stalks as well as the leaves tending to reduce the specific
gravity and borneol content, and increase the proportion of the lævo-
rotatory constituent (lævo-pinene). The following figures may be taken as
limits for pure oils:—
French and Dalmatian.—Specific gravity at 15° C., 0.900-0.916; optical
rotation, usually dextro-rotatory, up to +15°, but may occasionally be lævo-
rotatory, especially if stalks have been distilled with the leaves; ester,
calculated as bornyl acetate, 1-6 per cent.; total borneol, 12-18 per cent.;
usually soluble in 1-2 volumes of 82.5 per cent. alcohol.
Spanish.—The properties of the Spanish oil are similar to the others, except
that it is more frequently lævo-rotatory.
Rosemary oil contains pinene, camphene, cineol, borneol, and camphor.
Sandalwood oil, obtained by distillation of the wood of Santalum album
(East Indian), Santalum cygnorum (West Australian), and Amyris
balsamifera (West Indian). The oils obtained from these three different
sources differ very considerably in value, the East Indian being by far the
best.
East Indian.—Specific gravity at 15° C., 0.975-0.980; optical rotation, -14°
to -20°; refractive index at 20° C., 1.5045-1.5060; santalol, 92-97 per cent.;
usually soluble in 4-6 volumes of 70 per cent. alcohol, though, an old oil
occasionally is insoluble in 70 per cent. alcohol.
West Australian.—Specific gravity at 15° C., 0.950-0.968; optical rotation,
+5° to +7°; alcohols, calculated as santalol, 73-75 per cent.; insoluble in 70
per cent. alcohol, but readily dissolves in 1-2 volumes of 80 per cent.
alcohol.
West Indian.—Specific gravity at 15° C., 0.948-0.967; optical rotation,
+13° 30' to +30°; insoluble in 70 per cent. alcohol.
In addition to free santalol, the oil contains esters of santalol and santalal.
Sassafras oil, distilled from the bark of Sassafras officinalis, and obtained
chiefly from America. Specific gravity at 15° C., 1.06-1.08; optical rotation,
+1° 50' to +4°; refractive index at 20° C., 1.524-1.532; soluble in, 6-10

volumes of 85 per cent. alcohol, frequently soluble in 10-15 volumes of 80
per cent. alcohol.
The chief constituents are safrol, pinene, eugenol, camphor, and
phellandrene. The removal of safrol, either intentionally or by accident,
owing to cooling of the oil and consequent deposition of the safrol, is
readily detected by the reduction of the specific gravity below 1.06.
Thyme oil, red and white, distilled from the green or dried herb, Thymus
vulgaris, both French and Spanish oils being met with. These oils are
entirely different in character.
French.—Specific gravity at 15° C., 0.91-0.933; slightly lævo-rotatory up to
-4°, but usually too dark to observe; phenols, by absorption with 10 per
cent. aqueous caustic potash, 25-55 per cent.; refractive index at 20° C.,
1.490-1.500; soluble in 1-1.5 volumes of 80 per cent. alcohol.
Spanish.—Specific gravity at 15° C., 0.955-0.966; optical rotation, slightly
lævo-gyrate; phenols, 70-80 per cent.; refractive index at 20° C.; 1.5088-
1.5122; soluble in 2-3 volumes of 70 per cent. alcohol.
In addition to the phenols, thymol or carvacrol, these oils contain cymene,
thymene and pinene.
The white thyme oil is produced by rectifying the red oil, which is generally
effected at the expense of a considerable reduction in phenol content, and
hence in real odour value of the oil.
Verbena Oil.—The oil usually sold under this name is really lemon-grass oil
(which see supra). The true verbena oil or French verveine is, however,
occasionally met with. This is distilled in France from the verbena
officinalis, and has the following properties: Specific gravity at 15° C.,
0.891-0.898; optical rotation, slightly dextro- or lævo-rotatory; aldehydes,
70-75 per cent.; soluble in 2 volumes of 70 per cent. alcohol.
The oil contains citral.
Vetivert oil, distilled from the grass, Andropogon muricatus, or Cus Cus,
and grown in the East Indies.

Specific gravity at 15° C., 1.01-1.03; optical rotation, +20° to +26°;
saponification number, 15-30; refractive index at 20° C., 1.521-1.524;
soluble in 2 volumes of 80 per cent. alcohol.
The price of this oil makes its use prohibitive except in the highest class
soaps.
Wintergreen Oil.—There are two natural sources of this oil, the Gaultheria
procumbens and the Betula lenta. Both oils consist almost entirely of
methyl salicylate and are practically identical in properties, the chief
difference being that the former has a slight lævo-rotation, while the latter is
inactive.
Specific gravity at 15° C., 1.180-1.187; optical rotation, Gaultheria oil, up
to -1°, Betula oil, inactive; ester as methyl salicylate, at least 98 per cent.;
refractive index at 20° C., 1.5354-1.5364; soluble in 2-6 volumes of 70 per
cent. alcohol.
Besides methyl salicylate, the oil contains triaconitane, an aldehyde or
ketone, and an alcohol.
Ylang-ylang oil, distilled from the flowers of Cananga odorata, the chief
sources being the Philippine Islands and Java. Specific gravity at 15° C.,
0.924-0.950; optical rotation, -30° to -60°, and occasionally higher;
refractive index at 20° C., 1.496-1.512; ester, calculated as linalyl benzoate,
27-45 per cent., occasionally up to 50 per cent.; usually soluble in 1/2
volume of 90 per cent. alcohol.
The composition of the oil is qualitatively the same as that of Cananga oil,
but it is considerably more expensive and therefore can only be used in the
highest grade soaps.

Artificial and Synthetic Perfumes.

During the past few years the constitution of essential oils has been studied
by a considerable number of chemists, and the composition of many oils
has been so fully determined that very good imitations can often be made at
cheaper prices than those of the genuine oils, rendering it possible to

produce cheap soaps having perfumes which were formerly only possible in
the more expensive article.
There is a considerable distinction, however, often lost sight of, between an
artificial and a synthetic oil. An artificial oil may be produced by separating
various constituents from certain natural oils, and so blending these, with or
without the addition of other substances, as to produce a desired odour, the
perfume being, at any rate in part, obtained from natural oils. A synthetic
perfume, on the other hand, is entirely the product of the chemical
laboratory, no natural oil or substance derived therefrom entering into its
composition.
The following are among the most important bodies of this class:—
Amyl salicylate, the ester prepared from amyl alcohol and salicylic acid,
sometimes known as "Orchidée" or "Trèfle". This is much used for the
production of a clover-scented soap. It has the specific gravity at 15° C.,
1.052-1.054; optical rotation, +1° 16' to +1° 40'; refractive index at 20° C.,
1.5056; and should contain not less than 97 per cent. ester, calculated as
amyl salicylate.
Anisic aldehyde, or aubépine, prepared by oxidation of anethol, and
possessing a pleasant, hawthorn odour. This has the specific gravity at 15°
C., 1.126; refractive index at 20° C., 1.5693; is optically inactive, and
dissolves readily in one volume of 70 per cent. alcohol.
Benzyl Acetate, the ester obtained from benzyl alcohol and acetic acid. This
has a very strong and somewhat coarse, penetrating odour, distinctly
resembling jasmine. Its specific gravity at 15° C. is 1.062-1.065; refractive
index at 20° C., 1.5020; and it should contain at least 97-98 per cent. ester,
calculated as benzyl acetate.
Citral, the aldehyde occurring largely in lemon-grass and verbena oils, also
to a less extent in lemon and orange oils, and possessing an intense lemon-
like odour. It has a specific gravity at 15° C., 0.896-0.897, is optically
inactive, and should be entirely absorbed by a hot saturated solution of
sodium bisulphite.
Citronellal, an aldehyde possessing the characteristic odour of citronella oil,
in which it occurs to the extent of about 20 per cent., and constituting

considerably over 90 per cent. of eucalyptus citriodora oil. Its specific
gravity at 15° C. is 0.862; refractive index at 20° C., 1.447; optical rotation,
+8° to +12°; and it should be entirely absorbed by a hot saturated solution
of sodium bisulphite.
Coumarin, a white crystalline product found in Tonka beans, and prepared
synthetically from salicylic acid. It has an odour resembling new-mown
hay, and melts at 67° C.
Geraniol, a cyclic alcohol, occurring largely in geranium, palma-rosa, and
citronella oils. Its specific gravity at 15° C. is 0.883-0.885; refractive index
at 20° C., 1.4762-1.4770; it is optically inactive, and boils at 218°-225° C.
Heliotropin, which possesses the characteristic odour of heliotrope, is
prepared artificially from safrol. It crystallises in small prisms melting at
86° C.
Hyacinth.—Most of the articles sold under this name are secret blends of
the different makers. Styrolene has an odour very much resembling
hyacinth, and probably forms the basis of most of these preparations,
together with terpineol, and other artificial bodies. The properties of the oil
vary considerably for different makes.
Ionone, a ketone first prepared by Tiemann, and having when diluted a
pronounced violet odour. It is prepared by treating a mixture of citral and
acetone with barium hydrate, and distilling in vacuo. Two isomeric ketones,
α-ionone and β-ionone, are produced, the article of commerce being usually
a mixture of both. The two ketones have the following properties:—
Alpha-ionone.—Specific gravity at 15° C., 0.9338; refractive index at 16.5
C., 1.50048 (Chuit); optically it is inactive.
Beta-ionone.—Specific gravity at 15° C., 0.9488; refractive index at 16.8°
C., 1.52070 (Chuit); optically it is inactive also.
The product is usually sold in 10 or 20 per cent. alcoholic solution ready for
use.
Jasmine.—This is one of the few cases in which the artificial oil is probably
superior to that obtained from the natural flowers, possibly due to the

extreme delicacy of the odour, and its consequent slight decomposition
during preparation from the flowers. The chemical composition of the floral
perfume has been very exhaustively studied, and the artificial article now
on the market may be described as a triumph of synthetical chemistry.
Among its constituents are benzyl acetate, linalyl acetate, benzyl alcohol,
indol, methyl anthranilate, and a ketone jasmone.
Linalol, the alcohol forming the greater part of linaloe and bois de rose oils,
and found also in lavender, neroli, petitgrain, bergamot, and many other
oils. The article has the specific gravity at 15° C., 0.870-0.876; optical
rotation, -12° to -14°; refractive index at 20° C., 1.463-1.464; and when
estimated by acetylation, yields about 70 per cent. of alcohols.
Linalyl acetate, or artificial bergamot oil, is the ester formed when linalol is
treated with acetic anhydride. It possesses a bergamot-like odour, but it is
doubtful whether its value is commensurate with its greatly increased price
over that of ordinary bergamot oil. It has the specific gravity at 15° C.,
0.912.
Musk (Artificial).—Several forms of this are to be obtained, practically all
of which are nitro-derivatives of aromatic hydrocarbons. The original patent
of Baur, obtained in 1889, covered the tri-nitro-derivative of tertiary butyl
xylene. The melting point of the pure article usually lies between 108° and
112° C., and the solubility in 95 per cent. alcohol ranges from 1 in 120 to 1
in 200, though more soluble forms are also made.
An important adulterant, which should always be tested for, is acetanilide
(antifebrin), which may be detected by the characteristic isocyanide odour
produced when musk containing this substance is boiled with alcoholic
potash, and a few drops of chloroform added. Acetanilide also increases the
solubility in 95 per cent. alcohol.
Neroli Oil (Artificial).—Like jasmine oil, the chemistry of neroli oil is now
very fully known, and it is therefore possible to prepare an artificial product
which is a very good approximation to the natural oil, and many such are
now on the market, which, on account of their comparative cheapness,
commend themselves to the soap-perfumer. These consist chiefly of linalol,
geraniol, linalyl acetate, methyl anthranilate, and citral.

Mirbane Oil or Nitrobenzene.—This is a cheap substitute for oil of bitter
almonds, or benzaldehyde, and is a very coarse, irritating perfume, only
suitable for use in the very cheapest soaps. It is prepared by the action of a
mixture of nitric and sulphuric acids on benzene at a temperature not
exceeding 40° C. Its specific gravity is 1.205-1.206; refractive index at 20°
C., 1.550; and boiling point, 206° C.
Niobe oil, or ethyl benzoate, the ester obtained from ethyl alcohol and
benzoic acid, and having the specific gravity at 15° C., 1.094-1.095;
refractive index at 20° C., 1.5167; boiling point, 196.5°-198° C.; soluble in
1.5 volumes of 70 per cent. alcohol.
Oeillet is a combination possessed of a sweet carnation-like odour and
having as a basis, eugenol or isoeugenol. Its properties vary with the source
of supply.
Rose Oil (Artificial).—Several good and fairly cheap artificial rose oils are
now obtainable, consisting chiefly of citronellol, geraniol, linalol, phenyl
ethyl alcohol, and citral. In some cases stearopten or other wax is added, to
render the oil more similar in appearance to the natural article, but as these
are inodorous, no advantage is gained in this way, and there is, further, the
inconvenience in cold weather of having to first melt the oil before use.
Safrol, an ether which is the chief constituent of sassafras oil, and also
found in considerable quantity in camphor oil. It is sold as an artificial
sassafras oil, and is very much used in perfuming cheap toilet or household
soaps. Its specific gravity at 15° C. is 1.103-1.106; refractive index at 20°
C., 1.5373; and it dissolves in fifteen volumes of 80 per cent. alcohol.
Santalol, the alcohol or mixture of alcohols obtained from sandalwood oil.
Its specific gravity at 15° C. is 0.9795; optical rotation, -18°; and refractive
index at 20° C., 1.507.
Terebene, a mixture of dipentene and other hydrocarbons prepared from
turpentine oil by treatment with concentrated sulphuric acid, is used chiefly
in medicated soaps. Its specific gravity at 15° C. is 0.862-0.868; the oil is
frequently slightly dextro- or lævo-rotatory; the refractive index at 20° C.,
1.470-1.478.

Terpineol, an alcohol also prepared from turpentine oil by the action of
sulphuric acid, terpene hydrate being formed as an intermediate substance.
It has a distinctly characteristic lilac odour, and on account of its cheapness
is much used in soap perfumery, especially for a lilac or lily soap. Its
specific gravity at 15° C. is 0.936-0.940; refractive index at 20° C., 1.4812-
1.4835; and boiling point about 210°-212° C. It is optically inactive, and
readily soluble in 1.5 volumes of 70 per cent. alcohol.
Vanillin, a white crystalline solid, melting at 80°-82° C. and prepared by the
oxidation of isoeugenol. It has a strong characteristic odour, and occurs,
associated with traces of benzoic acid and heliotropin, in the vanilla bean. It
can only be used in small quantity in light-coloured soaps, as it quickly
tends to darken the colour of the soap.

CHAPTER IX.
GLYCERINE MANUFACTURE AND PURIFICATION.

Treatment of Lyes—Evaporation to Crude Glycerine—
Distillation—Distilled and Dynamite Glycerine—Chemically
Pure Glycerine—Animal Charcoal for Decolorisation—
Glycerine obtained by other Methods of Saponification—Yield of
Glycerine from Fats and Oils.
As pointed out in Chapter II. the fatty acids, which, combined with soda or
potash, form soap, occur in nature almost invariably in the form of
glycerides, i.e., compounds of fatty acids with glycerol, and as the result of
saponification of a fat or oil glycerine is set free.
In Chapter V. processes of soap-making are described in which (1) the
glycerine is retained in the finished soap, and (2) the glycerine is contained
in the lyes, in very dilute solution, contaminated with salt and other
impurities. These lyes, though now constituting the chief source of profit in
the manufacture of cheap soaps, were till early in last century simply run
down the drains as waste liquor.
Much attention has been devoted to the purification and concentration of
glycerine lyes; and elaborate plant of various forms has been devised for the
purpose.
Treatment of Lyes.—The spent lyes withdrawn from the soap-pans are
cooled, and the soap, which has separated during the cooling, is carefully
removed and returned to the soap-house for utilisation in the manufacture of
brown soap. Spent lyes may vary in their content of glycerol from 3 to 8 per
cent., and this depends not only upon the system adopted in the working of
the soap-pans, but also upon the materials used. Although, in these days of
pure caustic soda, spent lyes are more free from impurities than formerly,
the presence of sulphides and sulphites should be carefully avoided, if it is
desired to produce good glycerine.

The lyes are transferred to a lead-lined tank of convenient size, and treated
with commercial hydrochloric acid and aluminium sulphate, sufficient
being added of the former to neutralise the free alkali, and render the liquor
faintly acid, and of the latter to completely precipitate the fatty acids. The
acid should be run in slowly, and the point when enough has been added, is
indicated by blue litmus paper being slightly reddened by the lyes.
The whole is then agitated with air, when a sample taken from the tank and
filtered should give a clear filtrate.
Having obtained this clear solution, agitation is stopped, and the contents of
the tank passed through a filter press. The scum, which accumulates on the
treatment tank, may be transferred to a perforated box suspended over the
tank, and the liquor allowed to drain from it. The filtered liquor is now
rendered slightly alkaline by the addition of caustic soda or carbonate, and,
after filtering, is ready for evaporation.
The acid and alum salt used in the above treatment must be carefully
examined for the presence of arsenic, and any deliveries of either article,
which contain that impurity, rejected.
Lime, bog ore, and various metallic salts, such as ferric chloride, barium
chloride, and copper sulphate have been suggested, and in some instances
are used instead of aluminium sulphate, but the latter is generally employed.
Evaporation to Crude Glycerine.—The clear treated lyes, being now free
from fatty, resinous, and albuminous matter, and consisting practically of an
aqueous solution of common salt (sodium chloride) and glycerine, is
converted into crude glycerine by concentration, which eliminates the water
and causes most of the salt to be deposited.
This concentration was originally performed in open pans heated by fire or
waste combustible gases. In the bottom of each pan was placed a dish in
which the salt deposited, and this dish was lifted out periodically by the aid
of an overhead crane and the contents emptied and washed. Concentration
was continued until the temperature of the liquor was 300° F. (149° C.),
when it was allowed to rest before storing.
This liquor on analysis gave 80 per cent. glycerol and from 9 to 10-1/2 per
cent. salts (ash); hence the present standard for crude glycerine.

Concentration in open pans has now been superseded by evaporation in
vacuo. The subject of the gradual development of the modern efficient
evaporating plant from the vacuum pan, originated and successfully applied
by Howard in 1813 in the sugar industry, is too lengthy to detail here,
suffice it to say that the multiple effects now in vogue possess distinct
advantages—the greatest of these being increased efficiency combined with
economy.
The present type of evaporator consists of one or more vessels, each fitted
with a steam chamber through which are fixed vertical hollow tubes. The
steam chamber of the first vessel is heated with direct steam, or with
exhaust steam (supplied from the exhaust steam receiver into which passes
the waste steam of the factory); the treated lyes circulating through the
heated tubes is made to boil at a lower temperature, with the reduced
pressure, than is possible by heating in open pans.
The vapour given off by the boiling liquor is conveyed through large pipes
into the steam chamber of the second vessel, where its latent heat is utilised
in producing evaporation, the pressure being further reduced, as this second
vessel is under a greater vacuum than No. 1. Thus we get a "double effect,"
as the plant consisting of two pans is termed. The vapours discharged from
the second vessel during boiling are passed through pipes to the steam
chamber of the third vessel (in a "triple effect"), and there being condensed,
create a partial vacuum in the second vessel. The third vessel may also be
heated by means of live steam. The vapours arising from the last vessel of
the evaporating plant, or in the case of a "single effect" from the vessel, are
conveyed into a condenser and condensed by injection water, which is
drawn off by means of the pump employed for maintaining a vacuum of 28
inches in the vessel.
In the most recent designs of large evaporative installations, the vapours
generated from the last vessel are drawn through a device consisting of a
number of tubes enclosed in a casing, and the latent heat raises the
temperature of the treated lyes proceeding through the tubes to supply the
evaporator.
It will thus be observed that the object of multiple effects is to utilise all the
available heat in performing the greatest possible amount of work. Special

devices are attached to the plant for automatically removing the condensed
water from the steam chambers without the loss of useful heat, and as a
precaution against splashing over and subsequent loss of glycerine through
conveyance to the steam chamber, dash plates and "catch-alls" or "save-
alls" of various designs are fitted on each vessel.
In working the plant, the liquor in each vessel is kept at a fairly constant
level by judicious feeding from one to the other; the first vessel is, of
course, charged with treated lyes. As the liquor acquires a density of 42°
Tw. (25° B.) salt begins to deposit, and may be withdrawn into one of the
many patented appliances, in which it is freed from glycerine, washed and
dried ready for use at the soap pans. Difficulty is sometimes experienced
with the tubes becoming choked with salt, thereby diminishing and
retarding evaporation. It may be necessary to dissolve the encrusted salt
with lyes or water, but with careful working the difficulty can be obviated
by washing out with weak lyes after each batch of crude glycerine has been
run away, or by increasing the circulation.
It is claimed that by the use of the revolving heater designed by
Lewkowitsch, the salting up of tubes is prevented.
The salt having been precipitated and removed, evaporation is continued
until a sample taken from the last vessel has a density of 60° Tw. (33.3 B.)
at 60° F. (15.5° C.). When this point is reached, the crude glycerine is ready
to be withdrawn into a tank, and, after allowing the excess of salt to deposit,
may be transferred to the storage tank.
The colour of crude glycerine varies from light brown to dark brown,
almost black, and depends largely on the materials used for soap-making.
The organic matter present in good crude glycerine is small in amount,
often less than 1 per cent.; arsenic, sulphides and sulphites should be absent.
Crude glycerine is refined in some cases by the producers themselves;
others sell it to firms engaged more particularly in the refined glycerine
trade.
Distillation.—Crude glycerine is distilled under vacuum with the aid of
superheated steam. The still is heated directly with a coal or coke fire, and
in this fire space is the superheater, which consists of a coil of pipes through
which high pressure steam from the boiler is superheated.

The distillation is conducted at a temperature of 356°F. (180° C.). To
prevent the deposition and burning of salt on the still-bottom during the
distillation, a false bottom is supported about 1 foot from the base of the
still. With the same object in view, it has been suggested to rotate the
contents with an agitator fixed in the still.
Every care is taken that the still does not become overheated; this
precaution not only prevents loss of glycerine through carbonisation, but
also obviates the production of tarry and other bodies which might affect
the colour, taste, and odour of the distilled glycerine. The vacuum to be
used will, of course, depend upon the heat of the fire and still, but as a
general rule good results are obtained with an 18 inch vacuum.
There are quite a large number of designs for still heads, and "catch-alls,"
having for their object the prevention of loss of glycerine.
The distillate passes into a row of condensers, to each of which is attached a
receptacle or receiver. It is needless to state that the condensing capacity
should be in excess of theoretical requirements. The fractions are of varying
strengths and quality; that portion, with a density less than 14° Tw. (19.4°
B.), is returned to the treated-lyes tank. The other portion of the distillate is
concentrated by means of a dry steam coil in a suitable vessel under a 28
inch vacuum.
When sufficiently concentrated the glycerine may be decolorised, if
necessary, by treating with 1 per cent. animal charcoal and passing through
a filter press, from which it issues as "dynamite glycerine".
The residue in the still, consisting of 50-60 per cent. glycerine and varying
proportions of various sodium salts—e.g. acetate, chloride, sulphate, and
combinations with non-volatile organic acids—is generally boiled with
water and treated with acid.
The tar, which is separated, floats on the surface as the liquor is cooling,
and may be removed by ladles, or the whole mixed with waste charcoal,
and filtered.
The filtrate is then evaporated, when the volatile organic acids are driven
off; the concentrated liquor is finally mixed with crude glycerine which is
ready for distillation, or it may be distilled separately.

Distilled Glycerine.—This class of commercial glycerine, although of
limited use in various other branches of industry, finds its chief outlet in the
manufacture of explosives.
Specifications are usually given in contracts drawn up between buyers and
sellers, to which the product must conform.
The chief stipulation for dynamite glycerine is its behaviour in the nitration
test. When glycerine is gradually added to a cold mixture of strong nitric
and sulphuric acids, it is converted into nitro-glycerine, which separates as
an oily layer on the surface of the acid. The more definite and rapid the
separation, the more suitable is the glycerine for dynamite-making.
Dynamite glycerine should be free from arsenic, lime, chlorides, and fatty
acids, the inorganic matter should not amount to more than 0.1 per cent.,
and a portion diluted and treated with nitrate of silver solution should give
no turbidity or discoloration in ten minutes. The specific gravity should be
1.262 at 15° C. (59° F.) and the colour somewhat yellow.
Chemically pure glycerine or double distilled glycerine is produced by
redistilling "once distilled" glycerine. Every care is taken to avoid all
fractions which do not withstand the nitrate of silver test. The distillation is
very carefully performed under strict supervision.
The distillate is concentrated and after treatment with animal charcoal and
filtration should conform to the requirements of the British Pharmacopœia.
These are specified as follows: Specific gravity at 15.5° C., 1.260. It should
yield no characteristic reaction with the tests for lead, copper, arsenium,
iron, calcium, potassium, sodium, ammonium, chlorides, or sulphates. It
should contain no sugars and leave no residue on burning.
Animal Charcoal for Decolorisation.—The application of animal charcoal
for decolorising purposes dates back a century, and various are the views
that have been propounded to explain its action. Some observers base it
upon the physical condition of the so-called carbon present, and no doubt
this is an important factor, coupled with the porosity. Others consider that
the nitrogen, which is present in all animal charcoal and extremely difficult
to remove, is essential to the action. Animal charcoal should be freed from

gypsum (sulphate of lime), lest in the burning, sulphur compounds be
formed which would pass into the glycerine and contaminate it.
The "char" should be well boiled with water, then carbonate of soda or
caustic soda added in sufficient quantity to give an alkaline reaction, and
again well boiled. The liquor is withdrawn and the charcoal washed until
the washings are no longer alkaline. The charcoal is then separated from the
liquor and treated with hydrochloric acid; opinions differ as to the amount
of acid to be used. Some contend that phosphate of lime plays such an
important part in decolorising that it should not be removed, but it has,
however, been demonstrated that this substance after exposure to heat has
very little decolorising power.
Animal charcoal boiled with four times its weight of a mixture consisting of
equal parts of commercial hydrochloric acid (free from arsenic) and water
for twelve hours, then washed free from acid, dried, and burned in closed
vessels gives a product possessed of great decolorising power for use with
glycerines.
A good animal charcoal will have a dull appearance, and be of a deep
colour; it should be used in fine grains and not in the form of a powder.
The charcoal from the filter presses is washed free from glycerine (which is
returned to the treated lyes), cleansed from foreign substances by the above
treatment and revivified by carefully heating in closed vessels for twelve
hours.
Glycerine obtained by other Methods of Saponification.—French
saponification or "candle crude" glycerine is the result of concentration of
"sweet water" produced in the manufacture of stearine and by the autoclave
process. It contains 85-90 per cent. glycerol, possesses a specific gravity of
1.240-1.242, and may be readily distinguished from the soap-crude
glycerine by the absence of salt (sodium chloride). This glycerine is easily
refined by treatment with charcoal.
The glycerine water resulting from acid saponification methods requires to
be rendered alkaline by the addition of lime—the sludge is separated, and
the liquor evaporated to crude. The concentration may be performed in two
stages—first to a density of 32° Tw. (20° B.), when the calcium sulphate is

allowed to deposit, and the separated liquor concentrated to 48° Tw. (28°
B.) glycerine, testing 85 per cent. glycerol and upwards.
Yield of Glycerine from Fats and Oils.—The following represent practicable
results which should be obtained from the various materials:—

Tallow 9 per cent. of 80 per cent. Glycerol.
Cotton-seed oil 10 "
Cocoa-nut oil 12 "
Palm-kernel oil 18 "
Olive oil 10 "
Palm oil 6 "
Greases (Bone fats) 6-8 "

The materials vary in glycerol content with the methods of preparation;
especially is this the case with tallows and greases.
Every care should be taken that the raw materials are fresh and they should
be carefully examined to ascertain if any decomposition has taken place in
the glycerides—this would be denoted by the presence of an excess of free
acidity, and the amount of glycerol obtainable from such a fat would be
correspondingly reduced.

CHAPTER X.
ANALYSIS OF RAW MATERIALS, SOAP, AND
GLYCERINE.

Fats and Oils—Alkalies and Alkali Salts—Essential Oils—Soap
—Lyes—Crude Glycerine.
Raw Materials.—Average figures have already been given in Chapters III.
and VIII. for the more important physical and chemical characteristics of
fats and oils, also of essential oils; the following is an outline of the
processes usually adopted in their determination. For fuller details, text-
books dealing exhaustively with the respective subjects should be
consulted.

Fats and Oils.

It is very undesirable that any of these materials should be allowed to enter
the soap pan without an analysis having first been made, as the oil may not
only have become partially hydrolysed, involving a loss of glycerine, or
contain albuminous matter rendering the soap liable to develop rancidity,
but actual sophistication may have taken place. Thus a sample of tallow
recently examined by the authors contained as much as 40 per cent. of an
unsaponifiable wax, which would have led to disaster in the soap pan, had
the bulk been used without examination. After observing the appearance,
colour, and odour of the sample, noting any characteristic feature, the
following physical and chemical data should be determined.
Specific Gravity at 15° C. This may be taken by means of a Westphal
balance, or by using a picnometer of either the ordinary gravity bottle
shape, with perforated stopper, or the Sprengel U-tube. The picnometer
should be calibrated with distilled water at 15° C. The specific gravity of
solid fats may be taken at an elevated temperature, preferably that of a
boiling water bath.

Free acidity is estimated by weighing out from 2 to 5 grammes of the fat or
oil, dissolving in neutral alcohol (purified methylated spirit) with gentle
heat, and titrating with a standard aqueous or alcoholic solution of caustic
soda or potash, using phenol-phthalein as indicator.
The contents of the flask are well shaken after each addition of alkali, and
the reaction is complete when the slight excess of alkali causes a permanent
pink coloration with the indicator. The standard alkali may be N/2, N/5, or
N/10.
It is usual to calculate the result in terms of oleic acid (1 c.c. N/10 alkali =
0.0282 gramme oleic acid), and express in percentage on the fat or oil.
Example.—1.8976 grammes were taken, and required 5.2 c.c. of N/10 KOH
solution for neutralisation.

5.2 × 0.0282 × 100
7.72 per cent. free fatty acids, expressed as oleic
————————— =
acid.
1.8976

The free acidity is sometimes expressed as acid value, which is the amount
of KOH in milligrammes necessary to neutralise the free acid in 1 gramme
of fat or oil.
In the above example:—

5.2 × 5.61
—————= 15.3 acid value.
1.8976

The saponification equivalent is determined by weighing 2-4 grammes of
fat or oil into a wide-necked flask (about 250 c.c. capacity), adding 30 c.c.
neutral alcohol, and warming under a reflux condenser on a steam or water-
bath. When boiling, the flask is disconnected, 50 c.c. of an approximately
semi-normal alcoholic potash solution carefully added from a burette,
together with a few drops of phenol-phthalein solution, and the boiling
under a reflux condenser continued, with frequent agitation, until
saponification is complete (usually from 30-60 minutes) which is indicated

by the absence of fatty globules. The excess of alkali is titrated with N/1
hydrochloric or sulphuric acid.
The value of the approximately N/2 alkali solution is ascertained by taking
50 c.c. together with 30 c.c. neutral alcohol in a similar flask, boiling for the
same length of time as the fat, and titrating with N/1 hydrochloric or
sulphuric acid. The "saponification equivalent" is the amount of fat or oil in
grammes saponified by 1 equivalent or 56.1 grammes of caustic potash.
Example.—1.8976 grammes fat required 18.95 c.c. N/1 acid to neutralise
the unabsorbed alkali.
Fifty c.c. approximately N/2 alcoholic potash solution required 25.6 c.c. N/
acid..
25.6 - 18.95 = 6.65 c.c. N/1 KOH required by fat.

1.8976 × 1000 / 6.65 = 285.3 Saponification Equivalent.
The result of this test is often expressed as the "Saponification Value,"
which is the number of milligrammes of KOH required for the
saponification of 1 gramme of fat. This may be found by dividing 56,100 by
the saponification equivalent or by multiplying the number of c.c. of N/1
alkali absorbed, by 56.1 and dividing by the quantity of fat taken. Thus, in
the above example:—
6.65 × 56.1 / 1.8976 = 196.6 Saponification Value.
The ester or ether value, or number of milligrammes of KOH required for
the saponification of the neutral esters or glycerides in 1 gramme of fat, is
represented by the difference between the saponification and acid values. In
the example given, the ester value would be 196.6 - 15.3 = 181.3.
Unsaponifiable Matter.—The usual method adopted is to saponify about 5
grammes of the fat or oil with 50 c.c. of approximately N/2 alcoholic potash
solution by boiling under a reflux condenser with frequent agitation for
about 1 hour. The solution is then evaporated to dryness in a porcelain basin
over a steam or water-bath, and the resultant soap dissolved in about 200
c.c. hot water. When sufficiently cool, the soap solution is transferred to a
separating funnel, 50 c.c. of ether added, the whole well shaken, and

allowed to rest. The ethereal layer is removed to another separator, more
ether being added to the aqueous soap solution, and again separated. The
two ethereal extracts are then washed with water to deprive them of any
soap, separated, transferred to a flask, and the ether distilled off upon a
water-bath. The residue, dried in the oven at 100° C. until constant, is the
"unsaponifiable matter," which is calculated to per cent. on the oil.
In this method, it is very frequently most difficult to obtain a distinct
separation of ether and aqueous soap solution—an intermediate layer of
emulsion remaining even after prolonged standing, and various expedients
have been recommended to overcome this, such as addition of alcohol
(when petroleum ether is used), glycerine, more ether, water, or caustic
potash solution, or by rotatory agitation.
A better plan is to proceed as in the method above described as far as
dissolving the resulting soap in 200 c.c. water, and then boil for twenty or
thirty minutes. Slightly cool and acidify with dilute sulphuric acid (1 to 3),
boil until the fatty acids are clear, wash with hot water free from mineral
acid, and dry by filtering through a hot water funnel.
Two grammes of the fatty acids are now dissolved in neutral alcohol
saturated with some solvent, preferably a light fraction of benzoline, a
quantity of the solvent added to take up the unsaponifiable matter, and the
whole boiled under a reflux condenser. After cooling, the liquid is titrated
with N/2 aqueous KOH solution, using phenol-phthalein as indicator, this
figure giving the amount of the total fatty acids present. The whole is then
poured into a separating funnel, when separation immediately takes place.
The alcoholic layer is withdrawn, the benzoline washed with warm water
(about 32° C.) followed by neutral alcohol (previously saturated with the
solvent), and transferred to a tared flask, which is attached to a condenser,
and the benzoline distilled off. The last traces of solvent remaining in the
flask are removed by gently warming in the water-oven, and the flask
cooled and weighed, thus giving the amount of unsaponifiable matter.
Constitution of the Unsaponifiable Matter.—Unsaponifiable matter may
consist of cholesterol, phytosterol, solid alcohols (cetyl and ceryl alcohols),
or hydrocarbons (mineral oil). Cholesterol is frequently found in animal
fats, and phytosterol is a very similar substance present in vegetable fats.

Solid alcohols occur naturally in sperm oil, but hydrocarbons, which may
be generally recognised by the fluorescence or bloom they give to the oil,
are not natural constituents of animal or vegetable oils and fats.
The presence of cholesterol and phytosterol may be detected by dissolving a
small portion of the unsaponifiable matter in acetic anhydride, and adding a
drop of the solution to one drop of 50 per cent. sulphuric acid on a spot
plate, when a characteristic blood red to violet coloration is produced. It has
been proposed to differentiate between cholesterol and phytosterol by their
melting points, but it is more reliable to compare the crystalline forms, the
former crystallising in laminæ, while the latter forms groups of needle-
shaped tufts. Another method is to convert the substance into acetate, and
take its melting point, cholesterol acetate melting at 114.3-114.8° C., and
phytosterol acetate at 125.6°-137° C.
Additional tests for cholesterol have been recently proposed by Lifschütz
(Ber. Deut. Chem. Ges., 1908, 252-255), and Golodetz (Chem. Zeit., 1908,
160). In that due to the former, which depends on the oxidation of
cholesterol to oxycholesterol ester and oxycholesterol, a few milligrammes
of the substance are dissolved in 2-3 c.c. glacial acetic acid, a little benzoyl
peroxide added, and the solution boiled, after which four drops of strong
sulphuric acid are added, when a violet-blue or green colour is produced, if
cholesterol is present, the violet colour being due to oxycholesterol ester,
the green to oxycholesterol. Two tests are suggested by Golodetz (1) the
addition of one or two drops of a reagent consisting of five parts of
concentrated sulphuric acid and three parts of formaldehyde solution, which
colours cholesterol a blackish-brown, and (2) the addition of one drop of 30
per cent. formaldehyde solution to a solution of the substance in
trichloracetic acid, when with cholesterol an intense blue coloration is
produced.
Water.—From 5 to 20 grammes of the fat or oil are weighed into a tared
porcelain or platinum dish, and stirred with a thermometer, whilst being
heated over a gas flame at 100° C. until bubbling or cracking has ceased,
and reweighed, the loss in weight representing the water. In cases of
spurting a little added alcohol will carry the water off quietly.

To prevent loss by spurting, Davis (J. Amer. Chem. Soc., 23, 487) has
suggested that the fat or oil should be added to a previously dried and tared
coil of filter paper contained in a stoppered weighing bottle, which is then
placed in the oven and dried at 100° C. until constant in weight. Of course,
this method is not applicable to oils or fats liable to oxidation on heating.
Dregs, Dirt, Adipose Tissue, Fibre, etc.—From 10 to 15 grammes of the fat
are dissolved in petroleum ether with frequent stirring, and passed through a
tared filter paper. The residue retained by the filter paper is washed with
petroleum ether until free from fat, dried in the water-oven at 100° C. and
weighed.
If the amount of residue is large, it may be ignited, and the proportion and
nature of the ash determined.
The amount of impurities may also be estimated by Tate's method, which is
performed by weighing 5 grammes of fat into a separating funnel,
dissolving in ether, and allowing the whole to stand to enable the water to
deposit. After six hours' rest the water is withdrawn, the tube of the
separator carefully dried, and the ethereal solution filtered through a dried
tared filter paper into a tared flask. Well wash the filter with ether, and
carefully dry at 100° C. The ether in the flask is recovered, and the flask
dried until all ether is expelled, and its weight is constant. The amount of fat
in the flask gives the quantity of actual fat in the sample taken; the loss
represents the water and other impurities, and these latter may be obtained
from the increase of weight of the filter paper.
Starch may be detected by the blue coloration it gives with iodine solution,
and confirmed by microscopical examination, or it may be converted into
glucose by inversion, and the glucose estimated by means of Fehling's
solution.
Iodine Absorption.—This determination shows the amount of iodine
absorbed by a fat or oil, and was devised by Hübl, the reagents required
being as follows:—
(1) Solution of 25 grammes iodine in 500 c.c. absolute alcohol; (2) solution
of 30 grammes mercuric chloride in 500 c.c. absolute alcohol, these two
solutions being mixed together and allowed to stand at least twelve hours

before use; (3) a freshly prepared 10 per cent. aqueous solution of
potassium iodide; and (4) a N/10 solution of sodium thiosulphate,
standardised just prior to use by titrating a weighed quantity of resublimed
iodine dissolved in potassium iodide solution.
In the actual determination, 0.2 to 0.5 gramme of fat or fatty acids is
carefully weighed into a well-fitting stoppered 250 c.c. bottle, dissolved in
10 c.c. chloroform, and 25 c.c. of the Hübl reagent added, the stopper being
then moistened with potassium iodide solution and placed firmly in the
bottle, which is allowed to stand at rest in a dark place for four hours. A
blank experiment is also performed, using the same quantities of
chloroform and Hübl reagent, and allowing to stand for the same length of
time.
After the expiration of four hours 20 c.c. of 10 per cent. solution of
potassium iodide and 150 c.c. water are added to the contents of the bottle,
and the excess of iodine titrated with N/10 sodium thiosulphate solution, the
whole being well agitated during the titration, which is finished with starch
paste as indicator. The blank experiment is titrated in the same manner, and
from the amount of thiosulphate required in the blank experiment is
deducted the number of c.c. required by the unabsorbed iodine in the other
bottle; this figure multiplied by the iodine equivalent of 1 c.c. of the
thiosulphate solution and by 100, dividing the product by the weight of fat
taken, gives the "Iodine Number".
Example.—1 c.c. of the N/10 sodium thiosulphate solution is found equal to
0.0126 gramme iodine.
0.3187 gramme of fat taken. Blank requires 48.5 c.c. thiosulphate.
Bottle containing oil requires 40.0 c.c. thiosulphate.
48.5 - 40.0 = 8.5, and the iodine absorption of the fat is—

8.5 × 0.0126 × 100
————————— = 33.6.
0.3187

Wijs showed that by the employment of a solution of iodine monochloride
in glacial acetic acid reliable iodine figures are obtained in a much shorter
time, thirty minutes being sufficient, and this method is now in much more
general use than the Hübl. Wijs' iodine reagent is made by dissolving 13
grammes iodine in 1 litre of glacial acetic acid and passing chlorine into the
solution until the iodine is all converted into iodine monochloride. The
process is carried out in exactly the same way as with the Hübl solution
except that the fat is preferably dissolved in carbon tetrachloride instead of
in chloroform.
Bromine absorption has now been almost entirely superseded by the iodine
absorption, although there are several good methods. The gravimetric
method of Hehner (Analyst, 1895, 49) was employed by one of us for many
years with very good results, whilst the bromine-thermal test of Hehner and
Mitchell (Analyst, 1895, 146) gives rapid and satisfactory results. More
recently MacIlhiney (Jour. Amer. Chem. Soc., 1899, 1084-1089) drew
attention to bromine absorption methods and tried to rewaken interest in
them.
The Refractive index is sometimes useful for discriminating between
various oils and fats, and, in conjunction with other physical and chemical
data, affords another means of detecting adulteration.
Where a great number of samples have to be tested expeditiously, the Abbé
refractometer or the Zeiss butyro-refractometer may be recommended on
account of the ease with which they are manipulated. The most usual
temperature of observations is 60° C.
The Titre or setting point of the fatty acids was devised by Dalican, and is
generally accepted in the commercial valuation of solid fats as a gauge of
firmness, and in the case of tallow has a considerable bearing on the market
value.
One ounce of the fat is melted in a shallow porcelain dish, and 30 c.c. of a
25 per cent. caustic soda solution added, together with 50 c.c. of redistilled
methylated spirit. The whole is stirred down on the water bath until a pasty
soap is obtained, when another 50 c.c. of methylated spirit is added, which
redissolves the soap, and the whole again stirred down to a solid soap. This
is then dissolved in distilled water, a slight excess of dilute sulphuric acid

added to liberate the fatty acids, and the whole warmed until the fatty acids
form a clear liquid on the surface. The water beneath the fatty acids is then
syphoned off, more distilled water added to wash out any trace of mineral
acid remaining, and again syphoned off, this process being repeated until
the washings are no longer acid to litmus paper, when the fatty acids are
poured on to a dry filter paper, which is inserted in a funnel resting on a
beaker, and the latter placed on the water-bath, where it is left until the clear
fatty acids have filtered through.
About 10-15 grammes of the pure fatty acids are now transferred to a test
tube, 6" × 1", warmed until molten, and the tube introduced through a hole
in the cork into a flask or wide-mouthed bottle. A very accurate
thermometer, graduated into fifths of a degree Centigrade (previously
standardised), is immersed in the fatty acids, so that the bulb is as near the
centre as possible, and when the fatty acids just begin to solidify at the
bottom of the tube, the thermometer is stirred round slowly. The mercury
will descend, and stirring is continued until it ceases to fall further, at which
point the thermometer is very carefully observed. It will be found that the
temperature will rise rapidly and finally remain stationary for a short time,
after which it will again begin to drop until the temperature of the room is
reached. The maximum point to which the temperature rises is known as the
"titre" of the sample.

Alkalies and Alkali Salts.

Care should be bestowed upon the sampling of solid caustic soda or potash
as the impurities during the solidification always accumulate in the centre
of the drum, and an excess of that portion must be avoided or the sample
will not be sufficiently representative. The sampling should be performed
expeditiously to prevent carbonating, and portions placed in a stoppered
bottle. The whole should be slightly broken in a mortar, and bright
crystalline portions taken for analysis, using a stoppered weighing bottle.
Caustic Soda and Caustic Potash.—These substances are valued according
to the alkali present in the form of caustic (hydrate) and carbonate.
About 2 grammes of the sample are dissolved in 50 c.c. distilled water, and
titrated with N/1 sulphuric acid, using phenol-phthalein as indicator, the

alkalinity so obtained representing all the caustic alkali and one-half the
carbonate, which latter is converted into bicarbonate. One c.c. N/1 acid =
0.031 gramme Na2O or 0.040 gramme NaOH and 0.047 gramme K2O, or
0.056 gramme KOH.
After this first titration, the second half of the carbonate may be determined
in one of two ways, either:—
(1) By adding from 3-5 c.c. of N/10 acid, and well boiling for five minutes
to expel carbonic-acid gas, after which the excess of acid is titrated with
N/10 soda solution; or
(2) After adding two drops of methyl orange solution, N/10 acid is run in
until the solution acquires a faint pink tint.
In the calculation of the caustic alkali, the number of c.c. of acid required in
the second titration, divided by 10, is subtracted from that used in the first,
and this difference multiplied by 0.031, or 0.047 gives the amount of Na2O
or K2O respectively in the weight of sample taken, whence the percentage
may be readily calculated.
The proportion of carbonate is calculated by multiplying the amount of
N/10 acid required in the second titration by 2, and then by either 0.0031 or
0.0047 to give the amount of carbonate present, expressed as Na2O or K2O
respectively.
An alternative method is to determine the alkalinity before and after the
elimination of carbonate by chloride of barium.
About 7-8 grammes of the sample are dissolved in water, and made up to
100 c.c., and the total alkalinity determined by titrating 20 c.c. with N/1
acid, using methyl orange as indicator. To another 20 c.c. is added barium
chloride solution (10 per cent.) until it ceases to give a precipitate, the
precipitate allowed to settle, and the clear supernatant liquid decanted off,
the precipitate transferred to a filter paper and well washed, and the filtrate
titrated with N/1 acid, using phenol-phthalein as indicator. The second
titration gives the amount of caustic alkali present, and the difference
between the two the proportion of carbonate.

When methyl orange solution is used as indicator, titrations must be carried
out cold.
Reference has already been made (p. 39) to the manner in which the alkali
percentage is expressed in English degrees in the case of caustic soda.
Chlorides are estimated by titrating the neutral solution with N/10 silver
nitrate solution, potassium chromate being used as indicator. One c.c. N/10
AgNO3 solution = 0.00585 gramme sodium chloride.

The amount of acid necessary for exact neutralisation having already been
ascertained, it is recommended to use the equivalent quantity of N/10 nitric
acid to produce the neutral solution.
Sulphides may be tested for, qualitatively, with lead acetate solution.
Aluminates are determined gravimetrically in the usual manner; 2 grammes
are dissolved in water, rendered acid with HCl, excess of ammonia added,
and the gelatinous precipitate of aluminium hydrate collected on a filter
paper, washed, burnt, and weighed.

Carbonated Alkali (Soda Ash).—The total or available alkali is, of course,
the chief factor to be ascertained, and for this purpose it is convenient to
weigh out 3.1 grammes of the sample, dissolve in 50 c.c. water, and titrate
with N/1 sulphuric or hydrochloric acid, using methyl orange as indicator.
Each c.c. of N/1 acid required represents 1 per cent. Na2O in the sample
under examination.
A more complete analysis of soda ash would comprise:—
Insoluble matter, remaining after 10 grammes are dissolved in warm water.
This is washed on to a filter-paper, dried, ignited, and weighed.
The filtrate is made up to 200 c.c., and in it may be determined:—
Caustic soda, by titrating with N/1 acid the filtrate resulting from the
treatment of 20 c.c. (equal to 1 gramme) with barium chloride solution.

Carbonate.—Titrate 20 c.c. with N/1 acid, and deduct the amount of acid
required for the Caustic.
Chlorides.—Twenty c.c. are exactly neutralised with nitric acid, titrated
with N/10 AgNO3 solution, using potassium chromate as indicator.

Sulphates.—Twenty c.c. are acidulated with HCl, and the sulphates
precipitated with barium chloride; the precipitate is collected on a filter
paper, washed, dried, ignited, and weighed, the result being calculated to
Na2SO4.

Sulphides and Sulphites.—The presence of these compounds is denoted by
the evolution of sulphuretted hydrogen and sulphurous acid respectively
when the sample is acidulated. Sulphides may also be tested for,
qualitatively, with lead acetate solution, or test-paper of sodium nitro-
prusside.
The total quantity of these compounds may be ascertained by acidulating
with acetic acid, and titrating with N/10 iodine solution, using starch paste
as indicator. One c.c. N/10 iodine solution = 0.0063 gramme Na2SO3.

The amount of sulphides may be estimated by titrating the hot soda
solution, to which ammonia has been added, with an ammoniacal silver
nitrate solution, 1 c.c. of which corresponds to 0.005 gramme Na2S. As the
titration proceeds, the precipitate is filtered off, and the addition of
ammoniacal silver solution to the filtrate continued until a drop produces
only a slight opacity. The presence of chloride, sulphate, hydrate, or
carbonate does not interfere with the accuracy of this method. The
ammoniacal silver nitrate solution is prepared by dissolving 13.345
grammes of pure silver in pure nitric acid, adding 250 c.c. liquor ammoniæ
fortis, and diluting to 1 litre.
Carbonate of Potash (Pearl Ash).—The total or available alkali may be
estimated by taking 6.9 grammes of the sample, and titrating with N/1 acid
directly, or adding 100 c.c. N/1 sulphuric acid, boiling for a few minutes,
and titrating the excess of acid with N/1 caustic soda solution, using litmus
as indicator. In this case each c.c. N/1 acid required, is equivalent, in the
absence of Na2CO3, to 1 per cent. K2CO3.

Carbonate of potash may be further examined for the following:—
Moisture.—From 2-3 grammes are heated for thirty minutes in a crucible
over a gas flame, and weighed when cold, the loss in weight representing
the moisture.
Insoluble residue, remaining after solution in water, filtering and well
washing.
Potassium may be determined by precipitation as potassium platino-
chloride thus:—Dissolve 0.5 gramme in a small quantity (say 10 c.c.) of
water, and carefully acidulate with hydrochloric acid, evaporate the
resultant liquor to dryness in a tared platinum basin, and heat the residue
gradually to dull redness. Cool in a desicator, weigh, and express the result
as "mixed chlorides," i.e. chlorides of soda and potash. To the mixed
chlorides add 10 c.c. water, and platinic chloride in excess (the quantity
may be three times the amount of the mixed chlorides) and evaporate nearly
to dryness; add 15 c.c. alcohol and allow to stand three hours covered with
a watch-glass, giving the dish a gentle rotatory movement occasionally. The
clear liquid is decanted through a tared filter, and the precipitate well
washed with alcohol by decantation, and finally transferred to the filter,
dried and weighed. From the weight of potassium platino-chloride, K2PtCl6,
is calculated the amount of potassium oxide K2O by the use of the factor
94/488.2 or 0.19254.
Chlorides, determined with N/10 silver nitrate solution, and calculated to
KCl.
Sulphates, estimated as barium sulphate, and calculated to K2SO4.

Sodium Carbonate, found by deducting the K2CO3 corresponding to the
actual potassium as determined above, from the total alkali.
Iron, precipitated with excess of ammonia, filtered, ignited, and weighed as
Fe2O3.

Sodium Chloride (Common Salt).

This should be examined for the following:—

Actual Chloride, either titrated with N/10 silver nitrate solution, using
neutral potassium chromate solution as indicator, or, preferably, estimated
gravimetrically as silver chloride by precipitation with silver nitrate
solution, the precipitate transferred to a tared filter paper, washed, dried and
weighed.
Insoluble matter, remaining on dissolving 5 grammes in water, and
filtering. This is washed, dried, ignited and weighed.
Moisture.—5 grammes are weighed into a platinum crucible, and heat
gently applied. The temperature is gradually increased to a dull red heat,
which is maintained for a few minutes, the dish cooled in a desicator, and
weighed.
Sulphates are estimated by precipitation as barium sulphate and calculated
to Na2SO4.

Sodium.—This may be determined by converting the salt into sodium
sulphate by the action of concentrated sulphuric acid, igniting to drive off
hydrochloric and sulphuric acids, and fusing the mass until constant in
weight, weighing finally as Na2SO4.

Potassium Chloride.

This should be examined, in the same way as sodium chloride, for chloride,
insoluble matter, moisture, and sulphate. The potassium may be determined
as potassium platino-chloride, as described under carbonate of potash.

Silicates of Soda and Potash.

The most important determinations for these are total alkali and silica.
Total alkali is estimated by dissolving 2 grammes in distilled water, and
titrating when cold, with N/1 acid, using methyl orange as indicator.
Silica may be determined by dissolving 1 gramme in distilled water,
rendering the solution acid with HCl, and evaporating to complete dryness
on the water-bath, after which the residue is moistened with HCl and again
evaporated, this operation being repeated a third time. The residue is then

heated to about 150° C., extracted with hot dilute HCl, filtered, thoroughly
washed, dried, ignited in a tared platinum crucible, and weighed as SiO2.

Essential Oils.

As already stated, these are very liable to adulteration, and an examination
of all kinds of oil is desirable, while in the case of the more expensive
varieties it should never be omitted.
Specific Gravity.—As with fats and oils, this is usually taken at 15° C., and
compared with water at the same temperature. In the case of otto of rose
and guaiac wood oil, however, which are solid at this temperature, it is
generally observed at 30° C. compared with water at 15° C.
The specific gravity is preferably taken in a bottle or U-tube, but if
sufficient of the oil is available and a high degree of accuracy is not
necessary, it may be taken either with a Westphal balance, or by means of a
hydrometer.
Optical Rotation.—For this purpose a special instrument, known as a
polarimeter, is required, details of the construction and use of which would
be out of place here. Suffice it to mention that temperature plays an
important part in the determination of the optical activity of certain essential
oils, notably in the case of lemon and orange oils. For these Gildemeister
and Hoffmann give the following corrections:—
Lemon oil, below 20° C. subtract 9' for each degree below, above 20° C.
add 8' for each degree above.
Orange oil, below 20° C. subtract 14' for each degree below, above 20° C.
add 13' for each degree above.
Refractive Index.—This figure is occasionally useful, and is best
determined with an Abbé refractometer, at 20° C.
Solubility in Alcohol.—This is found by running alcohol of the requisite
strength from a burette into a measured volume of the oil with constant
agitation, until the oil forms a clear solution with the alcohol. Having noted

the quantity of alcohol added, it is well to run in a small further quantity of
alcohol, and observe whether any opalescence or cloudiness appears.
Acid, ester, and saponification values are determined exactly as described
under fats and oils. Instead of expressing the result as saponification value
or number, the percentage of ester, calculated in the form of the most
important ester present, may be obtained by multiplying the number of c.c.
of N/1 alkali absorbed in the saponification by the molecular weight of the
ester. Thus, to find the percentage as linalyl acetate, the number of c.c.
absorbed would be multiplied by 0.196 and by 100, and divided by the
weight of oil taken.
Alcohols.—For the estimation of these, if the oil contains much ester it must
first be saponified with alcoholic potash, to liberate the combined alcohols,
and after neutralising the excess of alkali with acid, the oil is washed into a
separating funnel with water, separated, dried with anhydrous sodium
sulphate, and is then ready for the alcohol determination.
If there is only a small quantity of ester present, this preliminary
saponification is unnecessary.
The alcohols are estimated by conversion into their acetic esters, which are
then saponified with standard alcoholic potash, thereby furnishing a
measure of the amount of alcohol esterified.
Ten c.c. of the oil is placed in a flask with an equal volume of acetic
anhydride, and 2 grammes of anhydrous sodium acetate, and gently boiled
for an hour to an hour and a half. After cooling, water is added, and the
contents of the flask heated on the water-bath for fifteen to thirty minutes,
after which they are cooled, transferred to a separating funnel, and washed
with a brine solution until the washings cease to give an acid reaction with
litmus paper. The oil is now dried with anhydrous sodium sulphate, filtered,
and 1-2 grammes weighed into a flask and saponified with alcoholic potash
as in the determination of ester or saponification value.
The calculation is a little complicated, but an example may perhaps serve to
make it clear.
A geranium oil containing 26.9 per cent. of ester, calculated as geranyl
tiglate, was acetylated, after saponification, to liberate the combined

geraniol, and 2.3825 grammes of the acetylated oil required 9.1 c.c. of N/1
alkali for its saponification.
Now every 196 grammes of geranyl acetate present in the acetylated oil
correspond to 154 grammes of geraniol, so that for every 196 grammes of
ester now present in the oil, 42 grammes have been added to its weight, and
it is therefore necessary to make a deduction from the weight of oil taken
for the final saponification to allow for this, and since each c.c. of N/1 alkali
absorbed corresponds to 0.196 gramme of geranyl acetate, the amount to be
deducted is found by multiplying the number of c.c. absorbed by 0.042
gramme, the formula for the estimation of total alcohols thus becoming in
the example given:—

9.1 × 0.154 × 100
Per cent. of geraniol = ———————— = 70.2
2.3825 - (9.1 × 0.042)

The percentage of combined alcohols can be calculated from the amount of
ester found, and by subtracting this from the percentage of total alcohols,
that of the free alcohols is obtained.
In the example quoted, the ester corresponds to 17.6 per cent. geraniol, and
this, deducted from the total alcohols, gives 52.6 per cent. free alcohols,
calculated as geraniol.
This process gives accurate results with geraniol, borneol, and menthol, but
with linalol and terpineol the figures obtained are only comparative, a
considerable quantity of these alcohols being decomposed during the
acetylation. The aldehyde citronellal is converted by acetic anhydride into
isopulegol acetate, so that this is also included in the determination of
graniol in citronella oil.
Phenols.—These bodies are soluble in alkalies, and may be estimated by
measuring 5 c.c. or 10 c.c. of the oil into a Hirschsohn flask (a flask of
about 100 c.c. capacity with a long narrow neck holding 10 c.c., graduated
in tenths of a c.c.), adding 25 c.c. of a 5 per cent. aqueous caustic potash
solution, and warming in the water-bath, then adding another 25 c.c., and
after one hour in the water-bath filling the flask with the potash solution
until the unabsorbed oil rises into the neck of the flask, the volume of this

oil being read off when it has cooled down to the temperature of the
laboratory. From the volume of oil dissolved the percentage of phenols is
readily calculated.
Aldehydes.—In the estimation of these substances, use is made of their
property of combining with sodium bisulphite to form compounds soluble
in hot water. From 5-10 c.c. of the oil is measured into a Hirschsohn flask,
about 30 c.c. of a hot saturated solution of sodium bisulphite added, and the
flask immersed in a boiling water bath, and thoroughly shaken at frequent
intervals. Further quantities of the bisulphite solution are gradually added,
until, after about one hour, the unabsorbed oil rises into the neck of the
flask, where, after cooling, its volume is read off, and the percentage of
absorbed oil, or aldehydes, calculated.
In the case of lemon oil, where the proportion of aldehydes, though of great
importance, is relatively very small, it is necessary to first concentrate the
aldehydes before determining them. For this purpose, 100 c.c. of the oil is
placed in a Ladenburg fractional distillation flask, and 90 c.c. distilled off
under a pressure of not more than 40 mm., and the residue steam distilled.
The oil so obtained is separated from the condensed water, measured, dried,
and 5 c.c. assayed for aldehydes either by the process already described, or
by the following process devised by Burgess (Analyst, 1904, 78):—
Five c.c. of the oil are placed in the Hirschsohn flask, about 20 c.c. of a
saturated solution of neutral sodium sulphite added, together with a few
drops of rosolic acid solution as indicator, and the flask placed in a boiling
water-bath and continually agitated. The contents of the flask soon become
red owing to the liberation of free alkali by the combination of the aldehyde
with part of the sodium sulphite, and this coloration is just discharged by
the addition of sufficient 10 per cent. acetic-acid solution. The flask is again
placed in the water-bath, the shaking continued, and any further alkali
liberated neutralised by more acetic acid, the process being continued in
this way until no further red colour is produced. The flask is then filled with
the sodium sulphite solution, the volume of the cooled unabsorbed oil read
off, and the percentage of aldehydes calculated as before.
Solidifying Point, or Congealing Point.—This is of some importance in the
examination of anise and fennel oils, and is also useful in the examination

of otto of rose. A suitable apparatus may be made by obtaining three test
tubes, of different sizes, which will fit one inside the other, and fixing them
together in this way through corks. The innermost tube is then filled with
the oil, and a sensitive thermometer, similar to that described under the Titre
test for fats, suspended with its bulb completely immersed in the oil. With
anise and fennel, the oil is cooled down with constant stirring until it just
starts crystallising, when the stirring is interrupted, and the maximum
temperature to which the mercury rises noted. This is the solidifying point.
In the case of otto of rose, the otto is continually stirred, and the point at
which the first crystal is observed is usually regarded as the congealing
point.
Melting Point.—This is best determined by melting some of the solid oil, or
crystals, and sucking a small quantity up into a capillary tube, which is then
attached by a rubber band to the bulb of the thermometer, immersed in a
suitable bath (water, glycerine, oil, etc.) and the temperature of the bath
gradually raised until the substance in the tube is sufficiently melted to rise
to the surface, the temperature at which this takes place being the melting
point.
The melting point of otto of rose is usually taken in a similar tube to the
setting point, and is considered to be the point at which the last crystal
disappears.
Iodine Absorption.—In the authors' opinion, this is of some value in
conjunction with other data in judging of the purity of otto of rose. It is
determined by Hübl's process as described under Fats and Oils, except that
only 0.1 to 0.2 gramme is taken, and instead of 10 c.c. of chloroform, 10
c.c. of pure alcohol are added. The rest of the process is identical.

Soap.

In the analysis of soap, it is a matter of considerable importance that all the
determinations should be made on a uniform and average sample of the
soap, otherwise very misleading and unreliable figures are obtained. Soap
very rapidly loses its moisture on the surface, while the interior of the bar or
cake may be comparatively moist, and the best way is to carefully remove

the outer edges and take the portions for analysis from the centre. In the
case of a household or unmilled toilet soap, it is imperative that the
quantities for analysis should all be weighed out as quickly after each other
as possible.
Fatty Acids.—Five grammes of the soap are rapidly weighed into a small
beaker, distilled water added, and the beaker heated on the water bath until
the soap is dissolved.
A slight excess of mineral acid is now added, and the whole heated until the
separated fatty acids are perfectly clear, when they are collected on a tared
filter paper, well washed with hot water and dried until constant in weight.
The result multiplied by 20 gives the percentage of fatty acids in the
sample.
A quicker method, and one which gives accurate results when care is
bestowed upon it, is to proceed in the manner described above as far as the
decomposition with mineral acid, and to then add 5 or 10 grammes of
stearic acid or beeswax to the contents of the beaker and heat until a clear
layer of fatty matter collects upon the acid liquor.
Cool the beaker, and when the cake is sufficiently hard, remove it carefully
by means of a spatula and dry on a filtering paper, add the portions adhering
to the sides of the beaker to the cake, and weigh.
The weight, less the amount of stearic acid or beeswax added, multiplied by
20 gives the percentage of fatty acids.
Care must be taken that the cake does not contain enclosed water.
The results of these methods are returned as fatty acids, but are in reality
insoluble fatty acids, the soluble fatty acids being generally disregarded.
However in soaps made from cocoa-nut and palm-kernel oils (which
contain an appreciable quantity of soluble fatty acids) the acid liquor is
shaken with ether, and, after evaporation of the ethereal extract, the amount
of fatty matter left is added to the result already obtained as above, or the
ether method described below may be advantageously employed.
Where the soap under examination contains mineral matter, the separated
fatty acids may be dissolved in ether. This is best performed in an

elongated, graduated, stoppered tube, the total volume of the ether, after
subsidence, carefully read, and an aliquot part taken and evaporated to
dryness in a tared flask, which is placed in the oven at 100° C. until the
weight is constant.
In a complete analysis, the figure for fatty acids should be converted into
terms of fatty anhydrides by multiplying by the factor 0.9875.
In this test the resin acids contained in the soap are returned as fatty acids,
but the former can be estimated, as described later, and deducted from the
total.
Total Alkali.—The best method is to incinerate 5 grammes of the soap in a
platinum dish, dissolve the residue in water, boil and filter, making the
volume of filtrate up to 250 c.c., the solution being reserved for the
subsequent determination of salt, silicates, and sulphates, as detailed below.
Fifty c.c. of the solution are titrated with N/1 acid, to methyl orange, and
the result expressed in terms of Na2O.

Number of c.c. required × 0.031 × 100 = per cent. Na2O.

The total alkali may also be estimated in the filtrate from the determination
of fatty acids, if the acid used for decomposing the soap solution has been
measured and its strength known, by titrating back the excess of acid with
normal soda solution, when the difference will equal the amount of total
alkali in the quantity taken.
The total alkali is usually expressed in the case of hard soaps as Na2O, and
in soft soaps as K2O.

Free caustic alkali is estimated by dissolving 2 grammes of the soap, in
neutral pure alcohol, with gentle heat, filtering, well washing the filter with
hot neutral spirit, and titrating the filtrate with N/10 acid, to phenol-
phthalein.
Number of c.c. required × 0.0031 × 50 = per cent. free alkali Na2O, as
caustic.

Free Carbonated Alkali.—The residue on the filter paper from the above
determination is washed with hot water, and the aqueous filtrate titrated
with N/10 acid, using methyl orange as indicator. The result is generally
expressed in terms of Na2O.

Number of c.c. required × 0.0031 × 50 = per cent. free alkali Na2O, as
carbonate.
Free Alkali.—Some analysts determine the alkalinity to phenol-phthalein of
the alcoholic soap solution without filtering, and express it as free alkali
(caustic, carbonates, or any salt having an alkaline reaction).
Combined Alkali.—The difference between total alkali and free alkali
(caustic and carbonate together) represents the alkali combined with fatty
acids. This figure may also be directly determined by titrating, with N/2
acid, the alcoholic solution of soap after the free caustic estimation, using
lacmoid as indicator.
The potash and soda in soaps may be separated by the method described for
the estimation of potassium in Pearl ash (page 126).
The potassium platino-chloride (K2PtCl6) is calculated to potassium
chloride (KCl) by using the factor 0.3052, and this figure deducted from the
amount of mixed chlorides found, gives the amount of sodium chloride
(NaCl), from which the sodium oxide (Na2O) is obtained by multiplying by
0.52991.
The potassium chloride (KCl) is converted into terms of potassium oxide
(K2O) by the use of the factor 0.63087.

Salt may be determined in 50 c.c. of the filtered aqueous extract of the
incinerated soap, by exactly neutralising with normal acid and titrating with
N/10 silver nitrate solution, using a neutral solution of potassium chromate
as indicator. The final reaction is more distinctly observed if a little
bicarbonate of soda is added to the solution.
Number of c.c. required × 0.00585 × 100 = per cent. of common salt, NaCl.

Chlorides may also be estimated by Volhard's method, the aqueous extract
being rendered slightly acid with nitric acid, a measured volume of N/10
silver nitrate solution added, and the excess titrated back with N/10
ammonium thiocyanate solution, using iron alum as indicator.
Silicates.—These are estimated by evaporating 50 c.c. of the filtered extract
from the incinerated soap, in a platinum dish with hydrochloric acid twice
to complete dryness, heating to 150° C., adding hot water, and filtering
through a tared filter paper.
The residue is well washed, ignited, and weighed as SiO2, and from this
silica is calculated the sodium silicate.
Sulphates may be determined in the filtrate from the silica estimation by
precipitation with barium chloride solution, and weighing the barium
sulphate, after filtering, and burning, expressing the result in terms of
Na2SO4 by the use of the factor 0.6094.

Moisture.—This is simply estimated by taking a weighed portion in small
shavings in a tared dish, and drying in the oven at 105° C. until it ceases to
lose weight. From the loss thus found is calculated the moisture percentage.
Free or Uncombined Fat.—This is usually determined by repeated
extraction of an aqueous solution of the soap with petroleum ether; the
ethereal solution, after washing with water to remove traces of soap, is
evaporated to dryness and the residue weighed.
A good method, which can be recommended for employment where many
determinations have to be performed, is to dissolve 10 grammes of soap in
50 c.c. neutral alcohol and titrate to phenol-phthalein with N/1 acid. Add 3-
5 drops HCl and boil to expel carbonic acid, neutralise with alcoholic KOH
solution and add exactly 10 c.c. in excess, boil for fifteen minutes under a
reflux condenser and titrate with N/1 acid. The difference between this
latter figure and the amount required for a blank test with 10 c.c. alcoholic
KOH, denotes the amount of alkali absorbed by the uncombined fat.
Examination of the fatty acids as a guide to the probable composition of the
soap:—

From the data obtained by estimating the "titre," iodine number, and
saponification equivalent of the mixed fatty and rosin acids, and the rosin
content, a fairly good idea of the constitution of the soap may be deduced.
The titre, iodine number, and saponification equivalent are determined in
exactly the same manner as described under Fats and Oils.
The presence of rosin may be detected by the Liebermann-Storch reaction,
which consists in dissolving a small quantity of the fatty acids in acetic
anhydride, and adding to a few drops of this solution 1 drop of 50 per cent.
sulphuric acid. A violet coloration is produced with rosin acids. The amount
of rosin may be estimated by the method devised by Twitchell (Journ. Soc.
Chem. Ind., 1891, 804) which is carried out thus:—
Two grammes of the mixed fatty and rosin acids are dissolved in 20 c.c.
absolute alcohol, and dry hydrochloric acid gas passed through until no
more is absorbed, the flask being kept cool by means of cold water to
prevent the rosin acids being acted upon. The flask, after disconnecting, is
allowed to stand one hour to ensure complete combination, when its
contents are transferred to a Philips' beaker, well washed out with water so
that the volume is increased about five times, and boiled until the acid
solution is clear, a fragment of granulated zinc being added to prevent
bumping. The heat is removed, and the liquid allowed to cool, when it is
poured into a separator, and the beaker thoroughly rinsed out with ether.
After shaking, the acid liquor is withdrawn, and the ethereal layer washed
with water until free from acid. Fifty c.c. neutral alcohol are added, and the
solution titrated with N/1 KOH or NaOH solution, the percentage of rosin
being calculated from its combining weight. Twitchell suggests 346 as the
combining weight of rosin, but 330 is a closer approximation.
The method may be also carried out gravimetrically, in which case
petroleum ether, boiling at 74° C. is used for washing out the beaker into
the separator. The acid liquor is run off, and the petroleum ether layer
washed first with water and then with a solution of 1/2 gramme KOH and 5
c.c. alcohol in 50 c.c. water, and agitated. The rosin is thus saponified and
separated. The resinate solution is withdrawn, acidified, and the resin acids
collected, dried and weighed.

Halphen's Reaction.—This is a special test to determine the presence or
absence of cotton-seed oil fatty acids in mixtures. Equal parts of the fatty
acids, amyl alcohol, and a 1 per cent. solution of sulphur in carbon
bisulphide, are heated in a test-tube placed in a water-bath until
effervescence ceases, then in boiling brine for one hour or longer when only
small quantities are present. The presence of cotton-seed oil is denoted by a
pink coloration. The reaction is rendered much more rapid, according to
Rupp (Z. Untersuch. Nahr. Genussm., 1907, 13, 74), by heating in a
stoppered flask.
Other bodies which it is occasionally necessary to test for or determine in
soap include:—
Carbolic acid.—Fifty grammes of the soap are dissolved in water and 20
c.c. of 10 per cent. caustic potash added. The solution is treated with an
excess of brine, the supernatant liquor separated, and the precipitate washed
with brine, the washings being added to the liquor withdrawn. This is then
evaporated to a small bulk, placed in a Muter's graduated tube, and acidified
with mineral acid.
The volume of separated phenols is observed and stated in percentage on
the soap taken.
Or the alkaline layer may be rendered acid and steam distilled; the distillate
is made up to a known volume, and a portion titrated by the Koppeschaar
method with standard bromine water.
Glycerine.—Five grammes of soap are dissolved in water, decomposed
with dilute sulphuric acid, and the clear fatty acids filtered and washed. The
filtrate is neutralised with barium carbonate, evaporated to 50 c.c., and the
glycerol estimated by the bichromate method detailed under Crude
Glycerine.
Starch or gum may be detected by dissolving the soap in alcohol, filtering,
and examining the residue on the filter paper. Starch is readily recognised
by the blue coloration it gives with a solution of iodine in potassium iodide.
Sugars are tested for by means of Fehlings' solution, in the liquor separated
from the fatty acids, after first boiling with dilute acid to invert any cane
sugar.

Mercury will be revealed by a black precipitate produced when sulphuretted
hydrogen is added to the liquor separated from the fatty acids, and may be
estimated by filtering off this precipitate on a tared Gooch's crucible, which
is then dried and weighed.
Borax or borates are tested for in the residue insoluble in alcohol. This is
dissolved in water, rendered faintly acid with dilute hydrochloric acid, and a
strip of turmeric paper immersed for a few minutes in the liquid. This is
then dried in the water-oven, when if any boric acid compound is present, a
bright reddish-pink stain is produced on the paper, which is turned blue on
moistening with dilute alkali.
The amount of the boric acid radicle may be determined by incinerating 5-
10 grammes of soap, extracting with hot dilute acid, filtering, neutralising
this solution to methyl orange, and boiling to expel carbon dioxide. After
cooling, sufficient pure neutralised glycerine is added to form one-third of
the total volume, and the liquid titrated with N/2 caustic soda solution,
using phenol-phthalein as indicator. Each c.c. of N/2 NaOH solution
corresponds to 0.031 gramme crystallised boric acid, H3BO3 or 0.0477
gramme crystallised borax, Na2B4O7·10H2O.

Lyes.

The amounts of caustic alkali (if any), carbonated alkali, and salt present
are determined in the manner already described under Alkali and Alkali
Salts. The glycerol content is ascertained by taking 2.5 grammes, adding
lead subacetate solution, and filtering without increasing the bulk more than
is absolutely necessary; the solution is concentrated to about 25 c.c., and the
oxidation with bichromate and sulphuric acid conducted as described in the
examination of Crude Glycerine. The solution, after oxidation, is made up
to 250 c.c., and titrated against standard ferrous ammonium sulphate
solution, the formula for the calculation being:—

Per cent. of glycerol = (0.25 - (2.5/n)) × 40

where n equals the number of c.c. of oxidised lyes required to oxidise the
ferrous ammonium sulphate solution.

The estimation of actual glycerol in this is necessarily a matter of
considerable importance, and a very large number of processes, which are
constantly being added to, have been suggested for the purpose. Hitherto,
however, only two methods have been generally adopted, viz. the acetin and
the bichromate processes. Unfortunately the results obtained by these do not
invariably agree, the latter, which includes all oxidisable matter as glycerol,
giving sometimes considerably higher results, and it has been suggested that
a determination should be made by both methods, and the average of the
two results considered the true value. This involves a considerable amount
of time and trouble, and it will generally be found sufficient in a works
laboratory to determine the glycerol by one method only in the ordinary
course, reserving the other process for use as a check in case of dispute or
doubt.
Acetin Method.—This consists in converting the glycerol into its ester with
acetic acid, the acetic triglyceride, or triacetin being formed. This is then
saponified with a known volume of standard alkali, the excess of which is
titrated with acid, and the percentage of glycerol calculated from the
amount of alkali absorbed.
From 1 to 1.5 grammes of the glycerine is weighed into a conical flask of
about 150 c.c. capacity, 7 or 8 c.c. of acetic anhydride added, together with
about 3 grammes of anhydrous sodium acetate, and the whole boiled on a
sand-bath under a reflux condenser for one to one and a half hours, after
which it is allowed to cool, 50 c.c. water added, and the ester dissolved by
shaking, and gently warming, the reflux condenser still being attached as
the acetin is very volatile. The solution is then filtered from a white
flocculent precipitate, which contains most of the impurities, into a larger
conical flask, of some 500-600 c.c. capacity, and after cooling, rendered just
neutral to phenol-phthalein by means of N/2 caustic soda solution, the exact
point being reached when the solution acquires a reddish-yellow tint; 25 c.c.
of a strong caustic soda solution is then added, and the liquid boiled for
about fifteen minutes, the excess of alkali being titrated after cooling, with
N/1 or N/2 hydrochloric acid. A blank experiment is carried out
simultaneously, with another 25 c.c. of the soda solution, and the difference
in the amounts of acid required by the two, furnishes a measure of the alkali
required to saponify the acetin formed, and hence the amount of glycerol in
the crude glycerine may be calculated.

Example.—1.4367 grammes crude glycerine, after treatment with acetic
anhydride, and neutralising, was saponified with 25 c.c. of a 10 per cent.
caustic soda solution.

The blank experiment required 111.05 c.c. N/1hydrochloric acid.
Flask containing acetin " 75.3 c.c. " "
——
35.75 c.c. " "

Hence, the acetin formed from the glycerol present in 1.4367 grammes of
the crude glycerine required 35.75 c.c. N/1 caustic alkali for its
saponification, so that the percentage of glycerol may be calculated from
the following formula:—

35.75 × 0.03067 × 100
Per cent. glycerol = ——————— = 76.3.
1.4367

Bichromate Method.—This process was originally devised by Hehner
(Journ. Soc. Chem. Ind., 1889, 4-9), but the modification suggested by
Richardson and Jaffe (ibid., 1898, 330) is preferred by the authors, and has
been practised by them for several years with perfectly satisfactory results.
Twenty-five grammes of the crude glycerine are weighed out in a beaker,
washed into a 250 c.c. stoppered flask, and made up to the graduation mark
with water. Twenty-five c.c. of this solution are then measured from a
burette into a small beaker, a slight excess of basic lead acetate solution
added to precipitate organic matter, the precipitate allowed to settle, and the
supernatant liquid poured through a filter paper into another 250 c.c. flask.
The precipitate is washed by decantation until the flask is nearly full, then
transferred to the filter, and allowed to drain, a few drops of dilute sulphuric
acid being added to precipitate the slight excess of basic lead acetate
solution, and the contents of the flask made up with water to 250 c.c. This
solution is filtered, 20 c.c. measured from a burette into a conical flask of
about 150 c.c. capacity, 25 c.c. of a standard potassium bichromate solution
containing 74.86 grammes bichromate per litre added, together with 50 c.c.
of 50 per cent. sulphuric acid, and the whole placed in a boiling water-bath
for one hour, after which it is allowed to cool, diluted with water to 250 c.c.,

and this solution run in to 20 c.c. of a 3 per cent. ferrous ammonium
sulphate solution until the latter is completely oxidised, as shown by no
blue coloration being produced when one drop is brought into contact with
one drop of a freshly prepared solution of potassium ferricyanide on a spot-
plate. The ferrous ammonium sulphate solution is previously standardised
by titration with a potassium bichromate solution of one-tenth the above
strength, made by diluting 10 c.c. of the strong solution to 100 c.c. with
water.
The reaction taking place in the oxidation may be represented by the
equation:—
3C3H5(OH)3 + 7K2Cr2O7 + 28H2SO4 = 9CO2 + 40H2O +
7K2SO4 + 7Cr2(SO4)3.

Now the strong potassium bichromate solution above mentioned is of such
a strength that 1 c.c. will oxidise 0.01 gramme glycerine, and 20 c.c. of the
ferrous ammonium sulphate solution should require about 10 c.c. of the
one-tenth strength bichromate in the blank experiment. If it requires more
or less than this, then the amount of ferrous ammonium sulphate solution
which would require exactly 10 c.c. (corresponding to 0.01 gramme
glycerine) is calculated, and the oxidised glycerine solution run into this
until oxidation is complete.
The formula for the calculation of the percentage of glycerol then becomes:
—

Per cent. of glycerol = (0.25 -((250 × 0.01)/n)) × 500,

where n equals the number of c.c. of oxidised glycerine solution required to
oxidise the ferrous ammonium sulphate solution.
Example:—
In the blank experiment 20 c.c. ferrous ammonium sulphate solution
required 9.8 c.c. one-tenth strength bichromate solution, so that 20.4 c.c.
ferrous solution would equal 10 c.c. bichromate.

20.4 c.c. ferrous solution required 27.8 c.c. of oxidised glycerine solution
before it ceased to give a blue coloration with potassium ferricyanide.

Therefore, per cent. of glycerol = (0.25 -((250 × 0.01)/27.8)) × 500,
= 80.04 per cent.

Other methods have been suggested for the preliminary purification, e.g.,
silver oxide, silver carbonate and lead subacetate, and copper sulphate and
caustic potash, but the lead subacetate alone with care gives satisfactory
results.
Other determinations include those of specific gravity, alkalinity, proportion
of salts and chloride, and tests for metals, arsenic, sulphur compounds,
sugar, and fatty acids.
Specific gravity is determined at 15° C., and may be taken in specific
gravity bottle, or with a Westphal balance or hydrometer It usually ranges
from 1.3 to 1.31.
Alkalinity, which is usually sodium carbonate, and may be somewhat
considerable if the soap has been grained with caustic alkali, is determined
after dilution with water by titrating with N/2 acid, using methyl orange as
indicator.
Salts.—These may be determined by gently incinerating 5-6 grammes of
the glycerine, extracting the carbonaceous mass with distilled water,
filtering, and evaporating the filtrate on the water bath. The dried residue
represents the salts in the weight taken.
Chloride of sodium (common salt) may be estimated by dissolving the total
salts in water, adding potassium chromate, and titrating with N/10 silver
nitrate solution.
Copper, lead, iron, magnesium, and calcium may also be tested for in the
salts, by ordinary reactions.
Arsenic is best tested for by the Gutzeit method. About 5 c.c. is placed in a
test-tube, a few fragments of granulated zinc free from arsenic, and 10 c.c.
dilute hydrochloric acid added, and the mouth of the tube covered with a
small filter paper, moistened three successive times with an alcoholic

solution of mercury bichloride and dried. After thirty minutes the filter
paper is examined, when a yellow stain will be observed if arsenic is
present.
Sulphates.—These may be precipitated with barium chloride in acid
solution, in the usual way, dried, ignited, and weighed.
Sulphites give with barium chloride a precipitate soluble in hydrochloric
acid. If the precipitate is well washed with hot water, and a few drops of
iodine solution together with starch paste added, the presence of sulphites is
proved by the gradual disappearance of the blue starch-iodine compound
first formed.
Thiosulphates are detected by precipitating any sulphite and sulphate with
barium chloride, filtering, acidifying, and adding a few drops of potassium
permanganate solution, when in the presence of a mere trace of
thiosulphate, the solution becomes cloudy.
Sulphides.—Lewkowitsch recommends testing for these by replacing the
mercury bichloride with lead acetate paper in the Gutzeit arsenic test. Any
sulphide causes a blackening of the lead acetate paper.
Sugars may be tested for both before and after inversion, by boiling with
Fehlings' solution, when no reduction should take place, if pure.
Fatty acids are detected by the turbidity they produce when the diluted
glycerine is acidified.

CHAPTER XI.
STATISTICS OF THE SOAP INDUSTRY.

Until the year 1853 the amount of soap produced annually in this country
was readily obtainable from the official returns collected for the purpose of
levying the duty, and the following figures, taken at intervals of ten years
for the half century prior to that date, show the steady development of the
industry during that period:—

Year. Manufactured. Consumed. Exported. Duty per Ton.
Cwts. Cwts. Cwts. £
1801 509,980 482,140 26,790 21
1811 678,570 651,780 26,790 21
1821 875,000 839,290 35,710 28
1831 1,098,210 955,360 142,850 28
1841 1,776,790 1,517,860 258,930 14
1851 1,937,500 1,741,070 196,430 14

Since the repeal of the soap duty, the revenue from which had reached about
£1,000,000 per annum, no accurate means of gauging the production exists, but
it is estimated that it has nearly quadrupled during the last fifty-five years, being
now some 7,000,000 or 8,000,000 cwt. per annum.
The number of soap manufacturers in the United Kingdom is nearly 300, and
the amount of capital invested in the industry is roughly estimated to approach
£20,000,000 sterling.
Official figures are still available for the amount and value of soap annually
imported and exported to and from the United Kingdom, the returns for the last
eight years being:—

Imports.

Household. Toilet. Total.[13]
Year. Quantity. Value. Quantity. Value. Quantity. Value
Cwts. £ Cwts. £ Cwts. £
1900 ... ... ... ... 191,233 244,345
1901 ... ... ... ... 302,555 315,026
1902 ... ... ... ... 361,851 429,300
1903 273,542 284,37625,749 98,032 462,959 499,407
1904 254,425 268,40817,962 81,162 383,122 438,966
1905 274,238 279,04419,631 98,507 473,067 500,430
1906 309,975 311,114 18,554 101,243399,070 468,086
1907 228,035 263,96518,244 99,432 504,710 545,385

Household and toilet soaps were not given separately prior to 1903.

The imports during the last three years for which complete figures are
obtainable, came from the following sources:—

Household Soap.

1904. 1905. 1906.
£ £ £
From Netherlands 4,315 3,620 3,368
France 14,339 17,783 24,747
Italy 24,209 18,129 32,972
United States 218,740 235,612 242,294
Other Foreign Countries 6,785 3,873 7,448
Total from Foreign Countries 268,388 279,017 310,829
Total from British Possessions 20 27 285
Total 268,408 279,044 311,114

Toilet Soap.

1904. 1905. 1906.
£ £ £
From Germany 3,509 3,516 3,001
Netherlands 5,937 5,773 5,919
Belgium 1,568 1,861 3,145
France 7,120 7,633 5,794
Italy 1,176 255 1,233
United States 59,863 74,51678,382
Other Foreign Countries 166 147 196
Total from Foreign Countries 79,339 93,70197,670
Total from British Possessions 1,823 4,411 3,225
Total 81,162 98,112 100,895

Exports.

The exports from the United Kingdom during the past eight years have been as
follows:—

Household. Toilet. Total.[14]
Year. Quantity. Value. Quantity. Value. Quantity. Value.
Cwts. £ Cwts. £ Cwts. £
1900 ... ... ... ... 874,214 939,510
1901 ... ... ... ... 947,485 999,524
1902 ... ... ... ... 1,051,624 1,126,657
1903 998,995 900,814 38,372 217,9281,057,164 1,143,661
1904 1,049,022 955,774 40,406 228,5741,108,174 1,208,712
1905 1,167,976 1,013,83743,837 248,4251,230,310 1,284,727
1906 1,131,294 1,009,65346,364 261,1861,210,598 1,309,556
1907 1,114,624 1,095,17050,655 280,1861,240,805 1,459,113

Household and toilet soaps were not given separately prior to 1903.
The exports for the last three years for which complete figures are available,
consisted of the following:—

Household Soap.

1904. 1905. 1906.
£ £ £
To Sweden 3,027 2,911 3,677
Norway 4,173 3,921 6,005
Netherlands 39,420 41,197 48,601
Dutch Possessions in the Indian Seas 8,586 10,293 7,746
Belgium 73,996 51,583 7,729
France 11,741 12,222 22,907
Portuguese East Africa 28,987 42,981 40,478
Canary Islands 24,763 27,864 27,579
Italy 2,842 3,187 3,962
Turkey 6,974 7,858 5,897
Egypt 12,110 9,467 12,035
China (exclusive of Hong-Kong and Macao) 49,235 114,156 89,169
United States 3,885 1,975 3,924
Columbia 3,601 501 1,364
Ecuador 3,075 3,096 6,861
Chili 5,972 4,865 9,203

Brazil 35,197 28,198 31,726
Argentine Republic 7,802 8,954 13,084
Other Foreign Countries 40,058 53,914 77,687
Total to Foreign Countries 365,444429,143 419,634
To Channel Islands 5,301 8,328 7,968
Gibraltar 13,272 13,868 12,661
British West Africa—
Gold Coast 22,598 18,513 23,423
Lagos 7,751 8,032 9,518
Nigerian Protectorate 14,942 15,299 20,951
Cape of Good Hope 158,517143,750 136,388
Natal 74,848 71,874 46,771
British India—
Bombay (including Kurachi) 59,406 68,945 77,867
Madras 6,364 6,697 10,355
Bengal, Eastern Bengal and Assam. 26,534 23,087 22,648
Burmah 26,389 35,727 37,103
Straits Settlements and Dependencies 26,516 32,214 39,749
Hong-Kong 14,119 15,153 15,685
British West India Islands 74,069 58,881 67,331
British Guiana 12,661 12,023 11,557
Other British Possessions 47,043 52,303 50,044
Total to British Possessions 590,330584,694 590,019
Total 955,7741,013,8371,009,653

Toilet Soap.

1904. 1905. 1906.
£ £ £
To Germany 5,051 6,322 6,620
Belgium 3,730 3,265 3,355
France 7,903 8,988 9,324
Portuguese East Africa 2,215 3,973 4,658
Egypt 2,302 3,350 3,525
China (exclusive of Hong-Kong and Macao) 3,096 3,115 3,645
Japan (including Formosa) 3,300 4,649 3,382

United States 50,043 50,668 52,124
Brazil 1,879 2,241 2,292
Other Foreign Countries 22,002 26,081 29,214
Total to Foreign Countries 101,521112,652 118,139
To Cape of Good Hope 14,094 14,815 14,988
Natal 8,897 11,913 7,280
British India—
Bombay (including Kurachi) 24,665 24,672 28,316
Madras 4,333 5,851 6,624
Bengal, Eastern Bengal and Assam 14,129 16,021 15,969
Burmah 3,299 3,400 4,667
Straits Settlements and Dependencies 3,590 5,092 4,798
Ceylon and Dependencies 12,210 11,118 12,854
Australia—
Western Australia 1,549 1,394 1,137
South Australia, (including Northern Territory) 895 644 637
Victoria 11,989 13,614 12,774
New South Wales 3,920 4,278 4,139
Queensland 957 1,097 1,108
Tasmania 482 315 547
New Zealand 5,093 4,498 5,503
Canada 6,382 6,196 8,185
Other British Possessions 11,069 10,855 13,521
Total to British Possessions 127,053135,773143,047
Total 228,574248,425261,186

The following statistics extracted from official consular reports, etc., show the
extent of the soap industry in other parts of the world.
United States.—According to the Oil, Paint and Drug Report the total
production of soap in the United States during 1905, exclusive of soap products
to the value of $1,437,118 made in establishments engaged primarily in the
manufacture of other products, reached a value of $68,274,700, made up in the
following manner:—

Quantity. Value.
Lbs. $

Hard soaps ... 56,878,486
Tallow soap 846,753,798 32,610,850
Olein soap 29,363,376 1,363,636
Foots soap 85,000,133 3,090,312
Toilet soaps, including medicated, shaving, and other
130,225,417 9,607,276
special soaps
Powdered soaps, sold as such 120,624,968 4,358,682
All other soaps 143,390,957 6,097,670
Soft soap 33,613,416 667,064
Special soap articles ... 554,881

France.—This country exported common soap during 1906 to the value of
£556,000, or £8,000 more than in 1905.
The chief centre of the soap industry is Marseilles, which, with about fifty soap
factories, produces annually some 3,000,000 cwts.
Germany imported in 1905 soap and perfumery to the value of £3,032, that
exported amounting to £15,364.
In Saxony there are eighty soap factories.
Russia.—There are fifty large soap factories in Russia, the annual output from
which is about 2,250,000 cwt.
Roumania.—This country possesses about 230 small and eighteen large soap
and candle factories, most of which produce only common soap, there being
only one firm—in Bucharest—which makes milled soaps.
Denmark.—In this country there are some 200 small soap factories.
Australia.—According to a Board of Trade report, there were ninety-eight soap
and candle factories in Australia in 1905, employing 1,568 hands, and
producing 495,036 cwt. of soap.
Queensland.—In 1905 this country contained twenty-one soap and candle
works, in which 142 hands were employed, and having an output valued at
£86,324.
Hong-Kong.—There are about twenty-four soap factories on this island.

Japan.—A Swiss consular report states that in Japan there are now some fifty
soap works, producing about 15,000,000 tablets monthly.
Fiji Islands.—These possess only one soap factory, the output from which is 9
cwt. daily.
The following table, compiled from various consular and other official returns,
shows the quantity and value of soap imported into different countries and
places during the years 1905-7:—

Household. Toilet. Total.
Place and Date. Quantity. Value. Quantity. Value. Quantity. Value.
Europe—
Cyprus, 1905 ... ... ... ... ... £9,983
Iceland, 1906 ... ... ... ... ... £6,423
Switzerland, 1,702,800
... ... ... ... ...
1906 kilos.
About
1,800,000
Turkey ... ... ... ... ...
lb. per
annum
Africa—
13,609
Algeria, 1906 £228,640 ... ... ... ...
tons
Cape Colony, 15,897,800 427,600
£145,000 ... ... ...
1906 lb. lb.
Gold Coast,
... ... ... ... ... £23,987
1906
Lourenço, 357,638 36,000
£4,293 £2,195 ... ...
Marques, 1906 lb. lb.
4,263,000
Natal, 1906 ... 9,870 lb. ... ... ...
lb.
Orange River 2,382,000
£23,000 1,748 lb. ... ... ...
Colony, 1906 lb.
Pemba, 1905 ... ... ... ... ... £1,092
Rhodesia, 257,600
... 2,909 lb. ... ... ...
1906 lb.
Southern
... ... ... ... ... £11,990
Nigeria, 1905

Tangier ... ... ... ... ... £4,554
Transvaal, 4,407,000 202,200
£81,000 ... ... ...
1906 lb. lb.
Tripoli, 1905 ... ... ... ... ... £6,080
1,539
Tunis, 1906 ... ... ... ... £23,727
tons
Zanzibar,
... ... ... ... ... £6,102
1906
America—
1,031 606,046
Bahia, 1906 ... ... ... ...
tons milreis
1,782
Brazil, 1906 ... ... ... ... tons from ...
U.K.
British
... ... ... ... ... £13,733
Guiana, 1906-7
Canada,
... ... ... ... ... $600,999
1906-7
Columbia,
1906—
65,991
Cartagena ... ... ... ... ...
tons
814,671
Barranquilla ... ... ... ... $14,712
lb.
Costa Rica, £1,269
... ... ... ... ...
1906 from U.K.
Ecuador, 759,034
... ... ... ... ...
1904 kilos.
Granada,
... ... ... ... ... £3,867
1905
Guatemala,
... £900 ... ... ... ...
1906
Martinique, 693,269
£6,955 ... ... ... ...
1906 kilos.
Mexico,
... £5,982 ... ... ... ...
1905-6

San 754,587
... ... ... ... ...
Domingo, 1906 lb.
St. Vincent,
... ... ... ... ... £1,375
1905-6
Surinam, 1,142
... £3,905 ... ... ...
1906 tons
Trinidad,
... ... ... ... ... £29,967
1906-7
United States,
... $399,797 ... $1,071,446... $1,471,243
1905
Asia--
423,700
Ceylon, 1906 ... ... ... ... ...
rupees
China, 1906 ... ... ... ... ... £216,042
Hangchow,
... ... ... ... ... £5,888
1906
183,998
India, 1906-7 ... ... ... ... £215,210
cwts.
Kiungchow,
... £575 ... ... ... ...
1905
Shanghai,
... ... ... ... ... £93,256
1905
Smyrna, 1906 ... ... ... ... 261 tons ...
Australasia--
Australia, 891,117
... ... £65,840 ... ...
1906 lb.
Fiji, 1906 ... ... ... ... ... £1,760
New Zealand,
... ... ... ... ... £36,843
1905
Philippine
... ... ... ... ... £9,137
Islands, 1905

Exports.

Household. Toilet. Total
Place and
Quantity. Value. Quantity. Value. Quantity. Value
Date

Europe--
Candia, 2,200
... ... ... ... £34,000
Crete, 1906 tons.
About
Greece ... ... ... ... ... 500,000 Fr.
per annum.
3,992,800
Italy, 1907 £95,840 ... ... ... ...
kilos.
Leghorn, 1,521
... ... ... ... £37,065
1906 tons.
4,750,996
Spain, 1905 £98,840 ... ... ... ...
kilos.
Switzerland, 77,300
... ... ... ... ...
1906 kilos.
Africa--
Cape
200 lb. ... ... ... ... ...
Colony, 1906
Natal, 1906 75,225 lb. ... ... ... ... ...
Seychelles, 419,329
... ... ... ... 129,590 Rs.
1906 kilos.
America--
New
... ... ... ... ... £55,534
Orleans, 1906
Perambuco, 3,582 1,087,797,150
... ... ... ...
1906 tons. rei.
United 44,110,949
... ... $1,042,185 ... ...
States, 1905 lb.
Asia--
Japan, 1906 ... ... ... ... ... £83,877
Smyrna,
... ... ... ... 322 tons. ...
1906

FOOTNOTES:

[13] Including soap powder and soap stock.
[14] Including soap powder and soap stock.

APPENDIX A.
COMPARISON OF DEGREES, TWADDELL AND BAUMÉ,
WITH ACTUAL DENSITIES.

Tw. B. Density. Tw. B. Density. Tw. B. Density. Tw. B. Density.
0 0 1.000 44 26.0 1.220 88 44.11.440 13157.11.655
1 0.7 1.005 45 26.4 1.225 89 44.41.445 13257.41.660
2 1.4 1.010 46 26.9 1.230 90 44.81.450 13357.71.665
3 2.1 1.015 47 27.4 1.235 91 45.11.455 13457.91.670
4 2.7 1.020 48 27.9 1.240 92 45.41.460 13558.21.675
5 3.4 1.025 49 28.4 1.245 93 45.81.465 13658.41.680
6 4.1 1.030 50 28.8 1.250 94 46.11.470 13758.71.685
7 4.7 1.035 51 29.3 1.255 95 46.41.475 13858.91.690
8 5.4 1.040 52 29.7 1.260 96 46.81.480 13959.21.695
9 6.0 1.045 53 30.2 1.265 97 47.11.485 14059.51.700
10 6.7 1.050 54 30.6 1.270 98 47.41.490 14159.71.705
11 7.4 1.055 55 31.1 1.275 99 47.81.495 14260.01.710
12 8.0 1.060 56 31.5 1.280 10048.11.500 14360.21.715
13 8.7 1.065 57 32.0 1.285 10148.41.505 14460.41.720
14 9.4 1.070 58 32.4 1.290 10248.71.510 14560.61.725
15 10.01.075 59 32.8 1.295 10349.01.515 14660.91.730
16 10.61.080 60 33.3 1.300 10449.41.520 14761.11.735
17 11.2 1.085 61 33.7 1.305 10549.71.525 14861.41.740
18 11.9 1.090 62 34.2 1.310 10650.01.530 14961.61.745
19 12.41.095 63 34.6 1.315 10750.31.535 15061.81.750
20 13.01.100 64 35.0 1.320 10850.61.540 15162.11.755
21 13.61.105 65 35.4 1.325 10950.91.545 15262.31.760
22 14.21.110 66 35.8 1.330 110 51.21.550 15362.51.765
23 14.91.115 67 36.2 1.335 111 51.51.555 15462.81.770
24 15.41.120 68 36.6 1.340 112 51.81.560 15563.01.775
25 16.01.125 69 37.0 1.345 113 52.11.565 15663.21.780
26 16.51.130 70 37.4 1.350 114 52.41.570 15763.51.785

27 17.11.135 71 37.8 1.355 115 52.71.575 15863.71.790
28 17.71.140 72 38.2 1.360 116 53.01.580 15964.01.795
29 18.31.145 73 38.6 1.365 117 53.31.585 16064.21.800
30 18.81.150 74 39.0 1.370 118 53.61.590 16164.41.805
31 19.31.155 75 39.4 1.375 119 53.91.595 16264.61.810
32 19.81.160 76 39.8 1.380 12054.11.600 16364.81.815
33 20.31.165 77 40.1 1.385 12154.41.605 16465.01.820
34 20.91.170 78 40.5 1.390 12254.71.610 16565.21.825
35 21.41.175 79 40.8 1.395 12355.01.615 16665.51.830
36 22.01.180 80 41.2 1.400 12455.21.620 16765.71.835
37 22.51.185 81 41.6 1.405 12555.51.625 16865.91.840
38 23.01.190 82 42.0 1.410 12655.81.630 16966.11.845
39 23.51.195 83 42.3 1.415 12756.01.635 17066.31.850
40 24.01.200 84 42.7 1.420 12856.31.640 17166.51.855
41 24.51.205 85 43.1 1.425 12956.61.645 17266.71.860
42 25.01.210 86 43.4 1.430 13056.91.650 17367.01.865
43 25.51.215 87 48.8 1.435

(From The Oil and Colour Trades Journal Diary.)

APPENDIX B.
COMPARISON OF DIFFERENT THERMOMETRIC SCALES.

Cent. Fahr. Cent. Fahr. Cent. Fahr. Cent. Fahr.
-40 -40 2 35.6 44 111.2 86 186.8
39 38.2 3 87.4 45 113 87 188.6
38 36.4 4 39.2 46 114.8 88 190.4
37 34.6 5 41 47 116.6 89 192.2
36 32.8 6 42.8 48 118.4 90 194
35 31 7 44.6 49 120.2 91 195.8
34 29.2 8 46.4 50 122 92 197.6
33 27.4 9 48.2 51 123.8 93 199.4
32 25.6 10 50 52 125.6 94 201.2
31 23.8 11 51.8 53 127.4 95 203
30 22 12 58.6 54 129.2 96 204.8
29 20.2 13 55.4 55 131 97 206.6
28 18.4 14 57.2 56 132.8 98 208.4
27 16.6 15 59 57 134.6 99 210.2
26 14.8 16 60.8 58 136.4 100 212
25 13 17 62.6 59 138.2 101 213.8
24 11.2 18 64.4 60 140 102 215.6
23 9.4 19 66.2 61 141.8 +103 +217.4
22 7.6 20 68 62 143.6 104 219.2
21 5.8 21 69.8 63 145.4 105 221
20 4 22 71.6 64 147.2 106 222.8
19 2.2 23 73.4 65 149 107 224.6
18 0.4 24 75.2 66 150.8 108 226.4
17 +1.4 25 77 67 152.6 109 228.2
16 3.2 26 78.8 +68 +154.4 +110 +230
15 5 27 80.6 69 156.2 111 231.8
14 6.8 28 82.4 70 158 112 283.6
13 8.6 29 84.2 71 159.8 113 235.4

12 10.4 30 86 72 161.6 114 237.2
11 12.2 31 87.8 73 163.4 115 239
10 14 +32 +89.6 74 165.2 +116 +240.8
9 15.8 33 91.4 75 167 117 242.6
8 17.6 34 93.2 76 168.8 118 244.4
7 19.4 35 95 77 170.6 119 246.2
6 21.2 36 96.8 78 172.4 120 248
5 23 37 98.6 79 174.2 121 249.8
4 24.8 49 100.4 80 176 +122 +251.6
3 26.6 39 102.2 81 177.8 123 253.4
2 28.4 40 104 82 179.6 124 255.2
1 30.2 41 105.8 83 181.4 125 257
0 32 42 107.6 84 183.2 126 258.8
+1 33.8 43 109.4 85 185 127 260.6

(From Soaps, by G. H. Hurst, published by Scott, Greenwood & Son.)

APPENDIX C.
TABLE OF THE SPECIFIC GRAVITIES OF SOLUTIONS OF CAUSTIC
SODA.

Lb. of actual NaOH contained in 1
Per cent. by
gallon of lye made from commercial
weight of
caustic of
Degrees Specific
Na2O. NaOH. 77 per cent. 74 per cent. 70 per cent.
Twaddell. gravity.
1 1.005 0.368 0.474 0.048 0.046 0.043
2 1.010 0.742 0.957 0.097 0.092 0.087
3 1.015 1.114 1.436 0.146 0.131 0.129
4 1.020 1.480 1.909 0.194 0.185 0.180
5 1.025 1.834 2.365 0.243 0.231 0.219
6 1.030 2.194 2.830 0.291 0.278 0.262
7 1.035 2.521 3.252 0.335 0.320 0.303
8 1.040 2.964 3.746 0.389 0.371 0.350
9 1.045 3.244 4.184 0.438 0.417 0.393
10 1.050 3.590 4.631 0.486 0.461 0.438
11 1.055 3.943 5.086 0.536 0.510 0.483
12 1.060 4.292 5.536 0.586 0.558 0.528
13 1.065 4.638 5.982 0.636 0.607 0.573
14 1.070 4.972 6.413 0.680 0.653 0.617
15 1.075 5.311 6.911 0.742 0.707 0.668
16 1.080 5.648 7.285 0.786 0.749 0.709
17 1.085 5.981 7.715 0.836 0.798 0.755
18 1.090 6.311 8.140 0.886 0.845 0.800
19 1.095 6.639 8.564 0.937 0.894 0.846
20 1.100 6.954 8.970 0.986 0.941 0.890
21 1.105 7.276 9.386 1.037 0.989 0.938
22 1.110 7.594 9.796 1.087 1.037 0.981
23 1.115 7.910 10.203 1.137 1.123 1.026
24 1.120 8.223 10.607 1.187 1.175 1.071

25 1.125 8.583 11.107 1.238 1.181 1.117
26 1.130 8.893 11.471 1.296 1.237 1.170
27 1.135 9.251 11.933 1.354 1.292 1.122
28 1.140 9.614 12.401 1.413 1.350 1.277
29 1.145 9.965 12.844 1.470 1.413 1.337
30 1.150 10.313 13.303 1.529 1.460 1.381
31 1.155 10.666 13.859 1.600 1.528 1.445
32 1.160 11.008 14.190 1.646 1.541 1.456
33 1.165 11.347 14.637 1.705 1.627 1.539
34 1.170 11.691 15.081 1.764 1.684 1.593
35 1.175 12.025 15.512 1.822 1.739 1.645
36 1.180 12.356 16.139 1.904 1.817 1.719
37 1.185 12.692 16.372 1.942 1.853 1.753
38 1.190 13.016 16.794 1.998 1.887 1.804
39 1.195 13.339 17.203 2.055 1.962 1.856
40 1.200 13.660 17.629 2.122 2.026 1.916
41 1.205 14.058 18.133 2.185 2.085 1.973
42 1.210 14.438 18.618 2.252 2.147 2.033
43 1.215 14.823 19.121 2.323 2.221 2.097
44 1.220 15.124 19.613 2.392 2.280 2.161
45 1.225 15.502 19.997 2.444 2.338 2.206
46 1.230 15.959 20.586 2.562 2.417 2.285
47 1.235 16.299 20.996 2.593 2.475 2.341
48 1.240 16.692 21.532 2.669 2.548 2.410

Lb. of actual NaOH contained in 1
Per cent. by
gallon of lye made from commercial
weight of
caustic of
Degrees Specific
Na2O. NaOH. 77 per cent. 74 per cent. 70 per cent.
Twaddell. gravity.
49 1.245 17.060 22.008 2.739 2.615 2.474
50 1.250 17.424 22.476 2.809 2.681 2.536
51 1.255 17.800 22.962 2.881 2.750 2.602
52 1.260 18.166 23.433 2.952 2.818 2.666
53 1.265 18.529 23.901 3.020 2.886 2.730
54 1.270 18.897 24.376 3.095 2.955 2.795

55 1.275 19.255 24.858 3.171 3.027 2.863
56 1.280 19.609 25.295 3.237 3.090 2.932
57 1.285 19.961 25.750 3.308 3.158 2.988
58 1.290 20.318 26.210 3.381 3.227 3.053
59 1.295 20.655 26.658 3.452 3.364 3.117
60 1.300 21.156 27.110 3.524 3.394 3.182
61 1.305 21.405 27.611 3.603 3.439 3.253
62 1.310 21.785 28.105 3.682 3.514 3.224
63 1.315 22.168 28.595 3.760 3.593 3.395
64 1.320 22.556 29.161 3.849 3.674 3.475
65 1.325 22.926 29.574 3.919 3.742 3.539
66 1.330 23.310 30.058 3.997 3.816 3.610
67 1.335 23.670 30.535 4.072 3.891 3.681
68 1.340 24.046 31.018 4.156 3.967 3.754
69 1.345 24.410 31.490 4.232 4.042 3.824
70 1.350 24.765 31.948 4.312 4.116 3.894
71 1.355 25.152 32.446 4.396 4.196 3.970
72 1.360 25.526 32.930 4.478 4.274 4.043
73 1.365 25.901 33.415 4.561 4.354 4.109
74 1.370 26.285 33.905 4.645 4.434 4.194
75 1.375 26.650 34.382 4.728 4.513 4.269
76 1.380 27.021 34.855 4.810 4.592 4.344
77 1.385 27.385 35.328 4.893 4.670 4.418
78 1.390 27.745 35.795 4.975 4.794 4.493
79 1.395 28.110 36.258 5.058 4.828 4.567
80 1.400 28.465 36.720 5.141 4.907 4.642
81 1.405 28.836 37.203 5.227 4.989 4.720
82 1.410 29.203 37.674 5.312 5.071 4.797
83 1.415 29.570 38.146 5.397 5.135 4.873
84 1.420 29.930 38.610 5.482 5.233 4.950
85 1.425 30.285 39.071 5.567 5.314 5.027
86 1.430 30.645 39.530 5.653 5.396 5.104
87 1.435 30.995 39.986 5.738 5.467 5.181
88 1.440 31.349 40.435 5.823 5.558 5.258
89 1.445 31.700 40.882 5.908 5.640 5.335
90 1.450 32.043 41.335 5.923 5.721 5.412

91 1.455 32.460 41.875 6.093 5.816 5.502
92 1.460 32.870 42.400 6.191 5.909 5.608
93 1.465 33.283 42.935 6.290 6.004 5.679
94 1.470 33.695 43.467 6.389 6.009 5.769
95 1.475 34.092 43.980 6.487 6.193 5.856
96 1.480 34.500 44.505 6.586 6.287 5.948
97 1.485 34.899 45.013 6.685 6.381 6.035
98 1.490 35.245 45.530 6.784 6.476 6.126
99 1.495 35.691 46.041 6.884 6.571 6.216
100 1.500 36.081 46.545 6.982 6.665 6.303

(From Soaps, by G. H. Hurst, published by Scott, Greenwood & Son.)

APPENDIX D.
TABLE OF STRENGTH OF CAUSTIC POTASH SOLUTIONS
AT 60° F.

Specific gravity. Degrees Twaddell. Per cent. KOH. Lb. of KOH per gal.
1.060 12 5.59 0.59
1.110 22 11.31 1.25
1.150 30 15.48 1.77
1.190 38 19.29 2.21
1.230 46 23.22 2.84
1.280 56 27.87 3.56
1.330 66 31.32 4.16
1.360 72 35.01 4.76
1.390 78 38.59 5.36
1.420 84 40.97 5.81
1.440 88 43.83 6.31
1.470 94 47.16 6.93
1.520 104 51.09 7.76
1.600 112 55.62 8.89
1.680 136 60.98 10.24
1.780 156 67.65 12.04
1.880 176 75.74 14.23
2.000 200 86.22 17.24

(From Soaps, by G. H. Hurst, published by Scott, Greenwood & Son.)

THE END.

INDEX.
A.

Acetic Acid, 10

Acid, Acetic, 10

---- Arachidic, 10

---- Behenic, 10

---- Butyric, 10

---- Capric, 10

---- Caproic, 10

---- Caprylic, 10

---- Carnaubic, 10

---- Cerotic, 10

---- Daturic, 10

---- Doeglic, 11

---- Elæomargaric, 12

---- Elæostearic, 12

---- Erucic, 11

---- Ficocerylic, 10

---- Hyænic, 10

---- Hypogæic, 11

---- Isolinolenic, 12

---- Isovaleric, 10

---- Jecoric, 12

---- Lauric, 10

---- Lignoceric, 10

---- Linolenic, 12

---- Linolic, 12

---- Margaric, 10

---- Medullic, 10

---- Melissic, 10

---- Moringic, 11

---- Myristic, 10

---- Oleic, 11

---- Palmitic, 10

---- Physetoleic, 11

---- Pisangcerylic, 10

---- Psyllostearylic, 10

---- Rapic, 11

---- Ricinoleic, 13

---- Saponification, 19-21

---- Stearic, 10

---- Tariric, 12

---- Telfairic, 12

---- Theobromic, 10

---- Tiglic, 11

---- value, 118, 128

Acids, Classification of fatty, 10

---- Fatty, 9-13

---- ---- Combination with Alkali, 45, 46

Acids, Fatty, Preparation by acid process, 19-21

---- ---- ---- by ferment process, 16

---- ---- ---- by Twitchell's process, 20

---- Saturated fatty, 11

---- Unsaturated fatty, 11

Albumen in soap, 90

Alcohols, Estimation of, 128

Aldehydes, Estimation of, 129

Alkali, Caustic and carbonated, 38, 39, 123-126

Alkali in soap, Determination of, 131, 132

Amyl salicylate, 107

Andiroba oil, 32

Animal charcoal, 115

---- fats, Treatment of, 43

Anise (star) oil, 96

Anisic aldehyde, 108

Arachidic acid, 10

Arachis oil, 28

Artificial perfumes, 107-110

Ash, Soda, 39, 124, 125

Aspic oil, 96

Aqueous saponification, 14

Aubépine, 108

B.

Bacteria, Decomposition of fats by, 18

Baobab-seed oil, 36

Bar soap, 54, 55

Barring soap, 68

Bay oil, 97

Behenic acid, 10

Benzyl acetate, 108

Bergamot oil, 97

---- ---- (artificial), 109

Biniodide soaps, 87

Birch-tar soap, 88

Bitter almond oil, 97

Bleaching palm oil, 41

---- rosin, 43

Boiling-on-strength, 51

Bois de Rose Femelle oil, 99

Bone-fat, 30

---- ---- treatment of, 43

Borax in soap, 88

Boric acid in soap, 88

Boric acid in soap, Determination of, 135

Borneo tallow, 32

Brine, 39

Bromine absorption of oils and fats, 122

Brown Windsor soap, 78, 98

Butter goa, 33

---- kokum, 33

---- shea, 31

Butyric acid, 10

Butyrin, 8

C.

Calico-printer's soap, 93

Cananga oil, 98

Candle-nut oil, 33

Capric acid, 10

Caprin, 8

Caproic acid, 10

Caproin, 8

Caprylic acid, 10

Caprylin, 8

Carapa oil, 32

Caraway oil, 98

Carbolic acid in soap, Determination of, 134

Carbolic soap, 88

Carbonate potash, 39, 125, 126

---- soda, 39, 124, 125

Carnaubic acid, 10

Cassia oil, 98

Castor oil, 30

Caustic potash, 39, 123

---- soda, 39, 123

Cayenne linaloe oil, 99

Cedarwood oil, 98

Cerotic acid, 10

Charcoal, Animal, 115

Chinese vegetable tallow, 31

Cholesterol in unsaponified matter, 120

Cinnamon oil, 98

Citral, 108

Citronella oil, 99

Citronellal, 108

Cleansing soap, 60, 61

Close-piling soap, 71

Clove oil, 99

Coal tar soaps, 88

Cocoa-nut oil, 25, 26

Cohune-nut oil, 34

Cold process soap-making, 46, 47

Colouring soap, 66, 80, 82

Compressing soap, 83, 85

Concrete orris oil, 100

Constitution of oils and fats, 6, 7

Conversion of oleic acid into solid acids, 11, 12

Cooling soap, 74, 76

Coprah oil, 25, 26

Cotton-seed oil, 27, 42

---- ---- Refining, 42

---- soapstock, 40

---- stearine, 28

Coumarin, 108

Crude glycerine, 113, 136-139

Crutching soap, 63

Curcas oil, 33

Curd mottled soap, 52, 53

Curd soaps, 52

Cutting and stamping toilet soap, 85

D.

Daturic acid, 10

Decolorisation, Glycerine, 115

Decomposition of fats by bacteria, 18

Detergent action of soap, 4, 5

Diglycerides, 7

Dika fat, 36

Disinfectant soaps, 66

Distearine, 7

Distillation, glycerine, 114

Distilled glycerine, 114

Doeglic acid, 11

Double distilled glycerine, 115

Dregs in fats and oils, Determination of, 120, 121

Drying soap, 71, 78-80

Dynamite glycerine, 115

E.

Elaidin reaction, 12

Electrical production of soap, 59

Elæomargaric acid, 12

Elæostearic acid, 12

Enzymes, Action of, 15-18

Erucic acid, 11

Essential oils, 96-107

---- ---- Examination of, 127-130

Ester value, 119, 128

Ether soap, 90

Eucalyptus oil, 100

Evaporation to crude glycerine, 112, 113

F.

Fat, Bone, 30

---- Dika, 36

---- Maripa, 34

---- Marrow, 30

---- Niam, 34

---- Tangkallah, 37

---- Treatment of bone, 43

Fats, Decomposition by bacteria of, 18

---- Treatment of animal, 43

---- Waste, 30

Fats and oils, Determination of acid value of, 118

---- ---- ---- of bromine absorption of, 122

---- ---- ---- of dregs, etc., in, 120, 121

---- ---- ---- of free acidity of, 117

---- ---- ---- of iodine absorption of, 121, 122

---- ---- ---- of saponification

---- ---- ---- equivalents of, 118

---- ---- ---- of saponification value, 118

---- ---- ---- of specific gravity of, 117 of titre of, 122, 123

---- ---- ---- of unsaponifiable matter in, 119

---- ---- ---- of water in, 120

---- ---- ---- Yield of glycerine from, 116

Fatty acids, 9-13, 31

---- ---- Classification of, 10

---- ---- Direct combination with alkali of, 45, 46

---- ---- in soap, Determination of, 131

---- ---- ---- Examination of, 133, 134

---- ---- Preparation by acid process, 19-21

---- ---- ---- by ferment process, 16

---- ---- ---- by Twitchell's process, 20

---- ---- Saturated, 11

---- ---- Unsaturated, 11

Fennel oil, 100

Ferment process for preparation of fatty acids, 16

Ferments, action of, 15-18

Ficocerylic acid, 10

Filling soap, 65

Fish oils, 30

"Fitting," 51

Floating soap, 90, 91

Fluorides in soap, 88

Formaldehyde soap, 88

Framing soap, 66

Free alkali in soap, Estimation of, 132

---- caustic in soap, Neutralising, 66

---- fat in soap, Determination of, 133

---- fatty acids, Determination of, 117

G.

Geraniol, 108

Geranium oils, 101

Geranium-sur-rose oil, 101

Ginger-grass oil, 101

Glycerides, 7, 8

Glycerine, Chemically pure, 115

---- Crude, 113, 136-139

---- decolorisation, 115

---- distillation, 114

---- Distilled, 114

---- dynamite, 115

---- in soap, Determination of, 134, 135

---- manufacture, 111-114

---- saponification, 116

---- soaps, 89

---- Yield of, from fats and oils, 116

Glycerol determination, acetin method, 136

---- ---- bichromate method, 137, 138

---- in lyes, Estimation of, 135

Goa-butter, 33

"Graining-out," 50

Grease, Animal, 30

---- Bone, 30

---- Kitchen, 30

---- Skin, 30

Guaiac wood oil, 101

H.

Halphen's reaction, 134

Heliotropin, 108

Hemp-seed oil, 29

Hyacinth, 108

Hyænic acid, 10

Hydrated soaps, 48, 49

Hydrolysis accelerated by heat and electricity, 14, 15

---- accelerated by use of chemical reagents, 19-23

---- accelerated with acid, 19, 21

---- Enzymic, 15-18

---- of oils and fats, 13-23

---- of soap, 3

Hypogæic acid, 11

I.

Ichthyol soap, 89

Inoy-kernel oil, 37

Iodine absorption of rose oil, 130

---- absorption of oils and fats, 121,122:

---- soap, 89

Ionone, 108

Isolinolenic acid, 12

Isovaleric acid, 10

Isovalerin, 8

J.

Jasmine, 109

Jecoric acid, 12

K.

Kananga oil, 98

Kapok oil, 32

"Kastilis," 88

Kokum butter, 33

L.

Lard, 25

Lauric acid, 10

Laurin, 8

Lavender oils, 101

Lemon-grass oil, 102

Lemon oil, 102

Lignoceric acid, 10

Lime oil, 102

---- saponification, 22

Linaloe oil, 102

Linalol, 109

Linalyl acetate, 109

Linolenic acid, 12

Linolic acid, 12

Linseed oil, 29

Lipase, 18

Liquoring of soaps, 64

Lyes, analysis of, 135

---- Determination of glycerol in, 135

---- Evaporation of, 112

---- Treatment of, 111, 112

Lysol soap, 89

M.

Mafura tallow, 35

Magnesia, Hydrolysis by, 22

Maize oil, 28

Margaric acid, 10

Margosa oil, 35

Marine animal oils, 30

---- soap, 49

Maripa fat, 34

Marjoram oil, 103

Medicated soaps, 86-90

Medullic acid, 10

Melissic acid, 10

Melting point, 130

Mercury soaps, 87

Milled toilet soaps, 78

Milling soap, 80, 81

---- soap-base, 54, 78

Mineral oil, saponifying, 58, 59

Mirbane oil or nitrobenzene, 109

Mixed glycerides, 8

Monoglycerides, 7

Monostearin, 7

Moringic acid, 11

Mottled soaps, 52, 53

---- ---- Pickling, 54

Moulds, Soap, 72, 85, 86

Mowrah-seed oil, 31

Musk (artificial), 109

Myristic acid, 8

Myristin, 8

N.

Naphthol soap, 89

Neroli Bigarade oil, 103

---- oil (artificial), 109

Neutralising free caustic in soap, 66, 80

Niam fat, 34

Nigre, 56

Nigres, Utilisation of, 56

Niobe oil or ethyl benzoate, 110

Nitrobenzene, 109

O.

Oeillet, 10

Oil, Andiroba, 32

---- Arachis, 28

---- Aspic (lavender spike), 96

---- Baobab-seed, 36

---- Bay, 97

---- Bergamot, 97

---- Bitter almond, 97

---- Bleaching palm, 41

---- Bois de Rose Femelle, 99

---- Cananga, 98

---- Candle-nut, 33

---- Carapa, 32

---- Caraway, 98

---- Cassia, 98

---- Castor, 30

---- Cayenne linaloe, 99

---- Cedarwood, 98

---- Cinnamon, 98

---- Citronella, 99

---- Clove, 99

---- Cocoa-nut, 25, 26

---- Cohune-nut, 34, 35

---- Concrete orris, 100

---- Coprah, 25, 26

---- Cotton-seed, 27, 42

---- Curcas, 33

---- Eucalyptus, 100

---- Fennel, 100

---- Geranium, 101

---- Ginger-grass, 101

---- Guaiac-wood, 101

---- Hemp-seed, 29

---- Inoy-kernel, 37

---- Kananga, 98

---- Kapok, 32

---- Lemon, 102

---- Lemon-grass, 102

---- Lime, 102

---- Linaloe, 102

---- Linseed, 29

---- Maize, 28

---- Margosa, 35

---- Marjoram, 103

---- Mowrah-seed, 31

---- Neroli Bigarade, 103

---- Olive, 26

---- Olive-kernel, 27

---- Orange, 163

---- Palm, 27, 41

---- Palm-nut, 26

---- Palmarosa, 103

---- Patchouli, 103

---- Peppermint, 103, 104

---- Persimmon-seed, 36

---- Peru-balsam, 104

---- Petit-grain, 104

---- Pongam, 35

---- Refining cotton-seed, 42

---- Rose, 105

---- Rosemary, 105

---- Safflower, 33, 34

---- Sandalwood, 105, 106

---- Saponifying mineral, 58, 59

---- Sassafras, 106

---- Sesame, 28, 29

---- Star-anise, 96

---- Sunflower, 29

---- Thyme, 106

---- Verbena, 106

---- Vetivert, 106-107

---- Wheat, 36

---- Wild mango, 36

---- Wintergreen, 107

---- Ylang-ylang, 107

Oils and fats, Constitution of, 6, 7

---- ---- Examination of, 117-123

---- ---- Hydrolysis of, 13-22

---- Fish and marine animal, 30

---- Lavender, 101

---- Refractive Index of, 122

---- treatment of vegetable, 43

Oleic acid, 11

---- ---- into solid acids, Conversion of, 11, 12

Olein, 8, 9, 31

---- Cocoa-nut, 31

---- Palm-nut, 31

Oleodidaturin, 8

Oleodipalmitin, 8

Oleodistearin, 8

Oleopaimitostearin, 8

Olive-kernel oil, 27

Olive oil, 26

Open-piling soap, 71

Optical rotation, 127

Orange oil, 103

Orchidée, 107

Orris oil, concrete, 100

P.

Palm oil, 27, 41

---- ---- Bleaching, 41

Palmarosa oil, 103

Palmitic acid, 10

Palmitin, 8

Palmitodistearin, 8

Palm-nut oil, 26

Pasting or saponification, 49

Patchouli oil, 103

Patent textile soaps, 94

Pearl-ash, Analysis of, 125, 126

Peppermint oil, 103, 104

Perfumer's soaps, 77, 78

Perfumes, Artificial and synthetic, 107-110

---- Soap, 95-110

Perfuming soaps, 94

Persimmon seed oil, 36

Peru-balsam oil, 104

Petit-grain oil, 104

Phenols, Determination of, 129

Physetoleic acid, 11

Phytosterol in unsaponifiable matter, 120

Pickling mottled soap, 54

Pisangcerylic acid, 10

Polishing soaps, 94

Pongam oil, 35

Potash, Carbonate, 39, 125, 126

---- Caustic, 89, 123

Potassium chloride, 126

---- Determination of, 126, 132

Powders, Soap, 94

Psyllostearylic acid, 10

R.

Rancidity, 18, 24

Rapic acid, 11

Refining cotton-seed oil, 42

Refractive index of oils and fats, 122

Remelted soaps, 77, 78

Resinate of soda, 43, 44

Ricinoleic acid, 13

Ricinolein, 8

Rose oil, 105

---- ---- (artificial), 110

Rosemary oil, 105

Rosin, 37, 38, 43, 44, 55

---- Bleaching, 43

---- Determination of, 133, 134

---- treatment, 43, 44

S.

Safflower oil, 33, 34

Safrol, 110

Salt, 39, 126

---- Determination of, 124, 125, 126, 132

Sandalwood oil, 105, 106

Santalol, 110

Saponification, 13-22, 49

---- accelerated by heat and electricity, 14, 15

---- accelerated by use of chemical reagents, 19, 23

---- accelerated with Twitchell's reagent, 20

---- Acid, 19, 21

---- Aqueous, 14

---- by ferment process, 20

---- equivalent, 118

---- Glycerine, 116

---- Lime, 22

---- under pressure, 47

---- value, 118, 128

Saponifying mineral oil, 58, 59

Sassafras oil, 106

Saturated acids, 11

Scouring soaps, 92, 93

Sesame oil, 28, 29

Settled soap, Treatment of, 60-76

Shaving soaps, 91

Shea butter, 31

Silicate of soda in soap, 65

Silicates of soda and potash, 127, 138

Silk scouring soaps, 93

---- dyer's soap, 93, 94

Slabbing soap, 68

Soap, Albumen in, 90

---- Analysis of, 130-35

---- Bar, 54, 55

---- Barring, 68

---- -base, Milling, 54, 78

---- Biniodide, 87

---- Birch-tar, 88

---- Borax, 88

---- Boric acid in, 88

---- ---- ---- ---- Determination, 135

---- Carbolic, 88

---- Classification of, 45

---- Cleansing, 60, 61

---- Coal-tar, 88

---- Cold process, 46, 47

---- Compressing, 83, 85

---- Cooling, 74-76

---- Crutching, 63

---- Curd, 52

---- Curd mottled, 53

---- Definition of, 1, 2

---- Detergent action of, 4, 5

---- Determination of carbolic acid in, 134

---- ---- of fatty acids in, 131

---- ---- of free alkali in, 132

---- ---- of free fat in, 133

---- ---- of glycerine in, 134, 135

---- ---- of total alkali in, 131

---- ---- of water in, 133

---- Drying, 71, 78-80

---- Electrical production of, 59

---- Ether, 90

---- Examination of fatty acids 133, 134

---- Filling, 65

---- Fluorides in, 90

---- formaldehyde, 88

---- frame, 66

---- framing, 66

---- from fatty acids, 45, 46

---- Glycerine, 89

---- Hydrated, 48, 49

---- Hydrolysis of, 3

---- Ichthyol, 89

---- Iodine, 89

---- Lysol, 89

---- Marine, 49

---- Milling, 80, 81

---- Monopole, 94

---- Mottled, 52, 53

---- moulds, 72, 85, 86

---- Naphthol, 89

---- Neutralising, colouring and perfuming, 66, 80, 82

---- Open and close piling, 71

---- perfumes, 95-110

---- Pickling mottled, 54

---- powders, 94

---- Properties of, 2

---- Salicylic acid, 88

---- Settling of, 55

---- Slabbing, 68

---- Soft, 41

---- Stamping, 71, 72, 85, 86

---- Sulphur, 89

---- Terebene, 90

---- Thymol, 90

---- Transparent, 57, 58

---- Treatment of settled, 60-76

---- Yellow household, 54, 55

Soap-making, 45-59

---- ---- Blue and grey mottled, 53

---- ---- "Boiling-on-strength," 51

---- ---- Cold process, 46, 47

---- ---- Combination of fatty acids with alkali, 45, 46

---- ---- Curd, 52

---- ---- Curd, Mottled, 53

---- ---- "Fitting," 51

---- ---- "Graining-out" or separation, 50

---- ---- Hydrated, 49

---- ---- "Pasting" or saponification, 49

---- ---- Soft, 48

---- ---- Transparent, 57, 58

---- ---- under pressure, 47

Soaps, Calico-printer's, 93

---- Disinfectant, 66

---- Floating, 90, 91

---- Liquoring of, 64, 65

---- Medicated, 86-90

---- Milled toilet, 78

---- Miscellaneous, 94

---- Perfumer's, 77, 78

---- Polishing, 94

---- Remelted, 77, 78

---- Scouring, 92

---- Shaving, 91

---- Silicating, 65

---- Silk dyer's, 93, 94

---- Textile, 91-94

---- Toilet, 77, 78

---- Woollen dyer's, 92

Soap-stock, 40

Soda ash, 39, 124, 125

---- ---- Caustic, 39, 125

---- Carbonate, 39, 124, 125

---- Caustic, 39, 123

---- Resinate, 43, 44

Soft soap-making, 48

Solidifying-point, 130

Specific gravity, Determination of, 117, 127

Stamping soap, 71, 72, 85, 86

Starch, Detection of, 121, 135

Steapsin, 18

Stearic acid, 10

Stearin, 8, 9

Stearine, Cotton-seed, 28

Stearodipalmitin, 8

Sulphides and sulphites, Determination of, 125

Sulphur soap, 89

Sunflower oil, 29

Superfatting material, 83

Synthetic perfumes, 107-110

T.

Table of caustic potash solutions, 151

---- of caustic soda solutions, 149, 150

---- of comparative densities, 147

---- of thermometric equivalents, 148

Tablet soap, 55

Talc, 65

Tallow, 24

---- Borneo, 32

---- Chinese vegetable, 31

---- Mafura, 35

Tangkallah fat, 37

Tariric acid, 12