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 Baume
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--