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 BAUME, 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 deg. 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 bee