lo FATS, OILS, AND WAXES 



is, however, not readily brought about by water alone at 

 ordinary temperatures ; in the presence of enzymes, however, 

 the hydrolysis may be effected at a moderate temperature with 

 comparative ease. 



The hydrolysis of fats for the purpose of preparing the free 

 fatty acids may be effected in either of the following ways : — 



1. By acting on the fat with superheated steam in the 

 presence of a little lime or magnesia, which acts as a catalytic 

 agent. 



This method is the one most commonly adopted by 

 candle-makers for the preparation of fatty acids required in 

 the manufacture of candles. The fat is subjected to the action 

 of steam under pressure at 170° in large copper vessels in the 

 presence of a small quantity of lime. The resulting mixture 

 is then treated with sulphuric acid sufficient in amount to 

 combine with the lime, after which the free fatty acids rise to 

 the surface in a molten condition. 



2. By the action of concentrated sulphuric acid. 



The molten fats are stirred up in leaden vessels with 9 per 

 cent of concentrated sulphuric acid, the mixture being heated 

 to about 120° C. The mixture is then warmed with water 

 to remove the acid, and the acids arc further purified by 

 distillation with steam. 



SAPONIFICATION OF FATS. 



Closely related to hydrolysis is the reaction known as 

 saponification ; this reaction, which literally means " soap- 

 making," is that which takes place when a fat is boiled with 

 caustic alkali. The alkali acts in much the same way as 

 water, breaking up the ester into glycerol and the fatty acid 

 which, however, in this case, combines with the alkali to form 

 a salt : — 



C„H„COOCH, CH,OH 



C^HsbCOOCH + 3KOH = 3C„H35COOK + CHOH 



C^HajCOOCHg Potassium stearate, CHgOH 



Tristearin, a fat a soap Glycerol 



It SO happens that the sodium and potassium salts of pal- 

 mitic, stearic, and oleic acids dissolve in water, forming opales- 



