PREPARATION OF FATTY ACIDS 13 



It will be seen from reaction (i) that the conversion of an 

 ester into an acid and an alcohol is an example of hydrolysis, 

 and since fats are esters it follows that they also must be 

 capable of hydrolysis. 



The reaction 



CH 2 OH 

 ^H^COOCH + 3 H 2 = aCjjH^COOH + CHOH 



CH 2 



OH 

 Stearic acid Glycerol 



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 (see p. 370). 



The hydrolysis of fats for the purpose of preparing the free 

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



I. 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 are 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 



