12 



FATS, OILS, AND WAXES 



gravity varying from about 0*900 to 0*970 at 1 5. They are 

 insoluble in water and at ordinary temperatures are sparingly 

 soluble in cold alcohol, excepting castor oil which dissolves 

 readily in this solvent ; they, however, dissolve readily in 

 ether, chloroform, petroleum ether, benzene, carbon tetra- 

 chloride or carbon disulphide. 



CHEMICAL PROPERTIES OF FATS. 



One of the most important chemical properties of fats is 

 their decomposition by hydrolysis. 



The term hydrolysis, which literally means loosening by 

 water, is applied to any reaction in which a substance is broken 

 up into two or more simpler ones with the fixation of water. 



The following examples taken from a variety of different 

 classes of compounds all illustrate this reaction : 



CH S COOC 2 H 5 + H 2 O 

 Ethyl acetate 



CH S CN + 2H 2 O 

 Methyl cyanide 

 CgH 6 CONHCH ? COOH + H 2 

 Hippuric acid 

 CiH M O u + H,0 

 Malt sugar 

 C^H^NO,! + 2H 2 

 Amygdalin 



CHgCOOH + C 8 H B OH . . (i) 

 Acetic acid Ethyl alcohol 

 CHjCOOH + NH S (2) 



C 6 H 6 COOH + NH a CH 2 COOH . (3) 



Benzoic acid Glycine 



2C 6 H 12 0, .... (4) 



Glucose 



C 6 H B CHO + 2C,H u O a + HCN . (5) 



Benzalde- Glucose Hydro- 

 hyde cyanic acid 



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 



+ 3H 2 



COOC 



CH 2 OH 

 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. 368). 



The hydrolysis of fats for the purpose of preparing the free 

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



