6o ORGANIC AGRICULTURAL CHEMISTRY 



further with the alkali present and the metal salt of the acid is 

 formed. 



Soap. — The sodium and potassium salts of some of the 

 fatty acids, chiefly palmitic and stearic, form the common 

 substance we know as soap. Thus when a fat is boiled with 

 dilute alkali, soap and glycerol are the products. 



CH2-OOC-C15H31 CH2-OH KOOC-C15H31 



CH-OOC-C15H31 +3 H2O -> CH-OH + KOOC-C15H31+3 H2O 



CH2-OOC-C15H31 +3 KOH CH2-OH KOOC-C15H31 



Glyceryl-tri-palmitate Saponifica- Glycerol Potassium palmitate 

 (fat) tion (soap) 



Saponification. — Such an hydrolysis of a fat is therefore 

 termed an action of saponification or soap formation. The 

 saponification of esters is thus a particular form of hydrolysis, 

 viz, in the presence of an alkali, and any alkaline hydrolysis 

 of an ester is termed saponification even though the product is 

 not, strictly speaking, a soap. Its particular importance in 

 our study is in connection with the saponification of the animal 

 and vegetable fats and oils. Industrially this is in the utiliza- 

 tion of fats in the manufacture of soap and glycerol. Physio- 

 logically it is in connection with the digestion of fats in the 

 animal body which will be considered again in detail when we 

 study animal digestion. 



Important Fats and Oils. — Fats differ from oils simply in 

 their physical properties, the former being solid at ordinary 

 temperature, while the latter are liquid. Chemically they are 

 of identical nature, being glycerol esters of the fatty acids, 

 differing from the waxes which are esters of monohydroxy 

 alcohols and fatty acids. They are not chemical individuals, 

 but are mixtures of several, oftentimes many, glycerol esters. 

 Individual fats and oils are characterized by the particular 

 acids present and by their relative proportions. The identifi- 

 cation and analysis of fats and oils is by the determination of 

 the physical properties of the fats themselves and of certain 



