184 Biological Chemistry. 



B. Unsaturated acids of the oleic or acrylic series, C n H 2n _ 2 2 

 (with one double bond) 



C J8 H 84 2 .... Oleic acid. 



.... Elaidic 



.... /50-oleic 



CJIvfit .... Erucic 



.... Brassidic 



C. Acids of the linolic series, C n H 2n _ 4 2 (with two double 

 bonds). The chief of these is linolic acid, C J8 Hj 2 2 . 



D. Acids of the linolenic series, C n H 2n ^0 2 . 



E. Certain hydroxy acids of the general formula C ft H 2n - 2 3 , of 

 which the best known is ricinoleic acid, 



Now, as already stated, a natural fat generally yields on 

 hydrolysis a mixture of fatty acids. It might be thought 

 possible that a fat could be characterized by isolating these 

 acids. The obstacle to a method of this kind is the fact 

 that the acids obtained are generally so similar in their 

 properties that no method exists for separating them from 

 one another quantitatively. Indirect methods are, there- 

 fore, employed for the analysis of fats, which consist in 

 the determination of certain chemical constants. The 

 chief of these are the following : 



(a) The Saponification Value. The amount of potassium 

 hydroxide which is necessary to neutralize with the acids 

 set free by hydrolysis will be influenced by the molecular 



