ACIDS OCCURRING IN FATS 7 



The classification and identification of fats is based upon 

 the acids which they contain. Thus it is found that whereas 

 beef suet and mutton fat consist chiefly of esters of the higher 

 fatty acids, such as palmitic and stearic acids, butter contains 

 a considerable quantity of the lower members of this same 

 fatty series such, for example, as butyric, caproic, caprylic and 

 capric acids ; these acids, which are low boiling liquids readily 

 volatile with steam, are known as volatile fatty acids and their 

 presence or absence in a given sample of fat may be used for 

 characterizing the fat. Thus, for example, the estimation of 

 the amount of volatile fatty acid serves to distinguish genuine 

 butter from its substitute margarine, which is relatively poor 

 in volatile acids and contains chiefly higher fatty acids. 



The more important members of the fatty acid series are 

 given in the following list : 



It should be noted that these acids all conform to the 

 general formula for the fatty acids, C n H 2n O^, in which " n " may 

 have any value, odd or even, but only those in which " n " is an 

 even number are found to occur naturally in fats ; the alleged 

 occurrence in natural fats of acids with an uneven number of 

 carbon atoms has in every case, so far recorded, been refuted on 

 careful re-examination. 



It appears probable, moreover, that all naturally occurring 

 fatty acids have a straight and not a branched carbon chain, 

 so that it is open to question whether the &0-butyl acetic acid 

 which is said to have been found in fats was not, in reality, 

 normal caproic acid of the formula CH 3 (CH 2 ) 4 COOH. 



* These acids do not occur in fats. 



