6 FATS, OILS, AND WAXES 



three hydroxyl groups (OH) instead of only one, may be 

 expressed by the following equation : — 



3H2O 



CH2OH C17H35COOH C17H35COOCH2 



CHOH + C17H35COOH = CJ7H35COOCH + 



CH2OH Ci-HgeCOOH Cj^Hg^COOCHjj 

 Glycerol Stearic acid Tristearyl glycerol 

 or tristearin 



the resulting compound tristearin also being an ester. 



The naturally occurring fats are mixtures of similar esters 

 of glycerol with other fatty acids such as palmitic C15H31COOH 

 or butyric C3H7COOH acids, or with the unsaturated acid 

 oleic acid Q^HggCOOH. 



A wax, on the other hand, is an ester of a monohydric 

 alcohol as illustrated by the equation : — 



C1BH31COOH + C3oHeiOH = CisHgiCOOCgoH^i+H^O 

 Palmitic acid Myricyl Myricyl palmitate 



alcohol 



myricyl palmitate being the chief constituent of beeswax. 



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 : — 



* These acids do not occur in fats. 



