PAT Ml TAB01 l-\! 



<»II (hydroxyl) groups, the resulting ester called triglyceride is neu 

 trnl ful. Tripalmitin has the formula: 



CH OOCC II 

 CH OOCC ii 

 CH, OOC-C H 



By boiling neutral fats with alkali the fatty acid radicles are split «»ff 

 as soaps, 1 « • ; i \ i 1 1 >_r the glycerol. This process is called saponification, and 

 it may be effected in man} other ways, as for example by heating with 

 steam or by the action of special enzymes called lipases, which are widely 

 distributed in plants and animals. 



The natural fats are usually a mixture of triglycerides, ;m<l their dif- 

 ferences in properties are dependent upon the relative amounts of fatty 

 acids present. The three mbsl important in animal fats arc tripalmitin, 

 t ristearin and triolein. Tt is essential in the study of fa1 metabolism that 

 we should know the mosl important methods by which the proportion of 

 fatty acids present in a mixed fat is determined. These methods are as 

 follows : 



1. The melting point. Olein is liquid at 0° C; palmitic acid melts at 

 fiL'.U C: and stearic at (>!».:! ('. The solidity of animal fats depends 



the proportion of olein. palmitin and stearin present. Mutton fat, for ex- 

 ample, is much stiffer than pig fat because it contains less olein and mere 

 stearin. The melting points of fats from different parts of the body may 

 also vary. 



2. Tin acid unmix r indicates the amount of free fatty acid mixed with 



the fat, and is determined by titrating a solution of a weighed quantity 

 the fa1 in alcohol with a N L0 alcoholic solution of K«>1I. phenolphtha- 

 lein being used as indicator. 



:!. '/'!■• saponification valm indicates the total amount of fatty acid 

 present, both that which is free and that combined with glycerol. It is 



determined by heating a weighed amount of fat with an exactly known 



amount of alcoholic K(»ll determined by titration with standard acid . 

 After saponification is complete, titration of the mixture shows how much 

 alkali has 1 n used to combine with the fatty acid. This is the saponi- 

 fication value. 



I //. ester valm indicate- the amount of fatty acid combined with 

 glycerol, and is obtained by subtracting the acid value from the saponi- 

 fication value. 



Besides these there are two values, known as the iodine and the Reichl 



Bfeiasl values, that are of importance because they depend on certain ci 

 iwti rist ■/" fatty-acid radu 



