183 



The saponification of a neaira, ..-it yields a perfectly definite com- 

 pound. This saponification takes place according to the following reac- 

 tion for an ester with three molecules of acid comhined with the radical 

 of a trihydric alcohol : 



|-Ri 

 CsH J R 2 + "3KOH = C 3 Hs(OH)3+ K(Ri;+ R 2 -f Rs) 



Lr 3 



The molecular weight of the triglyceride is calculated as follows : 

 Determine the per cent of KOH required to saponify the fat, and divide 

 the molecular weight of 3 (KOH) by the per cent thus obtained, or mul- 

 tiply the saponification equivalent by three. 



Thus, from the figures in Table VII the saponification equivalent of 

 the portion soluble in alcohol was found to be 216.5. This multiplied by 

 3 is 649.5. This equals the molecular weight of the triglyceride. 



The saponification equivalent of the portion not soluble in alcohol 

 was found to be 260.9 ; this multiplied by 3 equals the molecular weight. 

 7S2.7. The molecular weight of butyrin C 3 H 5 (C 4 H ? 0) 3 is 302, while the 

 molecular weight of the triglycerides of the soft portion is 649.5. 



The fact that only 1 per cent of the butter fat was dissolved in cold 

 alcohol shows clearly the absence of tributyrin, otherwise the per cent 

 of alcohol-soluble fat would be higher. The soft portion must, therefore, 

 be made up of mixed glycerides of the acids found in butter fat, the acids 

 having a low melting point and a low molecular weight predominating. 



FRACTIONAL SEPARATION OR CRYSTALLIZATION OF BUTTER 



FATS. 



The same condition presents itself if butter fat is subjected to frac- 

 tional separation. When butter fat is exposed to a temperature below the 

 melting point of the harder glycerides, the softer glycerides separate from 

 the harder glycerides. When this process is repeated by lowering the 

 temperature after each separation, a separation can be effected whereby 

 the constants differ widely from the original mixed glycerides. 1 Table III 

 shows the variation of the constants of the fats thus separated. The but- 

 ter used in this experiment was made in March. 



Richmond Dairy Chemistry, page 



