183 
The saponification of a nentra. tut yields a perfectly definite com- 
pound. This saponification takes place according to the following reac- 
tion for an ester with three molecules of acid combined with the radicat 
of a trihydric alcohol: . 
Ri 
CsHs<g Re+3KOH =C3Hs(OH)3s+ K(Ri'+ Re+ Ra) 
R3 
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(IKOH) 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 5 equals the molecular weight, 
782.7. The molecular weight of butyrin C,H,(C,H,O); 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.t 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 Pairy Chemistry, page 537. 
