8 BUTTER-MAKING. 
When pure butter-fat is rapidly cooled, it solidifies into one 
solid mass; but if allowed to cool gradually, part of it solidifies, 
and part of it remains a liquid longer than other parts. This 
seems to indicate that some fats with a high melting-point 
separate out from the fats with a low melting-point. This 
behavior of pure butter-fat is not well understood, as it con- 
tradicts the now accepted theory that the different fats are 
in chemical combination with each other, rather than a me- 
chanical mixture of different glycerides of fat. 
Glycerides of Fat.—By this term we understand that the 
fatty acid radicals are in chemical combination with the glycerol 
(glycerine) radical, thus: 
Fatty acid radicals, 
Glycerol radical. C4H702 (Butyric) 
C3Hs5 } CigH3302 (Oleic) 
| CigH3302 (Stearic) 
The chemical formula for glycerine is: 
Hydroxyl] groups. 
Glycerol radical. OH 
C3Hs OH 
| OH 
Comparing these two formulas, their difference and simi- 
larity are easily observed, and the reason why the term “‘Gly- 
ceride of Fat” has been applied to such a compound is evident. 
Condition of Fat—Whether the fats in milk exist in chem- 
ical combination, or whether they exist as glyceride of butyrin, 
stearin, olein, etc.,in the form of a mechanical mixture, is a 
question in dispute. If they exist in the latter form, the com- 
position of the different fats must be thus: 
Butyrin. Olein. Stearin. 
C4H702 CigH3302 CigH3502 
C3Hs {CsH702 C3Hs jCisHssO2  C3Hs } CigH3502 ete., 
{ C4H702 { CigH3302 CigH3502 
