190 
On the other hand, the iodine number is lowest in the fat soluble in 
alcohol and highest in the fat of the soft portion. 
The figures in the above table show the influence of the constants on 
the melting point of butter fat. The portion of fat insoluble in alcohol 
and the original fat from which the above portion was taken show a de- 
cidedly higher iodine number than the portion soluble in alcohol. If the 
melting point depended solely on the iodine number, the melting point of 
the fat insoluble in alcohol and of the original butter fat would be dis- 
tinctly lower than the melting point of the portion soluble in alcohol. 
Table VII shows that this is not the case. The melting point of the por- 
tion insoluble in alcohol and of the original butter fat is a great deal 
higher (19.1° C. and 16.6° C., respectively, higher) than the melting point of 
the fat soluble in alecohoi. The only factor to which this fact can be attrib- 
uted is the high Reichert-Meissl No. in the case of the fat soluble in 
alcohol, as compared with the low Reichert-Meiss] No. of the fat insoluble 
in alcohol and of the original butter fat. These results make it perfectly 
clear that the softness or hardness (melting point) of butter fat is de- 
pendent to a great degree on the per cent of soluble fatty acids present. 
This table further shows, as stated in the previous chapters, that 
butter fat is a mixture of triglycerides of different fatty acids. The soft 
portion is the result of mechanical separation at different temperatures. 
It, therefore, contains more giycerides combined with acids of low melting 
points including oleic and soluble acids. Turthermore, the fat soluble in 
alcohol represents glycerides of acids soluble in aleohol. Since it is known 
that some of the glycerides of the soluble acids are soluble in alcohol, 
we can assume that some of the molecules in butter fat are made up of the 
glycerides containing a larger proportion of the soluble acids than others. 
CONDITIONS AFFECTING THE COMPOSITION OF BUTTER FAT. 
The composition of butter fat varies with the season of the year. <A 
series of analyses of butter fat of butter made during each of the twelve 
months of the year, yielded the results summarized in Table VIII. 
The results in Table VIII show that the Reichert-Meiss] number was 
lowest in October, increasing steadily until it reached its maximum in 
March. After March it dropped abruptly, holding about its own till July, 
then taking a second drop and declining slightly toward October. 
