CHAPTER, III. 
THE TESTING OF MILK. 
MILK is so variable in composition, and so ea- 
siuly adulterated, that it frequently becomes of great 
importance to be able to ascertain with a fair de- 
gree of accuracy the composition of any given 
sample. 
HISTORY OF MILK TESTS. 
Gravimetric analysis.—The most accurate way to 
determine the composition of milk is by means of an 
exact chemical analysis. The constituents of milk 
which it is most frequently necessary to determine 
are the total solids and fat. The total solids are 
determined by drying an accurately weighed portion 
of the milk at the temperature of boiling water 
until it no longer loses weight. The residue is the 
total solids, and its weight, divided by the weight 
of the original amount taken, will give the percent- 
age of total solids. The fats may then be deter- 
mined by extracting the residue with anhydrous 
ether until nothing more is dissolved, and then 
evaporating the ether and weighing the resulting 
‘fat directly. Various forms of apparatus for mak- 
ing these determinations have been devised by vari- 
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