CHAPTER IV 



THE TESTING OF MILK 



MILK is so variable in composition, and so ea- 

 sily 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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