EXAMINATION OF MILK SERUM 



79 



whether a sample is adulterated by the addition of water, or is 

 merely abnormal in composition. The principal constituents 

 of the serum are milk sugar and mineral matter, and a deter- 

 mination of these on the milk direct affords the same evidence as 

 an indirect examination of the serum, but as the latter can be 



TABLE XXXV 

 RELATION OF REFRACTIVE INDEX TO SPECIFIC GRAVITY 



(LYTHGOE) 



performed more expeditiously, it is often included in the rou- 

 tine examination of milk. The serum is prepared by adding 

 2 c.cms. of 25 per cent acetic acid (Sp. Gr. 1.035) to 100 c.cms. 

 of sample at a temperature of 20 C., covering with a watch- 

 glass and heating to 70 C. for twenty minutes. After cooling 

 in ice water for ten minutes, the curd is separated by filtration 



