44 MILK 



lactose and ash, both of which are valuable data 

 in detecting added water. It is possible within 

 reasonable limits to indicate by the total solids 

 and fat whether a given sample has been watered 

 or skimmed. 



No relation exists between the refraction of 

 the (sweet) serum and the ash of the sour serum 

 (see page 66), therefore, if both these data are 

 below those of normal milk, added water is 

 positively indicated. 



The ratio of protein to fat in normal milk 

 is always less than i. If the ratio exceeds i, 

 skimming is indicated. If the protein-fat ratio 

 is less than 0.7, or the percentage of fat to 

 total solids is over 35, in samples having a low 

 serum refraction, these may be declared watered, 

 the refraction being not necessarily below the 

 minimum for all samples of known purity. 



The sp. gr. of the sweet serum or its total 

 soHds may be used as a datum in place of the re- 

 fraction; either will be a safe guide. 



Lowering of Freezing-point. — Several observers 

 have shown that watered milk has a lower freezing- 

 point than pure milk, and that the amount of 

 depression has a definite relation to the amount 

 of water added. One of the most recent state- 

 ments on the subject is by J. W. Leather, who 

 found the procedure very satisfactory for de- 

 tecting watering in qqws' milk and that of the 



