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 1. If the ratio exceeds 1, 
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 
solids 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 cows’ milk and that of the 
