DETECTION OF ADULTERATION 
By far the larger part of the laboratory work on 
milk is for assistance in the sanitary control of the 
supply, and the analyses are principally directed 
to the detection of the ordinary forms of adultera- 
tions. The most important of these are: skim- 
ming, watering and use of coloring, thickening 
and preserving agents. Skimming and watering 
are detected by determining fat and total solids; 
from these data the solids not fat are calculated. 
For the ordinary purposes of milk control, fat 
can be estimated with quite sufficient accuracy 
by centrifugal methods. The total solids may be 
estimated directly as described on page 12, or 
calculated from the sp. gr. and fat as indicated on 
page 21. 
Judgment whether a given sample has been 
skimmed or watered depends in many cases upon 
the standard for whole milk. Some irregularity 
of standards for fat and solids not fat exists, and 
the opinion of the analyst will be determined, 
therefore, by the standard of the locality. In 
most cases the standard for fat is between 3 and 
4%, and that for total solids about 8.50%. 
As fat diminishes the sp. gr. of milk, and the 
41 
