TESTING DAIRY PRODUCTS BY THE BABCOCK TEST. 93 



12 per cent total solids, unless it has been diluted. Milk con- 

 taining less than 9 per cent solids not fat is suspicious, and a 

 sample containing much less than 8.5 is probably watered. 

 When a standard is adopted, the only course to pursue is to 

 consider all milk falling below this standard adulterated. If 

 the milk is not up to the standard, it matters not whether it is 

 from poor cows or is diluted after milking, the results are the 

 same. 



It is necessary, therefore, in order to detect adulteration to 

 determine both the fat and the other solids. For the determin- 

 ation of the former, one has recourse to the Babcock test, and 

 the solids not fat can be quite readily and accurately estimated 

 (from the specific gravity and per cent of fat) by means of a 

 formula. The specific gravity of whole milk at 6o° F. varies from 

 1.030 to 1.034. This means that when a certain volume of 

 distilled water at 6o° F. weighs just 1,000 pounds the same 

 volume of milk will weigh 1,030 to 1,034 pounds. 



The solids not fat, namely, the casein, albumin, milk sugar 

 and mineral matter, are constituents of milk that are heavier 

 than water and therefore cause its greater weight. On the 

 other hand the fat is lighter, consequently the abstraction of 

 fat increases the specific gravity, and the addition of water 

 decreases the specific gravity, so one can readily tell by these 

 two tests whether the milk has been skimmed or diluted with 

 water. For example, suppose a sample of whole milk con- 

 tains 4.2 per cent fat, and has a specific gravity of 1.032. If 

 this milk were diluted one-half with water, it would contain 

 2.1 per cent fat and have a specific gravity of about 1.016, while 

 if it were partially skimmed to contain about 2.1 per cent fat 

 its specific gravity would be increased to about 1.0345. 



The Lactometer. The lactometer is an instrument for taking 

 specific gravity and is sufficiently accurate for practical pur- 

 poses. There are several kinds in use at the present time, all 

 of which are made on the same general principle, viz.: A nar- 

 row stem attached to an elongated bulb, weighted at the bottom 

 so that it will maintain an upright position when floating in 

 the milk, with the stem, which is graduated, partially sub- 

 merged. The mark on the stem to which it sinks shows the 

 specific gravity. The instrument for which the formula and 



