MILK INSPECTION 199 



the per cent, of fat multiplied by 1.2. For example, we have a 

 milk containing 4 per cent, of fat and a lactometer reading of 32, 

 to find the total solids : 



32 ■*- 4 = 8. 

 4 per cent. X 1.2 = 4.8 



12.8 per cent, of total solids. 



To find the solids-not-fat, divide the lactometer reading by 

 4, and, to the result, add the per cent, of fat multiplied by 0.2. 

 Thus, in the same milk as in the last example : — 



32-=- 4 = 8. 



4 per cent. X °- 2 = 0.8. 



8.8 per cent, of solids-not-fat. 



The percentage of casein and albumin increases — though not 

 in a proportionate degree — with the increase of fat, as shown in the 

 following table from Woll's Handbook, summarizing the analyses 

 of 2,400 samples of milk : 



Van Slyke gives the following formula for computing the 

 casein-content from the known fat-content in milks containing from 

 3 to 4.5 per cent, of fat : Subtract 3 from the per cent, of fat in 

 milk, multiply the result by 0.4, and add the result to 2.1. Hart 

 has shown that the proportion of fat to casein is not at all constant, 

 particularly in the milk of cows containing a large amount of fat. 

 In order to determine more accurately the percentage of casein in 

 milk the simple test recently given to the world by Prof. E. B. Hart 

 is of great value. 



The Hart casein test depends upon the following principles: 

 1. Construction of tube and scale whereby percentages of casein 

 in the milk are read directly. 2. Establishment of a proper volume 



