228 



other milk solids cannot be radically changed by varying 

 the composition or the kind of feed. Feeding fat or giving 

 feed almost free from fat will not materially change the ccm- 

 position of the milk. Giving dry feed and restricting the 

 amount of water allowed the cow may decrease the quantity 

 of milk and slightly increase the proportion of total solids in 

 the milk. 



Lomparative composition of various kinds 0/ milk. * 



* Konig, Chemie der menschlichen, Nahrunj:s und Genussmittel, 3d ed., I, pp. 

 267-362. 



Determinixg THE Per Cent. of Fat in Milk. 



The most simple and practicable method for closely esti- 

 mating the per cent, of fat in milk is the one discovered by 

 Prof. Babcock, of Wisconsin. It is now universally called 



The Babcock Test. 



The necessary apparatus consists of a centrifugal machine; 

 graduated milk, cream, and skim milk test bottles; pipettes; 

 an acid measure; and sulphuric acid having a specific gravity 

 of 1.82. This apparatus may be obtained from any dairy 

 supply house. If the centrifugal machine has a diameter of 

 20 inches it should be capable of making not less than 700 

 revolutions per minute; if the wheel is 12 inches in diameter 

 it should make 1,200 revolutions per minute. The size and 

 speed of the wheel should be sufficient to give enough cen- 

 trifugal force to separate the fat. 



Procurinir the Sample ot Milk to be Tested.— The best 



