DETERMINATION OF FAT IN MILK AND CREAM. 179 



water to milk and then some easily soluble material to bring 

 the gravity back to the normal. Nevertheless, the determin- 

 ation of the gravity is of great assistance to the health officer 

 and physician. 



The use of the determination of the specific gravity in the 

 detection of added water is discussed in Chap. XI. 



Determination of fat in milk and cream, Fat being the most 

 variable ingredient of milk, it is only logical that all commer- 

 cial transactions relative to milk should be based upon the fat 

 content. It was this that gave the incentive to a number of 

 agricultural chemists twenty years ago, upon the establish- 

 ment of the agricultural experiment stations, to devise a simple, 

 rapid and accurate method for the determination of fat, which 

 could be intelligently used by those who either had no training 

 in chemistry or could not obtain access to a chemical laboratory. 

 The method now in common use is the one given free to the 

 public in 1890 by Dr. S. M. Babcock of the Wisconsin Agri- 

 cultural Experiment Station. The details of this adrnirable 

 test are hardly called for here ; for such, and other valuable 

 and useful data, the reader is referred to that excellent little 

 work, "Testing Milk and Its Products," by Farrington and 

 Woll (5). Also, to " Modern Methods of Testing Milk and 

 Milk Products," by Van Slyke (14). 



It may be said, however, in supplementing the directions 

 usually given for this test that the addition of 2 cc. of an 80% 

 solution of glycerin, as recommended by Holm (7), to the milk 

 in the test bottle just previous to adding the acid will insure 

 a clearer line of demarcation than is ordinarily obtained be- 

 tween the fat and water in the graduated neck of the bottle; 



Another modification which has proved useful in the testing 

 of cream by the Babcock method is that obtained by Kckles 

 and Wayman of the Dairy Department of the University of 

 Missouri. It consists in dropping a small quantity of amyl 

 alcohol colored with fuchsin or any red dye on top of the col- 

 umn of butter fat before it is read. Since it is lighter than the 

 fat, it floats on the surface. This removes the meniscus from 

 the surface of the fat to the top of the amyl alcohol, and leaves 

 a perfectly straight line across the top of the fat column. Thus 



