642 ANNUAL REPORT OF THE Off. Doc. 



such knowledge can one obtain the most proli table herd. Fre- 

 quently, in making butter, it is desirable to know the amount of 

 fat present in cream, also in the case of selling cream. Then, it is 

 necessai'y, i« butter-making, as previously pointed out (see section 

 28, p. 44) to determine the amount of acid in cream, frequently, also, 

 in selling milk, in order to ascertain the approximate age of milk 

 when it is received by the retailer. Another form of test that 

 dairymem have occasion to make, especially where they purchase 

 milk from other parties, is the estimation of solids in milk to find 

 out if the milk has been adulterated by addition of water or by 

 removal of fat. From these preliminary statements, it can readily 

 be seen how important a part the testing of milk and its products 

 plays in the problems which the dairyman constantly has before 

 him. 



77. The Babcock Test. 



The Babcock test is a method for determining the amount of fat 

 in milk and its products. It was devised in 1S90 by Dr. S. M. Bab- 

 cock, chief chemist of the Wisconsin Experiment Station. It is 

 probably not too much to say that, in giving to dairymen this simple 

 method of finding out how much fat a sample of milk contains. Dr. 

 Babcock made the greatest contribution to the real progress of 

 dairying ever made by any one man. There are other tests which 

 are, more or less, imitations of the Babcock test, but oone that, in 

 all respects, equals it. 



In general, this test is based on the action of strong sulphuric 

 acid upon milk-casein, albumin and milk-sugar, by w^hich the milk- 

 fat is released from the influence of these other compounds and 

 thus is free to collect in one separate mass. In order to hasten the 

 complete separation of the fat from the rest of the liquid, centrifugal 

 force is employed. 



78. Advantages aod Disadvantages of the Babcock Test. 



Before describing in detail the method of employing the Babcock 

 test, it is desirable to call attention to the special points of its merits 

 and demerits. 



(1.) Advantages. — (a.) The apparatus and materials are inexpen- 

 sive, both in respect to first cost and also cost of making tests, (b.) 

 The test is accurate enough for all practical purposes, giving the 

 real per cent, of fat within two-tenths of one per cent., comparing 

 most favorably with the most accurate laboratory methods, (c.) 

 The test is quickly made, requiring less than fifteen minutes, (d.) 

 The operation of the test is simple and easy. Only one chemical is 

 used and no chemical training or knowledge is necessary to operate it. 



