154 lULINOIS STATE DAIRYMEN'S ASlSOCIATION. 



in the test bottles. Both the milk and acid should be so poured 

 into the test bottle that it will follow down the side of the 

 test bottle and form a distinct layer underneath the milk. 

 The test bottle should be given a rotary motion so as to mix 

 the milk and acid. This mixing should be completed at once 

 and not left half done. Inaccurate tests are often caused by 

 a failure to completely mix the last eighth of an inch of acid 

 in the bottom of the test bottle. 



When the liquids are thoroughly mixed the test bottle 

 should be whirled in the tester for at least five minutes at a 

 speed varying from 600 to 1,200 revolutions per minute, ac- 

 cording to the diameter of the machine. The small machines 

 require a greater speed than the large ones. After the first 

 run of five minutes fill the test bottle up to its neck with hot 

 water, and whirl it again at full speed for one minute; then 

 fill the test bottle to within about one-half inch of the top of 

 the neck with hot water, and complete the separation of the 

 fat by one more whirling about one minute. 



If these directions are carefully followed and the separ- 

 ated fat in the neck of the test bottle is of a golden yellow 

 color the acid is of the proper strength. If the fat is light 

 colored or white it generally indicates that the acid is too 

 weak, and a dark colored fat with a layer of black stuff be- 

 neath it often shows that the acid is too strong. Satisfactory 

 tests can often be made by using a little more than the 

 specified amount of weak acid. 



The strength of the acid (1.82 sp. gr.) as used in the test 

 is not sufficient at ordinary temperatures to appreciably dis- 

 solve the fat, but a variation in strength of the acid or tem- 

 perature of the milk influences the intensity of the action of 

 the acid on the fat, and the difference in the intensity of this 

 action is shown by the color of the fat. 



This action of sulphuric acid on the color of the fat can 

 be easily demonstrated by any one familiar with the Babcock 

 test, by the following experiment: 



First — From one sample of milk measure the usual quan- 

 tity for testing into each of three test bottles — A, B and 0. 

 Place A in ice water, C in warm water and leave bottle B at 

 the ordinary temperature. After the milk in one bottle has 



