214 MILK HYGIENE 



then placed at the zero point and the reading made with 

 the other. Experience by analysts in various parts of 

 the world has shown that with properly graduated 

 bottles the results are reliable. As a rule, they do not 

 differ more than 0.1 per cent, from those obtained by 

 the Adam's jjrocess, and are generally even closer. 



" The mixture of fusel oil and hydrochloric acid 

 seems to become less satisfactory when long kept. It 

 should be clear and not very dark in color. It is best 

 kept in a bottle provided with a pipette, which can be 

 filled to the mark by dipping. Eigid accuracy in the 

 measurement is not needed. ' ' 



The Bahcock method or " test " is, in America, by 

 far the best known and most used centrifugal test for fat 

 in milk. The Leffmann-Beam and the G-erber tests are, 

 however, being used more and more, on account of the 

 shorter time required. 



In careful hands, the Babcock test is very accurate. 

 Small or large outfits, the centrifuges to be driven by 

 hand or power, may be purchased from any dairy sup- 

 ply establishment. The test is made by placing in the 

 special test bottle 18 grams (17.6 c.c.) of milk. To this 

 is added, from a pipette, burette or measuring bottle, 

 17.5 c.c. commercial sulphuric acid of a specific gravity 

 of 1.82 to 1.83. The contents of the bottle are carefully 

 and thoroughly mixed by a rotary motion. The mixture 

 becomes brown and heat is generated. The test bottle is 

 now placed in a properly balanced centrifuge and 

 whirled for five minutes at a speed of from 800 to 1200 

 revolutions per minute. Hot water is then added to fill 

 the bottle to the lower part of the neck, after which it 

 is again whirled for two minutes. Now, enough hot 

 water is added to float the column of fat into the grad- 

 uated portion of the neck of the bottle, and the whirling 

 is repeated for a minute. 



