62 MILK AND DAIRY PRODUCTS PART 



collects below the milk. When all the samples have been 

 treated in this way, the contents of each bottle is mixed by 

 giving the bottle a slow rotary motion, the neck being held 

 in the hand. When all the casein, &c , has dissolved, the test- 

 bottles are put into a special centrifuge, care being exercised, 

 as in the " lactocrite " method, to get an even balance by 

 placing the bottles opposite to each other if there are not 

 enough to fill the centrifuge. If there are an unequal number 

 of test-bottles, one should be filled with water to make up the 

 required number. This rule applies to all methods where the 

 centrifuge is used, so need not be repeated each time. 



FIGS. 25a, 256. Babcock's Milk-testing Apparatus. 



When the test-bottles are in the centrifuge, boiling water is 

 poured into the latter until the level of the water is up to the 

 height of the vertically standing test-bottles. It is better, 

 however, to use steam for heating the centrifuge. The cover is 

 then put on the centrifuge, and the latter whirled for 6 or 7 

 minutes at a rate of 700-1,200 revolutions per minute. 

 There are various makes of centrifuges to be obtained, either for 

 turning by hand or power. 



After whirling in the centrifuge the test-bottles are filled 

 with boiling water, the arrangement shown in Fig. 25i being 

 handy for the purpose. The water is boiled in the conical 



