THE TESTING OF MILK AND CREAM 125 



be revolved once. In this way the acid washes the neck free 

 from particles of cream and curd. 



After the acid is added the bottle should be shaken carefully 

 by giving it a rotary motion. Care should be taken not to spill 

 any of the contents. In case of spilling, the test should be 

 rejected and made over. 



Whirling and adding ivater 



The bottles are now ready for the Babcock centrifuge. If 

 there are not enough test bottles to fill all the pockets in the 

 tester, the bottles should be so arranged as to balance the 

 machine. Whirl for five minutes at the proper speed; one 

 thousand revolutions per minute for a tester with a twelve- 

 inch diameter wheel and 800 revolutions a minute for a tester 



Fig. 30, — Water bath for bringing test bottles to proper temperature before 



reading. 



with an eighteen-inch diameter wheel. Fill to the bottom of 

 the neck of the bottles with hot, soft water, whirl for two 

 minutes: fill to about the 45 per cent mark with hot, soft 



