40 



MODERN METHODS OF TESTING MILK 



FIG. 17 — ELECTRIC CENTRIFUGAL MACHINE OF LATEST DESIGN 



Capable of 2,200 revolutions per minute. Made by the Inter- 

 national Instrument Co., Cambridge, Alass. 



centrifugal should run smoothly, without jar or trem- 

 ble, when going at full speed. 



Estimating speed of centrifugal tester. — In order 

 to cause separation of the most fat possible, the cen- 

 trifugal disc must move at a sufficient speed. The re- 

 quired number of revolutions depends upon the diame- 

 ter of the disc, to the edge of which the test bottles are 



