12 



DAIRY LABORATORY GUIDE 



to balance the machine. Oil tester and see that it 

 runs steadily. Revolve at listed speed for three 

 minutes. Then fill to the lower part of the neck 

 with hot water 150° to 200° F. Whirl again for two 

 minutes and fill to the upper part of the graduated 

 neck. Then whirl for one minute to a minute and 



Fig. 15. — Combined Acid 

 Bottle and Pipette 



a half, and read result at once before fat column 

 begins to cool and shrink. Read the per cent of fat 

 at about 120° F. If warmer it will be too high; if 

 colder too low. Butter fat solidifies at 80° F. 



The speed of the tester required to produce the 

 necessary centrifugal force depends upon the diameter 

 of the wheel containing the cups. The less the diam- 

 eter the greater the number of revolutions. 



