58 Testing Milk and Its Products. 



The speed at which testers of different diameters should be 

 run to effect a complete separation has been calculated by Prof. 

 C. L. Beach in the following manner. 1 The same standard as 

 before is taken, viz., 800 revolutions for an 18-inch tester (radius 

 9 inches) ; then if x designate the radius of the tester and y the 

 speed required, we have 





V 



The figures obtained by the use of this formula are similar 

 to those given in the preceding table. 



67. To find the number of turns of the handle corre- 

 sponding to the number of revolutions made by the 

 wheel, the handle is given one full turn, and the number 

 of times which a certain point or part of the wheel re- 

 volves, is noted. If the wheel has a diameter of 20 

 inches, and revolves 12 times for one turn of the handle, 

 the latter should be turned M>==63 times a minute (see 



12 



table), or about once every second, in order to effect a 

 maximum separation of fat. By counting the number of 

 revolutions, watch in hand, and consulting the preceding 

 table, the operator will soon note the speed which must 

 be maintained in case of his particular machine. It is 

 vitally important that the required speed be always 

 kept up ; if through carelessness, worn-out or dry bear- 

 ings, low steam pressure, etc., the speed is slackened, the 

 results obtained will be too low ; it may be a few tenths, 

 or even more than one per cent. Care as to this point 

 is so much the more essential, as the results obtained 

 by too slow whirling may seem to be all right, a clear 



1 Private communication. 



