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 



xy s =9X800 2 , or 



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 the wheel revolves, 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 \ 5 -f=63 

 times a minute (see 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 know 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 care- 

 lessness, worn-out or dry bearings, 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 separation of fat and 



1 Private communication. 



