THE PASTEURIZATION OF MILK 



readily seen that each tank will be emptied after 

 the milk has been held in the tank during the time 

 required for the shaft to make a complete revolu- 

 tion. By properly gearing the mechanism which 

 operates the shaft it can be seen that the time of 

 holding can be fixed at will for any period de- 

 sired. A little thought, however, will make it clear 

 that the actual holding time will not equal the time 

 required for the shaft to make a complete revolu- 

 tion, since approximately one-eighth of this time 

 is occupied in filling each tank, and one-eighth is 

 required to discharge each tank. In order to ar- 

 rive at the actual minimum time for which we can 

 be sure all the milk is held, we must reduce the 

 time of revolution by one-fourth, or 25 per cent. 

 Thus if it is desired to hold the milk for thirty 

 minutes, it is necessary that the time of revolution 

 of the operating shaft be forty minutes, which 

 reduced by 25 per cent, equals thirty minutes, the 

 actual holding time. 



It is also necessary to make sure that the dis- 

 charge pipes are completely closed before the milk is 

 allowed to enter through the inlet pipe into any tank. 

 Otherwise some milk may pass out of the holder 

 without being held for any definite length of time. 

 96 



