FROM THE PRACTICAL VIEWPOINT 



jackets of asbestos, cork or felt, or a surround- 

 ing tank of water may be provided, as in Fig. 25. 

 By means of the insulation, if properly applied, 

 the heat will be retained and the milk as it flows 

 from the tank will have a temperature but little 

 below that at which it enters. When the hot water 

 insulation is used, as in Fig. 25, the initial tem- 

 perature of the milk may become somewhat in- 

 creased during the holding period. This addi- 

 tional heating, it can be seen, has a tendency 

 to cause the milk which may enter the tank below 

 the average temperature to become heated and rise 

 toward the top of the tank, thus increasing the 

 time for which it is held. As a matter of fact, the 

 water-insulated tanks have shown a good percent- 

 age of holding time as compared with the filling 

 time when the color test has been applied. The 

 test of their efficiency as measured by the destruc- 

 tion of the bacteria contained in the milk is also 

 good. 



This Park type of holding tank has been some- 

 what modified by various manufacturers in this re- 

 spect, namely, by introducing the milk at the bot- 

 tom and allowing it to flow out at the top instead 

 by the reverse method of flow. When the inlet 

 121 



