FROM THE PRACTICAL VIEWPOINT 



U-pipe be provided with a vent at the upper end, 

 otherwise a syphon will be created and the milk 

 will all be rapidly drained from the tank. 



In plants where a large amount of milk is pas- 

 teurized, and there is therefore a rapid flow, it is 

 necessary to install more than one of these tanks 

 in series, and in some instances three and four 

 tanks are so installed, each succeeding tank being 

 a little lower than the one before it, and the valves 

 so arranged that the milk-flow is from one to the 

 other through the entire series. This also helps 

 to equalize any uneven temperature which may oc- 

 cur as the milk is discharged into the first tank. 



With all these precautions to insure a steady 

 and even flow, it is never safe to assume that the 

 holding time is correct unless a test is made. Only 

 two feasable means of so testing the tanks have 

 developed. One is the color test and the other 

 the temperature test. Neither are absolutely ac- 

 curate, but are sufficiently so for practical pur- 

 poses. 



In the color test, the tanks are filled with water, 



heated to the same temperature as is the case when 



milk is pasteurized. The time of filling having 



been observed, a solution of some intense color, 



115 



