THE PASTEURIZATION OF MILK 



ever, a seven-tank holder has a forty-minute se- 

 quence, which is reduced by two-sevenths, we have 

 a holding time of but twenty-eight and four- 

 sevenths minutes, and so on as the number of 

 tanks decreases. 



A modification of the valve system, shown in 

 Fig. 23, is now provided by the manufacturers of 

 this machine. A valve exactly similar in principle 

 to that shown in Fig. 22-B is made use of. All 

 tanks fill and empty from the bottom, thus avoid- 

 ing foam and reduring the danger of by-passing 

 the milk. 



All the types of holders already described are 

 being used with very satisfactory results. To 

 summarize the points which should be observed 

 in either buying or supervising the operation of 

 holders of this character: 



First. Any serious loss of heat should be pre- 

 vented by complete insulation of all tanks and 

 pipes in which the heated milk is held. Of 

 these insulations, the hot-water jacket is the most 

 expensive and perhaps the best. There is a 

 question whether the added expense secures 

 enough added efficiency to render the expenditure 

 wise. 



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