Testing the Acidity of Milk and Cream. 121 



number of bacteria and spores not destroyed by pasteur- 

 ization than does milk giving a low acid test (126); the 

 acidity test may therefore be used to advantage for the 

 purpose of selecting milk best adapted for pasteurization, 

 as well as such as is to be retailed or used in the manu- 

 facture of high-grade butter and cheese. 



& Ounce Bottle. "Measure 



FIG. 43. Apparatus used for rapid estimation of the acidity of appar- 

 ently sweet milk or cream. 



In distinguishing milk fit for pasteurization purposes 

 from that which is doubtful, an arbitrary standard of 

 two-tenths of one per cent, of acid may be taken as the 

 upper limit for milk of the former kind. The appara- 

 tus used in making this test is shown in the accom- 

 panying illustration (Fig. 43), and consists of a white 

 teacup; a four-, six-, or eight-ounce bottle, and a No. 10 

 brass cartridge shell, or a similar measure. A solution 

 of the tablets in water is first prepared, one tablet being 



