Principles of Milk Preservation. 



101 



Circumstances may arise that might lead to an error if 

 this method is blindly followed. It has been pointed 

 out that if milk is allowed to stand in rusty cans for 

 some time its acid content is diminished materially. Bid- 

 dick 1 has reported the following interesting observations. 

 The average of nine samples of milk brought to a factory 

 in clean cans contained .228% acidity, while that of nine 

 other patrons brought in rusty cans contained only .134% 

 acid. Milk kept in rusty cans is sure to contain large 

 quantities of bacteria, even though its acid content may 

 be low. 



& OunceBottle. Measure 



FIG. 18. Apparatus used in making rapid acid test. 



102. Making- the acid test. Fig. 18 gives the ap- 

 paratus necessary to make an approximate determination 

 of the acidity of the milk. A solution of the alkaline 

 tablets is first prepared by dissolving same in clean soft 

 water, one tablet for each ounce of water; thus eight 



1 Biddick, Hoard's Dairyman, July 30, 1897. 



