PRODUCTION, COMPOSITION AND CHARACTERISTICS 19 



Acidity Test* — The acidity, or sourness, of milk or 

 cream, which depends upon the amount of lactic acid 

 developed in it, may 

 be tested by a liquid 

 normal alkali or by the 

 Farrington Alkaline 

 Tablets, a solution of 

 which added to sour 

 milk neutralizes the 

 acid. A few drops of 

 an indicator, Phenol- 

 pthalein, added to the 

 milk, turns it pink 

 when all the acid has 

 been neutralized, and 

 the amount of alkali 

 solution used shows 

 the percentage of acid 

 in the milk. This is 

 quite important in 

 preparing ^ ' starters ' ' 

 for ripening the cream 

 in butter making or 

 milk in cheese mak- 

 ing, and in the manufacture of 

 milk," etc. 



* The Acid Test depends upon what in the laboratory is called "titra- 

 tion" and makes use of a "burette," a long, graduated measuring tube 

 provided with a pinch-cock. This burette is filled with an alkali solu- 

 tion of known strength, usually a "tenth normal" solution of caustic 

 soda. A certain amount of the milk to be tested is measured off into 

 a glass or a white porcelain cup. As a 17.6 c.c. pipette belonging to the 

 Babcock test usually is at hand, that may be used for this purpose. 

 A few drops of an Indicator is added to the milk and under constant 

 stirring the soda solution is allowed to drip into it until suddenly it turns 



The acidemeter 



Commercial Butter- 



