52 



Dairy Bacteriology. 



acid in milk can be made accurately by titration with 

 standard solutions of alkali, or more readily, in general 

 work, by employing the Farrington alkaline tablet, which 

 is a combination of a definite amount of standard alkali 

 and an indicator (phenolphthalein). It is possible by the 

 use of the tablet solution to make as accurate determina- 

 tion of acidity as with the usual standard solutions em- 

 ployed in the laboratory, but the method may also be 

 used rapidly in such a way as to give an approximate deter- 

 mination of acid. This modification is very serviceable at 

 the weigh-can or intake where it is necessary to pass judg- 

 ment very quickly on the quality of the milk. 



Fia. 15. Apparatus used in making rapid acid test. 



Making the acid test Fig. 15 gives the apparatus nec- 

 essary for this rapid testing of the acidity of the milk. A 

 solution of the alkaline tablets is first prepared by dissolv- 



