198 



MILK 



Publow's Method. 9 grams of milk with addition of a few 

 drops phenolphthalein solution are titrated with 0.1 normal so- 

 dium hydrate solution. Each cubic centimeter of the sodium hy- 

 drate solution neutralizes 0.1 per cent. acid. 



Marshall's Test. According to this method 9 grams of milk 

 are titrated with 0.1 normal sodium hydrate solution, the same as 

 in the previous test. The alkaline solution is contained in a bottle 

 with a buret and pressure bulb attached (Fig. 70) . The buret has 

 graduations of 0.2, and the alkali is furnished in dry form so that 



Fig. 69. Apparatus used in Manns' 

 test (Farrington and Woll). 



Fig. 70. Convenient apparatus for 

 acidity testing (Van Slyke). 



the contents of one package by addition of water make 1000 c.c. 

 0.1 normal sodium hydrate solution. 



Farrington's Alkali Tablet Method. This method has found 

 great favor because of its simplicity, enabling those inexperienced 

 in chemical work to make the test accurately. Each tablet con- 

 tains enough alkali to neutralize 0.035 gram lactic acid, and a 

 small amount of phenolphthalein is incorporated. If five tablets 

 are dissolved in enough water to make the solution measure 85 c.c. 

 each cubic centimeter of the solution used in neutralization repre- 

 sents 0.01 per cent, acid when 20 c.c. of milk are used. When 



