PHYSICAL AND CHEMICAL EXAMINATION OF MILK 



199 



17.5 c.c. of milk are used the solution is made up by dissolving 

 five tablets in 97 c.c. of water. This is equal to a 0.02 normal 

 alkali solution, and each cubic centimeter of the solution repre- 

 sents 0.01 per cent, of acid when 17.5 c.c. of milk are used 

 (Fig. 71). 



Spillman's Modification of Farrington's Test. Five tablets 

 are dissolved in "Spillman's acid test cylinder" (Fig. 72) filled 

 with water to the 8 mark. The solution is placed in a well-closed 

 container (fruit jar). In a cup is placed 17.6 c.c. of the milk to be 

 tested and the tablet solution added until the pink color is perma- 



Cylinder 



Fig. 71. Apparatus used for determining 



rington and 



G^lmder 



; the acidity of cream or milk (Far- 

 Woll). 



nent. The contents of the cup are then poured into the Spillman 

 cylinder and the mark at the surface noted. The figure expresses 

 the acid in tenths per cent. 



The acidity of milk is frequently expressed in degrees. Unfor- 

 tunately, there is no general agreement as to a standard degree. 

 Soxhlet's degrees represent the number of cubic centimeters of 

 one-fourth normal sodium hydrate solution necessary to neutralize 

 100 c.c. of milk. Others take the number of cubic centimeters of 

 one-tenth normal solution required to neutralize 25 or 50 c.c. of 

 milk. Uniformity of expression is best accomplished, perhaps, by 

 using lactic acid as a basis. This is obtained by multiplying the 



