30 



DETERMINATION OF SPECIFIC GRAVITY OF MILK. 



For exact work the specific gravity of milk is deter- 

 mined by comparing the weight of a volume of milk with 

 that of an equal volume of pure water under controlled- 

 temperature conditions. For inspection work an instru- 



/ \ 



I 



FIG. 27. Westphal balance. 



FIG. 28. Types of ordinary 

 lactometers. 



ment known as the Westphal balance or the special 

 lactometer described in Bulletin 134 of the Bureau of Ani- 

 mal Industry, United States Department of Agriculture, 

 is sufficiently accurate. 



Westphal balance. This instrument (fig. 27) consists of a 

 pivoted beam graduated on one arm and bearing a plum- 



