16 



ANALYTICAL PROCESSES. 



The simplest method of determining specific grav- 

 ity is by the laciodensimeUr, a. delicate and accurately 

 graduated hydrometer. The instrument must be im- 

 mersed carefully so as not to wet the stem above the 

 point at which it will rest. The reading should be 

 made at the actual level of the liquid, and not at the 

 point to which it is drawn by adhesion to the glass. 



The indications furnished by the lactodensimeter are 

 sufficiently accurate for most purposes, but its employ- 

 ment necessitates a considerable amount of the sample. 

 More accurate determination can be made by the 

 Westphal balance. This is 

 a delicate steelyard with a 

 counterpoised plummet, dis- 

 placing 5 c. c. The plum- 

 met being immersed in the 

 milk the equilibrium is re- 

 stored by weights, the value 

 of which can be directly ex- 

 pressed in figures for the 

 specific gravity. 

 The principal of the Westphal balance may be ap- 

 plied by means of the ordinary analytical balance and 

 a plummet. The latter may conveniently consist of a 

 short thermometer, or a thick glass rod, having a bulk 

 of from S to lo c. c. It is suspended from the hook of 

 the balance by a fine platinum wire and its weight as- 

 certained. It is then immersed in distilled water at 

 6o°F. and the loss in weight noted. The figure so ob- 

 tained is the weight of a bulk of water equal to that of 



