602 



DETERMINATION OF SPECIFIC GRAVITY 



of instruments called hydrometers. The hydrometer is a 

 floating glass spindle, so constructed that it rests in the 

 liquid to be tested in an upright position. The spindle bears 

 a graduated scale on which the specific gravity, or its equiva- 

 lent at a given temperature (usually 60 F.), can be read at 

 a glance. In order to make the divisions on the scale as far 

 apart as possible and to thereby make the instrument most 

 sensitive and accurate, different hydrometer scales have 

 been devised and are used for different liquids. The 

 hydrometers used for milk are called lactometers, of which 

 there are two types, namely, the Quevenne 

 lactometer and the New York Board of Health 

 lactometer. 



Quevenne Lactometer. The Quevenne 

 lactometer is the one most generally used for 

 determining the specific gravity of milk and skim 

 milk. It consists of a spindle with a scale gradu- 

 ated from 15 to 40, a weighted bulb, and usually 

 a thermometer. The scale is divided into 25 

 equal parts, ranging from 15 to 40. Each divi- 

 sion is called a degree and every fifth division is 

 numbered on the scale. Each division corre- 

 sponds to one point of the third decimal of the 

 specific gravity scale. The Quevenne degrees 

 are converted into specific gravity by adding 

 1000 and dividing by 1000. 



.1 



Example. Quevenne Reading is 32. What is 

 the specific gravity? 



1000 + 32 

 1000 



= 1.032 specific gravity. 



The Quevenne lactometer is so constructed 

 that the scale records the correct degree at a 

 temperature of 60 F. At a temperature above 

 60 F. the reading is corrected by adding one- M< 4-. Board 

 tenth point to the actual reading for each degree of Hcaltn 



Pigf. 86. 



Quevenne 

 Lactometer 



Courtesy F. above 60. At a temperature below 60 F. de- 

 B?os nn co r duct one-tenth point for each degree F. below 60. 



Lactom- 



