Relation of Quevenne to Ordinary Lactometer 81 



a specific gravity of 1.029 upon the ordinary hy- 

 drometer. The accompanying sketch (see opposite 

 page) shows the relative values of the degrees upon 

 the ordinary hydrometer, the ordinary lactometer and 

 the Quevenne lactometer. With the Quevenne lac- 

 tometer the specific gravity of the milk can be at 

 once read, a degree upon this scale being equivalent 

 to one degree of specific gravity. Since 100 degrees 

 upon the ordinary lactometer indicate a specific gravity 

 of 1.029, the specific gravity of any ordinary lactometer 

 reading may be obtained by multiplying the reading by 

 .29, dividing by 1,000 and adding 1. Twenty-nine Que- 

 venne degrees are also equivalent to 100 ordinary de- 

 grees, so that Quevenne readings may be changed to the 

 ordinary readings by dividing by .29, and ordinary 

 readings may be changed to Quevenne readings by 

 multiplying by .29. 



The relative density of milk varies with its tem- 

 perature, so that a hydrometer is only correct at one 

 given temperature. Most hydrometers are graduated 

 for a temperature of 60 F., and the better forms 

 have an attached thermometer ; so that if the milk 

 to be tested varies from this in either direction a cor- 

 rection must be made. As the density increases with 

 a reduction of temperature and decreases with a rise 

 of temperature, the correction must be subtracted in 

 going from a lower to a higher and added in going from 

 a higher to a lower temperature. The amount of such 

 correction for the Quevenne lactometer is .1 of a lac- 

 tometer degree for each degree of temperature, and for 

 the ordinary lactometer one lactometer degree for each 3 



