Relation of Quevenne to Ordinary Lactometer. 87 
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 ean be at 
once read, a degree upon this scale being equivalent 
to one degree of specific gravity. Since 100 degrees 
upon the ordinary lactometer are equal to 29 degrees 
specific gravity, the specific gravity may be obtained 
by multiplying the ordinary lactometer reading by 
.29 and adding 1,000. Twenty-nine Quevenne de- 
grees are also equivalent to 100 ordinary degrees, 
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 if 
the temperature is too low, and added if the temper- 
ature is too high. The amount of such correction 
for the Quevenne lactometer is .1 of a lactometer 
degree for each degree of temperature, and for the 
ordinary lactometer one lactometer degree for each 3 
Digitized by Microsoft® 
