CuHemica, TEsts:-AND ANALYSES 343 
one and one-half inches wide. Fill the evlinder with milk at a 
temperature between 55 and 65 degrees F. Insert the lactometer 
and when it has found its equilibrium, note the point on the scale 
at the surface of the milk. The correct temperature is 60 degrees 
I’, For every degree Fahrenheit above 60 add one-tenth point 
to the observed reading, and for every degree Fahrenheit below 
60 deduct one-tenth point from the observed reading. This rule 
holds good only when the range of temperature is within the 
limits of 55 degrees and 65 degrees F. 
The specific gravity is calculated by adding 1,000 to the 
lactometer reading and dividing the sum by 1,000. Example: 
Lactometer reading is 31 at 65 degrees F. Corrected reading is 
S15 
31.5 + 1000 
1000 
Gravimetric Determination.—This consists of the filling of 
specific gravity 1s- == 0313, 
a perfectly dry picnometer or other graduated flask of known meas- 
ure with milk at the standard temperature (60 degrees F., or 15.5 
degrees C.) and weighing the flask and contents. The weight of 
the flask is then deducted from the weight of the flask plus con- 
tents and the difference is divided by the weight of an equal volume 
of water at standard temperature. The result is the specific gravity 
of the milk. 
The Westphal balance method furnishes another accurate means 
of determining the specific gravity. Both the gravimetric method 
and the Westphal balance method, while accurate when operated 
by the skillful chemist, require considerable time. Experimental 
comparisons have demonstrated that for all practical purposes the 
Quevenne hydrometer, when accurately graduated, yields correct 
results, and the simplicity and rapidity of its operation render its 
use in the determination of the specific gravity of milk highly ad- 
vantageous and satisfactory. 
Total Solids. 
By Means of the Babcock Formula.—For rapid and reason- 
ably accurate work the total solids of milk may be determined by 
the use of the Babcock formula, which is as follows: 
Total solids = Bi pee Gs 
