THE BABCOCK TEST 57 
It has been learned that the volume of the graduated 
part of the neck is 2 c.c. Each section of the tester is 
made to displace 1 c.c. when immersed in the liquid, 
hence the two sections will just fill the scale if the latter 
is correct. 
The method recommended below for calibrating cream 
bottles may also be used with milk bottles. 
Calibrating Cream Bottles. According to Hunziker,* 
the most satisfactory method of calibrating cream test 
bottles is as follows (see Fig. 18): Fill the bottle to 
the zero mark with water. Remove any drops adhering 
to the inside of the neck with a coiled piece of filter or 
blotting paper. Now slowly add measured amounts of 
water from an accurate burette graduated to at least 0.1 
cc. Every 0.1 cc. of water run into the neck is equiv- 
alent to 0.5% on the scale of an 18 gram cream bottle and 
1.0% on a g gram cream bottle. That is, with an 18 
gram 30% bottle, 6 c.c. of water would be required to 
exactly fill the scale on the neck. 
In calibrating milk and cream bottles, different parts 
of the neck should be tested as well as the neck as a 
whole. 
Calculating Speed of Tester. The speed at which 
a tester must be run is dependent upon the diameter of 
the wheel carrying the bottles. The larger this wheel 
the fewer the revolutions it must make per minute to 
effect a complete separation of the fat. 
In the following table by Farrington and Woll the 
necessary speed per given diameter is calculated: 
*Bulletin No. 145, Indiana Experiment Station. 
