The Babcock Test Glassware 95 
steam is introduced into the bottle chamber or 
where the cover fits so tightly that no cold air 
enters the chamber during the whirling; the bottles 
are often heated to such a degree that the reading 
is made too large because of the expansion of the 
fat at the high temperature. The fat should be read 
at a temperature of 110° F., 
but up to 140° F. the expan- 
sion is not sufficient to cause 
material error. When, how- 
ever, the temperature rises to 
200° F. or thereabout, as fre- 
quently occurs under the con- 
ditions named above, the error 
due to the expan- 
sion of the fat may 
amount to .15 to 
.38 per cent. In all 
such cases the bot- 
tles should be al- 
lowed to cool to at 
least 140° F. before 
reading. Those cen- 
trifugals are most i 
satisfactory in which provision is made for the bottles 
to assume a perfectly horizontal position when in mo- 
tion and a perfectly perpendicular one when at rest. 
Fig. 13. Steam turbine centrifugal for 
Babcock test. (See opposite page.) 
The glassware.— The glassware consists of a flask 
or test bottle in which the determination is made, 
a graduated pipette for measuring the milk, and a 
short graduated glass cylinder for measuring the 
