METHODS OF EXAMINING MILK 235 
obtain accurate results, every particle of milk must be 
delivered into the bottle. The measuring cylinder is 
filled to the 17.5 e.c. mark with sulphuric acid; then, 
with the bottle held by the neck in an oblique position, 
the acid is poured slowly down the side, the bottle being 
rotated slowly so that any milk in the neck will be washed 
down. The acid and milk are then mixed by grasping 
the bottle by the neck and gently whirling it, first to the 
right and then to the left, or by holding the bottle by 
the neck in an inclined position with the edge of the bot- 
tom resting on a table and rotating it, 
first in one direction and then in the rT 
other. When mixing is once com- 
menced it must be continued until 
solution is complete. The solution 175 
should finally be of a dark brown color, 
The bottle is placed in a centrifuge 
and whirled for five minutes at a speed 
of 800 to 1200 revolutions per minute. | 3. Tiiaer used 
Hot water at a temperature above in Babcock test for_meas- 
120° F. (49° C.) is then added until Guan et Siew 
the bottle is filled to the bottom of the 7 ?:PtcfAsieuture) 
neck and the bottle is replaced in the centrifuge and 
whirled for two minutes. Hot water is again added until 
the fluid in the bottle is raised to a point near the top 
of the graduated scale, the water being dropped directly 
into the fluid, not run down the side, in order to remove 
any flocculent material which may be entangled in the 
fat at the top. The bottle is then whirled another min- 
ute. After the whirling is completed, the fat should be 
collected at the top of the fluid in the bottle in a column 
of clear, yellowish liquid, with a nearly colorless fluid 
below it. The fat column should have a well-defined 
