MILK PRODUCTS 427 
bottles and the finger removed to let the milk ow into the bottle. 
ret ne pipe drain and then blow in the upper end to expel all 
the milk. 
(c) Adding acid—The test bottle containing the milk is now 
ready for the acid. The exact amount is 17.5 cubic centimeters. 
The acid may be poured into the 
test bottle by means of an acid meas- 
ure, the exact quantity having been 
measured. The test bottle is held in 
a slightly slanting position and the 
acid poured into it. The acid being 
heavier than the milk, sinks to the 
bottom at once. By gently shaking 
with a rotary motion, the acid and 
milk are now mixed. Continue this 
motion until the material in the test 
FON i 
Mixinc MILK AND AcID bottle is dark brown and quite warm. 
Bottle should be given a rotary (d) Whirling the bottles. — The 
motion. bottles, mixed with milk and acid, 
are now placed in the tester. An 
even number of bottles should be whirled at the same time and 
placed opposite each other in the tester. When all the samples have 
been placed, the cover of the tester is put on the machine and the 
machine turned at the rate described in the directions accompanying 
the machine. Ordinarily, the bottles should make from 750 to 1,200 
revolutions a minute. The machine should be whirled at this rate 
for about seven minutes. 
(e) Adding hot water—After whirling the bottles as directed, hot 
water is poured into each test bottle so as to 
bring the mixture up to the bottom of the 
neck. The bottles are then put back into the 
machine and the whirling continued for two 
or three minutes, and then water again is 
added to the test bottle to bring all of the 
fat up into the neck of the bottle where it 
may be measured. As each bottle is taken 
from the tester, it is held in a straight posi- 
tion in front on a level with the eye. The 
division marks on the neck of the bottle in- 
dicate the measures for each per cent of fat. 
Counting the spaces occupied by the yellow 
substance in the neck of the bottle will give 
the total per cent of fat in that sample of 
milk. If, for instance, the yellowish sub- 
stance occupies a space between 1 and 5, that 
would indicate the percentage of fat in that 
sample to be 4. If a sample reads from 1% to 534, then the per 
cent of butter fat would be 4%. 
3. More Butter THAN Fat.—Since the Babcock tester gives the 
WHIRLING THE BOTTLES 
