MILK TESTING. 27 
sions; every five divisions marks one per cent and each division 
is therefore two-tenths of one per cent. 
54. The Pipette. 
The pipette is a glass tube with a bulb in the middle for 
measuring the milk. There is a mark on the upper narrow stem 
indicating 17.6 ¢. c.; this volume of average milk weighs eighteen 
erams. 
55. The Acid Measure. 
This is a glass cylinder with a 17.5 ¢. c. mark on it for meas- 
uring the sulphuric acid used in making the test. 
56. The Centrifuge. 
This is a machine for whirling the bottles. It consists of a 
drum 15 to 24 inches in diameter, with swinging sockets in 
the center for holding the bottles. The centrifuge is driven 
either by a crank or pulley and gear, by a steam turbiné or by 
electricity. 
57- To Make the Test. 
The milk to be tested must be thoroughly mixed to get the 
fat globules evenly distributed. This can be done by pouring 
from one vessel to another several times. If the cream is some- 
what hardened on a sample of milk it can be dissolved by warm- 
ing the milk a little, but this must be done with care as the milk 
will then churn easily. After the milk is thoroughly mixed, 
draw it up into the pipette by suction and then quickly place 
the finger over the upper end of it. By letting air in slowly 
under the finger the milk will run out till it drops to the 17.6 «. ¢. 
mark. Then deliver the contents into the bottle. Next measure 
17.5 ec. e. sulphuric acid into the bottle, and by a circular motion 
mix the acid and the milk thoroughly till the milk is all dis- 
solved, that is, till no clots of curd are left. 
Then put the bottle in the centrifuge and whirl four min- 
utes. At the end of this time all the fat will be on the top of the 
liquid. Hot water is filled in to bring the fat up into the neck 
where the amount can be read on the seale. It is whirled another 
minute to bring all the fat into the neck in a solid layer. The 
fat column must be read before it gets cold, while still in a per- 
