238 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
1.825 at 15° C. and amyl alcohol. The test is made as 
follows: The milk and the chemicals should be at a tem- 
perature of 15° C.; 10 c.c. of sulphuric acid are measured 
with the acid pipette and placed in the bottle. The point 
of the pipette should be passed obliquely through the 
opening of the bottle until it comes in contact with the 
side of the bottle, when the acid is allowed to flow slowly 
out. Care should be taken that no acid is deposited in 
the spiral grooves on the inner side of the opening. After 
thoroughly mixing the milk, 11 c.c. are drawn up into 
the proper pipette and placed in the bottle with the 
same precautions, the milk being permitted to flow 
slowly down the side of the bottle so that it will not mix 
with the acid. Then 1 ¢.c. of amyl alcohol is placed in 
the bottle in the same manner with the alcohol pipette. 
The three fluids should be arranged in three distinct 
layers. The bottle is closed with the rubber stopper and 
the fluids are mixed by slowly raising first one end of the 
bottle and then the other, permitting the fluid to flow in 
and out of the neck. This is continued until a perfect 
solution is obtained. The rubber stopper should be 
forced in sufficiently to raise the fluid to the zero mark 
on the scale in the neck and it should be held in place 
with the thumb while the bottle is being shaken. This 
latter precaution is taken to prevent the stopper from 
coming out, although this is not likely to occur if it is 
properly inserted. The bottle should be placed in a 
water bath at a temperature of 60° to 65° C. (140° to 
150° F.), with the stopper downward and the water 
covering the entire bottle, until it is centrifugalized. This 
will not be necessary, however, when only one or two 
samples are being tested. If a hand centrifuge is used 
the whirling must be continued 10 minutes, but with a 
