14 



teen and one-half cubic centimeters of the acid are meas- 

 ured out, and, with the bottle held at an angle, carefully 

 poured down the side, the bottle being turned slowly at 

 the same time so that any milk adhering to the neck will 

 be washed down. For two reasons the acid must not be 

 poured into the middle of the test bottle; first, because it 



FIG. 12. Hy- 

 drometer and 

 cylinder used 

 in testing sul- 

 phuric acid. 



FIG. 13. The right way of add- 

 ing milk to the test bottle. 

 (Farrington and Woll, Testing 

 Milk and Its Products.) 



may form a plug in the neck, which may be driven out by 

 the expansion of the air below; and second, because the 

 acid may partially mix with the milk and produce black 

 particles which do not dissolve and later interfere with 

 the reading of the test. The acid and milk should now 

 be in two distinct layers without much of a dark layer 

 between them. 



