Y. Henderson Ba 
The correctness of the graduation of the tube of the burette is most 
easily checked by drawing in on top of the mercury about 0.5 cc. of water. 
By raising and lowering the mercury and reading the air-water and water- 
‘ 
Frag: 3. 
mercury menisci at various levels (allowing time for the water to drain 
from the sides), errors of graduation due to irregularities in the caliber 
of the tube are revealed. The difference in the volume between the two 
menisci should not vary more than 0.005 cc. at any two levels. 
