108 



EXPERIMENTAL PHYSIOLOGY. 



When the mercury has risen to the piece of rubber tubing at 

 the end of tube H, b is closed and a slowly screwed down until 

 the mercury just fills the rubber tubing on H the last trace of 

 acid water being removed by means of a piece of filter paper. 

 The next step is to lower the reservoir B to hook 2, release the 

 screw clip a and cautiously open clamp b so that the mercury 



FIG. 32. 



slowly falls in the burette to a little below the 10 c.c. mark. 

 The tap C is then turned in the position III so that both 

 A and D communicate with the outside. The exact position 

 of the level of the NaOH solution in the tube between D and E 

 is marked on the glass (by a glass pencil or pen) and the mercury 

 level in the burette is adjusted, by using the screw clip a, so 



