﻿MERCUKOrS PERCHLORATK VOLTA^IETER 



47 



in small quantities did a\\'aY with the black powder and gave a per- 

 fect deposit of mercury. 



The form of the cell that was em^ployed is shown in Fignre I. 

 The stem of a large thistle tube (a) was sealed to a capillary tube of 

 about 0.6 mm. ])ore. To this was sealed a tube of larger diameter 

 (3 to 4 mm.) containing a stop cock (e), and bearing a side arm 



