588 



MR. F. E. SMITH, MR. T. MATHER, AND DR. T. M. LOWRY 



and this affords the only general method of preparing silver peroxide. It was 

 possible that whilst this compound does not crystallise out when a silver anode is 

 used, and does not occur in the anode slime, it might be produced in small quantities 

 and pass into solution, especially if high current densities are used at the anode. It 

 was found, however, that no increase in the electrochemical equivalent resulted when 

 the area of the silver anode of the Rayleigh voltameter was made very small and when 

 high current densities were employed (pp. 571 and 573, Part I.). 



In further experiments it was shown that this action at the anode, which is 

 accompanied by a liberation of acid, actually lowers the value of the electrochemical 

 equivalent instead of raising it. An apparatus was arranged with a platinum crucible 

 as an anode, and between it and the cathode a large filter paper cup was suspended 

 to prevent any crystals of Ag 7 NOn falling on the platinum bowl. The solution was 

 very acid after electrolysis, and the resulting values of the electro-chemical equivalent 

 were 1'11779 (34a) and 1'llSll (55&). The abnormally high equivalents are therefore 

 not due to the formation of peroxynitrate at the anode. 



RICHABDS* found that the anode liquid was so changed during electrolysis that it 

 deposited silver on prolonged contact with silver crystals. We have been unable to 

 confirm this in our voltameters. 



The following experiment was performed so that the anode liquid should come 

 into contact with the silver surface a few seconds after its formation. The anode 

 and kathode liquids were contained in two silver bowls (fig. 14) connected by a 



Fig. 14. 



syphon, and the anode was a silver plate which dipped into a glass funnel fitted with 

 a filter paper. On electrolysis, the dense liquid descended to the bottom of the bowl 

 and thus came into contact with silver. The anode bowl was weighed both before 

 and after electrolysis, but no gain in weight was recorded in any of the experiments, 

 even though on one occasion 20 grammes of silver were deposited on the kathode 

 bowl. In the first experiment the silver plate was surrounded with filter paper only, 

 but this led to complications, owing to part of the current entering and leaving the 



* RICHARDS and HEIMROD, 'Proc. Am. Ac.,' 37, p. 431, 1902. 



