1892.] On the Electrolysis of Silver Nitrate in Vacuo. 349 



Lord Rayleigh in his experiments on the silver voltameter used 

 two bowls of approximately the same size as ours, and the foregoing 

 comparison will show that the difference in the deposits pointed out 

 by us also appears in his results. 



In Table II we have entered in two separate columns the deposits 

 obtained by Lord Rayleigh simultaneously from silver nitrate solu- 

 tions in large and small bowls respectively. 



The mean deposit in the large bowls is therefore greater by ap- 

 proximately the same amount as in our experiments. In three cases 

 only were the deposits in the small bowls heavier ; and in two out of 

 these three cases the bowl showing these larger deposits contained 

 a 30 per cent, solution, while the other at the same time was filled 

 with a 15 per cent, solution. It seems possible, therefore, that when 

 the strength of the solution is increased to 30 per cent, the difference 

 due to the size of the bowls will disappear. We have recalculated 

 Lord Rayleigh's value for the equivalent of silver, taking the de- 

 posits in the large and small bowls separately, using the weight of 

 silver deposited before heating to verge of redness ; we find for the 

 equivalent of silver : 



(a) calculated from deposits in large bowls .... '0111817 

 (&) small .... 0-0111797 



Mean '0111807 



The heating to redness seems to affect the deposits equally, and 

 reduces the weight, on the average, by about one part in ten 

 thousand, which accounts for the difference between the above mean 

 and the equivalent as given by Lord Rayleigh and Mrs. Sidgwick. 



In some of our later experiments we used three voltameters in 

 series, two of them being kept in an exhausted receiver. 



This arrangement allowed us to judge whether the difference in 

 the results obtained with large and small bowls persisted in vacua. 

 The results are not very concordant, but the average deposits are 

 heavier in the large bowl, and hence we do not believe that the in- 

 fluence of current density can be ascribed to the presence of air in 

 the solution. 



In Experiment 27 the manipulation differed, in so far as the bowls 

 were cleared out with sand before use : a proceeding adopted in the 

 first experiments as far as the eleventh, but abandoned afterwards. 

 We cannot, of course, draw any conclusions from a single experiment, 

 but it does not seem impossible that the complete removal of the 

 old surface by washing with sand renders the effect of current density 

 more prominent. There is, no doubt, a difference in the condition 

 under which the electrolysis is carried out, according as the deposit 

 takes place on platinum as in the first few seconds, or on silver as in 



VOL. L. 2 B 



