702 



Transactions. — Chemistry. 



m 

 m 



5a 



and 2a were separated by a space of about xV^^-' ^^'^^ No. 2a 



showed no change in an hour. 



These results prove that for rapid sohition a portion of the 



strip must project above the surface of the hquid ; they also 



suggest the probability of the solution being due to electrical 



currents maintained by the action, at the surface of the 



liquid, of cyanide and the oxygen of the air. 



In pursuance of this idea the following experiments were 



made : The strips shown in Fig. 2 (varnished as shown by 



the shaded portions) 

 were exposed to the solu- 

 tion used in the last ex- 

 periments. In half an 

 hour that portion of No. 

 6 below the surface was 

 completely dissolved. In 

 No. 5 the action was the 

 same — all the strip be- 

 neath the surface of the 

 varnished portion, being 

 with 7, both a and h 



m 



Surtite or LiQuid 



Fig. 2 



liquid, with the 

 dissolved. The 



exception of the 

 same was the case 

 dissolvii^ig, and apparently at about the same rate. No. 4 

 showed no alteration. It was suggested above that the 

 solution of the lower portions of the strips was due to 

 electrical action, and tjiis is clearly proved to be the case 

 by the results obtained with Nos. 5 and 7 strips. Let us 

 consider how No. 5 differs from Nos. 2 and 2a in the last 

 experiments. So far as chemical action is concerned, one 

 would naturally conclude that 2a should be dissolved rather 

 than 5a, since the varnished portion separating 5 and 5a is 

 very much wider than the space between 2 and 2a, and for 

 such action a portion protected by varnish is quite as great a 

 barrier as a blank space. When we consider electrical action, 

 however, the case is quite different : the space between 2 and 

 2a does not allow an electric current to pass, whilst the 

 varnished portion between 5 and 5a off'ei's no obstruction to 

 such a current. It is therefore most probable that a current 

 flows, and that the solution of 5a is due to its action. Again, 

 in No. 7 the solution of h can be expltiined only by the genera- 

 tion of electric currents m a. Hence it follows that the solu- 

 tion of the lower portion of any strip partly immersed in 

 concenirated cyanide of potassium is due to electrical action. 



Should any doubt as to the production of an electric current 

 remain, the results obtained in the following experiment must 

 remove it : — 



Fig. 3 shows two plates of gold, varnished as shown by 

 the shading. The upper ends of these plates were connected 

 through a Thomson's galvanometer (G in the figure). A rested 



