Skey. — Action of Potassium- Cyanide upon Gold. 711 



merged end of our gold strip. To be explicit : so far from 

 the submerged gold requiring an electromotive power to pass 

 it into solution, it produces electromotive power as it dis- 

 solves, and of sufficient intensity, as I show, to electro-deposit 

 copper from its sulphate or gold from its cyanide. To go to 

 particulars : taking Mr. Maclaurin's own conception as to 

 the chemical operation that goes on in the process, viz., that 

 the cyanogen of the cyanide attacks the submerged gold 

 direct, while the potassium combines with oxygen at the 

 other end of the metal (a happy conception fitting the case, 

 and apparently true), I should maintain that the cyano- 

 dizing of the gold and the oxidizing of the potassium are 

 the initiatory steps in the process, and the current observed is 

 the effect of this and not the cause as assumed. The func- 

 tion of the interpolar connection (gold, piatina, or conducting 

 sulphide, as the case may be) is to conduct the electricity 

 generated, and so to allow a long slip of the liquid itself to be 

 polarized ; the effect of which is that cyanodizing and oxi- 

 dizing can and do go on simultaneously in the localities 

 especially suited for each process. 



Now, I have stated in the notes of mine referred to that 

 the rapid chemical action that occurs at the gold near to or 

 above the surface-line of the cyanide solution had a " mis- 

 leading effect upon me"; and I think that Mr. Maclaurin will 

 soon have to confess to a similar experience on his part. The 

 gold is so rapidly dissolved at that place that the electric 

 current observed is at first naturally assumed to have been 

 generated there ; but, though there must be electricity gene- 

 rated there, it does not become electromotive power, being 

 merely that of local action of the kind we have when we use 

 common zinc for a pole, and it takes no part in the dissolution 

 of the submerged gold. Any way, the dissolution of this sub- 

 merged end can be rapidly effected without it — that is (to 

 keep exactly to the text), without the assistance of any elec- 

 tromotive action taking place at the surface, or, indeed, any- 

 where else. This is proved by the results of the following 

 experiment taken from my old working-notes : — 



In the following figure (Pig. 1), representing the apparatus 



that I used, the vessel A contains a 

 saturated aqueous solution of potassic 

 cyanide. B contains a weak solution 

 of common salt. C contains an aqueous 

 solution of potash. D, D are glass tubes 

 filled with sodic chloride solution to 

 Fjn. I make interpolar connections. E, P are 



strips of gold leaf glued to paper (for 

 support), and connecting with each other through the galvano- 

 meter G. The cyanide solution is covered with a layer of oil. 



