Maclauein. — Action of Potassium- Cyanide upon Gold. 707 



If we consider the totals in the above table it will be 

 seen that in the case of the plates suspended by cotton 

 saturation of the solution with air increases the amount 

 of gold dissolved by 3-35, whilst in the case of the plates 

 suspended by gold the increase is only 295. In the for- 

 mer case, solution takes place in the manner already ex- 

 plained in my earlier papers on this subject ; in the latter, in 

 addition to this mode of solution there is solution due to 

 electrical action. Now, if these actions be independent of 

 each other, the results found for the plates suspended by gold 

 must represent the sum of these actions (chemical and elec- 

 trical). Suppose this to be the case : then, in the above table, 

 the amounts (totals) dissolved by electrical action will be 2-65 

 and 2-25 — i.e., 5-65 — 3 and 8-6 -6-35. It appears from this 

 that an increased amount of oxygen in solution decreases 

 the electrical action, whilst it very materially increases the 

 chemical action. Of course, the determinations made are not 

 numerous enough to insure absolutely correct results, but 

 they are quite sufficient to show that the electrical action is 

 independent of the oxygen in solution. Therefore, Mr. Skey's 

 conclusion, that because gold partially immersed in saturated 

 -cyanide solutions rapidly dissolved there must be a con- 

 siderable amount of dissolved oxygen, is incorrect. 



After stating this conclusion, Mr. Skey proceeds — " But 

 why strong cyanide solutions have so little or so very slow 

 an effect upon gold as we find is a question that in the light 

 of these results appears as yet quite unanswered. For my 

 part, I am inclined to think that a compound forms upon the 

 gold when in strong cyanide solutions that is either insoluble 

 or very slowly soluble in these strong solutions, but is 

 soluble to a considerable extent in weak solutions. It is, I 

 think, very probable that the cyanide of gold that first forms 

 on the gold has to be dissolved as a simple cyanide before it 

 can be so acted upon by the potassic cyanide as to pass into 

 the comparatively-soluble aurocyanide of potassium." 



