Skey. — Action of Potassium- Cyanide upon Gold. 709 



cess, I allowed in that communication of mine that Mr. Mac- 

 laurin had solved the question in its practical bearings as to 

 why gold is so slightly affected by strong cyanide solutions as 

 experience has proved it to be ; and, further, I proved that 

 even in those cases where an electric current is produced 

 during the solution of gold in potassic cyanide, free oxygen is 

 also necessary. 



One of the points upon which Mr. Maclaurin does not 

 agree with me is where I state that a product is generated on 

 the gold in the cyanide solution that hinders the dissolution 

 of this metal to a more or less extent. In answer to this I 

 would refer him to page 45 of the Laboratory Report cited, 

 where, as an additional result supporting this, I prove that by 

 the amalgamation test the cyanodizing or oxidizing of the 

 gold is always much ahead of its dissolution. As to the 

 author's statement that it is inexplicable why I should as- 

 sume that the gold compound that first forms is insoluble in 

 strong potassic cyanide, while the analogous silver compound 

 is more rapidly dissolved therein than in the weak solution, 

 I would answer that I have not tied myself to any particular 

 gold compound — nor yet to any one— the formulas of which 

 is known, and my result certainly appears to show that at 

 least there is a gold compound that forms in potassic cyanide 

 which is very slowly soluble therein. 



As to the inability of Mr. Maclaurin to confirm my state- 

 ment regarding the results of electrically pairing platina with 

 gold, except I allow that the platina must project out of the 

 cyanide solution, I have to say that if the platina is wholly 

 submerged therein, it all depends upon the area of the two 

 metals relatively to each other as to whether the result I 

 describe is easily observed or not. If the area of the platina 

 considerably exceeds that of the gold — as was the case in my 

 experiment — so much free oxygen present in the solution is 

 available for oxidation that the dissolution of the gold is 

 sufficiently accelerated to allow of its being easily observed. 

 If the platina is allowed to project above the cyanide, it does, 

 as Mr. Maclaurin observes, take the place of gold, and the 

 dissolution of that metal is still further accelerated. There is 

 another difference in our mode of conducting the experiment 

 the knowledge of which helps to reconcile our differences on 

 this point : I worked with shallow depths of liquid ; the 

 author had his metals deeply submerged ; and, as I rely some- 

 what on the absorption of aerial oxygen going on simul- 

 taneously with the dissolution of the gold, the result I stated 

 did not come out so well by the use of Mr. Maclaurin's 

 method.''' 



* These remarks have an application to the metallic sulphides. 



