THE ELECTROCHEMISTRY OF THE SOLUTION 

 OF GOLD IN POTASSIUM CYANIDE 



By John B. Ekeley and Arthur L. Tatum 



In 1893, McLaurin 1 proved definitely that gold will dissolve in potas- 

 sium cyanide solution when there is oxygen present, but that, if no 

 oxygen is contained in the cyanide solution, the gold remains unacted 

 upon. From pure hydrocyanic acid and potassium hydroxide dis- 

 solved in water freed from air by long boiling, McLaurin prepared a 

 solution of potassium cyanide. A Dumas bulb was partly filled with 

 this solution, a strip of pure gold was placed in the neck of the bulb, 

 and, while the solution was boiling, the neck was sealed. The gold was 

 allowed to remain in the solution for 24 hours, the gold losing .0002 

 grm. The gold was then allowed to remain in contact with the same 

 solution in the presence of air for 24 hours, during which time it lost 

 .0083 grm. This is the best experimental evidence that we have that 

 gold requires oxygen for its solution in potassium cyanide. 



Although other investigators took up the study of the solubility of 

 gold in potassium cyanide, little of any great value in a theoretical way 

 was brought forward until Christy 2 took the subject up from an electro- 

 chemical standpoint, his work being published in 1902. 



Christy made use of the Au/KCN/Hg 2 Cl 2 /Hg couple, measuring 

 the electromotive force and finding that the positive current flows in the 

 cell from the gold electrode to the mercury, gold going into solution and 

 mercury being deposited. He then suggests that, should an oxygen 

 electrode be substituted for the calomel electrode, the gold would go 

 into solution in the cyanide and the platinum would receive the same 

 electrical charge that he found in the case of the mercury. In support 

 of this he performed the following experiment. A strip of gold was 

 suspended in a solution of potassium cyanide that had been saturated 

 with oxygen. A second strip of gold was suspended in a similar solu- 

 tion freed from oxygen by boiling and subsequently protected by a layer 



1 Journal of the Chemical Society of London, Vol. LXIII, p. 727. 

 1 Electrochemische Zeitschri/l, Vol. XVIII, p. 227. 



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