2l6 UNIVERSITY OF COLORADO STUDIES 



of oil. The two solutions were connected by means of a liquid bridge, 

 and the two gold strips by means of a wire and galvanometer. Gold 

 dissolved in the oxygen-free solution and a current was shown by the 

 galvanometer to be flowing in the solutions from the oxygen-free solu- 

 tion to that containing the dissolved oxygen. 



The following explanation of the phenomenon has occurred to us. 

 Christy's cell is analogous to the simple cell constructed in the same 

 manner by substituting zinc in sodium sulphate for gold in oxygen-free 

 cyanide and copper in sulphuric acid for gold in oxygenated cyanide. 

 Here the current flows in the solutions from the zinc to the copper, zinc 

 dissolving in one solution and hydrogen being liberated on the copper 

 in the other solution. The zinc dissolves in the absence of acid just as 

 in Christy's cell the gold dissolves in the absence of oxygen. In the zinc- 

 copper cell, the solution pressure of the zinc drives zinc ions into the solu- 

 tion, the hydrogen ions in the other solution being thus forced out, 

 giving their charges to the copper with the production of a current out- 

 side the cell from copper to zinc. In Christy's cell, the gold, on account 

 of its solution pressure, sends gold ions into the solution. Hydrogen 

 ions in the oxygenated cyanide vessel (due to the slight ionization of 

 water into H ions and OH ions) tend to be forced out just as in the zinc- 

 copper cell, but this does not occur. The dissolved oxygen sends by 



rt 



virtue of its solution pressure, oxygen ions, O, into the solution. These 

 O ions with the H ions form OH ions, so that the cell acts like a bichro- 

 mate cell, or any other oxidation cell, instead of like a simple zinc-copper 

 couple. The OH ions thus left in the solution form with the K ions 

 dissociated KOH. 



In view of the above considerations, it seemed interesting to us to 

 set up a Au/KCN/O-Pt couple. As expected, gold dissolved rapidly in 

 the cyanide, the rate varying with the concentration of the cyanide, and 

 the concentration of the oxygen in the oxygen electrode, the current 

 passing in the couple from the gold to the oxygen. Solubility deter- 

 minations were made, first, with the external circuit closed, and secondly, 

 with the external circuit broken. Exact solubility determinations are 

 needless and impossible on account of the difficulty of excluding air from 

 the cyanide, and of the variability in the potential of the oxygen electrode. 



