VOLTAIC CELLS IN FUSED SALTS: PART III. THE SYSTEM SILVER – SILVER CHLORIDE, CADMIUM – CADMIUM CHLORIDE

Abstract

Using a silver–silver chloride reference electrode, the standard electrode potential his been established for the equilibrium Cd|Cd++ in melts containing equimolar quantities of KCl and NaCl. The experimentally obtained standard potential was greater than that calculated from theoretical thermodynamic data. This difference was attributed to the formation of a cadmium complex in the melt. A dissociation constant for the complex was calculated.The effect of temperature on the electromotive force of the silver–cadmium voltaic cell was also measured, and the heat of the cell reaction was calculated from the data. To extend the temperature range of the cadmium data, a cadmium–lead alloy was used in the higher temperature experiments. To correlate these data with those for the pure cadmium system, the activity coefficients of cadmium in the alloy were determined electrometrically using the silver–silver chloride electrode as a reference. It was found that the activity coefficients were in agreement with previously published data obtained at lower temperatures using a pure cadmium reference electrode. The activity coefficients were virtually independent of temperature but showed large positive deviations from unity when the mole fraction of cadmium was decreased below about 0.8.