VOLTAIC CELLS IN FUSED SALTS: PART I. THE SILVER – SILVER CHLORIDE, COBALT – COBALTOUS CHLORIDE SYSTEM

Abstract

A reversible silver − silver chloride reference electrode for use in melts at high temperatures has been developed. It was found that the solution of silver chloride in an equimolar mixture of KCl–NaCl melt is ideal for the range of concentrations studied, i.e. 1.0 × 10−3 to 6.0 × 10−2 mole fraction of AgCl.The electromotive force of the voltaic cell[Formula: see text]in which the half-cell to the right contains the above-mentioned reference electrode, was measured as a function of CoCl2 concentration. The applicability of the Nernst equation to this system was established. Deviation from ideality was observed in the case of the solution of CoCl2 in the melt solvent, and this was attributed to the formation of a complex. The dissociation constant of this complex was calculated as 4.50 × 10−2 at 710 °C.The effect of temperature on the electromotive force of this cell was also measured, and the heat of the cell reaction in the presence of solvent (Co + 2AgCl → CoCl2 + 2Ag) was calculated from the data as 22.8 ± 1.3 kcal.The thermodynamic significance of the standard electrode potential of the Co–Ag voltaic cell, derived experimentally as 0.324 volt, is discussed briefly.