Solutions of Silver and Copper in Their Molten Salt Systems AgClxBr1‐x and CuClxBr1‐x

Abstract

AbstractThe solubilities of the metals copper and silver in their molten salt systems AgClxBr1‐x and CuClxBr1‐x, respectively, were measured as functions of x and T. From the experimental data and using sublimation data for the metals from the literature, the enthalpies and entropies for the reaction Me(gas) → Me(dissolved)were calculated. In both systems, these solvation enthalpies and entropies do not vary monotonically with the composition parameter x of the melt, but show marked extrema at some compositions, indicating discrete structures within the solvation shell of the dissolved species.Spectroscopic investigations were made on the system Ag/AgCl. The difference spectrum between the pure melt and the metal solution shows a band at 540 nm (540°C), the intensity of which is proportional to the metal concentration. With increasing temperature, the wavelength of maximum absorption is shifted towards higher values.The influence of the dissolved metal on the electric conductivity of the melts was studied in the silver solutions as a function of T and x. In all cases, this influence was within the experimental error and definitely smaller than should be predicted on the base of a free electron model. Using the concept of electrons trapped in a cavity (spherical box with inifinite potential walls) for interpreting the spectroscopic data. one finds a cavity diameter of 7.1 A at 550°C and a thermal expansivity of the cavity of 8.1 · 10−1 K−1. In accordance with the results on other solvated electron systems, this value is higher than the macroscopic expansivity of the solvents (αv(AgCl) = 1.74 · 10−4 K−1).