The phase diagrams of the systems and and the densities of the liquid solutions have been measured over the permissible concentration and temperature ranges. Specific conductivities of the liquid mixtures have also been determined. The results indicate that the solutions, for concentrations up to about 30 m/o (mole per cent) and temperatures below 1000 °C, are essentially ionic conductors. Electronic conductance becomes evident for the more concentrated solutions. In the solutions, ionic conductivity appears to be restricted to concentrations below .The thermodynamic calculations from the phase diagram and the structural interpretation of the density measurements indicate that dimers are present in dilute solutions. Further association occurs at higher concentrations and the formation of a continuous sulfide network appears to be related to the onset of electronic conduction. The solubility of copper metal in cuprous chloride is very low, and the conductivity of cuprous chloride, and of cuprous chloride‐rich melts with cuprous sulfide, appears unaffected by the presence of copper metal. The addition of excess copper metal to molten cuprous sulfide, however, greatly increases its electrical conductivity.Because the electrical conductivities of cuprous and ferrous sulfides are predominantly electronic in nature electrodeposition from the molten sulfides is not feasible. Electrolysis of solutions of in in the composition and temperature ranges of ionic behavior yielded copper metal at the cathode with high current efficiencies. Copper metal was also recovered selectively from solutions of a synthetic matte dissolved in molten . It is also shown that may be extracted from a synthetic matte by solvent extraction using molten at the appropriate temperatures. The extraction is attributed to an exchange reaction which converts the component into the soluble ionic form of .