Solvation of ions. Some applications. III. Solutions of copper(I) salts in water containing ligands

Solutions of copper(II) and copper(I) sulphate in water containing acetonitrile have applications in the hydrometallurgy of copper. The potentials (n.h.e.) of the Cu+/Cu; the Pt/Cu2+, Cu+, and the Cu2+/Cu electrodes in water containing a large molar excess of various copper(I) bases and various counter-anions have been measured. Free energies of transfer of copper(I) ions from water to water containing the bases are calculated. ΔGtr(Cu+) at 25°C becomes less exoenergetic for water containing the bases in the following order: CN- >> S2O32- > Me2NCHS > KI > NH3 > C5H5N > KBr > KCl > C3H5OH ≥ MeCN, CO, C2H4 > C3H6. The reduction potentials of CuSO4/Cu2SO4 in acidic saturated copper(II) sulphate solutions and a range of Cu2SO4 concentrations in acetonitrile- water mixtures show that CuSO4/MeCN/H2O is a powerful oxidant, comparable in strength to acidic iron(III) sulphate in water. Acetonitrile is the preferred base for the processing of copper by way of solutions of copper(I) sulphate