AQUEOUS SOLUBILITIES, SOLUBILITY PRODUCTS AND STANDARD OXIDATION-REDUCTION POTENTIALS OF THE METAL SULFIDES

Available thermodynamic data, incorporating a new free energy of formation for aqueous S2- of 111 (±2) kJ/mol at 25°C, indicate that solubility products of the insoluble metal sulfide salts are several orders of magnitude smaller than previously considered. Thermodynamic characterization for a variety of soluble and insoluble aqueous metal sulfide systems is reported. Trends in the aqueous solubilities of the alkali salts solubilities are compared and discussed. New aqueous solubility products, Ksp, and standard redox potentials, Eo, for over forty metal sulfides are determined. The new values of pKsp and Eo at 25°C include: Ag2S-orthorhombic: 53.6, -0.786V, and HgS-red: 56.4, -0.816V.