Summary. Using a new mathematical treatment, the nature and stability constants of the simple and mixed complex-species of copper(I1) with hydroxyde and ammonia as ligands have been determined. The solubility curves of CuO in heterogeneous equilibrium have been identified in function of pH only and in function of pH and pNH,,,, a t 25 "C and unit ionic strength (NaClO,).The predominent species in the relatively dilute system limited by the ionic strength are [Cu2+]