The solubility and the solubility product K-sp of copper(2) oxychloride in aqueous solution were determined as a function of temperature. The pH of saturated solutions was determined at a known concentration of copper(2) chloride. The solubility product varied from 7.8 x 10(-36) at 25 degrees C to 1.4 x 10(-33) at 75 degrees C. No significant effect of particle size on the solubility equilibrium was observed when the diameters of particles were greater than 0.1 mu m. The standard thermodynamic functions Delta G degrees, Delta H degrees, and Delta S degrees for the dissolution process at 25 degrees C were estimated. The results were compared with the literature values.