The results of thermodynamic calculations and an analysis of the CuFeS2-H2O-O-2-CO2-C4H9OCSS--CrO (4) (2-) system, which characterizes the surface state of chalcopyrite in conditions of the selective flotation of copper-lead concentrates according to bichromate technology in the alkali medium, are presented. The electrode potentials of chalcopyrite are measured experimentally in solutions of potassium bichromate and potassium butyl xanthate with alkali pH. Due to the investigations, the mechanism of formation of the sorption layer of the collector on chalcopyrite is considered in the depression conditions of galenite by chromate ions. It is shown theoretically that the degree of oxidation of sulfide sulfur should not affect the competitive reactions of the formation of butyl xanthate on the chalcopyrite surface. It is established from the results of measuring the potential of the chalcopyrite electrode that chromate ions are not potential-deter-mining for chalcopyrite in their broad concentration range. The chalcopyrite surface in alkali solutions of butyl xanthate and potassium bichromate should preferentially hydrophobize due to the formation of butyl copper xanthate, and the sorption layer of the collector of a mixed composition in a form of copper(I) butyl xanthate and dixanthogenide can form only in a narrow range of the values of the redox potential and pH.
