Boundary conditions of formation Cu2Se and In2Se3 and also their hydroxides defines by means of calculation of ionic equilibrium with using of thermodynamic constants for systems nitrate gallium − copper(I) chloride − selenourea and nitrate gallium − copper(I) chloride − sodium selenosulphate account-ting the formation of crystal nucleus with critical radii. Experimental date on distributions and atomic rations of elements in a chemical bath deposited thin films Cu2Se-Ga2Se3 was discussed by means of the X-ray photoelectronic spectroscopy method.