Calculation of ionic equilibrium using the thermodynamic constants for systems indium chloride − copper chloride − thiourea and indium chloride − copper chloride − thiourea - trilon B defines boundary conditions of Cu2S and In2S3 and their hydroxides formation with the account of the crystallization factor. It has been experimentally shown that there is the possibility of getting films of solid InxCu1−xS2 solutions of various compositions thin InxCu1−xS2 solid substitution solutions by hydrochemical deposition.