Abstract: In conjunction with an electrolytic production of zinc, the residues are processed so that the residue is leached with cell acid at a temperature from 50.degree. to 100.degree. C. in such a manner that a concentration of free acid from 10 to 100 g/l is obtained at the end of the leaching. The undissolved matter is separated from the suspension, the separated matter is supplied to the acid leaching step performed in the electrolytic production of zinc, and fine-grained metallic iron is added to the solution from which the undissolved matter has been removed so that copper is precipitated. The precipitated copper is separated and the liquid phase from which the precipitated copper has been separated is supplied to one of the stages which precede the precipitation of iron in the electrolytic production of zinc.

Abstract: A process for treating a residue from the sulfuric acid leaching of roasted zinc blende, comprising(a) leaching the residue in a single stage with sulfuric acid and a metal sulfide supplied in a quantity sufficient for transforming the iron into divalent iron, the temperature being maintained between about 60.degree. C and the boiling point,(b) heating the mass to a temperature above the melting point of sulfur, separating a first fine-grained residue of low zinc and iron contents and high lead content, and separating a coarse-grained residue containing sulfur, compounds of iron and any excess metal sulfide from (a),(c) adjusting the pH of the residual solution to at most about 2, at a temperature between about 80.degree.