Abstract: Process for removing impurities selected from the group consisting of manese, cobalt, nickel and thallium from an acidic zinc or cadmium solution comprising adding thereto acid of Caro or an ammonium or alkali metal salt thereof.

Abstract: A process for removing chlorine from a solution of zinc sulfate, in which the pH of the solution is reduced to below 2.6 with sulfuric acid. Cupric ions are established in the solution in an amount such that after removal of the chlorine by precipitation as cuprous chloride, there remains an excess of cupric copper in the solution which is greater than 0.5 g/l. The cupric ions can be added by adding cupric sulphate and zinc powder, or cupric salt and metallic copper, or cupric copper followed by cuprous oxide. The cuprous chloride precipitate is collected and washed and treated with sodium hydroxide in an amount to raise the pH to more than 7, thereby to precipitate cuprous oxide which is separated by filtration.

Abstract: In a process for the treatment of a material containing zinc and soluble silica by dilute aqueous solutions of sulphuric acid at a temperature below its boiling point under atmospheric pressure, the acid is progressively added to the zinc containing material over a period of at least 3 hours, in such a quantity that the final acidity of the solution will be 1.5 to 15 g/l, while carefully maintaining the temperature at 70.degree. to 90.degree.C, thereby inducing the lixiviation of the material and simultaneously the reprecipitation of silica in a crystalline form which can readily be eliminated by filtration.