Aqueous solution of monovalent gold and ammonium sulfite complex, process for the preparation thereof and electrolytic bath obtained therefrom for the plating of gold or gold alloys
AssigneeSystemes de Traitements de Surfaces S.A.
InventorsPierre Laude, Erwin Marka, Franco Zuntini
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Abstract
Aqueous solution of monovalent gold and ammonium sulfite complex. As opposed to the corresponding alkali-gold sulfite solution, this solution is stable under slightly acidic pH conditions and can be used advantageously for preparing electrolytic baths for the plating of gold and gold alloys having a great flexibility of use and a particularly long working life. This solution is prepared, in a very economical manner, by adding ammonia to an HAuCl.sub.4 solution which results in the formation of a precipitate, then by dissolving this precipitate in an aqueous ammonium sulfite solution.
Claims12
An aqueous solution of a monovalent gold and ammonium sulfite complex, which is stable under slightly acidic conditions.
A process for the preparation of an aqueous solution of a monovalent gold and ammonium sulfite complex which is stable under slightly acidic conditions which comprises:
- treating a concentrated hydroaurichloric acid (HAuCl.sub.4) solution with ammonia to thereby form a precipitate of a gold compound;
- then decanting the supernatant solution;
- washing by decantation said precipitate with water until nearly complete elimination of the chlorides;
- then adding to the precipitate a quantity of aqueous solution of ammonium sulfite sufficient to dissolve it and ensure the reduction of the trivalent gold to monovalent gold.
Dependencies are inferred from the claim text.