Method for refining precious metals
US4397686A · kind A · utility
Inventors
Key dates
| Filing date | Jan 12, 1981 |
| Grant date | Aug 9, 1983 |
| Priority date | — |
| Expiry date | Jan 12, 2001 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC22B9/10
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A method for economically removing base metal impurities, other oxidizable impurities, and volatile impurities from precious-metal-bearing metallic materials, consisting of silver and gold, to obtain, with high recovery, a resultant precious metal of high purity (more than 99.9%) that greatly reduces refining time and precious metal loss in recovery. The method includes the steps of (1) controlled heating to maintain a temperature slightly above the melting temperature of the molten metallic mass, (2) maintaining contact between an oxidizing agent and the metallic mass to provide a concentration of dissolved oxygen within the molten metal throughout the refining process, (3) maintaining a flux medium on the surface of the molten material that absorbs base metal and other impurity oxides, and (4) controlling the concentration of base metal and other impurity oxides in the flux to a level that ensures continued transfer of the base metal oxides into the flux medium. The oxidizing agent, which is continuously absorbed into solution in the molten precious metal, combines with base metal impurities such as copper, zinc, iron or lead, and other oxidizable impurities to form oxides which …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.