Process for removal of base metal impurities from molten silver with sulfur hexafluoride

摘要

A method of pyrometallurgical refining of crude silver to remove base metal impurities, particularly bismuth, by treatment with sulfer hexafluoride gas. The crude silver is melted and maintained at about 1000. degree. C. while it is treated concurrently with sulfur hexafluoride and an oxidizing gas, such as air. Base metal fluorides are formed and are removed from the silver, after which the molten bath is treated with a reducing agent, such as hydrogen gas.