REDUCTION OF MILLER CHLORIDES WITH SODIUM OXIDE-CONTAINING REAGENTS

A mixture of silver chloride and copper chloride is produced when impu re molten gold is refined with gaseous chlorine. Mixed chlorides, cont aining 55.23 mass% silver and 10.61 mass% copper, were smelted with so dium oxide-containing compounds. Sodium oxide, sodium carbonate and so dium hydroxide were tested. The overall reactions were 2AgCl + Na2O = 2Ag + 2NaCl + 1/2 O2 2CuCl + Na2O = Cu2O + 2NaCl The effects of smelti ng temperature and time an of the amount of sodium oxide-containing re agent and carbon additions were investigated. Sodium chloride is produ ced as a by-product. Silver recoveries of more than 95% were achieved with about 1 wt% copper in the metallic product. With carbon addition silver recovery was over 99%. However, this also resulted in essential ly complete reduction of the copper oxide to copper. The resulting met al contained about 84 wt% silver and 15 wt% copper. The impure silver was refined under a borosilicate slag.