PURIFICATION OF SILVER NITRATE SOLUTIONS

1,248,264. Purifying silver nitrate solutions. EASTMAN KODAK CO. 6 June, 1969 [6 June, 1968], No. 28640/69. Heading C1A. Silver oxide is added in two stages to aqueous silver nitrate to precipitate other metals present, the first stage being to a pH from 5À1-5À8 and the second to a pH from 5À9-6À3, the precipitates being removed after the respective additions. The precipitate resulting from the second silver oxide addition may be combined with a second batch of impure solution that is to be subjected to purification. The impure solution should preferably contain less than 440 gm. of silver per litre. The method may be applied to solutions formed by dissolving silver bullion in nitric acid or solutions comprising electrolytic cell liquors which have been used in the refining of silver.