| 摘要 |
1304426 Ammonium gold cyanide ENGELHARD MINERALS & CHEMICALS CORP 2 July 1970 [3 July 1969] 32278/70 Heading C1A Ammonium gold cyanide is prepared by passing an aqueous solution of an alkali metal gold cyanide over a cation exchange resin in ammonium form. The cation exchange resin in ammonium form may be obtained by passing an aqueous solution of an ammonium salt, for example ammonium sulphamate, phosphate or sulphate, over the hydrogen form of the resin. The cation exchange resin may be a sulphonated resin, e.g. a copolymer of styrene and divinylbenzene. The alkali metal cyanide may be potassium gold cyanide or sodium gold cyanide. Alkali metal ions may be desorbed from the resin by acid, e.g. sulphuric acid, to give the hydrogen form of the resin again. In an example, crystalline NH 4 Au(CN) 2 is made by evaporating a 9% aqueous solution of the cyanide eluted from a resin column, the feed solution being 15% K Au(CN) 2 . |
