Recovery of rhodium values

Abstract

Ammonium pentachloromonoaquorhodate(III), (NH.sub.4).sub.2 RhCl.sub.5 (H.sub.2 O), is a useful photographic chemical. Small amounts of rhodium-containing, water soluble species remain in solution in the process liquor after synthesis. Most of the soluble rhodium values are present as the aforementioned ammonium complex; however there are traces of the cis and trans isomers of ammonium tetrachlorodiaquorhodate(III), and traces of the fac and/or mer isomers of rhodium(III) chloride triaquo complexes. Rhodium values present in the liquid as ammonium pentachloromonoaquorhodate(III) can be recovered by the addition of cesium chloride to form a precipitate identified as Cs.sub.2 RhCl.sub.5 (H.sub.2 O). Very little of the aforementioned fac and mer isomers or other contaminants, if any, are contained in the precipitate. The cesium rhodium pentachloride monohydrate product can be refined, for recovery of rhodium values, or used as an additive to a silver halide emulsion to control fog or stabilize the emulsion.

Dependencies are inferred from the claim text.