Determination of metallic and “oxide” copper in ores

Abstract

The selective determination of metallic copper in the presence of copper sulphides and oxides is performed by removal of these oxides or sulphides by means of a cyanide-hydrazine leach solution (pH 12 ± 0.2), washing the residue and dissolving the metallic copper in nitric acid. The copper in this solution is then determined by an atomic-absorption spectrophotometric or spectrophotometric (cuprizone) procedure. The recovery of metallic copper is about 98.6% and the average standard deviation ±0.003% for the range 0.011–0.142%.

The “oxide” copper is dissolved out of another portion of sample by means of an ammonia-ammonium chloride-sodium pyrophosphate leach. The solution is filtered and the copper(I) in the filtrate is oxidised with hydrogen peroxide and the absorbance of the filtrate is measured at 610 nm. The method determines “oxide” copper(I) and copper(II) and neither metallic nor trivalent iron interferes. The average standard deviation is ±0.003% for the range 0.01–1.15% of “oxide” copper.