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A rapid colorimetric solvent-extraction procedure for the determination of cyanide in gold-mill effluents and receiving waters

1970

Abstract

A colorimetric procedure is described for the determination of the total cyanide content of effluents from gold cyanidation plants and of water from basins into which they discharge. The method has several advantages over the official American Water Works Association Methods for routine mill use. First, the colour reagent is stable and easily prepared. Second, the initial colour development, which takes only 25 minutes, provides a visual indication as to whether the cyanide content exceeds 0.5 ppm and hence permits a quick screening-out of high-level samples. Determinations on samples with lower cyanide content can then be completed within an additional 45 minutes by a simple solvent extraction-spectrophotometric step. Actual working time is of the order of 20 minutes per sample and, since equipment requirements are minimal, a high throughput is possible. The method determines cyanide present as hydrocyanic acid, cyanide ion, zincocyanide, cuprocyanide and nickelocyanide, but not cyanide present in the form of ferrocyanide or cobalticyanide. It is free from interference by thiocyanate or cyanate and other common constituents of gold-mill effluents. It is also unaffected by the Products resulting from the decomposition of cyanide by hypochlorite; and, by means of an addition of sodium arsenite to the sample, the interfering effect of hypochlorite itself can be eliminated. It can therefore be used as a means of following the progress of the hypochlorite process for the destruction of cyanide.

Abstract

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