Solvent extraction of trace amounts of cobalt from pure reagent chemicals and its spectrophotometric determination with 2-nitroso-5-dimethylaminophenol

Abstract

Trace amounts of cobalt in pure reagent chemicals have been determined spectrophotometrically with 2-nitroso-5-dimethylaminophenol. Cobalt in amounts below 0·6 µg in the aqueous phase is extracted into 1,2-dichloroethane (5 ml) at pH 4 to 8. The excess of reagent and metal complexes other than the cobalt complex that are extracted into the organic phase are removed by extraction of the latter with 1 N potassium hydroxide solution followed by hydrochloric acid solution (1 + 2). The organic phase is then filtered through a dry filter-paper, and the absorbance of the organic phase measured in a cell of 50-mm path length at 456 nm. By using the above procedure, trace amounts of cobalt (10^–8 to 10^–4 per cent.) in sodium, potassium and iron(III) salts, etc., were determined by the standard addition method.