Suggested Use of a Bismuth Mercaptoimidazole Compound as a Specific Colour Reagent for Iodides

Abstract

THE reaction of bismuth salts with certain organic thio-compounds, for example, thiourea and dimercaptothiodiazole, to form coloured complexes of the metal is a well-known analytical procedure. Other workers (cf. Naiman¹) have reported on the detection of bismuth with a mixture of 2-methyl-benzothiazole and potassium iodide, which results in the formation of a coloured complex iodide. However, the use of such a reaction for the detection of iodides does not appear to have been reported, probably on the basis of specificity. In certain work on the colorimetric detection of mercaptoimidazoles, I found² that the yellow metallic complex, formed by the interaction of bismuth sulphate (acid) and l-methyl-2-mercaptoimidazole, reacted with iodide ions to form an intensely coloured complex iodide. Since the reaction has been found to be specific for iodides, the use of such a reagent for their detection is suggested.