Nitrosophenol and nitrosonaphthol derivatives as reagents for the spectrophotometric determination of iron and determination of micro-amounts in waters with 2-nitroso-5-dimethylaminophenol

Abstract

Twenty-five nitroso compounds have been examined for suitability as organic analytical reagents for the spectrophotometric determination of iron(II) ion. The complexes formed by 2-nitroso-5-dimethylaminophenol (nitroso-DMAP) and 2-nitroso-5-diethylaminophenol (nitroso-DEAP) with iron(II) are shown to have a 1:4 composition and the other iron(II) complexes a 1:3 composition. Nitroso-DMAP and nitroso-DEAP were found to be very sensitive reagents for iron(II) ion, the molar absorptivities of their complexes being about 4 × 10⁴ at about 750 nm in aqueous solution. The colour of the nitroso-DMAP-iron(II) complex is very stable in aqueous solution at about pH 8, while that of the nitroso-DEAP complex is less stable. Nitroso-DMAP is more useful for the determination of micro-amounts of iron than nitroso-DEAP, because of the greater stability of the reagent and the complex formed and the solubility of the latter in aqueous solution.

Diverse ions, which are generally present in city and river waters did not interfere in the direct spectrophotometric determination of micro-amounts of iron in these waters with nitroso-DMAP.