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Abstract
The abstraction of cyanide ion from hexacyanoferrate(II) by Hg(II) as a catalyst has been studied spectrophotometrically in the presence of α‐Nitroso‐β‐Naphthol (αNβN). When Hg(II) is present in different stoichiometric amounts with [Fe(CN)6]4−, abstraction of two cyanide ions per ion of Hg(II) takes place with the formation of three different green colored complexes [Fe(CN)4(αNβN)]2−, [Fe(CN)2(αNβN)2], and [Fe(αNβN)3]2+. However, when Hg(II) is present in catalytic amounts in the range of 1 × 10−6 − 1 × 10−5 mol l−1 a single ternary complex of the type [Fe(CN)4(αNβN)2]2− is formed which is intensely green in color and quite stable. The effects of pH, concentration of reactants, and temperature have been studied. A detailed kinetic study of cyanide abstraction is reported and a probable mechanism consistent with the experimental data has been proposed. This catalytic observation formed the basis for development of a catalytic kinetic method for determination of Hg(II) using the titled ligand exchange reaction. The reaction has been well suited for the determination of Hg(II) in various spiked water samples with 97 ∼ 103% recoveries. The relative standard deviation and percentage error in various determinations of Hg(II) have been reported. The effect of various interfering ions have been studied and discussed. The interference by various closely associated metal ions on the determination of Hg(II) have been studied using synthetic water samples.
Acknowledgement
The author is grateful to Prof. P.C. Nigam for helpful discussion and to the authorities of the Indian Institute of Technology, Kanpur, India for providing a laboratory facility to do this work when he visited India.