Department of Chemistry, University of Lucknow, Lucknow-226 007 Department of Phatmacokinetic Division, Central Drug Research Institute, Lucknow Manuscript received 23 May 1994, accepted 5 July 1994 The kinetics of oxidation of ethylenediaminetetraacetic acid (EDTA) by hexacyanoferrate(m) have been studied spectrophotometrically (λ = 420 nm) at pll = 11.0, I = 0.5 mol dm-3 (NaCIO4) and temperature 45°. The examination of rate data shows that the rate law is d[Fe(CN) ]/dr = kf [Fe(CN)] [EDTA4-

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... th a second order rate constant kI = 4.5 x 10-2 dm3 mol-I s-I. The rate of reaction has been followed as a function of pH in the range 7.5-12.0. The rate is found to increase. The reactive species of EDTA are H2L2-, HL3- and L4-. The resolved rate constants due to the reaction of [Fe(CN)6]3- with EDTA4-, HEDTA 3- and H2EDTA2- are calcu­lated. The effect of ionic strength is found to be positive. The activation parameters are also calculated from Arrhenius plots. An electron transfer mechanism is suggested for the reaction.