The kinetics of the formation of 1:1 complex of chromium(III) with ethylenediaminetetra-3-propinate (EDTP) was followed spectrophotometrically at lmax = 557 nm. The reaction was found to be first order in chromium(III) and was accelerated by EDTP. Increasing the pH from 3.3 to 4.7 accelerated the reaction rate, the reaction rate was retarded by increasing ionic strength and dielectric constant of the reaction medium. A mechanism was suggested to account for the results obtained which involves ion pair formation between the various species of the reactants. Values of the activation parameters obtained indicate an associative mechanism.
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