Ligand exchange kinetics in the calcium-EDTA system

Abstract

Rate constants and associated enthalpies and entropies of activation have been determined for reactions occurring at equilibrium in solutions containing K₂C_aEDTA and K_αH₄-_αEDTA, where x is a stoicheiometric number. The reactions, which include exchange between the bound ligand in CaEDTA^2- and the various protonated forms of the free ligand as well as the formation and decomposition reactions of CaEDTA^2- and CaHEDTA-, have been investigated by N.M.R. techniques using the Job method of continuous variations. Reaction mechanisms are proposed.