Diffusion phenomena and metal complex formation equilibria. Part 2.—CdII–benzimidazole and NiII–oxalate systems in aqueous solution and general treatment of ion–molecule interactions

Abstract

The nature of pseudo-formation curves is examined and the profiles of such plots are shown to be unique to given interacting systems for constant conditions; unambiguous verification of the number of individual reactions which occur is possible. Systems containing Cd^II and Ni^II show contrasting electrochemical behaviour, and the stabilities of the interactions investigated are significantly different. These have been chosen because formation-constant data have been determined independently and allow verification of the methods developed here. Generation of consecutive overall and step formation constants via analysis of a pseudo-formation curve is shown to be feasible for systems in which, to date, only the constant K′=(β_N)^1/N is known. Complexes formed by competition by H₂O₂ for hydration molecules of Rb⁺, Cs⁺ and F^– ions exemplify this category.