Diffusion phenomena and metal complex formation equilibria. Part 1.—CdII–thiourea systems in aqueous and mixed-solvent media

Abstract

Changes in polarographic diffusion current of the cadmium(II) aquo complex when consecutively complexed with thiourea and substituted thioureas are directly related to commonly used polynomial functions of free-ligand concentration involving overall formation constants. Pseudo-formation curves are defined and their analysis exploited as a means of obtaining formation-constant data; these are essentially in agreement with those generated by more conventional methods when these are applicable. It is shown that the average diffusion coefficient of a system of metal complexes in equilibrium depends upon the free-ligand concentration in a manner which is a function of both the nature of the ligand and the solvent medium.