Influence of protonation on physico-chemical properties of metal extractants

Summary The protonation constants of several metal extractants, especially hydroxamic acids have been determined by a solvent extraction method. The influence of the acidity on the solubility and the distribution ratio has been studied. A plot correlates the protonation behaviour of these metal extractants with the Hammett Acidity Function, H_o. The protonation constant is useful to explain the acid catalysed hydrolysis rate of these metal extractants and to determine the extraction coefficients of their metal chelates.