Abstract
The measurement of ionic self-diffusion coefficient D of the trivalent lanthanide ion Eu-152(III) in asymmetrical electrolytes of Eu(ClO4)(3) in hydro-organic water-dioxane mixtures (at a low dielectric constant) at 298.15 K, by the open-end capillary method gives evidence of the progressive association of ion pairs. The study of the different physicochemical properties in all the domains of composition shows the existence of three distinct behaviours. The application of association theory to such an asymmetrical electrolyte (3 : 1) with a polyvalent cation enables us to delimit the validity of the Bjerrum and Fuoss's association theories. Since there is similarity of the coordination chemistry of trivalent lanthanide and actinide ions, this study comes within the framework of previous works of the investigation of structure properties of the f-elements in solution carried out in some previous papers.