Ionic self-diffusion coefficients of (III) in solutions in water - dioxan mixtures at

The measurement of ionic self-diffusion coefficients of the lanthanide ions (III) in asymmetrical electrolytes (3:1) solutions of in hydro-organic water - dioxan mixtures (at a low dielectric constant) gives evidence of the progressive association of ion pairs. The study of different physical - chemical properties in all the domains of composition shows the existence of three regions with 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 theories.