IONIC STRUCTURE IN A BINARY-FLUID

The tracer diffusion coefficient D3+ of the trivalent lanthanide cation Gd-153(3+) is studied in mixtures of isobutyric acid, water and 5 x 10(-4) M Gd(NO3)3 using an open-ended capillary tube. These data are given over the complete composition range at T - T(c) = 0.171 K. The coefficients D3+ are combined with the shear viscosity eta of the electrolyte. The results are discussed in terms of the Einstein-Stokes law; our analysis suggests three different behaviours of the diffusing entity in the mixtures and it is based on the preferential solvation phenomenon.