DIELECTRIC-RELAXATION OF AQUEOUS-ELECTROLYTE SOLUTIONS .2. ION-PAIR RELAXATION OF 1/2, 2/1, AND 2/2 ELECTROLYTES

The low-frequency relaxation process contributing to the complex permittivity spectra of aqueous solutions Of MgSO4, CdSO4, Na2SO4, CdCl2, and CuCl2 is investigated. The dispersion amplitudes are analysed with the help of model calculations, based on a modified Cavell equation for ellipsoidal bodies. It is shown that ion pairs are responsible for the low-frequency relaxation process with solvent separated ion pairs dominating for the sulfates, whereas contact ion pairs are formed by the chlorides. The observed relaxation time is analysed as the superposition of chemical and reorientational relaxation. For the ion pairs the effective volumes of rotation and the rate constants of formation are determined. The results are compared with information from the literature.