Dielectric relaxation in non aqueous solutions. Part 2.—Solutions of tri(n-butyl)ammonium picrate and iodide in polar solvents

The permittivity and loss of solutions of tri(n-butyl)ammonium picrate and iodide in various polar solvents have been measured at a number of frequencies between 0.2 and 3.0 GHz. The relative static permittivities of the pure solvents used range from 3.37 to 20.7 at 25°C. For all the solutions investigated, the observed dispersion of permittivity is adequately described by a single relaxation time, which for a given solvent depends on the concentration as well as the nature of the solute. Apparent dipole moments evaluated from the dispersion amplitude by means of Bottcher's theory, on the assumption that the dipole occupies a spherical cavity, are 12.3±0.4 D and 11.2±0.6 D for the picrate and iodide respectively. These values indicate that the relaxing dipole is an ion pair. Dielectric relaxation times corrected for internal field effects by different relations are compared with those calculated from the partial molar volume of the solute and the viscosity of the solvent by means of the Debye-Stokes equation. Density data for solutions of the two salts in 1,2-dichloroethane are included and from these data, partial molar volumes of the salts have been evaluated.