Dielectric relaxation in non-aqueous solutions. Part 4.—Solutions of tri(n-butyl)ammonium picrate in benzene

Abstract

The dielectric relaxation times (τ) of solutions of tri(n-butyl)ammonium picrate in benzene have been found to increase linearly with increasing concentration of salt, although when the temperature is raised the slope (∂τ/∂c)_T is reduced. Limiting values of τ obtained by extrapolation to infinite dilution are similar in magnitude to the reduced relaxation times τ* defined by the relation τ*=τ(ε_∞+ 2)/(ε_s+ 2), where ε_s and ε_∞ are the low and high frequency limiting permittivities of the solution. Apparent enthalpies of activation also increase with increasing concentration, while the corresponding pre-exponential factors decrease with increasing concentration. The viscosity of the solution has been found to be a quadratic function of concentration.

From these observations, it has been concluded that the concentration dependence of the experimental relaxation times is due to electrostatic dipole-dipole interactions between individual ion pairs. Density data, from which the partial molar volume of the dissolved salt has been calculated, are also included.