Investigation of dielectric relaxation time and viscosity of polar-non polar liquid mixtures as a function of temperature

Abstract

The object of the work was to investigate whether the relaxation time of a polar molecule in solution in a non-polar solvent is controlled by the viscosity of the solution (as is implied by Debye's theory) or by a mutual viscosity which is a measure of the solute solvent interactions. Measurements have been made on viscosity, density, refractive index, complex permittivity at a wavelength of 3.33 cm of polar and non-polar mixtures. The non-polar liquids used were benzene and carbon tetrachloride and the polar ones were chloroform, chlorobenzene and t-butylchloride. The measured permittivity and loss together with refractive index values were used to calculate the relaxation times at different concentrations of the liquid mixtures. The mutual viscosity values were determined from the density, solution, solvent and solute viscosities, for the benzene solutions the temperature range used was 10°C to 60°C and for the carbon tetrachloride solutions it was -10°C to 40°C. The results were analysed as functions of temperature and also as concentration. The relaxation times, solution viscosities and the complex viscosity terms all behave as expected when studied as functions of temperature, that is, all these terms decrease with the increase of temperature. The ratios were (within experimental error) both constant with change of temperature which make it impossible to discriminate between the two theories (eta, the solution viscosity, and e, is the viscosity term taking into account the mutual viscosity). The results when studied as functions of concentration seemed to indicate that there is no direct dependence of relaxation time on the viscous properties of the liquid mixtures.