Dielectric relaxation time, a non-linear function of solvent viscosity

Abstract

By extending the Debye and Wirtz treatments to the case where the frictional force opposing rotation of the molecule differs from that of the bulk liquid, the relaxation time (τ) is found to depend non-linearly upon the macroscopic viscosity (η). The resulting expression is of the form τ=τ′η/(η+η′). When ηη′ it reduces to a Debye-like equation but when η increases τ does not increase in proportion but eventually approaches a constant value. Relaxation time data for a large number of solutions are found to conform to this relationship over the viscosity range 0.3 to 200 cP.