Dielectric relaxation times (t) have been determined for phenol,o-cresol,m-cresol andp-cresol in solutions ofn-heptane+paraffin oil of varying viscosities. Since, all the four systems contain an -OH group, capable of group rotation, the dielectric absorption was further resolved using Higasi, Koga and Nakamura method in terms oft(1) andt(2). In each case the dielectric relaxation time has been found to be maximum in the neighbourhood of 75%n-heptane+25% p.o. in the mixture. On further increasing the viscosity of the medium, theT values shorten. The results obtained suggest the associative nature of the compounds investigated.

The viscous nature of binary liquid solutions of non-polar solvents,viz. n-heptane, benzene, carbon tetrachloride and paraffin oil has been studied in terms of the deviation from the ideal law. The ideal law is supposed to take the form of (weighted) geometric mean. The viscous behaviour has been observed over a range of temperatures (298–322°K). The relative excess volume and relative excess enthalpy of activation have been evaluated to study the increase in viscosity associated with the shrinkage in mixing of its components.

Dielectric studies in dilute solutions of cyclohexane and benzene have been carried out in the temperature range 294–318°K. The observed data have been utilized to evaluate the relaxation times and thermodynamic parameters of these molecules. The high values ofα for 2-acetyl pyridine indicate the occurrence of more than one relaxation time. In the remaining systems, the observed lowα values indicate their rigid behaviour. The variation in the dielectric relaxation time is mostly correlated with the change in the heterocyclic configuration of the system.

Dielectric measurements on three heterocyclic compounds namely pyrrolidine, piperidine and 2-acetylpyridine in paraffin oil and paraffin oil + cyclohexane mixtures over the temperature range (294–318 K) at 9.8 GHz have been made. The data have been analysed using the method of Higasiet al and their dependence on macroscopic viscosity has been examined. The effect of solvent viscosity on the dipolar rotational process of the molecules in highly viscous media is also discussed.