COMPARATIVE ANALYSIS OF MOLECULAR INTERACTIONS BETWEEN DRUGS OF AQUEOUS PROPYLENE GLYCOL WITH CERTAIN ALCOHOLS AT 308.15K: AN INSIGHT FROM DENSITY AND VISCOSITY STUDIES

Density, ρ and viscosity, η of drug of aqueous solution of propylene glycol (PG) (3 m and 7 m) with tert-butanol/2-propanol have been measured over the entire composition range of alkanols at 308.15 K. From this experimental data, excess molar volume, _, deviation in viscosity, Δη, and excess Gibbs free energy of activation of viscous flow, ΔG^*E have been determined. Positive values of Δη, ΔG^*E and negative values of  have been observed over the entire composition range in the mixtures studied. The observed positive and negative values of various excess/deviation properties have been attributed to the existence of strong interactions such as geometrical fitting of smaller molecules into the voids created by larger molecules in the liquid mixtures. The excess/deviation properties have been fitted to Redlich–Kister type polynomial and the corresponding standard deviations have been evaluated. The computed partial and excess partial molar volumes data also support the results. The experimental viscosity data of the liquid mixtures investigated have been correlated with viscosity models such as Grunberg and Nissan; Hind, McLaughlin and Ubbelohde;   Katti and Chaudhari.