Investigation on molecular interactions of nicotinamide in aqueous citric acid monohydrate solutions with reference to manifestation of partial molar volume and viscosity B-coefficient measurements

Abstract

Apparent molar volumes ( V ϕ), viscosity B-coefficients for nicotinamide in 0.03, 0.05, 0.07 and 0.10 mol dm −3 aqueous citric acid monohydrate solutions have been determined from solution density and viscosity measurements at 298.15, 308.15 and 318.15 K as function of concentration of nicotinamide. The apparent molar volumes have been extrapolated to zero concentration to obtain the limiting values at infinite dilution using Masson equation. The infinite dilution partial molar expansibilities have also been calculated from the temperature dependence of the limiting apparent molar volumes. This results have, in conjunction with the results obtained in pure water, been used to calculate the standard volumes of transfer Δ V ϕ 0 and viscosity B-coefficients of transfer for nicotinamide from water to aqueous citric acid monohydrate solutions for rationalizing various interactions in the ternary solutions. The structure making or breaking ability of nicotinamide has been discussed in terms of the sign of ∂ 2 V ϕ 0 / ∂ T 2 p and dB/ dT. An increase in the transfer volume of nicotinamide with increasing citric acid monohydrate concentration has been explained by Friedman–Krishnan co-sphere model. The activation parameters of viscous flow for the ternary solutions studied have also been calculated and explained by the application of transition state theory.