Volumetric and viscometric studies of nicotinic acid in aqueous solutions of sodium malonate at T = (298.15–318.15) K

Abstract

Densities and viscosities for the solutions of nicotinic acid in aqueous sodium malonate solutions with several molalities (msodium malonate=0.000, 0.005, 0.010, 0.015 and 0.020mol·kg-1) of sodium malonate were determined at T=(298.15–318.15)K and at pressure p=101kPa. Apparent molar volume (ϕV standard partial molar volume (ϕV0 the slope (SV∗), standard isobaric partial molar expansibility (ϕE0) and its temperature dependence (∂ϕE0/∂T)P, the viscosity B-coefficient and solvation number (Sn), etc., were determined. Using the experimental data viscosity B-coefficients were further utilized to obtain the free energies of activation of viscous flow per mole of the solvents (Δμ10≠) and of the solute (Δμ20≠). Effects of molality, solute structure and temperature on all these parameters were analyzed in term of ion–ion and ion–solvent interactions; results revealed that the solutions are characterized predominantly by ion–solvent interactions and nicotinic acid behaves as a long-range structure maker.