Effect of Sodium Sulphate on the Volumetric, Rheological and Refractometric Properties of some Disaccharides in Aqueous Solutions at Different Temperatures

Abstract

Density,ρ, viscosity,η, and refractive index,n, of some disaccharides [D(+)-cellobiose, D(+)-lactose monohydrate, D(+)-maltose monohydrate and sucrose] in water and in 0.49850 and 0.99705mol kg-1aqueous solutions of sodium sulphate [Na2SO4] have been measured at four temperatures [288.15, 298.15, 308.15 and 318.15K]. From these data, the apparent molar volumes,VΦ, and viscosity-B-coefficients using Jones–Dole equation have been determined at different temperatures. The partial molar volumes of transfer,ΔtV20at infinite dilution and B-coefficients of transfer,ΔtB, have been estimated for transfer of disaccharides from water to aqueous sodium sulphate solutions. Partial molar expansion coefficients, (∂V20/∂T)Pand dB/dTcoefficients have also been calculated. Gibbs free energy of activation of viscous flow has been calculated by using Feakin´s transition-state theory for the studied systems. D(+)-Cellobiose has shown characteristically different hydration behaviour among the studied disaccharides. The signs and magnitude ofΔtV20, andΔtB parameters have been discussed in terms of various interactions occurring in these solutions.