Interactional Behavior and Hydration Characteristics of Polyhydroxysolutes (d(+)-Xylose and d(−)-Ribose) in Aqueous Solutions of Dipotassium Oxalate at Different Temperatures

Abstract

Thermodynamic properties revealing the hydration characteristics and structural effects of saccharides in mixed aqueous solutions generate considerable information for the growth of pharmaceutical and food industries. In this study, the apparent molar volumes, Vϕ, and the apparent molar isentropic compression, Kϕ,s, for monosaccharides (d(+)-xylose and d(−)-ribose) within the concentration range 0.1–1.0 mol·kg–1 in 0.0, 0.2, 0.4, and 0.6 mol·kg–1 aqueous solutions of dipotassium oxalate (K2C2O4) have been calculated from densities and speeds of sound measured at temperatures T = 288.15, 298.15, 308.15, and 318.15 K and experimental pressure p = 0.1 MPa. Thermodynamic parameters, partial molar volumes, Vϕo, partial molar volumes of transfer, ΔVϕo, partial molar isentropic compression, Kϕ,so, and partial molar isentropic compression of transfer, ΔKϕ,so, and hydration numbers, Nw, are also derived for the said monosaccharides. The effect of temperature on these parameters is studied, and further the expansion coefficients, (∂Vϕ0/∂T)p, (∂2Vϕ0/∂2T)p, and pair (VAB, KAB) and triplet (VABB, KABB) interaction coefficients are determined for monosaccharides. The results indicate the occurrence of strong solute–cosolute (hydrophilic–ionic and hydrophilic–hydrophilic type) interactions in these systems, which increase with the increasing concentration of saccharides and dipotassium oxalate.