Solute-solute and solute-solvent interactions of drug sodium salicylate in aqueous-glucose/sucrose solutions at temperatures from 293.15 to 318.15 K: A physicochemical study

Abstract

Physical properties like ultrasonic speed and compressibility give us an idea about the type of interactions prevailing in the solutions. Keeping this in view, we have measured the densities, ρ, ultrasonic speeds, u and viscosities, η of the drug sodium salicylate in water and in aqueous−D-glucose/d-sucrose (5 wt% and 10 wt% glucose/sucrose in water) solvents at different temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure. These experimental values have been used to calculate apparent molar volumes, Vϕ and apparent molar compressibilities, Ks,ϕ, limiting apparent molar volumes, Vϕ° and limiting apparent molar compressibilities, Ks,ϕ°. The transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr° of sodium salicylate from water to aqueous carbohydrate solutions were also calculated. The co-sphere model has been used to interpret the transfer molar properties. Using the η data, the viscosity A and B coefficients have been calculated. The variation of viscosity B coefficient with respect to temperature, i.e., dB/dT have been investigated, the sign of which is indicative of the structure making/breaking ability of the drug in these media. The free energy of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, enthalpies, ΔHο# and entropy, ΔSο# of activation of viscous flow, were also obtained from the viscosity data. The results obtained are discussed in terms of solute-solute and solute-solvent interactions prevailing in these solutions.