Thermodynamics of K₂HPO₄/d-Sucrose/Water System at 298.15 K: Experiment and Modeling

Thermodynamic properties of K 2 HPO 4 / d -sucrose/water ternary solutions were investigated at 298.15 K. Water activity, osmotic coefficient, and electrolyte saturation points are determined by measuring relative humidities in the wide range of K 2 HPO 4 molality (ranging from 0.1 to approximately 5 mol·kg –1 ) and for various d -sucrose contents (0.1, 0.3, 0.5, 1, 2, 3, 4, 5, and 5.5 mol·kg –1 ) in the ternary K 2 HPO 4 / d -sucrose/water system. The solid state was characterized using powder X-ray diffraction (XRD) and attenuated total reflection Fourier-transform infrared (ATR-FTIR) techniques. The obtained data were then analyzed using the Pitzer-Simonson-Clegg (PSC) model to determine several thermodynamic properties. These properties encompass the stoichiometric ionic mean activity coefficient of K 2 HPO 4, excess Gibbs energy, solubility in aqueous solutions, and the Gibbs energy of transfer of K 2 HPO 4 between water (W) and d -sucrose/water (W+S) mixtures. Furthermore, the interactions among water, d -sucrose, and K 2 HPO 4 are also examined and discussed.