Thermodynamic analysis of tartaric and lactobionic acids with aqueous potassium benzoate mixtures through volumetric and acoustic methods

• Density and sound speed measurements of tartaric and lactobionic acids in aqueous potassium benzoate solutions. • The expansibilities are calculated using thermal, pair, and triplet coefficients. • Molecular interactions between the solutes and solvents were analyzed in the liquid mixtures. • Strong solute-solvent, ion-ion, ion-hydrophilic, hydrophilic-hydrophilic interaction occurs. • Hydration numbers were estimated based on compressibility data. The molecular behavior of ternary liquid systems containing potassium benzoate and water-soluble organic acids (tartaric and lactobionic acids) was studied through measurements of density and ultrasonic velocity at varying concentrations (0.000-0.035) mol‧kg −1 and temperature varying from (288.15-318.15) K. Derived thermodynamic parameters such as apparent and partial molar volumes, apparent and partial molar isentropic compressibilities, expansibilities, transfer characteristics, thermal expansion coefficients, interaction coefficients were analyzed through investigated data from DSA 5000M to understand interactions. The structural influence of solutes in the solution, whether promoting or disrupting molecular order was interpreted using Hepler’s thermodynamic criterion and the co-sphere overlap hypothesis. Hydration numbers were estimated using Passynski’s relation based on compressibility data. These results contribute to the progress of stable and efficient formulations across various chemical, food, cosmetic, and pharmaceutical formulations.