Effect of temperature and concentration on the thermo-acoustic behavior of vitamin B5 (d-Panthenol) solutions in the presence of glycol additives

This study examines the influence of temperature and concentration on the thermo-acoustic properties of binary [propylene glycol (PG)/hexylene glycol (HG) + water] and ternary (PG/HG + d-Panthenol + water) liquid systems. Density and ultrasonic velocity measurements were carried out over the temperature range 288.15-318.15 K at d-Panthenol concentrations of 0.04, 0.08, and 0.12 mol/kg under ambient pressure. Apparent and partial molar volumes [Vϕ and Vϕ0 respectively] and transfer partial molar volumes [ΔVϕ0] were evaluated from density data to investigate solute-solvent interactions. Acoustic parameters, including apparent and partial molar compressibility [Kϕ,S and Kϕ,S0 respectively] and their transfer values [ΔKϕ,S0] were determined using ultrasonic velocity measurements. Positive values of Kϕ,S0 for binary systems indicate the dominance of solvent intrinsic compressibility over solute effects. Pair-triplet interaction coefficients, partial molar expansibility (Eϕ0), and its temperature derivative ∂Eϕ0/∂TP were also analyzed to elucidate temperature-dependent molecular interactions. Additionally, apparent specific volume (ASV), relative association, and relaxation strength were employed to assess solvation behavior and taste-related characteristics. The results demonstrate strong temperature- and concentration-dependent intermolecular interactions, providing valuable insights for pharmaceutical, food, and cosmetic formulations involving vitamin B5 and glycol-based additives.