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.