Investigation of Thermodynamic and Spectroscopic Interactions in Sodium Salicylate Solutions with Sodium Salts at Varying Temperatures

Abstract

The current study examines the thermodynamic behavior of ternary solutions containing sodium salicylate, with sodium chloride (NaCl) and sodium Sulfate (Na₂SO₄). Density and sound velocity measurements were conducted over a temperature span of (288.15 to 318.15 K) at a frequency 3 MHz and 0.1 MPa. With density data, V_ϕ (apparent molar volume), V_ϕ⁰ (partial molar volume), and transfer molar volume (ΔV_ϕ⁰) were determined, while sound velocity data were used to compute apparent and partial isentropic compressibilities (K_ϕ,s and K_ϕ,s⁰). The analysis of pair and triplet interaction coefficients, with derivative properties such as ${(\partial E_{\varphi }^0/\partial T)}_p$, provided insights into solute–solute along with solute–solvent interactions, determining the structure-making or structure-breaking nature of the solutes in the system. The results were further analyzed using the cosphere overlap model, and McMillan-Mayer theory which explains the influence of solute aggregation on volumetric and acoustic properties. Additionally, FTIR spectroscopy was performed on sodium salicylate solutions with NaCl and Na₂SO₄ to investigate molecular interactions. The findings contribute to a better understanding of the physicochemical properties of these ternary systems, which are relevant to applications in chemical and material sciences.