Thermodynamic Investigation of Magnesium Salicylate Solutions with Sodium Salts by Volumetric and Acoustic Approach

We conducted volumetric and acoustic studies on binary and ternary aqueous systems of magnesium salicylate with salts (sodium nitrate and sodium bicarbonate) to explore solute–solvent and solute–solvent interactions. Aqueous magnesium salicylate solutions (0.010, 0.030, and 0.050 mol·kg–1) were prepared as solvents, and salts were added to achieve molalities ranging from 0.10 to 0.50 mol·kg–1. We measured density and ultrasonic velocity using an Anton Paar DSA 5000 M. From these experimental data, we evaluated apparent and partial molar volumes, transfer volumes, isentropic compressibilities, and their corresponding pair and triplet interaction coefficients with derivative properties such as (∂Eϕ0∂T)p. Additional thermodynamic parameters, such as thermal expansibility, expansion coefficient, relative association, relaxation strength, and specific heat, were also calculated. The results reveal specific ion–dipole and hydrogen-bonding interactions governing solute–solvent association and hydration phenomena, which are particularly relevant to the formulation stability and solution behavior of magnesium salicylate-based pharmaceutical systems.