Thermodynamic investigation of methyl salicylate/1-pentanol binary system in the temperature range from 278.15 K to 303.15 K

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Densities ( ρ), speeds of sound ( u), isentropic compressibilities ( k s), refractive indices ( n D), and surface tensions ( σ) of binary mixtures of methyl salicylate (MSL) with 1-pentanol (PEN) have been measured over the entire composition range at the temperatures of 278.15 K, 288.15 K, and 303.15 K. The excess molar volumes ( V E), excess surface tensions ( σ E), deviations in speed of sound (Δ u), deviations in isentropic compressibility (Δ k s), and deviations in molar refraction (Δ R) have been calculated. The excess thermodynamic properties V E, σ E, Δ u, Δ k s, and Δ R were fitted to the Redlich–Kister polynomial equation and the A k coefficients as well as the standard deviations ( d) between the calculated and experimental values have been derived. The surface tension ( σ) values have been further used for the calculation of the surface entropy ( S S) and the surface enthalpy ( H S) per unit surface area. The lyophobicity ( β) and the surface mole fraction ( x 2 S ) of the surfactant component PEN have been also derived using the extended Langmuir model. The results provide information on the molecular interactions between the unlike molecules that take place at the surface and the bulk.