Densities, Refractive Indices and Excess Molar Volumes for Binary Mixtures of Protic Ionic Liquids with Methanol at T = (293.15 to 313.15) K

Densities and refractive indices for the binary mixtures involving four different Protic Ionic Liquids (PILs) namely (2-Hydroxyethanaminium formate [HEF] + methanol), (2-Hydroxyethanaminium acetate [HEA] + methanol), (2-Hydroxyethanaminium propionate [HEP] + methanol), and (2-Hydroxyethanaminium lactate [HEL] + methanol) have been measured at the temperature range from (293.15 to 313.15) K and at atmospheric pressure. The excess molar volumes VE, refractive index deviations ΔnD for these binary mixtures were calculated and correlated using Redlich-Kister equation. The coefficients of thermal expansion α, were also calculated from these experimental data. The values of VE are negative for the entire mole fraction range covered for all these binary mixtures and increased with temperature, whereas the values of ΔnD are positive and also increased with temperature. The measured refractive indices were compared with those predicted using the Lorentz–Lorenz, Gladstone–Dale, and Eykman equations and a satisfactory agreement was found for all the binary systems (PILs + methanol) studied in the present work.