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 V ^E, refractive index deviations Δn_D 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 V^E are negative for the entire mole fraction range covered for all these binary mixtures and increased with temperature, whereas the values of Δn_D 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.