Density and Surface Tension Measurements of Imidazolium-, Quaternary Phosphonium-, and Ammonium-Based Room-Temperature Ionic Liquids:  Data and Correlations

Abstract

Presented are experimental densities and surface tensions of imidazolium-, quaternary ammonium-, and phosphonium-based room-temperature ionic liquids (RTILs) in the temperature range of (298 to 350) K. Densities of the RTILs decrease slightly with temperature in the studied range (298 to 333) K. At 298 K, the densities of the phosphonium-based RTILs ranged from (0.88 to 1.05) g·cm -3, while those of the ammonium-based RTILs ranged from (1.08 to 1.37) g·cm -3 . The volume expansivities of phosphonium and ammonium RTILs at 1 atm and 298 K are in the range of (5.5 to 6.5)·10 -4 K -1 . Surface tension and temperature relationships were established using the van der Waals−Guggenheim equation, σ = E s (1 − T / T c ) n, where n ≈ 1, for the RTILs studied. The Macleod−Sugden−Wright (MSW) equation was used to correlate surface tension with the respective molar volume of the various RTILs. The developed equation can accurately correlate surface tension for this grouping of RTILs with a maximum estimated error of 0.15 % within the temperature ranges considered.