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