Effect of relative humidity of air on density, apparent molar volume, viscosity, surface tension, and water content of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid

The effect of relative humidity (RH) of air on the water content, density, apparent molar volume, dynamic viscosity, and surface tension of the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate has been studied. Physical property measurements were conducted at a temperature of 298.15 K, at atmospheric pressure, and in a RH range of (0 to 100) %. The experimental data were fit to first- and third-order polynomials that relate the physical properties with the relative humidity of air and the water content of [emim][EtSO4] with correlation coefficients higher than 0.9. The apparent molar volume was fit by the Redlich-Mayer equation with a relative standard deviation (a) less than 2 cm(3) . mol(-1). Excess molar volumes, viscosity, and surface tension deviations of a mole fraction average were calculated, and a second- and third-order Redlich-Kister polynomial was applied (sigma equal to 0.01 cm(3).mol(-1), 0.5 mPa.s, and 0.6 mN.m(-1), respectively).