Density and Derived Thermodynamic Properties of 1-Ethyl-3-methylimidazolium Alkyl Sulfate Ionic Liquid Binary Mixtures with Water and with Ethanol from 288 K to 318 K

We present in this paper experimental measurements of density for pure ionic liquids of the 1-ethyl-3-methylimidazolium alkyl sulfate family, with the alkyl group being ethyl ([EMIM][ES]), butyl ([EMIM][BS]), hexyl ([EMIM][HS]), and octyl ([EMIM][OS]), and their binary mixtures with water and with ethanol in the whole composition range, at 288 K, 298 K, 308 K, and 318 K and under atmospheric pressure. The IL family chosen allows us to analyze the influence of the alkyl chain length of the anion. We compare results with those previously published by us and by other research groups, where the influence of the alkyl chain length of the cation in volumetric properties is studied. We observed that the density for both kind of binary mixtures decreases with the increase of the alkyl chain length of the anion and with the decrease of the molar fraction of ionic liquid. From density data we extract molar volumes and excess molar volumes. Molar volumes can be adjusted to a straight line versus the molar fraction, and the excess molar volumes values are very small (less than 0.5 % of the molar volume value) for all of the measured systems. This fact allows us to state that these binary systems are quasi ideal from the molar volume point of view. Finally we study the influence of temperature on this property by means of isobaric expansivity, finding very different results depending on the solvent used.