Study on solid–liquid phase equilibria in ionic liquid: 2. The solubility of alkali bromide in ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate

This paper reports the solubility of alkali bromide MBr (M is Na or K) in ionic liquid (IL) EMISE (1-ethyl-3-methylimidazolium ethyl sulfate), measured in the temperature range of 293.15–343.15 K. The relationship between solubility, m, and temperature, T, may be expressed in an empiric formula: ln(m/m0) = A1 + A2T0/T, where T0 is 1 K, m0 is 1 mol kg−1. The observed sequence of solubility is NaBr > KBr. The fact implies that the less the radius of alkali ion, the greater is its solubility because small ion is easy to get into the interstices of IL EMISE. In addition, the standard transfer thermodynamic functions of MBr from water to IL EMISE were calculated in terms of solubility data of MBr in water. Using Born model, the dielectric constant, D = 8.7, was estimated and was close to the value of typical IL measured by Wakai.