Studies on Volumetric Properties of Concentrated Aqueous Solutions of the Ionic Liquid BMIBF4

In order to test the mole-fraction composition-based models as applied to aqueous solutions of an ionic liquid, the densities of aqueous 1-methyl-3-butylimidazolium tetrafluoroborate (BMIBF₄) were measured using a Westphal balance in the concentration range of about 0.2 to 0.85 mole fraction at temperatures from 283.2 to 323.2 K. Values of the apparent molar volumes of concentrated aqueous BMIBF₄ solutions were calculated from these densities and were represented with the Pitzer–Simomson and the Pitzer–Simomson–Clegg equations. The values of Pitzer–Simomson parameters and Pitzer–Simomson–Clegg parameters were obtained by fitting to experimental data with small standard deviations.