Study of the volumetric properties of the aqueous ionic liquid 1-methyl-3-pentylimidazolium tetrafluoroborate

This paper reports the densities of aqueous solutions of the ionic liquid (IL) 1-methyl-3-pentylimidazolium tetrafluoroborate ([pmim][BF4]) that were measured from 278.15 to 343.15 K, at intervals of 5 K, using an Anton Parr model DMA 4500 oscillating U-tube densitometer. The apparent molar volume, phi V-B, and the partial molar volume of [pmim] [BF4], V-B, were calculated. The values of the apparent molar volume, phi V-B, were fitted to Pitzer's model for volumetric properties by the method of least-squares, which allowed the partial molar volume of the IL at infinite dilution, V-B(o), and Pitzer's parameters, ss((0)V)(M,X) and ss(M,X),((1)V) to be obtained. The small standard deviations of the fits show that Pitzer's model is also appropriate for representing the volumetric properties of aqueous solutions of the ionic liquid [pmim][[BF4].