Prediction of Internal Pressure of Binary Liquid Mixtures Using Flory's Statistical Theory

Estimation of Ultrasonic Velocity, Density, Internal Pressure, and Thermophysical Parameters of Ionic Liquid Mixtures: Application of Flory's Statistical Theory

Flory's statistical theory (FST) has been employed to estimate the ultrasonic velocity, density, internal pressure, and several important thermophysical parameters such as the energy of vaporization, the heat of vaporization, cohesive energy density, polarity index, and solubility for eight binary mixtures of ionic liquids and water within the temperature range of 288.15 to 308.15 K. The ionic liquids chosen for this investigation are [BMim][dca], [BMim][TfO], [BMpy][TfO], [BMpyr][dca], [BMpyr][TfO], [EEPy][ESO4], [HMim][dca], and [MPy][MSO4]. The predicted values of ultrasonic velocity and density show good agreement with the data reported in the literature. It endorses the applicability of FST to these binary mixtures. A comparative analysis of the internal pressure values (Pi) determined by using FST and the standard thermodynamic approach is also presented. The results obtained for Pi using both approaches show good agreement. Besides, for the mixtures under study, the correlation between ultrasonic velocity, density, and surface tension has also been examined. The variation of thermophysical parameters with concentration and temperature changes has been utilized to explore the nature and strength of the solute-solvent interactions prevalent in these mixtures. It is pointed out that A-A-type interactions dominate over A-B-type interactions in water-rich regions of the mixtures.

Comments on ‘Prediction of internal pressure of binary liquid mixtures using Flory's statistical theory’

A. Ali and M. Tariq ( J. Chem. Res., 30, 2006, 261) have reported the prediction of internal pressure of binary liquid mixtures using Flory's statistical theory. It is now shown that the Ali–Tariq approach to calculate thermal expansion coefficient αp and isothermal compressibility κT for both organic liquids and liquid mixtures, is totally wrong, misleading and introduces errors in thermodynamic data. It should also be emphasised that once the correct expressions for calculating Flory's interaction parameter X12 are known, one should use only those expressions to derive X12 in the prediction of any thermodynamic property of liquid mixtures.