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Ionic liquids have attracted much attention in past decade for their unique properties. The density is an important property in industrial application, however the density data are relatively scarce compared with the great number of ILs. The quantitative structure property relationship (QSPR) and group contribution method (GCM) have been used for predicting ILs density. However, the accuracy of QSPR is not as good as that of GCM. In this work, a desirable QSPR model was developed to estimate ILs density. The general topological indexes (TIs) proposed by our research group were used to develop the QSPR model, which was on the basis of 5948 experimental data points for 188 ILs. The collected data are in the range of temperature (253.15–473.15) K and pressure (0.1–250) MPa. The correlation coefficient (R2) and the overall average absolute deviation are 0.998 and 0.422 %, respectively.

The isobaric vapor–liquid equilibrium (VLE) data were measured for the binary system (ethane-1,2-diol + butan-1,2-diol) at (20, 30, and 40) kPa using a modified dynamic recirculating still. The thermodynamic consistency of the experimental data was confirmed using the Herington and van Ness semiempirical method. The Wilson and universal quasichemical (UNIQUAC) models were used to correlate the activity coefficients with the liquid-phase composition. The average absolute deviation of the bubble-point temperature and vapor molar fraction for all of the systems obtained from the Wilson and UNIQUAC models are less than 0.18 K and 0.0011, respectively. Furthermore, the binary system (ethane-1,2-diol + butan-1,2-diol) exhibited azeotropic behavior. In addition, the data were calculated using the UNIFAC (Do) model (modified UNIFAC model) in which ethane-1,2-diol was treated as two groups (−CH2OH), and butan-1,2-diol was split to four groups (−CH2OH, −CHOH, −CH2, and −CH3). The new group-interaction parameter for...