Densities, isobaric thermal expansivities, and excess enthalpies were determined for the binary systems formed by ionic liquids with a common anion, 1-hexyl-3-methylimidazolium tetrafluoroborate + 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium tetrafluoroborate + 1-butyl-3-methylimidazolium tetrafluoroborate, and by those with a common cation, 1-butyl-3-methylimidazolium tetrafluoroborate + 1-butyl-3-methylimidazolium methylsulfate and 1-butyl-3-methylimidazolium tetrafluoroborate + 1-butyl-3-methylimidazolium hexafluorophosphate. Volumetric properties were obtained by means of a vibrating tube densimeter, whereas Calvet microcalorimetry was used to determine the excess enthalpies. Due to the high viscosity of the samples, nonstandard experimental techniques had to be used to obtain the results. The experimental data are interpreted on the basis of the chemical structure of the ionic liquids.

Excess Magnitudes for Ionic Liquid Binary Mixtures with a Common Ion

An isothermal displacement calorimeter for endothermic enthalpies of mixing

Transport properties of liquid methanol and ethanol are predicted by molecular dynamics simulation. The molecular models for the alcohols are rigid, nonpolarizable, and of united-atom type. They were developed in preceding work using experimental vapor-liquid equilibrium data only. Self- and Maxwell-Stefan diffusion coefficients as well as the shear viscosity of methanol, ethanol, and their binary mixture are determined using equilibrium molecular dynamics and the Green-Kubo formalism. Nonequilibrium molecular dynamics is used for predicting the thermal conductivity of the two pure substances. The transport properties of the fluids are calculated over a wide temperature range at ambient pressure and compared with experimental and simulation data from the literature. Overall, a very good agreement with the experiment is found. For instance, the self-diffusion coefficient and the shear viscosity are predicted with average deviations of less than 8% for the pure alcohols and 12% for the mixture. The predicted thermal conductivity agrees on average within 5% with the experimental data. Additionally, some velocity and shear viscosity autocorrelation functions are presented and discussed. Radial distribution functions for ethanol are also presented. The predicted excess volume, excess enthalpy, and the vapor-liquid equilibrium of the binary mixture methanol + ethanol are assessed and agree well with experimental data.

Prediction of transport properties by molecular simulation: methanol and ethanol and their mixture.

Topological aspects of the effect of temperature and pressure on the thermodynamics of binary mixtures of non-electrolytes

Complex permittivity was measured in the frequency range from 10 MHz to 20 GHz at 25 °C for water mixtures of 22 aliphatic alcohols. The molecular structures of these alcohols systematically changed with the number of carbon atoms and hydroxyl groups, and their positions in the molecules. The asymmetric shape of the frequency dependence of the dielectric loss for the primary relaxation process was observed for each mixture. The broadness of the asymmetric dielectric loss depends on the water content, and the broadest dielectric loss was observed in the water mole fraction range of 0.65 < xw < 0.85. There is a strong correlation between the broadness of dielectric loss and the number of carbon atoms in the alcohol molecule. Deviations of observed relaxation times from those estimated for ideal mixtures depend on the number of carbon atoms except for the mixtures of water and alcohols with large alkyl groups, which form a micelle-like structure. These experimental results are interpreted on the basis of a m...

Dielectric Relaxation Time and Relaxation Time Distribution of Alcohol−Water Mixtures

The heats of mixing of the 11 binary n-alcohol systems containing either butanol or octanol and formed from the set methanol, ethanol, propanol, butanol, hexanol, octanol, and decanol were measured in a continuous dilution calorimeter at 25 °C. The applicability of Bronsted's principle of congruence to the data was investigated.

A. E. Pope

Papers

Molar excess enthalpies of binary n-alcohol systems at 25 °C

Heats of mixing of normal alcohols at 25.deg.