Abstract: Activity coefficients at infinite dilution of alkanes, alkenes, and alkylbenzenes as well as of the linear and branched C1−C6 alcohols, esters, and aldehydes in the ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide have been determined by gas chromatography using the ionic liquids as stationary phase. The measurements were carried out at different temperatures between 301 K and 396 K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution of the solutes in the ionic liquids have been derived.

Abstract: Activity coefficients at infinite dilution of 31 organic compounds in three room-temperature ionic liquids (RTILs) were determined using inverse gas chromatography The measurements were carried out at different temperatures between 31315 and 33315 K The regular solution theory was used to estimate the solubility parameters of each RTIL Such a theory was also used to predict the CO2 solubility in a given RTIL and to estimate the upper critical solution temperature of a binary system containing 1-butanol and 1-butyl-3-methylimidazolium hexafluorophosphate The accuracy of the results obtained indicates that the regular solution theory is a good tool to predict the phase behavior of mixtures containing RTILs

Abstract: The activity coefficients at infinite dilution, , for both polar and nonpolar solutes in the ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) imidate have been determined by gas−liquid chromatography at the temperatures T = 303.15 K and T = 318.15 K. The results have been used to predict the solvent potential for the hexane−benzene separation using the calculated selectivity values. The results are compared to the for similar systems found in the literature in an attempt to understand the effect that the nature of the cation has on the solute−solvent interactions. The partial molar excess enthalpies at infinite dilution values, Δ , were calculated from the experimental values obtained at the two temperatures.

Abstract: Vapor−liquid equilibria of binary mixtures containing high-boiling solutes methoxy-benzene, (hydroxymethyl)-benzene, 1,2-ethanediol, and 1,4-butanediol and ionic liquid [EMIM][NTf2] were studied by using the transpiration method. VLE measurements were carried out over the whole concentration range at different temperatures between 298 K and 363 K. Activity coefficients γi of these solvents in the ionic liquid have been determined from these data and are described formally by using the NRTL equation. In addition, vapor pressures of pure solutes methoxy-benzene, (hydroxymethyl)-benzene, 1,2-ethanediol, and 1,4-butanediol have been measured as a function of temperature, and their enthalpies of vaporization have been obtained.

Abstract: Statistical Associating Fluid Theory coupled with Restricted Primitive Model (SAFT1-RPM) represents the mean ionic activity coefficient, density, osmotic coefficient, and vapor pressure of several ...

Abstract: The dissociation reaction of the bisulfate ion, HSO4- ⇌ SO42- + H+, is investigated in aqueous H2SO4 solutions with concentrations of 0.54−15.23 mol kg-1 in the temperature range of 180−326 K using Raman spectroscopy. All investigated H2SO4 solutions show a continuous increase in the degree of dissociation of HSO4- with decreasing temperature, in contrast to predictions from thermodynamic models of aqueous H2SO4 solutions. A Pitzer ion interaction model is used to derive a thermodynamically consistent formulation of the thermodynamic dissociation constant of the bisulfate ion, KII(T), that is in agreement with the experimental data. The new formulation of KII(T) is valid from 180 to 473 K. All ion interaction parameters and the corresponding parametrizations of the Pitzer ion interaction model are presented. Calculations with this model reveal significant differences in ion activity coefficients, water activities, water vapor pressure, and HCl solubilities, when compared to existing thermodynamic models o...

Abstract: In the present paper a procedure to calculate the properties of proteins in aqueous mixed solvents, particularly the excesses of the constituents of the mixed solvent near the protein molecule and the preferential binding parameters, is suggested. Expressions for the Kirkwood-Buff integrals in ternary mixtures and for the preferential binding parameter were derived and used to calculate various properties of infinitely dilute proteins in aqueous mixed solvents. The derived expressions and experimental information regarding the partial molar volumes and the preferential binding parameters were used to calculate the excesses (deficits) of water and cosolvent (in comparison with the bulk concentrations of protein-free mixed solvent) in the vicinity of ribonuclease A, ribonuclease T1, and lysozyme molecules. The calculations showed that water was in excess in the vicinity of ribonuclease A for water/glycerol and water/trehalose mixtures, and the cosolvent urea was in excess in the vicinity of ribonuclease T1 and lysozyme. The derivative of the activity coefficient of the protein with respect to the mole fraction of water was also calculated. This derivative was negative for the water/glycerol and water/trehalose mixed solvents and positive for the water/urea mixture. The mixture of lysozyme in the water/urea solvent is of particular interest, because the lysozyme at pH 7.0 is in its native state up to 9.3M urea, while at pH 2.0 it is denaturated between 2.5 and 5M and higher concentrations of urea. Our results demonstrated a striking similarity in the hydration of lysozyme at both pHs. It is worthwhile to note that the excesses of urea were only weakly composition dependent on both cases.

Abstract: Activity coefficients at infinite dilution of alkanes, alkenes, and alkylbenzenes as well as of the linear and branched C1−C6 alcohols, esters, and aldehydes in the ionic liquid 1-methyl-3-octyl-imidazolium tetrafluoroborate were determined by gas chromatography using the ionic liquid as the stationary phase. The measurements were carried out at different temperatures between 302 K and 396 K. Data points (204) have been obtained for 51 solutes. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution of the solutes in the ionic liquid have been derived.

Abstract: The activity coefficients at infinite dilution, , for hydrocarbons and methanol solutes in the ionic liquid 1-butyl-3-methylimidazolium octyl sulfate, [BMIM][OcOSO3], have been determined by gas−liquid chromatography at temperatures of 298.15 K, 313.15 K, and 328.15 K. This work is part of our research focus on activity coefficients at infinite dilution, , in ionic liquids. The selectivity values have been calculated at T = 298.15 K, and the results indicate that the ionic liquid [BMIM][OcOSO3] should not be considered to be a solvent for the separation of alkanes and aromatics. The partial molar excess enthalpy values at infinite dilution have also been determined at temperature 298.15 K and have been discussed in terms of intermolecular interactions and packing effects. The results have been discussed in terms of measurements of for other ionic liquids taken from the recent literature.

Abstract: A model for the Gibbs excess energy of mixed-solvent (chemical-reacting) electrolyte systems is presented. The activities of solvent and solute species are calculated by applying a new extension of Pitzer's equation for the excess Gibbs energy of aqueous electrolyte solutions, which allows for solvent mixtures. The capability of the new model to simultaneously describe such properties as, e.g., the mean ionic activity coefficient and the solubility of a salt (for example, sodium chloride) in a binary solvent mixture (for example, methanol + water), as well as the influence of that salt on the vapor−liquid equilibrium of that binary solvent mixture, is tested. The new model gives an explanation for the “salting-out” and “salting-in” effects resulting, e.g., from the addition of a salt to a liquid mixture of volatile solvents. The new model can also be applied to describe the gas solubility in mixed solvents in the presence of electrolytes. The capability of the new model to describe the solubility of a sin...

Abstract: A thermodynamic analysis is presented for electrically charged mixed micelles in water on the basis of the Gibbs−Duhem relation proposed by Hall in combination with the information on the degree of counterion binding. The proposed analyses are shown to work well for both ionic/nonionic mixed micelles and those consisting of ionic surfactants of like charges. Conclusions for ionic/nonionic mixed micelles are as follows. (1) The contribution from counterions is significant. (2) In media of low ionic strengths, the counterion concentration varies with the micellar mole fraction of the ionic species x. The dependency of the activity coefficients and the excess free energy on x is significantly influenced by this effect, but it can be corrected to a large extent in terms of the Corrin−Harkins relation. (3) The regular solution theory (RST) is not always valid even when the excess free energy is described well with the RST expression unless the observed range of the micelle composition is wide enough. (4) The R...

Abstract: The nonrandom two-liquid segment activity coefficient model of Chen and Song (Ind. Eng. Chem. Res. 2004, 43, 8354) has shown to be a simple and practical tool for chemists and engineers to correlate and estimate solubilities of organic nonelectrolytes in support of chemical and pharmaceutical process design. In this paper, the model is extended for the computation of ionic activity coefficients and solubilities of electrolytes, organic and inorganic, in common solvents and solvent mixtures. In addition to the three types of molecular parameters defined for organic nonelectrolytes, i.e., hydrophobicity X, polarity Y, and hydrophilicity Z, an electrolyte parameter, E, is introduced to characterize both local and long-range ion−ion and ion−molecule interactions attributed to ionized segments of electrolytes. Successful representations of mean ionic activity coefficients and solubilities of electrolytes, inorganic and organic, in aqueous and nonaqueous solvents are presented.

Abstract: The activity of alkali metal oxides can be controlled in one-atmosphere wire-loop experiments at high temperature by suspending a crucible containing alkali silicate melt beneath the samples. The method has been applied to measuring the activity coefficient of NaO0.5 in a series of CMAS-NaO0.5 melts relative to that in the anorthite-diopside eutectic composition at 1400 °C, using a reservoir of NaO0.5-SiO2 melt. The results show that this relative activity coefficient decreases strongly with SiO2, increases with CaO and MgO, but is insensitive to AlO0.5. This latter behavior is inconsistent with “quasi-crystalline” models of melt thermodynamics that hypothesize Na-Al species.

Abstract: The electrode reaction of Ce(III)/Ce couple in the eutectic LiCl - KCl, on a Bi liquid electrode, was investigated in the temperature range of 673 - 823 K. Cyclic voltammetry, using a Bi pool electrode, suggest a quasi - reversible behaviour of the system, and the values of the kinetic parameters, k0 and α, as well as the reversible half wave potential, Er 1/2, have been obtained. The differences between the equilibrium potential adopted by a Ce electrode and the Er1/2 observed with the same Ce(III) solution at the liquid electrode, were consistent with the activity coefficients of Ce in the liquid Bi phase taken from the literature. Because of the ease of application of cyclic voltammetry, it was suggested this to be used as a general method to obtain approximate values of the excess Gibbs energy change of Ce in liquid metal, and hence the partial molar enthalpy of mixing and the partial molar excess entropy. Electromotive force, emf, measurements for various intermetallic compounds in two - phase coexisting states were carried out using a Bi coated tungsten electrode. The activities and relative partial molar Gibbs energies of Ce were obtained for CeBi2 and CeBi. The relative partial molar entropies and enthalpies of Ce as well as the standard Gibbs energies of formation for the Ce - Bi intermetallic compounds were calculated.