Abstract: Static dielectric constants of acetonitrile/water mixtures in the whole composition range and within the temperature range from (15 to 60) °C have been measured. The values were fitted to a unique equation as a simultaneous function of temperature and acetonitrile composition. Densities of these mixtures at temperatures from (5 to 55) °C and different compositions have been collected from the literature. The complete data set was critically analyzed, the outliers were excluded, and the remaining values were also fitted to a unique equation as a function of temperature and acetonitrile composition. From the dielectric constants and densities, the activity coefficients of ions can be calculated by means of the Debye−Huckel approach, allowing the study of the ionic equilibria and determination of reference pH values or acidity constants in any acetonitrile/water mixture at any temperature within the studied range.

Abstract: The solubilities of C2H4 and CO2 and the interactions of polar and nonpolar solutes with the novel ionic liquids (ILs) 1-butyronitrile-3-methylimidazolium bis(trifluoromethylsulfonyl) imidate (CpMIm[NTf2]), 1-butyronitrile-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imidate (CpMMIm[NTf2]), 1-butyronitrile-3-methylimidazolium dicyanamide (CpMIm[N(CN)2]), 1-butyronitrile-2,3-dimethylimidazolium dicyanamide (CpMMIm[N(CN)2]), 1-butyl-3-methylimidazolium palmitate (BMIm[n-C16H33COO]), and 1-butyl-3-methylimidazolium stearate (BMIm[n-C18H35COO]) were studied by gas chromatography at infinite dilution at T = (303.15, 313.15, 323.15, and 333.15) K. Henry's law constant kH of C2H4 and CO2 gas, infinite dilution activity coefficient γ∞, molar enthalpies of solution ΔsolH∞, and partial molar excess enthalpies of solution ΔHE∞ and of Gibbs energies ΔGE∞ were determined for polar and nonpolar solutes in these novel ILs. Compared with the 1,3-dialkylimidazolium ILs, cyano functional group substitution on the a...

Abstract: The activity coefficients at infinite dilution, for 29 solutes, alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols and water in the ionic liquid 1-ethyl-3-methylimidazolium trifluoroacetate ([EMIM][TFA]), were determined by gas−liquid chromatography at temperatures from 298.15−368.15 K. The partial molar excess enthalpies at infinite dilution Δ values were calculated from the experimental values obtained over the temperature range. The selectivities for the hexane/benzene and cyclohexane/benzene separation were calculated from and compared to the literature values for other ionic liquids, NMP and sulfolane.

Abstract: Four equations of state have been implemented and evaluated for multicomponent electrolyte solutions at 298.15 K and 1 bar. The equations contain terms accounting for short-range and long-range interactions in electrolyte solutions. Short range interactions are described by one of the three equations of state, Peng-Robinson, Soave-Redlich-Kwong, or Cubic-Plus-Association (CPA). Long-range interactions are described by either the simplified mean spherical approximation (MSA) solution of the Ornstein–Zernicke equation or the simplified Debye–Huckel term. An optional Born term is added to these electrostatic terms. The resulting electrolyte equations of state were tested by determining the optimal model parameters for the multicomponent test system consisting of H2O, Na+, H+, Ca2+, Cl−, OH−, SO42−. To describe the thermodynamics of this multicomponent system, ion specific parameters were determined. The parameters in the equations of state were fitted to experimental data consisting of apparent molar volumes, osmotic coefficients, mean ionic activity coefficients, and solid–liquid equilibrium data. The results of the parameter fitting are presented. The ability of the equations of state to reproduce the experimental data is demonstrated. The performance of the equations of state for multi component systems is compared and analyzed in view of the various short-range and long-range terms employed. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Abstract: The behavior of mixed nonionic/nonionic surfactant solutions, that is, p-(1,1,3,3-tetramethylbutyl)phenoxy poly(ethylene glycol)s Triton X-100 (TX100) and Triton X-165 (TX165) have been studied by surface tension and density measurements. The obtained results of the surface tension measurements were compared with those calculated from the relations derived by Joos, Miller, and co-workers. From the comparison, it appeared that by using these two approaches the adsorption behavior of TX100 and TX165 mixtures at different mole fractions can be predicted. The negative deviation from the linear relationship between the surface tension and composition of TX100 and TX165 mixtures in the concentration range corresponding to that of the saturated monolayer at the interface, the values of the parameters of molecular interaction, the activity coefficients, as well as the excess Gibbs energy of mixed monolayer formation calculated on the basis of Rosen and Motomura approaches proved that there is synergism in the red...

Abstract: The activity coefficients at infinite dilution, γi∞, for 16 organic solutes, alkanes, alkenes, and alkyl benzenes in the ionic liquid 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]), have been measured by the gas–liquid chromatographic method. The measurements were carried out in the temperature range of (313.15 to 363.15) K. The partial molar excess enthalpies at infinite dilution, HiE,∞, of the solutes in [BMIM][DBP] were also derived from the temperature dependence of the γi∞ values.

Abstract: The analysis by infrared spectroscopy of aqueous solutions of the binary inorganic salts NaI and NaCl and the ternary salts CaCl2 and BaCl2 at concentrations from 1000to2mM was carried out to complement a previous study done at higher concentrations on nine binary salts (alkali halides) and one ternary salt (MgCl2) [J.-J. Max and C. Chapados, J. Chem. Phys. 115, 2664 (2001)]. These salts are completely ionized in aqueous solutions, forming monoatomic species that do not absorb IR but that perturb the surrounding water, modifying its spectrum. The factor analysis of the spectra revealed that all these salt solutions were composed of two water types: pure water and salt solvated water. The authors obtained pure salt solvated water spectra for all the salts using an extrapolation technique. The water types obtained are constant for the binary and ternary salts down to 2mM. For the binary salts, we determine that 5.0 and 4.0 water molecules are solvated to the Na+–Cl− and Na+–I− ion pairs, respectively. These numbers are the same as that obtained at higher concentrations. For the new ternary salts, we find that 6.0 and 8.0 water molecules are solvated to Ca++–(Cl−)2 and Ba++–(Cl−)2 ion pairs, respectively. These numbers are higher than the four water molecules solvated to Mg++–(Cl−)2 ion pairs determined previously, but show a progression that follows their atomic numbers. These results constitute new experimental results on “simple” systems whose molecular organization is still a matter of debate. The IR method that probes the system at the molecular level is a method different than the macroscopic ones that give the activity coefficients. The IR gives direct observation at the molecular level of the strong ion-water interactions that are often neglected and its water structure not considered in macroscopic methods. The present results and their analysis together with those obtained by other methods will facilitate the determination of the organization of these aqueous systems.

Abstract: A modified Dvorak & Boublik & recirculation still was used for the determination of isothermal vapour–liquid equilibrium data for the binary system ethanol–n-octane at four temperatures. Liquid activity coefficients, γ, were evaluated, and log γ values were correlated by a three-constant Redlich–Kister equation. Binary azeotrope exists at all four temperatures and the mole fraction of ethanol in the azeotrope increases with increasing temperature.

Abstract: Liquid−liquid equilibrium data have been determined experimentally for {1-methyl-3-octylimidazolium tetrafluoroborate + thiophene + hexane} and {1-methyl-3-octylimidazolium tetrafluoroborate + thiophene + cyclohexane} ternary systems at 298.15 K. The compositions of the ends of the tie-lines were obtained by gas chromatographic analysis of phases at equilibrium. Data have been adequately correlated using the nonrandom two-liquid (NRTL) activity coefficient model despite this being an equation intended for nonelectrolyte solutions.

Abstract: The solubilities of benzoic acid and phthalic acid in acetic acid + water solvent mixtures are determined by a static method. The experimental temperature ranges from (298.3 to 367.9) K, and the mass fraction of acetic acid in the solvent mixtures ranges from 0.8 to 1.0. The experimental results show that, within the temperature range of the measurements, the solubility of benzoic acid and phthalic acid in all the mixtures shows an increasing trend as the temperature increases. The solubility of benzoic acid decreases with increasing mass fraction of water. For the solubility of phthalic acid in acetic acid + water within the solvent composition range of the measurements, below 325.2 K, the higher the mass fraction of water, the less the solubility. However, above 325.2 K the higher the mass fraction of water, the greater the solubility. A simple explanation was given for this “maximum-solubility effect”. The experimental data was correlated by the Non-Random Two Liquids (NRTL) activity coefficient model,...

Abstract: Solubility data in water of ethane, propane, isobutane, n-butane, n-pentane, and n-hexane have been obtained as a function of temperature in vapor−liquid−liquid equilibrium (VLLE) conditions. The minimum temperature of experiments is 288 K, while the maximum temperature, for each system, is lower than the critical temperature of the corresponding hydrocarbon. New solubility vs temperature correlations are given herein for the studied hydrocarbons in water. Henry's law and activity coefficients at infinite dilution are deduced from the experimental solubility data. Good agreement is found with available literature data.

Abstract: From vapor pressure osmometry data, the activity of water, osmotic coefficients and mean ionic activity coefficients of glycine (m=0.006−3.2 mol⋅kg−1), L-histidine (m=0.005−0.23 mol⋅kg−1), L-histidine monohydrochloride (m=0.008−0.63 mol⋅kg−1), glutamic acid (m=0.004−0.05 mol⋅kg−1), sodium L-glutamate (m=0.007−0.6 mol⋅kg−1), and calcium L-glutamate (m=0.008−0.6 mol⋅kg−1) have been obtained in aqueous solutions at 298.15 and 310.15 K. The Pitzer equations and the mean spherical approximation (MSA) are used for theoretical modeling. The results are supplied as reference thermodynamic material for the characterization of more complex molecules such as proteins.

Abstract: Modeling atmospheric aerosol and cloud microphysics is rather complex, even if chemical and thermodynamical equilibrium is assumed. We show, however, that the thermodynamics can be considerably simplified by reformulating equilibrium to include water, and transform laboratory-based concepts to atmospheric conditions. We generalize the thermodynamic principles that explain hydration and osmosis ? merely based on solute solubilities. In chemical and thermodynamical equilibrium the relative humidity (RH) determines the saturation molality, including solute and solvent activities (and activity coefficients), since the water content is fixed by RH for a given aerosol concentration and type. As a consequence, gas/liquid/solid aerosol equilibrium partitioning can be solved analytically and non-iteratively. Our new concept enables an efficient and accurate calculation of the aerosol water mass and to directly link the aerosol hygroscopic growth to haze and cloud formation. We apply our new concept in the 3rd Equilibrium Simplified Aerosol Model (EQSAM3). Its input is limited to the species' solubilities from which a newly introduced stoichiometric coefficient for water is derived. Analogously, we introduce effective stochiometric coefficients for the solutes to account for complete or incomplete dissociation. We show that these coefficients can be assumed constant over the entire activity range and calculated for various inorganic, organic and non-electrolyte compounds, including alcohols, sugars and dissolved gases. EQSAM3 calculates the aerosol composition and gas/liquid/solid partitioning of mixed inorganic/organic multicomponent solutions and the associated water uptake for almost 100 major compounds. It explicitly accounts for particle hygroscopic growth by computing aerosol properties such as single solute molalities, molal based activities, including activity coefficients for volatile compounds, and deliquescence relative humidities of mixed solutes. Various applications and a model inter-comparison indicate that a) the application is not limited to dilute binary solutions, b) sensitive aerosol properties such as the pH of binary and mixed inorganic/organic salt solutions up to saturation can be computed accurately, and c) aerosol associated water is important for atmospheric chemistry, visibility, weather and climate.

Abstract: An ebulliometer has been designed for vapor−liquid equilibrium measurement of systems containing an ionic liquid (IL). The new design allows vapor phase sampling and analysis, while the liquid composition is calculated on the basis of synthetic quantities and with regard to vapor phase composition, quantity of vapor material, and vapor-to-liquid circulation ratio. T, x, y data are reported for the system water + 2-propanol + 1-butyl-3-methylimidazolium tetrafluoroborate at 100 kPa and ionic liquid mass fractions of 0.300, 0.500, and 0.700. The quasi-binary system water + 2-propanol presents a temperature minimum when IL mass fraction is kept constant at these three concentrations. Addition of the IL with mass fraction of 0.500 and 0.700 breaks the azeotrope. Activity coefficients are calculated from the experimental data for the volatile components in the IL-containing mixture. The activity coefficients are directly related to the relative volatility of the quasi-binary mixture and show rather complicated...

Abstract: The total pressure and the compositions of the vapour and liquid phases of the methanol–benzene system have been determined under equilibrium conditions at 100°, 120°, 140°, 160°, 180°, 200° and 220° for ten levels of concentration. The corresponding activity coefficients of methanol and benzene are reported; their values indicate that the equilibrium data are thermodynamically consistent. An azeotrope is found at all temperatures, its methanol content increasing as the temperature is increased. The relationship log Paz = 6·5098—(1,766/T) expresses the interdependence of the azeotrope vapour pressure Paz(lb/in2 abs.) and temperature T(°K). Estimates of integral heat of mixing (HE) and entropy change due to mixing (SE) as functions of liquid composition (xmeth) have been made from the excess free energy of mixing GE,(T) xmeth functions. Both HE and SE at a given x are positive increasing functions of temperature. These phenomena are discussed in terms of the dissociation of methanol ‘polymer’ and the formation of benzene–methanol ‘complexes’.

Abstract: The modification and extension of a three-characteristic-parameter correlation model for calculating the thermodynamic properties including osmotic and mean activity coefficients of aqueous electrolytes at 298.15 K have been presented in this paper. The model can be reduced with two parameters: b, the approaching parameter, and S, the solvation parameter. Although the model adequately describes the thermodynamics with these two parameters, the third parameter, n, which is related to the distance between an ion and a solvent molecule, also can be regarded as an adjustable parameter. The two sets of parameters for 283 single salts in aqueous solutions up to saturation have been obtained from the regression of experimental values. Mean activity or osmotic coefficients of RbNO2, MgCl2, Sm(ClO4)3, and ZnSO4, with these two sets of parameters, have been compared with the smoothed experimental data, which show good agreement. When the model with three parameters is employed, it gives a more accurate result, esp...

Abstract: Ion-based SAFT2 is used to represent the properties of aqueous single-salt solutions in the temperature, pressure, and concentration ranges of 298.15−473.15 K, 1.013−1000 bar, and 0−6 mol/kgH2O in ionic strength, respectively. The short-range interaction between cation and anion is needed to capture the effect of pressure on the properties of electrolyte solutions. A new set of parameters at 298.15 K for five cations (Li+, Na+, K+, Ca2+, Mg2+) and seven anions (Cl-, Br-, I-, NO3-, HCO3-, SO42-, CO32-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 26 aqueous single-salt solutions. An additional set of ion-specific coefficients used in the temperature-dependent parameter expressions for five cations (Li+, Na+, K+, Ca2+, Mg2+) and five anions (Cl-, Br-, HCO3-, SO42-, CO32-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 15 aqueous single-salt solutions at low pressures and temperatures up to...

Abstract: Activity coefficients at infinite dilution of 17 polar solutes included linear and branched C1 to C5 alcohols, chlorinated methane, acetone, acetonitrile, ethyl acetate, 1,4-dioxane, and cyclohexanone in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate were determined by gas chromatography using the ionic liquid as the stationary phase. The measurements were carried out at temperatures between (303.15 and 343.15) K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution of the organic solutes in the ionic liquid have been derived.

Abstract: The simple three-parameter Pitzer and extended Huckel equations were used for calculation of activity coefficients of aqueous hydrochloric acid at various temperatures from 0 to 50 °C up to a molality of 5.0 mol·kg−1. A more complex Huckel equation was also used at these temperatures up to a HCl molality of 16 mol·kg−1. The literature data measured by Harned and Ehlers J. Am. Chem. Soc. 54, 1350–1357 (1932) and 55, 2179–2193 (1933) and by Akerlof and Teare [J. Am. Chem. Soc. 59, 1855–1868 (1937)] on galvanic cells without a liquid junction were used in the parameter estimations for these equations. The latter data consist of sets of measurements in the temperature range 0 to 50 °C at intervals of 10 °C, and data at these temperatures were used in all of these estimations. It was observed that the estimated parameters follow very simple equations with respect to temperature. They are either constant or depend linearly on the temperature. The values for the activity coefficient parameters calculated by using these simple equations are recommended here. The suggested new parameter values were tested with all reliable cell potential and vapor pressure data available in literature for concentrated HCl solutions. New Harned cell data at 5, 15, 25, 35, and 45 °C up to a molality of 6.5 mol·kg−1 are reported and were also used in the tests. The activity coefficients obtained from the new equations were compared to those calculated by using the Pitzer equations of Holmes et al. [J. Chem. Thermodyn. 19, 863–890 (1987)] and of Saluja et al. [Can. J. Chem. 64, 1328–1335 (1986)] at various temperatures, and by using the extended Huckel equation of Hamer and Wu [J. Phys. Chem. Ref. Data 1, 1047–1099 (1972)] at 25 °C.

Abstract: Ionic liquids are neoteric, environmentally friendly solvents (since they do not produce emissions) composed of large organic cations and relatively small inorganic anions. They have favorable physical properties, such as negligible volatility and wide range of liquid existence. Moreover, many different cations and anions can be used to synthesize ionic liquid, so the properties can be designed by the use of selected combinations of anions and cations. (Liquid + liquid) equilibrium (LLE) data for systems including ionic liquids, although essential for the design and operation of separation processes, are still scarce. However, some recent studies have presented ternary LLE data involving several ionic liquids and such organic compounds as alkanes, alkenes, alkanols, water, ethers and aromatics. In this work, LLE data for 24 ternary systems including ionic liquids from the literature are correlated by using the NRTL model for the activity coefficient. The results are very satisfactory, with rms deviations of about 1.4%.