Partial Molar Excess Gibbs Energy Research Articles

Activity Coefficients at Infinite Dilution and Physicochemical Properties for Organic Solutes and Water in the Ionic Liquid 1-Ethyl-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate.

New data of activity coefficients at infinite dilution, γ 13∞, for 65 different solutes including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, aldehydes, esters and water in the ionic liquid 1-ethyl-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate, were determined using inverse gas chromatography within the temperature range from 318.15 to 368.15 K. This is a continuation of our study of ionic liquids based on this anion. The results are compared with the other trifluorotris(perfluoroethyl)phosphate ionic liquids. The γ 13∞ values were used to calculate thermodynamic functions such as partial molar excess Gibbs energies Delta G_{1}^{{{text{E,}}infty }} , enthalpies Delta H_{1}^{{{text{E,}}infty }} and entropies Delta S_{1}^{{{text{E,}}infty }} as well as gas–liquid partition coefficients of the solutes, K L. These values were used to determine the linear free energy relationship (LFER) system constants as a function of temperature. The selectivities at infinite dilution needed for some extraction problems were calculated and compared with literature data of ionic liquids based on the trifluorotris(perfluoroethyl)phosphate anion and the 1-ethyl-3-methylimidazolium cation. Additionally, the density and viscosity of the investigated ionic liquid at temperatures from 298.15 to 348.15 K were measured.Electronic supplementary materialThe online version of this article (doi:10.1007/s10953-014-0274-0) contains supplementary material, which is available to authorized users.

Measurements of activity coefficients at infinite dilution in vegetable oils and capric acid using the dilutor technique

This paper reports experimental activity coefficients at infinite dilution, γi∞, for methanol, ethanol and n-hexane in three refined vegetable oils (soybean, sunflower, and rapeseed oils) measured using the dilutor technique (inert gas stripping method). The measurements were carried out in the temperature range between 313.15 and 353.15K. Furthermore, activity coefficients at infinite dilution for various solutes (acetone, methanol, ethanol, n-hexane, cyclohexane and toluene) were measured in capric (decanoic) acid using the same technique in the temperature range from 313.13 to 353.30K. The new data obtained for capric acid and soybean oil were compared with already published experimental data. Additionally, densities of the investigated vegetable oils were measured in the temperature range from 293.15 to 353.15K. Using the experimental γi∞ values obtained over the temperature range, the partial molar excess Gibbs energy (ΔGiE,∞), enthalpy (ΔHiE,∞) and entropy (ΔSiE,∞) at infinite dilution were determined. The relative error for the γi∞ measurements carried out using the dilutor technique is approximately ±2.5%. The measured γi∞ data in the investigated refined vegetable oils were also compared with the results of the group contribution methods original UNIFAC and modified UNIFAC (Dortmund) and an extension of the latter method to triacylglycerols was proposed.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate

This work presents new data of activity coefficients at infinite dilution, γ∞ of different organic solutes and water in the 1-(2-hydroxyethyl)-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate, [C2OHmim][FAP] ionic liquid. Values of γ∞ were determined for 65 organic solutes, including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, 1-nitropropane, aldehydes, acetonitrile and water by inverse gas chromatography within the temperature range from (318.15 to 368.15)K. The basic thermodynamic functions, such as partial molar excess Gibbs energies, ΔG1E,∞, enthalpies, ΔH1E,∞ and entropies, ΔS1E,∞ at infinite dilution were calculated from the experimental γ∞ values obtained over the temperature range. Additionally the gas–liquid partition coefficients, KL were determined. Experimental values of gas–liquid partition coefficients were used to determine the coefficients in the Abraham solvation parameter model (LFER). Results are compared to previously investigated ionic liquids with the same [C2OHmim]+ cation and [FAP]− anion. The selectivity and capacity at infinite dilution for alkanes/thiophene extraction problems were calculated from experimental γ∞ values to verify the possibility of investigated ionic liquid as an entrainer in liquid–liquid extraction.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2-methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate

This work presents new data of activity coefficients at infinite dilution, γ∞ of different organic solutes and water in the 1-(2-methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate ionic liquid. Values of γ∞ were determined for 62 solutes, including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, 1-nitropropane, butanal, acetonitrile and water by inverse gas chromatography over the temperature range from (318.15 to 368.15)K. The basic thermodynamic functions, namely partial molar excess Gibbs energies, ΔG1E,∞, enthalpies, ΔH1E,∞ and entropies, ΔS1E,∞ at infinite dilution were calculated from the experimental γ∞ values obtained over the temperature range. Additionally the gas–liquid partition coefficients, KL were determined. Experimental values of gas–liquid partition coefficients were used to determine the coefficients in the Abraham solvation parameter model (LFER). Results are compared to previously investigated ionic liquids with the same cations or anions. The selectivities and capacities at infinite dilution for alkanes/thiophene extraction problems were calculated from experimental γ∞ values to verify the possibility of investigated ionic liquid as an entrainer in liquid–liquid extraction.

Thermodynamics and Activity Coefficients at Infinite Dilution Measurements for Organic Solutes and Water in the Ionic Liquid N-Hexyl-3-methylpyridinium Tosylate

The activity coefficients at infinite dilution, γ13(∞), for 44 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, tetrahydrofuran, ethers, and ketones in the ionic liquid (IL) N-hexyl-3-methylpyridinium tosylate (p-toluenesulfonate), [HM3Py][TOS], were determined by gas-liquid chromatography at temperatures from 338.15 to 368.15 K. The densities of [HM3Py][TOS] as a function of temperature have been measured at temperatures higher than the melting temperature and were extrapolated to T = 298.15 K. The gas-liquid partition coefficients, K(L) were calculated for all solutes. The partial molar excess Gibbs energies ΔG1(E,∞), enthalpies ΔH1(E,∞), and entropies ΔS1(E,∞) at infinite dilution were calculated from the experimental γ13(∞) values obtained over the temperature range. The selectivities for different separation problems including n-heptane/benzene, cyclohexane/benzene, and n-heptane/thiophene were calculated from γ13(∞) and compared to literature values for tosylate-based ILs, or hexyl-substituted cations of ILs, or pyridynium-based IL, or N-methyl-2-pyrrolidinone (NMP), and sulfolane.

Physicochemical Properties and Activity Coefficients at Infinite Dilution for Organic Solutes and Water in the Ionic Liquid 1-Decyl-3-methylimidazolium Tetracyanoborate

The activity coefficients at infinite dilution γ(13)(∞) and gas−liquid partition coefficients K(L) for 43 solutes—alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, carboxylic acids, thiophene, ethers, ketones, and water—in the ionic liquid 1-decyl-3-methylimidazolium tetracyanoborate ([dmim][TCB]) were determined by gas−liquid chromatography at temperatures from 318.15 to 378.15 K. The partial molar excess Gibbs energies ΔG(1)(E,∞), enthalpies ΔH(1)(E,∞), and entropies ΔS(1)(E,∞) at infinite dilution were calculated from the experimental γ(13)(∞) values obtained over the temperature range. Additionally, the densities for investigated ionic liquid over the temperature range were determined. The selectivities for the aliphatic/aromatic hydrocarbon separation problem were calculated from γ(13)(∞) and compared to the literature values for N-methyl-2-pyrrolidinone (NMP) and sulfolane. It was found that the investigated [dmim][TCB] ionic liquid shows much higher capacity than NMP and sulfolane and selectivity on the same level as NMP and lower than that for sulfolane for the separation of aliphatic hydrocarbons from aromatic hydrocarbons.

Osmotic coefficients of aqueous solutions of potassium acesulfame, sodium saccharin, and ammonium and tetramethylammonium cyclohexylsulfamates at the freezing point of solutions

The osmotic coefficients of aqueous solutions of potassium acesulfame (0.67 mol kg−1), sodium saccharin (0.75 mol kg−1), and tetramethylammonium (0.55 mol kg−1) and ammonium (0.35 mol kg−1) cyclohexylsulfamates were determined up to the molality indicated in parentheses. The osmotic coefficients were fitted to the Pitzer equation, and the ion interaction parameters α 1, β (0), and β (1) were evaluated. The mean ionic activity coefficients of the solutes were calculated, and the non-ideal behaviour of the systems investigated were characterized by calculation of the excess Gibbs energy of the solution and the respective partial molar functions of solute and solvent. The partial molar excess Gibbs energies of the solutes are negative, as also are the corresponding excess Gibbs energies of their solutions, and the partial molar excess Gibbs energies of the solvent are positive and increase slightly with increasing concentrations of the solutes. The solvation ability of water was calculated from differences between the Gibbs energy of solution of water in the aqueous solutions and that of pure water, and are positive and small for all the solutes investigated, throughout the concentration ranges studied.

Thermodynamic studies on ThGa 2

The enthalpy of formation of ThGa 2 was determined by high temperature gallium solution calorimetry and precipitation calorimetry. The values thus obtained are −(55.1±4.8) and − (69.6±5.6) kJ g atom −1 with reference to α-thorium and solid gallium at 298.15 and 1100 K, respectively. These are the first calorimetric results for the enthalpy of formation of ThGa 2. The Gibbs energy of formation of ThGa 2 with reference to α-thorium and liquid gallium was determined by molten salt galvanic cell measurements to be −75.1+0.024T kJ g atom −1 in the temperature range 682–891 K. The partial molar excess Gibbs energy of thorium in liquid gallium in the saturated solution at 787 K was determined to be − (123.3±4.7) kJ g atom −1 . The partial molar enthalpy of solution of thorium in liquid gallium at infinite dilution at 1095 K was determined to be − (178.6±6.8) kJ g atom −1 and partial molar enthalpy of thorium in liquid gallium in the saturated solution at 787 K to be − (164.2±4.7) kJ g atom −1 .

Henrian ideality of iron in liquid uranium solvent at high temperatures

Equilibrium vapor pressures of iron from its dilute solutions in liquid uranium were measured at high temperatures (2250–2750 K). From the Fe vapor pressure data at known compositions ( x Fe), Henry’s coefficient ( K Fe= p Fe/ x Fe) of the solute was obtained as log K Fe (±0.07) (Pa)=−18975.6(±1098.1)/T+11.15(±0.44) . The behavior of K Fe( T) is shown to be marginally different from that of the equilibrium vapor pressures of pure liquid iron ( p Fe°). The partial molar excess Gibbs energy of iron at infinite dilution derived from the behavior is expressed as Δ E G ̄ Fe ∞=−1588+1.25T ( J mol −1) . The result is discussed in the light of the quasi-regular solution model and compared with data of the system available in the literature.

Activity coefficients and partial molar volumes of boron in platinum-rhodium alloys

Activity coefficients of B in the α phase of Pt and of three PtRh alloys with 3, 6, and 10 wt.% Rh were obtained by equilibration of B 2O 3 with H 2-H 2O mixtures between 750 and 1000 °C and subsequent determination of the B mole fraction x B ⩽ 0.06 by the mass gain of the samples or by photometric analysis. Additions of Rh to Pt have rather large but opposing effects on the partial molar enthalpies and entropies of B, resulting in partial molar excess Gibbs energies within the modest range between −40 and −55 kJ mol −1. The change in the lattice contraction from −13.5 to −3.2 pm/ x B in the α phase of Pt and of Pt-10Rh can be fully described in terms of a substitutional solution model with strictly constant partial molar volumes of 9.09 cm 3 mol −1 and 8.28 cm 3 mol −1 for Pt and Rh respectively and a partial molar volume for B that increases linearly from 8.2 to 8.9 cm 3 mol −1 between pure Pt and Pt-10Rh.

Thermodynamic activity measurements of U-Fe and U-Ga alloys by mass spectrometry

The thermodynamic activities of Fe in the U-Fe system for xFe = 0.05 to 0.90 in the 1440 K to 1850 K temperature range, and of Ga in the U-Ga system for xGa = 0.05 to 0.28 between 1100 and 1670 K are investigated by the multiple Knudsen cell-mass spectrometric method. The integration of the Gibbs-Duhem equation then yields the uranium activity. These systems are found to exhibit negative deviations from the ideal behavior. Polynomial fits of the relative partial molar excess Gibbs energy referred to liquid elements versus composition and temperature are deduced (in J mol−1), ΔGFexs(1−xFe)2=(−187200+92.646T)+(203834−184.437T)(1−xFe)+(−15614+75.289T)(1−xFe)2, ΔGGaxs(1−xGa)2=(−284 769 + 133.390T) + (242 863−110.39OT)(1−xGa), and compared to previous ones. We have measured the Gibbs energies of formation of the following intermetallic compounds: UFe2 (ΔGfo = − 52.8 ± 3.4 kJ mol−1 at 1501 K), U6Fe (ΔGfo = −31 ± 6 kJmol−1at 998 K) and U2Ga3 (ΔGfo = −111.9 ± 3.9 kJmol−1at 1250 K). Our values for UFe2 and U6Fe are in good agreement with previous data. Concerning the U-Ga system, our measurements suggest a large solubility of gallium in uranium.

On the thermodynamics of the Ta-Rh system

Thermodynamic measurements in the Ta-Rh system were made between 1140 and 1280 K by the e.m.f. method using solid galvanic cells with the arrangements Ta 0.083Rh 0.917, TaRh 3.3, Ta 2O 5¦ThO 2-Y 2O 3¦Fe 0.95O, Fe and Ta 0.083Rh 0.917, TaRh 3.3, Ta 2O 5¦ThO 2-Y 2O 3¦Ta 2O 5, Ta x Rh 1− x ( x ⩽ 0.083). For this purpose, the isothermal section of the Ta-Rh-O system was investigated at a temperature of 1273 K. TaRh 3 and Rh(Ta) are in equilibrium with Ta 2O 5− x . The relative partial molar Gibbs energy of tantalum was determined in the Rh(Ta) solid solution range. The relative partial molar excess Gibbs energy of tantalum in Rh(Ta) at infinite dilution is xsΔ G ̄ Ta ∞ = −250 kJ mol −1 at 1200 K. The Gibbs energies of formation of Ta 0.083Rh 0.917 and TaRh 3.3 are fΔG o = −22 kJ mol −1 and fΔG o = −273 + 0.020 T kJ mol −1 respectively, between 1140 and 1280 K.

Thermodynamics of the MoRu system

Thermodynamic measurements in the MoRu system were made between 1150 and 1350 K by the e.m.f. method using solid galvanic cells in the arrangement Re¦Fe,Fe 0.95 O¦Zr(Ca)O 2 ¦MoO 2 ,MoRu¦Re. For this purpose, the isothermal section of the MoRuO system was investigated at 1273 K. The Ru(Mo) solid solution is in equilibrium with MoO 2 − x . The relative partial molar Gibbs energy of molybdenum was determined in the entire MoRu concentration range. The relative partial molar excess Gibbs energy of molybdenum in the h.c.p. Ru(Mo) solid solution at infinite dilution is xs Δ G ̄ Mo ∞ = −43 kJ mol −1 at 1200 K. The minimum of the Gibbs energy of formation was found at x Ru = 0.70; it is f ΔG °( Mo 0.3 Ru 0.7 ) = −8900 −0.6 T J mol −1 between 1150 and 1350 K. The minimum of the enthalpy of formation was found at x Ru = 0.85; it is f ΔH °( Mo 0.15 Ru 0.85 ) = −11 700 J mol −1 .

Activity coefficients and the α-γ transition lines in fe-b alloys

Activity coefficients of B in γ-Fe at 1227 and 1273 K and in α-Fe at 1133 K were measured by exposing Fe samples to known B activities with subsequent photometrical determination of the equilibrium B concentration. The B activity was fixed by the reduction of B 2O 3 with H 2/H 2O mixtures, the ratio of which was in turn established by equilibration with Cr and Cr 2O 3 at a known temperature in a two zone furnace. The partial molar excess Gibbs energies are 10,8 kJ/mol at 1273 K and -1.0 kJ/mol at 1133 K at mole fractions of B below 0.001. The α- and γ-solvus lines were obtained conductometrically from the transition temperature depressions of various alloys. They were proportional to the B mole fractions by factors of-(22.2 ± 0.9)· 10 3 and-(8.2 ± 0.3)· 10 3, respectively.

Thermodynamic Properties of Pd‐X‐Alloys, with X = Gd, Y, Ce

AbstractElectromotive force measurements on cells with a CaF2 solid electrolyte were used to determine the activities of Gd, Y, and Ce in Pd‐rich alloys between 700°C and 800°C. The thermodynamic properties of these alloys are characterized by extreme negative deviations from ideal mixing behavior, up to −400 kJ/mol for the partial molar excess Gibbs energy of Ce and up to −320 kJ/mol for Gd and Y. The high thermodynamic stability of these alloys is attributed to a transfer of valence electrons to the electron gas of the alloy. At infinite dilution the resulting bonding contribution to the partial excess free energy is determined by the difference of the Fermi levels of the components and the valency of the solute. Including the size difference of the components as an additional effect, the mixing behavior of the alloys can be well described. – Within the homogeneity ranges of the intermetallic phases Pd3Y and Pd3Gd the activities of the unnoble components increase by more than ten orders or magnitude.

Thermodynamic Properties of Pt — B Solid Solutions

AbstractThe activity coefficients of B in Pt were determind at 1200 and 1300 K by equilibrating Pt with B2O3 in a controlled H2 – H2O atmosphere and measuring the weight gain. The partial molar excess Gibbs energies at vanishing B concentration are –44 and –43 kJ/ mol, respectively. The atomic fractions at the solidus line are 0.036 and 0.031. A relative lattice contraction of the solid solutions prepared at 1200 and 1300 K of (1/a)(∂a/∂xB) = −0.042 and of −0.035 ± 0.002 was observed. This dependence of the lattice constant on the temperature of preparation suggests a mixed occupation of lattice and interstitial sites, with the majority of B atoms on lattice sites.

Determination of the thermodynamic excess functionsG E,H E, andS E of the liquid ternary system AgCl?LiCl?KCl by means of EMF-measurements

By means of EMF-measurements using the formation cell $$graphite/Ag/AgCl(l,x_{AgCl} ) - LiCl(l,x_{LiCl} ) - KCl x_{KCl} /(Cl_2 )graphite$$ the partial molar excessGibbs energies,GAgClE, of silver chloride in the ternary system AgCl−LiCl−KCl were determined over the whole concentration range at five temperatures between 973 K and 1,123 K.