Determination of thermodynamic properties of triple phases formed in different regions of phase diagram of the Ag-Bi-S system using EMF measurements

The technique of measurement of electromotive force (EMF technique) in reversible cells of solid-state galvanic cells with RbAg₄I₅ as solid electrolyte was used to determine standard thermodynamic properties of triple phases in the system of Ag-Bi-S in equilibrium with metallic bismuth. The results are compared to the available literature data obtained in equilibrium with crystalline sulfur.     

Determination of thermodynamic properties of aqueous mixtures of RbCl and Rb2SO4 by the EMF method at T=298.15 K

The thermodynamic properties, including activity coefficients, osmotic coefficients and excess Gibbs free energy for RbCl and Rb₂SO₄ aqueous mixtures at T=298.15 K and in 0.01 mol · kg⁻¹ to 5 mol · kg⁻¹ ionic strength, were determined by emf measurements. The Rb–ISE and Ag–AgCl electrodes used in this work were prepared in our laboratory and had a reasonably good Nernst response. The experimental data were fitted by using the Harned rule and Pitzer model. The Harned coefficients and the Pitzer binary and ternary interaction parameters for the system have been evaluated. The experimental results obey the Harned rule. The Pitzer model can be used to describe this aqueous system satisfactorily.     

Determination of the thermodynamic properties of the Li2CaThF8 in Li-Ca-Th-F system by the solid-state electrochemical cell method

Journal of Solid State Electrochemistry - In the present paper, we have reported the standard molar Gibbs energy of formation for Li2CaThF8(s) measured by solid electrolyte galvanic cell technique...     

电动势法对LiCl-Li~2SO~4-H~2O体系25℃热力学性质研究

用自制的锂离子选择电极和经典Ag-AgCl电极,测定25℃时LiCl-Li~2SO~4-H~2O三元体系中离子强度0.01～6.0mol.kg^-1的LiCl平均活度系数.,由实验数据,用多元线性回归法求取Pitzer方程、Harned方程的离子作用参数和系数,并用上述方程计算LiCl在混合溶液中的平均活度系数,分别以Inγ~±LiCl和logγ~±LiCl的形式与实验值进行比较,标准偏差均小于0.008.本工作测得的LiCl平均活度系数的自然对数与等压法测定的渗透系数拟合的Pitzer方程参数计算值比较,标准偏差为0.0097.同时计算了Li~2SO~4在该体系中的平均活度系数和混合溶液的渗透系数以及混合超额自由能.     

Accurate measurements of thermodynamic properties of solutes in ionic liquids using inverse gas chromatography

Activity coefficients at infinite dilution of 29 organic compounds in two room temperature ionic liquids were determined using inverse gas chromatography. The measurements were carried out at different temperatures between 323.15 and 343.15K. To establish the influence of concurrent retention mechanisms on the accuracy of activity coefficients at infinite dilution for 1-butyl-3-methylimidazolium octyl sulfate and 1-ethyl-3-methylimidazolium tosylate, phase loading studies of the net retention volume per gram of packing as a function of the percent phase loading were used. It is shown that most of the solutes are retained largely by partition with a small contribution from adsorption on 1-butyl-3-methylimidazolium octyl sulfate and that the n-alkanes are retained predominantly by interfacial adsorption on 1-ethyl-3-methylimidazolium tosylate.     

Determination of thermodynamic properties of YRhO3(s) by solid-state electrochemical cell and differential scanning calorimeter

The standard molar Gibbs free energy of formation of YRhO₃(s) has been determined using a solid-state electrochemical cell wherein calcia-stabilized zirconia was used as an electrolyte. The cell can be represented by: ( - )\textPt - Rh/{ \textY₂\textO_\text3( \texts ) + \textYRh\textO₃( \texts ) + \textRh( \texts ) }//\textCSZ//\textO₂( p( \textO₂ ) = 21.21  \textkPa )/\textPt - Rh( + ) \left( - \right){\text{Pt - Rh/}}\left\{ {{{\text{Y}}_2}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right) + {\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right) + {\text{Rh}}\left( {\text{s}} \right)} \right\}//{\text{CSZ//}}{{\text{O}}_2}\left( {p\left( {{{\text{O}}_2}} \right) = 21.21\;{\text{kPa}}} \right)/{\text{Pt - Rh}}\left( + \right) . The electromotive force was measured in the temperature range from 920.0 to 1,197.3 K. The standard molar Gibbs energy of the formation of YRhO₃(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by: D_\textfG^\texto{ \textYRh\textO₃( \texts ) }/\textkJ  \textmo\textl ^{- 1}( ±1.61 ) = - 1,147.4 + 0.2815  T  ( \textK ) {\Delta_{\text{f}}}{G^{\text{o}}}\left\{ {{\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right)} \right\}/{\text{kJ}}\;{\text{mo}}{{\text{l}}^{ - 1}}\left( {\pm 1.61} \right) = - 1,147.4 + 0.2815\;T\;\left( {\text{K}} \right) . Standard molar heat capacity C^o_p,m C^{o}_{{p,m}} (T) of YRhO₃(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges from 127 to 299 K and 305 to 646 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: $ {*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ $ \begin{array}{*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ \end{array} The heat capacity of YRhO₃(s) was used along with the data obtained from the electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K.     

Transference numbers of aqueous NaCl and Na2SO4 at 25°C from EMF measurements with sodium-selective glass electrodes

Transference numbers in aqueous solutions of NaCl and Na ₂ SO ₄ were obtained by measuring the emf of cells with liquid junction using sodium-selective glass electrodes. Transference numbers in the NaCl–H₂O system from about 0.1 to 4 mol-kg ^–1 (m) are in good agreement with literature data obtained by various experimental techniques, but are markedly lower than recent data obtained from emf measurements with Ag,AgCl-electrodes. Transference numbers in the Na ₂ SO ₄ –H ₂ O system from about 0.03 to 1.9 m show a small decrease with increasing salt concentration, which is near the limit of experimental uncertainty. Sodium-selective electrodes are well suited to perform determinations of transference numbers and may provide an alternative to amalgam electrodes.     

Dynamic versions of EMF method in studies of phase formation and thermodynamic properties of metal alloys

Using dynamic versions of emf method, potential study of phase formation and thermodynamic properties was shown in all the equilibrium diagram of the studied systems, phase formation parameters and thermodynamic characteristics of oversaturated liquid and solid metal solutions were found for the first time.     

Determination of thermodynamic properties of the ternary oxides in the Y-Ru-O system by electromotive force measurements and differential scanning calorimetric measurements

Journal of Solid State Electrochemistry - In this study, the standard molar Gibbs energy of formation of Y2Ru2O7(s) and Y3RuO7(s) was determined using calcia-stabilized zirconia (CSZ) as an...     

Determination of thermodynamic properties by supercritical fluid chromatography

This survey attempts to summarise thermodynamic applications of supercritical fluid chromatography (SFC) with an emphasis on the results published during the last 10 years. In addition to a review of thermodynamic measurements by SFC, it contains brief sections on instrumental considerations and on the sources of auxiliary information needed when processing the retention data.     

Heat-capacity measurements and thermodynamic functions of crystalline adenine; revised thermodynamic properties of aqueous adenine

The standard molar heat capacity C^°_p,m of adenine(cr) has been measured using adiabatic calorimetry over the range 6<(T/K)<310 and the results used to derive thermodynamic functions for adenine(cr) at smoothed temperatures. At T=298.15 K, C^°_p,m=(142.67±0.29) J · K⁻¹ · mol⁻¹ and the third law entropy S^°_m=(145.62±0.29) J · K⁻¹ · mol⁻¹. The standard molar Gibbs free energy of formation Δ_fG^°_m at T=298.15 K for crystalline adenine was calculated, using the standard molar enthalpy of formation for the compound and entropies of the elements from the literature, and found to be Δ_fG^°_m=(301.4±1.0) kJ · mol⁻¹. The results were combined with solution calorimetry and solubility measurements from the literature to yield revised values for the standard molar thermodynamic properties of aqueous adenine at T=298.15 K: Δ_fG^°_m=(313.4±1.0) kJ · mol⁻¹, Δ_fH^°_m=(129.5±1.4) kJ · mol⁻¹, and S_m^°=(217.68±0.44) J · K⁻¹ · mol⁻¹.     

Determination of dynamic properties of flax fibres reinforced laminate using vibration measurements

Experimental and numerical methods to identify the linear viscoelastic properties of flax fibre reinforced polymer (FFRP) composite are presented in this study. The method relies on the evolution of storage modulus and loss factor as observed through the frequency response. Free-free symmetrically guided beams were excited in the dynamic range of 10 Hz to 4 kHz with a swept sine excitation focused around their first modes. A fractional derivative Zener model has been identified to predict the complex moduli. A modified ply constitutive law has been then implemented in a classical laminates theory calculation (CLT) routine. Overall, the Zener model fitted the experimental results well. The storage modulus was not frequency dependant, while the loss factor increased with frequency and reached a maximum value for a fibre orientation of 70°. The damping of FFRP was, respectively, 5 and 2 times higher than for equivalent carbon and glass fibres reinforced epoxy composites.     

A thermodynamic study of the Cu-Cr-O system by the EMF method

The equilibrium oxygen pressures of the three-phase regions [Cu, Cr₂O₃, Cu₂Cr₂O₄], [Cu, Cu₂O, Cu₂O₂O₄] and [CuO, Cu₂O, Cu₂Cr₂O₄] were measured as a function of temperature by the solid oxide electrolyte electromotive force method. The measured Gibbs energy of the reaction Cu₂O+ Cr₂O₂ = Cu₂Cr₂O₄ (ΔG°) was found to be −46608 + 7.8328 T J mol⁻¹ (1075–1275 K). The evaluated Gibbs energy of formation of Cu₂Cr₂O₄ (ΔG°(inf,Cu₂Cr₂O₄)) was found to be −1332900 + 332.761 T J mol⁻¹ (900–1350 K).     

Estimation of 2nd-order derivative thermodynamic properties using the crossover lattice equation of state

We apply the crossover lattice equation of state (xLF EOS) [M.S. Shin, Y. Lee, H. Kim, J. Chem. Thermodyn. 40 (2007) 174–179] to the calculations of thermodynamic 2nd-order derivative properties (isochoric heat capacity, isobaric heat capacity, isothermal compressibility, thermal expansion coefficient, Joule–Thompson coefficient, and sound speed). This equation of state is used to calculate the same properties of pure systems (carbon dioxide, normal alkanes from methane to propane). We show that, over a wide range of states, the equation of state yields properties with better accuracy than the lattice equation of state (LF EOS), and near the critical region, represents singular behavior well.     

Low-temperature heat capacity and thermodynamic properties of layered perovskite-like oxides NaNdTiO4 and Na2Nd2Ti3O10

We report the results of the study of thermodynamic properties for layered perovskite-like oxides NaNdTiO₄ and Na₂Nd₂Ti₃O₁₀. Isobaric heat capacity of the compounds was measured in an adiabatic calorimeter in the range of 5–340 K. Low-temperature heat capacity anomaly was observed in the heat capacity curve of Na₂Nd₂Ti₃O₁₀. Standard thermodynamic properties of the oxides were evaluated from the experimental heat capacity temperature dependencies. Finally, on the basis of the experimental data obtained in this work, we tested applicability of the additivity principle for prediction of thermodynamic properties for layered compounds built of fragments of various structural types.     

Activity coefficients of NaCl in polyelectrolyte solutions from EMF measurements

Electromotive force (EMF) data were measured at 298.15 K for the cell, Na–ISE |polyelectrolyte(m_p), NaCl(m_s)| AgCl, Ag, where a salt NaCl with different concentrations is added in aqueous poly(diallyl dimethyl ammonium chloride), poly(anethole sulfonic acid, sodium salt) and sodium polyacrylate solutions, respectively. ISE means ion-selective electrode. Mean activity coefficients of the salt NaCl in these aqueous polyelectrolyte solutions were calculated correspondingly. The standard cell potential needed for calculations were obtained from EMF measurements of an another cell, Na–ISE |NaCl(m)| AgCl, Ag, where the solution contains only a single electrolyte. Activity coefficients of the electrolyte NaCl in this cell were estimated by Pitzer model. For poly(diallyl dimethyl ammonium chloride) solutions with different concentrations, mean activity coefficients of the salt NaCl decrease monotonically as the concentration of NaCl increases. However, for poly(anethole sulfonic acid, sodium salt) solutions and sodium polyacrylate solutions, the salt-concentration dependence of the mean activity coefficients of NaCl exhibit a maximum.     

The thermodynamic properties of Ba2SrUO6

The standard enthalpy of formation of crystalline Ba₂SrUO₆ at 298.15 K was determined by reaction calorimetry (-2940.0 ± 8.5 kJ/mol). The heat capacity of the compound was measured over the temperature range 8-330 K by adiabatic vacuum calorimetry. The thermodynamic functions of Ba₂SrUO₆ were calculated. The standard entropy (-558.6 ± 2.1 J/(mol K)) and Gibbs function of formation at 298.15 K (-2773.5 ± 9.0 kJ/mol) were determined.     

Systems Ln-Fe-O (Ln=Eu, Gd): thermodynamic properties of ternary oxides using solid-state electrochemical cells

The standard molar Gibbs energies of formation of LnFeO₃(s) and Ln₃Fe₅O₁₂(s) where Ln=Eu and Gd have been determined using solid-state electrochemical technique employing different solid electrolytes. The reversible e.m.f.s of the following solid-state electrochemical cells have been measured in the temperature range from 1050 to 1255 K.Cell (I): (−)Pt / {LnFeO₃(s)+Ln₂O₃(s)+Fe(s)} // YDT/CSZ // {Fe(s)+Fe_0.95O(s)} / Pt(+);Cell (II): (−)Pt/{Fe(s)+Fe_0.95O(s)}//CSZ//{LnFeO₃(s)+Ln₃Fe₅O₁₂(s)+Fe₃O₄(s)}/Pt(+);Cell (III): (−)Pt/{LnFeO₃(s)+Ln₃Fe₅O₁₂(s)+Fe₃O₄(s)}//YSZ//{Ni(s)+NiO(s)}/Pt(+);andCell(IV):(−)Pt/{Fe(s)+Fe_0.95O(s)}//YDT/CSZ//{LnFeO₃(s)+Ln₃Fe₅O₁₂(s)+Fe₃O₄(s)}/Pt(+).The oxygen chemical potentials corresponding to the three-phase equilibria involving the ternary oxides have been computed from the e.m.f. data. The standard Gibbs energies of formation of solid EuFeO₃, Eu₃Fe₅O₁₂, GdFeO₃ and Gd₃Fe₅O₁₂ calculated by the least-squares regression analysis of the data obtained in the present study are given byΔ_fG°_m(EuFeO₃, s) /kJ mol⁻¹ (± 3.2)=−1265.5+0.2687(T/K)   (1050 ? T/K ? 1570),Δ_fG°_m(Eu₃Fe₅O₁₂, s)/kJ mol⁻¹ (± 3.5)=−4626.2+1.0474(T/K)   (1050 ? T/K ? 1255),Δ_fG°_m(GdFeO₃, s) /kJ mol⁻¹ (± 3.2)=−1342.5+0.2539(T/K)   (1050 ? T/K ? 1570),andΔ_fG°_m(Gd₃Fe₅O₁₂, s)/kJ·mol⁻¹ (± 3.5)=−4856.0+1.0021(T/K)   (1050 ? T/K ? 1255).The uncertainty estimates for Δ_fG°_m include the standard deviation in the e.m.f. and uncertainty in the data taken from the literature. Based on the thermodynamic information, oxygen potential diagrams for the systems Eu-Fe-O and Gd-Fe-O and chemical potential diagrams for the system Gd-Fe-O were computed at 1250 K.