Thermodynamics of the cell Pt | H2(p)| HCl (m)| AgCl| Ag and primary medium effects upon HCl in (glycerol + water) solvents

The electromotive force (e.m.f.)E of the cellPt|H₂(p)|HCl(m) in Z|AgCl|Ag in {glycerol (G)  +  water (W)} solvents, Z  =  (G  +  W), up to glycerol mass fraction w_G =  0.7 has been measured within the temperature range from 273.15 K to 313.15 K at HCl molalities up to 0.1mol · kg ^− 1. On this basis, the standard molar e.m.f. E_m ^∘ values pertaining to such solvent mixtures have been obtained, and have been combined with sparse literature data for optimization. At glycerol mass fractions up tow_G ≈  0.5, at constant temperature,E_m ^∘  shows a linear dependence on the glycerol mole fractionx_G and, in parallel, E_c ^∘ (on the amount-of-substance concentration scale) shows linear dependence on the glycerol volume fractionϕ_G . The primary medium effect upon HCl, defined as the difference (E_c ^∘ )_W −  (E_c ^∘ )_Z, has been considered as a function of the water volume fraction ϕ_Win terms of Feakins and French’s theory: this would lead to a primary hydration number n(hydr)  =  2.4 for HCl, in good agreement with previous results obtained with solvents other than (glycerol  +  water). In this connection, some basic methodological aspects are discussed. Ancillary values of the densities ρ_Zof the relevant solvent mixtures, which were hitherto unavailable and are necessary for the data processing leading toE_m ^∘  , have also been measured.     

Synthesis,spectroscopic, magnetic and thermal properties of bimetallic salts, [Ni(L)][MCl4] {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. X-ray structure of [Ni(L)][CoCl4]

New bimetallic complex salts corresponding to the formulation [Ni(L)][MCl₄] have been synthesized by the facile reaction between [Ni(L)](ClO₄)₂ and [MCl₂(PPh₃)₂] in high yields {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. The complexes were characterized by IR, electronic spectra, TGA/DSC, magnetic moment and conductivity measurements. The X-ray crystal structure for [Ni(L)][CoCl₄] clearly establishes the cationic–anionic interaction. It crystallizes in the space group P1 with unit cell dimensions a = 7.1740(15) Å, b = 8.1583(16) Å and c = 8.3102(16) Å. A square-planar geometry is evident for the [Ni(L)]²⁺ cation while the anion is found to be tetrahedral. A two-step thermolytic pattern is observed in the pyrolysis of the bimetallic complex salts.     

Vapor pressures,osmotic and activity coefficients for (LiBr + acetonitrile) between the temperatures (298.15 and 343.15) K

Precise vapor pressure data for pure acetonitrile and (LiBr + acetonitrile) are given for temperatures ranging from T=(298.15 to 343.15) K. The molality range is from m=(0.0579 to 0.8298) mol · kg⁻¹. The osmotic coefficients are calculated by taking into account the second virial coefficient of acetonitrile. The parameters of the extended Pitzer ion interaction model of Archer and the mole fraction-based thermodynamic model of Clegg–Pitzer are evaluated. These models accurately reproduce the available osmotic coefficients. The parameters of the extended Pitzer ion interaction model of Archer are used to calculate the mean molal activity coefficients.     

Apparent molar heat capacities and apparent molar volumes ofY2(SO4)3(aq),La2(SO4)3(aq),Pr2(SO4)3(aq),Nd2(SO4)3(aq),Eu2(SO4)3(aq),Dy2(SO4)3(aq),Ho2(SO4)3(aq), andLu2(SO4)3(aq)atT = 298.15 K andp = 0.1 MPa

The apparent molar heat capacities C_{p, φ} ^∘ and apparent molar volumes V_φ ^∘ of Y₂(SO₄)₃(aq), La₂(SO₄)₃(aq), Pr₂(SO₄)₃(aq), Nd₂(SO₄)₃(aq), Eu₂(SO₄)₃(aq), Dy₂(SO₄)₃(aq), Ho₂(SO₄)₃(aq), and Lu₂(SO₄)₃(aq) were measured at T =  298.15 K and p =  0.1 MPa with a Sodev (Picker) flow microcalorimeter and a Sodev vibrating-tube densimeter, respectively. These measurements extend from lower molalities of m =  (0.005 to 0.018) mol ·kg ^− 1to m =  (0.025 to 0.434) mol ·kg ^− 1, where the upper molality limits are slightly below those of the saturated solutions. There are no previously published apparent molar heat capacities for these systems, and only limited apparent molar volume information. Considerable amounts of the R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are present, where R denotes a rare-earth, which complicates the interpretation of these thermodynamic quantities. Values of the ionic molar heat capacities and ionic molar volumes of these complexes at infinite dilution are derived from the experimental information, but the calculations are necessarily quite approximate because of the need to estimate ionic activity coefficients and other thermodynamic quantities. Nevertheless, the derived standard ionic molar properties for the various R SO₄ ⁺ (aq) and R(SO₄)₂ ⁻ (aq) complexes are probably realistic approximations to the actual values. Comparisons indicate that V_φ ^∘ {RSO₄ ⁺ , aq, 298.15K}  =  − (6  ±  4)cm³· mol ^− 1and V_φ ^∘ {R(SO₄)₂ ⁻ , aq, 298.15K}  =  (35  ±  3)cm³· mol ^− 1, with no significant variation with rare-earth. In contrast, values of C_{p, φ} ^∘ { RSO₄ ⁺ , aq, 298.15K } generally increase with the atomic number of the rare-earth, whereas C_{p, φ} ^∘ { R(SO₄)₂ ⁻ , aq, 298.15K } shows a less regular trend, although its values are always positive and tend to be larger for the heavier than for the light rare earths.     

Electronic structure and Raman spectroscopy study of dibarium magnesium orthoborate,Ba2Mg(BO3)2

The samples of dibarium magnesium orthoborate Ba₂Mg(BO₃)₂ were synthesized by solid-state reaction. The X-ray diffraction (XRD) patterns and Raman spectra of the samples were collected. Electronic structure and vibrational spectroscopy of Ba₂Mg(BO₃)₂ were systematically investigated by first principle calculation. A direct band gap of 4.4 eV was obtained from the calculated electronic structure results. The top valence band is constructed from O 2p states and the low conduction band mainly consists of Ba 5d states. Raman spectra for Ba₂Mg(BO₃)₂ polycrystalline were obtained at ambient temperature. The factor group analysis results show the total lattice modes are 5E_u + 4A_2u + 5E_g + 4A_1g + 1A_2g + 1A_1u, of which 5E_g + 4A_1g are Raman-active. Furthermore, we obtained the Raman active vibrational modes as well as their eigenfrequencies using first-principle calculation. With the assistance of the first-principle calculation and factor group analysis results, Raman bands of Ba₂Mg(BO₃)₂ were assigned as E_g (42 cm⁻¹), A_1g (85 cm⁻¹), E_g (156 cm⁻¹), E_g (237 cm⁻¹), A_1g (286 cm⁻¹), E_g (564 cm⁻¹), A_1g (761 cm⁻¹), A_1g (909 cm⁻¹), E_g (1165 cm⁻¹). The strongest band at 928 cm⁻¹ in the experimental spectrum is assigned to totally symmetric stretching mode of the BO₃ units.     

Ionization constants ofo-phthalic acid in (propylene carbonate + water) and (ethylene carbonate + water), and thermodynamics of the cellPt|H2|HCl(m)| Hg2Cl2|Hg

The potential differences E of the cells Pt|H₂|H₂Ph(m₁)  +  KHPh(m₂)  +  KCl(m₃) in Z|AgCl|Ag and Pt|H₂|H₂Ph(m₁)  +  KHPh(m₂)  +  KCl(m₃) in Z|Hg₂Cl₂|Hg have been measured at T =  298.15 K in mixtures Z =  (W + S) of water (W) with cosolvents S =  propylene carbonate (PC) and S =  ethylene carbonate (EC), to determine the first ionization constants K of the o -phthalic acid H₂Ph(benzene-1,2-dicarboxylic acid), which are indispensable for the determination of primary pH-metric standards based on the potassium hydrogen phthalate buffer (KHPh) in such solvent mixtures. The value of K is seen to decrease progressively with increasing mass fraction w_sof the organic cosolvent, as with all of the other cosolvents studied earlier, but no simple relationship with the cosolvent permittivity is discernible. Since the required values of the standard potential difference E^oof the second cell were hitherto missing, they have now been obtained based on potential difference measurements of the cell Pt|H₂|HCl(m) in Z|Hg₂Cl₂|Hg. The primary medium effect (E_W^o − E_Z^o, by Owen’s definition) upon HCl in water-rich mixtures Z is seen to increase linearly with increasing w_s, as in earlier investigations. In this comparative context, the slope of the primary medium effect against w_splots for the aprotic cosolvents increases regularly with decreasing permittivity, whereas for the protic (alcoholic) cosolvents the slope is ill-defined.     

Volumetric properties of (an organic compound + di-n-butyl ether) atT = 298.15 K

Excess molar volumes V_m^Eof {di- n -butyl ether (DBE)  +  a monofunctional organic compound} have been determined atT =  298.15 K over the whole composition range by means of a vibrating-tube densimeter. TheV_m^E values were either positive (propylamine, or butylamine, or acetone, or tetrahydrofuran  +  DBE) or negative (methanol, or butanol, or diethyl ether, or cyclopentanone, or acetonitrile  +  DBE). Markedly asymmetric V_m^Ecurves were displayed by (DBE  +  methanol) and (DBE  +  acetonitrile). Partial molar volumes __ V_m^oat infinite dilution in DBE, both from this work and the literature, were analysed in terms of an additivity scheme, and the group contributions thus obtained were discussed and compared with analogous results in water. DBE revealed a greater capability of distinguishing between polar and non-polar solutes, as well as in discriminating differently shaped molecules (unbranched, branched, cyclic). The limiting slopes of apparent excess molar volumes are evaluated and briefly discussed in terms of solute–solute and solute–solvent interactions.     

Study on the enthalpy of solution and enthalpy of dilution for the ionic liquid [C3mim][Val] (1-propyl-3-methylimidazolium valine)

A new amino acid ionic liquid (AAIL) [C₃mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C₃mim][Val] with known amounts of water and with different concentrations in molality were measured at T = 298.15 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C₃mim][Val] without water, ${\mathrm{\Delta }}_{\text{s}}{H}_{\text{m}}^{\circ }$ = (−55.7 ± 0.4) kJ · mol⁻¹, was obtained. The hydration enthalpy of the cation [C₃mim]⁺, ΔH₊ ([C₃mim]⁺) = −226 kJ · mol⁻¹, was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, Δ_DH_m(m_i → m_f), of aqueous [C₃mim][Val] with various values of molality were measured. The values of Δ_DH_m(m_i → m_f) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, ^φL, calculated using Pitzer’s ion-interaction model.     

Thermodynamics of the hydrolysis reactions of adenosine 3′,5′-(cyclic)phosphate(aq) and phosphoenolpyruvate(aq); the standard molar formation properties of 3′,5′-(cyclic)phosphate(aq) and phosphoenolpyruvate(aq)

Molar calorimetric enthalpy changes Δ_rH_m(cal) have been measured for the biochemical reactions {cAMP(aq) + H₂O(l)=AMP(aq)} and {PEP(aq) + H₂O(l)=pyruvate(aq) + phosphate(aq)}. The reactions were catalyzed, respectively, by phosphodiesterase 3^′,5^′-cyclic nucleotide and by alkaline phosphatase. The results were analyzed by using a chemical equilibrium model to obtain values of standard molar enthalpies of reaction Δ_rH_m^∘ for the respective reference reactions {cAMP⁻(aq) + H₂O(l)=HAMP⁻(aq)} and {PEP³⁻(aq) + H₂O(l)=pyruvate⁻(aq) + HPO²⁻₄(aq)}. Literature values of the apparent equilibrium constants K^′ for the reactions {ATP(aq)=cAMP(aq) + pyrophosphate(aq)}, {ATP(aq) + pyruvate(aq)=ADP(aq) + PEP(aq)}, and {ATP(aq) + pyruvate(aq) + phosphate(aq)=AMP(aq) + PEP(aq) + pyrophosphate(aq)} were also analyzed by using the chemical equilibrium model. These calculations yielded values of the equilibrium constants K and standard molar Gibbs free energy changes Δ_rG_m^∘ for ionic reference reactions that correspond to the overall biochemical reactions. Combination of the standard molar reaction property values (K, Δ_rH_m^∘, and Δ_rG_m^∘) with the standard molar formation properties of the AMP, ADP, ATP, pyrophosphate, and pyruvate species led to values of the standard molar enthalpy Δ_fH_m^∘ and Gibbs free energy of formation Δ_fG_m^∘ and the standard partial molar entropy S_m^∘ of the cAMP and PEP species. The thermochemical network appears to be reasonably well reinforced and thus lends some confidence to the accuracy of the calculated property values of the variety of species involved in the several reactions considered herein.     

Measurements of HmE and VmE for (n-butane + sulphur hexafluoride) in the supercritical region at the pressure 6.00 MPa

A flow mixing calorimeter followed by a vibrating-tube densimeter has been used to measure excess molar enthalpies H_m^E and excess molar volumes V_m^E of {xC₄H₁₀+(1−x)SF₆}. Measurements over a range of mole fractions x have been made in the supercritical region at the pressure p=6.00 MPa and at seven temperatures in the range T=311.25 K to T=425.55 K. The H_m^E(x) measurements at T=351.35 K were found to exhibit an unusual double maximum. Measurements at all temperatures are compared with the Patel–Teja equation of state with the parameters determined by solving a cubic equation as recommended, and also with parameters determined by the method suggested by Valderamma and Cisternas who proposed equations which are a function of the critical compression factor. The overall fit to the H_m^E and V_m^E measurements obtained using Valderamma and Cisternas equations was found to be better than that obtained using the parameters according to the method suggested by Patel and Teja.     

Excess thermodynamic properties of binary mixtures of N,N-dimethylacetamide with water or water-d2 at temperatures from 277.13 K to 318.15 K

Densities of binary mixtures of N,N-dimethylacetamide (DMA) with water (H₂O) or water-d₂ (D₂O) were measured at the temperatures from T=277.13 K to T=318.15 K by means of a vibrating-tube densimeter. The excess molar volumes V_m^E, calculated from the density data, are negative for the (H₂O + DMA) and (D₂O + DMA) mixtures over the entire range of composition and temperature. The V_m^E curves exhibit a minimum at x(DMA)≅0.4. At each temperature, this minimum is slightly deeper for the (D₂O + DMA) mixtures than for the corresponding (H₂O + DMA) mixtures. The difference between D₂O and H₂O systems becomes smaller when the temperature increases. The V_m^E results were correlated using a modified Redlich–Kister expansion. The partial molar volume of DMA plotted against x(DMA) goes through a sharp minimum in the water-rich region around x(DMA)≅0.08. This minimum is more pronounced the lower the temperature and is deeper in D₂O than in H₂O at each temperature. Again, the difference becomes smaller as the temperature increases. The excess expansion factor α^E plotted against x(DMA) exhibit a maximum in the water rich region of the mole fraction scale. At each temperature, this maximum is higher for the (D₂O + DMA) mixtures than for the corresponding (H₂O + DMA) mixtures, and the difference becomes smaller as the temperature increases. At its maximum, α^E can be even more than 25 per cent of total value of the cubic expansion coefficient α in the (H₂O + DMA) and (D₂O + DMA) mixtures.     

Volumetric study of (2-methoxyethanol + tetrahydrofuran + cyclohexane) at T=298.15 K

The excess molar volumes V_m^E at T=298.15 have been determined in the whole composition domain for (2-methoxyethanol + tetrahydrofuran + cyclohexane) and for the parent binary mixtures. Data on V_m^E are also reported for (2-ethoxyethanol + cyclohexane). All binaries showed positive V_m^E values, small for (methoxyethanol + tetrahydrofuran) and large for the other ones. The ternary V_m^E surface is always positive and exhibits a smooth trend with a maximum corresponding to the binary (2-methoxyethanol + cyclohexane). The capabilities of various models of either predicting or reproducing the ternary data have been compared. The behaviour of V_m^E and of the excess apparent molar volume of the components is discussed in both binary and ternary mixtures. The results suggest that hydrogen bonding decreases with alcohol dilution and increases with the tetrahydrofuran content in the ternary solutions.     

Near critical measurements of HmE andVmE for (ethane + sulphur hexafluoride)

A flow mixing calorimeter and a vibrating-tube densimeter have been used to measure excess molar enthalpies H_m^E and excess molar volumes V_m^E of {xC₂H₆ +  (1  − x)SF₆ }. Measurements over a range of mole fractions x have been made at T =  305.65 K and T =  312.15 K and at the pressures (3.76, 4.32, 4.88 and 6.0) MPa. The pressure 3.76 MPa is close to the critical pressure of SF₆, the pressure 4.88 MPa is close to the critical pressure of C₂H₆, and the pressure 4.32 MPa is midway between these values. The measurements are compared with the Patel–Teja equation of state which reproduces the main features of the excess function curves as well as it does for similar measurements on {xCO₂ +  (1  − x)C₂H₆ }, {xCO₂ +  (1  − x)C₂H₄ } and {xCO₂ +  (1  − x)SF₆ }.     

Measurements of HmE and VmE for (propane + sulphurhexafluoride) in the near critical region

A flow mixing calorimeter followed by a vibrating-tube densimeter has been used to measure excess molar enthalpies H_m^E and excess molar volumesV_m^E of {xC₃H₈ +  (1  − x)SF₆}. Measurements over a range of mole fractionsx have been made at the pressure p =  4.30 MPa at eight temperatures in the rangeT =  314.56 K to 373.91 K, in the liquid region at p =  3.75 MPa andT =  314.56 K, in the two phase region at p =  3.91 MPa andT =  328.18 K, and in the supercritical region at p =  5.0 MPa andT =  373.95 K. The measurements are compared with results from the Patel–Teja equation of state which reproduces the main features of the excess function curves as well as it does for similar measurements on{xCO₂ +  (1  − x)C₂H₆} ,{xCO₂ +  (1  − x)C₂H₄} and{xCO₂ +  (1  − x)SF₆} reported previously.     

The enthalpy of dilution and thermodynamics of Na2CO3(aq) and NaHCO3(aq) fromT = 298 K toT = 523.15 K and pressure of 40 MPa

Molar enthalpies of dilution Δ_dilH_mofNa₂CO₃(aq) were measured from molality m =  1.45 mol · kg ^− 1to m =  0.008 mol · kg ^− 1at seven temperatures from T =  298 K toT =  523 K at the pressure p =  7 MPa, and at four temperatures fromT =  371 K to T =  523 K at the pressurep =  40 MPa. Molar enthalpies of dilutionΔ_dilH_m of NaHCO₃(aq) were measured fromm =  0.98 mol · kg ^− 1tom =  0.007 mol · kg ^− 1at the same temperatures and pressures. Hydrolysis and ionization equilibria contribute substantially to the measured enthalpies under many of the conditions of this study. Explicit consideration of these reactions, using thermodynamic quantities from previous studies, facilitates a quantitative representation of apparent molar enthalpies, activity coefficients, and osmotic coefficients with the Pitzer ion-interaction treatment over the ranges of temperature, pressure, and molality of the experiments.     

Doping effect of nonmagnetic impurity on the spin-Peierls-like transition in the quasi-one-dimensional (quasi-1D) spin system of 1-(4′-nitrobenzyl)pyridinium bis(maleonitriledithiolato)nickelate

A nonmagnetic compound, [NO₂BzPy][Cu(mnt)₂] (mnt^2? = maleonitriledithiolate; NO₂BzPy⁺ = 1-(4′-nitrobenzyl)pyridinium), is isostructural with [NO₂BzPy][Ni(mnt)₂], which is a quasi-1D spin system and exhibits a spin-Peierls-like transition with J = 192 K in the gapless state and spin energy gap = 738 K in the dimerization state, respectively. Further, five nonmagnetic impurity doped compounds [NO₂BzPy][Cu_xNi_1?x(mnt)₂] (x = 0.04–0.74) were prepared, and their crystal structures as well as magnetic properties were investigated. The nonmagnetic doping causes the suppression of the spin transition with an average rate of 139(13) K/percentage of dopant concentration, and the transition collapse is estimated at around x > 0.5.     

(Vapour + liquid) equilibria and excess molar enthalpies for mixtures with strong complex formation. Trichloromethane or 1-bromo-1-chloro-2,2,2-trifluoroethane (halothane) with tetrahydropyran or piperidine

Isothermal (vapour  +  liquid) equilibria were measured for (trichloromethane  +  tetrahydropyran or piperidine) at T =  333.15 K and {1-bromo-1-chloro-2,2,2-trifluoroethane (halothane)  +  tetrahydropyran or piperidine} atT =  323.15 K with a circulation still. The results were verified by effective statistical procedures and used to calculate activity coefficients and excess molar Gibbs free energiesG_m^E . Excess molar enthalpiesH_m^E for these mixtures were determined at T =  298.15 K by means of an isothermal CSC microcalorimeter equipped with recently reconstructed flow mixing cells. Reliable performance of the calorimetric setup was proved by the good agreement of H_m^Efor (hexane  +  cyclohexane), (2-propanone  +  water), and (methanol  +  water), with the best literature results. The trichloromethane- or halothane-containing mixtures exhibit strong negative deviations from Raoult’s law and are highly exothermic, thus indicating that complex formation via hydrogen bonding is a governing nonideality effect. A close similarity in the behaviour of corresponding mixtures with trichloromethane and halothane is observed, but for halothane-containing mixtures,G_m^E and H_m^Eare consistently more negative, confirming that halothane is a more powerful proton donor than chloroform.     

Measurement of densities and excess molar volumes for (1,2-propanediol,or 1,2-butanediol + water) at the temperatures (288.15, 298.15, and 308.15) K and at the pressures (0.1, 20, 40, and 60) MPa

Excess molar volumes V_m^Eof (1,2-propanediol  +  water) and (1,2-butanediol  +  water) were measured at temperatures of (288.15, 298.15, and 308.15) K and at pressures of (0.1, 20, 40, and 60) MPa with a densimeter, model DMA 512p from Anton Paar. Values of V_m^Ewere negative for all the mixtures studied over the whole concentration range and for all temperatures and pressures. Results were correlated by polynomial equations of Redlich and Kister and of Myers and Scott.     

The excess molar enthalpies of (N-methyl-2-pyrrolidinone + mono-, or di-, or trichlorobenzene) atT = 298.15 K

Excess molar enthalpies H_m^EatT =  298.15 K are reported for (N -methyl-2-pyrrolidinone  +  chlorobenzene, or 1,2-dichlorobenzene, or 1,3-dichlorobenzene, or 1,2,4,-trichlorobenzene). The values ofH_m^E were obtained by using the flow calorimetric method. All the mixtures, over the whole composition range, are formed exothermically. The H_m^Eresults are discussed in terms of the NRTL and UNIQUAC models.