Measurements of the critical parameters for {xNH3 + (1 − x)H2O} with x = (0.9098, 0.7757, 0.6808)

Measurements of the critical parameters for {xNH₃ + (1 ? x)H₂O} with x = (0.9098, 0.7757, 0.6808) were carried out by using a metal-bellows variable volumometer with an optical cell. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than 3.2 mK, 3.2 kPa, 0.3 kg · m^?3, and 8.8 · 10^?4, respectively. In each mole fraction, the critical temperature T_c was first determined on the basis of the intensity of the critical opalescence. The critical pressure p_c and critical density ρ_c were then determined as the point at which the meniscus disappears on the isotherm at T = T_c. The expanded uncertainties (k = 2) in the present critical parameters have also been estimated. Comparisons of the present values with the literature data as well as the calculated values afforded using the equation of state are also presented.     

Gas-tight proton-conducting Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) ceramics

Journal of Solid State Electrochemistry - Gas-tight Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) pyrochlore materials have been prepared via...     

Thermodynamic study of (alkyl esters + α,ω-alkyl dihalides) III. HmEandVmE for 20 binary mixtures {xCu − 1H2u − 1CO2C4H9 + (1 − x)α,ω-ClCH2(CH2)v − 2CH2Cl}, where u = 1 to 4, α = 1 and v = ω = 2 to 6

In this article, the experimental data of excess molar enthalpies $H_{\mathrm{m}}^{\mathrm{E}}$ and excess molar volumes $V_{\mathrm{m}}^{\mathrm{E}}$ are presented for a set of 20 binary mixtures comprised of the first four butyl alkanoates (methanoate to butanoate) and five α,ω-dichloroalkanes (1,2-dichloroethane to 1,6-dichlorohexane), obtained at atmospheric pressure and at a temperature of 298.15 K. The results indicate the existence of specific interactions between both kinds of compounds resulting in exothermic processes for most mixtures, except for those containing butyl methanoate which give rise to net endo/exothermic effects. The $V_{\mathrm{m}}^{\mathrm{E}}$ are positive for mixtures of (butyl esters + 1,2-dichloroethane or 1,3-dichloropropane) and negative for the remaining ones. The change in $H_{\mathrm{m}}^{\mathrm{E}}$ with the dichloroethane chain length for a same ester is regular although the $V_{\mathrm{m}}^{\mathrm{E}}$ presents an irregular variation. It can, therefore, be deuced from this that the mixing process involves both effects, exothermic/endothermic and expansion/contraction, simultaneously. The behaviour of the mixtures is interpreted on the basis of the results observed and attributed to different effects taking place among the molecules studied.To improve application of the UNIFAC model using the version of Dang and Tassios, average values were recalculated again for parameters of the ester/chloride interaction, distinguishing, during its application, the functional group of the acid part of the ester. In spite of this, the model does not adequately reproduce the systems’ behaviour.     

The (p, ρ, T) properties and apparent molar volumes Vϕ of (ZnBr2 + C2H5OH)

The (p, ρ, T) properties and apparent molar volumes V_? of ZnBr₂ in ethanol at temperatures (293.15 to 393.15) K and pressures up to p = 40 MPa are reported. The measurements were made with a recently developed vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, ethanol, and aqueous NaCl solutions. The experiments were carried out at molalities of m = (0.05681, 0.16958, 0.30426, 0.43835, 0.93055, 1.49016, and 1.88723) mol · kg^?1 using zinc bromide. An empirical correlation for the density of (ZnBr₂ + C₂H₅OH) with pressure, temperature, and molality has been derived. This equation of state was used to calculate other volumetric properties such as isothermal compressibility, isobaric thermal expansibility, the differences in specific heat capacities at constant pressures and volumes, apparent molar volumes of ZnBr₂ in ethanol, and partial molar volumes of both components.     

(Solid + liquid) equilibria for the ternary system (CsBr + LnBr3 + H2O) (Ln = Pr,Nd, Sm) at T = 298.2 K and atmospheric pressure,thermal and fluorescent properties of Cs2LnBr5·10H2O

The (solid + liquid) phase equilibria of the ternary systems (CsBr + LnBr₃ + H₂O) (Ln = Pr, Nd, Sm) at T = 298.2 K were studied by the isothermal solubility method. The solid phases formed in the systems were determined by the Schreinemakers wet residues technique, and the corresponding phase diagrams were constructed based on the measured data. Each of the phase diagrams, with two invariant points, three univariant curves, and three crystallization regions corresponding to CsBr, Cs₂LnBr₅·10H₂O and LnBr₃·nH₂O (n = 6, 7), respectively, belongs to the same category. The new solid phase compounds Cs₂LnBr₅·10H₂O are incongruently soluble in water, and they were characterized by chemical analysis, XRD and TG-DTG techniques. The standard molar enthalpies of solution of Cs₂PrBr₅·10H₂O, Cs₂NdBr₅·10H₂O and Cs₂SmBr₅·10H₂O in water were measured to be (52.49 ± 0.48) kJ · mol⁻¹, (49.64 ± 0.49) kJ · mol⁻¹ and (50.17 ± 0.48) kJ · mol⁻¹ by microcalorimetry under the condition of infinite dilution, respectively, and their standard molar enthalpies of formation were determined as being −(4739.7 ± 1.4) kJ · mol⁻¹, −(4728.4 ± 1.4) kJ · mol⁻¹ and −(4724.4 ± 1.4) kJ · mol⁻¹, respectively. The fluorescence excitation and emission spectra of Cs₂PrBr₅·10H₂O, Cs₂NdBr₅·10H₂O and Cs₂SmBr₅·10H₂O were measured. The results show that the upconversion spectra of the three new solid phase compounds all exhibit a peak at 524 nm when excited at 785 nm.     

Synthesis,characterization and thermochemistry of Cs(ASP) · nH2O (n = 0, 1)

New compounds of aspartic acid Cs(ASP) · nH₂O (n = 0, 1) have been synthesized and characterized by XRD, IR and Raman spectroscopy as well as TG. The structural formula of this new compound was Cs(ASP) · nH₂O (n = 0, 1). The enthalpy of solution of Cs(ASP) · nH₂O (n = 0, 1) in water were determined. With the incorporation of the standard molar enthalpies of formation of CsOH(aq) and ASP(s), the standard molar enthalpy of formation of −(1202.9 ± 0.2) kJ · mol⁻¹ of Cs(ASP) and −(1490.7 ± 0.2) kJ · mol⁻¹ of Cs(ASP) · H₂O were obtained.     

Thermodynamics of formation of double salts M2SO4 · M′SO4 · 6H2O and M2SeO4 · M′SeO4 · 6H2O where M denotes Rb,or Cs and M′ denote Co,Ni, or Zn

This paper describes a chemical model that calculates (solid + liquid) equilibria in the (m₁Rb₂SO₄ + m₂CoSO₄)(aq), (m₁Rb₂SeO₄ + m₂CoSeO₄)(aq), (m₁Rb₂SO₄ + m₂NiSO₄)(aq), (m₁Rb₂SO₄ + m₂ZnSO₄)(aq), (m₁Rb₂SeO₄ + m₂ZnSeO₄)(aq), (m₁Cs₂SO₄ + m₂CoSO₄)(aq), (m₁Cs₂SeO₄ + m₂CoSeO₄)(aq), (m₁Cs₂SO₄ + m₂NiSO₄)(aq), (m₁Cs₂SeO₄ + m₂NiSeO₄)(aq), (m₁Cs₂SO₄ + m₂ZnSO₄)(aq), and (m₁Cs₂SeO₄ + m₂ZnSeO₄)(aq) systems, where m denotes molality at the temperature T=298.15 K. The Pitzer ion-interaction model has been used for thermodynamic analysis of the experimental osmotic and solubility data presented in the literature. The thermodynamic functions needed (binary and ternary parameters of ionic interaction, thermodynamic solubility products) have been calculated and the theoretical solubility isotherm has been plotted. The mixing parameters {θ(MN) and ψ(MNX)} have been chosen on the basis of the compositions of saturated ternary solutions and data on the binary solubility of the sulfate M₂SO₄. M^′SO₄ · 6H₂O double salts in water. To validate the mixing solutions model two different approaches have been used in evaluation of the ternary parameters: (I) preserving the same value of the binary mixing θ(MN) for the corresponding chloride, bromide, sulfate, and selenate systems with the same cations, and (II) with constant θ(MN) value (set equal to −0.05) for the all 11 sulfate and selenate systems. Very good agreement between experimentally determined and model predicted solubilities has been found. Important thermodynamic characteristics (thermodynamic solubility products, standard molar Gibbs free energy of formation) of the solid phases (simple salts, six sulfate – M₂SO₄ · M^′SO₄ · 6H₂O, and five selenate – M₂SeO₄ · M^′SeO₄ · 6H₂O – double salts) crystallizing in the systems under consideration are determined.     

Enhancing the rate capability of high capacity xLi2MnO3 · (1 − x)LiMO2 (M = Mn,Ni, Co) electrodes by Li–Ni–PO4 treatment

The rate capability of high capacity xLi₂MnO₃ · (1 ? x)LiMO₂ (M = Mn, Ni, Co) electrodes for lithium-ion batteries has been significantly enhanced by stabilizing the electrode surface by reaction with a Li–Ni–PO₄ solution, followed by a heat-treatment step. Reversible capacities of 250 mAh/g at a C/11 rate, 225 mAh/g at C/2 and 200 mAh/g at C/1 have been obtained from 0.5Li₂MnO₃ · 0.5LiNi_0.44Co_0.25Mn_0.31O₂ electrodes between 4.6 and 2.0 V. The data bode well for their implementation in batteries that meet the 40-mile range requirement for plug-in hybrid vehicles.