Volumetric properties of a stoichiometric mixture of K+ and Br− ions in H/D isotope-substituted aqueous methanol at 278.15–318.15 K: I. The H2O-CH3OH-KBr system

The densities of potassium bromide solutions in aqueous methanol mixtures have been measured with an error of at most ±(1 × 10^?5) g/cm³ for methanol mole fractions x ₂ of 0.06, 0.1, 0.3, or 0.6 and for the potassium bromide mole fractions up to about 2.65 × 10^?2 at 278.15, 288.15, 298.15, 308.15, and 318.15 K. Limiting partial molar volumes $\overline V _3^\infty $ , excess molar volumes $\overline V _3^{E, \infty } $ , and expansibilities $\overline E _{p, 3}^\infty $ have been calculated for a stoichiometric mixture of solvated K⁺ and Br^? ions in the mixed solvents. In the region of x ₂ ≈ 0.25, $\overline E _{p, 3}^\infty $ changes its sign from positive to negative. The $\overline V _3^{E, \infty } $ (x ₂) trend, on the whole, reflects the topologic features of the molecular structure of aqueous methanol associated through H-bonding.     

Volumetric properties of H2O, D2O, and methanol in acetonitrile at 278.15—318.15 K

The densities of H₂O, D₂O, and MeOH solutions in acetonitrile with the solute concentrations up to 0.07 molar fractions at 278.15, 288.15, 298.15, 308.15, and 318.15 K were measured using vibrating-tube densimetry with an error 8·10^–6 g cm^–3. The limiting partial molar volumes for the H/D isotopomers of water and IaII in acetonitrile (V^– ₂ ) and the isotope effects in V^– ₂ and in excess molar volumes of acetonitrile—water mixtures were calculated. Molecules of H₂O, D₂O, and IaII form associates with acetonitrile molecules via hydrogen bonds. The associates have the packing volumes close to those in the individual solute. The water and methanol molecules were assumed to be incorporated into the acetonitrile structure without substantial changes in the latter. However, this process results in some compression of the system with a simultaneous increase in its expansibility.     

The inflection point of the variation of interionic distance between Sm3+ and Cl− in a methanol and water mixture

The stability constants, β₁, of the monochloride complex of Sm(III) have been determined in mixed system of methanol and water at 1.00 mol dm⁻³ ionic strength using a solvent extraction technique. The values of β₁ increase with an increase in the mole fraction of methanol (X _s ) in the mixed solvent system when 0≤X _s ≤0.351. The interionic distance of Sm³⁺−Cl⁻ (d _Sm−Cl) in the mixed solvent system was estimated by applying the Gibb's free energy derived from β₁ to a Born-type equation. It was determined that an inflection point of the variation in the estimatedd _Sm−Cl againstX _s was present in the vicinity ofX _s =0.054. The inflection point ofd _Sm−Cl shows a value ofX _s between those ofd _Eu−Cl andd _Nd−Cl previously obtained by us.     

Structural and spectral consequences of ion pairing II. a theoretical study of CIO−3Li+ and ClO−3Na+

The structure of ClO⁻₃M⁺ ion pairs (M = Li, Na) has been examined with the aid of ab initio molecular orbital calculations. The calculations support recent experimental findings that ClO⁻₃ M ion paris have C_3v rather than C_s configurations. Results from these studies also show that the metal cation prefers to coordinate at the base of the chlorate anion pyramidal structure along the C₃ axis. Calculated vibrational frequencies, intensities, isotopic frequency shifts, and isotopic substituted frequency and intensity patterns render support to this conclusion. New vibrational assignments of observed and some unassignable bands from previous matrix-isolation and molten gas phase spectroscopic studies of ClO⁻₃M⁺ ion pairs are provided.     

Thermochemical investigations of the systems KCl−KBr−H2O,K2SO4−(NH4)2SO4−H2O and KNO3−NH4NO3−H2O at 298.15 K

For the equilibrium solid phases occurring in the systems: KCl?KBr?H₂O, K₂SO₄?(NH₄)₂SO₄?H₂O and KNO₃?NH₄NO₃?H₂O, the concentration dependencies of differential solution enthalpies, Δ_sol H ₂ for several crystallization paths, were measured. The limiting differential solution enthalpies, Δ_sol H ₂ ⁰ , were determined by extrapolation of the above dependencies to the ionic strength,I _m ⁰ , corresponding to the appropriate binary solutions. For KCl?KBr?H₂O system only, the clear dependence between Δ_sol H ₂ ⁰ andI _m ⁰ values was found and discussed.     

Dynamical competition between reactive and reactive detachment channels in X− + H2 colliding systems (X = Cl,Br, I)

Two reactive processes are observed: X⁻ + H₂ → XH + H⁻ (R) and X⁻ + H₂ → XH + H + e⁻ (RD). The angular and energy distributions of the molecular XH products are measured at collision energies varying from 5 to 10 eV center of mass. These distributions obey identical rules in the three systems: (a) XH molecules formed by both R and RD processes are scattered at the same c.m. angle, respectively 55° ±10 for ClH, 80° ±20 for BrH and 90° ±20 for IH. (b) The rovibrational energy of the XH molecules, when formed by R processes, is limited to a small amount: ⩽ 2 eV for ClH, ⩽ 1.5 eV for BrH, ⩽ 1 eV for IH, whereas when formed by RD it extends to the highest amount available from the collision energy, up to the dissociation limit. The RD process is not observed experimentally in the I⁻/H₂ system. This dynamical behaviour is fully understood in terms of non-adiabatic interaction between the two lowest [XH₂]⁻ ionic surfaces, but the reason of the angular anisotropy is still not well understood.     

Study of the process of the hydroxo complexes formation in the Al3+-Hg2+-NO 3 − -H2O and Al3+-Cd2+-NO 3 − -H2O systems

Russian Journal of Applied Chemistry - The process of hydrolysis in the Al3+-Cd2+-NO 3 ? -H2O and Al3+-Hg2+-NO 3 ? -H2O systems is studie by the methods of pH-metric titration and...     

Volumetric properties of aqueous solutions of sodium bromide at temperatures from 278.15 K to 338.15 K and molalities of (0.1, 0.5, and 1.0) mol · kg − 1

Densities of aqueous solutions of sodium bromide at the molalities (0.09855, 0.49997, and 1.0001)mol · kg ^− 1were determined at 1 K temperature intervals fromT =  278.15 K to T =  338.15 K. The densities were used in the evaluation of the apparent molar volumes, the cubic expansion coefficients, the apparent molar expansibilities and the second derivatives of the volume with respect to temperature. Properties of sodium bromide solutions which were determined in volumetric and calorimetric measurements are discussed and compared.     

Formation and thermodynamic properties of mixed complexes of Cd(II) with SCN2H4 and C−, Br−, I− as ligands

Thermodynamic parameters for in-water-formation of mononuclear complexes of cadmium-halide-thiourea systems, calculated by means of potentiometric measurements at different temperatures and at μ = 1 for KNO₃, are reported.     

Volumetric properties of aqueous solutions of lithium chloride at temperatures from 278.15 K to 338.15 K and molalities (0.1, 0.5, and 1.0)mol · kg − 1

Densities of aqueous solutions of lithium chloride at the molalities (0.1009, 0.4932, and 1.0009)mol · kg ^− 1were determined at 1 K temperature intervals fromT =  278.15 K to T =  338.15 K. The densities were used in the evaluation of the apparent molar volumes, cubic expansion coefficients, the apparent molar expansibilities and the second derivatives of the volume with respect to temperature. Properties of lithium chloride solutions which were determined in volumetric and calorimetric measurements are discussed and compared.     

Adsorption of Cd2+ and Cu2+ ions from aqueous solutions by a cross-linked polysulfonate–carboxylate resin

A new cross-linked polyzwitterion (CPZ) was synthesized through cyclocopolymerization of 3-[diallyl(carboxymethyl)ammonio]propane-1-sulfonate (92.5 mol%), and a cross-linker 1,1,4,4-tetraallylpiperazine-1,4-diium chloride (7.5 mol%) in the presence of tert-butylhydroperoxide. The cross-linked polyzwitterion/anion (CPZA) was obtained by the basification of CPZ with NaOH. The adsorption data fit both Temkin and Freundlich isotherm models. The adsorption trend on CPZA is as Cu²⁺ > Cd²⁺ and both followed pseudo-second-order kinetic model. The negative ΔG and positive ΔH values ascertained the spontaneous and endothermic nature of the adsorption process. The effectiveness of a zwitterionic–anionic motif consisting of quaternary nitrogen, sulfonate and carboxylate groups has been tested for the first time for capturing Cd²⁺ and Cu²⁺ ions at low concentrations.     

Calorimetric investigation of interactions in the LaNi4.75Al0.25−H2 and LaNi4.8Sn0.2−H2 systems

The interaction of hydrogen with intermetalic compounds LaNi_4.75Al_0.25 and LaNi_4.8Sn_0.2 has been studied in the temperature range 308–353 K by the calorimetry titration method. The mechanism of hydrogenation was investigated. It was shown that, as the temperature increases, the initial concentration of hydrogen in the metal lattice needed for β-hydride formation decreases. It was assumed that this effect is related to the concentration of H^δ+ atoms, which “oxidize” the metallic matrix according to the scheme H^δ++M⁰→H^δ−+M⁺. The enthalpy and entropy of hydrogenation for the LaNi_4.75Al_0.25−H₂ system were calculated from thep-C-T curves and the calorimetry results. The thermodynamic parameters of the LaNi_4.8Sn_0.2−H₂ system were obtained for the first time. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1841–1844, October, 1999.     

The enthalpies of interactions of Ca2+(aq) and C2O 4 2− (aq) ions in complexon solutions: Competition between complexation and precipitation

The thermal effects of mixing of aqueous calcium chloride with sodium citrate and ethylenedi-aminetetraacetate in the absence and presence of sodium oxalate have been measured at 25°C. The thermal effects of dilution of aqueous calcium chloride solutions were determined. The thermal effects of calcium oxalate precipitation and formation of calcium complexes with citrate and ethylenediaminetetraacetate ions were calculated. The 1% solution of sodium citrate inhibited the formation of CaC₂O₄ (s); in a 1% solution of sodium ethylenediaminetetraacetate with [Ca²⁺][C₂O ₄ ^2? ] > 10^?5, the endothermal formation of the [CaEdta]^2? complex quickly changed to exothermal precipitation. The 3 and 5% solutions of complexons showed a pronounced inhibiting effect on the formation of urinary stones even when the concentration of calcium and oxalate ions in solution exceeded the product of solubility of CaC₂O₄ by four and more orders of magnitude.     

Vibrational behavior of matrix-isolated ions in Tutton compounds. V. Infrared spectroscopic study of NH4+ and SO42− ions included in zinc sulfates and selenates

Infrared spectra of K₂Zn(SeO₄)₂·6H₂O and (NH₄)₂Zn(SeO₄)₂·6H₂O containing SO₄^2? guest ions and those of K₂Zn(SO₄)₂·6H₂O and K₂Zn(SeO₄)₂·6H₂O containing NH₄⁺ guest ions are presented and discussed in the region of the stretching modes ν₃ and ν₁ of the sulfate ions and in the region of asymmetric bending modes ν₄ of the NH₄⁺ ions, respectively. The SO₄^2? ions matrix-isolated in the selenate matrices (approximately 2 mol%) exhibit three bands for ν₃ and one band for ν₁ in agreement with the low site symmetry C₁ of the selenate host ions. The NH₄⁺ guest ions included in the potassium sulfate matrix are characterized also with three site symmetry components of ν₄. However, the ammonium ions in (NH₄)₂Zn(SeO₄)₂·6H₂O as well as those included in K₂Zn(SeO₄)₂·6H₂O display four infrared bands corresponding to ν₄ probably due to some kind of disorder of the ammonium ions. The extent of energetic distortion of the isomorphously included sulfate ions as deduced from the values of Δν₃ (site-group splitting) and Δν_max (the difference between the highest and the lowest wavenumbered components of the stretching modes) are commented. The spectroscopic experiments reveal that the SO₄^2? guest ions are weaker distorted in the potassium selenate matrix than the same ions in the neat potassium sulfate due to the larger unit-cell volumes of the selenate compounds. However, the SO₄^2? guest ions are stronger distorted in the ammonium selenate matrix as compared to the same ions in the neat ammonium sulfate owing to the formation of hydrogen bonds between the SO₄^2? guest ions and the NH₄⁺ host ions. The analysis of the spectra shows that the band positions of the water librations in the host potassium compounds are affected by the included ammonium cations. The formation of the hydrogen bonds between the NH₄⁺ guest ions and the XO₄^2? host ions leads to a decrease in the proton acceptor capabilities of the anions (anti-cooperative or proton acceptor competitive effect) and as a result the hydrogen bonds formed by the water molecules weaken on going from the neat potassium compounds to the mixed crystals K_1.8(NH₄)_0.2Zn(SO₄)₂·6H₂O and K_1.8(NH₄)_0.2Zn(SeO₄)₂·6H₂O (the bands corresponding to water librations are broadened and shifted to lower frequencies).     

Synthesis and thermoelectric properties of Sr0.95La0.05TiO3−δ-TiO2 solid solutions

Sr_0.95La_0.05TiO_3?δ solid solutions, combined with 10 mol% TiO₂, were prepared at different temperatures. When sintered at a suitable temperature, the Seebeck coefficient presents the same behavior at high temperatures as that of Sr_0.95La_0.05TiO_3?δ ceramic. Otherwise, the Seebeck coefficient would be smaller. After introducing TiO₂, both of the thermal and electrical conductivity are reduced. The sample sintered at 1350 °C exhibits the highest ZT of about 0.2, which slightly larger than that of Sr_0.95La_0.05TiO_3?δ ceramic.