Sorption and Diffusion of SF6 in Silicalite Crystals

Kinetic and equilibrium data for sorption of SF₆ in silicalite have been determined by the ZLC method. The equilibrium constants and adsorption energy are comparable with the values reported previously for SF₆-NaX. Intracrystalline diffusion is relatively rapid with diffusivities of order 10_–7– 10^–8 cm²·s^–1 at temperatures in the range 30–90°C. The implications for the use of SF₆ as a probe molecule for assessing the integrity of silicalite membranes are considered.     

Experimentelle Bestimmung der Gleichgewichtslagen im System NaCl(l)-KCl(l)-Na(l)-K(l)

Zusammenfassung Ausgehend von nahezu äquivalenten Mengen an Na und KCl werden die Gleichgewichtszusammensetzungen der metallreichen und der salzreichen Phase des Systems NaCl–KCl–Na–K im Bereich von 1140 bis 1240° K ermittelt. Die Gleichgewichtskonzentrationen der Komponenten werden zur Berechnung der GleichgewichtskonstantenK _x in beiden Phasen herangezogen.

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The equilibrium compositions of both metal-rich and salt-rich phases of the system NaCl–KCl–Na–K are investigated in the temperature range from 1140 to 1240° K, starting from nearly equivalent amounts of Na and KCl. From the experimentally determined concentrations the equilibrium constantsK _x were calculated.

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Mit 1 Abbildung     

Equilibrium acidity of potassium (3)−1,2-dicarbadodecahyronidoundecaborate (−1)

Conclusion The equilibrium acidity of potassium dicarbadodecahydronidoundecaborate(–1) when metalated with fluorenylpotassium and indenylpotassium in 1,2-dimethoxyethane was determined, and was found to have a pK _a value of 21.1–21.5 on the Streitwieser scale.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 471–472, February, 1972.     

Solubility of Crystalline Calcium Isosaccharinate

The solubility of calcium isosaccharinate Ca(ISA)₂(c) was determined at 23°C as a function of pH (1–14) and calcium ion molality (0.03–0.52). The similarity of solubility from the over- and undersaturation directions for different equilibration periods indicated that equilibrium in these solutions was reached rapidly (< 7 days) and that these data can be used to develop thermodynamic equilibrium constants. The solubility data were interpreted using the Pitzer ion–interaction model. The logarithms of the thermodynamic equilibrium constants determined from these data were 1.30 for the dominant reaction at pH < 4.5 [Ca(ISA)₂(c) + 2H⁺ Ca²⁺ + 2HISA(aq)], and –2.22 for the dominant reaction at 4.5 [Ca(ISA)₂(c)+ Ca(ISA)₂(aq)]. In addition, the logarithm of the dissociation constant of HISA [HISA(aq) ISA- + H⁺] was calculated to be –4.46.     

New Procedure for Determining the Solubility of Lypophilic Nonionic Surfactants in Water

The procedure that allows to study the kinetics of a dissolution of oleophilic nonionic surfactants in water and to determine the equilibrium values of solubility (S ^eq _w) was proposed, based on the spectrophotometry of extremely dilute, finely dispersed o/w emulsions of these substances prepared by sonication. The equilibrium values of solubility of tetraethoxylated p-nonylphenol (Neonol AF_9-4) and sorbitan monolaurate (Span-20) at 293 K in water are 3.67 × 10^–5 and 1.03 × 10^–5 M, respectively. For the tetraethoxylated p-nonylphenol, the equilibrium value of solubility in water determined by the proposed procedure agrees well with that determined by precision tensiometric measurements.     

Triiodide ion formation equilibrium and activity coefficients in aqueous solution

The equilibrium quotient for the formation of triiodide was studied as a function of temperature, 3.8–209.0°C, and ionic strength, 0.02–6.61. The best-fit value for the molal equilibrium constant at 25°C is 698±10 and the corresponding partial molal enthalphy, entropy, and heat capacity of formation are: H^o=–17.0±0.6 kJ-mol^–1, S^o=–0.6±0.3 J-K^–1-mol^–1, and C _p ^o =–21±8 J-K^–1-mol^–1. Activity coefficients of iodine were determined as a function of ionic strength (NaClO₄) at 25°C and conclusions are drawn as to the corresponding ionic strength dependence of the triiodide anion.     

Paramagnetic complexes of nickel(I) stabilized by norbornadiene

Nickel(I) compounds whose concentration was 10^–4–10^–6 of the total concentration of nickel added to the system were identified by EPR in the reaction of 2,5-norbornadiene with nickel homoligand allyl complexes Niall₂ (all is C₃H₅, 1-CH₃C₃H₄, or 2-CH₃C₃H₄). The Ni(I) complexes were stable at room temperature under oxygen-free conditions. It was shown that the paramagnetic complexes were in equilibrium with diamagnetic forms. The temperature dependence of the concentration of the paramagnetic species was determined. The structure of the paramagnetic nickel(I) complexes and the possible routes of their formation are discussed on the basis of the obtained data.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 490–493, July–August, 1990.     

Synergistic extraction behavior of samarium(III), europium(III) and dysprosium(III) with 1-nitroso-2-naphthol and 1,10-phenanthroline

The equilibrium extraction behavior of Sm(III), Eu(III) and Dy(III) from aqueous NaClO₄ solutions in the pH range of 4–9 at 0.1 M ionic strength into organic solutions of 1-nitroso-2-naphthol (HA) and 1,10-phenanthroline (Phen) has been studied. The equilibrium concentrations of Eu were assayed through the 344 keV photopeak of the¹⁵²Eu radiotracer used. The concentrations of Sm and Dy were measured by irradiating one mL portions of the organic extract and analyzing the 104 and 108 keV photopeaks of the short-lived neutron activation products,¹⁵⁵Sm and^165mDy, respectively. Quantitative extraction of Eu with 5×10^–2 M HA alone was obtained in the pH range of 6.7–7.8 with n-butanol, 7.4–8.5 with chloroform, 8.0–8.7 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.1–8.0 with methyl isobutyl ketone (MIBK). But, Eu was extracted only to a maximum of 78% and 83% in the pH range of 8.3–8.9 and 7.4–8.1 with carbon tetrachloride and xylene, respectively. The extraction of Sm and Dy were found quantitative in the pH range of 6.3–7.0 and 6.6–7.1, respectively, with 5×10^–2 M HA alone in MIBK solutions. The synergistic extraction of Eu was quantitative in the pH range of 6.6–9.8 with chloroform, 7.8–8.9 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.0–9.6 with MIBK when 1×10^–2 M each of HA and Phen were employed. Sm and Dy were quantitatively extracted into MIBK solutions containing 5×10^–2 M each of HA and Phen in the pH range 6.0–7.5 and 6.1–7.5, respectively. The distribution ratios of these lanthanides (Ln) were determined as a function of pH, and HA and Phen concentrations. The analysis of the data suggests that these Ln are extracted as LnA₃ chelates when HA alone is used. In the presence of HA and Phen, both LnA₃(Phen) and LnA₃(Phen)₂ adducts are formed only in the MIBK system while LnA₃(Phen) complexes are the predominant ones in all other solvent systems studied. The extraction constants and the adduct formation constants of these complexes have been calculated.     

Mixed chloro-bromo complexes of ruthenium(IV)

Conclusions Using spectrophotometry the authors have investigated complexing in the system Ru(IV)-Cl^–-Br^–. They have identified the formation of mixed-ligand chloro-bromo complexes of Ru(IV) and determined the equilibrium constants of reactions of formation of the complexes [Ru₂OCl₇Br-(H₂O)₂]^2– and [Ru₂OBr₇Cl(H₂O)₂]^2–.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2186–2190, October, 1977.     

Chloro Complexes of Mercury(II) in Aqueous Perchlorate Media: Equilibrium and Electronic Absorption Spectra

The literature data on the equilibrium constants of formation of HgCl^– _{3 solv} and HgCl^2– _{4 solv} from HgCl_{2 solv} and Cl^– _solv in aqueous perchlorate–chloride solutions were generalized. The individual electronic absorption spectrum of the trichloro complex of mercury(II) was obtained for the first time, and the effect of the ionic strength on the spectra of di-, tri-, and tetrachloro complexes of mercury(II) was considered. The previously developed procedures for the resolution of absorption spectra into individual bands were found to be suitable for interpretation of spectral changes experimentally observed for solutions as the result of stepwise complexation. The parameters of the absorption bands in the spectra of chloro complexes of mercury(II) were determined.     

Potentiometric studies of the thermodynamics of iodine disproportionation from 4 to 209°C

The equilibrium constant for the disproportionation of iodine in aqueous solution was determined as a function of temperature from 3.8 to 209.0°C using emf measurements in low ionic strength media. The equilibrium constant and associated molal thermodynamic quantities at 25°C are: K₁=1.17±0.62×10^–47, H^o=273±3 kJ-mol^–1, S^o=16±9 J-K^–1-mol^–1, and C _p ^o =–1802±41 J-K^–1-mol^–1. Although the value of K₁ is in excellent agreement with a previous emf measurement at 25°C, these results conflict with the corresponding parameters obtained from the NBS tables. Moreover, at temperatures above ca. 100°C, our measured values for the equilibrium constant diverge strongly from all previous estimates and predictions.     

Vapor–liquid equilibria and interfacial tensions for the ternary system acetone + 2,2′-oxybis[propane] + cyclohexane and its constituent binary systems

Isobaric vapor–liquid equilibrium data have been measured for the ternary system acetone + 2,2′-oxybis[propane] + cyclohexane, and its constituent binaries at 94 kPa and in the temperature range 324–350 K in a vapor–liquid equilibrium still with circulation of both phases. The dependence of the interfacial tensions of these mixtures on concentration was also determined at atmospheric pressure and 303.15 K, using the maximum bubble pressure technique.From the experimental results, it follows that both the ternary and binary mixtures exhibit positive deviations from ideal behavior and, additionally, azeotropy is present for the binaries that contain acetone. The application of a model-free approach allows conclusions about the reliability of the present vapor–liquid equilibrium data for all the indicated mixtures. Furthermore, the determined interfacial tensions exhibit negative deviation from linear behavior for all the analyzed mixtures, and aneotropy is observed for the acetone + cyclohexane mixture.The vapor–liquid equilibrium data of the binary mixtures were well correlated using the NRTL, Wilson and UNIQUAC equations. In a similar manner, the interfacial tensions of the binary mixtures were smoothed using the Redlich–Kister equation. Scaling of these models to the ternary mixture allows concluding that both the vapor–liquid equilibrium data and the interfacial tensions can be reasonably predicted from binary contributions.     

Characterization of the molecular species formed by interaction of acetonitrile and copper(I) chloride in the liquid and solid phase

Summary The equilibrium vapour pressure of the solid complex, CuCl·MeCN, was measured at several temperatures. The enthalpy and entropy changes according to the following complex formation were determined: CuCl(s)+ MeCN(g)CuCl·MeCN(s); H=–56.9 kJ mol^–1 and S=–150 J mol^–1 K ^–1, respectively. Vapour pressure osmometry shows that a monomer-dimer equilibrium of CuCl exists in the acetonitrile solution. The equilibrium constant was found to be 0.93±0.08. A gas chromatographic technique was employed to determine the monomeric species as [Cu(MeCN)₄]Cl.     

Specific features of the thermodynamics of activation in the LaNi<Subscript>5</Subscript>-H<Subscript>2</Subscript> and CeNi<Subscript>5</Subscript>-H<Subscript>2</Subscript> systems

Using heat conducting Tian—Calvet calorimetry and volumetric measurements, the first hydrogen absorption—desorption cycles in the LaNi₅-H₂ and CeNi₅-H₂ systems were studied. The pressure—composition isotherms were plotted, the equilibrium pressures of hydrogen along the absorption and desorption branches and in the region of hysteresis for different activation steps were determined, and the enthalpies of phase transitions α → β and β → α were calculated. The profiles of the heat evolution curves were analyzed. It was concluded that the mechanism of the reactions studied changes upon activation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 134–139, January, 2005.     

Acid Catalysis in Reaction of Ozone with Chloride Ions

The kinetics of the interaction of ozone with aqueous solutions of chlorides resulting in Cl₂ evolution to the gas phase was studied. The reaction of O₃ with Cl^– is accelerated by H⁺ ions. The effects of the concentrations of H⁺ and Cl^–, the ionic strength, and temperature (ranged from 7 to 60°C) on the reaction rate were studied. A mechanism explaining the experimental kinetics was proposed. The acid catalysis is due to the formation of the HO₃Cl complex, which is in equilibrium with H⁺, O₃, and Cl^–. The constants of reactions involved in the proposed mechanism were determined.     

Acoustic absorption in aqueous potassium phosphate

Measurements of acoustic absorption and velocity as a function of frequency and concentration in KH₂PO₄–K₂HPO₄ buffers at 4°C and pH 5-7 are reported. The dependence of the observed acoustic relaxation parameters on concentration is consistent with that to be expected from perturbation of a monomer-dimer equilibrium with an equilibrium constant [for 2H₂PO ₄ ^– (H₂PO₄)₂ ^2–] of 0.21 M^–1, a bimolecular rate constant of 5×10⁸ M^–1-sec^–1 and a standard volume change of –5 cm³ mole. The equilibrium constant for H₂PO ₄ ^– + HPO₄ ^2–H₃(PO₄)₂ ^3– is estimated to be 0.7 M^–1.     

Complexation of Cu(II) with <Emphasis Type="SmallCaps">L</Emphasis>- and <Emphasis Type="SmallCaps">DL</Emphasis>-threonine: An ESR study

Complexation of Cu(II) ions with L- and DL-threonine in aqueous solution was studied. Treatment of the ESR spectra of solutions containing Cu(II) and threonine in various ratios and having various pH, involving total line shape analysis, revealed formation of geometric isomers of the complex ions [Cu(thrH_–1)₂]^2– differing in the mutual arrangement of the N and O atoms in the equatorial plane; the complexation and isomerization equilibrium constants were determined.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1388–1391.Original Russian Text Copyright © 2004 by Statsenko, Bolotin, Panyushkin.This revised version was published online in April 2005 with a corrected cover date.     

Raman and Infrared Spectra, Ab Initio Calculations, Normal Coordinate Analysis, and Conformational Stability of 2-Methoxypropene

The Raman (3500–40 cm^–1) and infrared (3500–70 cm^–1) spectra of gaseous and solid 2-methoxypropene, CH₃O(CH₃)C=CH₂, and the isotopomers, CD₃O(CH₃)C=CH₂ and CH₃O(CD₃)C=CD₂ have been recorded. In addition, the Raman spectra of the liquids have been recorded with qualitative depolarization measurements. All of these data indicate that only one conformer is present in the fluid phases at ambient temperature and this form is the cis conformer, which remains in the solid. Assignments are provided for the fundamentals of all three isotopomers for the cis conformer with C_s symmetry. The far-infrared spectra of all three isotopic species have been recorded at a resolution of 0.1 cm^–1 in the gas and 1.0 cm^–1 in the solid. The parameters of the potential function governing the asymmetric torsion are determined to be V₃ = 1485 ± 9 cm^–1 and V₆ = –55 ± 4 cm^–1 for the d₀ compound, where only two terms were determined, since a second conformer was not evident. The barrier to internal rotation for the methyl group attached to the oxygen atom is 1370 ± 8 cm^–1 and the C—CH₃ barrier is 772 ± 5 cm^–1. Ab initio calculations with full electron correlation have been carried out by the perturbation method to second order to obtain the equilibrium structural parameters, harmonic force constants, fundamental frequencies, infrared intensities, Raman activities, depolarization values, and conformational stability. The predicted values have been compared to the experimental values where appropriate.     

Kinetics of reduction of hydroxycuprate(III) in KOH solution

The solution of an unstable copper(III) complex, hydroxycuprate(III) i.e. Cu(OH)^– ₄, has been obtained by oxidising a copper anode in 0.5–3 M KOH solution. The kinetics of the copper(III) reduction in KOH solution has been studied spectrophotometrically and is first order with respect to copper(III), and the pseudo-first order rate constant increases as the KOH concentration increases. The kinetic data is explained by a scheme according to which a Cu^III intermediate, in equilibrium with Cu(OH)^– ₄, reacts with OH^–. On the basis of the kinetic data, the molar absorptivity of the Cu(OH)^– ₄ solution has been determined.     

Complexation processes in KF-SbF<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system studied by calorimetric titration

Complexation in a KF-SbF₃-H₂O system is studied in a range of molar ratios of fluorides KF : SbF₃= (0.1–2) : 1 by calorimetric titration. The equilibrium formation constants of complexes KSb₂F₇, KSbF₄, and K₂SbF₅ (5.8×10⁵±800, 3.3×10⁴±500, and 1.9×10⁶± 950, respectively) and the changes in enthalpy (–31.75± 0.74, –28.15±0.44, and –25.5±0.64 J mol^–1, respectively) and entropy (4±7, –8±5, and –35±9 J mol^–1 K^–1, respectively) are determined. The thermodynamic stability of the antimony(III) fluoride complexes is found to increase on going from KSb₂F₇ to K₂SbF₅.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 168–171.Original Russian Text Copyright © 2005 by Kovaleva, Zemnukhova, Lebedeva, Fedorishcheva.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.