Properties of Interface between Platinum Sponge and Solid Electrolyte Na5TbSi4O12in an Oxygen Atmosphere at Moderate Temperatures: Effect of the Platinum Grain Size

The behavior of electrochemical cells Pt(sponge)/Na₅TbSi₄₁₂/Na_0.65Co₂(cell I) and Pt(sponge)/Na₅TbSi₄₁₂/Pt(sponge) (cell II) is studied by, respectively, potentiometric and impedance methods in oxygen and argon atmospheres at 50–300°C. Dependence of potential of cell I on the oxygen concentration is affected by the grain size of platinum sponge and the temperature. At 50–200°C the coarse-grained platinum electrode in contact with solid electrolyte Na₅TbSi₄₁₂ exhibits an oxygen function characterized by the potential-determining reaction ₂(g) + ₂ + 2 = ^– ₂ + ^–. An impedance method shows the triple-phase boundary ₂, Pt(sponge)/Na₅TbSi₄₁₂ to be reversible with respect to oxygen. The reversibility is realized by minority charge carriers in the solid electrolyte, i.e. by oxygen ions.     

Withasteroids ofPhysalis VI.1H and13C NMR spectra of withasteroids ixocarpalactone A and ixocarpanolide

The¹H and¹³C NMR spectra of two withasteroids isolated fromPhysalis ixocarpa Brot. have been studied in detail. Their spectral characteristics are discussed. A comparison of the results obtained has led to the identification of a withasteroid with the composition C₂₈H₄₀O₈, mp 291–292°C (from methanol) as ixocarpalactone A, in spite of some difference in its physical constants. The other compound, with mp 252–253°C (from methanol), had the composition C₂₈H₄₀O₆, [] _D ²⁰ +27±4°, is new and has been called ixocarpanolide. The structure of 5,20R-dihydroxy-1-oxo-6, 7-epoxy-22R-witha-2-enolide has been proposed for it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 326–332, May–June, 1986.     

The Deposition of Aerosol Submicron Particles on Ultrafine Fiber Filters

The diffusion deposition of submicron aerosol particles of a finite size on a model filter composed of parallel ultrafine fibers with a radius comparable with the mean free path of air molecules was considered. The diffusion capture coefficient with allowance made for particle interception _DR is found by the numerical solution of the elliptic equation of steady-state convective diffusion in the wide ranges of interception parameter R, Peclet (Pe) and Knudsen (Kn) numbers at small Reynolds numbers. It was shown that, at small Kn numbers, the _DR value exceeds the sum of capture coefficients due to specific deposition mechanisms, interception and diffusion, = _R + _D , whereas, at Kn > 1, _DR . Within the range of intermediate Pe, Kn, and R numbers, the radius of the most penetrating particles is higher than the fiber radius.     

Infrared Spectroscopy Analysis of Oxyhydroxides as Intermediate Species in the Formation of Iron Oxides-Silica Xerogels

A detailed infrared spectroscopy analysis in the 2500 to 3800 cm^–1 region has been used to study the formation of species in samples of iron oxides embedded in silica xerogel matrix. We report the presence of , , and forms of iron oxyhydroxides as intermediate species in the formation of -Fe₂O₃, -Fe₂O₃ and -Fe₂O₃ starting from three different iron precursors: iron nitrate, iron chloride and nanometric Fe particles prepared by chemical reduction. Our results show that under thermal dehydration and forms of iron oxyhydroxides transform into hematite and maghemite, respectively, whereas the form transform to the -Fe₂O₃ without going through an intermediate iron oxide phase.     

Growth,Structure, and Electrophysical Properties of Single Crystals of A2TiGeO5 (A = Li and Na)

Crystals of Li₂TiGeO₅ were obtained by solution-melt crystallization, and those of Na₂TiGeO₅ were grown from a melt by pulling. The crystals are isostructural with the natisite mineral Na₂TiSiO₅. The crystal structure of Li₂{TiOGeO₄} was refined by X-ray diffraction analysis (a four-circle diffractometer, 2/ scan mode, MoK radiation, _max = 50°). The unit cell parameters are a = 6.614(4) Å and c = 4.435(4) Å; space group P4/nmm, Z = 2, _calcd = 3.67 g/cm³, R = 0.031, s = 1.128, wR(F ²) = 0.071 (548 reflections with I 2I). The ionic conduction in both crystals was found to be anisotropic in the temperature range 250–600°C;. At 400°C;, the conductivity values are 10^–4 to 10^–5 S/cm along the a axis and 10^–6 to 10^–8 (for Na₂TiGeO₅) and 10^–7 to 10^–9 S/cm (for Li₂TiGeO₅) along the c axis.     

The annealing of radical species in γ-irradiated cesium nitrate

The kinetics of thermal annealing of radical species /equivalent nitrite (NO ₂ ^– )', NO ₂ ^– and their difference, (NO ₂ ^– )/ in -irradiated CsNO₃ has been investigated. The data have been nalyzed on the basis of models for vacancy interstititial combination and also on the basis of conventional chemical kinetics.     

Synthesis of heterocycles on the basis of products of addition of polyhaloalkanes to unsaturated systems.

Oximes of 3,3-dichloropropenal and 4,4,4-trifluoro-3-chloro-1-butenal were obtained on the basis of products of free-radical addition of CCl₄ and CF₃CCl₃ to vinyl butyl ether. Generation of the corresponding nitrile oxides from these oximes and reaction of the nitrile oxides in situ with vinyl butyl ether, phenylacetylene, and propargyl alcohol via the scheme of 1,3-dipolar cycloaddition are proposed as a method for the synthesis of isoxazoles containing ,-dichlorovinyl and -trifluoromethyl--chlorovinyl substituents in the 3 position.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1250–1255, September, 1990.     

Hartree-Fock-Roothaan wave functions,electron density distribution,diamagnetic susceptibility,dipole polarizability and antishielding factor for ions in crystals

Using the Hartree-Fock method the wave functions of Li⁺, Be²⁺, O^2–, F^–, Na⁺, Mg²⁺, Al³⁺, S^2–, Cl^–, K⁺, Ca²⁺, Sc³⁺ and Ti⁴⁺ have been calculated for the free ion and the ion in a potential well. The main result of these calculations is a contraction of the anion and an expansion of the cation due to the external potential. A comparison of the calculations with an experimental determination of the electron density distribution in NaCl and MgO shows qualitative agreement. The diamagnetic susceptibility , the dipole polarizability _d, and the Sternheimer antishielding factor of the ions given above were also calculated for the free ions and the spherical potential ions (SPI). The charged hollow sphere model improves the theoretical values towards the properties determined by experiment.

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Zusammenfassung Unter Verwendung der Hartree-Fock-Methode wurden analytische Wellenfunktionen für die Ionen Li⁺, Be²⁺, O^2–, F^–, Na⁺, Mg²⁺, Al³⁺, S^2–, Cl^–, K⁺, Ca²⁺, Sc³⁺ und Ti⁴⁺ berechnet. Es wurden sowohl die freien Ionen als auch Ionen im Potentialtopf untersucht. Es zeigt sich eine durch das äußere Potential hervorgerufene Kontraktion der Anionen und eine Expansion der Kationen. Der Vergleich der Rechnungen mit experimentellen Bestimmungen der Elektronendichteverteilung in NaCl und MgO zeigt qualitative Übereinstimmung zwischen Theorie und Experiment. Ferner wurden die diamagnetische Suszeptibilität , die Dipolpolarisierbarkeit _d und der Antishieldingfaktor (Sternheimerfaktor) sowohl für die freien als auch für die durch ein kugelsymmetrisches Potential gestörten Ionen berechnet. Das hier benutzte Festkörpermodell der geladenen Hohlkugel ergibt Werte, die in guter Übereinstimmung mit dem Experiment sind.

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Résumé Les fonctions d'onde de Li⁺, Be²⁺, O^2–, F^–, Na⁺, Mg²⁺, Al³⁺, S^2–, Cl^–, K⁺, Ca²⁺, Sc³⁺ et Ti⁴⁺ ont été calculées par la méthode de Hartree-Fock pour l'ion libre et pour l'ion dans un puit de potentiel. Le résultat essentiel de ces calculs montre une contraction de l'anion et une expansion du cation sous l'effet du potentiel extérieur. Les densités électroniques calculées et celles obtenues expérimentalement dans NaCl et MgO sont en accord qualitatif. La susceptibilité diamagnétique , la polarisabilité dipolaire _d, et le facteur anti-écran de Sterneimer des ions ci-dessus ont été calculés pour les ions libres et pour les ions à «potentiel sphérique» (SPI). Le modèle de la sphère creuse chargée améliore les valeurs théoriques par rapport aux données expérimentales.

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D 17 (E. Paschalis, 1967).     

Übergangsmetall-Chalkogensysteme, 3. Mitt.: Das System Nickel-Tellur

Zusammenfassung Auf Grund thermischer und röntgenographischer Unter-suchungen wurde das vollständige Phasendiagramm Ni–Te aufgestellt. Die Anlage für die thermische Analyse wurde teilweise automatisiert, so daß ausgewählte Temperaturintervalle mit einstellbaren Heiz- udn Kühlgeschwindigkeiten periodisch durchlaufen werden konnten. Zwischen Ni und der kub. f. z. Hochtemperaturphase ₁ (Ni_3±x Te₂) liegt ein Eutektikum bei 34 At% Te und 1004,5°C. ₁ schmilzt kongruent bei 38 At% Te und 1021,5°C und hat eine maximale Phasenbreite von 37 At% Te (1004,5°C) bis 43,5 At% Te (880°C). Nickelreiches ₁ wandelt sich zwischen 796 und 789°C in eine Ordnungsphase ₁ um, die bei 37,7 At% Te und 731°C eutektoidisch in Ni und ₂ zerfällt. ₁ und ₁ wandeln sich unterhalb bei 790°C in die tetragonale ₂-Phase um, deren maximaler Homogenitätsbereich von 38,8 At% Te (731°C) bis 41 At% Te (775°C) reicht. Bei 42,5 At% Te und 775°C zerfällt ₁ eutektoidisch in ₂ und ₂. Die ₂-Phase (NiTe_0,85) bildet sich peritektisch bei 880°C und zerfällt bei 690°C nach _{2 1} + . Orthorhombisches ₁ disproportioniert sich peritektoidisch bei 742,5°C in ₂ und ₂. ₂ bildet bei 873°C und 49,5 At% Te ein Eutektikum mit der -Phase vom NiAs-Typ. hat einen kongruenten Schmelzpunkt von 900,5°C bei 56 At% Te und eine maximale Phasenbreite von 52 At% Te (690°C) bis 66,6 At% Te (448,5°C). Mit Te bildet die -Phase ein entartetes Eutektikum bei 448,5°C. Die Phasen ₂, ₁ und wurden röntgenographisch verifiziert und die Abhängigkeit der Gitterparameter der -Phase von der Konzentration vermessen.

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Transition metal-chalcogene systems, III: The system Ni–Te

Based on thermal and X-ray measurements the complete Ni–Te phase diagram was constructed. The equipment for thermal analysis was partially automated so that selected temperature intervals could be periodically scanned by programmed heating and cooling rates. Between Ni and thefcc high temperature phase ₁ (Ni_3±x Te₂) a eutectic exists at 34 at% Te and 1004.5°C. ₁ melts congruently at 38 at% Te and 1004.5°C, and has a maximum phase width from 37 at% Te (1004.5°C) to 43.5 at% Te (880°C). Nickel-rich ₁ transforms between 796 and 789°C into an ordered phase ₁ which decomposes eutectoidally into Ni and ₂ at 37.7 at% Te and 731°C. ₁ and ₁ transform at temperatures below 790°C into the tetragonal ₂-phase which has a maximum range of homogeneity from 38.8 at% Te (731°C) to 41 at% Te (775°C). At 42.5 at% Te and 775°C ₁ decomposes eutectoidally into ₂ and ₂. The ₂-phase (NiTe_0.85) is formed by the peritectic reactionL + _{1 2} at 880°C and decomposes at 690°C according to _{2 1} + . Orthorhombic ₁ disproportionates peritectoidally at 742.5°C into ₂ and ₂. ₂ forms at 873°C and 49.5 at% Te a eutectic with the -phase of the NiAs-type. has a congruent melting point of 900.5°C at 56 at% Te and a maximum phase width from 52 at% Te (690°C) to 66.6 at% Te (448.5°C). Te and the -phase form a degenerate eutectic at 448.5°C. The phases ₂, ₁, and were verified by X-ray diffraction and the lattice parameters of the -phase were determined as a function of concentration.

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Mit 2 Abbildungen     

The effects of cyclodextrin inclusion of the ferrocenemonocarboxylate anion on the kinetics of its oxidation by bis(pyridine-2,6-dicarboxylato)cobaltate(III) in aqueous solution

The effects of -, -, dm-(heptakis(2,6-di-O-methyl)--) and -cyclodextrins (CD) on the kinetics of the electron-transfer reaction of the ferrocenemonocarboxylate anion (FCA^–) with bis(pyridine-2,6-dicarboxylato)cobaltate(III) have been investigated in aqueous solution (0.20 M Na₂HPO₄, pH 9.2) at 25.0°C. Substantial decreases in the rate constants for the electron-transfer reactions were observed upon cyclodextrin inclusion of the reductant, due to an increase in the FCA^0/– reduction potential and to the insulation of the reductant from oxidant. The inclusion stability constants for {FCA·CD}^– were evaluated from the¹H NMR and kinetic data, and the order of the stability constants was found to be -CDdm-CD-CD>-CD.     

Chemical and x-ray structural investigation of a new diterpene lactone betolide

A crystalline substance with the composition C₂₀H₂₄O₅ has been isolated from the roots of common betony. The spatial structure of this new diterpene lactone, betolide, has been established from the results of UV, IR, NMR, and¹³C NMR spectral and x-ray structural investigations — 13-formyl-14-hydroxy-(2-hydroxy-5-oxotetrahydrofuro) [3,4:11,12]-^8,10,12-podocarpane, the first representative of new tetracyclic diterpenes the lactone ring of which is formed with the participation of a hydroxyl of a geminal diol. The stability of a lactone ring of this type and a high reactivity of the semiacetal hydroxyl have been shown.Institute of Chemical Sciences, Kazakhstan SSR Academy of Sciences, Alma-Ata. Division of the Institute of Chemical Physics, USSR Academy of Sciences, Chernogolovka. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 811–817, November–December, 1987.     

Elucidation of hydrodesulfurization mechanism on molybdenum‐based catalysts using 35S radioisotope pulse tracer methods

Elucidation of the hydrodesulfurization (HDS) mechanism on molybdenumbased catalysts using radioisotope tracer methods and reaction kinetics is reviewed. Firstly, to investigate the sulfidation state in Mo/Al₂O₃ and Co–Mo/Al₂O₃ catalysts, presulfiding of these catalysts has been performed using a ³⁵S pulse tracer method. Secondly, HDS of radioactive ³⁵Slabeled dibenzothiophene was carried out over a series of sulfided molybdena–alumina catalysts and cobaltpromoted molybdena–alumina catalysts in a pressurized flow reactor to estimate the behavior of sulfur on the working catalysts. Finally, sulfur exchange of a ³⁵Slabeled catalyst with hydrogen sulfide was performed to estimate the relationship between the amount of labile sulfur and catalytically active sites.     

Ammoxidation of 3- and 4-picolines over V2O5?SnO2/γ?Al2O3 catalyst

The ammoxidation of 3- and 4-picolines has been studied over V₂O₅–SnO₂/–Al₂O₃ catalysts prepared by surface impregnation technique. Best results were obtained for the generation of cyanopyridines in the temperature range 400–450°C and sub-stoichiometric value with respect to O₂. Catalysts that were calcined above 700°C showed no activity.

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3- 4- V₂O₅–SnO₂/–Al₂O₃, . 400–450°C O₂. , 700 K, .

     

Apparent molal heat capacities and volumes of pyridine and methyl-substituted pyridines in aqueous solution at 25°C

We have made calorimetric measurements leading to apparent molal heat capacities of pyridine and four methyl-substituted pyridines in aqueous solution at 25.0°C. Measurements of densities of the same solutions have led to apparent molal volumes. The results are as follows: pyridine, _C ^° = 305.7 J–°K^–1-mole^–1 and _V ^° = 77.5 cm³-mole^–1; 2-methylpyridine, _C ^° = 370.0 J–°K^–1-mole^–1 and _V ^° = 94.3 cm³-mole^–1; 3-methylpyridine, _C ^° = 380.2 J–°K^–1-mole^–1 and _V ^° = 93.7 cm³-mole^–1; 4-methylpyridine, _C ^° = 378.9 J–°K^–1-mole^–1 and _V ^° = 94.3 cm³-mole^–1; 2,6-dimethylpyridine, _C ^° = 441.8 J–°K^–1-mole^–1 and _V ^° = 109.9 cm³-mole^–1. These _C ^° and _V ^° values are discussed in terms of effects of substitution of CH₃-for H– in the various solute molecules.The research reported here was carried out in the Department of Chemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4.     

A new component of Artemisia fragrans

A new component C₁₅H₂₂O₃, has been isolated from the epigeal part ofArtemisia fragrans. On the basis of chemical transformations and spectral characteristics it has been established that it has the structure of 1-hydroxy-5,7H,6,11H-eudesm-3,4-en-6,12-olide (I).V. L. Komarov Institute of Botany, Academy of Sciences of the Azerbaidzhan SSR, Baku. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 632–635, September–October, 1990.     

Electronic absorption spectra of rhenium(VII) compounds: The effect of the coordination number

Changes in electronic absorption spectra in the following series: MeRe(L₂)O₃ McReO3 ReO4– ReO₆5–, have been studied in terms of the qualitative MO scheme.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1563–1566, June, 1996.     

New advances in the field of synthesis of natural polyhydroxysteroids

This review of the literature and of the authors' own work, devoted to a discussion of new methods for the synthesis of sections of steroid molecules responsible for their biological action, consists of two parts. The first is devoted to methods of constructing polyoxygenated side chains C₃-C₈ of steroids. In it are discussed the Grignard, Wittig, and Claisen reactions using Me-organic complexes including the C-20, C-21, C-22, C-23, and C-24 compositions, the C-22(23) double bond, the C-22, C-23, and C-24 centers, and the C-24 and C-25 centers, and other methods. In the second part methods of constructing the A/B rings of natural polyhydroxysteroid are discussed: the construction of the 2,3-vicinal diol grouping in the 5H-⁷-6-keto fragment of the ecdysones, the construction of the 2,3-cis-diol grouping in the 7-oxa-6-keto-B-homo rings of the brass inolides, and methods of creating the ⁵-7-oxygen-containing ring B of steroids of the antheridiol group.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 3–28, January–February, 1988.     

Thermal decomposition of decavanadates of bivalent metals

The thermal decomposition of Cd₃V₁₀O₂₈ · 16H₂O and Mg₃V₁₀O₂₈ · 18H₂O has been investigated. It was found by means of IR spectroscopy and X-ray phase analysis that the final products of decomposition of the given compounds are V₂O₅, the corresponding metavanadates and the vanadium bronzes of cadmium and magnesium. Present and previous results allow conclusions on the thermal decomposition of decavanadates of bivalent metals.

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Zusammenfassung Die thermische Zersetzung von Cd₃V₁₀O₂₈ · 16 H₂O und Mg₃V₁₀O₂₈ · · 18 H₂O wurde untersucht. Durch IR-Spektroskopie und Röntgen-Phasenanalyse wurde festgestellt, daß die Endprodukte der Zersetzung der gegebenen Verbindungen V₂O₅ ist, entsprechend den Metavanadate und den Vanadiumbronze von Cadmium und Magnesium. Die gegenwärtigen und früheren Ergebnisse gestatten Folgerungen bezüglich der thermischen Zersetzung von Dekavanadaten zweiwertiger Metalle.

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Résumé On a étudié la décomposition thermique de Cd₃V₁₀O₂₈ · 16 H₂O et Mg₃V₁₀O₂₈ · · 18 H₂O. A l'aide des techniques de spectroscopie IR et de rayon X, on a établi que les produits finaux de la décomposition de ces composés sont V₂O₅, les métavanadates correspondants et les bronzes au vanadium, de cadmium et magnésium. Les résultats présents et antérieurs permettent de tirer des conclusions sur la décomposition thermique des décavanadates des métaux divalents.

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d₃V₁₀₂₈ · 16₂ Mg₃V₁₀O₂₈· 18H₂O. , , V₂O₅, . , , .

     

Measurements of relative thick target yields for PIGE analysis on light elements in the proton energy interval 2.4–4.2 MeV

In order to extend the energy range of the systematic investigation on relative thick target yields performed by ANTTILA et al² for 1E_p2.4 MeV bombarding energies, gamma spectra and yield data are presented for elements Z=3–9, 11–17, 19–21 in the energy range 2.4E_p4.2 MeV and the results are discussed from the point of view of PIGE analysis.     

Study of the evolution of a MoO3+Bi2MoO6 mixture in air and in the conditions of mild propene oxidation

MoO₃ can react with the gamma phase of bismuth molybdate (Bi₂MoO₆) in the conditions of propene oxidation to form the alpha phase (Bi₂Mo₃O₁₂) resulting in a more selective catalyst for propene oxidation to acrolein. Intimate contact between MoO₃ and the gamma phase is an important factor favoring the formation of the alpha phase.

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MoO₃ - (Bi₂MoO₆), - (Bi₂Mo₃O₁₂), .