Some aspects of the thermal behaviour of In2Se3

On the basis of measurements of the specific heat capacity from 7 to 525 K and of DTA investigations from 300 K up to the melting point, it was possible to clarify the problem of the occurrence of the two room-temperature modifications of In₂Se₃.

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Zusammenfassung Anhand von DTA-Untersuchungen im Bereich zwischen 300 K. und dem Schmelzpunkt und durch Messung der spezifischen WÄrmekapazitÄt im Bereich von 7 K bis 525 K. konnte eine KlÄrung hinsichtlich des Auftretens von zwei In₂Se₃-Raumtemperatur-Modifikationen gegeben werden.

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, 300 , 7–525 , .

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The authors thank St. Budurov (Sofia) for helpful discussions.     

Possibility of thermal analysis of different types of bonding of water in minerals

Various types of water bonding were studied. e.g. water bound by occlusion, by adsorption, by capillary condensation, by chemisorption and as a solid solution, zeolitic water, interlayer water, crystal water and structural water bound in form of hydroxil groups. The differentiation of these various types of bonding is rather difficult, for on heating water is evolved at various temperatures and in rather wide temperature domains which overlap to different extents. Efforts were made to improve the detection by applying the quasi-isothermal quasi-isobaric measuring technique.

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Zusammenfassung Es wurden verschiedene Bindungstypen von Wasser untersucht. Wasser kann unter anderem durch Einschlüsse, Adsorption. Kapillarkondensation, Chemisorption und in Form von Mischkristallen, zeolitisch, schichteingebettetem und Kristallwasser sowie als OH-Form gebunden sein. Die Untersuchung dieser zahlreichen Bindungstypen ist äußerst schwierig, da die Wasserabgabe bei verschiedenen Temperaturen geschieht und die ziemlich breiten Temperaturintervalle mehr oder weniger überlappen. Mittels quasiisothermen und quasiisobaren Meßtechniken wurde versucht, die Möglichkeit der Bestimmung zu verbessern.

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. , , , , , , , . , , . , .

     

Intermediates of homogeneous deuterium exchange in alkanes catalyzed by Pt(II)

The rate constants and distribution of deuterated products of the H-D exchange in alkanes (C₁–C₈) have been measured for aqueous solutions of K₂PtCl₄. The reaction involves the intermediate formation of alkyl, 1,1-(carbene). 1,2-(olefin), 1,3-(cyclopropane) and 1,4-(cyclobutane) type hydrocarbon complexes. The selective attack of Pt(II) on the primary, secondary and tertiary C–H bonds in alkanes (110) is due to the predominance of steric over polar effects.

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H-D (C₁–C₈) K₂PtCl₄ , , 1,1-(), 1,2-(), 1,3-() 1,4-() . Pt(II) ., ., . C–H (110) .

     

Non-exchangeable organically bound tritium (OBT): its real nature

Denaturation experiments show that the larger part of organically bound tritium (OBT) consists of buried tritium and is not bound to carbon, as has been traditionally assumed. The logistical growth analysis of hydrogen isotopes in dry plant matter reveals a larger rate of increase of OBT than organically bound hydrogen (OBH). This is reflected by tritium accumulation for 1.4 and 2 in the primary hydration shell and in the base-pairing hydrogens of DNA respectively. If tritons and protons are considered as quantum mechanical entities, the accumulative tritium transfer from water to the hydrogen bonds of biopolymers is generally valid. Growth experiments confirm the assumed rapid isotope exchange in vivo, which is not observed in vitro by denaturation.     

Contribution a l'étude de l'oxyde de cadmium en milieu alcalin

Résumé La thermogravimétrie et l'analyse thermique différentielle montrent que l'oxydation du cadmium à l'air est négligeable jusqu'à 400°, tandis qu'en présence de peroxyde de sodium de soude ou de peroxyde de baryum, elle est totale mais que l'agent oxydant est uniquement l'oxygène de l'air. Le calcul de la chaleur de réaction à partir de la mesure de l'air du pic d'ATD correspondant fait conclure à la seule formation de l'oxyde de cadmium, le pic de fusion étant utilisé comme référence.

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Thermogravimetric and differential thermoanalytical investigations have shown that the oxidation of cadmium in air is negligible up to 400°. In the presence of sodium peroxide, barium peroxide or sodium hydroxide complete oxidation takes place, the aerial oxygen acting as the only oxidizing agent. The heat of reaction, calculated from the DTA peak area using the peak corresponding to the melting of the sample as reference, indicated that exclusively cadmium oxide was formed.

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Zusammenfassung Thermogravimetrische und differentialthermoanalytische Untersuchungen zeigten, daß die Oxydation des Kadmiums in Luft bis zu 400° vernachlässigbar ist. In Gegenwart von Natriumperoxyd, Bariumperoxyd oder Natriumhydroxyd tritt vollständige Oxydation ein. Als Oxydationsmittel wirkt jedoch ausschließlich der Luftsauerstoff. Die aus der Messung der DTA Spitzenfläche erfolgte Berechnung der Reaktionswärme, wobei die dem Schmelzen entsprechende Spitze als Referenz diente, wies auf die alleinige Bildung von Kadmiumoxyd hin.

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, 400° . , , . , TA, , , .

     

Cyclohexanol conversion of Pt-and Co-promoted molybdena-alumina; Effect of S-uptake

The uptake of sulfur reduces the overall activity of PtMo/Al₂O₃ and enhances that of CoMo/Al₂O₃ in conversion of cyclohexanol. Significant changes in selectivity indicate the existence of different active sites of the initial catalyst for hydro-dehydrogenation and dehydration. The differences in catalytic activity expressed in terms of overall TOF decrease with increasing sulfur treatment like for Ru and Ir promoted catalysts.

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PtMo/Al₂O₃ CoMo/Al₂O₃. - . Ru .

     

Scattering from concentration fluctuations in polymer blends: A monte carlo investigation

The collective scattering function S_coll( ), which describes light (neutron-, x-ray) scattering under wavevector , is obtained from Monte Carlo simulations for a symmetrical polymer mixture. The polymers are modelled by self-avoiding walks ofN _A=N_B=N steps on a simple cubic lattice, where a fraction _V of sites is left vacant, and an attractive energy occurs if two neighboring sites are taken by the same kind of monomer. Spinodal curves are estimated from linear extrapolation of S _coll ^–1 (0) vs./k _B T, whereT is the temperature. Also the single chain structure factor is obtained and the de Gennes random phase approximation (RPA) can thus be tested. Unexpectedly, strong deviations are found if one species is very dilute. The estimation of an effective Flory-Huggins-parameter from scattering data is also discussed.Contributed paper delivered at the Tagung der Deutschen Physikalischen Gesellschaft, Fachausschuß Polymerphysik, Hamburg, March 14–16, 1987.     

Détermination de la pureté de la sulfapyridine s par analyse thermométrique

Résumé L'étude thermoanalytique de la pureté de deux échantillons de sulfapyridine, médicament (I) et standard (II), a été réalisée par différentes méthodes. Par mesure de la transparence les valeurs moyennes de la température et du domaine de fusion indiquent une teneur en impureté plus faible pour (II) que pour (I). Disposant de deux analyseurs thermiques de conception différente, les auteurs ont montré l'excellente concordance des résultats: 99.790 ± 0.047 % et 99.800 ± 0.045 % (I). Seule l'analyse calorimétrique différentielle permet d'évaluer avec précision le taux de pureté de (II) 99.956 ± 0.028 %, valeur représentant un seuil pour l'analyse calorimétrique différentielle à compensation de puissance (DSC 1B).

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The thermoanalytical purities of two sulfapyridine samples, drug (I) and standard (II), have been studied with different methods. By transparency measurement the fusion temperatures and intervals indicate a lower percentage of impurity for (II) than for (I). By means of two thermal analyzers the authors have shown the good agreement of the results: 99.790±0.047% and 99.800±0.045% (I). Heat-flux differential scanning calorimetry is the only method able to give precisely the degree of purity of (II): 99.956±0.028 %, this value being a limit for the power-compensation differential scanning calorimetry analysis (DSC 1B).

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Zusammenfassung Das Studium der thermoanalytischen Reinheit der beiden Sulfapyridinproben drag(I) und standard(II) wurde durch verschiedene Methoden durchgeführt. Schmelztemperaturen sowie-bereiche zeigen im Falle von Transparenzmessungen einen geringeren Prozentsatz von Verunreinigungen für (II) als für (I). Unter Anwendung zweier Thermoanalyser zeigten die Autoren die gute Übereinstimmung der Ergebnisse: 99.790±0.047% und 99.800 ± 0.045 % für (I). Ein Wärmeströmungs-Differentialabtastkalorimeter bietet die einzige Möglichkeit den Reinheitsgrad von (II) genau zu bestimmen: 99.956 ± 0.028 %, wobei dieser Wert die Grenze für die Kraft-Kompensations-Differentialkalorimetrie (DSC 1B) darstellt.

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: (I) (II). , , II , I. , : 99.790±0.047% 99.800 ± 0.045% I. II: 99.956 ± 0.028% ( 1).

     

Infrared spectra of nitric oxide adsorbed on photoreduced V/SiO2 catalyst

Studies of the IR spectra of surface species produced via NO adsorption on selectively photoreduced V/SiO₂ catalysts indicate that at low coverages NO is adsorbed on V³⁺ ions to form strongly bonded mononitrosyl species V³⁺...... NO. With increasing NO coverage, V³⁺ is oxidized to V⁴⁺, which is accompanied by the appearance of gaseous N₂O and weak adsorption of NO on V⁴⁺.

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- , NO V/SiO₂ . , V³⁺ NO V³⁺... NO. V³⁺ V⁴⁺, N₂O NO V⁴⁺.

     

Thermal decomposition of Cu(II) Malonate

The isothermal decomposition of anhydrous Cu(II) malonate of uniform particle size has been studied at 170, 180 and 190°. Decomposition to cupric oxide takes place via the intermediate formation of 2CuCO₃.Cu(OH)₂. X-ray diffraction has been employed to identify the decomposition products. The experimental kinetic data for Cu(II) malonate decomposition are best fitted by two stages: (i) a linear process and (ii) a first-order expression. The activation energies for the two kinetic stages have been found to be 45.7 and 57.2 kcal/mole, respectively. A DTA study of Cu(II) malonate decomposition has also been made. Activation energies have been determined via analysis of the DTA curve using the Borchardt and Piloyan equations.

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Zusammenfassung Die isotherme Zersetzung von wasserfreiem Cu(II)-malonat einheitlicher Partikelgröße wurde bei Temperaturen von 170°, 180° und 190° untersucht. Die Zersetzung von Cu(II)-malonat zu Kupfer(II)-oxid erfolgt über die intermediäre Bildung von 2CuCO₃.Cu(OH)₂. Die Röntgendiffraktionstechnik wurde zur Identifizierung der Zersetzungsprodukte eingesetzt. Die Versuchsergebnisse von Cu(II)-malonat können am besten zwei kinetischen Zuständen angepaßt werden: (1) einem linearen Prozeß und (2) einem Ausdruck erster Ordnung. Die entsprechenden Aktivierungsenergien für die zwei kinetischen Zustände waren 45.7 Kcal/Mol bzw. 57.2 Kcal/Mol. Eine DTA-Untersuchung von Cu(II)-malonat wurde ebenfalls durchgeführt. Die Aktivierungsenergien wurden aus der Analyse der DTA-Kurve mittels der Gleichungen von Borchardt und Piloyan bestimmt.

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Résumé On a étudié la décomposition thermique du malonate de cuivre(II) anhydre à 170, 180 et 190°. La décomposition du malonate en CuO se produit avec formation intermédiaire de 2CuCO₃.Cu(OH)₂. Les produits de décomposition ont été identifiés par diffraction des rayons X. Les données expérimentales correspondent à deux étapes de cinétique différente: (i) un processus linéaire et (ii) une expression du premier ordre. Les énergies d'activation respectives des deux étapes cinétiques s'élèvent à 45.7 et 57.2 kcal.mol^/s-1. Le malonate de cuivre(II) a aussi été étudié par ATD. Les énergies d'activation ont été déterminées à partir de la courbe ATD en appliquant les équations de Borchardt et de Piloyan.

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(II) 170°, 180° 190°. (II) 2CuCO₃. Cu(H)₂. . (II) : (1) (2) . , , , 45,7 / 57,2 /. (II). , , .

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One of the authors (P.C.K.) is grateful to the University Grants Comission, New Delhi, for the award of a junior research fellowship. The authors are grateful to Dr. K. N. Goswami of the Physics Department, University of Jammu, for his help in the X-ray studies of the products.     

Epoxidation of cyclohexene with tert-butyl hydroperoxide catalyzed by polymer anchored molybdenum complexes

Catalytic activity of molybdenum hexacarbonyl anchored on various polymers was investigated for the epoxidation of cyclohexene with tert-butyl hydroperoxide. The activity was increased by anchoring on the polymer. The catalyst on polystyrene showed much higher activity than Mo(CO)₆ used under homogeneous conditions.

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, , .— . . ]qt, Mo(CO)₆, .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Calorimetric study of the BrO3?/Ce4+/cyclohexanone and BrO3?/Ce4+/cyclopentanone oscillating systems

The heat output (Q) during the induction period of a Belousov-Zhabotinskii oscillating reaction usually evolves at a constant rate /6/; we observe in the BrO ₃ ^– /Ce⁴⁺/Cyclohexanone system a sudden change in the slope of the function Q=f(t), which corresponds to the beginning of the quasistationary phase /3/.

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(Q) - ; BrO ₃ ^– /Ce⁺⁴/ Q=f(t), .

     

Influence of the preparation method on the pore spectrum of Pt?Cr/Al2O3 and Pt?Sn/Al2O3 catalysts

It is shown that, in contrast to classical impregnation methods, in bimetallic catalyst production the texture of the carrier is stabilized by introducing the promoting ion on the surface of Pt/Al₂O₃ with vapors of CrO₂Cl₂ or SnCl₄. This is shown by a relatively slower decrease of the specific area and the volume of the pores upon calcination.

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, Pt/Al₂O₃- CrO₂Cl₂ SnCl₄ . .

     

Acidity and oxidation activity of MoO3?UO3/SiO2 catalysts

The effect of UO₃ on the acidity of MoO₃–UO₃/SiO₂ catalysts has been studied by means of infrared spectroscopy of adsorbed pyridine. The surface acidity exhibited a maximum for the same U/(U+Mo) atomic ratio (=0.11) that yielded a maximum in total conversion for isobutene oxidation. The catalytic properties for oxidation are discussed in terms of the acidic properties of the samples.

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UO₃ MoO₃–UO₃/SiO₂ . U/(U+Mo)=0,11, . , .

     

ESCA study of modifying effect by potassium carbonate on Pd/γ?Al2O3 catalysts

ESCA studies of the state of Pd/–Al₂O₃ catalysts modified by potassium carbonate show that such catalysts differ from unmodified samples in much greater changes of a positive charge of palladium ions under redox conversions. This is ascribed to the lower interaction of Pd with the support in modified samples.

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Pd/–Al₂O₃ . , -, Pd .

     

Kinetics of reduction of iron ore—coal pellets

Kinetic data on the reduction of iron ore-coal pellets are compared with similar data for lump ore. It is shown that, when ore and coal are mixed intimately, the reduction reactions are accelerated considerably. Ore-coal pellets offer some additional advantages, as discussed in the text.It is shown that the kinetics of ore-coal reduction can be studied by using a pseudo kinetic parameter,f (fraction of reaction), defined as the instantaneous weight loss divided by the maximum possible weight loss. Plots off versust have been analysed to establish the kinetic equations and evaluate the kinetic parameters.

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Zusammenfassung Die kinetischen Daten der Reduktion von Eisenerz-Kohle-Pellets wurde mit ähnlichen Daten von Stückerz verglichen. Es wurde gezeigt, daß die Reduktionsreaktionen im Falle einer intensiven Vermischung von Erz und Kohle erheblich beschleunigt werden. Erz-Kohle-Pellets besitzen einige zusätzliche Vorteile, auf die im Text näher eingegangen wird. Es wurde gezeigt, daß die Kinetik der Erz-Kohle-Reduktion mit Hilfe eines pseudokinetischen Parametersf (Reaktionsbruch) untersucht werden kann, der als Quotient aus aktuellem Gewichtsverlust und maximal möglichem Gewichtsverlust definiert wird. Zur Bestimmung der kinetischen Gleichungen und der Berechnung der kinetischen Parameter wurde einf–t Diagramm ausgewertet.

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- . , , . . , - , g ( ), . f t .

     

Interaction of PM12?nVnO40?(3+n) (M=Mo, W) heteropoly complexes with nitrogen oxide

In aqueous solution, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) hetero-polyanions provide a much faster oxidation of NO than mononuclear VO ₂ ⁺ ions, yielding HNO₂, NO ₃ ^– and reduced HPA.

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, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) , VO ₂ ⁺ , NO HNO₂ NO ₃ ^– .

     

Acid-base properties of Al2O3/MgO oxides, II. Infrared study of adsorption of pyridine

Mixed oxides of alumina and magnesia were characterized by an IR study of pyridine adsorption. Three different Lewis acid sites, but no Brönsted acid sites were detected. The strongest adsorption sites are attributed to Al³⁺ cations of the alumina phase (1455 cm^–1), the weaker Lewis acid sites were assumed to be due to cations of the MgAl₂O₄ phase (1449–1443 cm^–1) and the MgO phase (1440–1438 cm^–1).

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. , , . Al⁺³ (1455 ^–1), MgAl₂O₄ (1443 ^–1) MgO (1438 ^–1).

     

Determination of reactivity constants of 5-substituted 2-indolyl groups by means of13C NMR

Conclusions A series of 5-substituted 2-phenylindoles has been synthesized; the¹³C chemical shifts have been measured for these compounds in acetone, and these data have been used to determine the _I and _R ^O constants of the 5-substituted 2-indolyl groups. Relationships have been found for the estimation of the constants of any 5-substituted 2-indolyl group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 312–315, February, 1985.