Kinetics of formation of the mercury/II/-cyanide-bromide mixed ligand complex in dioxan-water solvent mixtures

The kinetics of formation of the mercury/II/-cyanide-bromide mixed ligand complex have been studied spectrophotometrically at 25°C, in dioxan-water mixtures of different compositions. The reaction can be described by the rate equation of a simple second-order reversible process. The rate constants of both the forward and reverse reaction vary periodically with the solvent composition, whereas the equilibrium constant of the reaction does not change to a large extent. The unusual behaviour of the rate constants is due to selective solvation of the reactants.

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- (ІІ) 25°C, - . . — — , . .

     

Kinetics and mechanism of reduction of thallium(III) by hydrogen peroxide in perchloric acid medium

The kinetics and mechanism of reduction of thallium(III) by hydrogen peroxide has been studied in 1.0 mol dm^–3 perchloric acid medium. The reaction is first order with respect to thallium(III) and second order with respect to hydrogen peroxide. A negative hydrogen ion and chloride ion catalysis is observed. Bromide ion is found to catalyze the reaction in low concentration. There is no effect of ionic strength on the rate of the reaction. A plausible mechanistic pathway for the reaction is suggested which leads to the following rate law: Rate=–d[T1(III)]/dt=kK[T1(III)][H₂O₂]²/[H⁺] where K is the formation constant of the complex between thallium(III) and hydrogen peroxide and k is the rate constant of the reaction between that complex and hydrogen peroxide. The computed values of E_a and S^# are 44.8±6.5 kJ mol^–1 and –107.8±22.2 JK^–1 mol^–1, respectively.

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(III) - - . - (III) . - - . . -- . , - :=–[T1(III)]/dt=kK[T1(III)][H₂O₂]²/[H⁺], - (III) - . E_A S^# 44,8±6,5 / –107,8±22,1 /·, .

     

Mechanism of homogeneous catalysis of isotope exchange during interaction of dihydrogen with alkaline solutions

The mechanism of hydrogen isotope exchange in aqueous alkaline solutions (AAS) of D₂ has been studied using Interacting Bonds Method (IBM) data obtained for hydrogen interaction with the molecular ion H₃O ₂ ^– . Models for the activated and metastable intermediate complexes are described.

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- D₂ (). () H₃O ₂ ^– . .

     

Thermogravimetric study of diatomites

The thermal curves of diatomites (kieselguhrs) in air display different profiles, depending on the type and quantity of impurities (carbonates, clays, etc.) present. TG and DTG runs can be used for a quick diagnosis of quality, but also give a nearly quantitative picture of the silica content of these minerals.

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Zusammenfassung In Abhängigkeit von Art und Menge der Verunreinigungen (Karbonate, Tonerde usw.) weisen die thermischen Kurven von Diatomiten (Kieselguhr) in Luft unterschiedlichen Verlauf auf. Einfache TG- und DTG-Untersuchungen können als Schnelldiagnose zur Bestimmung der Qualität benutzt werden und geben ausserdem noch ein nahezu quantitatives Bild über den Silikatgehalt dieser Mineralien.

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( ) , (, . .). , .

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The authors acknowledge the financial support of this work by the Comisión Asesora de Investigatión Cientifica y Técnica, Spain, through Project No. PR84-0151.     

Influence of the thermal treatment of platinum alumina catalysts with exhaust gases on their activity in cyclopropane hydrogenation

The activity of platinum/alumina catalysts in cyclopropane hydrogenation has been investigated. Catalysts heated in exhaust gases are considerably less active in cyclopropane hydrogenation as compared to samples calcined in air. A relatively stable modification of the metallic surface is formed, probably as a result of coke or poison deposition.

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- . , , , , , . , , .

     

Thermochemistry of Carbonization of Polypyromellitimide

The mechanisms of thermal degradation processes in polypromellitimide films were investigated by mass-spectrometric thermal analysis and high-resolution NMR spectroscopy in the solid state. Both the structures of the solid residues of pyrolysis products of the PM polyimide and the process of carbonization proper up to 1200° were studied. It was established that the breaking of the C_ar-O-C_ar bond in the diamine moiety is not the primary act of degradation of the molecular structure of the polymer, as might be expected on the basis of the value of the bond energy. The process of intermolecular crosslinking following polymer degradation under high-temperature conditions is completed by the formation of a complex nitrogen-containing heterocyclic structure.

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Zusammenfassung Der Mechanismus der in Polypyromellitfilmen ablaufenden thermischen Zersetzungsprozesse wurde durch massenspektrometrische thermische Analyse und hochauflösende Festkörper-NMR-Spektroskopie untersucht. Sowohl die Struktur des festen Rückstandes des Pyrolyseproduktes des PM-polyamids als auch der Prozeß der Verkokung bis 1200 °C wurden Untersucht. Es wurde festgestellt, daß das Aufbrechen der Bindung C _ar ,-O-C _ar im Diaminteil nicht der primäre Schritt der Zersetzun der molekularen Struktur des Polymers ist, wie nach dem Wert der Bindungsenergie zu erwarten wäre. Der auf die Hochtemperatur-Polymerzersetzung folgende Prozeß der intermolekularen Vernetzung endet mit der Bildung einer komplexen stickstoffhaltigen heterozyklischen Struktur.

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- (MTA) (MP BPTT) , 1200 °C. . , C _ap -C _ap , , .

     

Effect of hydrogen sulfide on the catalytic hydrodenitrogenation of 1,2,3,4-tetrahydroquinoline. Comparison of NiMo/Al2O3 and CoMo/Al2O3

The hydrodenitrogenation of 1,2,3,4-tetrahydroquinoline was carried out in a flow reactor (350 °C, 35 atm) over CoMo/Al₂O₃ and NiMo/Al₂O₃. It is shown that in both cases the addition of hydrogen sulfide to the feed promotes denitrogenation and inhibits hydrogenation.

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1,2,3,4- (350°C, 35 ) CoMo/Al₂O₃ NiMo/Al₂O₃. , .

     

Thermal analysis of conducting polymers part I

Thermogravimetry (TG) has been conducted on a series of electroconducting acid-doped polyanilines. The weight loss results suggest that the majority of dopants are eliminated between 230 °C to 350 °C leaving behind the skeletal non-conducting polyaniline. The doped polyaniline are thermally more stable than the pristine polyaniline in air at high temperatures. This suggests that despite the early elimination observed, the presence of dopant at the begining has a stabilizing effect on the skeletal polyaniline. By comparison the acid-doped polyanilines are more thermally stable than many other electroconductive polymers, such as polypyrroles and polyacetylenes.

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Zusammenfassung An einer Reihe von elektrisch leitenden säureversetzten Polyanilinen wurden thermogravimetrische (TG) Untersuchungen durchgeführt. Die Gewichtsverluste zeigen, daß die Mehrzahl der Zusätze bei einer Temperatur zwischen 230 °C und 350 °C eliminiert werden, wobei die nichtleitenden Polyaniline zurückbleiben. Bei hohen Temperaturen ist das versetzte Polyanilin in Luft thermisch stabiler als das ursprüngliche Polyanilin. Das bedeutet, daß eine anfängliche Gegenwart der Zusätze ungeachtet der frühen Eliminierung einen stabilisierenden Effekt auf das Polyanilingerüst ausübt. Im Vergleich erwiesen sich säureversetzte Polyaniline als thermisch stabiler als andere elektrisch leitende Polymere wie z. B. Polypyrrole oder Polyazethylene.

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, . , 230–350°, . , . , , . , - , , , .

     

Effect of the dispersity of substances on the macrokinetics of thermal analysis under non-isothermal conditions

The effect of the dispersity of the sample on the topochemical mechanism and on the kinetic parameters of thermolysis (A _sB_s + C_g) under non-isothermal conditions is discussed. For correctness of the experiment, a ratio of maximum and minimum particle diameters 6 is a necessary condition. The topochemical mechanism of the process should be determined separately for the initial and final stages.

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Zusammenfassung Die Wirkung der Dispersion der Probe auf den topochemischen Mechanismus und die kinetischen Parameter der Thermolyse (A_s B_s + C_g) unter nichtisothermen Bedingungen wird diskutiert. Die Genauigkeit des Experiments setzt ein Verhältnis der maximalen und minimalen Teilchendurchmesser von 6 voraus. Der topochemische Mechanismus sollte für die Anfangs- und Endphase des Vorganges einzeln bestimmt werden.

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Résumé L'effet de la dispersion de l'échantillon sur le mécanisme topochimique et sur les paramètres cinétiques de la thermolyse (A_s B_s + C_g) en conditions non-isothermes est discuté. La conditions nécessaire pour qu'une expérience soit correcte est que le rapport entre les valeurs maximale et minimale des diamètres des particules soit 6. Le mécanisme topochimique du processus devrait être déterminé séparément pour les étapes initiale et finale.

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(A + ) . d ./d 6; .

     

Catalytic properties of silica-molybdenum catalysts in propylene oxidation

The activity of silica-molybdenum catalyts in propylene oxidation is shown to be determined by the partially dehydrated silica-molybdenum heteropolyacid stabilized by the SiO₂ surface.

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, , SiO₂.

     

Studies with a derivatograph of the properties of a water film on a marble surface modified by tetradecylammonium chloride (TDACl)

The properties of water layers on bare marble and on marble samples covered with various amounts of tetradecylammonium chloride (TDACl) after flotation were investigated by thermal analysis methods. The dependences of the layer thickness, activation energy, enthalpy and entropy of the bonded watervs. the amount of TDACl previously deposited on the marble surface were determined. The results obtained and the literature data were used to propose an interpretation of the changes caused in these parameters by the coverage of the marble surface with TDACl molecules. A correlation between these parameters and the changes in water structure and marble flotatibility is also presented.

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Zusammenfassung Eigenschaften von Wasserfilmen auf unbeschichteten und mit Tetradecylammoniumchlorid (TDACl) in unterschiedlichen Mengen bedeckten Marmorproben wurden nach Flotation thermoanalytisch untersucht. Die Abhängigkeit der Schichtdicke, der Aktivierungsenergie und der Enthalpie und Entropie des gebundenen Wassers von der Menge des vorhergehend auf die Marmoroberfläche aufgebrachten TDACl wurden ermittelt. Die durch die Bedeckung der Marmoroberfläche mit TDACl verursachten Veränderungen dieser Parameter werden anhand der erhaltenen Resultate und von Literaturangaben interpretiert. Beziehungen zwischen diesen Parameters und Veränderungen der Wasserstrukturen und der Flotierbarkeit des Marmors werden angegeben.

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, (). , , . , , , . , .

     

Combinations of alkyl radicals with alkyl and substituted allyl radicals

In contrast with expectations based upon simple collision theory, reactions of alkyl radicals with substituted allyl radicals yield cross-combination ratios of =2. Reactions of CH ₃ ^\ with some C₅ radicals give >2, in accordance with theory.

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, =2. CH₃ ^\ C₅ >2, .

     

Thermal synthesis of non-stoichiometric Bi5.8PO11.2

The formation of the compound Bi_5.8PO_11.2 from 2.4 Bi₂O₃+BiPO₄ was investigated by means of DTA, simultaneous DTA—high-temperature thermomicroscopy, and X-ray diffraction. Solid-state reactions begin above 700 °C, followed by intermediate local melting and exothermic reactions. These are coupled with the intermediate formation of-Bi₂O₃, Bi₁₂P_0.8O₂₀ (both with sillenite structure) and Bi₄P₂O₁₁. The reaction is completed upon congruent melting of Bi_5.8PO_11.2 at 955 °C.The formation of Bi_5.8PO_11.2 from 2.9 Bi₂O₃+NH₄H₂PO₄ begins after melting of NH₄H₂PO₄ at around 200 °C, and is similarly completed at 955 °C.

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Zusammenfassung Die Bildung der Verbindung Bi_5.8PO_11.2 aus 2,4 Bi₂O₃+BiPO₄ wurde mittels DTA, simultaner DTA-Hochtemperatur-Thermomikroskopie und Röntgenbeugung untersucht. Die Umsetzung beginnt als Festkörperreaktion oberhalb 700 °C, gefolgt durch intermediäres örtliches Schmelzen und exotherme Reaktionen. Dabei werden als Zwischenprodukte-Bi₂O₃, Bi₁₂P_0.8O₂₀ (beide mit Sillenit-Struktur) sowie Bi₄P₂O₁₁ nachgewiesen. Die Umsetzung wird erst beim kongruenten Schmelzen des Bi_5,8PO_11,2 bei 955 °C beendet. Die Bildung von Bi_5,8PO_11,2 aus 2,9 Bi₂O₃ + NH₄H₂PO₄ beginnt nach dem Schmelzen des NH₄H₂PO₄ bei ca. 200 °C und geht ebenfalls erst bei 955 °C zu Ende.

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, Bi_5.8PO_11.2 2,4 Bi₂O₃ BiPO₄. 700° , — -Bi₂O₃, Bi₁₂P_0,8O₂₀ ( ) Bi₄P₂O₁₁. Bi_5,8PO_11,2 955°. 2,9 Bi₂O₃ NH₄H₂PO₄ 200° 955°.

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Thanks are due to Mrs. K. Norouzi for performing most of the DTA measurements, and to Mr. P. Höfner for the recording and discussions of the X-ray diffractograms.     

Studies on the catalytic decomposition of nitrous oxide on lanthanum cobaltate

The catalyst LaCo₂O₄ crystallizing in CaFe₂O₄ type structure has been synthesized and its physicochemical characteristics evaluated. The kinetics of decomposition of nitrous oxide, studied in the temperature range 400–460°C at 50 and 200 Torr of the reactant gas, was found to obey an expression corresponding to strong inhibition by product oxygen. A reaction mechanism has been proposed based on the existence of Co²⁺–O^2––Co³⁺ clusters on the surface.

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LaCo₂O₄, CaFe₂O₄, - -. , - 400–460°C 50 200 Qu , -, . Co²⁺–O^2––Co³⁺ .

     

Study of the adsorption of n-butylamine on NaHY zeolites by microcalorimetry

The adsorption, of n-butylamine has been studied at 405 K on NaHY zeolites by microcalorimetry. The curves of the variation in the heat of adsorption as a function of the coverage change characteristically with the temperature of activation of the zeolite. From the course of these changes it is possible to establish which part of the curve corresponds to the adsorption of n-butylamine on Brönsted or Lewis acid centers.

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- 405 NaHY . . , - .

     

Identification of nitride inclusions in steel using differential thermal analysis and evolved gas analysis

A preliminary study has been made of the feasibility of applying differential thermal analysis/evolved gas analysis (DTA/EGA) to the identification and estimation of nitrides in residues extracted from iron base alloys. A set of commercially available nitride powders have also been examined.The results showed that EGA traces are more informative than the DTA observations and, additionally, provide an estimate of the total nitrogen present. Residues from steels often contain elemental carbon and this complicates the interpretation of the DTA and EGA traces. It is generally concluded that the DTA/EGA technique is useful in identifying nitrides but should be ancilliary to other techniques such as X-ray diffraction.

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Zusammenfassung Eine Vorstudie wurde durchgeführt um die Einsatzmöglichkeit der Differentialthermoanalyse/Emittierte Gasanalyse (DTA/EGA) zur Identifizierung und Abschätzung der Nitride in aus Eisenbasenlegierungen extrahierten Rückständen zu prüfen. Eine Reihe handelsüblicher Nitridpulver wurde ebenfalls untersucht.Die Ergebnisse zeigten, daß EGA-Spuren informativer sind als die DTA-Beobachtungen und überdies eine Schätzung des Gesamtstickstoffgehaltes gestatten. Rückstände aus Stählen enthalten oft Kohlstoff und dies erschwert die Deutung der DTA- und EGA-Spuren. Im Allgemeinen kann gefolgert werden, daß die DTA/EGA-Technik bei der Identifizierung von Nitriden nützlich ist, doch nur als Ergänzung anderer Techniken, wie z. B. die Röntgendiffraktion, eingesetzt werden sollte.

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Résumé On a effectué une étude préliminaire pour rechercher si l'emploi conjugué de l'analyse thermique différentielle et de l'analyse des gaz émis (ATD/AGE) pouvait servir à l'identification et à l'estimation de la teneur des nitrures présents dans les résidus d'extraction des alliages à base fer. On a également examiné une série de nitrures en poudre disponibles commercialement.Les résultats ont montré que les enregistrements d'AGE fournissent davantage de renseignements que les courbes ATD car ils donnent en plus la valeur de l'azote total présent. Les résidus d'extraction des aciers contiennent souvent du carbone élémentaire, ce qui complique l'interprétation des enregistrements d'ATD et d'AGE. L'étude permet de conclure qu'en général la technique d'ATD/AGE est utile pour identifier les nitrures, mais qu'elle devrait être utilisée comme méthode auxiliaire vis-à-vis d'autres techniques, par ex. la diffraction des rayons X.

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( /) , . . , , . , . , / , , .

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The authors would like to express their thanks to the Directors of the British Steel Corporation, Tubes Division for permission to publish this paper.     

Kinetics of hydroperoxyde-dependent naphthalene hydroxylation involving cytochrome P-450 of the intact and induced enzyme systems of rat liver microsomes

Hydroperoxide-dependent naphthalene hydroxylation involving rat liver microsomes has been studied. The direct interaction between cytochrome p-450 and cumyl hydroperoxide (CHP) has been demonstrated. K_m values with respect to both the substrate and CHP have been determined using intact and induced enzyme systems. The nature of the hydroxylating agent and the possible role of high-valence iron in the processes of hydroxylation by microsomal systems is discussed.

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. P-450 . K_m . , .

     

X-ray study of Re/Al2O3 and Re+Pt/Al2O3 catalysts using synchrotron radiation

Uning synchrotron radiation, L_III rhenium absorption spectra have been studied for Re/Al₂O₃ and Re+Pt/Al₂O₃ catalysts obtained by impregnation. For individual rhenium compounds a linear dependence between the shift of absorption edge and the state of rhenium oxidation has been found. The absorption spectra of reduced catalysts are significantly broadened as compared with those of individual compounds of the same valency. This points to the presence of rhenium compounds in different oxidation states.

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L_III- , Re/Al₂O₃ Re+Pt/Al₂O₃, . . . .

     

Kinetics of bromate-cerium(III) reaction

The induction period and the fast, and slow rates of the bromate-cerium(III) reaction were examined. It was found that the duration of the induction period was inversely proportional to both the bromate and acid concentrations, and that the fast reaction rate was proportional to the square of bromate concentration.

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(III). , , .