Zur thermischen Zersetzung des Hg2Cl2 und Hg2Br2

Thermical Decomposition of Hg₂Cl₂ and Hg₂Br₂ The thermical decomposition of Hg₂Cl₂ and Hg₂Br₂ was proved by total pressure measurements in a membrane manometer. The decomposition according to Hg₂X_2,s = Hg_,g + HgX_2,g and their thermodynamic data were confirmed.     

Zur thermischen Zersetzung von Ammoniumfluorochromaten

On the Thermal Decomposition of Ammonium Fluoro Chromates The thermal decomposition of the ammonium fluoro chromates (NH₄)₂[CrF₅(H₂O)], (NH₄)₃CrF₆, and (NH₄)₂[Cr(H₂O)₆]F₅ has been investigated by thermoanalytical and X-ray investigations. Steps of decomposition are the formation of (NH₄)₃CrF₆ und NH₄CrF₄. Further the formation of a chromium fluoride ammoniate CrF₃ · xNH₃ (x ≥ 1) has been detected. The end product of decomposition is the rhomboedrical CrF₃. The hydrolysis reactions have been suppressed by using quasi-isobaric conditions. As by-reaction a partial reduction of CrF₃ has been detected leading to the formation of Cr₂F₅.     

Zur Untersuchung der thermischen Zersetzung polymerer Stoffe

Ohne Zusammenfassung     

Zur Kinetik der chloridkatalysierten thermischen Zersetzung von Ammoniumnitrat

On the Kinetics of Chloride Catalyzed Thermal Decomposition of Ammonium Nitrate The activation energies and frequency factors of thermal decomposition reactions of ammonium nitrate and mixtures of ammonium nitrate and chloride have been determined by volumetric measurement of the gaseous decomposition products evolved on linear hcating. The rate constants obtained from these values show that thermal stability and initial decomposition temperature of ammonium nitrate are considerably reduced by addition of small amounts of chloride.     

Zur thermischen Zersetzung der hochkonzentrierten Salpetersäure

The thermal decomposition of highly concentrated nitric acid was observed at atmospheric pressure between 0 and 60 °C for up to 273 d. The decomposition of highly concentrated nitric acid $$2 HNO_3 \rightleftharpoons 2 NO_2 + H_2 O + {1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2} O_2 $$ is a second order reaction in nitric acid. The reversible reaction proceeds to equilibrium. The velocity and equilibrium constants were obtained by kinetic evaluation of the readings for HNO₃ and NO₂. The activation energy for decomposition was — 134 kJ/mol.     

Zur thermischen Zersetzung von mechanisch aktivierten und γ-bestrahlten Silberoxalaten unterschiedlicher Dotierung

On the Thermal Decomposition of Mechanically Activated and γ-Radiation-treated, Pure and Doped Silver Oxalate Both on mechanical activating and on γ-radiation treating of silver oxalate, the concentration of Frenkel defects in the crystal lattice is strongly increased, leading to a facilitation of the electron transfer decomposition process and to an acceleration of the Ag° nucleation. At longer treating the reaction inhibition is almost completely compensated by nuclei formation. In the beginning of the decomposition, the nuclei grow 3-dimensionally, at a later stage, however, 1-dimensionally. Due to an increase of the surface in the case of mechanical treatment the range of 3-dimensional growth is more extended. On mechanical treating of variously Cu²⁺ doped silver oxalate two overlapping effects, acting contrarily on the thermal lattice stability, result.     

Die Fehlordnung des Natriumazides und deren Einfluß auf die thermische Zersetzung, 3. Mitt.: Modell einer diffusionskontrollierten thermischen Zersetzung des Natriumazides

Zusammenfassung Abweichungen von der normalen Leitfähigkeit des NaN₃ lassen vermuten, daß bei der Keimbildung und beim Keimwachstum atomare Diffusionsprozesse stattfinden. Unter der Annahme, daß die Zersetzungsreaktion durch das Keimwachstum an denhk0-Begrenzungen des Kristalls gegeben ist und für jedes an den Kontakt Na/NaN₃ diffundierende Natriumion die äquivalente Menge Stickstoff frei wird, wird mit Hilfe eines Zylindermodells eine Geschwindigkeitsgleichung abgeleitet. Zur experimentellen Überprüfung werden isotherme Zersetzungen von NaN₃-Pulvern mit definierter Korngröße herangezogen. Die analytische Auswertung der Umsatz/Zeit-Funktion ergibt eine quadratisch-hyperbolische Teilchenradienabhängigkeit sowie eine der Diffusion entsprechende Temperaturabhängigkeit der Geschwindigkeitskonstante, wie sie durch das Modell gefordert wird.

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From deviations of the normal ionic conductivity of NaN₃ it may be concluded that atomic diffusion processes are taking place with nucleiation and nucleus growth. A rate equation can be derived by means of a cylindric model, supposing that a decomposition reaction is given by nucleus growth athk0-planes of the crystal and supposing that for each sodium ion diffusing to the sodium/sodiumazide-contact an equivalent quantity of nitrogen becomes free.Isothermic decompositions of NaN₃ powders with defined particle size are carried out for experimental examination. The analytical evaluation of the pressure—time-function shows a squarehyperbolic dependence of the particle radius as well as a temperature dependance of the rate constant correponding to the diffusion as it is requested by the model.

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Mit 7 Abbildungen     

Zur Kenntnis der thermischen Zersetzung von Ammoniumhexafluoroscandat,-titanat,-vanadat und-chromat

Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described.     

Über Ammonium-Uranyl-Vanadat und die Produkte seiner thermischen Zersetzung

Ammonium Uranyl Vanadate and the Products of its Thermal Decomposition Hydrated ammonium uranyl vanadate has been investigated with roentgenographic and spectroscopic methods. The analysis of the powder diagramm shows that the compound is structurally related to the mineral Carnotite. The i. r. and Raman spectra also confirm this relation. The thermal behaviour of NH₄UO₂VO₄ · nH₂O is also reinvestigated and the uranyl divanadate, (UO₂)₂V₂O₇, produced during this decomposition is fully characterized. Its behaviour in the temperature range up to 1200°C is also investigated.     

Zur Tribochemischen Zersetzung von Alkali-Bromaten und -Nitraten

The tribochemical decomposition of alkali bromates and nitrates Tribochemical decompositions of bromates and nitrates of alkali metals are described and compared with the analogous thermal reactions. On the basis of thermodynamical investigations it is concluded, that the tribochemical decompositions are stimulated by the triboplasma.     

Die Sublimation und thermische Zersetzung von TeJ4 und die Existenz von TeJ2 in der Gasphase

The Sublimation and the Thermal Decomposition of TeJ₄ and the Existence of TeJ₂ in the Gaseous Phase The sublimation and the decomposition of TeJ₄ have been investigated. For the sublimation and the decomposition reactions and the values of enthalpy and entropy were derived (see ?Inhaltsübersicht”?). The existence of TeJ₂ in the gaseous phase was demonstrated by equilibrium measurements and chemical transport experiments.     

Untersuchungen zur thermischen Zersetzung von Boraten

In spite of numerous investigations the literature data on the thermal decomposition of borax are contradictory. On the basis of thermal, X-ray, gas analytical and optical investigations this fact can be attributed to the complex decomposition mechanism. After the release of about 8 mole water the reaction product is an X-ray amorphous phase, having the thermal behaviour of glass. From this glass sodium diborate (Na₂O.2B₂O₃) crystallizes between 500–600? with further mass loss. Sodium diborate decomposes from about 700? incongruently yielding NaBO₂ vapor and B₂O₃ glass phase. After evaporation of NaBO₂ is completed the rate of evaporation of B₂O₃ increases considerably.     

Untersuchung der thermischen Zersetzung von Aluminium-dodekawolframatosilicat

Investigation on the Thermal Degradation of Aluminium-12-Tungstosilicate The dehydration of aluminium-12-tungstosilicate AlH[SiO₄W₁₂O₃₆] · 29 H₂O gives the anhydrous salt at 440°C. By means of X-ray heating patterns, thermal analysis, and i.r. spectroscopy the formation of the new phase 1/2 Al₂O₃ · SiO₂ · 12 WO₃ (I) at 500°C is observed, stable at room temperature. Above 800°C from I tetragonal W₃, Al₂(WO₄)₃, and amorphous SiO₂ are formed. Amorphous SiO₂ crystallizes to high-temperature cristobalite at 1000°C. High-resolution ²⁷Al NMR (MAS-technique) is used to determine the coordination number of aluminium in the different phases.     

Zur Zersetzung von Tetrathiowolframaten und Bildung von Nonathiotriwolframaten

Decomposition of Tetrathiotungstates and Formation of Nonathiotritungstates The tetrathiotungstates have been prepared by reaction of [NH₄]₂WS₄ with [R₄X]Y (Y = OH, Cl or I). The tetrathiotungstates decompose under variable conditions to form [R₄X]₂W₃S₉. The thiotungstates [R₄X]₂WS₄ and [R₄X]₂W₃S₉ have been characterized by chemical and thermoanalytical methods as well as by infrared, electron absorption, ¹H-NMR, and mass spectra. The decomposition of [R₄N]₂WS₄ has been studied kinetically. A mechanism of the formation of W₃S₉^2? is suggested.     

Die Fehlordnung des Natriumazides und deren Einfluß auf die thermische Zersetzung, 5. Mitt.: Primärprozesse der thermischen Zersetzung von Natriumazid

Zusammenfassung Elektronische Zustände des Natriumazides werden durch ein Energiebandmodell charakterisiert, dem mittlere spektroskopische Eigenschaften zugrunde liegen. Unter Verwendung von UV-Absorptionsspektren sowie der in der 2. Mitt. ber. Polarisationsund Gitterenergie kann mit Hilfe eines Kreisprozesses das Bandmodell vervollständigt werden. Ein Vergleich mit den elektronischen Daten der Natriumhalogenide ergibt, daß sich das NaN₃, wenn man von den feinstrukturellen Eigenschaften, die zur Zersetzung führen, absieht, natriumhalogenidähnlich verhält. Weiters werden Studien über elektronische Primärprozesse bei der thermischen Zersetzung mitgeteilt. Als geschwindigkeitsbestimmender Primärschritt wird ein Elektronentransfer von Azid-Ionen zu Elektronenfallen angenommen. Wie eine quantenmechanische Betrachtung gestörter Gitterpotentiale zeigt, ergeben kationische Fremdionen, anionische Leerstellen und Oberflächen Elektronenfallen, während kationische Leerstellen und anionische Fremdionen Streustellen für Elektronen und Excitonen darstellen. Auf der Basis eines Störzentrengases kann eine Geschwindigkeitsgleichung für den Primärschritt abgeleitet werden, die qualitativ durch Umsatz/Zeit-Kurven belegt wird. Diese wurden durch Registrierung der bei der Zersetzung entstehenden Stickstoff-Druck-Zunahme gewonnen. Durch Zersetzung von NaN₃-Präparaten mit verschiedenen Gitterfehlern wird gezeigt, daß mit steigendem Einbau von kationischen Fremdionen, anionischen Leerstellen sowie einer Vergrößerung der Oberfläche die autokatalytische Zersetzung beschleunigt und mit steigendem Einbau von anionische Fremdionen die Reaktion verzögert wird. In der Sprache der Festkörperchemie entspricht dies einer Variation der Keimbildungsperiode.

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Electronic states of sodium azide are characterized by an energy band model, based on mean spectroscopic properties. Using UV-absorption-spectra and the calculated polarization and lattice energies (see paper 2) the band model can be completed by means of a cyclic process. A comparison with the electronic data of sodium halogenides shows that sodium azide behaves similar neglecting the microstructural properties leading to the decomposition. Moreover, studies on electronic primary processes during thermal decompositions are reported on. An electron transfer from azide ions to electron traps is assumed to be a rate determining step. As shown by a quantum mechanical consideration of disturbed lattice potentials cationic impurities, anionic vacancies and surfaces give rise to electron traps, whereas cationic vacancies and anionic impurities represent defraction centers for electrons and excitons. Based on imperfections behaving like a gas a rate equation for the primary step can be derived, which is proved qualitatively by pressure/timecurves. By decomposing samples of sodium azides with various lattice defects it is shown that with increasing amounts of cationic impurities, anionic vacancies and an increase of the surface, the autocatalytic decomposition is accelerated, whereas with increasing amount of anionic impurities the reaction is slowed down. In decomposition chemistry this corresponds to a variation of the nucleiation period.

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Mit 9 Abbildungen     

Zur thermischen Zersetzung vom (NH4)2[FeF5(H2O)] unter quasi-isobaren Bedingungen

On the Thermal Decomposition of (NH₄)₂[FeF₅(H₂O)] on Quasi-Isobaric Conditions The thermal decomposition of (NH₄)₂[FeF₅(H₂O)] was investigated by thermal and X-ray analysis. Quasi-isobaric conditions are realized by using a special crucible which guaranteed a pressure of the gaseous products of 70 kPa. In dependence on the partial pressure α- or β-(NH₄)₂FeF₅ were formed during dehydration. Further intermediate products are NH₄FeF₄, (NH₄)_1?xFeF_4?x, and (NH₄)_yFeF₃ with x = 0.15–0.20 and y = 0.12–0.15. Structural relations between these phases are discussed and comparable considerations to the Al system were made.     

Ueber Zersetzung und Bestimmung des Wasserstoffsuperoxyds durch Silberoxyd

Ohne Zusammenfassung     

Intramolekulare Redoxreaktionen bei der thermischen Zersetzung von Additionskomplexen des Typs Mo(NO)2Cl2L2 und Mo(NO)Cl3L2

The intermediates formed from Mo(NO)₂Cl₂ L ₂ and Mo(NO)Cl₃ L ₂ by splitting-off of weakly-coordinated ligandsL (alcohols, glycols, nitriles) decompose in exothermic reactions: the decomposition products are N₂, MoOCl₄ and MoO₃. If the ligandL is strongly coordinated and is reducing (DMFA, DMSO, Pph₃, Asph₃), the NO groups oxidize the ligandL by formation of N₂ in an exothermic intramolecular redox process under 300?. The central atom is oxidized by NO, and N₂O is formed above 300? in the case of non-reducing ligandsL (OPph₃, OAsph₃). An endothermic redox reaction with chlorine formation is observed during decomposition of the trichloro complex. The solid residue is metallic molybdenum.