Beiträge zum thermischen Verhalten von Sulfaten. II. Zur thermischen Dehydratisierung des ZnSO4 · 7 H2O und zum Hochtemperaturverhalten von wasserfreiem ZnSO4

Contributions to the Thermal Behaviour of Sulfates. II. On the Thermal Dehydration of ZnSO₄ · 7 H₂O and the Effect of High Temperature upon Anhydrous ZnSO₄ The dehydration of ZnSO₄ · 7 H₂O and effect of high temperature upon unhydrous ZnSO₄ was examined by means of continous high temperature Guinier photographs. On heating in air ZnSO₄ · 7 H₂O decomposes stepwise to ZnSO₄ · 6 H₂O, to an unknown hydrate, to the monohydrate and finally to N? ZnSO₄, which is the thermodynamically stable modification at S.T.P. At about 700°C a reversible transformation to H-ZnSO₄ can be observed which can start from N? ZnSO₄ or H-ZnSO₄, proceeds to the oxide sulfate Zn₃O(SO₄)₂ and finally to ZnO. ZnSO₄ · 6 H₂O crystallizes monoclinically in the hexahydrite structure with a_25°C = 9.981 Å, b_25°C = 7.250 Å, c_25°C = 24.280 Å, β_25°C = 98.45°, Z = 8, space group: C 2/c. Cubic H-ZnSO₄ is the first A²⁺B⁶⁺O₄ compound of H-Cristobalit structure; probable space group F 4 3 m with a_700°C = 7.18 Å, Z =4, N-Zn₃O(SO₄)₂ is monoclinic probable space group B 2 with a_25°c=13.987 Å, b_25°c=6.706 Å, c_25°c =7.379 Å β_25°c=90.69°, Z=4, Above 420°C N-Zn₃(SO₄)₂ becomes orthorhombic where at first of all H′-Zn₃O(SO₄)₂ which has a reversible transformation point to H-Zn₃O(SO₄)₂ at 655°C is formed. The probable space group of H-Zn₂O(SO₄)₂ is C 222₁ with a _850°C = 7.36 Å, b_350°C = 13.96 Å, c_850°C = 6.79 Å Z = 4, The solid solution N? Cu_1,5Zn_1,5O(SO₄)₂ is isotypic with N? Zn₃O(SO₄)₂ and has the lattice constants a_25°C = 14.03 Å, b_25°C = 6.62 Å, c_25°C = 7.33 Å, β_25°C = 90.58°, Transoformations into the non quenchable high temperature modifications H-ZnSO₄, H′-Zn₃O(SO₄)₂ and H-Zn₃O(SO₄)₂ are displacive. The thermal expansion of N-ZnSO₄ and H-ZnSO₄ and H-ZnSO₄ has been exa-mined.     

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 thermischen Bildung von Ketenen

Zusammenfassung Das beim Erhitzen von Salicylsäurechlorid (1), Isatosäureanhydrid (2), 2,4-Dioxo-1,3-benzodioxan (4) und ähnlichen Verbindungen auftretende Keten wird über seine Folgeprodukte IR-spektroskopisch nachgewiesen.

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The thermal decomposition of salicyloylchloride (1), isatoic anhydride (2), 2.4-dioxo-1.3-benzodioxane (4) and similar compounds leads to ketenes identified by IR spectroscopic methods. *** DIRECT SUPPORT *** A3615129 00014

     

Zur Untersuchung der thermischen Zersetzungsprodukte von Kohlenhydraten

Ohne Zusammenfassung     

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.     

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 und Sublimation des NiI2

Thermical Decomposition and Sublimation of NiI₂ In a membran manometer the thermical decomposition and the sublimation of NiI₂ was measured and in ampuls the sublimation of NiI₂ studied. From the total pressure and the sublimation pressure the enthalpy of formation ΔH°(f,NiI₂,f,298) = ?20 ± 2 kcal/mole and ΔH°(f,NiI₂,g,298) = +31.2 ± 5 kcal/mole was derived. The entropy dates are: S°(NiI₂,f,298) = 35 ± 2 cl, S°(NiI₂,g,298) = 80 ± 1 cl and S°(Ni₂I₄,g,298) = 128 ± 3 cl respectively. The Ni formed with NiI₂ an eutectical system.     

Zur Photochemie von 2, 1-Benzisoxazolen (Anthranilen) und thermischen und photochemischen Umsetzungen von 2-Azido-acylbenzolen in stark saurer Lösung

On the Photochemistry of 2, 1-Benzisoxazoles (Anthraniles) and on the Thermal and Photochemical Decomposition of 2-Azido-acylbenzenes in Strongly Acidic Solution Anthranils 6 (Scheme 3), when irradiated with a mercury high-pressure lamp, in 96% sulfuric acid yielded, after work-up, 2-amino-5-hydroxy-acylbenzenes 8 and as side products 2-amino-3-hydroxy-acylbenzenes 9 (cf. Schemes 5–7 and Table 1). When C(5) of the anthranils 6 carries a methyl group a more complex reaction mixture is found after irradiation in 96% sulfuric acid (cf. Schemes 8 and 9): 3, 5-dimethyl-anthranil ( 6d ) yielded (after irradiation and acetylation) 2-acetyl- amino-5-methyl-acetophenone ( 15 ), 2-acetylamino-5-acetoxymethyl-acetophenone ( 18d ) and 2-acetylamino-5-acetoxy-6-methyl-acetophenone ( 12c ). The latter product was also formed after irradiation of 3, 4-dimethylanthranil ( 6c ) in 96% sulfuric acid. 3, 5, 7-Trimethyl-anthranil ( 6f ) formed under the same conditions 2-acetylamino-3, 5-dimethyl-acetophenone ( 15f ) and 2-acetylamino-5-acetoxymethyl-3-methyl-acetophenone ( 18f ). Since qualitatively the same product patterns were observed when the corresponding 2-azido-acetophenones 7 were decomposed in 96% sulfuric acid it is concluded that anthranilium ions (cf. 6b -H⊕, Scheme 11) on irradiation are transformed by cleavage of the N, O-bond into 2-acyl-phenylnitrenium ions (cf. 25b -H⊕) in the singlet ground state. The nitrenium ions are trapped directly by nucleophiles ( HSO ?₄ in 96% sulfuric acid), thus, yielding the hydroxy-acetophenones 8 and 9 (Scheme 11). If C(5) is blocked by a methyl group a [1, 2]-rearrangement of the methyl group may occur (cf. Scheme 13) or loss of sulfuric acid can lead to quinomethane iminium ions (cf. 32-H⊕ , Scheme 13) which will react with HSO ?₄ ions to yield, after hydrolysis and acetylation, the 5-acetoxymethyl substituted acetophenones 18d and 18f . It is assumed that the reduction products (2-acetylamino-acetophenones 15 ) are formed from the corresponding nitrenium ions in the triplet ground state.     

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.     

Neubestimmung der Gitterparameter,Dichten und thermischen Ausdehnungskoeffizienten von Silber und Gold,und Vollkommenheit der Struktur

Zusammenfassung Die neu bestimmten Gitterparameter des Ag und Au sinda ₂₅=4,08626±0,00004 (Ag) bzw. 4,07894±0,00005 Å (Au), die Brechungskorrektur+0,00035 einbezogen. Die Dichten beider Metalle sindd ₂₅=10,4976±0,0003 (Ag) bzw. 19,2779±0,0018 (Au) g cm^–3. Die thermischen Ausdehnungskoeffizienten sind _Ag=18.73·10^-6 and _Au=13.4·10^-6°C^-1 zwischen 10 und 65°. Beide Metalle weisen einen vollkommenen Aufbau (innerhalb der Fehlergrenzen) auf.Die vollständige Erholung der reinen, 99,999proz. Metalle von den Folgen der Kaltbearbeitung (Feilen) erfolgt sogar bei Zimmertemperatur: Ag-in ungefähr 24 Stdn., Au-in 5 Tagen. Die Verschiebung (Platzwechsel) der Atome wird stark durch Verunreinigungen verzögert.Der dicht unter dem Schmelzpunkt abgeschreckte Silberkristall zeigte eine geringe Dichte, die beim Tempern zunahm, was durch das Herausdiffundieren von Leerstellen erklärt werden kann.

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Redetermination of lattice parameters, densities and thermal expansion coefficients of silver and gold, and the perfection of their structures

The redtermined lattice parameters of Ag and Au are as follows:a ₂₅=4.08626±0.00004 and 4.07894±0.00005 Å, resp., including the refraction correction of 0.00035; the densities ared ₂₅=10.4976±0.0003 and 19.2779±0.0018 gcm^–3, resp. The thermal expansion coefficients between 10 and 65°C are: _Ag=18.73·10^-6 and _Au=13.4·10^-6°C^-1. Both metals showed a perfect structure (within the error limits).A complete recovery of the 99.999% pure metals from the consequences of cold work (filing) occurred at room temperature in about 24 hr. (Ag) and in 5 days (Au). The displacement of atoms is strongly retarded by the presence of impurities.A silver crystal quenched just below the melting point showed a lower density which increased during the heat treatment. This behavior can be explained by vacancies diffusing out of the crystal.

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Mit 2 Abbildungen

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Herrn Prof. Dr.H. Nowotny gewidmet.

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Mitteilung Nr. 132 aus dem GCMR, Univ. of Mo-Rolla.     

Dehydratisierung von Butanolen an Hartstoffcarbiden

The dehydration of 1-butanol and 2-butanol was studied in a microcatalytic reactor over refractory carbides (except Hf and Cr) in a temperature range between 40 and 500°C. The activity was comparable with that of oxides and salts. Varying the pulse size, the surface coverage — and the amount of reaction products—was found to be in good correlation with aLangmuir adsorption isotherm. Heats of adsorption and activation energies were calculated from experiments at different temperatures, the activation energies, using two different methods with good agreement. The activity of the refractory carbides increased in the periodic table of the elements from the left to the right and from bottom to top, as observed with salt-catalysts.

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Mit 3 Abbildungen

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Auszugsweise vorgetragen bei der 75. Hauptversammlung der Deutschen Bunsengesellschaft für Physikalische Chemie in Saarbrücken, 26. bis 29. Mai 1976.     

Untersuchungen zur Kinetik der thermischen Dissoziation von Nickel-, Kupfer- und Zinksulfat

The rates of decomposition and the energies of activation were determined for the thermal dissociation of NiSO₄, CuSO₄, Cu₂(SO₄)O, ZnSO₄and Zn₃(SO₄)₂O. Linear, parabolic and logarithmic rate laws were found. Kinetics are largely determined by the rate of energy transfer. The reasons for the formation of basic sulfate intermediates are discussed.     

Zur Trennung von Jodid und Perrhenat von Arsenat, Selenat und Tellurat

Ohne Zusammenfassung     

Zur Bestimmung und Trennung von Kalk, Baryt und Strontian

Ohne Zusammenfassung     

Zur Bestimmung von Formaldehyd und Acetaldehyd,

Ohne Zusammenfassung     

Zur Ionenaustausch-Chromatographie von Europium, Yttrium und Promethium

Ohne Zusammenfassung