The thermal decomposition of aqueous manganese (II) nitrate solution

The thermal decomposition of commercially available aqueous solutions of manganese(II) nitrate was investigated using the conventional thermal analytical techniques of thermogravimetry (TG), differential thermal analysis (DTA), and evolved gas analysis (EGA). Infrared spectra and X-ray diffraction patterns were used to help characterize intermediate species.     

Thermal decomposition of potassium hexacyanoferrate(II) trihydrate

Potassium hexacyanoferrate(II) trihydrate, K₄Fe(CN)₆·3H₂O, was heated under controlled conditions of mass and rate in a derivatograph in the presence of oxygen. The heating was stopped at different temperatures and Mössbauer spectra and X-ray diffractograms were taken on the quenched material at room temperature. The reaction pathway was studied in this way and the advantages and drawbacks of each of the techniques are described. At different stages of the thermal process we were able to show the presence of K₄Fe(CN)₆,-Fe₂O₃, Fe₃O₄, Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ and KCN.

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Zusammenfassung Kaliumhexacyanoferrat(II)trihydrat, K₄[Fe(CN)₆.3H₂O wurde unter kontrollierten Bedingungen in einem Derivatographen in Gegenwart von Sauerstoff erhitzt. Das Aufheizen wurde bei verschiedenen Temperaturen gestoppt und Mössbauer-Spektren, sowie Röntgendiffraktogramme aufgenommen. Der Reaktionsweg wurde auf diese Weise untersucht und die Vor- und Nachteile jeder der Techniken beschrieben. Bei den verschiedenen Stufen des thermischen Vorganges konnten K₄[Fe(CN)₆],-Fe₂O₃, Fe₃O₄, Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ und KCN nachgewiesen werden.

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Resumé Le ferrocyanure de potassium trihydraté, K₄Fe(CN)₆·3H₂O, a été chauffé en présence d'oxygÊne dans un Derivatograph, dans des conditions bien déterminées de masse et de vitesse de chauffage. Le chauffage a été interrompu à diverses températures et les spectres Mössbauer ainsi que les diffractogrammes de rayons X ont été enregistrés aprÊs trempe du matériau à la température ambiante. On a étudié de cette faÇon le déroulement de la réaction; on décrit les avantages et les inconvénients de chacune de ces techniques. On a pu déceler la présence de K₄Fe(CN)₆,-Fe₂O₃, Fe₃O₄ Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ et KCN aux différentes étapes du traitement thermique.

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- (II)- -₄F/)₆. 3₃- . . . K₄Fe(CN)₆, -Fe₂O₃, Fe₃O₄, Fe₃C, Fe, FeO, KFeO₂,-FeOOH, KOCN, K₂CO₃ KCN.

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This research was performed with financial support from the Conselho Nacional de Desenvolvimento Científico e TecnolÔgico (CNPq) and Financiadora de Estudos e Projetos (FINEP). We are grateful to Profs. A. Bristoti, J. Danon, P. J. Aymonino, E. Baran and M. A. Blessa for valuable suggestions and criticisms, and Miss E. A. Veit for performing the thermal measurements at the Pontificia Universidade Católica, Porto Alegre. This work was submitted in partial fulfilment of the conditions for the degree of Livre Docente by one of us (J. I. K.).     

Thermal decomposition of copper(II) glutarate trihydrate. Part I. The mechanism of dehydration of copper(II) glutarate trihydrate

The mechanism of thermal dehydration of copper(II) glutarate trihydrate has been determined from the analysis of the kinetic data for isothermal and non-isothermal dehydration experiments. Microscopic investigations for the dehydration process of a single crystal of copper(II) glutarate trihydrate have been carried out to support the mechanism. The simultaneous DTG—DTA—TG curves of the salt are also described.     

Application of thermogravimetric equations in the thermal decomposition of manganese(II) soaps

Summary Thermal decomposition of manganese(II) soaps of general composition, Mn(O₂CR)₂ (where R = C₁₇H₃₃, C₁₁H₂₃, C₉H₁₉, C₇H₁₅) has been studied by t.g.a. and a probable mechanism of decomposition is proposed. The activation energies have been determined using the different equations of Horowitz and Metzger and of Coats and Redfern. The results obtained are consistent.     

Kinetics of thermal decomposition of manganese(ii) oxalate

The kinetics of manganese(II) oxalate thermal decomposition in the helium atmosphere was studied on the basis of isothermal measurements in the temperature range from 608 to 623 K. Manganese(II) oxide, MnO, was found to be the final product of reaction. The Avrami-Erofeev kinetic equation was used to describe all the experimental data in the range of decomposition degrees from 0.1 to 0.9. The determined activation energy equals 184.7 kJ mol^-1 with standard deviation ±5.2 kJ mol^-1. The estimated value of parameter n is 1.9 with standard deviation ±0.01 what suggests that the rate limiting step of MnC₂O₄ decomposition is the nucleation of new MnO phase and that the rate of nuclei growth is rising during decomposition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and crystal structure of aquachlorobis(1,10-phenanthroline)manganese(II) nitrobenzoate trihydrate

The title compound has been prepared and its crystal structure determined by X-ray diffraction methods. The complex salt consists of Mn(II) complex cations, benzoate anions and lattice water molecules. Mn(II) assumes a distorted octahedral geometry defined by two 1,10-phenanthroline (phen) ligands, a Cl^? ion and a water molecule. A comparison of bond distances and bond angles suggests electrostatic interaction between Mn(II) and coordinated N atoms. The nitrobenzoate anion does not coordinate to the Mn atom but links with the complex cation via O?H···O hydrogen bonds. Aromatic stacking occurs between phen rings and between phen and benzoate.     

Thermal decomposition of manganese(II)bis(oxalato)nickelate(II)tetrahydrate

Summary A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn₂O₃, MnO₂ and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.     

Thermochemistry of decomposition of manganese(II) oxalate dihydrate

Differential scanning calorimetry (DSC) has been used to determine the enthalpy of dehydration of manganese(II) oxalate dihydrate and the enthalpies of decomposition in nitrogen and in oxygen of the anhydrous oxalate. The thermodynamic data have been related to the activation energies reported in kinetic studies and to the mechanisms proposed for the thermal decomposition and oxidation processes.     

The thermal decomposition of platinum(II) and (IV) complexes

The decomposition characteristics of Pt(II) and Pt(IV) complexes in hydrogen, air and argon were investigated by thermal gravimetric and differential thermal analysis. Based on weight-loss measurements, the thermal stability in hydrogen increased in the order: hexachloroplatinic acid<platinum acetyl acetonate<platinum diamino dinitrite<tetrammine platinous hydroxide<tetrammine platinous chloride<platinum phthalocyanine; whereas in air, the order was: hexachloroplatinic acid<tetrammine platinous hydroxide<platinum acetyl acetonate<platinum diamino dinitrite<tetrammine platinous chloride. The platinum complexes were more stable in air than in hydrogen where decomposition was observed in all platinum samples at temperatures below 200°C.     

Thermal decomposition kinetics of bis(pyridine)manganese(II) chloride

The thermal stability and the decomposition steps of bis(pyridine)manganese(II) chloride (Mn(py)₂Cl₂) were determined by thermogravimetry and derivative thermogravimetry. The initial compound and the solid compounds resulted from each step of decomposition were characterized by FT-IR spectroscopy and RX diffraction. It was pointed out that at the progressive heating of Mn(py)₂Cl₂, the following decomposition reactions occur: I $$ {\text{Mn}}\left( {\text{py}} \right)_{ 2} {\text{Cl}}_{ 2} \left( {\text{s}} \right) \, \to {\text{ Mn}}\left( {\text{py}} \right){\text{Cl}}_{ 2} \;\left( {\text{s}} \right) \, + {\text{ Py }}\left( {\text{g}} \right) $$ II $$ {\text{Mn}}\left( {\text{py}} \right){\text{Cl}}_{ 2} \left( {\text{s}} \right) \, \to {\text{ Mn}}\left( {\text{py}} \right)_{ 2/ 3} {\text{Cl}}_{ 2} \;\left( {\text{s}} \right) \, + { 1}/ 3 {\text{ Py }}\left( {\text{g}} \right) $$ III $$ {\text{Mn}}\left( {\text{py}} \right)_{ 2/ 3} {\text{Cl}}_{ 2} \left( {\text{s}} \right) \, \to {\text{ MnCl}}_{ 2} \left( {\text{s}} \right) \, + { 2}/ 3 {\text{ Py }}\left( {\text{g}} \right) $$ The dependence of the activation energy of these decompositions steps on the conversion degree, evaluated by isoconversional methods, shows that all decomposition reactions are complex. The mechanism and the corresponding kinetic parameters of reaction (I) were determined by multivariate non-linear regression program and checked for quasi-isothermal data. It was pointed out that the reaction (I) consists of three elementary steps, each step having a specific kinetic triplet.     

Hexaaquazinc(II) dipicrate trihydrate

In the crystal structure of the title compound, [Zn(H₂O)₆](C₆H₂N₃O₇)₂·3H₂O, the zinc cation complexes and picrate anions are stacked separately, extending along the b axis. No picrate species ligate to the metal cation. This lack of picrate coordination is atypical among metal picrate salts. We speculate that the size of the metal–aqua complex as related to the intermolecular distance of the picrate anions in the π stack can be a measure of the formation of such separated stacks in the crystal structures of divalent metal complexes with picrate anions. Picrate ions are linked to each other with short intermolecular C...C contacts of 3.223 (6) and 3.194 (6) Å in the stack.     

The doping effect of altervalent cations on the thermal decomposition and electrical conduction properties of manganese(II) carbonate

The electrical conductivities of pure and doped manganese(II) carbonate with 10 mol% Li⁺ or Al³⁺ ions were measured. The effect of doping on the observed kinetic parameters of decomposition were measured. Doping with Li⁺ or Al³⁺ ions enhances the decomposition. The enhanced promotion effect is ascribed to the generation of hole defects which are concentrated at the reaction interface. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Thermal decomposition of hydrated iron(II) oxalate and manganese(II) oxalate in vacuum

The thermal decomposition of hydrated iron(II) oxalate and manganese(II) oxalate under high vacuum conditions (10^–5 mm Hg) has been studied by differential thermal analysis. The decomposition in vacuum of iron(II) oxalate is exothermic, while that of manganese(II) oxalate is endothermic. An explanation is offered for this behaviour.The financial support by National Bureau of Standards, U.S.A., through a PL-480 scheme is gratefully acknowledged.     

Kinetic parameters of thermal decomposition of nitritocuprates (II)

Kinetic parameters of thermal decomposition of compounds of the general formula M ₂ ^I M^II[Cu(NO₂)₆] (where M^I=K⁺, Rb⁺ or Cs⁺; and M^II=Ca²⁺, Sr²⁺, Ba²⁺ or Pb²⁺) and K₂Pb[X(NO₂)₆] (where X=Co²⁺, Ni²⁺, Zn²⁺) are determined from the corresponding thermal curves. The order of reaction (n) and the activation energy (E _a) are derived. The kinetic data is discussed in terms of the effects of outer sphere cations and the central ion on the activation energy.

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Zusammenfassung Die kinetischen Parameter der thermischen Zersetzung von Verbindungen des allgemeinen Typs M ₂ ^I M^II[Cu(NO₂)₆] (M¹=K⁺, Rb⁺ oder Cs⁺; M^II=Ca²⁺, Sr²⁺, Ba²⁺ oder Pb²⁺) bzw. K₂Pb[X(NO₂)₆] (X=Co²⁺, Ni²⁺, Zn²⁺) werden aus den entsprechenden thermischen Kurven bestimmt. Die Reaktionsordnung (n) und die Aktivierungsenergie (E _a) werden abgeleitet. Die kinetischen Parameter werden hinsichtlich der Effekte der Kationen in der Äu\eren SphÄre und des zentralen Ions auf die Aktivierungsenergie diskutiert.

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Résumé Les paramètres cinétiques de la décomposition thermique des composés de formule générale M ₂ ^I M^II[Cu(NO₂)₆] où M^I=K⁺, Rb⁺ ou Cs⁺ et M^II=Ca²⁺, Sr²⁺, Ba²⁺ ou Pb² + et K₂Pb[X(NO₂)₆] où X=Co²⁺, Ni²⁺, Zn²⁺ ont été déterminés à partir des courbes thermoanalytiques correspondantes. L'ordre de réaction (n) et l'énergie d'activation (E _a) ont été calculés. Les effets des cations de la sphère externe et ceux de l'ion central sur l'énergie d'activation sont discutés.

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M ₂ ^I M^II[Cu(NO₂)₆, ^I=⁺, Rb⁺ Cs⁺; ^II=C²⁺, Sr²⁺, ^{2+ 2+}, K₂Pb[X(NO₂)₆], X=²⁺ Ni²⁺; Zn²⁺. (n) (E _a ). .

     

Synthesis of nanocrystalline zinc manganese oxide by thermal decomposition of new dinuclear manganese(III) precursors

Nanocrystalline manganese-doped zinc oxide was synthesized by thermal decomposition of a zinc oxide sol with two new dinuclear manganese(III) complexes as precursor. Thermal analysis results indicated that the decomposition of manganese precursors occurred at 269 and 314 °C. X-ray structural analysis shows the presence of dimanganese core in the complexes and the binding of the ligands to the manganese(III) is through N₂O₂. The manganese-doped zinc oxide composite was characterized by means of X-ray diffraction, scanning electron microscopy, and UV–Vis spectroscopy. Structural properties of the composites elucidated that the manganese ions have substituted the zinc ions without changing the wurtzite structure of zinc oxide.     

Solid-phase thermal decomposition of polynuclear nickel(II) and cobalt(II) complexes

Solid-phase thermal decomposition of polynuclear Ni^II and Co^II pivalate complexes was studied by differential scanning calorimetry and thermogravimetry. The decomposition of the polynuclear (from bi-to hexanuclear) Co^II carboxylate complexes is accompanied by aggregation to form a volatile octanuclear complex. Thermolysis of the polynuclear NiII carboxylates results in their destructure, and the phase composition of the decomposition products is determined by the nature of coordinated ligands. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 250—260, February, 2006.