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.).     

The thermal decomposition of manganese(II) sulphite trihydrate

Thermal studies have shown that manganese(II) oxide and trimanganese tetroxide are the final decomposition products when manganese(II) sulphite trihydrate is heated in nitrogen and oxygen respectively. However, in each atmosphere, there are several decomposition routes involving the intermediate formation of manganese(II) sulphate and manganese(II) sulphide. The reactions can be summarized as follows:

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Zusammenfassung Thermische Untersuchungen haben gezeigt, da\ Mangan(II)oxid und Trimangan-Tetroxid die Endprodukte der Zersetzung sind, wenn Mangan(II)sulfit Trihydrat in Stickstoff bzw. Sauerstoff erhitzt wird. In jeder der AtmosphÄren gibt es jedoch erschiedene Zersetzungswege, wobei vorübergehend Mangan(II)sulfat und Mangan(II)sulfid gebildet werden. Die Reaktionen können, wie folgt, zusammengefa\t werden:

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Résumé Les études thermiques montrent que l'oxyde de manganèse(II) et le tétroxyde de trimanganèse constituent les produits finaux de la décomposition du sulfite de manganèse(II) chauffé respectivement dans l'azote et dans l'oxygène. Cependant dans chacune de ces atmosphères, plusieurs chemins de décomposition peuvent Être suivis. Ils font intervenir la formation intermédiaire de sulfate de manganèse(II) et de sulfure de manganèse(II). Les réactions peuvent Être résumées comme suit:

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, , , , MnO Mn₃O₄. , , - (II). :

     

Thermal decomposition of basic aluminium potassium sulfate. Part III. General regularities of thermal dissociation

Using the method of Bolles and Drago (1) the thermodynamic properties of drug - aromatic amino acid complexes were determined calorimetrically. The comparison of K_c evaluated from vapour pressure osmometry. ORD, partition and calorimetry shows a considerable agreement, whereas the data calculated from solubility measurements differ widely from our results. Qualitatively the relationship between solubilisation through different salts and ΔG⁰ for the complexation with the same salts could be demonstrated. Methylxanthines form complexes with anions and cations, the complex formation in H₂O and D₂O, determined calorimetrically, shows the greater stability of the complexes in D₂O.     

Thermal decomposition mechanism of iron(III) nitrate and characterization of intermediate products by the technique of computerized modeling

The nonahydrate of iron(III) nitrate shows no phase transitions in the range of ?40 to 0 °C. Both hexahydrate Fe(NO₃)₃·6H₂O and nonahydrate Fe(NO₃)₃·9H₂O have practically the same thermal behavior. Thermal decomposition of iron nitrate is a complex process which has a different mechanism than those described for other trivalent elements. Thermolysis begins with the successive condensation of 4 mol of the initial monomer accompanied by the loss of 4 mol of nitric acid. At higher temperature, hydrolytic processes continue with the gradual elimination of nitric acid from resulting tetramer and dimeric iron oxyhydroxide Fe₄O₄(OH)₄ is formed. After complete dehydration, oxyhydroxide is destroyed leaving behind 2 mol of Fe₂O₃. The molecular mechanics method provides a helpful insight into the structural arrangement of intermediate compounds.     

The synthesis and characterization of melamine based Schiff bases and its trinuclear [salen/salophenFe(III)] and [salen/salophenCr(III)] capped complexes

Four new trinuclear Fe(III) and Cr(III) complexes involving tetradentate Schiff bases N, N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophen H₂) with 2,4,6-tris(4-carboxybenzimino)-1,3,5-triazine have been synthesized and characterized by means of elemental analysis, ¹H NMR, FT-IR spectroscopy, LC-MS, thermal analyses and magnetic susceptibility measurements. The complexes have also been characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by COO^? group.     

Studies on the thermal behaviour of tris-[thallium(III)]-lactate

The interaction of TL(OH)₃, with excess lactic acid indicated the formation of Tl(LA)₃ where LA stands for the anion of lactic acid. The structure of the complex was predicted from elemental analyses and IR spectra. The thermal decomposition of the complex using TG, DTG and DTA gave supporting evidence for the predicted structure. The kinetics of thermal decomposition were also studied employing various computational methods.     

Thermal analysis of prednicarbate and characterization of thermal decomposition product

In the present work, the thermal behavior of prednicarbate was studied using DSC and TG/DTG. The solid product remaining at the first decomposition step of the drug was isolated by TG, in air and N₂ atmospheres and was characterized using LC-MS/MS, NMR, and IR spectroscopy. It was found that the product at the first thermal decomposition step of prednicarbate corresponds to the elimination of the carbonate group bonding to C₁₇, and a consequent formation of double bond between C₁₇ and C₁₆. Structure elucidation of this degradation product by spectral data has been discussed in detail.     

Thermal decomposition of silver cyano complex and characterization its decomposition products by ETA,DSC, DTA and TG

It was found by DTA and TG that [Phenyl₂I][Ag(CN)₂] in the solid state is chemically stable on heating in argon up to 160°C. During heating to higher temperatures it decomposes, forming volatile products such as [Phenyl]I, [Phenyl]NC and (CN)₂ [1]. After heating the sample to 500°C metallic silver resulted. The volatile and intermediate solid products were analysed by IR-spectroscopy.It was found by means of DTA and ETA that an isophase reversible transition takes place when the sample is heated and cooled, not higher than 100°C. At heating higher than 100°C the sample melts (melting pointT _m=135°C). The enthalpy melting was determined by means of DSC (H=–28 kJ·mol^–1).By means of ETA the disorder degree of the final decomposition product was estimated. The value of the activation energy of radon diffusion in the temperature range 720°–500°C equals 32.6 kJ·mol^–1.Dedicated to Prof. I. N. Bekman Moscow State University at the occasion of his 50th birthday     

The synthesis and characterization of 2,4,6-tris(3,4-dihydroxybenzimino)-1,3,5-triazine and its [salen/salophenFe(III)] and [salen/salophenCr(III)] capped complexes

Four new trinuclear Fe(III) and Cr(III) complexes involving tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophenH₂) with 2,4,6-tris(3,4-dihydroxybenzimino)-1,3,5-triazine have been synthesized and characterized by means of elemental analysis, ¹H N.M.R., FT-IR spectroscopy, thermal analyses and magnetic susceptibility measurements. The complexes have also been characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by catechol group.     

Thermal decomposition of [bis(salicylaldehydato)cadmium(II)] to CdS nanocrystals

The present investigation reports, the novel synthesis of nanocrystals CdS using thermal decomposition of [bis(salicylaldehydato)cadmium(II)], as a new precursor, and elemental sulfur in oleylamine. The as-synthesized CdS crystals have diameters about 10 nm. The products were characterized by X-ray diffraction (XRD) transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) spectroscopy and Fourier transformed infrared (FT-IR) spectra. The results of this paper show that the shape and size of cadmium sulfide nanocrystals can be controlled systematically by adjusting certain reaction parameters, such as the reactant concentration, the reaction temperature and the reaction time. Cadmium sulfide nanoparticles and nanorods with different lengths have been successfully prepared.     

The thermal and spectral properties of trans-[chloro-bis(dimethylglyoximato)Co(III)] complexes containing heterocyclic donor ligands

The thermal decompositions of the complexes [Co(dmgH)₂(LN)Cl] (where LN: btz, benzotriazole; ind, indole; car, carbazole; qui, quinoline) have been investigated in an atmosphere of static nitrogen in the temperature range 25–1000 °C by means of TG and DTA. Though the complexes are similar but the kinetics of their thermal decompositions are different. The solid intermediate and the resultant products of thermolysis have been identified by means of elemental analysis and spectrometrical data. The schemes of destruction of these complexes are suggested. On heating, these compounds first release halogen part, then heterocyclic nitrogen ligand and finally dimethylglyoxime. The final product of the thermal decomposition was Co₃O₄ for the complexes I–IV. According to the decomposition temperature, the thermal stability of the complexes can be ordered in the sequence: III>II>IV>I. By means of IR spectral analysis, the stereochemistry around Co(III) ion in the compounds have been studied. The btz, ind, car and qui were coordinated to Co(III) through the nitrogen atom of their heterocyclic ring and the chloride ion is coordinated to central metal ion.     

Chemiluminescence in the thermal decomposition of di(tert-butyl) trioxide

Intense chemiluminescence (CL) in the visible and IR regions arising during the thermal decomposition of di(tert-butyl) trioxide has been observed. The decomposition rate constants have been determined. The emitter of CL in the IR region is singlet oxygen, that of CL in the visible region is triplet excited acetone. Kinetic and spectral data and thermochemical and MNDO calculations point to a homolytic mechanism of decomposition. The formation of the CL emitters occurs in the reactions of radicals that arise upon the decay of di(tert-butyl) trioxide.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2056–2059, December, 1993.     

Preparation,characterization and thermal decomposition of phenylenediammonium sulfate salts Part. XVI

Polyaniline/α-Al₂O₃ (PANI/α-Al₂O₃) composites were synthesized by in situ polymerization through ammonium persulfate ((NH₄)₂S₂O₈, APS) oxidized aniline using HCl as dopant. XRD and FTIR were used to characterize the PANI/α-Al₂O₃ composites. The thermal stabilities and glass transition temperature (T _g) of PANI/α-Al₂O₃ composites were tested using thermogravimetric (TG) method and modulated differential scanning calorimetry (MDSC) technique. The results of TG showed that the thermal stability of PANI/α-Al₂O₃ composite increased and then decreased with the increase in α-Al₂O₃ content. The derivative thermogravimetry (DTG) curves showed one step degradation of PANI when the α-Al₂O₃ content was lower than 52.5 mass%, and exhibited two steps degradation when the α-Al₂O₃ content was higher than 63.6 mass%. The MDSC curves showed that the T _g of PANI/α-Al₂O₃ composites increased and then decreased with the augment of α-Al₂O₃ for the interaction between PANI chains and the surface of α-Al₂O₃.     

Thermal decomposition products of dihydroahtemisinin (dihydroqinghaous)

Dihydroartemisinin (2), a sodium borohydride reduction produot of artemisinin (1), undergoes themolysis at 190 °C to give desoxyartemisinin (3) and a preponderant decomposition product (4) consisting of 2 epimers 4a, (2S, 3R, 6S)-2-(3-oxobutyl)-3-methyl-6-[(R)2-propanal]-cyclohexanone, and 4b, (2S, 3R, 6R)-2-(3-oxobutyl)-3-methyl-6-[(R)2-propanal]-cyclohexanone.     

Thermal decomposition of cerium(III) perchlorate

Thermal decomposition of Ce(ClO₄)₃ ? 9H₂O and Ce(ClO₄)₃ to give cerium(IV) dioxide in the temperature range 240–460°C was studied by DSC–TGA, X-ray powder diffraction, IR and mass spectroscopy. The thermolysis of these salts was shown to proceed through the stage of formation of intermediate product supposedly cerium oxoperchlorate. The thermal decomposition of cerium(III) perchlorate hydrate at 460°C leads to formation of nanocrystalline cerium dioxide with particle size of 13 nm.     

Thermal decomposition of ammonium fluoromanganates(III)

The thermal decomposition of ammonium fluoromanganates (III) has been investigated in air and argon by simultaneous thermogravimetry and differential thermal analysis. Chemical analysis, X-ray powder data, and infrared spectra have been employed to characterise the intermediate and final products. The thermal decomposition can be described by the sequence (NH₄₃MnF₆ → (NH₄)₂MnF₅ → NH₄MnF₄ → MnF₂. Although penta- and tetra-fluoromanganates are well-defined compounds, the intermediate states could not be separated. In addition, a high temperature form of ammonium hexafluoromanganate has been observed.     

Thermal decomposition of Cr(III) dithiocarbamates

The thermal stability of chromium(III) complexes with dithiocarbamate acid derivatives was studied. The general formula of these complexes is (RCS₂)₃Cr where: The thermal stability of these complexes was found to depend on the kind ofR and the decomposition occur in several stages.The final product of the decomposition of the complexes in the 20–600 temperature range investigated is chromium sulphide, Cr₂S₃ or with incomplete combusted sulfur atoms.

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Zusammenfassung Die Thermostabilität von Chrom(III)-Komplexen mit sauren Derivaten von Dithiocarbamat wurde untersucht. Die allgemeine Formel dieser Komplexe ist (RCS₂)₃Cr. Es wurde festgestellt, da\ die Thermostabilität dieser Komplexe von der Art von R abhängt und die Zersetzung in mehreren Stufen verläuft.Das Endprodukt der Zersetzung der Komplexe im untersuchten Temperaturbereich von 20 bis 600 ist Chromsulfid, Cr₂S₃, oder solches mit überschüssigem Schwefel.

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Résumé On a étudié la stabilité thermique des complexes du chrome(III) avec les dérivés de l'acide dithiocarbamique. La formule générale de ces complexes est (RCS₂)₃Cr où: On a trouvé que la stabilité thermique de ces complexes dépendait de la nature du radical et que la décomposition se déroulait en plusieurs étapes.Dans l'intervalle de température étudié, de 20 à 600, le produit final de la décomposition des complexes est le sulfure de chrome, Cr₂S₃, éventuellement accompagné de soufre résultant d'une combustion incomplÊte.

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(III) - . — (RCS₂)₃ Cr, , R . 20–600 Cr₂S₃ .

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The autors would like to thank Doc. dr h. J. F. Biernat for valuable discussions.     

Thermal decomposition of hexamminecobalt(III) chloride

The results of comparative thermal analysis (TG-DTG-DTA-DSC) of the thermal decomposition of hexamminecobalt(III) chloride in air atmosphere are reported. The kinetics and mechanism of the thermal decomposition, the process enthalpy and the variation in specific thermal capacity of the solid product reaction with temperature were determined.     

Thermal decomposition of hexamminechromium (III) chloride

In this paper the results of comparative thermal analysis TG-DTG-DTA-DSC for the thermal decomposition process of [Cr(NH₃)₆]Cl₃ in air atmosphere are given. The kinetics and mechanism of this complex thermal decomposition, process enthalpy as the changes of specific thermal capacity of solid products reaction with temperature were determined.

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Zusammenfassung Es werden die Ergebnisse einer vergleichenden Thermoanalyse TG-DTG-DTA-DSC des thermischen Zersetzungsprozesses von [Cr(NH₃)₆]Cl₃ in Luft dargelegt. Weiterhin wurde die Kinetik und der Mechanismus dieses komplexen thermischen Zersetzungsprozesses, die Enthalpie des Vorganges sowie die temperaturbedingten Änderung der WÄrmekapazitÄt dieser Festkörperreaktion bestimmt.