Thermal analysis of iron(II) sulphate heptahydrate in air

Iron(II) sulphate hydrates (hexa- through mono-) have been prepared and their thermal decomposition behaviours have been studied in air by isothermal and dynamic thermal analysis methods. The results show that their behaviours are similar to that of the heptahydrate. The stepwise loss of water molecules is accompanied by oxidation. Under a restricted supply of oxygen, the anhydrous sulphate is oxidized directly to Fe₂O(SO₄)₂ without the formation of Fe(OH)SO₄. When free exchange with oxygen is allowed, Fe(OH)SO₄ is formed, which in turn decomposes to Fe₂O(SO₄)₂. The decomposition of Fe₂(SO₄)₂ to iron(III) oxide and sulphur oxides appears to occur via two independent paths — one direct and other through iron(III) sulphate.     

Thermal analysis of iron(II) sulphate heptahydrate in air. V

The thermal decomposition of the hydroxysulphate and oxysulphate of iron(III) was carried out in air. Under dynamic conditions, the hydroxysulphate decomposes to the oxysulphate, which in turn decomposes to iron(III) oxide and sulphur oxides. The oxysulphate decomposes directly to iron(III) oxide and sulphur oxides. The heats of decomposition and heats of formation of the two basic sulphates were calculated.     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of (basic) beryllium carbonate

Iron(II) sulphate heptahydrate undergoes decomposition in the presence of basic beryllium carbonate without any interaction with the carbonate. The components of the mixture decompose individually. Iron(II) sulphate decomposes with the formation of tetrahydrate, monohydrate, anhydrous salt, oxysulphate and ferric sulphate as intermediate phases. The basic beryllium carbonate decomposes to the oxide with BeO·BeCO₃ as the intermediate compound.

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Zusammenfassung In Gegenwart von basischem Berylliumcarbonat zersetzt sich Eisen(II)-sulfat-Heptahydrat, ohne mit dem Carbonat in Wechselwirkung zu treten. Die Komponenten des Gemisches zersetzen sich individuell. Die Zersetzung des Eisen(II)-sulfats verläuft über die Zwischenphasen Tetrahydrat, Monohydrat, wasserfreies Salz, Oxysulfat und Eisen(III)-sulfat. Das basische Berylliumcarbonat wird über die intermediäre Verbindung BeO·BeCO₃ in das Oxid überführt.

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, . . , , , . .₃.

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The authors are grateful to Dr. B. R. Sant for his keen interest and useful suggestions throughout this work. They also express their sincere thanks to Prof. P. K. Jena, Director, for his kind permission to publish the results. One of us (MSRS) thanks the Director for a Senior Fellowship.     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of basic magnesium carbonate

Results on the thermal decomposition of iron(II) sulphate heptahydrate in the presence of basic magnesium carbonate are presented and discussed. These results are compared with those for the mixture of iron(II) sulphate heptahydrate with basic beryllium carbonate. While no reaction occurs between the components in the case of basic beryllium carbonate, basic magnesium carbonate reacts readily with iron(II) sulphate heptahydrate.

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Zusammenfassung Bei der in Gegenwart von basischem Magnesiumcarbonat erfolgten thermischen Zersetzung von Eisen(II)-sulfat-Heptahydrat erhaltene Ergebnisse werden beschrieben, diskutiert und mit denen verglichen, die in Gegenwart von Berylliumcarbonat erhalten wurden. Im Gegensatz zu basischem Berylliumcarbonat reagiert basisches Magnesiumcarbonat mit Eisen(II) sulfat-Heptahydrat.

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. . , , .

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The author gratefully acknowledges the support extended by Professor P. K. Jena, Director of this laboratory, and the permission to publish the results.     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of calcium,strontium and barium carbonates

The thermal decomposition in air of iron(II) sulphate heptahydrate in the presence of calcium, strontium and barium carbonates has been carried out. The decomposition path varies from carbonate to carbonate. Also, these decompositions are different from those of basic beryllium carbonate and basic magnesium carbonate. The results obtained for the kinetics of thermal decomposition have also been presented.     

Thermal decomposition of sulphate complexes of uranium(IV) hydrates

A study was made of the thermal decompositions of the hydrates of 5 neutral sulphate complexes and 5 hydroxy-sulphate complexes of uranium(IV). The hydrates did not yield corresponding stable anhydrous compounds. After dehydration, the complexes decomposed in endothermic reactions involving progressive substitution of sulphur trioxide (that is liberated) by oxygen, giving oxy-sulphates and other compunds.     

Thermal decomposition of iron(II) sulphate heptahydrate in the presence of alkali metal carbonates

The thermal decomposition of iron(II) sulphate heptahydrate was carried out in air under dynamic conditions in the presence of lithium, sodium, potassium and rubidium carbonates. The decomposition path in the presence of lithium carbonate differs from that in the presence of the other carbonates. In the presence of lithium carbonate, the heptahydrate loses all the water molecules before entering into reaction with the carbonate. The anhydrous sulphate then reacts with the carbonate, presumably to form iron(II) carbonate, which in turn undergoes decomposition — oxidation via magnetic oxide to ferric oxide. In the case of the other carbonates, iron(II) sulphate enters into reaction with the carbonate in question even before dehydration is complete, to form ferrous carbonate, which in turn reacts with the moisture still present to form green iron(II) hydroxide. This compound then undergoes decomposition — oxidation reactions via magnetic oxide to ferric oxide.

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Zusammenfassung Die thermische Zersetzung von Eisen(II)-sulfat-Heptahydrat wurde in Luft unter dynamischen Bedingungen in Gegenwart von Lithium-, Natrium-, Kalium und Rubidiumcarbonat ausgeführt. In Gegenwart von Lithiumcarbonat verläuft die Zersetzung auf einem anderen Wege als in Gegenwart der anderen untersuchten Carbonate. In Gegenwart von Lithiumcarbonat verliert das Heptahydrat alle Wassermoleküle, bevor es mit dem Carbonat in Reaktion tritt. Das wasserfreie Sulfat reagiert mit dem Carbonat vermutlich unter Bildung von Eisen(II)-carbonat, das oxydativ über Magnetit zu Eisen(III)-oxid zersetzt wird. Im Falle der anderen Carbonate tritt Eisen(II)-sulfat mit dem betreffenden Carbonat noch vor der völligen Beendigung der Dehydratation unter Bildung von Eisen(II)-carbonat in Reaktion, das daraufhin mit noch vorhandenem Wasser zu grünem Eisen(II)-hydroxid weiterreagiert. Diese Verbindung zersetzt sich oxydativ über Magnetit zu Eisen(III)-oxid

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, , . . . , , - . , , . .

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The authors express their sincere thanks to Dr. B. R. Sant for his keen interest in this work and for his valuable suggestions. They also express their gratitude to Professor P. K. Jena, Director, for his permission to publish the results. One of us (MSRS) also thanks the Director for a Senior Fellowship.     

Thermal decomposition of thorium(IV) benzenedicarboxylates in air atmosphere

The conditions of thermal decomposition of Th(IV) benzenedicarboxylates have been studied. On heating, thorium(IV) phthalate and isophthalate are dehydrated and the anhydrous complexes decompose to ThO₂ with intermediate formation of a mixture of ThOCO₃ and carbon.Th(IV) terephthalate obtained at room temperature loses crystal water and then decomposes directly to ThO₂, while the complex isolated from a hot solution on heating is first dehydrated, and the anhydrous complex is decarboxylated and then decomposed to ThO₂ with the intermediate formation of ThOCO₃.The activation energies of dehydration have been calculated for the Th(IV) benzenedicarboxylates.

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Zusammenfassung Die Bedingungen der thermischen Zersetzung von Th(IV)-benzendicarboxylaten wurde untersucht. Thorium(IV)-phthalat und- isophthalat werden beim Erhitzen zunÄchst dehydratisiert, danach zersetzen sich die wasserfreien Komplexe über ein intermediÄr auftretendes Gemisch von ThOCO₃ und Kohlenstoff zu ThO₂. Bei Raumtemperatur erhaltenes Th(IV)-terephthalat verliert Wasser und zersetzt sich dann direkt zu ThO₂, wÄhrend der aus einer hei\en Lösung isolierte Komplex nach der als erster Schritt verlaufenden Dehydratisierung zunÄchst decarboxyliert wird und sich dann über ThOCO₃ als Zwischenprodukt zu ThO₂ zersetzt. Die Aktivierungsenergien der Dehydratisierung der Th(IV)-benzendicarboxylate wurden berechnet.

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. , ThO₂ ThOCO₃ . , , , ThO₂. , , , , H₂ ThOCO₃ . .

     

Thermal decomposition of bishydrazinocarboxylate iron(II) di-hydrazinate

Low temperature (T<200°C) thermal decomposition in air of bishydrazinocarboxylate iron(II) dihydrazinate [Fe(II)(N₂H₃COO)₂(N₂H₄)₂] is known to produce-Fe₂O₃ in ultrafine form [1–4]. This decomposition process is known to be exothermal and autocatalytic but details regarding the stepwise mechanism of decomposition is yet unknown although a few attempts have been made with limited success [1, 5]. In our present work, we have combined the results from (i) thermal analysis of complex precursor and (ii) characterization of products isolated at intermediate and final stages of decomposition in order to explain the stepwise mechanism of decomposition of Fe(N₂H₃COO)₂(N₂H₄)₂ in air.

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Zusammenfassung Mittels DTA/TG/DTG, XRD sowie IR wurde die thermische Zersetzung von Bis-hydrazinocarboxylat-eisen(II)-dihydrazinat untersucht. Die thermische Zersetzung verläuft in sechs Schritten und endet bei genügend niedriger temperatur mit der Bildung von-Fe₂O₃. Durch Auswertung der Untersuchungsdaten konnten die einzelnen Zwischenprodukte, darunter eine neuartige Verbindung FeO₂.2CO, identifiziert werden.

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NCL Communication No. 4613.

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One of us (KBG) wishes to thank the Council of Scientific and Industrial Research for the award of the senior research fellowship. We are grateful to Dr. P. Ratnasamy for his continuing interest in our work.     

Thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere

The conditions of thermal decomposition of copper(II) benzenetricarboxylates in air atmosphere at heating rates of 10 and 5 deg·min^–1 were studied. At 10 deg · min^–1, the hemimellitate and trimesinate of copper(II) lose crystallization water and then decompose directly to CuO, whereas at 5 deg·min^–1 they decompose to CuO through Cu₂O. The trimellitate of copper(II) heated at various rates decomposes in the same way: it loses 1 water molecule and then decomposes directly to CuO.     

Thermal decomposition of thorium(IV) complexes with benzenecarboxylic acids in air atmosphere

The conditions and products of thermal decomposition of thorium(IV) complexes with general formula Th(R-C₆H₄COO)₄ (whereR=2-CH₃, 3-CH₃, 4-CH₃), Th(OH)₂(4-CH₃C₆H₄COO)₂. H₂O and Th(OH)₂(R-C₆H₄COO)₂·nH₂O (whereR=2-COO, 3-COO,n=2;R=4-COO,n=1) were studied. Anhydrous thorium(IV) complexes decompose in two steps. On heating, tetra(2-methylbenzoato)-thorium(IV) decomposes to yield ThO₂ through the intermediate ThOCO₃ whereas tetra(3-methylbenzoato)thorium(IV) and tetra(4-methylbenzoato)thorium(IV) decompose to ThO₂ through oxocomplexes. Hydrated thorium(IV) complexes are dehydrated in one step and then anhydrous complexes decompose to ThO₂. Di [1,2-(benzene)dicarboxylato]dihydroxythorium(IV) decomposes directly to ThO₂, whereas the 1,3- and 1,4-isomers through the intermediate thorium(IV) oxocarbonates.     

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.     

Thermal decomposition of thorium(IV) salts of benzene carboxylic acids in air atmosphere

The thermal stabilities of thorium(IV) salts of ortho-, meta- and para-hydroxy- and aminobenzoic acids were studied. The salts were prepared as hydrated compounds with general formula Th(OH)₂(R-C₆H₄COO)₂·nH₂O, wereR = OH or NH₂, andn = 2, 3 or 4, while the salt of 3-aminobenzoic acid was anhydrous. On heating, the salts undergo dehydration in two or three steps and di(R-benzoato)dihydroxothorium(IV) or di(2-hyroxybenzoato)oxothorium(IV) is then transformed directly to ThO₂.The temperatures of beginning of decomposition and ThO₂ formation decrease with decreasing values of the Hammett constant and von Bakkum constant ⁿ.

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Zusammenfassung Es wurde die Thermostabilität der Thorium(IV)-salze von ortho-, meta- und para-Hydroxy- und Aminobenzoylsäure untersucht.Die Salze wurden als hydratierte Verbindungen der allgemeinen Formel Th(OH)₂(R-C₆H₄COO)₂·nH₂O mitR=OH oder NH₂ undn=2,3 oder 4 gefertigt, während das Salz der 3-Aminobenzoylsäure unhydratiert war. Beim Erhitzen zeigen die Salze eine Dehydratation in zwei oder drei Stufen und anschließend werden Di(R-benzoato)dihydroxothorium(IV) oder Di(2-hydroxybenzoato)oxothorium(IV) direkt in ThO₂ umgewandelt.Die Temperaturen für das Einsetzen der Zersetzung und der ThO₂-Bildung sinken mit abnehmenden Werten für die Hammet-Konstante und die Bakkum-Konstante

     

Thermal decomposition of cesium hexanitratouranium(IV)

As cesium hexanitratouranium(IV), Cs₂U(NO₃)₆, has the same Cs:U stoichiometry as that of Cs₂UO₄, thermal decomposition of this nitrato complex in air and nitrogen was studied in detail as a possible alternate method of preparing pure Cs₂UO₄. The volatility of cesium nitrate, which is one of the intermediate products, changed this Cs:U ratio during thermal decomposition. Hence, only Cs₂U₂O₇ was obtained on heating the sample to 775 K or higher. A scheme for the thermal decomposition of Cs₂U(NO₃)₆ is given by combining the observed TG, XRD and IR data.     

Mössbauer studies of the thermal decomposition of iron(II) ammonium sulphate hexahydrate

The thermal decomposition of binary copolymers of acrylonitrile with variable amounts of -methylstyrene (2–40%) has been studied atp=10^–2–10^–4 torr andT=0–600°. The decomposition products (solids, liquids and gases) have been characterized by IR and UV spectroscopy, gas chromatography, vapor pressure osmometry and elemental analysis. The decomposition mechanism has been ascertained on the basis of the obtained results.

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Zusammenfassung Die thermische Zersetzung der binären Kopolymere von Akrylnitril mit verschiedenen Mengen von -Methylstyrol (2–40%) wurde beip=10^–2–10^–4 Torr undT=0–600° untersucht. Die Zersetzungsprodukte (Festkörper, Flüssigkeiten und Gase) wurden durch IR- und UV-Spektroskopie, Gaschromatographie, Dampfdruck-Osmometrie und Elementaranalyse charakterisiert. Der Zersetzungsmechanismus wurde an Hand der erhaltenen Ergebnisse bestätigt.

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Résumé On a étudié la décomposition thermique des copolymères binaires de l'acrylonitrile avec des quantités variables d'-méthylstyrène (2–40%), àp=10^–2–10^–4 torr etT=0–600°. Les produits de décomposition (solides, liquides et gaz) ont été caractérisés par spectroscopie IR et UV, Chromatographie en phase gazeuse, osmométrie sous pression de vapeur et analyse élémentaire. Le méchanisme de décomposition a été établi à partir des résultats obtenus.

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(2–40%) - p=10^–2–10^–4 =0–600°. (, ) - - , , . .

     

Thermal decomposition of bis(dimethylglyoximate) iron(II) complexes containing axial N-heterocyclic ligands

A systematic TG and DTG study of the thermal decomposition of a series of bis(dimethylglyoximate)iron(II) complexes containing axial N-heterocyclic ligands is reported. The decomposition reaction is very exothermic, coinciding with the loss of the axial ligands. The average temperatures of decomposition correlate linearly with the basicity properties of the axial ligands.

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Zusammenfassung Es wird eine systematische TG- und DTA-Untersuchung der thermischen Zersetzung einer Reihe von Bis(dimethylglyoximat)-Komplexe von Eisen(II) mit axialem N-heterocyclischen Liganden beschrieben. Die Zersetzungsreaktion ist sehr exotherm, was mit dem Verlust der axialen Liganden zusammenfällt. Die durchschnittliche Zersetzungstemperatur ist den Basizitäts eigenschaften der axialen Liganden proportional.

     

Sequential titration of iron(II) and vanadium(IV) mixtures with cerium(IV) sulphate, with ferroins as indicators

The titration of vanadium(IV) with cerium(IV) sulphate, with nitroferroin as indicator, is proposed. Unlike ferroin, the indicator does not need a catalyst in this system. By suitable choice of experimental conditions iron(II) can be titrated first to a ferroin end-point and then vanadium(IV) to a nitroferroin end-point.     

The decomposition of iron(III) sulfate in air

The decomposition of initially hydrated powders of iron(III) sulfate was carried out in air over the temperature range 823–923 K. The decomposition process, which gave Fe₂O₃ as a solid product, was seen to have zero-order kinetics and an activation energy of 219 kJ·mol^–1. The nature of the product and the kinetics of decomposition were the same for samples decomposed in air and in argon. Sulfate samples with additives of FeS and Fe₂O₃ were also decomposed under similar conditions and the results confirmed the zero-order kinetics (for the case of the Fe₂O₃ additives) and the lack of effect of FeS on the decomposition of iron(III) sulfate.

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Zusammenfassung Anfänglich hydratiertes Eisen(III)-sulfatpulver wurde in Luft im Temperaturbereich 823–923 K zersetzt. Für die Reaktionsordnung des Zersetzungsprozesses, der als Endprodukt festes Fe₂O₃ lieferte, wurde Null und für die Aktivierungsenergie 219 kJ·mol^–1 ermittelt. Die Art des Produktes und der Kinetik der Zersetzung war in Luft und Argon gleich. Unter den gleichen Bedingungen wurden auch Sulfatproben mit Zusätzen von FeS und Fe₂O₃ zersetzt. Die Ergebnisse bekräftigen sowohl die nullte Reaktionsordnung (im Falle von Fe₂O₃ Zusätzen) als auch einen fehlenden Einfluß von FeS auf die Zersetzung von Eisen(III)-sulfat.

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823–923 . , , , 219 · ^–1. . FeS Fe₂O₃ . ( Fe₂O₃) - .

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This work was supported by a grant from the U.S. Department of Energy, Office of Basic Energy Sciences. The authors gratefully acknowledge this support.