Thermal decomposition of silver carbonate

Conflicting results have been reported by different workers on the thermal decomposition of silver carbonate, Ag₂CO₃. In the present study, the decomposition mechanism was elucidated by various analytical methods; gas analysis (differential thermal gas analyses) in helium, carbon dioxide and oxygen flows with and without a P₂O₅ trap or a KOH trap, DTA-TG in a carbon dioxide flow and high-temperature X-ray diffraction analysis in a carbon dioxide flow. The gas evolution at ca. 200?C consisted of carbon dioxide. A simultaneous evolution of carbon dioxide and oxygen occurred at ca. 400?C. Two endothermic peaks (ca. 189 and 197?C) without weight change during the heating in a carbon dioxide atmosphere were due to the phase transition of silver carbonate from the normal viaΒ toα phase. The reverse transition occurred during the cooling.     

On the pyrolytic decomposition of cadmium carbonate

The pyrolytic decomposition of cadmium carbonate was studied by thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermoanalysis (DTA) and exoemission of electrons (EEE).     

The thermal decomposition of the carbonate reaction products

The complex thermal analysis was used in the investigations of the carbonate reaction products in the residue after Al leaching from calcium aluminate-12CaO·7Al₂O₃ and Selfdisintegrated Powder. The conversion of Al was calculated basing on a content of Al in the pregnant solution as well as in a residue obtained from the kinetic investigations. The third method of measurements of a conversion of Al was presented and discussed. Results show, that the proposed method can be used for conversion estimations with 95% of confidence level as well as for the detection of carbonate products and is useful for an interpretation of the new approach for kinetic mechanism of Al leaching.     

Cathodic decomposition reactions of propylene carbonate

The cathodic decomposition of propylene carbonate was investigated. Whereas at graphite the reaction occurs with reasonable high current densities predominantly via the formation of alkali metal intercalation compounds (EC mechanism) at active electrode surfaces such as e.g. sintered nickel, copper- or steel-felt, the reaction occurs at rather small current densities by direct electrochemical reduction. In both cases the reaction products are propene and carbonate. An interpretation of the observed effects due to reactions of impurities such as water can be excluded. Solvent decomposition reactions have to be taken into account for the use of solvents as e.g. PC in lithium batteries.     

Thermal decomposition of basic lead carbonate

TG and DTA curves of the thermal decomposition of basic lead carbonate, 2PbCO₃ Pb(OH)₂, are presented and compared with the thermogram of normal lead carbonate PbCO₃. The appearance of different intermediate compounds at identical experimental conditions is ascribed to the degree of perfection of the carbonate crystals. Poorly developed basic lead carbonate crystals, formed in the presence of polyglutamic acid, give no recognizable intermediate compounds.     

Thermal decomposition of zinc carbonate hydroxide

This study is devoted to the thermal decomposition of two zinc carbonate hydroxide samples up to 400 °C. Thermogravimetric analysis (TGA), boat experiments and differential scanning calorimetry (DSC) measurements were used to follow the decomposition reactions. The initial samples and the solid decomposition products were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and laser particle size analyzer. Results showed that zinc carbonate hydroxide decomposition started at about 150 °C and the rate of decomposition became significant at temperatures higher than 200 °C. The apparent activation energies (E_a) in the temperature range 150–240 °C for these two samples were 132 and 153 kJ/mol. The XRD analyses of the intermediately decomposed samples and the DSC results up to 400 °C suggested a single-step decomposition of zinc carbonate hydroxide to zinc oxide with not much change in their overall morphologies.     

Thermal decomposition of ammonium cerous carbonate

The thermal decomposition of ammonium ceryl(III) carbonate (ACeC) [NH₄CeO(CO₃)] was investigated by thermogravimetry, differential thermal analysis and X-ray diffraction. The results showed three endothermic stages of decomposition, each involving a loss in weight. The first stage, at 65.5 °C, is characteristic of the removal of adsorbed water, the second stage, at 214.8 °C, is associated with ammonia release, and the third stage, at 263.6 °C, relates to the removal of carbon dioxide.     

The kinetic compensation effect in the decomposition of calcium carbonate

Some specific factors which may cause the kinetic compensation effect (k.c.e.) during the decomposition of CaCO₃ are identified. The role of the CO₂ equilibrium pressure is examined in relation to the k.c.e. The article also shows why non-isothermal experiments must sometimes necessarily yield a value of activation energy different from the value obtained from isothermal experiments.

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Zusammenfassung Einige spezifische Faktoren, welche den sogenannten kinetischen Kompensationseffekt (k. c. e.) während der Zersetzung von CaCO₃ herbeiführen können, werden identifiziert. Die Rolle des Gleichgewichtsdruckes des CO₂ wird im Zusammenhang mit dem k. c. e. geprüft. Der Beitrag zeigt, warum die nicht-isothermen Versuche manchmal zwangläufig zu einem von den isothermen Versuchen abweichenden Wert der Aktivierungsenergie führen.

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甘氨酸钠碳酸盐的合成及表征

在泡腾饮料、面食品和膨化食品中,过去一直用ＮａＨＣＯ3作ＣＯ2源[1],但它溶解度低、易残留、稳定性不高,加热至一百多度粉末会放出气体,水溶液中则会分解。甘氨酸钠碳酸盐溶解度大、不存在残留问题;且稳定性高,粉状品加热至385℃以上才会放出气体,加热至100℃水溶液中不分解;发生中和反应时不产生水,具有抗菌性防腐作用[3]和缓冲性故较宜用于复配发泡制品[2]。本文用超声合成法制备了甘氨酸钠碳酸盐,对其进行了ＩＲ及ＸＲＤ表征。1　实验部分1 1　合成超声合成法:取甘氨酸(ＡＲ)7 5ｇ(0 1ｍｏｌ)和碳酸钠(ＡＲ)5 3ｇ(0 05ｍｏｌ),加入…     

One-pot carbonyl reduction and carbonate formation using sodium borohydride in dialkyl carbonate solvents

Preparation of mixed carbonates proceeded in one step from ketones and aldehydes via treatment with NaBH₄ in dimethyl or diethyl carbonate solvent at elevated temperatures. This is an efficient and convenient alternative to the traditional two-step sequence of carbonyl reduction to alcohol and subsequent carbonate formation by treatment with an alkyl chloroformate. 25 examples are presented from 49 to 92% yield, highlighting the versatility of this reaction.     

The thermal decomposition of Mg-containing carbonate apatites

Carbonate apatites precipitated from an aqueous solution and containing Mg²⁺ and Sr²⁺ ion were studied by thermogravimetric, infrared absorption, and X-ray diffraction methods. In the temperature range of 25–350°C water evolves and at 350–905°C carbonate decomposes. Two effects characterize the Mg-containing system: Weight loss during decomposition is related to carbonate in the apatite and to an additional ion; increased formation of whitlockite. The interrelation between these two phenomena and the presence of carbonate and Mg is discussed.     

Thermogravimetric studies of quaternary systems involving salicylic acid,sodium salicylate,sodium carbonate and sodium hydrogen carbonate,part III

The thermal decompositions of quaternary systems comprising salicylic acid, sodium salicylate, disodium salicylate sesquihydrate, sodium carbonate and sodium hydrogen carbonate were investigated using thermogravimetry and differential thermal analysis. A possibility was shown of analyzing quaternary systems comprising three or four interacting components. Use can be made of the results of these investigations in the control of the course and degree of conversion of reagents in commercial-scale production of sodium salicylate as well as in checking the declared compositions, hydration degrees and contamination with starting reagents of multicomponent salicylate mixtures.

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Zusammenfassung Die thermische Zersetzung Salicylsäure, Natriumsalicylat, Dinatriumsalicylat Sesquihydrat, Natriumkarbonat und Natriumbikarbonat enthaltender quaternärer Systeme wurde mittels Thermogravimetrie und Differentialthermoanalyse untersucht. Die Möglichkeit der Analyse quaternärer Systeme mit drei oder vier aufeinander einwirkenden Komponenten wurde gezeigt. Die Ergebnisse dieser Untersuchungen können bei der Kontrolle des Verlaufs und des Konversionsgrades der Reagentien, bei der Herstellung von Natriumsalicylat im Handelsmaßstab sowie bei der Prüfung der deklarierten Zusammensetzung des Hydratierungsgrades und der Verunreinigung mit Ausgangsreagentien von Salicylatgemischen mit einer Vielzahl von Komponenten eingesetzt werden.

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Résumé Etude de la décomposition de systèmes quaternaires contenant de l'acide salicylique, du salicylate de sodium, du salicylate disodique sesquihydraté, du carbonate de sodium et de l'hydrogénocarbonate de sodium, par thermogravimétrie et par analyse thermique différentielle. On montre qu'il est possible d'analyser des systèmes quaternaires dans lesquels trois ou quatre composants réagissent entre eux. Les résultats de la présente étude peuvent servir pour contrÔler l'avancement de la réaction dans la production à l'échelle commerciale du salicylate de sodium et pour vérifier la composition déclarée, le degré d'hydratation et la contamination éventuelle par les réactifs initiaux dans les mélanges de salicylate à composants multiples.

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Part II: J. Thermal Anal., 10 (1976) 233.     

Kinetics and mechanism of thermal decomposition of lead carbonate

Results are given on the kinetics and mechanism of the processes in the thermal decomposition of lead carbonate with the application of TG and DTA experimental investigation methods.The following mechanism was established: 3 PbCO₃=2 PbO.PbCO₃+2 CO₂ (1) 2 PbO.PbCO₃=3 PbO+CO₂ (2) PbO — melting (3)The following activation energy values were determined with TG methods for processes (1) and (2): 118.2 and 235.2 kJ/mole, respectively; and with DTA methods for processes (1), (2) and (3): 113.9, 246.6 and 294.9 kJ/mole, respectively.

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Zusammenfassung Die an Hand der TG- und DTA-Untersuchungen erhaltenen Ergebnisse über Kinetik und Mechanismus der bei der thermischen Zersetzung von Bleicarbonat auftretenden VorgÄnge werden beschrieben.Die folgenden Mechanismen des Vorganges wurden festgestellt: 3 PbCO₃=2 PbO.PbCO₃ + 2 CO₂ (1) 2 PbO.PbCO₃=3 PbO + CO₂ (2) PbO — Schmelzen (3)Die folgenden Werte der Aktivierungsenergie wurden durch TG-Versuche für die VorgÄnge (1) und (2) bestimmt: 118.2, bzw. 235.2 kJ/Mol, und durch DTA-Messungen für die VorgÄnge (1), (2) und (3): 113.9, 246.6, bzw. 294.9 kJ/Mol.

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Résumé La cinétique et le mécanisme des réactions qui se déroulent lors de la décomposition thermique du carbonate de plomb ont été étudiés par TG et ATD. Les mécanismes suivants ont été établis: 3 PbCO₃=2 PbO.PbCO₃+2 CO₂ (1) 2 PbO.PbCO₃=3 PbO + CO₂ (2) PbO — fusion (3)Pour les réactions (1) et (2), les valeurs de 118.2 et 235.2 kJ · mol^–1 ont été trouvées à partir des résultats TG et pour les réactions (1), (2) et (3) l'ATD a fourni respectivement 113.9, 246.6 et 294.9 kJ · mol^–1.

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, . : 3 ₃=2 PbO.PbCO₃+2 ₂ (1) 2 PbO.PbCO₃=3 +O₂ (2) — (3) (1) (2), 118.2 235.2 /. (1), (2) (3) : 113.9; 246.6 294.9 /.

     

Solubilities and vapour pressures of saturated aqueous solutions of sodium tetraborate,sodium carbonate,and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions

Solubilities and vapour pressures of water over saturated solutions of sodium tetraborate, sodium carbonate, and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions were determined and compared with the literature data. These results permitted the evaluation of osmotic and activity coefficients and molar enthalpies of vaporization.     

Thermal decomposition of basic zinc carbonate in nitrogen atmosphere

Dynamic kinetic analyses were performed on basic zinc carbonate using TG and DTA measurements in N₂. The thermal behavior and the kinetics of decomposition were studied. The effect of procedural variables on the kinetics was investigated. In this work, the procedural variables included heating rate and sample size. To estimate the activation energy of decomposition, the Friedman isoconversional method was applied. The activation energy (E_a) was calculated as a function of conversion (a).     

Thermogravimetric studies of binary and ternary systems containing salicylic acid,sodium salicylate,sodium carbonate and sodium hydrogen carbonate. Part II

The mechanism of thermal decomposition of binary and ternary systems containing salicylic acid, sodium salicylate and disodium salicylate sesquihydrate, sodium carbonate and sodium hydrogen carbonate were studied by means of thermogravimetric and differential thermal analysis. The possibility was demonstrated of analyzing ternary systems containing three unreactive or three reactive components. The results can be useful for monitoring the course of the commercial-scale manufacture of sodium salicylate and for checking declared compositions of salicylate mixtures.

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Zusammenfassung Ein Mechanismus der thermischen Zersetzung SalicylsÄure, Natriumsalicylat und Dinatriumsalicylat Sesquihydrat, Natriumcarbonat und Natriumhydrocarbonat enthaltender binÄrer und ternÄrer Systeme wurde mittels Thermogravimetrie und Differentialthermoanalyse untersucht. Die Möglichkeit, drei unreaktive oder drei reaktive Komponenten enthaltende ternÄre Systeme zu untersuchen, wurde gezeigt. Die Ergebnisse können dazu eingesetzt werden den Verlauf der Natriumsalicylatfabrikation im Handelsma\stab zu verfolgen und deklarierte Zusammensetzungen von Salicylatmischungen zu überprüfen.

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Résumé On a étudié par thermogravimétrie et par analyse thermique différentielle le mécanisme de la décomposition thermique de systèmes binaires et ternaires contenant de l'acide salicylique, du salicylate monosodique et du salicylate disodique sesquihydraté, du carbonate de sodium et de l'hydrogénocarbonate de sodium. On montre la possibilité d'analyser des systèmes ternaires comprenant trois composants réactifs ou non. Les résultats peuvent Être utilisés pour commander le déroulement de la fabrication du salicylate de sodium à l'échelle commerciale et pour contrÔler les compositions déclarées des mélanges de salicylates.

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Thermal decomposition of sodium azide

The thermal decomposition of sodium azide has been investigated in the temperature range 240–365°C. Three values for the activation energy, 37.0, 59.0 and 14 kcal mol^?1 have been obtained depending on the temperature range of study. The mechanism of decomposition seems to involve excited azide ions (through internal conversion) and excitations. The activation energy of 14 kcal mol^?1 appears to be associated with the promotion of electron in the presence of sodium metal.