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.     

Thermal decomposition kinetics of sodium metaperiodate

Aged and fresh samples of sodium metaperiodate are subjected to thermal decomposition studies in air by TG, DTG and DTA techniques. The kinetic parameters for their decomposition have been evaluated by weighted least squares method using equations of Coats-Redfern, Horowitz-Metzger and Freeman-Carroll. The results indicate that, within the limits of experimental error, ageing did not change the E^* values considerably.

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, . , -, - -. , , , E^*.

     

Thermal decomposition of sodium aluminium sulphate crystallohydrate

Dynamic TG investigations were carried out to elucidate the mechanism of thermal decomposition of aluminium sodium sulphate crystallohydrate. Shimadzu 31H and MOM Derivatograph X-ray diffraction and other techniques were used to determine data on the decomposition, activation energy, structure and phases in the solid products. Isothermal study in the temperature ranges 883–958 K and 983–1113 K in air or a reducing gas atmosphere revealed different reaction mechanisms. Depending on the experimental conditions, mainly Al₂O₃ can be obtained.     

Thermal decomposition of sodium nitrite and sodium nitrate pre-adsorbed on TiO2 surfaces

The thermal decomposition of sodium nitrite or nitrate pre-adsorbed upon TiO₂ surfaces has been investigated by employing several techniques as infrared spectroscopy (IR) and temperature programmed desorption in conjunction with mass spectrometry analysis (TPD-MS) to study the features observed during these thermal decompositions. Differential thermal analysis (DTA) in combination with X-ray diffraction analysis (XRD) were used to investigate the possibility of a solid state chemical reaction between the solid products originated from the thermal decomposition of the pre-adsorbed species and the TiO₂. On the basis of our results, various characteristic features of these thermal decomposition reactions will be discussed.This work was supported by JUNTA DE ANDALUCIA (financial support for research groups/1990).     

Thermal decomposition of jarosites of potassium,sodium and lead

Summary Jarosites are a group of minerals formed in evaporite deposits and form a component of efflorescence. As such the minerals can function as cation and heavy metal collectors. Thermogravimetry coupled to mass spectrometry has been used to study three Australian jarosites which are predominantly K, Na and Pb jarosites. Mass loss steps of K-jarosite occur over the 130 to 330 and 500 to 622°C temperature range and are attributed to dehydroxylation and desulphation. In contrast the behaviour of the thermal decomposition of Na-jarosite shows three mass loss steps at 215 to 230, 316 to 352 and 555 to 595°C. The first mass loss step for Na-jarosite is attributed to deprotonation. For Pb-jarosite two mass loss steps associated with dehydroxylation are observed at 390 and 418°C and a third mass loss step at 531°C is attributed to the loss of SO₃. Thermal analysis is an excellent technique for the study of jarosites. The analysis depends heavily on the actual composition of the jarosite.     

Thermal behaviour of diclofenac sodium: decomposition and melting characteristics

The thermal behaviour and melting characteristics of diclofenac sodium were investigated using various instrumental techniques--differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy and thin layer chromatography (TLC). DSC analysis of diclofenac sodium performed under dynamic flow of either synthetic air or helium or nitrogen did not produce any sharp endothermic peak characteristic of melting peak of a pure substance. Both the rate of scanning of the sample and the environmental atmospheric condition significantly affected the thermographic profile of diclofenac sodium. An exothermic peak prior to an endothermic peak corresponding to melting of the substance appeared when heated under dynamic flow of synthetic air suggesting oxidation (decomposition) of diclofenac sodium before reaching its melting point. In fact, at a scanning rate of 1 degree C/min only the exothermic peak appeared in the thermogram, suggesting complete decomposition prior to melting under the dynamic flow of synthetic air. DSC, FT-IR and TLC data obtained from samples heated under the dynamic flow of either helium or nitrogen revealed formation of a related compound, 1-(2,6-dichlorophenyl)-indolin-2-one, an indol-cyclic amide, as a result of an intramolecular cyclization reaction during the heating process. TGA data demonstrated a loss of 11.4-20.2% of the mass of diclofenac sodium when heated under various environmental conditions, and also supported the oxidative nature of degraded product(s) when the thermal process occurred slowly under a dynamic flow of synthetic air.     

Thermal decomposition of sodium chlorate and chromium(III) oxide mixtures

A study of the thermal decomposition of intimate mixtures of sodium chlorate and chromium(III) oxide in different molar ratios was made employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. Sodium chlorate in the presence of chromium(III) oxide starts to decompose around 180°, which is much below the decomposition temperature of pure NaClO₃. Each mole of Cr₂O₃ consumes 8/3 moles of NaClO₃, undergoing oxidation to sodium dichromate.     

Thermal decomposition ofC-iodotetrazoles

Thermal decomposition of 1-substitutedC-iodotetrazoles in melt and solutions has been investigated. Thermal stabilities, kinetic and activation parameters, and compositions of products of thermolysis ofC-iodotetrazolcs depend on the substituent nature. The scheme of thermolysis ofC-iodotetrazoles has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 68–71, January, 1996.     

Thermal decomposition of dicitratoborates

The thermal decompositions of dicitratoborates M¹[B(C₆H₆O₇)₂]·nH₂O (n=0–2, M¹=Rb, K, Li, NH₄) and M¹¹[B(C₆H₆O₇)₂]₂·8H₂O (M¹¹=Co, Ni, Mn, Cu, Zn, Cd) were investigated by means of TG, DTA and DTG methods. It was found that these thermal decompositions involve three successive stages: dehydration, the endothermal decomposition of the ligand, and oxidation of the residual organic component. The volatile products of decomposition in each stage were detected by means of gas chromatography. The method of TG-curve transformation into the curvedm/d T vs.m, wherem is the loss of weight at each moment of time, was used for a more detailed study of dehydration. The optimal conditions for TG-curve modification were found.

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Zusammenfassung Die thermische Zersetzung von Dicitratboraten der allgemeinen Formeln M¹[B(C₆H₆O₇)₂]·nH₂O (n=0–2;M ¹=Rb, K, Li, NH₄) und M¹¹[B(C₆H₆O₇)₂]₂·8H₂O (M ¹¹=Co, Ni, Mn, Cu, Zn, Cd) wurden mittels TG, DTA und DTG untersucht. Es wurde gefunden, daß die thermische Zersetzung dieser Verbindungen in drei Schritten verläuft: Dehydratisierung, endotherme Zersetzung des Liganden und Oxydation des organischen Rückstandes. Die flüchtigen Zersetzungsprodukte eines jeden Stadiums wurden gaschromatographisch detektiert. Zur detailierten Untersuchung der Dehydratisierung wurden die TG-Kurven zu Kurven transformiert, in denendm/dT gegenm dargestellt ist, wobeim der Gewichtsverlust zu einer gegebenen Zeit ist. Die optimalen Bedingungen für die TG-Kurvenmodifikation wurden festgestellt.

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, , ¹[(₆₆₇)₂]-n₂, =0–2, ^II[(₆₆₇)₂]₂ 8₂, Me^I=Rb, , Li, NH₄, Me^II=Co, Ni, Zn, Cd, Mn, . : , . . dm/dT- (). .

     

Thermal decomposition of gem-dinitroethylnitramines

Thermal decomposition of C,N-disubstituted gem-dinitroethylnitramines in dilute solutions in inert solvents is a first-order reaction and it is unaffected by the polarity of the solvent. The rate constant is largely controlled by the steric effect of the substituent at the carbon atom bearing gem-nitro groups. A correlation is found between the rate constant and the steric constant E _s of the substituent. This correlation permits prediction not only of thermal stability of yet unexplored compounds, but also of change of the decomposition mechanism.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1669–1673.Original Russian Text Copyright © 2004 by Stepanov, Kruglyakova, Astakhov.This revised version was published online in April 2005 with a corrected cover date.     

Thermal decomposition of mononitroalkanes

Conclusions The contribution of the heterogeneous reaction to the rate of the gas phase decomposition of nitroethane, 1-nitropropane, and 2-nitropropane was determined by varying the ratio of the surface to the volume of the reaction vessel (S/V).The activation energies of the homogeneous decomposition of the enumerated compounds differ from the literature data.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1412–1416, July, 1971.     

Thermal decomposition of azoethane

The thermal decomposition of azoethane (AE) was studied by detailed product analysis in the temperature and pressure intervals 508–598 K and 2.7–13.3 kPa. Besides the hydrocarbon products, three characteristic and quantitatively important nitrogen-containing compounds were also determined: ethyl-2-butyldiimide, ethanal-diethylhydrazone, and tetraethyl-hydrazine. Apart from the predominant termination reactions of the ethyl radical with itself and with the μ₂ radical, the decomposition is characterized by a very short chain reaction. The measurements led to determination of the following rate constants and rate constant ratios: for the following reactions:      

Thermal decomposition of cellulose

Journal of Thermal Analysis and Calorimetry - Cellulose has been pyrolysed in nitrogen at two heating rates, and the rates of formation of total gases, and the oxides of carbon, have been measured....     

Thermal decomposition of deuterofullerite

The volative products of thermal decomposition of deuterofullerite C₆₀D₁₉ were studied by mass spectrometry. It was found that D₂, CD₄, and C₆D₆ molecules are present in the gas phase above deuterofullerite heated to 773 K. Deuterocarbons appear in the gas phase already at 673 K.