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Abstract  

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.

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Abstract  

Mössbauer spectra of hexakis (trimethylacetato) ferrate(III) complexes with general formula M3[Fe{OCOC(CH3)3}6] (where M=H+, Li+, Na+, K+ and NH 4 + ) exhibit a quadrupole doublet with EQ=0.31–0.65 mms–1 and =0.60–0.74 mms–1 (with respect to S.N.P. as standard). Infrared studies suggest unidentate coordination of the carboxylate ligands. Anomalously high and EQ values for H3[Fe{OCOC(CH3)3}6] have been explained in terms of possible hydrogen bonding. Thermal decomposition studies show fast and single stage decomposition yielding a constant weight at 320°C. Mössbauer spectra of intermediates after heating complexes at different temperatures indicate increasing EQ values. At 350°C, all complexes exhibit six-line spectra, suggesting the formation of alkali metal ferrate (Na2O·NaFeO2) or Fe2O3.

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Abstract  

A series of carboxylatoferrate (III) complexes have been synthesized with monocarboxylic and dicarboxylic acids. Mössbauer spectra of all the complexes exhibit quadrupole doublets with EQ=0.36–0.88 mm s–1, suggesting a distorted octahedral geometry. The complexes start decomposing at 100°C and finally yield a constant weight at <500°C. Mössbauer spectral studies of the intermediates and final products after heating at different temperatures yield a complex pattern, suggesting the formation of one or two magnetic phases. Mössbauer spectra of the final products show two, six or eight lines with a central doublet, all indicating the formation of -Fe2O3 of different particle sizes. It is proposed that decarboxylation occurs first, followed by the loss of one or two ligands, depending on the nature of the carboxylate and the heating tempeature. The complex of pyridine-2,6-dicarboxylic acid shows an anomalous behavior.

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Abstract  

Tetracyanocomplex clathrates and their changes caused by heating were studied. The intermediates formed were characterized by IR and UV-VIS spectroscopy. Elemental analysis and XRD patterns were also used. For the visualisation of changes occurring on the surface and the distribution of metallic elements therein were studied by electron microscopy and EDX. The extent of the non-stoichiometric changes introduced by the topochemical course of the degradation reactions was correlated with the measured electrical values.

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Abstract  

Hydrated methanesulfonates Ln(CH3SO3)3 nH2O (Ln=La, Ce, Pr, Nd and Yb) and Zn(CH3SO3)2 nH2O were synthesized. The effect of atmosphere on thermal decomposition products of these methanesulfonates was investigated. Thermal decomposition products in air atmosphere of these compounds were characterized by infrared spectrometry, the content of metallic ion in thermal decomposition products were determined by complexometric titration. The results show that the thermal decomposition atmosphere has evident effect on decomposition products of hydrated La(III), Pr(III) and Nd(III) methanesulfonates, and no effect on that of hydrated Ce(III), Yb(III) and Zn(II) methanesulfonates.

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Abstract  

An autocatalytic model involving the limited solubility of volatile catalytic products was applied to the thermal decomposition of 2,4,6-trinitrotoluene. The critical supersaturation of the thermal decomposition products with the catalytic properties was higher at a low heating rate. Decrease of the sample mass led to an increased critical supersaturation of the decomposition products. This is probably a result of the greater contribution of products adsorption on the aluminium pan surface. It is presumed that the differences observed in the rate constant are connected with the uncontrolled critical supersaturation of the volatile thermal decomposition products.

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Abstract  

Thermal decomposition of natural pyrite (cubic, FeS2) has been investigated using X-ray diffraction and57Fe Mössbauer spectroscopy. X-ray diffraction analysis of pyrite ore from different sources showed the presence of associated minerals, such as quartz, szomolnokite, stilbite or stellerite, micas and hematite. Hematite, maghemite and pyrrhotite were detected as thermal decomposition products of natural pyrite. The phase composition of the thermal decomposition products depends on the temperature, time of heating and starting size of pyrite crystals. Hematite is the end product of the thermal decomposition of natural pyrite.

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Abstract  

Using Mössbauer spectroscopy, the thermal decomposition products of co-precipitated Fe/NH4/2/SO4/2.6H2O and Ni/NH4/2/SO4/2.6H2O for two hours at various temperatures in open air have been studied and identified. It has been found that NiFe2O4, formed at 900 °C and 1100 °C, has been the final product.

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Abstract  

A method is described for the determination of airborne compounds of203Hg. The method is based on the sorption of Hg on hopcalite (activated copper oxide/manganese oxide) with subsequent monitoring for the gamma-radiation of203Hg. Aerosol activity in the air is separated by sucking the air through a filter prior to the absorption tube. The sensitivity of the method permits the assessment of less than one tenth of the maximum permissible concentration in air. It is shown experimentally that the separation procedure used is suitable for the determination of airborne mercuric acetate and its thermal decomposition products.

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