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Abstract  

A method of gelation enthalpy determination of nitrocellulose (NC)+s-diethyldiphenylurea (Centralite 1, C1) binary system was elaborated using the change of Centralite 1 melting enthalpy in the mixture. The heats of C1 melting together with gelation and dissolution of NC fibres were determined by DSC calorimetric methods. A sharp maximum of the gelation enthalpy for C1 mole fraction x C1 max =0.555 suggests that the complex is very stable and one partly nitrated anhydroglucose ring is interacting with about 1.25 C1 molecules. The gelatinization enthalpy maximum equals
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\bar H_{max}^M$$ \end{document}
=−4.59 kJ mol−1.
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The thermal decomposition in air of several complexes of chromium(III) with imidazole,N-methylimidazole and 2-methylimidazole has been studied with the aid of differential thermal analysis (DTA), thermogravimetry (TG) and derivative thermogravimetry (DTG) in the temperature range 25–600°C. Although the final process of the decomposition gives Cr2O3, there are interesting differences in the complete process of decomposition. The reasons for these differences appear to be related to the trans-effect and to the presence in the imidazole complexes of hydrogen bonds. Enthalpies of the several decomposition reactions have been determined by differential thermal analysis.

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Some azo dyes have been assayed using D. I. E. The analysis is completed in less than 1 minute with an average error of 1.05% at the 1 mMole level.The reagent used is titanium(III)chloride. Degassing of the solutions is not necessary.

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Abstract  

Melting enthalpy and mixing enthalpy of binary system 2,4-dinitrotoluene and nitrocellulose were determined by DSC method. The maximum value of mixing enthalpy was H max M=1.38 kJ mol−1 for molar fraction x w24DNT = 0.501. The Flory-Huggins parameter (c) was estimated. The solubility curves and glass transition temperatures were predicted and compared with the experimental results. The measurements were performed for the samples with different times of storage at room temperature. The analysis of melting peaks for the mixture leads to the conclusion that for the long periods of storage the melting of 2,4-dinitrotoluene takes place in the confined spaces (pores) and unconfined space (bulk). The crystallization and melting is observed during the short time of storage in mixtures with low nitrocellulose content and in the case of mixtures with a large amount of NC the glass transition is additionally observed.

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Journal of Thermal Analysis and Calorimetry
Authors: Natalia Avramenko, M. Korobov, Aksana Parfenova, P. Dorozhko, Natalia Kiseleva, and P. Dolgov

Abstract  

In an effort to improve understanding of dissolution behaviour of fullerenes and their simple chemical derivatives the binary systems of C60, C70 and the piperazine monoadduct of [60] fullerene C60 N2C4H8 with a series of aromatic solvents have been studied by means of DSC. In certain systems solid solvates have been found to be the thermodynamically stable phases relative to saturated solution at room temperature. Identified solid solvates were characterized by their compositions, temperatures and enthalpies of incongruent melting transitions. The regularities in thermodynamic stability of the solvated crystals have been discussed along with dissolution properties of fullerenes and the derivative. Certain correlations have been observed.

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Journal of Thermal Analysis and Calorimetry
Authors: J. C. J. Bart, A. Bossi, P. Perissinoto, A. Castellan, and N. Giordano

The thermal degradation of H6TeO6 in air has been evaluated critically. Evidence is presented for a decomposition mechanism involving step-wise dehydration of H6TeO6 via non-stoichiometric amorphous solids to polymetatelluric acid and up to a composition corresponding to pyrotelluric acid. No morphological changes were observed during these structural variations and no evidence was found for the formation of allotelluric acid. Further dehydration is accompanied by reduction, which, depending upon the experimental conditions accounts for the considerable variety of results reported previously. Crystalline Te(VI)-Te(IV) oxides are obtained at about 550‡ from which TeO2 is formed by additional calcination at about 620‡.

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Abstract  

Solid complexes of M(His)2Cl2 nH2O (M=Mn, Co, Ni, Cu) of MnCl26H2O, CoCl26H2O, NiCl26H2O, CuCl22H2O and L-α-histidine (His) have been prepared in 95% ethanol solution and characterized by elemental analyses, chemical analyses, IR and TG-DTG. The constant-volume combustion energies of the complexes have been determined by a rotating-bomb calorimeter. And the standard enthalpies of formation of the complexes have been calculated as well.

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Abstract  

Differential scanning calorimetry (DSC) was used to determine the molar enthalpies of dehydration and decomposition of CoC2O42H2O, Co(HCOO)22H2O and [Co(NH3)6]2(C2O4)34H2O. The first stage of dissociation of each compound is a single-step dehydration both in air and argon atmospheres. The next stages are decomposition processes influenced by experimental parameters. The enthalpies of dehydration and decomposition vary from compound to compound in each atmosphere. The obtained data have been related to the macromechanisms proposed for the thermal decomposition and the parallel-consecutive decomposition-oxidation processes.

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Thermal features and thermochemistry of hexachlorohafnates of nitrogen aromatic bases

Theoretical studies on the geometry and thermochemistry of HfCl 6 2−

Journal of Thermal Analysis and Calorimetry
Authors: T. Janiak, J. Rak, and J. Btażejowski

Abstract  

Hexachlorohafnates of pyridine and its three methyl-substituted derivatives were synthesized and examined by the thermoanalytical methods. The van't Hoff equation employed for the thermogravimetric αvs. T dependencies enabled evaluation of the heats of the thermal dissociation and subsequently enthalpies of formation and crystal lattice energies of the salts. Geometry and energy of formation of HfCl 6 2− was determined at the ab initio Hartree-Fock SCF level, using all electron MINI basis set augmented with standard polarization functions (MINI*). Electron correlation was considered at the MP2 level. Thermodynamic characteristics for the latter species were also obtained combining ab initio results with those of statistical thermodynamics. The usefulness of theoretical methods in examination of solid state energetics is briefly discussed.

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