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 xC1max
=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
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.
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.
Authors:T. Wolszakiewicz, A. Książczak, and T. Książczak
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 HmaxM=1.38 kJ mol−1 for molar fraction xw24DNT = 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.
Authors:Natalia Avramenko, M. Korobov, Aksana Parfenova, P. Dorozhko, Natalia Kiseleva, and P. Dolgov
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  fullerene C60
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.
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‡.
Authors:S. Chen, Sh Gao, X. Yang, R. Hu, and Q. Shi
Solid complexes of M(His)2Cl2nH2O (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.
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.
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
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.