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Abstract  

The research in thermal analysis and calorimetry, conducted by the author over the period 1964 to 1993, is summarised and concisely reviewed. The major investigations have focussed on thermal analysis studies of coordination compounds, particularly the metal dithiocarbamate complexes. A significant solution calorimetric study of some metal dithiocarbamate complexes has also been undertaken. DSC has been applied to determine the sublimation enthalpies of many metal dithiocarbamate and metal pentane-2,4-dionate complexes and solution calorimetry has been applied to study the thermochemistry of the latter group of complexes. Thermal analysis investigations of several inorganic molten salt systems have been initiated. Thermometric titrimetry has been applied to study metal-macrocyclic ligand systems in aqueous media and particularly those systems of environmental significance. Temperature calibration standards for TMA have been proposed and TMA has been applied to study the mechanical properties of several common inorganic compounds. DTA has been applied to study a wide variety of phenols and has subsequently been applied as an analytical technique to determine the components of solid state phenol mixtures. Thermometric titrimetry has been applied to determine the phenolic content of wines. A comprehensive thermal analysis study of Australian brown coal has been undertaken, involving the DSC determination of coal specific energy, a TG/DTA study of the coal pyrolysis and combustion processes and a TG/DTA and EGA study of the cation catalytic effect on the coal pyrolysis process. Thermal analysis and calorimetric techniques have been extensively publicised and promoted by the publication of specialist reviews, the presentation of symposia review papers and the oral presentation of short courses, particularly in the SE Asian region. This review essentially reveals the diversity of possible application of thermal analysis and calorimetric techniques and the primary significance of thermodynamic data in the fundamental rationalisation of chemical phenomena.

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Abstract  

A short review of the thermal analysis data available for dithiocarbamate complexes of tin(II) and tin(IV) is presented. Since the relevant thermal decomposition mechanisms are complicated, even for decompositions in inert atmospheres, mechanisms postulated on the basis of thermal analysis data alone are suspect. Realistic thermal decomposition mechanisms for these complexes can only be formulated when the relevant decomposition products are unambiguously identified. In this short review, an attempt is made to identify trends in these thermal analysis data, with particular reference to structural features of the corresponding complexes.

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The pyrolysis of a suite of brown coal samples and bituminous coal maceral concentrates is investigated by non-isothermal thermogravimetry. The TG data for these coals reveal a two-stage pyrolysis process. The activation energy for the primary pyrolysis stage is considerably higher than that for the secondary pyrolysis stage. It is evident that a particular coal may be characterised by the weighted mean apparent pyrolysis activation energy which correlates with the corresponding specific energy of the coal.

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A DTA study of phenols

II. Methyl-, methoxy- and methyl, halo-phenols

Journal of Thermal Analysis and Calorimetry
Authors: N. Buckman, J. Hill, and R. Magee
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A DTA Study of phenols

III. Polyhydroxy-phenols and naphthols

Journal of Thermal Analysis and Calorimetry
Authors: N. Buckman, J. Hill, and R. Magee
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A DTA study of phenols

IV. Nitro- and amino-phenols

Journal of Thermal Analysis and Calorimetry
Authors: N. Buckman, J. Hill, and R. Magee
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Thermal stability of the crystallisation nucleant

2,4,6 trinitrotoluene, TNT, and 2,2',4,4',6,6'hexanitrostilbene, HNS

Journal of Thermal Analysis and Calorimetry
Authors: A. Aziz, M. Cartwright, and C. J. Hill

The 2,2',4,4',6,6'hexanitrostilbene, HNS, nucleant, used in the crystallisation of 2,4,6,trinitrotoluene, TNT, was precipitated from molten TNT and examined by differential scanning calorimetry, DSC, at several stages during purification by vacuum sublimation. During purification a broad endotherm, associated with nucleant decomposition, which could be resolved into two endotherms, depending on the sublimation temperature, was observed. Pure nucleant prepared at 70‡C showed a similar behaviour during thermal annealing for extended periods of time at >85‡C. Thus TNT, retained in the recrystallised HNS nucleant, may be migrating during the purification process or may occupy a range of lattice sites, which exhibit different activation energies for migration to the surface of the solid during thermal decomposition of the nucleant. Loss of TNT from the nucleant, during purification, could produce some free HNS. The activation energy for nucleant decomposition, which may be a two-stage processes with the initial mobility of the TNT being the limiting reaction, was estimated to be ∼210 kJ mol. The lattice sites available for the TNT in the host HNS nucleant require elucidation and are the subject of further studies to be published at a later date.

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Abstract  

A DSC compositional analysis of 3 model binary systems of pharmaceutical significance has been conducted. Mixtures of known selected composition for each of the systems 3,5-dinitrobenzoic acid/benzoic acid, paracetamol/4-aminobenzoic acid and acetylsalicylic/salicylic acid were prepared and analyzed by DSC. The respective compositions derived from applications of the van't Hoff equation were correlated with the corresponding theoretical values and with the corresponding fusion temperatures and fusion enthalpies, obtained from the relevant DSC profiles. Linear correlations were found to exist between the theoretical compositions, fusion temperatures and fusion enthalpies for each of these systems and it is apparent that with suitable calibration procedures, the DSC compositional analysis method can be applied to determine the purity at the 90–95 mole% level. This level is of considerable interest in drug stability studies and has real significance in purity assays of commercial pharmaceutical preparations.

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