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The influence of the fuel to oxidant ratio on the ageing behaviour of the magnesium–strontium nitrate pyrotechnic system in the presence of water vapour has been investigated by isothermal microcalorimetry in conjunction with chemical and thermal analysis measurements. The major products of ageing were identified as magnesium hydroxide and strontium nitrite. Measurement of the ratio of the amount of magnesium hydroxide formed to that of strontium nitrate reacted has shown that for compositions containing from 10 to 60% magnesium, a major component of the ageing process could be represented by the equation 3Mg + Sr(NO3)2 + 4H2O → 3Mg(OH)2 + Sr(NO2)2 + H2. DSC studies have confirmed that the formation of strontium nitrite during ageing has a significant influence on the high temperature pyrotechnic reaction between magnesium and strontium nitrate.

The ageing behaviour of a pyrotechnic composition containing equal parts by mass of magnesium and strontium nitrate has been followed by isothermal microcalorimetry. The measurements were carried out on the samples at 50 °C and 65% relative humidity in air using closed ampoules. The results have been compared to those obtained for magnesium powder under the same conditions. Following an initial induction period, the pyrotechnic compositions reacted at a much faster rate than magnesium powder alone. The main reaction products were found to be magnesium hydroxide and strontium nitrite; the amounts formed have been correlated with the cumulative heats of ageing. In addition, the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry (DSC) and by modulated temperature DSC.

The aim of this study is to demonstrate the potential of coals as a low-cost reactive barrier material for environmental protection applications, with the ability to prevent leaching of toxic Cr(VI) and other transition metals. Depending upon the type of ion and the surface functionalities, the uptake can involve ion sorption, ion exchange, chelation and redox mechanisms with the surface functionalities being considered as partners in electron transfer processes. The capacity for Cr(VI) uptake of low rank coals and oxidized bituminous coals has been found to lie within the range 0.2–0.6 mM g −1 . Air oxidation of bituminous coals can increase their Cr(VI) removal capacities. The effect of air oxidation of coals on uptake capacity was more pronounced for Cr(VI) than Cr(III), but less than for Hg(II) and the other ions (Ca 2+ , Ba 2+ , Zn 2+ , Cd 2 ) investigated. As previously found for Hg(II), redox mechanisms play an important role in Cr(VI) uptake, with sorption of the resultant Cr(III) being aided by the functionalities arising from oxidation of the coal surface. In acidic media, much of the resultant Cr(III) is exchanged back into solution by hydrogen ions, but some of the sorbed chromium is irreversibly bound to the coal. The reduction of Cr(VI) alone is often considered a satisfactory solution in view of Cr(III) being essentially non-toxic.

For the well-swept fixed-bed reactors used in temperature-programmed reduction (TPR) to specify the organic sulfur forms present in coals and kerogens, calibrants must neither melt nor evaporate before the onset of thermal decomposition. In this respect, nonmelting silica-immobilized substrates are suitable with the Si-O-C linkage being stable up to ca. 500 °C. Silica-immobilized samples of dibenzothiophene, diphenyl sulfide, phenyl benzyl sulfide, and thioanisole have been synthesized and noncatalytic tests have been conducted in atmospheric and high-pressure TPR reactors. The characteristic reduction temperatures of the non-thiophenic compounds investigated are well resolved from that of dibenzothiophene for both techniques and the results have validated previous findings by TPR on coals. The use of high hydrogen pressure (150 bar) lowered the reduction temperatures substantially. The H 2 S recoveries from the atmospheric experiments are low suggesting that, for the non-thiophenic compounds, secondary reactions occur yielding refractory thiophenes which are not detected. Although sulfur recoveries are greatly improved, such reactions are still evident with 150 bar hydrogen pressure especially in the case of the phenyl benzyl sulfide, possibly as a consequence of the high surface coverages used. Insights into the retrogressive chemistry occurring for the immobilized phenyl benzyl sulfide have been provided from GC-MS analysis of hydrolyzed TPR residues obtained at different temperatures, and from vacuum pyrolysis experiments conducted as a function of surface coverage.

In this communication, the temperature-programmed reduction with on-line mass spectrometry has been conducted on the series of four fenolic resites (cured resoles) containing different sulfur functionalities in a TGA apparatus to ascertain whether the release of SO 2 is dependent primarily on sulfur functionality or whether other factors, particularly the concentration of volatile matter and chemistry involving the interconversion of sulfur forms, are also important for macromolecular systems

Reactions of chromium pentafluoride, CrF5, with some Lewis acids and bases have been studied and the reaction products have been characterized by infrared and Raman spectroscopy. CrF5reacts with the bases CsF and NO2F to give CsCrF6 and NO2CrF6, respectively. The Lewis acid, SbF5, reacts with CrF5 to give the adduct CrF5·2SbF5, which should be formulated as CrF4Sb2F11 on the basis of spectroscopic evidence. This compound is a strong oxidizing agent, reacting with O2, Xe and C6F6 to form, respectively, O2(CrF4Sb2F11), Xe(CrF4Sb2F11)2 and C6F6(CrF4Sb2F11). It was observed that O2(CrF4Sb2F11) reacts with C6F6 and IF5 to form C6F6(CrF4Sb2F11) and IF4(CrF4Sb2F11), respectively.