Journal Articles (before-1995)

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    Explosive Oxidation of Hydrogen Sulphide: Self-heating, Chain-branching and Chain-thermal Contributions to Spontaneous Ignition
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Gray, Peter; Sherrington, Malcolm E.
    The spontaneously explosive oxidation of hydrogen sulphide in a 290 cm3 vessel has been investigated over a temperature range 280–360°C and between pressures of 10 and 120 mmHg. Conditions for ignition have been mapped on a p,T diagram. Very fine thermocouples (25 µm Pt–Pt/Rh) have been used to detect and measure self-heating, and special emphasis has been laid on the direct measurement of the size and form of the temperature against time histories for different initial conditions or locations on the ignition diagram. The effects of reactant proportions and of added diluents (with different thermal conductivities) on the second and third ignition limits have also been studied. Although the reaction exhibits many features traditionally associated with purely branched chain explosions, the direct temperature measurements have revealed extensive self-heating under very varied conditions of pressure and temperature. Boundaries may be drawn on the ignition diagram that separate the regions where a combined chain-thermal mechanism is responsible for explosions (I) from those which may be considered as purely thermal (II) or isothermal branched chain (III) in nature. The measured temperature against time histories provide novel experimental support for the unified theoretical treatment of chain and thermal explosions of Gray and Yang. Critical temperature rises are smaller than would be expected on a purely thermal basis, and induction times are longer. In the chain-thermal region, the rate of self-heating immediately prior to ignition is not always rapid; indeed, temperature excesses may be relatively steady or even decreasing when spontaneous explosion takes place. We should expect similar behaviour in the hydrogen-oxygen reaction.
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    Effect of Radical Scavengers and Electric Fields on the y-Radiolysis of Gaseous Hydrogen Sulphide
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (2), 1973) Huyton, D. W.; Woodward, T. W.
    In the γ-radiolysis of H2S with added buta-1,3-diene, H atoms appear to react before they become thermalised. With added benzene, propene, and but-1-ene insufficient scavenging occurs to say with certainty whether a similar situation applies, but indications are that it may be so for propene, and but-1-ene. Investigation of the effect of but-1-ene on the sulphur yield, indicates a dose rate effect which is explained by a competition between ion-recombination and diffusion to the wall enhanced by convenction currents. Yields of G(H2)=G(S)= 0.5 unscavengable by buta-1,3-diene are indicated, and evidence is given that excited sulphur atoms (S*) and S+ ions are probable precursors of these yields. Nitric oxide appears to react with SH radicals in a chain process producing H2O, N2O and S. Electric fields do not affect the radiation yields until electron acceleration just before saturation occurs, causes increased decomposition. The ratio of sulphur scavengable in the presence of a field is ∼4 : 1, which is much lower than in the absence of a field (13:1). This is evidence for production of excited S atoms by field accelerated electrons.
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    Electron Spin Resonance Study of the Reaction of Hydrogen Atoms with Hydrogen Sulphide
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (2), 1973) Bradley, John N.; Trueman, Susan P.; Whytock, David A.; Zaleski, Thomas A.
    The reaction between H atoms and hydrogen sulphide, with and without added nitric oxide, has been studied by following the H atom, S atom and SH radical concentrations with time using electron spin resonance detection. The results are fully explained by the mechanism (1)–(4) H + H2S→H2+ SH, k1= 5.0 × 108 l. mol–1 s–1(1), H + SH → H2+ S, k2= 2.5 × 1010 l. mol–1 s–1(2), SH + NO → stable species, k3= 6.3 × 108 l. mol–1 s–1(3), SH + SH → H2S + S, k4= 7.8 × 109 l. mol–1 s–1. (4) with no evidence for significant surface effects (the walls were coated with boric acid). The results demonstrate conclusively that reaction (2) is very important in this system and that previous measurements of k1 which neglect this reaction may require correction.