A study of sensitized explosions. VII. A chain-thermal theory of the reaction between hydrogen and oxygen sensitized by nitrogen peroxide or nitrosyl chloride

Abstract

Both these reactions are chain processes for which the net branching factor ɸ is inversely proportional to the induction period. By applying this relation to the experimental results described in Parts V and VI, it is shown that ignition only occurs when the net branching factor attains a value determined by the sum of two quantities, one proportional to the thermal capacity and the other proportional to the thermal conductivity. It is pointed out that this ignition condition cannot be accounted for by any isothermal theory of ignition, but that it may readily be deduced from a thermal theory in which explosion is visualized as occurring only when the initial reaction rate, in a favourable volume element, is large enough to ensure that a critical temperature T c is reached in a critical time t c . Theories of reaction kinetics are developed from these two systems which give ɸ in terms of the experimental variables. The expressions so deduced lead to a dependence of the induction period on these variables identical with that found experimentally. The effects of vessel diameter, surface condition, temperature, and concentrations of sensitizer, reactants and foreign gases on the explosion are satisfactorily accounted for by substituting these expressions in the ignition condition of the chain-thermal theory.