A study of sensitized explosions. V. Some new experiments on the hydrogen-oxygen reaction sensitized by nitrogen peroxide

Abstract

The effect of pressure and temperature of reactants, of inert gases, of vessel diameter and of surface condition on the induction periods and explosion boundary of 2H 2 + O 2 mixtures containing nitrogen peroxide have been determined in the temperature range 350-410° C. The principal results may be summarized: ( a ) Increase of pressure causes the separation of the upper and lower limiting concentration of sensitizer to increase from zero to a maximum value at the inversion pressure. Above this pressure the upper limit decreases and the lower limit increases linearly with increase of pressure. The induction periods of H 2 -O 2 -NO 2 mixtures of constant NO 2 content decrease rapidly with increase of pressure, approaching a small value asymptotically. ( b ) All foreign gases lengthen the induction periods and eventually quench the ignition of an explosive mixture of H 2 -O 2 -NO 2 of constant composition. The order of efficiency of the non-reactant gases in lengthening the induction periods is CO 2 > N 2 > A = He, whereas the order of efficiency in quenching ignition is CO 2 > He > N 2 > A. ( c ) The induction period at the upper limit always exceeds the induction period at the lower limit. The reverse is true of the rates of the slow reactions in the vicinity of the limits. ( d ) At constant total pressure, rise of temperature causes the upper limit ( P u )to be raised according to the equation log P u = E / RT + constant. E is 19,500 cal. at a total pressure of 75 mm. and increases with pressure to 25,600 cal. at 472 mm. ( e ) At constant pressure the upper limit decreases and the lower limit increases as the reciprocal of the square of the diameter