Behaviour of electron acceptors in low-pressure acetylene oxygen flames

Abstract

Introduction of small proportions of electron acceptors such as chlorine or bromine into low-pressure acetylene + oxygen flames results in a marked reduction of the free electron concentration in the reaction zone. Quantitative studies of this effect by the cyclotron resonance technique suggest strongly that for halogen it is caused principally by formation of negative halide ion, B^–, through the balanced process HB + e^–⇌ H + B^–. The results are also shown to yield information about the extent of disequilibrium in the reaction zone. On the basis of this mechanism, the electron affinities of chlorine and bromine are deduced to be 83.0 ± 0.5 and (E.A._CI–4.5)± 0.5 kcal/mole respectively, which are in satisfactory agreement with the values of 83.33 and 77.55 kcal/mole obtained by Berry and Reimann through a photodetachment procedure. Traces of cyanogen, sulphur compounds and ammonia also produce large reductions in electron concentrations. Possible explanations of these effects in terms of electron acceptors are considered.