Relation between ion creation and C 2, CH and OHformation in the combustion of hydrocarbons

Abstract

In the previous paper, studies on C 2 , CH, and OH emission and ion formation in the reactionof acetylene and oxygen ignited by a strong luminous flash were described, and a sequence of chemical reactions responsible for producing the radicals and ions was proposed. The weak point of the experiments was the need to photosensitize the mixture with a small amount of nitrogen dioxide (NO 2 ), which may affect acetylene-oxygen reactions. One of the purposes of our present study was to determine the effect of the nitrogen dioxide.The results already reported were compared first with those obtained using 1-3-5 cycloheptatriene (C 7 H 8 ), the reaction of which is initiated by a flash without nitrogen dioxide. The results were then compared with those obtained when an acetylene-oxygen mixture without nitrogen dioxide is ignited by a microwave. Since no difference, at least no qualitative difference, was observed, it was proposed that nitrogen dioxide does not essentially affect emission and ion formation. Next, various hydrocarbons, other than acetylene, were examined, but no notable difference was found insofar as emission and ion formation were concerned, which was to be expected from the well-known theory that hydrocarbons generally produce acetylene during chain reactions. The present paper also reports on a vacuum ultraviolet light emitted for a short time by the reacting mixtures. This uv light has a photoelectric effect on the electrodes used in the combustion tube to detect ions, and charges them positively. It is suggested that the radical responsible for this is CO (A 1 II).