Ultraviolet Absorption Spectra and the Chemical Mechanism of CS2–O2 Explosions

Abstract

Ultraviolet absorption spectra have been obtained at various times during and after homogeneous explosions of carbon disulfide‐oxygen mixtures thermally initiated at temperatures of 190 to 300°C. This has been accomplished by triggering a flash source of continuum by means of the early chemiluminescence of the explosion. These photographically recorded spectra show the presence, and the absorption intensity as a function of time, of CS, SO, SO₂, S₂O₂, S₂, CS₂ and a species which absorbs in a continuum, to which has been assigned the structure of a sulfur superoxide, SOO. Numerous conclusions have been reached from these data concerning the elementary chemical reactions that are involved in these experiments. A direct bimolecular reaction is postulated for the initiation process which produces the superoxide, and eventually free radicals. In the very early stages of the explosion, propagation proceeds via a slowly branching primary chain which involves an attack on the reactants by sulfur and oxygen atoms. As the branching reaction proceeds and the temperature increases, the mechanism undergoes a number of changes including an increase in the importance of a nonfree radical, bimolecular process. The explosion is especially interesting in that one of the final products, sulfur dioxide, does not appear in more than minor concentrations, almost characteristic of an intermediate, until the explosion is over. This is explained in terms of the reactions postulated.