The fate of arsenic in a laminar diffusion flame

An arsenic compound (cacodylic acid) has been added to laminar diffusion flames burning in a co-flowing stream of air. Two fuels were used viz. ethene (C2H4) and a mixture of hydrogen and nitrogen. Samples of aerosols and gaseous species were collected within the flames and above the flames with filters and sorbent tubes. The hydrogen flame showed the conversion of arsenite to arsenate with increased residence time through the flame. The conversion of arsenite to arsenate in the ethene flames was inhibited by the emission of soot, which apparently competed with the arsenic for oxygen in the postflame gas. Arsenic was not found to be incorporated into soot particles. The carbon and arsenic were present in the posflame gases as two distinct aerosol phases. The addition of arsenic did not have a significant effect on the formation and oxidation of soot. The addition of arsenic did not lead to the production of organoarsenic species; only common polycyclic aromatics were found in the sooting flames.