Mass spectrographic studies have been conducted on the positive ions and neutral species in glow discharges containing 1.0% each of SO2and CO in helium and also 1.1% each of SO2and CO2in helium. Ion species observed in these mixtures included S+, SO+,SO2+,O+,O2+C+, CO+, andCO2+with lesser amounts ofSO3+,[CO]2+, SCO+, and [SO·CO]+(orCS2+). The functional dependencies of the various ion and neutral species on pressure and discharge current for He&sngbnd;SO2&sngbnd;CO mixtures were consistent with the interpretation that CO reacted with the SO formed in the discharges to produce CO2and sulfur. Measurements in He&sngbnd;SO2&sngbnd;CO2mixtures also indicated the removal of SO2through the formation of CO2and S.