The chemical processes within high-density CO/H-2 plasmas are examined using supersonic pulse, plasma sampling mass spectrometry. The principle chemistry observed is consistent with a Fischer-Tropsch process and results in the formation of primarily formic acid and a C2O2Hx species tentatively identified as ethenediol. The high-density plasmas used are shown to etch nickel. (c) 2005 American Vacuum Society.