The reaction of graphite with sulfuric acid in the presence of KMnO 4 (oxidant : graphite ratio 0.02730.55) involves consecutive and concurrent reactions : graphite intercalation and direct oxidation of the carbon matrix. The properties of graphite bisulfate and its reaction products are determined by the stage number of the intercalation compound; the decomposition enthalpies of the stage I3IV graphite bisulfate correlate with the enthalpies of graphite intercalation with sulfuric acid.