Chlorides can be intercalated in graphite either directly or from their solutions in various reagents. Chlorosulfonic acid, which dissolves a large number of chlorides, can be intercalated in its pure state only by means of chemical or electrochemical oxidation. Three types of reactions have been observed between graphite and the solutions of chlorides in this acid. 1. (i) Insertion of chlorosulfonic acid, d i 8.03 A ̊ , with CuCl 2, ZnCl 2, HgCl 2, PbCl 2, MnCl 2, CoCl 2; AlCl 3, CrCl 3, FeCl 3; SiCl 4, SnCl 4, TiCl 4, ZrCl 4; PCl 5, NbCl 5, TaCl 5. The reaction temperature and the stage seem to be related to the redox potential of the M n+/M couple. 2. (ii) Formation of ternary compounds, d i ≌ 8.36 A ̊ , with BCI 3. 3. (iii) Formation of two-phase systems: one graphite-HSO 3Cl phase, d i ≌ 8.10 A ̊ ; one graphite-chloride phase, di is that measured with the free halogenide with AuCl 3 and SbCl 5. SbCl 3 gives the same results as SbCl 5. This exploratory study allows us to envisage the preparation of new ternary graphite-halogenide-acid compounds. Furthermore, the formation of two-phase systems does not seem to have been described by other authors.