130.    BAHR, H. A., AND BAHR, T.  [Decomposition of Carbon Monoxide on Nickel.]  Ber. deut. chem. Gesell., vol. 61B, 1928, pp. 2177-2183; Chem. Abs., vol. 23, 1929, p. 756.

                  Metallic Ni or NiO catalyzes the reaction 2CO=C+CO2+38.9 cal. by first forming Ni3C.  Below 270°, the decomposition of CO continues until the Ni is completely transformed into Ni3C; then the reaction stops.  Between 270° and 380°-420°, the CO decomposition continues, the catalyst being Ni3C, which is free from metallic Ni.  This is proved by analysis, which shows that the amount of C bound chemically by the catalyst corresponds to Ni3C, excess C being present as the free element.  (To determine the ratio of bound C to free C, H2 is passed over the catalyst.  The amount of CH4 formed indicates the quantity of bound C.  Free C remains inert.)  Above 380°-420°, free Ni again appears in the catalyst because Ni3C dissociates at such temperatures.  Ni3C2 is probably an intermediary step in the decomposition of Ni3C.  It is believed that Ni3C formed in the catalysis process is identical with that isolated from fusions of Ni in the presence of C.