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.