3505.     ---------------.  [TUTIYA, H.]  Catalytic Decomposition of Carbon Monoxide.  IV.  Behavior of Nickel Carbides.  Bull. Inst. Phys. Chem. Research (Tokyo), vol. 10, 1931, pp. 951-973, abs. 83-84; Sci. Papers Inst. Phys. Chem. Research (Tokyo), vol. 16, No. 328-329, 1931; Chem. Zentralb., 1932, I, pp. 782-783; Chem. Abs., vol. 27, 1933, p. 1809.

        An X-ray investigation of the catalytic decomposition of CO by Ni or NiO has confirmed the formation of Ni₃C n a percarbide, Ni_χC.  The percarbide is formed from NiO at 270° and rapidly decomposes into Ni₃C and C at 284°; it also is decomposed by atmospheric H₂O vapor.  Ni₃C is quite stable at 285° and catalyzes the decomposition of CO.  In the temperature range of stability of Ni₃C, the reaction 3Ni+2CO=Ni₃C+CO₂ is possible, but not reaction 2CO=C+CO₂.  Free Ni is found in the earlier stages of reduction of NiO, but later changes completely to carbides.