3095.     ---------------.  [SCHMIDT, J.]  [Nonexistence of a Higher Nickel Carbide.]  Ztschr. anorg. Chem., vol. 216, 1933, pp. 85-98; Chem. Abs., vol. 28, 1934, p. 1618.

        Since Fe forms a higher carbide and since H Tutiya had reported detecting a  higher Ni carbide, (abs. 3505) Schmidt attempted to prepare it by X-ray analysis.  CO was passed over Ni (reduced by H₂) for 240-465 hr. at 240°-250°.  All samples of carbide thus obtained contained 0.4-1.3% free C and 6.8-7.8% combined C.  Although the latter was higher than the theoretical (6.37%) for Ni₃C, this was the only compound detected by X-ray studies.  As all the possible places for C in the space lattice of Ni₃C are not filled, Schmidt assumes that the excess C takes some of these places without distorting the crystal.  The density of Ni₃C computed from crystal data is 7.880 gm. per cc.; the experimental value (d²⁵₄) was found to be 7.957 gm. per cc.  The excess C in the crystal may help account for the difference.  The products of decomposition with acids were CH₄, C₂H₆, C₂H₄, and H₂, all being evolved in varying proportions.  The results of decomposition were not reproducible.  When CH₄ was passed over Ni, C was formed but no carbide.  C₂H₂ gave Ni₃C and much C.  Bibliography.