767.    ECKSTROM, H. C., AND ADCOCK, W. A.  New Iron Carbide in Hydrocarbon-Synthesis Catalysts.  Jour. Am. Chem. Soc., vol. 72, 1950, pp. 1042-1043.

     During the course of hydrocarbon-synthesis investigations, X-ray diffraction patterns of certain catalyst samples have indicated the presence of a new Fe carbide phase.  The new carbide appeared along with Fe₃O₄ and Fe₂C (Hägg) during a fluidized synthesis run at 27 atm. pressure and 360°, and eventually it constituted approximately 90% of the total catalyst charge.  The X-ray diffraction pattern is shown in comparison with those of Fe₃O₄ and Fe₂C (Hägg).   The d/n values and relative line intensities are given also.  The new carbide is ferromagnetic; and, within the limits of experimental error, its Curie temperature is the same as that of Fe₂C (Hägg), (250° + or –3°).  After heating the sample for 10 min. at 600°, an X-ray diffraction pattern showed that the carbide had been converted partly to cementite, Fe₃C; after 30 min., all the carbide had been converted into Fe₃C.  A chemical analysis gave 77.4% Fe and 17.4% C.  This gives an Fe : C ratio of 0.96, so that the new phase could be equivalent to FeC.

     EDEBURN, P. W.  See abs. 3150, 3151, 3152.