3439.    TRILLAT, J. J., AND OKETANI, S.  [Electron-Diffraction Study of the Cementation of Iron.  I.  Action of Pure Carbon Monoxide.]  Compt. rend., vol. 230, 1950, pp. 2,203-2,205; Chem. Abs., vol. 44, 1950, p. 10,631.

        Extremely thin polycrystalline films were prepared by vaporizing from pure Fe or mild steel onto the surface of freshly cleaved rock salt; the salt was then dissolved in H₂O and the metallic film collected on a Ni grill.  This was submitted to cementation in the presence of pure CO and then examined by electron diffraction.  After cementation at 540°, orthohombic crystals of cementite are present.  Below 500° none is formed.  At 540°, if the preparations are not exposed constantly to fresh CO₂, decomposition takes place forming Fe₃O₄.  As the temperature is raised, graphite is deposited on the surface, and above 820° the diagrams of Fe and Fe₃C are masked.