2618.     ---------------.  [PETCH, N. J.]  Interpretation of the Crystal Structure of Cementite.  Jour. Iron Steel Inst. (London), vol. 149, 1944, pp. 143P-150P; Chem. Abs., vol. 38, 1944, p. 4891.

        Cementite is essentially a framework of close-packed Fe atoms with the small C atoms in the largest interstices held in place by metallic bonding.  The lattice parameters of cementite have a small but systematic and definite decrease with increasing quenching temperature.  Variation in the Fe:C ratio is the explanation of the lattice parameter variation.  The most possible variation in composition is by omission of C atoms to a limited extent.  9 refs.

        ----------.  See abs. 2120.