3671. WEVER, F. [Iron Carbide.] Mitt. Kaiser Wilhelm-Inst. Eisenforsch. Düsseldorf, vol. 4, 1922, pp. 67-80; Chem. Abs., vol. 18, 1924, p. 1460. By X-ray analysis, it is proved that the forms of cementite shown in the Fe-C thermal diagram are not distinguishable by their lattice structure. Fe_{3}C crystallizes in a rhombic lattice denoted by the quadratic form sin^{2}θ/2=0.0464x^{2}+0.0367y^{2}+0.0208z^{2}. The edge lengths are a=4.481 Å., b=5.034 Å., c=6.708 Å. The density is calculated therefrom as 7.82. Data by the Debye-Scherrer method above 210° show that the magnetic transformation is not associated with a change in the type of lattice. The quadratic form is expressed by sin^{2}θ/2=0.0456x^{2}+0.0362y^{2}+0.0203z^{2}. The edge lengths are a=4.52 Å., b=5.08 Å., c=6.77 Å. |