1277.    ----------------.  [GUERTLER, W.] [Law Governing the Transformations of the Carbide System Into the Graphite System.]  Stahl u. Eisen, vol. 34, 1914, pp. 520-525, 751-754; Chem. Abs., vol. 8, 1914, p. 3002.

       Discusses Fe-C diagram in detail.  Fe₃C is unstable at all ordinary temperatures, but the transformation energy is so weak that it must be heated for hours at 800° before it breaks down.  With increases in temperature, the time required for decomposition is shorter.  In spite of the instability of Fe₃C, it is possible, under certain conditions, to cause the reaction Fe₃C=3Fe+C to reverse.  If the tendency to form graphite is stronger than the force tending to decompose Fe₃C, the speed of the reaction is governed by the former force.  There is some doubt as to which of these forces is influenced by the presence of Si.  The separation of graphite is accompanied by increase in volume; consequently, its formation is retarded by pressure.  The main factor is, however, temperature, and it is by varying this that foundries obtain the various results they desire.  Gives diagram that shows graphically the relative amounts of free and combined C with different temperatures; by means of it the changes during cooling are discussed.

       GUEST, P. G.  See abs. 1449.