3049.     ---------------.  [SCHENCK, R.]  [Equilibrium relations Between Iron, Oxygen, and Carbon.]  Stahl u. Eisen, vol. 46, 1926, pp. 665-682; Chem. Abs., vol. 21, 1927, p. 1743.

        It is established from data on indirect reduction of Fe oxides by CO, that, in addition to magnetic Fe oxide and FeO, solid solutions of these in one another and in Fe take part in the equilibria as O-containing phases.  The probable presence of an Fe suboxide, stable only below 720°, is deduced from these equilibria.  The equilibria for the system Fe, Fe carbide, CO, CO₂ cannot be determined experimentally because of simultaneous oxidation, but data for the system Fe, Fe carbide, CH₄, H₂ are given, and from these the constants for the first named system are calculated.  The results are used to deduce the conditions for indirect cementation of Fe by CO and CH₄ well as for direct cementation processes.  From the equilibrium between Fe and CO below 600°, the existence of a per carbide of Fe, with a considerably higher C vapor pressure than cementite or elementary C, is rendered probable.  The equilibrium isotherms for CO-CO₂ in the presence of Fe are determined and from them a space model showing the relation between temperature, pressure, and concentration in the gaseous phase is constructed; from this a curve is derived for the relation of gas composition to temperature, which is very similar to curves experimentally obtained from observations on blast furnaces.  Information on the equilibria in ore-roasting processes is derived from these isotherms.