2087.     LEIBU, H. J.  [Reduction of Iron Oxides by Hydrogen and Carbon Monoxide.]  Schweiz. Arch. angew. Wiss u. Tech., vol. 14, 1948, pp. 1-19, 49-59, 76-85; Ind. Chemist, vol. 24, 1948, p. 267; Chem. Abs., vol. 42, 1948, p. 4881.

        This study was carried out in 2 steps:  (1) Determination of the best conditions for reduction in which the action of the gases on pure Fe₂O₃ of varying grain size and porosity was examined; (2) the same reduction process in the presence of other oxides forming the gangue and ores with a low % of Fe₂O₃.  The action of H₂ is more effective than CO, being endothermic, while the latter is exothermic; it is about 3-4 times great at 800°, but this ratio decreases at lower temperatures.  At temperatures above 800°, CO disintegrates, forming CO₂ and C, so that Fe free from C cannot be obtained.  The physical factors are similar in effect with both gases.  Confirmation that H₂ eliminates S and O₂ simultaneously was not forthcoming; indeed, the elimination of O₂ is more rapid and that of S (with P) forms a different process.  The reaction is influenced by the chemical composition and crystalline structure of the other oxides present, but their effect is only conspicuous if the ore consists of certain mixed crystals before or during the reaction.  Under these circumstances the reaction is, thereby, not merely slowed down but is brought to a standstill, products being formed that resist reduction.  Proof of this was obtained by spectral analysis.  Reduction is virtually total (a) for ferrites (for example, 2 CaO. Fe₂O₃) where Fe is the active cation, while in other ferrites it is inactive; (b) for ferrites where O₂ is combined mainly or solely with Fe (for example, FeO₄MgFe).  Reduction is more or less impossible:  (a) In the presence of mixed crystals containing ferric or ferrous oxides in small quantities so that the groups (FeO₆), (FeO₄), are surrounded by crystals of alien cations, for example (Al, Fe)₂O₃ (Mg, Fe)O; (b) in the presence of intermediate crystals (SiO₄Fe₂) or (FeO₄Al₂) where the O₂ belongs not only to (FeO₆) or (FeO₄) groups but to the (SiO₄) or (AlO₆) groups as well.

        LEIBUSH, A. G.  See abs. 1670.