476.    ---------------.[CHAUDRON, G.]  [Reversible Reactions of Hydrogen and Carbon Monoxide on Metallic Oxides.]  Ann. Chim., vol. 16, 1921, pp. 221-281; Chem. Abs., vol. 16, 1922, pp. 212-213.

                   Apparatus combined features previously used with modifications designed to effect continuous slow circulation of the gas phase over the solid phases and to require a single thermostat well removed from the furnace.  The composition of the gas phase was determined at intervals, pH O-pH by tension measurements Cco-Cco₂ by refraction with an interferential method shown to be capable of detecting a variation of 0.5% in composition.  Equilibrium was determined by both oxidation and reduction experiments.  The triple point at which Fe, FeO, and Fe₃O₄ coexist was found to be 570°, the data being concordant for both gas phases.  Above 570° the equilibrium curve has 2 branches corresponding to Fe+H₂O=FeO+H₂ (and Fe+CO=FeO+CO) and 3FeO+H₂O(CO₂)= Fe₃O₄+H₂(CO).  Below 570° 1 system only exists:  3Fe+4H₂O(CO₂)=Fe₃O₄+4H₂(CO).  The triple point corresponds to the invariant system 4FeO=Fe₃O₄+Fe.  This transformation was directly observed by maintaining below 570° FeO prepared at high temperature, 900°, and using metallographic methods and appearance of ferromagnetic properties.  The diagram, temperature-gas composition, fixes the conditions for preparing Fe, FeO, and Fe₃O₄.  The following equilibria were also studied:  CO+H₂O=CoO+H₂; Mo+2H₂O=MoO₂+2H₂; W+2H₂O=WO₂+2H₂; 2WO₂+H₂O=W₂O₃+H₂.  The last confirm the existence of the oxides WO₂ and W₂O₃ and the diagram fixes the conditions for preparing WO₂.  Ni, MnO, and UO₂ are not oxidized by water vapor.  From the measurements of the systems Fe+H₂O(CO₂)=FeO+H₂(CO) values of the water-gas equilibrium K=(C_coC_H2O-C_CO2C_H2), are calculated for 686°, 786°, 886°, and 986° in excellent agreement with Haber’s values.  For K=1 was found 810°; Haber, 825°.