822.    EMMETT, P. H., AND BRUNAUER, S.  The Poisoning Action of Water Vapor at High Pressure on Iron Synthetic Ammonia Catalysts.  Jour. Am. Chem. Soc., vol. 52, 1930, pp. 2682-2693; Chem. Abs., vol. 24, 1930, p. 4693.

      Poisoning of synthetic NH3 catalysts by water vapor was studied at 450 at pressures as high as 100 atm. and at various partial pressures of H2O vapor between 0.08 and 0.64%.  

The amount of O retained by the catalyst is 

proportional to  ________     √PH2O : PH2

 Very active catalysts are capable of retaining more O than less active catalysts.  The poisoning of both doubly and singly promoted catalysts by water vapor is almost entirely reversible, although a slight permanent injury to the catalyst results.  A probable mechanism of NH3 synthesis consists in the reduction by H2 of surface Fe4N formed by the reaction of N2 with surface Fe atoms having average free energies sufficiently in excess of those of normal Fe atoms.