836.    EMMETT, P. H., HENDRICKS, S. B., AND BRUNAUER, S.  Dissociation Pressure of Fe₄N.  Jour. Am. Chem. Soc., vol. 52, 1930, pp. 1456-1464; Chem. Abs., vol. 24, 1930, p. 2940.

     By a flow method it was determined that at 1 atm. pressure the % NH₃ in a gaseous H₂-NH₃ mixture in equilibrium with an Fe-Fe₄N mixture is 36 at 420°, 30 at 444°, 28.5 at 460°, and 17 at 525°.  The dissociation pressures of Fe₄N at these respective temperatures are calculated to be 4,250, 4,300, 5,400, and 5,600 atm.