2085.     ---------------.   [LEHRER, E.]  [Equilibrium, Iron-Hydrogen-Ammonia.]  Ztschr. Elektrochem., vol. 36, 1930, pp. 383-392; Chem. Abs., vol. 24, 1930, p. 4207.

        Many experiments in which Fe was vitrified with H2-NH3 mixtures were carried out, and the resulting nitrides were examined by magnetic methods (abs. 2084).  The equilibrium diagram of Fe-H2-NH3 showed four phases, a, γ, γ’ and ε representing five divariant equilibria and two univariant with the phases a, γ, γ’ or γ, γ’ and ε as solid phases, 350°-750°.  The a phase is a fixed solution of N in a-Fe, 0-0.5% N; the γ phase is a fixed solution of N in γ-Fe, 1-2.7% N; the γ’ phase, Fe4N mixed crystals 5.5%-6% N; ε phase 4.5-11% N.  The dissociation pressures were calculated from the Haber values for NH3 equilibrium.  The dependence of the results upon the concentration of NH3 showed that the γ’ phase does not form in demonstrable amounts under normal working conditions.