1218.    GOODEVE, C., AND JACK, K. H.  Kinetics of Nitrogen Evolution From an Iron-Nitrogen Interstitial Alloy.  Disc., Faraday Soc., No. 4, 1948, pp. 82-91; Chem. Abs., vol. 43, 1949, p. 4933.

       Rate of N evolution from e-Fe nitride at 350°-500° is given by a 2d-order equation with respect to interstitial N concentration and is associated with an activation energy of 42,100±1,400 cal. per gm. mol.  The evolution rate of N atoms per 100 Fe atoms per sec. is given as r=2 ≈ (10²/A)=(10² Newn/A)e^-E/RT, where A is the number of Fe atoms in the nitride particle.  The approximate value for the successful collisions w is taken as 3 A.  From the known structure of e-nitride and the observed particle diameter N, n and A are known.  At 450°, the values are c=1.05X10⁵ cm. per sec.; N=1.9X10⁸; n=3.8X10¹⁴; A=2.3X10¹².  Thus, at 450°, r ranges from 0.7-4.3X10^-3 with a most probable value of 1.8X10^-3 N atoms per 100 Fe atoms per sec.  The velocity of diffusion of N atoms to the surface is at least 10⁴ times as rapid as the rate-determining process.  The rate-determining stage of the reaction is considered the combination of N atom pairs at the solid surface.  By calculation of the collision frequency on the assumption that this surface reaction behaves as in a 2-dimensional gas, the correct order of magnitude for the absolute reaction rate is predicted.

        GOODMAN, J. B.  See abs. 2576, 2577.