3267.     STEFANOVSKIĬ, A. M., TATARSKIĬ, E. S., AND ZELYAKOV, N. V.  Dependence of the Structure of an Ammonia Catalyzer Upon the Conditions During Its Reduction.  Compt. rend. acad. sci. U.R.S.S., vol. 3, 1935, pp. 21-24 (in English); Chem. Abs., vol. 29, 1935, p. 8244.

        Catalyzer prepared by oxy-acetylene fusion consisting mainly of 72% Fe₂O₃ and 27% FeO was reduced at temperatures 450°-800°.  Its efficiency dropped abruptly from 61% for that prepared at 500° to 2% for that prepared at 600°.  X-ray studies of changes involved show that the fall in activity cannot be accounted for by a change in size of the crystals but to a qualitative change of the surface.  At higher temperatures, the defects, which are the active centers in NH₃ synthesis, disappear.  This illustrates the use of X-ray photographs in the study of active centers.

        STEFFENS, L. R.  See abs. 1460.

        STEIN, K.  See abs. 1449a.