337.    BREDIG, G., AND ALLOLIO, R.  [X-Ray Studies of Catalytically Active Metals.]  Ztschr. Physik. Chem., vol. 126, 1927, pp. 41-71; Chem. Abs., vol. 21, 1927, p. 2204. 

                  Pt and Pd surfaces obtained by the glow discharge in H₂ at low pressures have been shown to be of very slight or negligible activity as catalysts for the hydrogenation of C₂H₄ or for the combination of H₂ and O₂.  These metal preparations contain considerable amounts of H₂ as evidenced by X-ray photographs, the presence of which in the metal lattice is responsible for lack of activity.  Ni, similarly prepared, is inactive at 350° in the hydrogenation of C₂H₄.  When Pt and Pd are prepared as above but in O₂ at low pressures, very active surfaces are obtained.  X-ray studies of these active Pt, Pd, and Ni surfaces have shown that except for differences in particle size, there is no difference between the finely divided, highly active, and the compact, slightly active metals.