2469.     ---------------.  [NIKITIN, N. I.]  [Hydrogen and Carbon Dioxide Absorption by Pyrophoric Iron, Nickel, and Cobalt.]  Ztschr. anorg. Chem., vol. 154, 1926, pp. 130-143; Chem. Abs., vol. 20, 1926, p. 3255.

        Experiments were carried out to determine the adsorption and solution of H2 and CO2 by pyrophoric Fe, Ni, and Co at different temperatures and pressures.  A specially constructed apparatus for this is illustrated and described.  Finely divided metals were obtained on slow reduction, in about 30 hr., of the respective carbonates with H2, the reduction temperature being kept at 525° for Fe and at 350° for Ni and Co.  The following results were obtained:  For 5 gm. Fe the maximum H2 adsorption at –185° and 667 mm. pressure was 8.3 cc.  At –80° and 16° there was virtually no adsorption, while at 380° and 500° there was again a larger adsorption.  The results obtained at different pressures exhibited in isotherms show an adsorption curve at –185°, following Freundlich’s equation:  a=βp1/n, where β and 1/n are determined constants.  A proof for the application of this equation is the straight line obtained on plotting log a against log p, the tangent to the angle between this end and X-axis being 1/n.  That surface adsorption and not solution occurred at –185° was proved by the easy removal of the H2 on evaluation, while the H2 taken up at 400° could be removed only by heating strongly.  The results obtained with Ni and H2 at –185°, 19° and 336° showed a maximum adsorption at 336°, which was 3.8 cm.3 for 5 gm. Ni at 714.9 mm. pressure.  The isotherm for 19° exhibits a straight line parallel to the X-axis and points to the formation of a superficial layer of Ni-H.  A similar formation is not present at –185° inasmuch as the isotherm stars at the O-point of the coordinate axis.  The isotherm for 336° starts below that of 19°, because the loose Ni-H compound dissociates at higher temperature and lower pressure.  Fe had a strong tendency to adsorb CO2, 1 vol. Fe taking up 35 vol. CO2 at ordinary temperature and pressure and 2 times as much at –80°.  Ni adsorbed virtually no CO2 at 335°.  The application of Freundlich’s equation for the CO2 adsorption by Ni at lower temperatures was not safe because of the small values obtained.  The results with Co and H2 were all uncertain.  Adsorption values for CO2 and Co were found between those for Fe and Ni.  5 gm. Co adsorbed 13 cm.3 CO2 at 14° and 760 mm. pressure.