Activated Adsorption of Hydrogen in the Neighbourhood of the Curie Point

Abstract

IN catalytic phenomena the ferromagnetic metals (iron, cobalt, nickel) possess a special interest. On the other hand, it is also known that adsorption phenomena are closely connected with catalysis. In continuation of systematic work carried out during recent years in this laboratory on adsorption phenomena, we measured the adsorption of hydrogen on nickel sheets between 200° and 400° C. The nickel is thoroughly cleaned by washing it successively with hydrogen and pumping off for several hours at 600° C. at a pressure lower than 10^-6 mm. Special care is taken with the purification of the hydrogen. The measurements have been made with pressures up to 1 cm. It is found, first, that the equilibrium is very rapidly reached (30 sec.); secondly, adsorption increases with increasing temperature; thirdly, in the neighbourhood of the Curie point (358° C.) the isobars show a very pronounced discontinuity (see graph).