NOTE ON THE MODEL OF METALLIC ADSORBENT OF HYDROGEN By

The two current models of metallic adsorbent, i. e. the crystal plane mode!',,) and that underlying the distribution function methodS) are reviewed with regard to their experimental grounds with special reference to the dissociative adsorption of hydrogen. In the crystal plane model, sites of hydrogen adatoms form lattice planes respectively congruent with the basic lattice planes on the surface of adsorbent metal crystal, the sites on the same lattice plane are practically physically identical with each other and there exist appreciable repulsions be· tween adatoms thus situated near to eClch other. In the model underlying the distribution function method, sites are distributed over the energy of adatoms on the sites, which is peculiar to each site irrespective of the arrangements of other adatoms. The latter model leads') from the observed adsorption isotherms inevitably to a distribution function, which varies considerably with temperature under the condition, where the rearrange· ments of basic metal atoms, hence the variation of the distribution function is excluded. The results of the differential isotopic method12 \ usually accepted as an exclusive evidence for the model, are shown, on the other hand, equally accounted for on the basis of the crystal plane modeP')