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THE use of evaporated carbon films for adsorption studies is desirable in view of the difficulty of outgassing carbon powder. By analogy with the comparative properties of metal surfaces produced by evaporation and by reduction of powders, it seems likely that evaporated carbon should be significantly cleaner and more reproducible.

THE well-known dissociative adsorption of hydrogen on transition metal films has been reported1 not to occur on evaporated copper films. Copper is catalytically active in hydrogenation reactions, and copper powders prepared by reduction of the oxide have been shown2 to adsorb hydrogen. It is not certain that the surfaces were clean and it has been suggested3 that the observed adsorption may be due to impurities. Kwan4 found a slight activated chemisorption at high temperatures on very carefully reduced copper powder.