Surface-area determination by adsorption of nitrogen from nitrogen-helium mixtures

Abstract

A new apparatus and technique, in which vacuum pumps and associated eq uipment are not required, have been developed for the determinatiolJ of the adsorption of nitrogen from mixtures with helium for use in the determination of surface area. The sample is heated initially in a stream of helium. The adsorption of helium is negligible at the temperatures concerned. The gas mixture is cycled repeatedly over the adsorbent until no flll'thel' change in pressure is observed. Temperature equilibration is attained rapidly. It is shown that thermomolecular pressure differences are negligible under the conditions of the experiment. Surface-area determinations by the simplified technique are in good agreement with results obtained by the conventional volumetric method when the same adsorbents are used with various residual helium pressures.