826.    ---------------.  [EMMETT, P. H., AND BRUNAUER, S.]   Use of Adsorption Isotherms for Measuring the Surface Areas of Catalysts and Other Finely Divided Materials.  Trans. Electrochem. Soc., vol. 71, 1937, 12 pp. (preprint); Chem. Abs., vol. 31, 1937, p. 3371.

     Describes method for measuring the surface areas of catalysts, and of other finely divided substances, by using low-temperature adsorption isotherms of gases such as N2, A, CO, O2, and CO2.  Representative isotherms for 2 promoted Fe-synthetic-NH3 catalysts, pumice, Ni on pumice, and NiO on pumice are presented.  In the case of the Fe catalyst, it is shown that if the beginning of  the linear portion of the isotherms is interpreted as the point of completion of a unimolecular layer, surface areas can be calculated that are approximately the same for all gases tried.  Furthermore, the surface areas so calculated are large enough to accommodate the observed chemisorption of CO at 183 and the largest irreversible adsorption of H observed at 78-100.  Only in the case of O at 183 is the volume taken up irreversibly by the catalyst several fold greater than a monomolecular layer.  Presumably O reacts chemically with the outer layers of Fe atoms even at 183.  The method has so far been applied with apparent success to the catalysts and catalyst supports mentioned above and in addition, to 4 other synthetic NH3 catalysts, 2 Cu catalysts, glaucosil, 2 soils and 2 soil colloids, samples of dry powdered bacteria, Cr oxide gel, and Cr oxide gel that had been glowed at 400.