Krypton adsorption and the surface area of silica

Autor: K. S. W. Sing, D. Swallow
Rok vydání: 2007
Předmět:
Zdroj: Journal of Applied Chemistry. 10:171-175
ISSN: 1934-998X
0021-8871
Popis: Details are given of the apparatus used for measuring adsorption isotherms of krypton at −196°, which allowed a rapid and precise measurement of pressure. Surface areas have been calculated, by the B.E.T. method, from the krypton adsorption isotherms on samples of ground quartz and a silica gel. The surface areas of the quartz samples determined by other workers, using B.E.T. nitrogen adsorption and electron microscopy, agreed well with the krypton values, provided that the atomic cross-sectional area of krypton was taken as 19·5Ǎ2. It was not possible to obtain a ‘standard’ curve from the krypton adsorption isotherms on the non-porous silicas, but when these isotherms were plotted in logarithmic form, all gave a substantial linear region with the same slope. The logarithmic plot of the isotherm on the silica gel had a different slope; it would seem likely, therefore, that capillary condensation occurred on this sample at low pressure and that the B.E.T. area is invalid here.
Databáze: OpenAIRE