The behaviour of gases in contact with glass surfaces

Abstract

That glass surfaces possess the property of taking up small quantities of gases is a fact of considerable interest to those engaged in accurate gas measurement. If, as seems probable, this property is closely connected with the "wetness" or "dryness" of the glass surface, the success of any quantitative experiments will depend on the constancy of the water content. Complete desiccation of glass may be impossible even at the melting-point, but Sherwood's experiments indicate that glass which has been heated for a long time at a particular temperature loses very little further water on subsequent heating at or below that temperature. In order to obtain a large surface, a quantity of fine glass wool was packed into a glass tube. The density of the material and the length per gram had been determined, so that the surface could be estimated. The wool was cleaned in situ with chromic and sulphuric acids, well washed with distilled water, and dried, After sealing to the apparatus the tube was electrically heated in vacuo for several days to a constant temperature in the neighbourhood of 200° C., the system being exposed to charcoal cooled in liquid air. The same treatment—but for a shorter time—was applied to the wool after each sorption experiment.