Accession Number : AD0735539

Title :   Phase Transitions of Adsorbates. Part 2. Vapour Pressure and Extension Isotherms of the Porous-Glass plus Water System Below 0C,

Corporate Author : NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO) DIV OF BUILDING RESEARCH

Personal Author(s) : Sidebottom,E. W. ; Litvan,G. G.

Report Date : 19 OCT 1970

Pagination or Media Count : 15

Abstract : The vapour pressure and extension isotherms of the water-porous 96% silica glass were determined at +1.5, -6.4, -14.6, 25.4 and -35.3C. Isotherms obtained at these temperatures coincided if the amounted of adsorbed water, a, was plotted against the relative pressure with reference to that undercooled water. This demonstrates that the isothermally adsorbed water is in a liquidlike state and confirms that the drastic reduction of a with declining temperature is due to a decrease of maximum relative pressure that can be realized experimentally. In contrast to previous studies, a minimum in the extension isotherm at low concentration was found, indicating that adjacent hydrogen-bonded silanol groups of the glass may not be the site of water adsorption as has been assumed in the past. (Author)

Descriptors :   (*PHASE STUDIES, *ADSORPTION), (*SURFACES, ADSORPTION), (*GLASS, ADSORPTION), VAPOR PRESSURE, TRANSITION TEMPERATURE, WATER, SILICON DIOXIDE, CANADA

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE