ADSORPTION PHENOMENA ON IONIC ADSORBENTS.
Abstract
The adsorption of water vapor on ionic crystals was investigated between 0 and -45 C. With vacuum deposited films of KC1, the isosteric log plots at low coverage showed a break at about -25 C, indicating a higher heat of adsorption at the higher temperature. The heats of adsorption at the higher temperature showed no significant variation with coverage, while those at the lower temperature increased sharply from 3 kcal per mole to a constant level corresponding to the heat of liquefaction of water. The silver halides and PbF2 gave an inflexion in the early stages of the isosteric heat curve, explicable, semi-quantitatively, on the basis of lateral interactions between square arrays of adsorbed molecules. With CaF2 and PbI2, the crystal structure of the adsorbent seemed to be the dominant feature in determining the adsorptive properties. Two-dimensional condensation occurred on CaF2 and a mechanism of adsorption by hydrogen-bonding was proposed. The heats of adsorption at various stages of the photochemical decomposition of AgBr were tentatively explained in terms of adsorption in surface cation vacancies. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 31, 1961
- Accession Number
- AD0282141
Entities
Organizations
- Imperial College London