IMMERSION CALORIMETRY AND ADSORPTION STUDIES: HYDROPHOBIC AND HYDROPHILIC SURFACES AND THE SORPTION OF WATER VAPOR BY OXIDE COATED METALS
Abstract
Heats of immersion in water were obtained for asbestos, rutile, Graphon, and silica with a calorimeter which employed a thermistor as the temperature-sensing element. For asbestos on which various fractions of a water monolayer had been adsorbed, the heats decreased linearly with surface coverage. This behavior, together with the shape of isoteric heat curves, indicated the homogeneity of the asbestos surface. Absolute entropies of water adorbed on asbestos were calculated. A study was made of oxide films on Ni, steel, and Mo surfaces. Ni and steel powders degassed at 25 deg C exhibited only physical water adsorption; the heats of emersion were both 550 ergs/sq cm. The heat of emersion of Mo degassed at 25 deg C was 9500 ergs/sq cm. Degassing Ni powder at 300 deg C raised the heat of emersion to 950 ergs/sq cm. Activation of steel at 400 deg allowed 10 to 13 layers of water to be adsorbed, indicating the presence of a polymolecular hydrous oxide film; Mo activation decreased the amount of water sorbed/unit area. Adsorption isotherms and heats of immersion were measured for the Graphon-water system. Isoteric heats of adsorption and absolute entropies of the adsorbed state were calculated. The former were much less than the heat of liquefaction and had a minimum value of 5.5 kcal.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 31, 1953
- Accession Number
- AD0017613
Entities
Organizations
- Lehigh University