THE CALORIMETRIC DETERMINATION OF THE HEATS OF ADSORPTION OF OXYGEN ON EVAPORATED METAL FILMS

Journal Article · Tue May 31 04:00:00 EDT 1960 · Proc. Roy. Soc. (London)

DOI:https://doi.org/10.1098/rspa.1960.0094· OSTI ID:4152844

Brennan, D; Hayward, D O; Trapnell, B M.W.

A Beeck-type calorimeter was used to measure the integral heat of adsorption of oxygen on evaporated films of titanium, chromium, manganese, iron, cobalt, nickel, riobium, molybdenum, rhodium, palladium, tantalum, tungsten, platinum, and aluminium. The variation of the heat with the extent of the adsorption was also determined, exc ept with palladium, platinum, and aluminium for which the amounts of oxygen adsorption were too small to allow this to be done. The overall error is not more than plus or minus 5 kcal/mole. The surface areas of the films were measured before and after an adsorption by the B.E.T. method; krypton isotherms at - 196 deg C were used for this purpose. From these data, it was possible to estimate the number of atoms of oxygen adsorbed per surface metal atom. In most cases, this quantity, togother with the heat of adsorption, can be related to the oxygen/ metal ratios and the heats of formation of certain oxides; this observation is remarkable in view of the limited extent of the adsorption. in the cases of rhodium, palladium and platinum the adsorption stops short of a monolayer and is probably true chemisorption rather than oxide formation. For those metals on which oxide formation occurs, the decrease in heat of adsorption with increasing coverage is interpreted in terms of an increase in the oxidation number of surface metal ions by electron transfer within the adsorbed layer. Some theoretical correlations between the heat of adsorption and the atomic and the bulk properties of the species concerned were examined and found of little value; an empirical relation with the metallic radius is given. (auth)

• Research Organization: Univ. of Liverpool; Imperial Coll. of Science and Tech., London; Denstone Coll., Uttoxeter, Staffordshire, Eng.
• Sponsoring Organization: USDOE
• NSA Number: NSA-14-016653
• OSTI ID: 4152844
• Journal Information: Proc. Roy. Soc. (London), Journal Name: Proc. Roy. Soc. (London) Vol. Vol: A256
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ADSORPTION
ALUMINUM
BET METHOD
CALORIMETERS
CHEMISTRY
CHROMIUM
COBALT
FILMS
HEATING
IRON
LOW TEMPERATURE
MANGANESE
MEASURED VALUES
METALS
MOLYBDENUM
NICKEL
NIOBIUM
OXIDES
OXYGEN
PALLADIUM
PLATINUM
RHODIUM
SURFACES
TANTALUM
TITANIUM
TUNGSTEN
USES