636.    CRAWFORD, V. A., AND TOMPKINS, F. C.  Adsorption of Gases Sulfur Dioxide, Ammonia, Carbon Dioxide, and Nitrous Oxide on Barium Fluoride Crystals.  Trans. Faraday Soc., vol. 44, 1948, pp. 698-708; Chem. Abs., vol. 43, 1949, p. 2485.

     Adsorption was determined between –78° and 119°, and it was reversible and complete within 5 min. of gas admission at all temperatures.  The Brunauer-Emmett-Teller plots are linear except at low pressures (p), where departures were anticipated.  The volume adsorbed tends to be too small at high pressure (p), in keeping with the decrease in the heat of adsorption.  The latter was determined by use of the Clausius-Clapeyron and the B.E.T. equations.  The decrease of heats with coverage found by experiment is compared with those expected theoretically.  Variation in adsorption potential over the crystal surfaces was calculated in an approximate manner and the significance discussed from the viewpoint of the applicability of the B.E.T. multilayer theory.