1. Langmuir and Villars2 calculated the heat of adsorption of oxygen on a smooth tungsten surface from the rate of loss of this gas from the adsorbed film, this rate of loss being determined experimentally by the change in electron emission of the tungsten filament sensitized by the presence of minute traces of cesium vapor.
2. Taylor and Sickman3 have derived an expression which enables them to calculate, from their rate measurements of the slow adsorption of hydrogen on zinc oxide, the value V 0, which is the quantity of gas adsorbed at equilibrium. Substituting this value into the exponential relationship, derived by them, between V 0 and A, the heat of adsorption, the value of the latter was obtained.
3. To account for the reversal, with temperature, in the sign of the temperature coefficient of the catalytic hydrogenation of ethylene on active nickel, zur Strassen4 and also Schwab5 have developed the following equation in which E is the activation energy of the hydrogenation reaction and λH2 and λC2H4 are the heats of adsorption of hydrogen and ethylene. It is assumed that the factor λC2H4 becomes effective only above the maximum in the temperature vs. reaction velocity curve. If this view is correct, λC2H4 is obtainable from the difference in the slopes of the ascending and descending branches of the curve obtained by plotting log k against 1/T. Schwab found, for λC2H4, 16 kcal. which seems a reasonable value.
4. Rideal6 calculated the heat of adsorption of hydrogen on active nickel making use of his experimental data on the rate of hydrogenation of oxygen on the nickel surface. This calculation is of interest because Rideal’s heat value was among the first to be obtained on an active catalytic surface and was soon to be confirmed by the direct measurements of Foresti7 and of Beebe and Taylor8.
5. Schwab, Zorn: Z. physik. Chem., Abt. B 32 (1936), 169.