1255.    GREGG, S. J., AND JACOBS, J.  Examination of the Adsorption Theory of Brunauer, Emmett, and Teller, and Brunauer, Deming, Deming, and Teller.  Trans. Faraday Soc., vol. 44, 1948, pp. 574-588; Chem. Abs., vol. 43, 1949, p. 2065.

       Brunauer-Emmett-Teller and Brunauer-Deming-Deming-Teller theories have been examined, and the following points are discussed:  The heat of adsorption E₁ calculated via the parameter c of the theory, is shown to be compatible with thermo-dynamic requirements as expressed in the Clausius-Clapeyron equation, but the latter are equally compatible with a value E₁+RT in C, where C=any constant.  E₁ shows a moderate qualitative correspondence with the calorimetric or isoteric value, but close quantitative agreement is lacking.  The relationship, which the theory implies between I_L and I_X, the integration constants of the vapor equation and the adsorption isostere, respectively, is not found to hold in practice.  Arguments are adduced against the assumption made by the theory that the evaporation-condensation conditions of the adsorbed multilayer differ inappreciably from those of the bulk liquid.  The implicit assumption that the adsorption isotherms above and below the critical temperature of the adsorbate are markedly different is shown to be improbable.  The values of the monolayer capacity derived from the theory and from the “phase-change” method of Gregg and Maggs are compared; only for isotherms of types I and II of the BDDT classification is agreement to be found.  According to the phase-change method, the adsorption isotherm cannot invariably be represented by a single equation as assumed by the BET-BDDT theory; where phase changes occur, the isotherm is split up into separate parts each following its own equation.  The BET-BDDT theory does not account for hysteresis, but the phase-change conception includes it as a natural consequence.