41.     ANDERSON, R. B., AND HALL, W. K.  Modifications of the Brunauer, Emmett and Teller Equation.  II. Jour. Am. Chem. Soc., vol. 70, 1948, pp. 1727-1734; Chem. Abs., vol. 42, 1948, p. 6198.

                Modified Brunauer, Emmett, and Teller equation similar to that previously suggested has been derived and applied to physical-adsorption isotherms of types I and IV.  With type I isotherms, this reaction can be satisfactorily applied if the free energy of adsorption in the second and subsequent layers is taken to be equal to the heat of liquefaction.  For isotherms of type IV, which flatten below relative pressures of 0.85, the equation satisfactorily fits the data, if the free energy of adsorption was taken as less than that of liquefaction.  For this kind of type IV isotherm, the equation was used to integrate the equation of Kistler, and the resulting expression gave surface areas of the same order of magnitude as the Brunauer, Emmett, and Teller areas.  The equation is believed to be a simple method of characterizing isotherms with 4 constants.