Determination of surface area of soil by adsorption methods

How significant are estimates of surface areas of soils obtained by adsorption methods? To answer this we tested the applicability of an equation that relates monolayer coverage (N) of an adsorbent with the area (A) of adsorbate, NA(z)=k, for six soil samples using six adsorbates of different sizes. The data obtained confirm the validity of the equation with the z parameter ranging between 1.25 and 1.41. Hence each soil sample showed preferences towards small-sized adsorbates for which the product NA (calculated surface area) is inversely related to the size of adsorbate. We also demonstrated that the equation has roots in the Langmuir adsorption equation.