DE VAULT1 has directed attention to the possibility of obtaining the adsorption isotherm of single solutes from chromatographic results of the 'diffuse' boundary, suggesting a differential equation for evaluating the measurements. A more useful equation can be obtained by integration of the equation ν/x–α=d1/dc. . . . (1) where α and q are the pore space and the amount adsorbed per gram of adsorbent. After developing with a given amount of pure solvent ν, the amount of solute µ remaining in the column between the tail end of the chromatogram and the point x where the concentration c exists is