The adsorption from binary mixtures of acetic, propionic and butyric acids has been studied systematically, by using sugar charcoal as adsorbent.In all these systems, the adsorption of any one acid is less than when it is present alone, but the well-known Langmuir type equation does not well represent the experimental data.Plotting of the corresponding (x/m) values gives straight lines with negative slopes which vary with the concentration of the acid displaced.The negative slopes of these straight lines are all less than unity, even though the adsorption of displaced acid is saturated.These facts agree with Ting and Fu's assumption, that the decrease of adsorption of individual acids is due to the displacement of the solvent, with subsequent shift of equilibrium, and not due to simple displacement.