Adsorption studies of a homogeneous series of dlcarboxyllc acids were performed at 5 and 40 °C, with oxalic, malonic, and succinic acids being adsorbed from dilute aqueous solutions onto activated carbon. Experimental data were compared with the calculated equilibrium uptakes as predicted by three different models: Freundllch Isotherm, Langmuir Isotherm, and the potential theory. A single generalized characteristic curve for these dlcarboxyllc acids was obtained In accordance with the potential theory. The average errors between the values calculated by the potential theory and the experimental data ranged from 1.80% to 5.44%. In this study the potential theory provided a better fit to the experimental data than did either the Freundllch or Langmuir Isotherm equations.