The equilibrium solubility of o-tolidine in supercritical carbon dioxide with or without cosolvents was measured using a dynamic flow method. The experimental data were taken at 308, 318 and 328 K. and over the pressure range from (11.0 to 21.0) MPa. Ethanol and ethylene glycol were chosen as the cosolvent, and the mole fraction of cosolvent was 0.01,0.02, and 0.04, respectively. The experimental data indicated that the solubility of o-tolidine can be enhanced by the presence of both the cosolvents, and increases with an increase in the mole fraction of cosolvents. The thermodynamic properties (total enthalpy Delta H-tot, sub-limation enthalpy Delta H-sub and solvation enthalpy Delta H-sol) of solid solute were obtained. The experimental data were correlated by Chrastil, Bartle, Mendez-Santiago and Teja, K-J, modified K-J, modified Chrastil and modified Sovova models. All the correlations showed satisfactory agreement with the experimental data. (C) 2011 Elsevier B.V. All rights reserved.