The binodal curves of the liquid-liquid equilibria (LLE) for systems of o-toluidine with heptane, octane, nonane, decane or dodecane have been determined visually. All the curves show an upper critical solution temperature (UCST), which increases with the chain length of the alkane. The bimodal curves have a rather flat horizontal top and their symmetry depends on the chain length of the alkane. For the studied systems, interaction parameters in the framework of the DISQUAC model are reported. DISQUAC represents the coordinates of the critical points in the correct range of temperature and composition. (c) 2007 Elsevier B.V. All rights reserved.