The phase behavior and critical points of carbon dioxide + octane are determined from 313 to 393 K, and their molar volumes and densities are measured both in the subcritical and supercritical (SC) regions using a variable-volume autoclave in this study. The critical curve of carbon dioxide + octane has been predicted with an equation of state (EOS) by Heilig and Franck, in which a repulsion term and a square-well potential attraction term for intermolecular interaction has been used. To use the pairwise combination rule for the square-well molecular interaction potential, three adjustable parameters are required. The thermodynamic properties including mole fractions, densities and molar volumes of this system are also calculated using the Heilig-Franck, the Peng-Robison (PR) and the Peng-Robinson-Stryjek-Vera (PRSV) equation of state. Among the equations of state, the Heilig-Franck equation of state has been found to have the best correlation with binary vapor-liquid equilibrium data of the carbon dioxide + octane system. (c) 2006 Elsevier B.V. All rights reserved.