phase equilibrium data for co2 hydrate in presence of binary nacl-mgcl2 aqueous solutions were obtained at four different concentrations (2 wt%nacl-8 wt%mgcl2, 8 wt%nacl-2wt%mgcl2, 5 wt% nacl-15 wt%mgcl2, 15 wt% nacl-5 wt%mgcl2) in the temperature range of (258.63 to 276.45) k and in the pressure range of (1.34 to 3.41) mpa, respectively. the measurements were carried out by employing isochoric pressure search method with uncertainties of +/- 0.1 k for temperature and +/- 0.02 mpa for pressure. the hydrate equilibrium data for the (co2 + water) system were compared with some experimental data from the literature, and the acceptable agreement demonstrated the reliability of the experimental method used in this work. the van der waals and platteeuw (vdw-p) solid solution theory was used to model the hydrate phase, and the equation of weiss combined with pitzer-based model was applied to characterize the activity of water. the predicted results were in good consistency with the experimental data, and the average pressure deviation was 5.13%. (c) 2012 elsevier ltd. all rights reserved.