Partial molar volumes of 11 n-alkanes (C21H44, C22H46, C23H48, C24H50, C25H52, C27H56, C28H58, C31H64, C34H70, C36H74, and C40H82) at infinite dilution in CO2, obtained by supercritical fluid chromatography at T = 310.5 K to T = 431.6 K and p = 8.7 MPa to p = 39.1 MPa, have been used to estimate the (carbon dioxide-alkane) interaction second virial coefficients B-12. The isothermal, high-pressure data are fitted by the Peng-Robinson equation of state with the van der Waals one-fluid mixing rules, and the optimised unlike-interaction parameters of the equation are used to calculate B-12. The error sources, inherent in this model-dependent procedure, are discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.