A new apparatus for the measurement of solid solubilities in supercritical fluids is described indetail. It is based on an analytical open-flow method: the composition of the phase is obtainedby analyses, and the solvent flows continuously through the solid solute. Solubilities ofnaphthalene in supercritical CO2 in the pressure range of 8−30 MPa are reported for theisotherms 308.15 and 318.15 K. The solubility data are then correlated using three density-based models.