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