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.