In order to overcome the lack of experimental phase equilibrium data for a deeper understanding of particle formation processes using supercritical fluids, investigations have been carried out in two static equilibrium apparatuses. The first apparatus is designed as a view cell with an inner volume of 1310 cm(3) placed in an air-thermostatted chamber, which allows a visual determination of the SLG-line following the first melting point method. The second equilibrium cell of approximately half the inner volume is placed in a water thermostat, which is more efficient for solubility measurements. The SLG-lines of naphthalene with carbon dioxide, trifluoromethane, and a mixture of these two solvents were experimentally determined and additional solubility measurements have been performed. The experimental results are described by means of cubic equations of state, which give, from an engineering point of view, an adequate thermodynamic model for the representation of solubility and SLG-lines. (C) 2002 Elsevier Science B.V. All rights reserved.