The SFT Phase Monitor II is a powerful analytical tool for determining the solubility of various compounds and mixtures of compounds in subcritical and supercritical fluids. It provides direct, visual observation of materials under conditions which may be controlled precisely by the researcher. Experiments may be performed in liquid or supercritical carbon dioxide or in other compressed gases. Additionally, the effect of co-solvents on the solubility of compounds of interest in supercritical carbon dioxide can be investigated with this instrument. It allows the end user to view the dissolution, precipitation and crystallization of compounds over a wide range of pressures and temperatures. Experiments can be done from a few hundred psi to 10,000 psi and from ambient temperature to 150º centigrade.