The Bureau of Mines is testing supercritical fluids as solvents to selectively extract valuable components from complex matrices. Materials recovered during supercritical fluid extraction are often highly purified. Using laboratory apparatus designed specifically for supercritical fluid research, Bureau researchers have measured the solubility of titanium tetrachloride (ticl4) in supercritical, liquid, and gaseous carbon dioxide (co2). Co2, a commonly used supercritical fluid, is inert, inexpensive, and nontoxic. Supercritical co2 formed a single phase with ticl4 at 45 deg. C and 1,500 psig. When the solution was heated at constant pressure beyond 55 deg. C, ticl4 precipitated from the fluid. Results showed that ticl4 solubility in supercritical co2 is not controlled by the vapor pressure of the solute.