The principal investigator will attempt to determine equations of state and other properties of fluids in four chemical systems of geologic interest. Measurements will be made up to temperatures of 1100C and 25 kbar and will thereby extend P-V-T-X data for these systems to high-pressure/temperature conditions that are of considerable geologic interest. The data also will be used to more accurately pinpoint the phase equilibrium boundaries of several important mineralogical reactions.