PHASE BEHAVIOR AND IN-SITU DENSITY DETERMINATION IN CONCENTRATED SALT SOLUTIONS UNDER HYDROTHERMAL CONDITIONS

An optical cell was constructed to observe phase behavior in aqueous electrolyte solutions at temperatures up to 450{degrees}C and pressures up to 1200 bar. The goal was to map out the single-phase region for a certain concentrated, multicomponent waste solution, to aid in the design of a treatment facility. The imaging system could also measure the refractive index of the fluid, allowing the density to be determined by means of the Lorentz-Lorenz relationship. The validity of the technique was verified for pure water and for NaCl-water systems. Data for a multicomponent system is present as a family plot of density vs. pressure, for several different temperatures, with the lowest pressure on each plot corresponding to a phase boundary. Data is also presented for the binary system NaNO{sub 3}-water.