Aqueous mixtures to supercritical temperatures and at high pressures

Thermophysical properties of dense supercriiicai water with special emphasis on dielectric permittivity are discussed. Phase diagrams and some critical curves of the binary systems H20—H2, H2O—N, H20—02, H20-CH4 and H20-He to 450 °C and 200 MPa are shown. H20-He tas a type I critical curve. A rational equation of state to calculate phase diagrams and critical curves for polar—non polar systems is described. Measurements with the ternary system H20—CH4—NaCl are presented. 2 mol per cent of added NaC1 shifts the phase separation H0—CH4 by 100 degrees to higher temperatures. The excess Gibbs energy fr homogeneous supercritical H20—N2-mixtures to 200 MPa is shown. The static permittivity of super— critical H20—benzene mixtures is presented as an example of dielectric behaviour of polar-non polar mixtures in general.