PHASE-EQUILIBRIA IN (WATER PLUS KRYPTON) AT PRESSURES FROM 31 MPA TO 273 MPA AND TEMPERATURES FROM 610-K TO 660-K AND IN (WATER PLUS NEON) FROM 45 MPA TO 255 MPA AND FROM 660-K TO 700-K

The equilibrium surface in (T, p, x) space (where T denotes temperatures, p pressure, and x mole fraction), has been determined experimentally for {xH2O + (1-x)Kr} and for {xH2O + (1-x)Ne}. Pressures and temperatures within the range 31 MPa to 273 MPa and 610 K to 660 K were obtained at seven values of x between 0.177 and 0.809 for the mixture containing krypton. Five values of x between 0.553 and 0.860 were used to obtain results from 45 MPa to 255 MPa and 660 K to 705 K for the neon mixture. The critical curve can be deduced from the (p, T) boundary curves commencing from the critical point of pure water (647 K and 22.1 MPa). The critical curve for {xH2O + (1-x)Kr} passes through a temperature minimum at 631 K and 55 MPa whereas the critical locus for {xH2O + (1-x)Ne} proceeds immediately to temperatures and pressures above the critical point of pure water. This is a rare example of “gas + gas) immiscibility” of the first kind. The experimental results are supplemented by calculations of the critical locus using a “hard-sphere + attractive term” equation of state based on a square-well potential for the fluid. The comparison between theory and experiment indicates good agreement. © 1993 Academic Press Ltd.