H2O-NaCl equilibrium phase diagram. Phases at equilibrium for the system H2O-NaCl are shown as a function of chemical composition (weight percent NaCl) and temperature at one atmosphere pressure. The diagram includes temperatures where steam is stable. The blue area indicates temperatures and compositions for which a single phase, brine, is present at equilibrium. Just as the freezing temperature of a brine depends on its salinity, the boiling temperature of the brine depends on its salinity. There is a saturation curve for brine in the presence of steam at equilibrium. The steam saturation curve and the halite saturation curve meet at a chaotectic point (108.7°C, 28.40 wt.% KCl), which is the highest temperature and highest salinity at which an H2O-NaCl brine can exist at equilibrium at one atmosphere pressure. Data sources for this diagram can be found in Brady (2009).
Wt.% NaCl:
Temperature:
Wt.% Brine:
Wt.% Ice:
Wt.% Halite:
Wt.% HHal:
