H2O-KCl equilibrium phase diagram. Phases at equilibrium for the system H2O-KCl are shown as a function of chemical composition (weight percent KCl) 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 (108.6°C, 36.8 wt.% KCl), which is gives the highest temperature and highest salinity at which an H2O-KCl brine can exist at equilibrium at one atmosphere pressure. Data sources for this diagram can be found in Brady (2009).
Wt.% KCl:
Temperature:
Wt.% Brine:
Wt.% Ice:
Wt.% Sylvite:
