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. Hydrohalite (NaCl.2H2O) is shown in this diagram. At equilibrium, brines below 0.1°C can be saturated with hydrohalite, but not with halite. The halite and hydrohalite saturation curves meet at 0.1°C and 21.6 wt.% NaCl. This special point is called a peritectic. Hydrohalite melts incongruently to a mixture of halite and brine at 0.1°C. Click on the "Show Phases" button and mouse over the diagram to see the equilibrium proportions of phases at each composition and temperature. Data sources for this diagram can be found in Brady (2009).
Wt.% NaCl:
Temperature:
Wt.% Brine:
Wt.% Ice:
Wt.% Halite:
Wt.% HHal:
