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. The blue area indicates temperatures and compositions for which a single phase, brine, is present at equilibrium. Areas that have the horizontal line pattern indicate temperatures and compositions for which two phases are in equilibrium. The brine region is bounded on the right by a sylvite-saturation curve and on the lower left by an ice-saturation curve. Lowering of the temperature (by cooling) or changes in chemistry (by dissolving sylvite or ice in the brine) or can cause brines to become saturated with sylvite or ice. Where the two saturation curves meet is a special point, a composition and temperature where brine is saturated both with sylvite and with ice. This special point, a eutectic, gives the composition (19.87 weight percent KCl) of the first liquid that would appear upon heating a cold mixture of ice and sylvite above -10.8°C. Below -10.8°C, ice and sylvite are in equilibrium and brine is not stable. 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.% KCl:
Temperature:
Wt.% Brine:
Wt.% Ice:
Wt.% Sylvite:
