Phase diagrams for quaternary salt solutions
Phase diagrams for two quaternary salt solutions are shown in the tabs below. This type of phase diagrams are for example useful when designing fractional crystallization processes.
- The sodium chloride, potassium chloride, calcium chloride – water system. This is a system with three cations and one anion which can be plotted in a triangular Jänecke diagram.
- The sodium chloride, potassium chloride, sodium sulfate, potassium sulfate – water system has two cations and two anions and is therefore plotted in a quadratic Jänecke diagram
The sodium chloride – potassium chloride – calcium chloride – water system
In the quaternary (Na+,K+, Ca2+) – Cl–-H2O system at 50°C, the following solid phases appear:
- NaCl (halite)
- KCl (sylvite)
- CaCl2·2H2O (sinjarite)
- KCl·CaCl2 (chlorocalcite, baeumlerite)
In the triangular diagram shown in the figure to the right, compositions are shown on a dry basis. At any point in the diagram, the mass percents of the three salts NaCl, KCl, and CaCl2 add up to 100%. A saturated solution contains the amount of water given in mass percent in the diagram and an amount of salt with a composition corresponding to the location in the diagram.
The experimental points and the calculated phase diagram lines represent compositions at which two solid phases are in equilibrium with the same saturated liquid. Each field in the diagram represents solution compositions that can only be in equilibrium with a single solid phase. The two fields representing CaCl2·2H2O and KCl·CaCl2 are very small. This is indicative of a high solubility relative to the other salts in the diagram.