Phase diagrams for binary salt solutions
Phase diagrams for several binary salt solutions are shown below. Click on the tabs to see solubility diagrams for:
- Sodium chloride – water
- Calcium chloride – water
- Magnesium nitrate – water
- Magnesium sulfate – water
- Tri-sodium phosphate – water
- Di-sodium phosphate – water
- Mono-sodium phosphate – water
The sodium chloride – water system
In the sodium chloride – water system, one eutectic point and one peritectic point is found. These points are shown in the phase diagram to the right.
The eutectic point is at -21°C.
The peritectic point is at 0.1°C.
The eutectic point is the cryohydratic point, where ice and NaCl·2H2O (hydrohalite) both are in equilibrium with the same saturated solution. This point is at the lowest temperature where a liquid sodium chloride solution can exist.
The peritectic point at 0.1 °C marks the transition between hydrohalite and anhydrous sodium chloride as the stable solid phase in equilibrium with a saturated sodium chloride solution. If heated, solid hydrohalite will at this temperature be transformed into anhydrous sodium chloride (NaCl) and a saturated solution of sodium chloride.