H2O-MgCl2 equilibrium phase diagram. Phases at equilibrium for the chemical system H2O-MgCl2 are shown as a function of chemical composition (weight percent MgCl2) and temperature at 1 atmosphere pressure. There are seven stoichimetric solid phases. On the diagram, two melt congruently, two melt incongruently, and the melting behaviors ot two are not shown. MgCl2 melts congruently at 712°C. Peritectic and eutectic compositions and temperatures are shown on the axes. There is a chaotectic point between steam and MgCl2.H2O at 192°C. Data sources for this diagram can be found in Brady (2009).