dissolution of carnallite in water

[sadegh66]

Hi all
I want dissolve carrnallite(KCl.MgCl2.6H2O),which have low value NaCl, in water.Crystals KCl forms and MgCl2 is dissolved, when carnallite dissolve in water. but I don know what is the exact dissolution temperature of the carnallite in water. How can use PHREEQC to estimate the dissolution temperature of Carnallite in Water with a specific component?
Thank...

[dlparkhurst]

To find carnallite solubility as a function of temperature you can run the following script with the pitzer.dat database.

SOLUTION
EQUILIBRIUM_PHASES
Carnallite
REACTION_TEMPERATURE
0 100 in 11 steps
END

If you assume the NaCl does not affect the solubility, you can simply define a phase in PHASES that has the composition that you want and simply keep the analytical expression from Carnallite.

If you want the NaCl to affect the solubility of carnallite, you need some more thermodynamic data. Either an equilibrium constant appropriate to the composition or perhaps you want to treat the carnallite as a solid solution with another NaCl-bearing phase.

[sadegh66]

Thank you...
Generally, after dissolution of carnallite in water, NaCl is crystallized with KCl but MgCl2 is dissolve in water. any way NaCl will afect on solubillity carnallite. It is important that MgCl2 will dissolve in water totally for me, because i want use from precipitation methods to deposits Mg(II) ions.
good luck....