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Beginners => PHREEQC basics => Topic started by: PrestoConFuoco on July 04, 2018, 05:48:30 PM

Title: Finding a point of phase diagram with defined concentrations of some components
Post by: PrestoConFuoco on July 04, 2018, 05:48:30 PM
I have some experimental points of isothermal phase diagrams of systems salt(1)-salt(2)-H2O.  And for comparing calculated data with experimental one, for example, i need to get the point with concentration of one salt identical to experimental, and concentration of second salt i will just compare.
So, the problem is - how to calculate solubility of salt(1) while constant concentration of salt(2)?

At the moment i managed to do it only for cases with no double salts and no crystallohydrates, for example for system NaCl - KCl - H2O at 25 C, where equilibrium phases are halite (anhydrous NaCl) and sylvite (anh. KCl), as amount of water in solution doesn't change during precipitation of solids, and so the concentration of unsaturated component.
And if crystallohydrates are precipitated, water is going to solid phase and the concentration of unsaturated component is rising! :(
Thus,  i need to calculate more complicated phase diagrams of salt-salt-water systems, and also more complicated 4- and 5-component systems.

Big thanks! And sorry a lot for my poor english.
Input file and appropriate database for mentioned Na-K-Cl-H2O system are attached.