PhreeqcUsers Discussion Forum

Beginners => PHREEQC basics => Topic started by: Flopi on February 12, 2020, 02:43:38 PM

Title: Fix_Ca
Post by: Flopi on February 12, 2020, 02:43:38 PM
Dear forum,
I am trying to use Fix_Ca to control the activity of my solution of an mineral stability diagram. My issue is that since it adds Ca+2 without counter ions, it messes up with the pH and the pe by forcing water to react to create these counterions. I tried with CaCl2 instead of Ca+2 in Fix_Ca but then the Ca+2 activity is not well constrained anymore.

Any way to control precisely Ca+2 activity without messing up with electroneutrality ?
Title: Re: Fix_Ca
Post by: dlparkhurst on February 12, 2020, 04:14:45 PM
This script fixes the activity of the Ca+2 ion.

Code: [Select]
PHASES
Fix_Ca+2
Ca+2 = Ca+2
log_k 0
END
SOLUTION
EQUILIBRIUM_PHASES
Fix_Ca+2  -3 CaCl2 10
END
Title: Re: Fix_Ca
Post by: Flopi on February 12, 2020, 04:51:36 PM
Once again, you save my life :)
Thanks a lot for your rapidity and your efficiency !