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Warning: Reactants are charge imbalanced

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I have been trying to run the attached react and thermo data in flush mode. But I receive the following warning:


-- Warning: Reactants are charge imbalanced by 172.8

Residuals too large, 709-th interation

Largest residual(s):

Resid Resid/Totmol Cbasis


Cl- 0.03095 1.714e+200 3.374e-214



It seems that other forum questions have had similar issues, but I was unable to resolve the issue with the advice provided in those posts. Any assistance on how to balance the system so that it converges to a solution would be appreciated.


Thanks in Advance,




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Hi Howard,


That warning message is certainly something you'll want to look into, but the charge imbalance on the reactants pane is actually not your main issue. Your initial system (which you've defined on the Basis pane) fails to converge before the Reactants pane is even considered. Try using SpecE8 to equilibrate your initial system before making a more complicated reaction path model.


You should ask yourself whether all of those minerals are really in equilibrium with your system. As a simple test, I used Rxn to write the following reaction:


Mg4Al2O7^10H2O + 8 H+ + 2 Quartz = 12 H2O + 4 Mg++ + Kaolinite


I then set pH to 5.4, T to 25, and activity of H2O to 1. The resulting equilibrium equation states that the activity of the Mg++ ion in this assemblage should be 10^3.7888 - quite a large value. This leads me to believe there is something wrong with the way you defined your system. For example, a higher pH would result in a more reasonable Mg++ activity. Perhaps you should check whether the thermo data is correct. Another item to consider is whether it makes sense to have so much oxygen in a system that is in equilibrium with Pyrrhotite.


Hope this helps,


Brian Farrell

Aqueous Solutions LLC

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