Mixing solutions and charge

[Charlie]

Q:
I have a series (300 to be precise) of mixing reactions which use the solution from the prior step and mix it with some solutions from a solution spread.  The issue I have is that the percentage error gradually grows and grows and eventually the solver stops.  Can I ‘charge’ an element in the mixed solution(s) which is then carried forward into the subsequent mix reaction? 

A: (from D. Parkhurst)
The charge balance error should be proportional to the solutions that are mixed. If the volume of solution grows, then the absolute equivalents error might grow, but the percent error should be bounded by the mixing proportions. Seems to me, the percent error should be no worse than the worst percent error in the mix.

If you are using SURFACE without a diffuse double layer in a reaction, then the solution error could grow because charge can be transferred to the surface and the solution has an equal and opposite charge added.