how to add NaOH as a solution species

["Shane Matolyak" <smatolyak@xxxxxxxxxxx>]

Good day David,

I'm trying to use PHREEQCi to model the effect of adding lye to a
sedimentation pond.  My approach is to specify the pond as "Solution 1" and
the lye as "Solution 2" and then use the "Mix" command to mix these
solutions in various ratios to see the resulting pH change and precipitates.

The lye consists of a 50 wt% NaOH solution (19.125 molar, pH = 15.6).

Since lye / NaOH is not listed in the "Individual element input" window of
the "Solution" menu I attempted to add it using the "Solution Species" and
"Solution Master Species" menus.  However, I end up with convergence errors
for lye and the activity of water, not to mention a terrible charge
imbalance for Solution 2.

I've attached my input file.  If you have time, could you please take a look
and let me know what I'm doing wrong and suggest some ways to overcome my
problems?

Thanks!

Shane Matolyak
Maxim Technologies, Inc.
Bozeman, MT(406) 582-8780

Attachment: input.doc
Description: MS-Word document