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Did Not Converge Error - Charge Balance

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I am struggling to understand my results from Spec8. I have 10 samples and am trying to get charge balances and Saturation Indices.


All the chemistry is quite similar between samples, however I only get results from 3 out of 10 of the samples. For the rest I get


N-R didn't converge after 999 its., maximum residual = 0.451, Xi = 0.0000
I attached my spread sheet below in hopes that someone smarter than me could figure out where I am going wrong!!
Thanks so much!!
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Hello Shona,


Thank you for sharing your spreadsheet. It’s hard to tell what’s wrong. I noticed that you’ve described your samples with a mix of basis entries (these are constraints on the calculation) and user-defined analytes like P, Si, and Sb (these have no effect on the calculation). As a result, the program has an incomplete understanding of the systems’ true chemistry. Perhaps this is the source of the error you’re encountering. I recommend completely describing your fluid in terms of basis entries and double-checking that all of your values and chemical units are correct.


You can specify the masses of basis entries like HPO4—and SiO2(aq) in terms of their elemental equivalents (i.e. HPO4-- as P and SiO2(aq) as Si) so you don’t have to do any extra work to get the spreadsheet in a form compatible with your water analyses from the lab. As for the Sb, GWB’s default thermo dataset, thermo.tdat, doesn’t include that element so you won’t find it in the list of basis entries in GSS. Other datasets included with the software, like thermo.com.V8.R6+.tdat, do. You can try loading that thermo dataset instead, or you can easily modify an existing dataset, either by copying entries from one thermo dataset to another or simply adding information directly from the literature.


For more information on thermo datasets, see the TEdit section in the GWB Essentials Guide. You can also view tutorials on how to edit thermo datasets here. Once you pick a suitable dataset, you can load it into GSS by going to File -> Open -> Thermo Data… and browsing for the file.


Kind regards,



Aqueous Solutions LLC

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