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Error: Ionic Strength out of Range


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I'm attempting to calculate speciation in a complex brine system and continually receive the ion strength out of range error. The error seems to be focused around the interactions of EDTA4- with Ca2+ and Mg2+. Oxalate also seems to have this same issue.

If I swap the EDTA concentration for the species we expect to dominate, CaEDTA2-, this just moves the error to another species in the calculation. The model seems to give accurate data when EDTA and Oxalate are removed from the calculations.

error.png

inputs.png

 

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Hello,

Taking a quick look at your basis input, it seems like your solution is extremely concentrated (> 200 moles of solute per kilogram of solution). Can you double check that the unit that you are using for your concentration measurements are correct? 

Best regards,
Jia Wang

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Hello,

Thanks for double checking the units. I did a quick test with the new units and swapped CaEDTA-- (more abundant species) for EDTA----, and the speciation calculation was successful. Did you alter any other parameters in file setup? Perhaps a unit was left unchanged for one of the basis species? If you would like someone to take a closer look, please attach the SpecE8 or React input file so we can troubleshoot. 

Hope this helps,
Jia

 

 

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