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React: error messages


Stefan
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By calculating simple salt systems sometimes error messages occur, that unfortunately are not self-explanatory (for me). Similar problems have been addressed within the user forum before but the answers do not apply for the systems shown in the examples below.

 

Example Script 1:

 

reset

data = thermo_hmw.dat

balance off

temperature = 25

1.0000 kg free H2O

K+ = 2e-8 molal

Mg++ = 1e-8 molal

SO4-- = 2e-8 molal

react 25 mol Schoenite

go

pickup entire

go

 

The first part works well. But picking up the entire system as base for further calculations leads to the following error message:

 

*N-R didn't converge after 999 its., maximum residual =

Largest residual(s):

Resid Resid/Totmol Cbasis

--------------------------------------------------------

SO4-- -51.16 0.1124 171

--------------------------------------------------------

 

By replacing “pickup entire†by “pickup fluid†it works well (but solids are lost as expected with this command). It seems that there is some conflict with minerals swapped into the basis. But if so, how to solve this?

 

A similar problem arises when using another script that should lead to approximately the same result.

 

Example Script 2:

 

reset

data = thermo_hmw.dat

balance off

temperature = 25

1.0000 kg free H2O

Mg++ = 1e-8 molal

SO4-- = 1e-8 molal

swap Schoenite for K+

25 free mol Schoenite

go

 

 

 

This results in the following message:

 

Ionic strength out of range.

Largest residual(s):

Resid Resid/Totmol Cbasis

--------------------------------------------------------

SO4-- -8.029e+009 1 9e-009

Mg++ -4.014e+009 1 9e-009

 

What puzzles me most is the message “Ionic strength out of rangeâ€. As one can see from the first part of the first script this system has an ionic strength of about 8. With other setups one may easily create systems with an ionic strength quite double that value.

 

Can anybody help me understanding this kind of error messages and tell me how to deal with them?

 

Regards,

Stefan

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Can anybody help me understanding this kind of error messages and tell me how to deal with them?

Regards,

Stefan

 

Hi Stefan:

 

In your first script, after the Pickup command, while you have a system that's essentially in equilibrium, it far from charge balanced. Both of your cation components are constrained by mineral masses, leaving you initially only with dissolved anion (SO4--). React needs to add significant cation component mass (K+ and Mg++) to achieve a solution that's in equilibrium with Arcanite and Schoenite. I think you'll find that your solution converges without trouble if you add charge balance to the SO4-- component.

 

Your second script defines a solution that's initially so far out of equilibrium with the Schoenite mineral mass in the Basis, that it causes numerical difficulty.

 

I hope that helps.

 

Regards,

 

Tom Meuzelaar

RockWare, Inc.

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Hi Tom

 

Thank you for your support. Your answers help me unterstanding these kinds of error mesages. Script 1 works fine with charge ballancing on SO4-- for the second part.

 

There seem to be some little secrets that one has to learn with time and/or by asking a more experienced user via the support forum. ;)

 

Regards,

Stefan

 

 

Hi Stefan:

 

In your first script, after the Pickup command, while you have a system that's essentially in equilibrium, it far from charge balanced. Both of your cation components are constrained by mineral masses, leaving you initially only with dissolved anion (SO4--). React needs to add significant cation component mass (K+ and Mg++) to achieve a solution that's in equilibrium with Arcanite and Schoenite. I think you'll find that your solution converges without trouble if you add charge balance to the SO4-- component.

 

Your second script defines a solution that's initially so far out of equilibrium with the Schoenite mineral mass in the Basis, that it causes numerical difficulty.

 

I hope that helps.

 

Regards,

 

Tom Meuzelaar

RockWare, Inc.

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Hi Tom

 

Thank you for your support. Your answers help me unterstanding these kinds of error mesages. Script 1 works fine with charge ballancing on SO4-- for the second part.

 

There seem to be some little secrets that one has to learn with time and/or by asking a more experienced user via the support forum. ;)

 

Regards,

Stefan

 

Glad to be of help,

 

Tom

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