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react-decreasing water mass


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so far, I´m not too experienced with GWB but I do think it is a very capable program

(I use version 8). Recently, I did some calculations about minerals precipitating

in chlorine solutions. In these calculations, the water mass decreases during the

simulations while the minerals incoporate water in their structures (I guess it`s

due to that).


Is there any possibility to keep the water mass constant anyways during simulation?


Thanks a lot for your help,



I attach a script and the thermo_hmw database (though I made no changes on it).



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Is there any possibility to keep the water mass constant anyways during simulation?


Hi Christiane:


In your simulation, water mass decreases for two reasons:


1. precipitation of Gypsum

2. generation of acidity (your pH decreases from 12 to -4)


There is no direct way to fix water mass in GWB- you could titrate H2O back in via the Reactants panel as it is being lost, but since H2O loss is not linear in your system, this would have to be done in two model steps, which is not very ideal.


The other way to tackle this issue is to ask whether the water mass decrease predicted by GWB is actually what you observe/expect in your system. You could prevent Gypsum precipitation by removing the mineral from consideration (Config- Suppress option), and you can also hold pH constant (use the Fixed pH option in the Reactants tab).


I hope that helps,


Tom Meuzelaar

RockWare, Inc.

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