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Eh-pH diagram


Bob K
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Alright, I am a new user and wish to create an Eh-Ph diagram for cadmium with acetate, phosphate, and bicarbonate species present. So, first, how do I access the correct database (is there a dropdown menu for databases?) and then how do I add multiple species?

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Hi Bob,

 

You can go to File - Open - Thermo Data... to load different thermo datasets. You might choose thermo.com.v8.R6+.dat for this example, since the default dataset thermo.dat does not contain data for Cd++.

 

From the Basis pane of Act2, you set the main species to diagram, then choose the axes, then finally add any complexing species with the "add" button under the "in the presence of" section. You'll probably want to account for the speciation of complexing species in your diagram. Please refer to section 5.3 (Mosaic diagrams) in the GWB Essentials Modeling Guide for details. To account for both acetate and bicarbonate, you might try decoupling all redox pairs involving carbon (type decouple Carbon into the command pane) then separately adding HCO3- and Acetic acid to the Basis and choosing the "speciate over x" option to create a mosaic diagram. Alternatively, you can decoupling all but the HCO3-/Acetic acid pair, add HCO3-, then choose "speciate over x-y".

 

The GWB Essentials Modeling Guide can be accessed from the help menu of any GWB app. You might also take a look at this

for creating specialty plots and diagrams.

 

Hope this helps,

 

Brian Farrell

Aqueous Solutions LLC

 

P.S. I moved your post from the archive of old posts and made a new topic on the main GWB forum page so that it's more easily visible.

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