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decoupling organic/HCO3 couples

Tom Meuzelaar

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[admin notice: the below is from the former GWB users group email distribution list. This message was originally posted 3/28/2006]


Posted by: Kirk Cantrell


Dear GWB User's Group:


I have a problem that I encounter while using the thermo database

thermo.com.v8.r6+.dat. I prefer to use this database because it appears

to be the most comprehensive and up to date. For example, thermo.dat

does not have any Pb hydrolysis constants. I am currently working on a

Pb solubility problem. The problem is that I have no interest in all the

organic/HCO3 couples which are automatically included in an Eh-pH plot

when HCO3 is a basis species. It would be simple enough to decouple all

carbon redox couples or even all redox couples in one step (if you don't

care about redox reactions). However, when I try to do this, it doesn't

seem to work properly. The program gets get rid of most of the

organic/HCO3 couples, but not all of them. Am I doing something wrong?


Any suggestions.


Kirk Cantrell


Posted by: Andy Scott




I looked at the script, and I noted that the Org/HCO3 redox couples were still coupled. I decoupled each one and hit the apply button. When I ran the plot routine I still got some Pb(pent) species, so I supressed these. I ran plot again, and got some Pb(prop) species, and supressed them. I ran the plot a final time and got an organic free plot. Hope this is what you needed. Script attached.



Clemson Univ.


Posted by: Craig Bethke


Hi Kirk, Andy,


Andy's method should work for you if you want to work from the GUI, or you can go to the command pane and enter the command


decouple Carbon


That should give you what you want without too much drama.


We suspect the root of your issue is that in the current release, the Redox Couples dialog can get a little funky when there are a lot of couples to keep track of. We've already replaced it with a new dialog that is more flexible and reliable; it will be included in the next maintenance release.


Hope this helps,


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