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As a new user of GWB package I am going through all training materials on the GWB ONLINE ACADEMY and now I have an issue of making the graph Change in Concentration(mmol/kg) versus Temperature (C). From what I made, the CO2aq and HCl curves overlap but I am surprised to see how both curves don't overlap in your case. What did you do so that curves cannot be overlap?

Thank you




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Thank you so much for the reply Dr Farrel. I was able to pinpoint where the issue was. But my other main question concerns the species highlighted((H+, CO2aq and HCl). I am wondering why the H+ concentration variation depends only (or mainly?) on HCl and CO2 dissociation as they are many other species that might contribute to the decrease in pH.

My second concern relates the Reaction Kinetics part. Can you elaborate more how to plot together the undersaturated and supersaturated curves in the same graph using MS PowerPoint(see attached graph)? 


Thanks again for your enlightenment!



Reaction Kinetics.PNG

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You can start with a delta plot showing all the species in the fluid, then one-by-one hide the species with the largest concentration changes that aren’t due to H+ transfer. For example, the concentration of CaCl+ decreases more than anything else, and the free Ca++ and Cl- ions increase almost stoichiometrically. It's clear there's no H+ transfer involved, so right-click on the curve corresponding to each species and select "Hide this variable". After a few more similar steps, you’ll see that the species we’ve highlighted have the largest change in concentration and thus best explain the pH change in our chemical model.

I’m glad to hear you figured out how to overlay the plots outside our software. For anyone else reading, there are a couple different options for using MS Office products to superimpose results from separate calculations together. One method is to export the numerical values from your plots into Excel (Edit > Copy As > Spreadsheet), then plot them together there. A second method is to copy each plot as an enhanced metafile (Edit > Copy As > Enhanced Metafile) into its own slide in PowerPoint. You should make sure that the axis range spans the entire data range of interest (in your case, from 0-12 mg/kg), so that the two plots fit together correctly. Next, ungroup each image, then copy one of the curves and paste it into the other slide. For more information, please see the “How do I retrieve numerical data from my plots?” and “How do I overlay my diagrams?” slideshows in the Using GWB section of https://www.gwb.com/tutorials.php.


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