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[OLD] Temperature dependence in Tact


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From: Antoine de Haller

Subject: temperature dependence in Tact

I have problems with the Tact program in speciating SO4-- on mozaic diagrams when plotting Fe++ vs fO2(g) at fixed pH or vs pH at fixed fO2(g). The program does not take into account Temperature dependent species changes and therefore plots wrong diagrams.

From: Craig Bethke

Subject: Re: temperature dependence in Tact

It turns out that the program is working correctly, if not according to your expectations. When you speciate a basis entry, the program considers all of the species that can be constructed from that entry, water, and the species on the axis (or axes) in question. For example, if you speciate SO4-- over pH, the program accounts in its speciation calculations for SO4-- and HSO4-, but not H2S, HS-, etc. You can manipulate the configuration by swapping the basis. If you swap HS- for SO4-- and then speciate it over a pH axis, for example, the program will consider the sulfide instead of sulfate species. Remember that in any Act2 or Tact calculation, you can view complete details of how the diagram was generated by inspecting the Act2_output.txt (or Tact_output.txt) file. Just click on Run - View. Finally, if you want to create diagrams for chemical systems more complicated that can be represented easily in an activity-activity or activity-temperature diagram, you can use React and Gtplot to create a speciation diagram.

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