Spana  SPANA

SPANA: Modify a Chemical System

A chemical system may be modified by selecting either one of the pull-down menus: “File / Data File / Modify” and “Run / Modify Chemical System”. A new window appears with the following functions:


 

Delete

 

Delete either a single reaction or a component, with all reactions where it participates. For example, removing the component Cu2+ will also take away CuOH+, etc.


Exchange

 

Exchange a component with a reaction. For example: Fe2+ for Fe3+; CO2(g) for CO32−; etc. This is useful when the equilibrium constants are based on CO32− as a component but a diagram for a given CO2(g) partial pressure is needed (example). May also be used to create diagrams for solutions saturated with a solid (example with Al).


Merge

 

Merge with another data file (Only in ad­vanced program level). For example: merge a file with the components H+, e−, Fe2+ and a file with Cr3+, e−, H+, to create a file with the system: H+, e−, Fe2+, Cr3+. Note that afterwards you will need to add manually any species formed by both Fe and Cr, for example FeCr2O4(s).


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The reaction and the equilibrium constant are shown in a status bar when you point with the mouse to a species name in the lists:

Mod_Chem_Syst

By double-clicking on a reaction product a new window appears where you can easily deactivate it and/or change the equilibrium constant:

logK_Ch.gif, 13kB

With this window you can make changes quickly without the need of a text editor and without learning the format of the input data file. Components can not be deactivated with SPANA; you must use a text editor to add a “*” at the start of their names. However, it is always possible to first deactivate a species and then exange to a component.

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