Conceptual Models > Database selection and modification

Primary species in databases


Hello dear PhreeqC users,

I work with several databases and thought until now that only primary species could be reactant in reactions.
It was until I work with the JAEA (Japan Atomic Energy Agency) data base which uses secondary species as reactant, e.g.:
Cit-3 + H+ = HCit-2
Ca+2 + HCit-2 = CaHCit
In most of database it would have been an error for the last reaction due to the use of the secondary species CaHCit.

Or maybe am I wrong and databases can use seconday species ? Does someone has any clues on that?

Thank you,

Yes, any database can contain reactions with non-master aqueous species in SOLUTION_SPECIES, PHASES, EXCHANGE_SPECIES, etc. As long as a given species on the left-hand-side of a reaction is defined by another reaction with the given species on the right-hand-side, you should be okay (A->B, B->C, C->D). The order that the reactions are defined should not matter. PHREEQC sequentially rewrites reactions to replace non-master species; the process must eventually lead to a reaction that contains only master species. If the process fails, possibly by a circular set of definitions (A->B, B->A), you will get an error message.

One further rule is that each redox state has one secondary master species. A secondary master species must be the only species of the redox state that has electrons, H2, or O2 in its reaction.

Okay thanks a lot for these precisions,


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