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Errors in a modified database

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RenAmb:
Hello everyone,

It is my first utilisation of PHREEQC and I am currently working on silica dissolution in strong alkaline conditions. I added the followed equilibriums to model the high solubility of silica in those conditions as the monomeric equilibirums (already in llnl database) are not enough to explain silica solubility. When I ask the software to put my new modified database as the default database, I obtain errors messages as follow :

ERROR: Elements in species have not been tabulated, O.
Error: Reaction for species has not been defined,O.
Error Calculations terminating due to input errors.

So what I understand is that in SOLUTION_MASTER_SPECIES I should specify that O can be in the forms of the products I added and not only the basic ones already in :
O        H2O            0.0     O               15.994
O(-2)    H2O            0.0     0.0
O(0)     O2             0.0     O
O_phthalate O_phthalate-2 0 1 1)

As an example, here is one of the equilibirum added :
2H4SiO4 = Si2O2(OH)5- + H+ + H2O
   -log_k   -8.5

So should I add in SOLUTION_MASTER_SPECIES : O   Si2O2(OH)5- ?? If yes what should I put for the other columns alk   gfw_formula   element_gfw ?

Thanks to anyone helping me here.

dlparkhurst:
The master species for Si in llnl.dat is SiO2, so if that is the database that you are using, you should write reactions with SiO2 (or other aqueous species defined from SiO2, like H2SiO4-2). H4SiO4 is not defined in llnl.dat because it is equivalent to SiO2 with waters (SiO2 + 2H2O = H4SiO4).

I suggest that you do not modify llnl.dat, but rather add the necessary SOLUTION_SPECIES in your input file, or put the definitions in another file that can be added by using INCLUDE$.

To add Si aqueous species, I do not think you need to make any changes to SOLUTION_MASTER_SPECIES.

Put your added definitions in an input file, post them, and I will be able to tell you the problem.

dlparkhurst:
This will work with llnl.dat:


--- Code: ---SOLUTION_SPECIES
#2H4SiO4 = Si2O2(OH)5- + H+ + H2O
2SiO2 + 3H2O = Si2O2(OH)5- + H+
   -log_k   -8.5
END
SOLUTION
pH 14
Na 3 charge
Si 1
END

--- End code ---

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