Conceptual Models > Database selection and modification

Elements and reactions in/for SiO2 not tabulated/defined

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kennedyantwi1:
Dear Dr. Parkhurst,
I'm attempting to model the effect of H2 storage on the porosity of the storage reservoir. I've included SiO2 in my phases block as follows: 

Quartz
SiO2 + 2 H2O = H4SiO4
- log_k  -3.98
-delta_h  5.990 kcal
-analytic   0.41   0.0   -1309.0
-Vm 22.67
END

I keep getting the errors:
ERROR: Elements in species have not been tabulated, SiO2
ERROR: Reaction for species has not been defined, SiO2

Your guidance at this juncture would be appriciated.

dlparkhurst:
It depends on the database that you are using.

If SiO2 is the SOLUTION_MASTER_SPECIES for Si, as in llnl.dat, then here is reaction that you need:


--- Code: ---PHASES
Quartz
        SiO2 = SiO2
...

--- End code ---

For phreeqc.dat and most other databases, H4SiO4 is the master species and the definition should be as follows:


--- Code: ---PHASES
Quartz
SiO2 + 2 H2O = H4SiO4
...
END

--- End code ---

I think you might have put the definition in the SOLUTION_SPECIES data block.

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