1. Enter your fluid composition on the Basis pane
SpecE8 figures concentrations of aqueous and sorbed species, mineral saturation, and gas fugacity
Enter your fluid composition on the Basis pane
Swap in gases of known fugacity, or minerals at equilibrium
Set dissolved concentrations in units of your choice
Set temperature
Click to add new entries

2. View results as a text file…
Species listed in order of molal concentration
Activity coefficients
Species activities

3. … or plot results in Gtplot
Set “Variable type”, then choose from the list of variables
Set X and Y axes

4. Calculate mineral saturation
Only consider minerals with silica
Oversaturated minerals
Undersaturated minerals

5. Plot a variety of water chemistry diagrams
thermo_hmw.tdat is the Harvie-Moller-Weare formalism of the Pitzer equations.

6. Disable redox coupling between As(V) and As(III), Fe(III) and Fe(II)
You can disable one or more redox coupling reactions, or assume redox equilibrium
Config →
Redox Couples…
Disable redox coupling between As(V) and As(III), Fe(III) and Fe(II)

7. Select Nernstian Eh values
Widely varying Eh values indicate system has not reached redox equilibrium
Select Nernstian Eh values

8. File → Open → Thermo Data…
Thermo datasets utilizing the Pitzer equations are designed for application at high ionic strength.
File → Open →
Thermo Data…
thermo_hmw.tdat is the Harvie-Moller-Weare formalism of the Pitzer equations.

9. File → Open → Sorbing Surfaces…
Account for sorption onto mineral surfaces using Kd, Freundlich, and Langmuir isotherms, ion exchange, or two-layer surface complexation
File → Open →
Sorbing Surfaces…
Surface complexation dataset for hydrous ferric oxide.
You can add any number of sorbing surfaces.

10. Select “Sorbed fractions” for the “Variable type”
The anion SO4−− is strongly sorbed at pH 5.3, but not the cations.
Select Nernstian Eh values