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

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

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

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

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

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)

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

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.

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.

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