Calc.  SED & PREDOM / Special Cases

Dissolved species with zero concentration

Some chemical species need a special treatment:

For these species the concentration must be set to zero (although their activity may be calculated).

For electrons it is possible to plot  log{e−} (= − pe), but the concentration of “free electrons” will not appear in a fraction or logarithmic diagram. Note that the total concentration of e− may be given in the input, see for example the data file EX5.DAT.

For water (H2O) it is not possible to give a total concentration.

Gases: only aqueous species and solids are considered when making a diagram, and the concentration (in mol/L) for gases is set to zero. The fugacity (≈ partial pressure) is calculated and it is displayed in “log activity” diagrams (example).