Addition of Chemicals (pH Calculator)
The reaction module (button Reac) allows the addition of chemicals to any aqueous solution (input water). In the simplest case the input water is “pure water” (H2O). In this way you get the pH of an acid, base, salt or another chemical compound.
The addition of KOH increases the pH from 7.90 to 9.03 (output 1). In this way, calcite becomes supersaturated and precipitates, changing the pH back to 7.83 (output 2).
More Reactants. By activating the checkbox More reactions, up to three additional reactants can be added. An example is given here.
Plot Titration Curve. By activating the checkbox Plot Titration Curve, small portions of the reactant will be successively added to obtain pH plots. An example is given here.
List of Chemical Compounds (Reagents)
The addition/dosage can be done in units of mmol/L or mg/L. Typical pH values of common acids and bases are given in the pH Table.
“Forced Mineral Dissolution”
The Reac module includes also mineral phases denoted by the prefix “Mineral_”, such as
Suppose one sets 0.5 mmol/L of “Mineral_Gypsum” then exactly 0.5 mmol/L CaSO4 will be added to the input water. This approach is distinctly different from the thermodynamics of mineral dissolution and is called “forced mineral dissolution”.
In thermodynamics (which is used here), the mineral dissolves only as long as the solution remains undersaturated with the mineral (SI < 0). In other words, the (maximum) amount that dissolves is dictated by equilibrium thermodynamics and cannot be chosen arbitrarily.
The “forced mineral dissolution” bypasses the equilibrium thermodynamics. The selected amount of addition will always dissolve completely, regardless of whether SI > 0 or not. In this “crude way” one can simulate e.g. strongly supersaturated solutions.