A phase is a part of a chemical system that contains entities and has a separate mass balances for primary entities.
Or more concrete: each primary entity gets an individual mass balance for each phase in the system: <entityname>.<phasename>
Example commonly used phases are:
- “diss” (dissolved),
- “ads” (adsorbed),
- “min” (mineral),
- “tot” (total),
- “gas” (gaseous)
Phases can be linked hierarchically and are defined as follows:
@phase(liter, tot, watervolume)
@phase(diss, liter, 1)
@phase(min, liter, 1)
In this case the “tot” phase is the parent phase for a liter, gas and min phase.
Once we have defined the phases and their hierarchy, we can define entities in these phases
All primary entities get a separate mass balance in each phase.
A species is a special form of entity that is automatically placed in the “.diss” phase.
So defining Ca+2 as a species and primary entity
@species(Ca+2, 2) @primary_entity(Ca+2, -9.0, tot, 0.01)
We iterate for a given amount Ca+2.tot of 0.01 mol. Start estimation for Ca+2.logact = -9
This definition automatically defines the following variables for Ca+2
Ca+2.tot, (total amount in system, mol, includes amounts in child phase liter x watervolume) Ca+2.diss (total amount in diss phase, mol/l) Ca+2.min (total amount in min phase, mol/l) Ca+2.liter (total amount in liter phase, includes amounts in diss and liter child phases