Two Calculation Pathways
Once the input water is given there are two principal ways to proceed:
- Button Start – to interprete and proof a water sample (CBE, calcite saturation etc.)
- Button Reac – to add 1 to 4 chemicals (acids, bases, salts)
In case of reactions you even can start from pure water (i.e. H2O instantiated by button New) to mimic a pH calculator (cf. online demo).
The calculation paths from the input water to the final solutions (Output 1, Output 2) can be sketched as follows:
Two Output Solutions
Irrespective of the selected path (button Start or Reac) aqion always provides two aqueous solutions:
- Output 1 – chemical equilibrium without mineral phases
- Output 2 – chemical equilibrium with mineral phases
whereas the input water (raw data) is usually neither in the state of chemical equilibrium nor is it charge-balanced.
According to the above scheme the results of the calculations are presented in form of tables with three columns: Input, Output 1 and Output 2.
The charge-balanced solution Output 1 (of the left pathway) enters the calculation to determine the calcium carbonate saturation state.
Two optional settings are available and worth noting:
- pCO2 – to establish equilibrium with atmospheric CO2 (pCO2 = 3.41)
- pe value – to establish a given redox potential (pe value)
Both options simulate a so-called ‘open system’ where the solution stays in contact with an unlimited reservoir of CO2 and/or O2. Thus, in the first option, a definite amount of CO2 is added or removed from the solution in order to establish the given partial pressure of CO2 gas. In the second case, a definite amount of O2 is added or removed from the solution in order to establish the given pe value (redox potential).
[last modified: 2014-11-30]