Adding solutions¶

A Solution is an aqueous composition that stays in the PHREEQC engine. You create it on a PhreeqPython instance.

There are two ways to define the composition: a complete PHREEQC SOLUTION block, or a known chemical recipe. Both assign a solution number automatically.

Adding a complete solution¶

Use add_solution when you have an analytical composition, or you need PHREEQC SOLUTION options: pH, pe, units, density, charge balance, redox, or equilibrium with a phase.

The dictionary is written as identifier lines in a SOLUTION data block. Keys and values are the same identifiers and data items as in the PHREEQC manual: temp, pH, pe, units, density, redox, element names, Alkalinity, and so on. Values may be numbers or strings when PHREEQC needs extra tokens (as HCO3, charge, a phase name).

PhreeqPython assigns the solution number; do not put a number in the dictionary.

from phreeqpython import PhreeqPython

pp = PhreeqPython()

solution = pp.add_solution({
    'units': 'ppm',
    'pH': 8.22,
    'temp': 25.0,
    'Ca': 412.3,
    'Mg': 1291.8,
    'Na': 10768.0,
    'K': 399.1,
    'Cl': 19353.0,
    'Alkalinity': '141.682 as HCO3',
    'S(6)': 2712.0,
})
print(solution)
print('pH', round(solution.pH, 2), 'SC', round(solution.sc, 1))

That call sends:

SOLUTION 0
  units ppm
  pH 8.22
  temp 25.0
  Ca 412.3
  Mg 1291.8
  Na 10768.0
  K 399.1
  Cl 19353.0
  Alkalinity 141.682 as HCO3
  S(6) 2712.0
SAVE SOLUTION 0
END

Typical SOLUTION lines you can pass through the dictionary:

• units: mmol/kgw, ppm, mg/L, …
• pH / pe: a number, charge, or equilibrium with a phase ('pH': '8 Gibbsite')
• element totals: 'Ca': 1, 'S(6)': 2712.0, 'Al': '0.2 mg/kgw'
• charge balance: 'Cl': 'charge'
• phase equilibrium on an element: 'Al': '1e3 Gibbsite'

See the SOLUTION keyword in the PHREEQC Version 3 manual for the full identifier list and syntax.

Adding a simple solution¶

Use add_solution_simple when the solution has a known chemical composition, for example a solution of 1 mmol NaOH. The dictionary keys are chemical formulas; the values are amounts. Optional arguments: temperature (default 25 °C) and units (default mmol; also mol, mg, or ug).

PhreeqPython creates an empty SOLUTION at that temperature, then adds the formulas in a PHREEQC REACTION step. Formula names follow PHREEQC (case-sensitive), as described in the PHREEQC manual.

naoh = pp.add_solution_simple({'NaOH': 1})
print(naoh)
print('pH', round(naoh.pH, 2))
print('Na mmol', round(naoh.total('Na'), 3))

That call sends:

SOLUTION 1
-temp 25
REACTION 1
NaOH 1.0
1 mmol
SAVE SOLUTION 1
END

Amounts are converted to mmol before the REACTION. Pass units='mg' (or another unit) when the dictionary is not already in mmol.