What is CHEAQS?
CHEAQS Next is a computer program for calculating CHemical
Equilibria in AQuatic Systems. You supply
input data, the program calculates the chemical speciation for
you. CHEAQS Next is free but it is not cheap.
- You can calculate the concentration of complexes, but you can also calculate:
- redox equilibria;
- complexation by natural organic matter (four different
models, three developed by Tipping and co-workers: Model V,
Model VI and Model VII; one developed by Cabaniss &
- solids that are formed due to oversaturation (or just calculate if they are oversaturated or not);
- adsorption (surface complexation model).
- pH: you can either specify a fixed pH or have the program calculate the pH for you.
- Input: you can edit input interactively (screenshot) or read from an input file.
- Output: You can view output on your screen (screenshot; updated September 2016), save in an output file, or export to an .CSV or .XML file (both types can be read by spreadsheet programs like EXCEL 2002 and later).
CHEAQS Next comes with a large database. Documentation is
available for each equilibrium reaction in the database so you
can always trace the source of an equilibrium reaction. In the
periodic table on the right, you can see (in green) which
elements are covered in CHEAQS Next' database. The database
- 52 cations (H+, Li+, Be2+, Na+, Mg2+, Al3+, K+, Ca2+, Sc3+, Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Co3+, Ni2+, Cu+, Cu2+, Zn2+, Ga3+, Rb+, Sr2+, Y3+, Zr4+, Pd2+, Ag+, Cd2+, In3+, Sn2+, Sn4+, Cs+, Ba2+, La3+, Ce3+, Pr3+, Nd3+, Pm3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+, Hf4+, Hg2+, Pb2+, Bi3+, U(VI)O22+);
- 34 ligands (OH-, H2BO3-, CO32-, NH3, NO2-, NO3-, F-, H2SiO42-, PO43-, S2-, SO32-, SO42-, Cl-, VO43-, CrO42-, MnO4-, H2AsO3-, AsO43-, SeO32-, SeO42-, Br-, MoO42-, I-, WO42-, CN-, acetate, catechol, salicylate, phthalate, NTA, citrate, HEDTA, EDTA and DTPA;
- 1969 complexes;
- 273 solids;
- 81 adsorption equilibria (as calculation examples);
- 16 redox equilibria (for Fe, Co, Cu, Sn, Cr, Mn, Pb, N, S, As and Se);
- 4 gases (CO2, NH3, H2S, SO2);
- organic complexation according to the models of:
- Tipping & Hurley (GeoChim. CosmoChim. Acta, 1992); Tipping (Comp. GeoSc., 1994) also known as WHAM or Model V;
- Tipping (Aquatic Geochemistry, 1998) also known as WHAM-6;
- Tipping et al. (Environmental Chemistry, 2011), also known as Model VII;
- Cabaniss & Shuman (GeoChim. Cosmochim. Acta, 1988a,