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What is CHEAQS?

CHEAQS is a computer program for calculating CHemical Equilibria in AQuatic Systems. First the user specifies a set of total concentrations, then CHEAQS will calculation the chemical speciation.

You can not only calculate the concentration of complexes, you can also calculate:

• redox equilibria;
• adsorption (surface complexation model);
• complexation by natural organic matter (4 different models - including Tippings' Model V, Model VI and (new!) Model VII;
  
• solids that appear by oversaturation (or just calculate if they are oversaturated or not).

CHEAQS is freeware. CHEAQS is popular as well (see the list of publications).

CHEAQS runs under Windows. Using an emulator like wine, it may also run under Linux (not tested).

Why use CHEAQS?

Well, CHEAQS is easy to use.
Entering the input concentrations is like working in a spreadsheet program. Anyone can do that. Want to modify the database? Just use the menu commands and enter your information interactively (see Database). Output is shown in tables and in graphs (see example on the right). You can see not only the concentration of a species, but also activity, equilibrium constants (intrinsic and conditional) and literature reference.

• You can titrate, for question like: what happens to the concentration of free copper when I add 1 mM of ETDA in 100 steps?
  
• You can calibrate, for questions like: how much EDTA should I add to decrease the concentration of free copper by a factor of 2?
• You can enter one sample, then run it, view the output and decide further.
• You can enter special samples at once, then run all of them.
• Even batch mode is supported.

If you wish, you can register to receive emails when there is news. You can also follow CHEAQS on Twitter.

CHEAQS was written by Wilko Verweij (see page About author).

System requirements

Conditions for use

Contact author

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