By this point you may be wondering how to perform chemical equilibrium calculations yourself. After all,
it's fine to talk about the benefits of this technique, but if it is too complicated to apply to your work then
what good is it?
Calculating chemical equilibrium for all but the most simple waters requires the use
of a computer program. There are several around, some of which you can get for
free. Many of them base their numerical algorithms around the MINEQL program
which was developed at MIT in the mid 1970's. I'm not going to go into a
description of MINEQL here. It suffices to say that MINEQL maintained such a
robustness and elegance that it was hard to beat. Any of the improvements that
came to MINEQL over the years never tampered with its core numerical techniques.
Some of the other models worth looking into are MINTEQA2 (developed in the mid
1980's for the USEPA), PHREEQC (developed by the US Geological Survey) and
MINEQL+ (which I will talk more about later). In fact, there have been hundreds of
derivative programs created of the last 30 years. Many were never intended to be
used by a broader audience; many assumed that you would have a fairly advanced
knowledge of computers and programming.
How to Go About Performing
These Calculations
By this point you may be wondering how to perform chemical equilibrium calculations yourself. After all, it's fine to talk about the benefits of this technique, but if it is too complicated to apply to your work then what good is it?

Calculating chemical equilibrium for all but the most simple waters requires the use of a computer program. There are several around, some of which you can get for free. Many of them base their numerical algorithms around the MINEQL program which was developed at MIT in the mid 1970's. I'm not going to go into a description of MINEQL here. It suffices to say that MINEQL maintained such a robustness and elegance that it was hard to beat. Any of the improvements that came to MINEQL over the years never tampered with its core numerical techniques. Some of the other models worth looking into are MINTEQA2 (developed in the mid 1980's for the USEPA), PHREEQC (developed by the US Geological Survey) and MINEQL+ (which I will talk more about later). In fact, there have been hundreds of derivative programs created of the last 30 years. Many were never intended to be used by a broader audience; many assumed that you would have a fairly advanced knowledge of computers and programming. 
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