“…Our purpose is to present the code for the program PHREEQE -±/ and a sufficient theoretical discussion (on an elementary level) to provide the user with a grasp of the basic chemical and thermodynamic concepts and assumptions used in PHREEQE. We will not treat in any detail the general subject of chemical modeling, as several recent and comprehensive reviews on the subject are available (Leggett, 1977;Perrin, 1977;Nordstrom and others, 1979).…”