Soluble Complexes-
This is one of the output options that is offered in this program. See Output Tables for more information on the other types of Geochem output.
Geochem can calculate for each metal-ligand pair, up to six soluble complexes and up to three different simple solid phases (complexes and solids which contain no more than one component metal, one component ligand, and H+ or OH- ions).
See the Help file : "Example 1 General Case.geo" for an example of the "can precipitate" option. In this example, both complex and simple solid phase formation are considered.
This has always been a tough table to read, but is essential if someone wants the activity and/or concentration of an individual complex. In this table each complex or simple solid formed by a metal and a ligand has two rows of output. In the first row is listed the -log of the concentration (top part of the table) or activity (bottom part of the table) and then three stoichiometric coefficients (e.g., 11 1 or 11-1). The first is the number of metal ions, the second is the number of ligands, and the third is the number of protons consumed (if positive) or released (if negative) in the formation reaction. In the second row is the actual concentration or activity.
So, for Al PO4... there are two possible complexes. In the first complex, 4.731 is the negative log of the concentration, in the complex (111) one Al interacts with one PO4 and consumes one proton. The concentration of the complex is 1.86 x 10^-5 M. In the second complex, the negative log of the concentration is 5.669, (1 1 2) one Al complexes with one PO4 and 2 protons are consumed. The concentration of the complex is 2.14 x 10^-6 M.
Excerpted from the Geochem-PC version 2.0 user notes:
GEOCHEM can perform computations for 'mixed solids', i.e., solid phases that contain more than one metal, one ligand, and either H or OH. During a single program run it can simultaneously consider up to 20 metals and 30 ligands. For each metal-ligand pair, up to six soluble complexes and up to three different simple solid phases (complexes and solids which contain no more than one component metal, one component ligand, and H+ or OH- ions) can be considered. The thermodynamic database allows for up to 50 individual metals and 99 different ligands.
The conventions followed by GEOCHEM are best taken from the example reactions in the table below. Each complex or simple solid formed by a metal and a ligand is designated by three stoichiometric coefficients (e.g., 13 0 or 11-1); the first is the number of metal ions, the second is the number of ligands, and the third is the number of protons consumed (if positive) or released (if negative) in the formation reaction. The table shows that GEOCHEM 'thinks' in terms of formation reactions, i.e. association reactions for complexes and precipitation reactions for solids. All acid-base reactions are handled via proton exchange, and reactions that could be written as consuming OH-'s must be written instead as hydrolysis reactions releasing H+. All reactions must be expressed using the log K values for overall, not stepwise, reactions. Lastly, note that the program is indifferent to characteristics of solid phases other than reaction stoichiometry and solubility (see, e.g., the three Fe oxides/hydroxides given at the end of the table).