Craig Bethke

Thank you for your contribution! I have cited your code on our web page www.gwb.com/thermo.htm.

Hi Sanjoy, When you suppress a mineral, it is not available to use in the chemical system. It cannot precipitate and you cannot use it as an equilibrium buffer or kinetic reactant. Nonetheless, the mineral has a saturation state, which the programs calculate and report. Suppose for example you are constructing a model of weathering. You might reasonably suppress quartz, since it reacts too slowly buffer silica activity. Now quartz will not form in the simulation. You might want to know however whether at a point in the calculation the fluid is undersaturated or supersaturated with respect to the mineral. The model therefore figures quartz saturation and reports it in the output datasets. Hope this helps, Craig

I think you'll find quite a bit of data vanadium species and minerals in several redox states in the thermo dataset "thermo.com.V8.R6+.dat". Hope this helps, Craig

Hi Bron, Every decade or so, someone suggests scaling saturation indices in some way, so they can provide a measure of the amount of a mineral that might precipitate, or so saturation indices of various minerals can be compared to each other, or both. Unfortunately, the SI is no more than a measure of the instantaneous energy that would be liberated (or consumed) if the precipitation reaction would begin to move forward. Trying to find a scaling that would add to this meaning is I'm afraid a fool's errand. I think if you were to take out pencil and paper and play around with the idea you mention, you'd agree. HTH, Craig