Calc.  SED & PREDOM / SED

A solubility diagram shows total dissolved concentrations (on a logarithmic scale) usually plotted against a free concentration. It is convenient to set the activity = 1 for the solid phase of interest. This can be done by exchanging a component for a reaction, for example exchanging Ca2+ with CaCO3(s).

The following diagram shows the solubility of calcite in the system H+, CaCO3(s), and CO2(g) at log PCO2 = −3.5:

Solubility diagram

This diagram was obtained with the following input file:

3  8  1  1,
H+,CO2(g),CaCO3(s)
OH-     , -14.00 -1 0 0, HCO3- , -7.83 -1 1 0
H2CO3(aq), -1.48  0 1 0, CaOH+ , -3.12 1 -1 1
CaCO3(aq), -5.22  0 0 1, CaHCO3+, 2.91 1  0 1
CO3-2   , -18.16 -2 1 0, Ca+2  ,  9.74 2 -1 1
Ca(OH)2(s),-13.07 0 -1 1
ls,0,-7, H+,
lav,-5,-11,
la,-3.5,  la,0