surface_data = FeOH.sdat decouple Fe+++ swap Fe(OH)3(ppd) for Fe+++ Fe(OH)3(ppd) = 1 free g/kg Na+ = 100 mmol/kg Cl- = 100 mmol/kg pH = 4 Zn++ = 1e-6 mmol/kg scope x slide pH to 12 scope y react 3 mmol of Zn++ react 6 mmol of Cl- sorbate include precip = off