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RE: Release of PHREEQC 2.7 and PhreeqcI

> I am trying to use PHREEQC to simulate the formation of green rust (iron
corrosion product). Its formula is considered to be
first Fe is in 2nd valence and the second Fe is in 3rd valence (So I might
write it as Fe(II)4Fe(III)2(OH)12SO4. But the PHASE data block in PHREEQC
seems only to accept single valent element on left hand side. I thought of
SOLID-SOLUTION but the green rust is not yed considered as any aggregate of
other phases. I don't know if there is any other way to handle this

> the reaction equation is:

> Fe4Fe2(OH)12SO4 = 5Fe(OH)2 + Fe2+2 + SO4-2 + 1/2O2 + H2O

This equation should be adequate for the PHASE definition. I just did a
little balancing for PHREEQC:

Fe4Fe2(OH)12SO4 = 5Fe(OH)2 + Fe+2 + SO4-2 + 0.5O2 + H2O

If this stoichiometry is added to solution, the iron will be distributed
between +3 and +2 states depending on electron acceptors. With no
additional electron acceptors in the system the ratio of Fe(2):Fe(3) should
be 2:1.


David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

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