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PHREEQC question



Mr. Parkhurst,

I was trying to use your program to duplicate some results that I found in:

Marine Chemistry, 1988, volume 23
p. 295-309
authors: Luther and Church

Specifically, on p. 305, they claim to use PHREEQE to calculate pE's for
known pH, Fe(II), and SO4. They assume equilibrium with pyrite. To perform
this in PHREEQC I wrote the following:


TITLE	Example to calculate pE from Luther and Church (1987)

SOLUTION 1 High Salinity site, June 1986(after flood), 2.5 to 5.0cm
units	umol/kgw
pH	6.22
temp	25
S(6)	43700
Fe(2)	67

PHASES
pH_Fix
H+=H+
log_k	0.0

EQUILIBRIUM PHASES
Pyrite 0.0 
pH_Fix	-6.22	HCl	10



END


I did get similar numbers (not the same numbers though), but is the
technique correct? You mention several times in you FAQs list that it is not
a good idea to control pE or pH in this manner... but I couldn't figure out
how else to do it. I don't want to develop poor technique and have something
critical fail on me in the future.

Dan


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