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Dave,
I have a question regarding Phreeqc for Windows. I am using v. 1.5.09 on a
machine running Windows 2000.
I am trying to simulate a laboratory metal-chelate titration. Solution 1
contains Cd in NaNO3 and an NH3/NH4+ buffer at pH 10.23. Solution 2
contains NaH2EDTA at pH 4.08. I save both solutions and get the
anticipated result for each but when I mix the two solutions, the resultant
pH is 12.8. I anticipate a negligible drop in pH, and lab data confirm
this. The output indicates that the pH is used to charge balance
regardless of any instructions I give otherwise. I have appended and
example of the input file. I am using a slightly modified version of the
llnl database to which I have added Edta and the corresponding protonation
and complexation reactions. The results of other simulations with the
database suggest that the problem does not lie within the amended
database. Do you have any suggestions for the correct way to set this up?
Thanks in advance for your time and consideration,
====
DATABASE C:\Program Files\Phreeqc\llnl-scb.dat
TITLE Test my modified llnl.dat = llnl-scb.dat
SOLUTION 1
units mmol/kgw
pH 10.23
Na 100
N(+5) 110 charge
Cd 5.0
N(-3) 179.3
SAVE SOLUTION 1
END
SOLUTION 2
units mmol/kgw
pH 4.08
Na 200
Edta 100
SAVE SOLUTION 2
END
MIX 1
1 0.100
2 0.001
END
===================================
Scott Brooks
Environmental Sciences Division
Oak Ridge National Laboratory
P.O. Box 2008, MS 6038
Oak Ridge, TN 37831-6038
phone: 865-574-6398
fax: 865-576-8646
For FedEx and other couriers
swap "Bethel Valley Road" for the
P.O. Box
===================================
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