Dear David, sorry for confusing you. Apparently, I confused the original database with my own one. I recently installed the newest PHREEQC release and thought that the original database was still in the directory. Instead I copied my own from an older directory and made the mistake about vivianite before. However, I can suggest a slight modification to the database from this. The article referred to (Al-Borno & Tomson) provides thermodynamic data about the solubility constant of vivianite. The authors used the MINTEQA2 database for data interpretation and their data is therefore suitable for some of the database related to PHREEQC. The results in PHREEQC format read: Vivianite Fe3(PO4)2:8H2O = 3 Fe+2 + 2 PO4-3 + 8 H2O log_k -35.767 delta_h 5.05 kJ -analytic 234.205 0.0 -12242.6 -92.510 log_k differs somewhat from the original value in PHREEQC (-36.000) and no temperature dependence was included. I apologise for my own mistake. best regards, jasper David L Parkhurst wrote: > > I looked in phreeqc.dat, wateq4f.dat, llnl.dat, and minteq.dat, and none > have analytical expressions for vivianite, nor can I find any instance of > the number 234.205 in any of the databases. So I'm confused as to where to > locate the error; it looks like it is not in any of the databases that I > distribute. > > David > > David Parkhurst (dlpark@xxxxxxxx) > U.S. Geological Survey > Box 25046, MS 413 > Denver Federal Center > Denver, CO 80225 > > Project web page: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled > > > Jasper Griffioen > <j.griffioen@xxx To: David L Parkhurst <dlpark@xxxxxxxx>, Tony Appelo <appt@xxxxxxxxx> > g.tno.nl> cc: In-Reply-To: <3D33DB4C.F418064B@xxxxxxxxxxx> > Subject: phreeqc-database > 07/16/02 02:37 > AM > > > > Dear David and Tony, > > Herewith I would like to ask your attention for a small mistake in the > PHREEQC database (and maybe other databases as well). > > The values for the analytic expression for the solubility of vivianite > should read: > > +234.205 0.0 -12,242.6 -92.510 > > instead of > > -234.205 0.0 +12,242.6 +92.510 > > The reason is presumably that Al-Borno & Tomson (GCA(58/24), 5373-5378) > report the analytic expression for pK instead of logK. > > Best regards, > Jasper Griffioen > > _____________________________________________________________________________________________ > This inbound message from KPN has been checked for all known viruses by KPN IV-Scan, powered by MessageLabs. > For further information visit: http://www.veiliginternet.nl > _____________________________________________________________________________________________
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