Re: PHREEQC reaction

["David L Parkhurst" <dlpark@xxxxxxxx>]

You should define the phase in a PHASES data block. You should use a
"dissociation" reaction with the new phase as the first entity on the
left-hand side, all other entities on left and right-hand sides should be
aqueous species. The log K is immaterial to inverse modeling, but will
affect the saturation indices calculated for initial solutions.

That said, H2SiO3 is not a common phase formula. I would use SiO2(a),
quartz, or chalcedony (just one). The only difference of these with your
phase is a water in the formula, which should make almost no difference in
the mole transfers that are calculated.

David


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


                                                                                                                     
                      Elizabeth Bryant                                                                               
                      <elb46+@xxxxxxxx         To:      dlpark@xxxxxxxx                                              
                      >                        cc:                                                                   
In-Reply-To: <14446485.3212477731@xxxxxxxxxxxxxxxxxxxxxxxx>
                                               Subject: PHREEQC reaction                                             
                      10/19/01 08:55                                                                                 
                      AM                                                                                             
                                                                                                                     
                                                                                                                     



Mr. Parkhurst,

I am working with PHREEQC and using the LLNL database.  I have a reaction
             SiO2 + H20 = H2SiO3
along with the log k.  I tried inputing this information as one of the
phoses for inverse modeling, but I got an error message saying that PHREEQC

didn't recoginize H2SiO3. I know that LLNL has SiO2 as the master species
for Si.  I was wondering how to input H2SiO3 as a master species.  I tried
entering a new master species before, but it seemed like I entered it
incorrectly, because the program still didn't recognize it.  If you could
please help me out with this matter, I would greatly appreciate it.

Thank you for your time,
Elizabeth Bryant