Re: Please help!

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

I am attaching the source databases that I have for llnl.dat and the newest
minteq database (Fall of 2000, I believe), which I have not yet translated
into PHREEQC format. I believe the equations in the two databases are
different. llnl.dat writes the equation with acetic acid, while minteq
writes the reaction with acetate. References are included as comments in
the llnl.dat database. Minteq lists abbreviated references as well.

David


(See attached file: llnl.thermo.dat)(See attached file: minteq.thermo.dbs)


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


                                                                                                                             
                      Zhi Ling Zeng                                                                                          
                      <z.zeng@xxxxxxxx         To:      dlpark@xxxxxxxx                                                      
                      edu.au>                  cc:                                                                           
In-Reply-To: <3.0.32.20010417194839.007331a8@xxxxxxxxxxxxxxx>
                                               Subject: Please help!                                                         
                      04/17/01 02:48                                                                                         
                      AM                                                                                                     
                                                                                                                             
                                                                                                                             



Dear Sir,

I have noticed something interesting whilst using PHREEQC for copper
speciation modeling.  I have noticed that the llnl.dat database has
provided different stability constants for the various copper acetate
complexes to the Minteq database (please see the table below):


                                     Cu                      Acetate
             Log_k

llnl.dat                       1                       1
             2.525
                                     1                       2
                   5.882
                                     1                       3
                   9.379
                                     1                       4
                     -

Minteq.dat                     1                       1
             2.22
                                     1                       2
                   3.63
                                     1                       3
                   3.1
                                     1                       4
                   2.9

The constants shown above, especially the ones displayed in llnl.dat, are
significantly higher than the literature values.  Since the quality of the
speciation model predictions is solely dependant on the stability constants
used, the discrepancies between the logK values may result in confusion and
inaccurate predictions of the speicies distribution.  Could you please
comment on the situation and could you please also tell me what the sources
of the constants listed in llnl.dat and Minteq.dat are?

Thanks in advance for your help!

Yours sincerely,
Zhi Ling ZENG

Attachment: llnl.thermo.dat
Description: Binary data

Attachment: minteq.thermo.dbs
Description: Binary data