[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Manual calculations versus phreeqc

Can you tell me if this difference is significant and if so where I might
going wrong?

I would not consider the difference significant. Both numbers indicate
calcite is reacting fast enough to maintain equilibrium.

I'm not sure how you are  doing the hand calculation, but PHREEQC prints
the molalities, activities, and log activity coefficient for each aqueous
species. You should be able to compare directly to the hand calculation.


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

                      "Garrett Kilroy"                                                                                 
                      <kilroyg@xxxxxxx         To:      <dlpark@xxxxxxxx>                                              
                      tcd.ie>                  cc:                                                                     
In-Reply-To: <LPBBLDFBJADNFPNHNHGJCEGGCBAA.kilroyg@xxxxxxxxxxx>
                                               Subject: Manual calculations versus phreeqc                             
                      07/21/01 10:50                                                                                   
                      Please respond                                                                                   
                      to kilroyg                                                                                       

Dear Sir/Madam,
I would be very grateful if you could assist me in this query.

I am using Phreeqc to calculate calcite saturation indices for my PhD.
However, my manual calculations are coming out different to the Phreeqc
As a test I used data from a hydrogeology textbook (Fetter(2001) applied
hydrogeology, p360-1) which calculates calcite saturation manually. The
textbook gives a saturation index of 0.05 while Phreeqc gives a saturation
index of -0.02.
Can you tell me if this difference is significant and if so where I might
going wrong?
I would welcome any suggestions.
Best regards,

Garrett Kilroy
PhD Candidate

Department of Geology/
Centre for the Environment
Trinity College
Dublin 2
Tel: +353 1 608 2403
Fax: +353 1 671 8047

Project Home Page
Complete Water Resources Division Software
USGS Home Page
Water Resources Division Home Page
NRP Home Page
Help Page
USGS Privacy Statement       

Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. 

The URL of this page is: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/mail/msg00282.html
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 2665 since Jan 22, 1998.