Hi Greg, I think you want to adjust the pe, rather than the pH, when you find the fixed SO4/H2S ratio. See if the following does what you want. TITLE sulfur SI PHASES fix_S H2O + SO4-2 = H2S -no_check -log_k 0 SELECTED_OUTPUT -file int_S.sel -reset false -ph true -totals S(-2) S(6) -activities H2S SO4-2 -saturation_indices S SOLUTION 1 units mol/kgw temp 25 S 0.1 pH 1 pe 1 fix_S 0 SOLUTION 2 units mol/kgw temp 25 S 0.1 pH 2 pe 1 fix_S 0 SOLUTION 3 units mol/kgw temp 25 S 0.1 pH 3 pe 1 fix_S 0 SOLUTION 4 units mol/kgw temp 25 S 0.1 pH 4 pe 1 fix_S 0 SOLUTION 5 units mol/kgw temp 25 S 0.1 pH 5 pe 1 fix_S 0 END I tried just adjusting the pe to the phase boundary in the reaction step by adding H2. Apparently, this affects the pH (SO4-2 -> S-2) more than it affects the ratio (SO4/H2S), and it does not converge. I think the program is working ok, it is simply not possible to attain a SO4/H2S ratio in this way. At any point you can adjust both the pe and the pH with the following and I think it should work. EQUILIBRIUM_PHASES fix_S 0.0 H2 10 fix_pH -5 NaOH 10 # with appropriate definition of fix_pH But you have to choose the pH that you want, in this case pH 5. I expect at some point all the polysulfides and other sulfur redox states will cause some problems. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled
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:
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 1831 since Jan 22, 1998.