m.scharrer

Dear Melika, in the attachment you can see a react file in which I testet the effect of titration of 1 mole of O2 and 1mol of H+ into a simple NaCl 10wt% fluid. As you can see in the PNG file, the O2(aq) value changes over several log units whereas the H+ activity stays nearly constant. I am interested in knowing the reason for this distinct difference in behavior between O2 and H+. Ive looked at the activity coeficient and fould that it is 1 for O2 and around 0.8 for H+. However, this difference should not account for the variation stated above. Another option is that H+ is buffered in the system and O2 is not. However i could not find out what buffers my H+ activity so dramatically. So my question is: Why does the titration of equal amounts of O2 and H+ into the system affects O2 and H+ on scales of several log units differently? Sincerely Manuel O2-H titration test.rea

Dear Melika, im sorry, I must have forgossen to click "attach this file" after inserting it. Sincerely Manuel

Hello everyone, I am using React and am starting at log fO2 = -10 and log H+ = -10 I have noticed that if I add one mole of H+ into the system, the logH+ of the system barely changes. If I however add 1 mole of O2, the logO2 value changes over more than 10 log units. This effect is independant of starting conditions and is visible throuout all reaction paths ive modelled. What is the reason for the fact that if equal amounts of O2 and H+ are added, the pH barely shifts but the logO2 changes dramatically? Sincerely Manuel

Dear Melika, its not an error message that i recieve but the T-fO2 diagram is not complete. As you can see in the attached photo, ive circled the area where the mineral area is not boundet towards the aqueous species. FUrthermore, the diagramms still do not match (the fO2-pH diargam in the picture is calculated for 20 °C) Sincerely Manuel

Dear Melika, I have tried the extrapolate option and the results are not the same for Act2 and Tact. Furthermore, weirs errors occur (see attachment) Sincerely Manuel

Dear Melika, I have already looked at the SpecE8 results for the same concentrations as ive used in my GSS file. My problem is that: 1) for Act2 i input one activity for each element (species). However if i plot fO2 vs. pH the activity of each species is variable relative to fO2 and pH. What activity should be inserted into Act2? 2) in GSS i can calculate activities of species without inserting a specific pH, T and fO2. For what parameters are the calculated activities representative. Sincerely Manuel

I have tried the extrapolate K option, hower, with no improvement. It only adjusts the fO2-pH diagram but Act2 and Tact are still not relatable. T-fO2_Zn-As-S.tac fO2-pH_Zn-As-S-100°C.ac2

Hello Admin, if i am interested in a fO2-pH Predominance diagram of Fe of a speculated fluid with for example the following parameters: H2ASO4 as As = 50 mg/l SO4-- as S = 50 mg/l Fe++ as Fe = 10 mg/l Na++ = 39.34 g/kg Cl- = 60.66 g/kg T = 150 °C ive been using GSS to calculate the activities of specific species which i applied in Act2. For the GSS calculations i did not input any pH value since it will be my x-axis on my diagram. Now my question is if that is the correct procedure since of course using specific pH values in GSS gives me different activities of my species and thus greatly altering the predominance diagram in the end? For what pH or in general for what terms do the activities calculated in GSS apply if no pH is entered? Sincerely Manuel

Thank you for the reply and the help with extrapolating the K values. However, I am still not recieving coinciding results with tac and act2. I have also tried different databases. an example of a system using thermo.tdat: activity of SO4-- = 1E-6 activity of Zn++ = 1E-8 activity of As(OH)4- = 1E-5 all species are speciated over x and y

Hello everyone. Comparing diagrams from Act2 and Tact, I realized that the results are not identical but differ quite a bit. The disagreement is not just based on a small shift in predominance boundaries but mainly by the occureing of other stable phases (aqueous and solids). These differences become more promenent the more complex my system becomes (the more elements are in the system) What is the cause of this disagreement and is there a way to fix it? Thank you for your attention.

Personally i only have a Students version of GWB but at work, a collegue has the standart version 10.0.10 which we use to model reaction paths. To beginn with, we want to cool a fluid of known composition from 230 to 110 °C which is a simple case. For our modeling, we will use the current thermoddem database (http://thermoddem.brgm.fr/) due to the included species. At first we succesfully cooled the fluid with standart parameters. If we constrain the fluid useing the flow-through and/or dump command, the following error arrises: Exit: React stop: no species React is ending . We have tried to decrease deltaxi from 0.01 to 0.001 and 0.0001 as this was stated in a previous forum post to possibly solve this problem. However, this made no difference. The commands used are: data = "C:\Program Files\Gwb\Gtdata\thermo_thermoddem_lvl2_no-org_11dec14.tdat" verify pH=5.0 temperature initial = 230, final = 110 swap e- for O2(aq) e- = -100 mV Na+ = 27.5 g/l K+ = 3.25 g/l Ca++ = 6.9 g/l Mg++ = 125 mg/l Cl- = 59 g/l SO4-- = 59 mg/l Br- as Br = 220 mg/l F- as F = 4.5 mg/l Sr++ as Sr = 450 mg/l Li+ as Li = 140 mg/l Mn++ as Mn = 15 mg/l Ba++ as Ba = 10 mg/l Fe++ as Fe = 100 mg/l B(OH)3(aq) as B = 35 mg/l H4SiO4(aq) as Si = 213 mg/l Al+++ as Al = 6 mg/l H2AsO4- as As = 6 mg/l Al+++ as Al = 0.05 mg/l Rb+ as Rb = 22 mg/l Cs+ as Cs = 14 mg/l Ge(OH)4(aq) = 53 ug/l Be++ as Be = 30 ug/l Ni++ as Ni = 100 ug/l Cu++ as Cu = 45 ug/l Co++ as Co = 50 ug/l CrO4-- as Cr = 40 ug/l Cd++ as Cd = 10 ug/l Zn++ as Zn = 3000 ug/l Ti(OH)4(aq) as Ti = 200 ug/l Pb++ as Pb = 300 ug/l HCO3- = 85 mg/l balance on HCO3- dxplot 0 dump flow-through