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From: Brugger, Joel (SAM) Subject: Where does the Palladium go? I join a script file simulating reduction of a groundwater by carbon. The fluid contains Pd. According to GTplot, the concentration of Pd in the fluid decreases dramatically as reaction progresses. However, there is no Pd minerals among the minerals! Where does this Pd go? Note that if I remove the flow-through option (flow-through off), life's good (or at least more confusing) and Pd appears among the minerals. I'm using the LLNL database, and I can reproduce the problem with GWB versions 3 and 4.03 (just got it today!). # Reduction of RC water by organic carbon # reset suppress Uranopilite Rabejacite suppress Pentlandite Violarite suppress Delafossite # precip off # balance on Na+ T 23 # O2(aq) 3 mg/l swap e- for O2(aq) Eh -0.023 # swap O2(g) for O2(aq) # log f O2(g) -50 # just above solubility of uraninite/coffinite pH 6.92 # swap NO3- for NH3(aq) # NO3- total mg/l = 45.73 Sb(OH)3(aq) total mg/l = 5.05e-5 VO++ total mg/l = 0.02201 H2O 1 kg solvent Na+ total mg/l = 209 Mg++ total mg/l = 61 Ca++ total mg/l = 105 K+ total mg/l = 7 F- total mg/l = 3.67 Cl- total mg/l = 275.71 # Br- total mg/l = .94 SO4-- total mg/l = 125.69 HCO3- total mg/l = 589.98 SiO2(aq) total mg/l = 34.22 # Li+ total mg/l = .029 # Al+++ total mg/l = .00225 Ti(OH)4(aq) total mg/l = .015485 # CrO4-- total mg/l = .0161216 # Mn++ total mg/l = .02456 Co++ total mg/l = .00084 Ni++ total mg/l = .01626 Cu++ total mg/l = .00541 Zn++ total mg/l = .00689 H2AsO4- total mg/l = .03674 Sr++ total mg/l = .63367 # Y+++ total mg/l = 6e-4 # Zr(OH)2++ total mg/l = .000141 MoO4-- total mg/l = .09593 Pd++ total mg/l = .00118 Ag+ total mg/l = 2e-5 # Cd++ total mg/l = .00029 Sn++ total mg/l = 7e-5 # Cs+ total mg/l = .00029 Ba++ total mg/l = .06431 # Ce+++ total mg/l = 3e-5 WO4-- total mg/l = .0081 # Au+ total mg/l = .00031 # Tl+ total mg/l = 1e-5 Pb++ total mg/l = .00053 UO2++ total mg/l = .754058 # Ga+++ total mg/l = .00187 # Rb+ total mg/l = .01352 # Sc+++ total mg/l = .01197 # NbO3- total mg/l = 1.5e-5 # B(OH)3(aq) total mg/l = .571 # La+++ total mg/l = 2e-5 # Nd+++ total mg/l = 2e-5 # Sm+++ total mg/l = 1e-5 # Eu+++ total mg/l = 3e-5 # Gd+++ total mg/l = 2e-5 # Dy+++ total mg/l = 3e-5 # Ho+++ total mg/l = 1e-5 # Er+++ total mg/l = 3e-5 # Yb+++ total mg/l = 3e-5 suppress Quartz Tridymite Coesite Cristobalite(alpha) Cristobalite(beta) suppress Chalcedony # suppress SiO2(am) # swap SiO2(am) for SiO2(aq) # 100 free g SiO2(am) 0.01 molal SiO2(aq) # swap Hematite for Fe++ # 1 free g Hematite # Fe++ 1e-12 molal go pickup fluid flow-through react 0.07 g C react 10000 g SiO2(aq) delxi .05 log dx_init 0.00000001 go From: Craig Bethke Subject: Re: Where does the Palladium go? In a flow-through model, a reactant fluid displaces existing fluid from the system. Pb initially in solution in the system, therefore is lost over the course of the reaction path, as fluid is displaced. From: Brugger, Joel (SAM) Subject: Re: Where does the Palladium go? I'm afraid that I'm still confused. According to the yellow manual, flow-through just prevents back-reaction between precipitated minerals and fluid, while flush dispaces the fluid (which i can't do with the present model as I haven't defined the displaced aquifer fluid). Also, if I plot the total composition of the system, the amount of Pd remains constant, as does the amount of H2O. So how can the concentration of Pd decrease in the fluid ? From: Craig Bethke Subject: RE: Where does the Palladium go? Sorry, I misunderstood your question. Please ignore my last response. Where does the Pd go? It falls off the end of the computer chip. There is little Pd in your run, only about 10^-17 moles. Metallic Pd saturates over the course of your path and precipitates, but of course only an extremely small amount forms. In a flow-through model, React transfers after each reaction step the minerals that formed over the step into a set of isolated minerals. A very small amount -- effectively a zero mass -- of the mineral must remain behind in the equilibrium system, to maintain the basis. Your computer can carry a number to only about 12 or 13 significant digits. This means that the mass of Pd the program wants to leave behind for numerical reasons is more than the mass that has precipitated. So the Pd never makes it the list of isolated minerals, and therefore does not appear in your plotted output. But that very small mass is there, as far as React is concerned -- it is not lost and there is no mass balance problem. You just can't see it in your plots. All that said, React is commonly a poor tool for modeling trace elements because it doesn't account for the trace element content of minerals that might form or dissolve. In your case, for example, you need to ask yourself whether Pd is likely to precipitate as a truly minuscule amount of metal, or whether it would more likely coprecipitate as impurities in the other minerals that form.

From: Katie Aguilar Subject: HFO Sorbing Surfaces I am modeling leachate through a clay layer. The contaminants of concern are metals, there are no organics in this problem. I am trying to model the natural attenuation in clay as the leachate runs through a set volume of clay (8 cubic feet) with a CEC = 0.6 eq/g. The model works well when I use the ion exchange script for the model. However, when I add in the FeOH script, it tells me that the reactants are charge imbalanced by -539.8, and it does not continue the model. I am running GWB (React) Release 4.0.2 on Windows 2000, and have attached the script. I am also using the default thermo dataset. # React script, saved Tue Jan 06 2004 by kaguilar data = "C:Program FilesGwbGtdatathermo.dat" verify surface_data = "C:Program FilesGwbGtdataIonEx.dat" surface_data = "C:Program FilesGwbGtdataFeOH.dat" exchange_capacity IonEx = .6 eq/g time start = 0 days, end = 20 years temperature = 25 decouple Fe+++ swap Kaolinite for Al+++ swap Quartz for SiO2(aq) swap Goethite for Fe+++ 66.4 kg free H2O free kg Kaolinite = 173.3 free kg Quartz = 218.6 total mg/kg Mg++ = 94.59 total mg/kg H+ = -.1047 total mg/kg SeO3-- = .3186 total mg/kg Cr+++ = 1.074 total mg/kg Pb++ = .01556 total mg/kg Hg++ = .0004979 total mg/kg Ag+ = .4979 total mg/kg As(OH)4- = .9769 total mg/kg Ba++ = .0001944 total mg/kg O2(aq) = 132.9 total mg/kg Cl- = 28.88 balance on Na+ total mg/kg Na+ = 988.1 total mg/kg K+ = 291.7 total mg/kg SO4-- = 2755 free kg Goethite = 8.3 density = 1.013 react 9.42 kg of H2O react 4.69 mg of Ag+ react 9.2 mg of As(OH)4- react .0018 mg of Ba++ react 272 mg of Cl- react 11.1 mg of Cr+++ react -.986 mg of H+ react .0047 mg of Hg++ react 2747.8 mg of K+ react 891 mg of Mg++ react 9307.9 mg of Na+ react 1251.9 mg of O2(aq) react .15 mg of Pb++ react 25.95 kg of SO4-- react 3 mg of SeO3-- flush itmax0 = 1000 itmax = 1000

From: Scheerhorn, Rosario V Subject: kinetic sulfur I am running React and I am trying to add the kinetic mineral sulfur. Does anybody know where I can find the rate constant and surface area for such mineral. I've been looking without any luck.

From: Scheerhorn, Rosario V Subject: Molar volume of H2S(g) I am trying to run React and it's asking for the molar volume of H2S (g). Does anybody know where Ican get that kind of information. From: Richard Laffers Subject: Re: Molar volume of H2S(g) Specific volume of H2S(g) is 0.699 m3/kg, according to http://www.airliquide.com/en/business/prod...ex.asp?GasID=59. Recalculated to molar volume it is about 23823,248 cm3 per 1 mole of H2S. However, I don't know how to input the molar volume into GWB, since editing dataset doesn't seem to work in this case. Actually, molar volumes of gases depend significantly on temperature - it's not good to constrain gases in volume units. My advice is: use fugacity to constrain H2S(g) in your initial system. If H2S(g) is a reactant in your model, constraining in units other than cm3 should work (e.g. gram, mol, ...)

From: Rosa Maria Barragan Subject: Modeling diluted waters Dear GWB users, we want to make geochemical modeling with mineral saturation in some very diluted waters from Colombia, where Cl concentration is under 3 ppm. We have had problems apparently with iterations, could we have some clues regarding this? From: Craig Bethke Subject: Re: Modeling diluted waters You didn't include an input script demonstrating the issue, so it's hard to answer your question definitely. As a guess, perhaps you are trying to charge balance on chloride, instead of a cation or anion of larger concentration?

From: Antoine de Haller Subject: temperature dependence in Tact I have problems with the Tact program in speciating SO4-- on mozaic diagrams when plotting Fe++ vs fO2(g) at fixed pH or vs pH at fixed fO2(g). The program does not take into account Temperature dependent species changes and therefore plots wrong diagrams. From: Craig Bethke Subject: Re: temperature dependence in Tact It turns out that the program is working correctly, if not according to your expectations. When you speciate a basis entry, the program considers all of the species that can be constructed from that entry, water, and the species on the axis (or axes) in question. For example, if you speciate SO4-- over pH, the program accounts in its speciation calculations for SO4-- and HSO4-, but not H2S, HS-, etc. You can manipulate the configuration by swapping the basis. If you swap HS- for SO4-- and then speciate it over a pH axis, for example, the program will consider the sulfide instead of sulfate species. Remember that in any Act2 or Tact calculation, you can view complete details of how the diagram was generated by inspecting the Act2_output.txt (or Tact_output.txt) file. Just click on Run - View. Finally, if you want to create diagrams for chemical systems more complicated that can be represented easily in an activity-activity or activity-temperature diagram, you can use React and Gtplot to create a speciation diagram.

From: Dimitri Vlassopoulos Subject: f(O2) vs T diagram in TACT I have been trying to calculate a redox-vs-temperature species predominance diagram for inorganic nitrogen using TACT, but the program repeatedly crashes. I have tried switching to different thermo databases, but no change. Any suggestions/insights would be greatly appreciated. Also, to kill 2 birds with one email, are the MINTEQA2, WATEQ4F and /or PHREEQE thermodynamic databases available in the format read by the Geochemist's Workbench programs?

From: Laiq Rahman Subject: Suppress options Is there any method to prevent a basis species from appearing on a (TACT/ACT2) diagram once it has been swapped out of the basis? From: Craig Bethke Subject: Re: Suppress options There is a way, but it involves making a small change to the thermo dataset. Suppose you want to suppress SO4--: 1) Save the thermo dataset under a new name, and use this as your working copy. 2) Choose another species such as HSO4- to be the new basis species. Add it to the group of basis species at the top of the dataset, and remove it from the list of aqueous species. 3) Add SO4-- to the list of redox couples. The reaction to form it should be written in terms of HSO4-, the new basis species. Use the "block" command in Rxn to balance the reaction and output the entry for the thermo data. 4) Copy the entry from Rxn_block.txt and paste to the thermo dataset. 5) Rebalance any other reactions (in this case, HS-) among the redox couples containing SO4-- so that they are written in terms of HSO4-. Again, use the "block" command of Rxn. Leave all other entries (aqueous species, minerals, ...) as they are. 6) Make sure the headers are correct: you now have one fewer aqueous species and one more redox couple. 7) Now you are ready: run Act2, read in the new thermo data (you will receive a warning that SO4--/HSO4- does not form a redox couple, which you can ignore), and suppress SO4-- in your diagram.

From: Laiq Rahman Subject: redox models using TACT We are finding it impossible to use code that incorporates a redox aspect in the TACT program but we have no problems with ACT2. The TACT program crashes giving a "segmentation fault" error message when the code incorporates lines setting oxygen fugacities etc. We are using the Solaris version of GWB (v3.0). The example of code below works but crashes if we add a line to fix the O2 activity, i.e. log activity O2(aq) = 1e-40 data = thermo.dat verify swap H2S(g) for SO4-- diagram Fe++ vs pH log activity main = -3 log activity Cl- = -3 log fugacity H2S(g) = -3 x-axis from 0 to 14 increment 1 y-axis from 100 to 200 increment 5 From: Craig Bethke Subject: Re: redox models using TACT We have sent you an updated version of Tact (3.0.2) that handles redox reactions a little better. However, the immediate problem with the your input script is the line log activity O2(aq) = 1e-40 You should set either log activity O2(aq) = -40 or activity O2(aq) = 1e-40 to get the result you want.

From: Paul Foellbach Subject: new database I am attempting to use the database "thermo_com.R7beta" together with TACT, when I do this, TACT can't work with this database, because this database is defined for the temperatures from 0.1 to 300°C and TACT calculates between 0 and 300°C. How can I change the temperature setting of TACT ? From: Craig Bethke Subject: Re: new database You didn't enclose a script showing this behavior, so it's hard to comment. You set the temperature range for a Tact calculation with the “y-axis� command. If the temperature range in the thermo data continues to cause you difficulty, I suggest you change the first entry in the temperature table (at the top of the dataset) from 0.0100 to 0.0000.

Subject: Act2/Tact question From: Jennifer Houghton We are noticing that whenever we try and run Act2 or Tact with a high temperature/pressure database (400 degrees, 500 bars) these two programs report steam saturation pressures on the plots even though the database is not set at steam saturation. Is this just a hardwired calculation that the program runs to report a pressure on the plot or is this actually the program rewriting the database? We would like to verify that the programs are using the log K's we specified in the database (500 bars) and not a calculated log K at steam saturation. From: Craig Bethke Subject: Re: Act2/Tact question The pressure reported on Act2 and Tact plots is the confining pressure that you set with the “pressure" command. The default value is 1 atm below 100 C and the L-V curve at higher temperature. The programs use this value to determine positions of the water stability limits, and to set fugacities for any gases that may appear in the diagram. See Chapter 3 of the Users' Guide for more info. The GWB programs wouldn't dream of messing around with your thermo data. They use the log K's directly if you work at one of the principal temperatures in the thermo dataset, or figure values from polynomial fits to the log K's if you work at other temperatures. Nonetheless, since it's never a good idea to trust a computer program completely, you can quickly verify the position of any line on an Act2 or Tact diagram with by hand calculation or using Rxn.

From: Richard Laffers Subject: pH buffering I encountered two problems while using GWB: 1. REACT: I wonder how can I buffer pH by a certain reaction during reaction path. For instance, I wish to model cooling of hydrothermal fluid from 300C to 200C while pH in the system is buffered by the reaction Annite + .5 H2O + 3 H+ + 3 Albite = 7.5 Quartz + Maximum_Microcline + 1.5 Chamosite-7A + 3 Na+ e.g. annite to chlorite conversion, at the presence of Qtz, Alb, Microcline (=other rock-forming minerals present in my system). (I got this reaction running the script annite2chamosite.rxn). Since pH of the reaction is temperature dependent, simple fixing pH on the Reactants pane is not reasonable. Sliding pH would have been applicable only if pH was linearly dependent on temperature. Is there currently a way to buffer pH by a reaction in the React program? 2. ACT2, TACT: I wish to draw Eh-pH and T-pH diagrams concerning stability and coexisting of Annite and Chamosite (or Annite and Daphnite). Running any of the attached scripts did not yield satisfactory results, as I couldn't force both phases to be present at the diagram. Does anybody know how to deal with this? { WinXP Proffesional + SP1, GWB 4.0.3, thermo.com.v8.r6+.dat } +++ annite2chamosite.rxn +++ # Rxn script, saved Mon Feb 09 2004 by ja data = "C:Program FilesGwbGtdatathermo.com.v8.r6+.dat" verify temperature = 300 C react Annite swap Quartz for SiO2(aq) swap Maximum_Microcline for K+ swap Albite for Al+++ swap Chamosite-7A for Fe++ log activity H2O = 0 pH = ? log activity Na+ = 0 long +++ diagram_BT-CHL.ac2 +++ # Act2 script, saved Mon Feb 09 2004 by ja data = "C:Program FilesGwbGtdatathermo.com.v8.r6+.dat" verify temperature = 300 C swap Annite for Fe++ swap e- for O2(aq) swap Quartz for SiO2(aq) swap Maximum_Microcline for K+ diagram Annite on Eh vs pH log activity main = 0 x-axis from 0 to 14 increment 1 y-axis from -1.5 to 1.25 increment .25 +++ diagram_BT-CHL_Eh.tac +++ data = "c:program filesgwbgtdatathermo.dat" verify swap Annite for Fe++ swap Quartz for SiO2(aq) swap Chamosite-7A for Al+++ swap "Maximum Microcline" for K+ swap e- for O2(aq) diagram Annite vs pH log activity main = 0 Eh = -.1 x-axis from 0 to 14 increment 1 y-axis from 0 to 300 increment 10 +++ diagram_BT-CHL.tac +++ data = "c:program filesgwbgtdatathermo.dat" verify swap Annite for Fe++ swap Quartz for SiO2(aq) swap Chamosite-7A for Al+++ swap "Maximum Microcline" for K+ diagram Annite vs pH log activity main = 0 x-axis from 0 to 14 increment 1 y-axis from 0 to 300 increment 10 +++ diagram_BT-CHL+Al.ac2 +++ data = "C:Program FilesGwbGtdatathermo.com.v8.r6+.dat" verify temperature = 300 C swap Annite for Fe++ swap e- for O2(aq) swap Quartz for SiO2(aq) swap Maximum_Microcline for K+ swap Chamosite-7A for Al+++ diagram Annite on Eh vs pH activity main = 1 x-axis from 0 to 14 increment 1 y-axis from -1.5 to 1.25 increment .25 From: Craig Bethke Subject: Re: pH buffering (1) To buffer a system in React by equilibrium with an assemblage of minerals, simply swap the minerals into the basis. If the assemblage is not stable (which is probably trying to tell you something), you can maintain the mineral assemblage by turning of the "precip" option, or by suppressing the mineral(s) that become supersaturated. BTW, the mineral assemblage you cite buffers the Na+/H+ activity ratio, not pH. (2) You don't see minerals Chamosite or Daphnite in your Act2 results because they can't be made up from the basis entries you specify, and hence aren't part of the chemical system. You can see the species considered in constructing a diagram by clicking on the "Log" pane, or by inspecting the output file (Run -> View -> Act2_output.txt). To get the diagram you describe, try swapping Microcline for Al+++, then setting a K+ activity.

From: Gregg Jones Subject: stability of pyrite I'm trying to determine if pyrite in limestone in the Floridan aquifer is stable under the set of ground-water conditions described below. I used ACT 2 and plotted the log of the activity of the sulfate/sulfide ratio vs pH. Pyrite falls comfortably within the pyrite stability field and I want to verify that I've set up the input correctly. Here's my input data for ACT 2: Diagram Fe++ on O2(aq) vs pH Swap SO4--/S- for O2(aq) Log a SO4-- = -2 Log a Fe++ = -7 Speciate SO4-- over X-Y x from 0 to 14; y from -25 to 30. go Some additional info: pH = 6.99 Sulfate Conc. = 1,526 mg/l Sulfate Activity = 1.59 X 10 -2 Sulfide Conc. = 14.5 mg/l Sulfide Activity = 1.51 X 10-4 Iron Conc. = 0.065 mg/l Iron Activity = 6.7 X 10-7 Using release 3.0 From: Craig Bethke Subject: Re: stability of pyrite The good news is that it's a safe bet that pyrite is thermodynamically stable in a water of neutral pH containing ferric iron, sulfate, and sulfide. I suspect the diagram you propose is not exactly what you have in mind (it's hard to know: there is no species S-; perhaps you mean HS-?). To determine if a diagram is appropriate for a purpose, first consider what reactions you wish to consider. After you've made the diagram, select Run -> View -> Act_output.txt and verify that those reactions were used to construct the diagram.

From: Alexander Neaman Subject: Act2 and databases from Minteq, PhreeqC, and Wateq4F I am trying to use Act2 with thermo_minteq_gwb4.dat (please find the script attached). I have an error message: "Act2 stops: wat_lim: lost H2(g). Act2 is ending". Setting Eh value (e.g. to 0.25 V) does not help to solve the problem. Any comments? Does someone else have problems with thermo_minteq_gwb4.dat? I use GWb 4.0.2 and Windows XP Professional. # Act2 script, saved Thu Dec 18 2003 by Sue Brantley data = "F:Program FilesGwbGtdatathermo_minteq_gwb4.dat" verify swap e- for O2(aq) diagram Al+++ on Al+++ vs H+ Eh = .25 log activity Citrate--- = -3 x-axis from -10 to 0 increment 1 y-axis from -10 to 0 increment 1 From: Craig Bethke Subject: Re: Act2 and databases from Minteq, PhreeqC, and Wateq4F Sounds like you might have set the "water limits" option, which is not compatible with the Minteq dataset, since it does not contain H2(g). (There's a reminder to this effect in the notes at the top of the dataset.) If you uncheck this option on the Options dialog, I think you'll be fixed up. From: James Cleverley Subject: Re: Act2 and databases from Minteq, PhreeqC, and Wateq4F This may be to do with the default name for H2(g) or O2(g) within the data file that you are using. If my memory serves me correctly the water dissociation equation (names of species) are hardwired somehow in the code. I know I had this problem when I defined Oxygen gas as O2(gas) instead of O2(g). Just check O2 and H2 gas in the data file.

From: Alexander Neaman Subject: how to export diagrams from Act2 I am wondering how to export activity-activity diagrams from Act2 in a format suitable to be pasted to Word or Power Point. Another question: In a particular diagram in the attached file, the names of the species are superimposed on each other (e.g. AlOH++, Al(OH)2+, and HAlO2 (aq) at the bottom of the diagram are all grouped together). I would like to move them up or down in order to make them readable, but I am not able to figure out how to do it. Any help would be appreciated. I am using GWB 4.0.2, Windows XP. Script: diagram Al+++ on Al+++ vs pH x-axis from 0 to 14 increment 1 length 9 y-axis from -10 to 0 increment .5 suppress Diaspore Boehmite line labels size = 20 From: James Cleverley Subject: how to export diagrams from Act2 The method I use for publications and presentations is the following. Remove all species/mineral labels from the plot in ACT2 the use Edit > Copy to copy to clipboard. Open up powerpoint and use Edit > Paste > Special > Picture to place a copy onto a powerpoint slide. Then you can simply add labels from within powerpoint. If you really can not get the plot looking the way you want, or you want to combine aspects of several plot then you can view the output file in ACT2 and use the coordinates supplied to reconstruct the diagram in Excel. This is what I have done for journal publications where font consistency is important. From: Michael C. Adams Subject: how to export diagrams from Act2 Don't use Photoshop, it will rasterize it. Use adobe illustrator or some such vector drawing program. I just tested it, once you "ungroup" the image, it works fine. From: Tom Meuzelaar Subject: how to export diagrams from Act2 To export your image to MS Word, I recommend saving as an EMF file- choose "File- Save Image", and then select the .emf format. The metafile format should be easily read by MicroSoft Word. Regarding the overlapping labels, I don't think there is a way to position them within Act2. Here are some options: 1. Change the axis range (make your x-axis/pH range smaller) so that the labels don't overlap 2. Save the image as a vector file (.eps format), and open them up in PhotoShop (or similar)- the individual items should be movable since the graphic is in vector format. 3. Plot the image without labels - "Plot- Character Sizes", then set "Species Labels" equal to zero. Then save the image in any format, and edit the image in any third-party image manipulation software.

From: John Pareizs Subject: Act2 - Which Si Activity Should I Use I would like to plot some React output on an activity diagram (see script below), but I am unsure of the appropriate Si species to use from the React output file. See a sample react input and output file below. Note that I have several somewhat similar solutions that I would like to plot on this activity diagram. Am I using the right Si species for the x axis? Which Si species log a from the React output file should I use? One thought I had was to sum the activities of the predominant Si species and use the log of this sum for my x value. Any thoughts, advice, suggestions, etc. would be appreciated. I am using GWB version 4.0.2

From: Alexander Neaman Subject: Al+++ vs. pH using thermo.dat and thermo.com.v8.r6+.dat I am plotting log a Al+++ vs. pH at 25oC using Act2, version 4.0 of GWb. When thermo.dat database is used, gibbsite appears to be as a solid phase in equilibrium and (Al(OH)4)- as a species at alkaline pH. When thermo.com.v8.r6+.dat is used, however, diaspore appears to be as a solid phase in equilibrium and (AlO2)- as a species at alkaline pH. (Al(OH)4)- is not present in the thermo.com.v8.r6+.dat database and (AlO2)- is not present in the thermo.dat database. I thought that gibbsite was the stable phase at 25oC. Does anyone know why gibbsite is not stable phase using the thermo.com.v8.r6+.dat database? From: Tom Meuzelaar Subject: Re: Al+++ vs. pH using thermo.dat and thermo.com.v8.r6+.dat Act2 plots different assemblages for the two databases because each database lists a different log K value at 25C for the same mineral formation reaction: Thermo.dat, log K at 25C: Gibbsite- 7.9603 Diaspore - 8.7517 Thermo.com.., log K at 25C: Gibbsite- 7.7560 Diaspore- 7.1603 Act2 will plot the lowest free energy assemblage. You can remove a mineral from consideration by using the 'Config- suppress' command. Note that when using thermo.com, you would need to suppress both diaspore and boehmite to get Act2 to plot Gibbsite. The reasons for the variations in the log K values among the databases I'll leave to someone better versed in the topic. From: Craig Bethke Subject: Re: Al+++ vs. pH using thermo.dat and thermo.com.v8.r6+.dat There's quite a bit of information about the various thermodynamic databases, as well as deficiencies of the aluminum data in thermo.com.v8.r6+.dat in Alex Smirnov's archive of queries to the Users' Group: http://gwb.geo.stonybrook.edu/. From: Jeffrey R. S. Brownson Just commenting that the Thermo.dat values are closest to the Robie et al. (1979) data and Apps et al. (1989) sets. I've found these original data to be the most internally consistent in the Al mineral assemblages for my own calculations.

From: Alexander Neaman Subject: how to plot my experimental data on activity-activity diagrams using Act2? I am wondering how to plot my experimental data on activity-activity diagrams using Act2. I am using GWB 4.0.2, Windows XP. From: Tom Meuzelaar Subject: Re: how to plot my experimental data on activity-activity diagrams using Act2? You can plot your experimental data as scatter data on Act2 using the "File- get scatter data" command. Note that your data must be stored as an ASCII text file. For details about formatting these files correctly, you can choose the "Help- adding scatter data..." menu command.

From: Geoffrey Thyne Subject: scatter plots I am trying to get a scatter plot of on an activity diagram of Ca2+/H+2 vs K+/H+. The diagram plots perfectly and the Act2 window indicates the program is finding and reading the scatter file but no points appear in the plot. I have also tried using the menu command to plot the scatter points but no joy.

From: Paul Foellbach Subject: swapping problems in Act I attempt to figure a diagram with y-axis=log((aFe++)/(aCu+)^2) and x-axis=log fO2 to find out the stability of Pyrrotite, Magnetite, Bornite, Chalcopyrit, Hematit and Pyrit. The system contains Cu, Fe and S. The Temperature is 300°C. Act2> swap Fe++/(Cu+)^2 for Fe++ -- Cannot identify bottom species in ratio -- Don't know species Fe++/(Cu+)^2 Act2> show system Diagram speciation of Fe++ on O2(g) vs Fe++ Temperature is 300 C, Pressure is 85.81 bars Working directory: c:programmegwb3.0.1 Basis is: Fe++ X-axis variable (main species) H2O Activity = 10^0 (solvent) S2(g) (swapped for SO4--) Fugacity = 10^-11.5 O2(g) (swapped for O2(aq)) Y-axis variable X-axis plotted from -40 to .01; Y-axis from -30 to 0 I have got problems to swap Fe++/(Cu+)^2 for Fe++. Could anyone tell me how I figure this diagram?

From: James Laurinat Subject: Activity-activity plots using nonbasis species I have attempted to use act2 to plot activity-activity diagrams using nonbasis species, Al(OH)4-/H+ instead of Al+++ or Al+++/H+ versus HSiO4--- instead of SiO2(aq). Activities for both the stability field and superimposed scatter data appear to be off by many orders of magnitude. Data that matched up well with the stability field on a Al+++/H+ versus SiO2(aq) plot were off by about 45 orders of magnitude on the aluminum axis and 30 orders of magnitude on the silicon axis. In both cases, the scatter data exhibited higher activities than the corresponding locations on the stability field. The thermo.dat data set was used to plot these diagrams. Prior to making the diagrams, the activities of HSiO4--- were added to the aqueous species list of this data set. Scatter data were entered in terms of the basis species H2O, H+, SiO2(aq), and Al+++. Activities of SiO2(aq) and Al+++ were calculated from the known silicon and aluminum concentrations for the scatter data and equilibrium distribution equations. Is there any way to generate correct activity-activity diagrams using nonbasis species? Does this require an addition of the species Al(OH)4- and HSiO4--- to the basis species list? If so, what should be entered for ion size? How would this impact the use of the related basis species Al+++ and SiO2(aq)?

From: Garry Davidson Subject: Plotting of siderite on fO2-pH diagrams We've recently had a controversy over whether GWB plots siderite correctly on fO2-pH diagrams...it appears that GWB can only consider the S species, or only the C-species, and not both S and C, for one diagram, but siderite requires consideration of the effect of both. It appears that siderite does not plot correctly in the current version. Questions: 1. Is this right? 2. Is there a way around it?

From: Davison V Vivit Subject: Problems with Substituting Solid Phase Thermodynamic Data for Use with ACT2 Prior to running ACT2, I substituted the dataset for Cr2O3 with a dataset for amorphous Cr(OH)3. I encountered the following problems: 1) the program would not execute without a molar volume value 2) the program would not execute with a formula weight value identical to the value found in the dataset for aqueous Cr(OH)3 I plugged in an estimated value for the molar volume for amorphous Cr(OH)3 and a formula weight that was nearly but not exactly the same as for aqueous Cr(OH)3, and the program executed yielding a solubility diagram for the amorphous Cr(OH)3 solid phase with associated Cr(III) aqueous phase species at 25 C (see attachment). Are these error observations correct? Is the molar volume needed to construct the diagram? How is the molar volume used in the computations? How does one arrive at a valid estimate of molar volume for a desired solid phase? From: William F. McKenzie Subject: Problems with Substituting Solid Phase Thermodynamic Data for Use with ACT2 WRT to log K = 500 = this is a flag that tells the program that there are not data at this temperature. WRT to molar volumes, you might ask yourself how the calculations are carried out (perhaps do one by hand for one of your boundaries in your activity diagram); and then you could answer your question. From: Craig Bethke Subject: Problems with Substituting Solid Phase Thermodynamic Data for Use with ACT2 You do not need to specify the molar volume of a mineral in the thermo dataset. If you do not know it, just enter a zero. This will prevent you from doing certain things in React, such as constraining a mineral's volume, calculating porosity, and so on. It will, however, have no effect on an Act2 calculation. Regarding the molar weight question, you should be able to enter the value for the Cr(OH)3 aqueous species. I tried this just now and the program ran without problem. Perhaps the reaction coefficients for the amorphous phase are not exactly correct? Finally, a log K of 500 indicates a lack of data. I think you will be less confused if you look at Appendix 3 of the GWB User's Guide, which discusses the thermo dataset and how to modify it.

From: Ian Hutcheon Subject: Activity of solids in act2 I am trying to figure out how to assign more than one activity for a solid species in ACT2. For the system: show system Diagram speciation of Paragonite on Na+/H+ vs SiO2(aq) Temperature is 25 C, Pressure is 1.013 bars Thermo dataset: .gtdatathermo.dat Working directory: c:program filesgwb Basis is: Paragonite (swapped for Al+++) Activity = 10^-2.57 (main species) H2O Activity = 10^0 (solvent) Na+/H+ (swapped for Na+) Y-axis variable SiO2(aq) X-axis variable The components that appear on a Paragonite, Na+/H+ vs SiO2(aq) diagram are as follows. Gibbsite Kaolinite Pyrophyllite Analcime Paragonite Albite low Clinoptil-Na Using the Aagaard and Helgeson approach to defining activities of these components in smectite requires assigning an activity for each of the components Paragonite and Pyrophyllite. However, we seem to only be able to define one activity? From: Craig Bethke Subject: Re: Activity of solids in act2 I think the following should work for you. The reactions for Paragonite and Pyrophyllite (like all the minerals) are written in the database as destruction reactions for a single stoichiometric unit of mineral. If you change the log K for these two reactions to log K + log a, where a is the desired mineral activity, therefore, this activity will be carried implicitly throughout your calculations. The easiest way to change the log K values is to use the “alter� command -- there's no need in this case to edit the thermo database.

From: Garry Davidson Subject: any developments on plotting siderite in Act2? Reading the manuals, Act2 can only plot phases for diagrams speciated over X-Y relative to one set of species, e.g., SO4--, whereas siderite requires speciation for C in X-Y as well.Is that still the case for GWB3.2? How can I modify the following text for Fe-S-O to best include siderite? swap O2(g) for O2(aq) diagram Fe++ on O2(g) vs pH T = 250 x = 2 to 10 y = -50 to -30 suppress FeO© suppress Troilite suppress Hercynite add SO4-- log a SO4-- =-3 log a Fe++ =2 speciate SO4-- over X-Y go From: Paul Barton Subject: Re: any developments on plotting siderite in Act2? I, too, am interested in siderite; and I write to call attention to the question of the quality of the compiled thermo data on siderite. When we model an epithermal ore deposit having the siderite + hematite assemblage, the data base proposes a PCO2 that is far too high for the probable temperature and depth (250 C and 500m). To the extent that the assembled data for siderite utilize "equilibrium" studies involving reduction of siderite to magnetite and graphite, BEWARE. Graphite is very slow to react, and those experiments need to be evaluated in that light. I my view, superior data (unfortunately not reversed, and for that reason not published properly) are available from the oxidative reaction to hematite and magnetite studied by Chou and Williams (1978), EOS, 59, 402. Chou and I mentioned this briefly in Econ. Geol. (1993), 88, 873-884. If someone else has discovered better data, please share them. From: Craig Bethke Subject: Re: any developments on plotting siderite in Act2? There is nothing magic about a mosaic diagram: you can assemble one simply by calculating diagrams for the various ligand species you wish to consider, trimming each diagram to the limits for its ligand species, and assembling the “tilesâ€?. You could you this with scissors and tape, but more likely you'd just use an Illustration program. For the example you cite, calculate a diagram for iron, speciating sulfur over x-y and carbonate over x. Calculate a second diagram as before, but replace the carbonate with methane (no need to speciate). Clip off the portion of the second diagram above the methane-carbonate bounds and paste what's left over the first diagram.