Tom Meuzelaar

Hi Helge: Unfortunately, I'm not aware of anyone who is doing work near 0C, nor do I understand much about all of the complications that arise when you approach freezing. I'm hoping that another user with more familiarity finds this post and can comment on this... Best regards, Tom

Hi Henry: In your custom rate law, try changing 'Ksp' to 'K', as React will only recognize the latter as a valid parameter for the equilibrium constant. If it still doesn't work, please attach the entire React script, so I'm sure to compare apples to apples.. Best regards, Tom Meuzelaar RockWare, Inc.

Dear GWB Users: We have released GWB 8.0.7, which addresses the following issues: Correct flaw in 8.0.6 update affecting launching SpecE8 from GSS. Preliminary support for Windows 7. Correct problem converting to units of electrical equivalents when making certain plots. In GSS, allow mixing of samples in arbitrary mass ratios. User can set header and trailer commands when launching SpecE8 and React from GSS. GSS can compute component and species concentrations as Calculated Analytes. User can choose to ignore zero-valued and less-than-valued cells in GSS, when performing calculations. GSS can use a value reported for carbonate alkalinity to constrain the carbonate composition of a fluid. Fix various issues in Gtplot and Xtplot, especially with respect to selecting units. Correct several problems with overlaying scatter data in Gtplot and Xtplot. New predefined variable "Time elapsed" in GSS to simplify adding scatter data to plot of kinetic simulations. Landscape printing of GSS data sheets. Assure data legend fits onto printouts of scatter plots User's Guides are hyperlinked Better support for landscape and color printing from GSS Improved "connect scatter points" feature in Gtplot and Xtplot Show per-kg units in GSS when calculating charge imbalance Fix a problem in multithreaded polythermal runs using Pitzer model Improve label positioning when copying special plots to clipboard Implement control scripts Provide two header files for user DLLs missing in 8.0 install Correct minor problem with report command Fix all known problems with the GUI Resolve all known issues with 8.0 through 8.0.6 Note that this patch includes the flaw in the alkalinity command in GWB releases 8.0 through 8.0.4 (addressed in previous patch 8.0.5). All current GWB Essentials, Standard and Pro version 8 users can download the GWB 8.0.7 patch here. Please contact me with any questions. Regards, Tom Meuzelaar RockWare, Inc.

Dear Helge: The GWB databases are actually formulated to work down to 0C, not 25C. Regards, Tom Meuzelaar RockWare, Inc.

Dear GWB Users: We have released GWB 8.0.6, which addresses the following issues: Preliminary support for Windows 7. Correct problem converting to units of electrical equivalents when making certain plots. In GSS, allow mixing of samples in arbitrary mass ratios. User can set header and trailer commands when launching SpecE8 and React from GSS. GSS can compute component and species concentrations as Calculated Analytes. User can choose to ignore zero-valued and less-than-valued cells in GSS, when performing calculations. GSS can use a value reported for carbonate alkalinity to constrain the carbonate composition of a fluid. Fix various issues in Gtplot and Xtplot, especially with respect to selecting units. Correct several problems with overlaying scatter data in Gtplot and Xtplot. New predefined variable "Time elapsed" in GSS to simplify adding scatter data to plot of kinetic simulations. Landscape printing of GSS data sheets. Assure data legend fits onto printouts of scatter plots User's Guides are hyperlinked Better support for landscape and color printing from GSS Improved "connect scatter points" feature in Gtplot and Xtplot Show per-kg units in GSS when calculating charge imbalance Fix a problem in multithreaded polythermal runs using Pitzer model Improve label positioning when copying special plots to clipboard Implement control scripts Provide two header files for user DLLs missing in 8.0 install Correct minor problem with report command Fix all known problems with the GUI Resolve all known issues with 8.0 through 8.0.5 Note that this patch includes the flaw in the alkalinity command in GWB releases 8.0 through 8.0.4 (addressed in previous patch 8.0.5). Please contact me with any questions. Regards, Tom Meuzelaar RockWare, Inc.

Hi Peng: You can look at the calculations behind an entire activity diagram by choosing the Run - View - .\Act2_output.txt menu option. I think this will answer all of your questions. Regards, Tom

Sure- in the thermo database, just above the equilibrium constant data, you'll see all of the chemical components involved in the reaction, and their stoichiometric coefficients. The below image shows what this looks like for Calcite: Note that a negative symbol in front of the stoichiometric coefficient means the component is on the reactant side (with Calcite), whereas a positive symbol refers to a component on the product side of the reaction. I hope that helps, Tom

Hello: There is not a log K value for any particular mineral, only an equilibrium constant for a mass action equation that involves a mineral. In this case, the difference stems from how the dissolution reaction for Calcite is written. The log K data you see in the literature reflects the following reaction: CaCO3 = CO32- + Ca2+ Whereas in thermo.dat, the dissolution for Calcite is written as: CaCO3 + H+ = HCO3- + Ca2+ However, if you add the thermo.dat reaction for CO32- (log K = -10.3439) to the previous reaction: HCO3- = CO32- + Ca2+ ..you'll find that you get both the reaction and equilibrium constant commonly reported in the literature. I hope that helps, Tom Meuzelaar RockWare, Inc.

Hi Peng: 1) Indeed, since this is an activity diagram, all species concentrations must be input as activities. 2) If you specify an activity for Cu++, you are constraining the non-ideal concentration (or activity) for the dissolved Cu++ species. 3) Any boundary in Act2 is simply the mass action equation between the species/minerals on either side of the boundary written in terms of the axis species. For example, on a Quartz solubility diagram with log SiO2 activity as the Y-axis and -log H+ activity (pH) as the X-axis, the boundary between dissolved silica and Quartz is expressed by the reaction: Quartz = SiO2(aq) Which has the mass action equation: K = aSiO2(aq) From the thermodynamic database, the log K value at 25C for this reaction is -3.9993. Substituting for K and aSiO2, and switching to log scale, we come up with the final equation as it's plotted in Act2: Y = -3.999 Note that since the reaction is only written in terms of the Y-axis (ie. not in terms of H+ activity), there is a Y-intercept, but no line slope- that is, the line plots as a horizontal line on the activity diagram. I hope this helps. Regards, Tom Meuzelaar RockWare, Inc.

I am able to reproduce the 90% imbalance error, but not the 13%, as I'm not sure how you've configured your bicarbonate units, but maybe this will help... Note that constraining your Basis using carbonate alkalinity vs. bicarbonate concentration is setting up a completely different problem: if you constrain your Basis using 1728 mg/kg carbonate alkalinity, this is the equivalent ~.017 molal CO3-- (at your very alkaline pH of 12.5) if you constrain your Basis using 1728 mg/kg HCO3- component, this is the equivalent of ~.029 molal CO3--, or roughly twice the alkalinity as the first configuration The latter configuration results in a much higher negative charge imbalance. I hope that helps, Tom Meuzelaar RockWare, Inc.

Hello: With the exception of classroom licenses, virtually all copies of GWB are run via a hardware lock. The message that a license file is missing simply indicates that GWB is having trouble recognizing the hardware lock. To resolve hardware lock (dongle) issues in version 6: - be sure the dongle is plugged in and lit up - download and install the version 6 HASP fix tool on the GWB downloads page. Please let me know if this does not address the issue. Regards, Tom Meuzelaar RockWare, Inc.

Hi: Can you tell me what version of the software you are using? (Click on the Help - About React menu option in the React module). Regards, Tom Meuzelaar RockWare, Inc.

Hi Ruth: The attached script mostly resembles figure 2, other than that the default thermo database is missing data for anilite, djurlite and Cu4(OH)6Cl2. Re-creating the diagram is one thing, but understanding the assumptions behind it are another, so feel free to ask me questions about this configuration. Regards, Tom Meuzelaar RockWare, Inc.

Hi Julie: The script now converges, and I my point plots ok on the Piper diagram in Gtplot 7.0.6 - I'm not convinced that the HCO3+CO3 point is not recognized- it just appears that the combined HCO3+CO3 concentration is extremely low relative to Cl+SO4/Mg+Ca, so it essentially plots along the zero axis. Agreed? Regards, Tom

Hi Herdis: GWB calculates TDS according to the following formula: TDS = (Mass_solution - Mass_solvent) / Mass_solution This formula gives a correct conversion from mass fraction to molal units, and vice versa. As an aside- TDS is not a precise measurement of a well-defined physical quantity. Instead, it is a standardized test, the results of which vary depending on the extent to which volatiles like H2O and CO2 are lost from or retained in the residuum during desiccation. There will always be discrepancies between lab tests and theoretical calculations, and between calculations that account for or neglect the distribution of H2O. Regards, Tom Meuzelaar RockWare, Inc.

Hi Julie: The script as you sent it to me, does not converge, so I cannot evaluate this. I assume the issue is with the oxygen concentration, which is set to 1,766,000 mg/L (usually, 5-8 mg/L is equilibrium with the atmosphere). Am I using the same script you are using? To answer your question about scatter data- have a look at the section entitled Adding Scatter Data in the Help menu of Gtplot. You can plot multiple scatter data points and assign symbols, colors and sizes to them, but labels and a legend are not possible. You'd either need to port the image out in vector format to Adobe Illustrator (or similar), or take advantage of the better scatter data and plotting options by upgrading to version 8. Regards, Tom

Hi Julie: What version of GWB and thermo database are you using? Would you mind attaching the SpecE8 script to save me the data input work? Regards, Tom Meuzelaar RockWare, Inc.

Almost. It looks like Barite and Witherite both precipitate along the course of the reaction path- Barite precipitates at the beginning of the reaction path, and continues to precipitate until there's .007 molal in the system. Witherite begins to precipitate about 20% into reaction path progress, and continues until there's 2e-4 molal in the system. At 40% reaction path progress (Xi = .4), both minerals reach saturation, and there is no further precipitation. However, the mineral masses remain in the system. I hope that helps, Tom

Can you attach the script in it's current state so I can take a look? Regards, Tom

In Gtplot, just generate a plot of Minerals vs. Rxn progress. If you don't see BaSO4 precipitating, I'd plot Mineral Saturation vs. Rxn progress. Regards, Tom

Yes- any component you titrate into the Basis system must also be present in the Basis. If you don't have a lab value, just specify a very small Ba++ concentration in the Basis. Regards, Tom

There is an mineral called BaCl2© in the default database you are using (thermo.dat). I don't know much about BaCl- are you titrating this in as a solid? You could check some of the other databases to see what minerals/species they have- have a look at section 2.3 Thermo datasets in the v8 GWB Essentials Guide. Also- if you use the Config - Show option in React, you can quickly find all minerals or aqueous species in the database you've loaded for a given component. Hope that helps, Tom

Hi Ruth: You can change the fugacity (non-ideal partial pressure) of any gas in your system in React in the Reactants pane via the add - sliding - fugacity option. That said, GWB is not really suited for modeling boiling. You might take a look at the code Chiller (see: Reed, M.H., 1982, Calculation of multicomponent chemical equilibria and reaction processes in systems involving minerals, gases and an aqueous phase, Geochimica et Cosmochimica Acta 46, 512-528), which is well suited for this purpose. Hope that helps, Tom Meuzelaar RockWare, Inc.

Sure- keep your original solution in the Basis tab; in the Reactants tab, choose Add- Simple Reactant - Aqueous - BaCl2; specify the mass to be titrated, and click Run. You'll have a lot of output data, so I recommend moving to plotted output (Gtplot) for analysis. Hope that helps, Tom

Hi Drew: I'm not sure I understand the question. Units on the rate constant must change depending on how the rate law is posed. Note for instance when you add inhibiting/promoting species that rate constant units change depending on whether or not you cast the species as concentrations or activities. Regards, Tom Meuzelaar RockWare, Inc.