Alfisol, Item 007: IExFit, version 3.2
Fit adsorption data based on ion exchange reaction models.
Display solid & liquid & gas phase speciation diagrams as a funciton of pH and redox conditions.

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Brief summary of modifications and/or errors fixed with each IExFit version released:


10 September 2018: version 3.2 released.
  • Added a button to allow redox reactions.
  • Added a tab to show redox diagrams (pe-pH or Eh-pH diagrams).
  • Expanded the user-defined database. Initial starter size of database offered with version 3.2 is 591 reactions. Addition of redox reactions are now allowed.
  • Gases and redox reactions and aqueous species are now calculated using the same algorithm. Thus, the loop counter (LC) display was also edited. Only solid species are calculated separately. Calculation of solid species greatly improved. Added more options for user to manipulate the convergence criteria.
  • Added option to overlay precipitation events with adsorption predictions; user chooses "removed" (rather than "adsorption") option if overlay is desired. Improved options to highlight specific output curves. Other minor aesthetic issues were fixed.
  • Tutorial was updated.


2 August 2016: version 3.1 released.
  • Added a button to allow addition of gases to the exercise. You can specify if the volume is infinite, variable or fixed. You can specify if the total pressure is variable or fixed. And you can also specify if the gas-liquid boundary is flat or curved (concave or convex) with a specified radius of curvature.
  • Added a tab to show gas species as a function of pH.
  • Expanded the user-defined database. Initial starter size of database offered with version 3.1 is 323 reactions. Addition of gases-liquid phase reactions are now allowed.
  • Improved controls for display of colors of symbols, lines, and highlight of any error events encountered.
  • Loop counter (LC) display edited. LC numbers now include number of gas phase calculations.
  • Very large data grid results were slow to display or would sometimes crash the program. This was fixed.
  • Other minor aesthetic issues were fixed. Control Center window buttons were rearranged to help user better understand what to do next.
  • Tutorial was updated.


11 March 2016: version 3.0 released.
  • Added a button to allow addition of solids to the exercise, and to identify which solids are allowed to precipitate.
  • Added a tab to show precipitation of solid species as a function of pH. IExFit will also calculate the log(SI) for all solids (including those solids that are not allowed to precipitate). log(SI) = log(saturation index).
  • Expanded the user-defined database. Initial starter size of database offered with version 3.0 is 304 reactions. Addition of solid precipitation and dissolution reactions are now allowed.
  • Added "max % ΔC" values to the "Mass Balance Error Summary" option.
  • Loop counter display edited. LC numbers now include number of solid precipitation/dissolution calculations. A progress panel display was also added.
  • Other minor aesthetic issues were fixed.
  • Tutorial was updated.


19 September 2015: version 2.1 released.
  • Allow user to cross-link the pK and adsorption maxima (Γmax) values in the adsorption model. That is, user can select which pK values are optimized as linked parameters. Similarly, user can select which Γmax values are optimized as linked surface sites.


23 August 2015: version 2.0 released.
  • Added a user-defined database. Initial starter size of database offered with version 2.0 is 186 reactions. This database is very easy to edit and expand as desired by the user.
  • Allow user to show plot of aqueous speciation of ions even when no adsorption model has been created.
  • Allow user to overlay the aqueous phase speciation plots.
  • Improve the table display for error analysis of results generated.
  • Globalization of software was improved. Some errors that could occur with use of commas for decimal notation entry of data and output of data were fixed.


25 June 2015: version 1.2 released.
  • Changed the formula to calculate the activity coefficient from the Guggenheim Equation to the Davis Equation (1938, JCS (resumed):2093-2098).


19 June 2015: version 1.1 released.
  • Added ionic strength options (calculate and display I values, or use fixed values). Resultant activity coefficients are also displayed. Speciation results grid now shows both concentrations and activity values of aqueous species.
  • Fixed the handling of adsorption maximum values when multiple minerals are used. Added display of "Total Solids" and "Total Specific Surface Area" information.
  • Edited the display format and scroll bar options for small screens. Also added options to change order of how reactions are displayed (i.e., added "move up/move down" commands).
  • Fixed the unit conversion problems for various concentration units.
  • Improved internal checks on the reaction input information. Likelihood of user input errors were reduced. Also improved the display of the net charge balance of the reactions entered by the user.
  • Details on the loop counter were added to all display grids for advanced users that checked the "analyze each loop" option.
  • Expanded the tutorial.


8 January 2015: version 1.0 released.