Alfisol, Item 007: IExFit, version 3.1
Fit adsorption data based on ion exchange reaction models.
Display solid & liquid & gas phase speciation diagrams as a funciton of pH.

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Step 2: Enter Initial Conditions

Here you enter the concentration of the ions present in your experiments.

In the example shown below,
.... H(+) and OH(-) values are set by the equilibrium pH conditions
.... the total phthalate ion concentration added was constant
.... the Na(+) concentrations added were pH dependent due to the variable addition of NaOH to control the pH
.... the Cl(-) concentrations added were pH dependent due to the variable addition of HCl to control the pH

In the example shown below, the Cl(-) ions were also later determined to exist in the solid surface and thus contribute to the total Cl(-) ion concentrations present. Rather than having to re-enter all the pH dependent values, you simply edit the "Native Concentration" cellbox information.

You also enter here the temperature of the experiment. This will temperature-correct the database equilibrium constants.

You also enter the ionic strength condition, which is either at a fixed value or is calculated by IExFit based on the ions remaining in solution. IExFit uses the Davis Equation to calculate the activity coefficient of each ion in the aqueous phase, which is then used to correlate ion activity with ion concentration.