metal_edta {titrationCurves}

Complexation Titration Curve

Description

This function calculates and plots the titration curve for a metal ion analyte using EDTA as the titrant. The calculation uses a single master equation that finds the volume of titrant needed to achieve a fixed concentration of the metal ion, pM, as outlined in R. de Levie's Principles of Quantitative Chemical Analysis (McGraw-Hill, 1997).

Usage

metal_edta(conc.metal = 0.1, conc.edta = 0.1, vol.metal = 50, ph = 10,
  logkf = 8.79, alpha.metal = 1, plot = TRUE, eqpt = TRUE,
  overlay = FALSE, ...)

Arguments

conc.metal

Molar concentration of the metal ion analyte; defaults to 0.10 M.

conc.edta

Molar concentration of the EDTA titrant; defaults to 0.10 M.

vol.metal

Initial volume, in mL, of the solution that contains the metal ion analyte; defaults to 50.00 mL.

ph

The pH of the solution, which is used to calculate the fraction of EDTA present in its fully deprotonated form; defaults to a pH of 10.

logkf

The log of the formation constant, Kf, for the metal-EDTA complex; defaults to 8.79, which is the value for the complex of Mg2+ and EDTA.

alpha.metal

The fraction of the metal ion analyte that is not complexed by an auxilary complexing agent; defaults to 1, the value when there is no secondary complexing agent present.

plot

Logical; if TRUE, plots the titration curve.

eqpt

Logical; if TRUE, draws a vertical line at the titration curve's equivalence point.

overlay

Logical; if TRUE, adds the current titration curve to the existing titration curve.

...

Additional arguments to pass to plot() function.

Value

A two-column data frame that contains the volume of titrant in the first column and the solution's pMetal in the second column. Also produces a plot of the titration curve with options to display the equivalence point and to overlay titration curves.

Author(s)

David T. Harvey, DePauw University. [e-mail]

Examples

### Simple titration curve with equivalence point
ex11 = metal_edta(eqpt = TRUE)
head(ex11)

### Overlay titration curves using different pH values
metal_edta(ph = 12, eqpt = TRUE)
metal_edta(ph = 10, overlay = TRUE)
metal_edta(ph = 8, overlay = TRUE)