A laboratory experiment on the study of the chemical equilibrium based on the reaction between ferric and iodide ions in solution with the formation of ferrous ions, free iodine, and triiodide ions is developed. The total concentration of iodide and triiodide ions in the reaction mixture during the reaction is determined by the argentometric titration; the concentrations of the other reagents and products are calculated using the material balance equations. The dependence of the equilibrium constant on temperature is also considered. The average values of K[subscript c] are 2.5 × 10[superscript 4] M[superscript -1] (35 °C) and 4.5 × 10[superscript 4] M[superscript -1] (45 °C). The experiment uses common reagents and simple equipment and can be performed in any educational laboratory. The basic procedure of processing the experimental data is quite simple and can be easily performed even by first-year students; however, the experiment can be extended in several ways to be suitable for advanced laboratory courses for upper-year undergraduates. Possible extensions are discussed, including calculating the activity coefficients and activities of the aqueous species using the extended Debye-Hu¨ckel equation, and comparing the experimental equilibrium constant with the values calculated from the thermodynamic data on the standard electrode potentials or the standard enthalpies and Gibbs energies of formation.