Iodometry
A redox titration in which iodine liberated by the analyte is titrated with standard thiosulfate.
Formula / equation
I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻
Unit
mol/L
In depth
An oxidising analyte liberates iodine from excess iodide, and that iodine is then titrated. Starch is added only near the end point, when the colour has faded to pale straw, because it forms a strongly adsorbed complex with high concentrations of iodine.
Examples in the real world
Determining dissolved oxygen by the Winkler method; measuring the available chlorine in bleach.