Iodimetric and Iodometric Titrations

IODIMETRIC AND IODOMETRIC TITRATIONS

NTRODUCTION

Iodimetric and iodometric titrations constitute another class of oxidation-reduction titrations wherein either iodine solutions are employed directly for the assay or an equivalent amount of iodine is liberated indirectly from the reaction mixture and then assayed.

Iodimetry is a procedure based on the following reversible reaction :

2I^–   < = =>   I₂ + 2e

Hence, it can be utilized for the quantitative estimation of reducing agents like arsenites (H₃AsO₃) and thiosulphates (Na₂S₂O₃) by employing a standard solution of iodine.

Iodometry is an indirect procedure based on the aforesaid reversible reaction whereby the assay of oxidizing agents, for instance : ‘available chlorine’ in bleaching powder, cupric and ferric salts may be carried out by reducing them with an excess potassium iodide thereby liberating an equivalent quantity of iodine which can be estimated using a standard solution of thiosulphate.