What is iodimetric titration and how is it different from iodometric titration?

Iodimetric Titration

Iodimetric titration, also known as iodimetry, is a method of direct titration where a reducing agent (the analyte) is titrated with a standard solution of iodine (Iâ‚‚). This process involves a single redox reaction where iodine directly reacts with the reducing agent until all the iodine is consumed, indicating the end point of the titration. Iodine is typically dissolved in a solution like potassium iodide (KI) to enhance its solubility in water45.

Iodometric Titration

Iodometric titration, or iodometry, is an indirect method of titration. It involves the reaction of an oxidizing agent with iodide ions to liberate iodine, which is then titrated with sodium thiosulfate (Na₂S₂O₃), a reducing agent. This process involves two redox reactions: the first liberates iodine from iodide by the oxidizing agent, and the second involves the titration of the liberated iodine with sodium thiosulfate. The end point is typically indicated by a color change using starch as an indicator135.

Key Differences

• Direct vs. Indirect: Iodimetric titration is a direct method where iodine is used as the titrant to react with a reducing agent. Iodometric titration is indirect, involving the liberation of iodine from iodide before titration with sodium thiosulfate45.

• Analyte Type: Iodimetry is used to quantify reducing agents by directly titrating them with iodine. Iodometry is used to quantify oxidizing agents by first liberating iodine and then titrating it with sodium thiosulfate5.

• Number of Redox Reactions: Iodimetry involves a single redox reaction, whereas iodometry involves two redox reactions45.