Iodometry

Iodometry, known as iodometric titration, is a method of volumetric chemical analysis, a redox titration where the appearance or disappearance of elementary iodine indicates the end point.

Note that iodometry involves indirect titration of iodine liberated by reaction with the analyte, whereas iodimetry involves direct titration using iodine as the titrant.

Redox titration using sodium thiosulphate, Na₂S₂O₃ (usually) as a reducing agent is known as iodometric titration since it is used specifically to titrate iodine. The iodometric titration is a general method to determine the concentration of an oxidising agent in solution. In an iodometric titration, a starch solution is used as an indicator since it can absorb the I₂ that is released, visually indicating a positive iodine-starch test with a deep blue hue. This absorption will cause the solution to change its colour from deep blue to light yellow when titrated with standardized thiosulfate solution. This indicates the end point of the titration. Iodometry is commonly used to analyze the concentration of oxidizing agents in water samples, such as oxygen saturation in ecological studies or active chlorine in swimming pool water analysis.