Which substance is commonly used for the standardization of KMnO4?

Sodium oxalate is commonly used for the standardization of potassium permanganate (KMnO4) because it reacts stoichiometrically with the permanganate ion under acidic conditions. The redox reaction between KMnO4 and sodium oxalate involves the reduction of permanganate to manganese(II) ions while simultaneously oxidizing oxalate to carbon dioxide. This reaction is beneficial for standardization because it provides a clear endpoint, indicated by the color change of the solution, which shifts from purple (due to KMnO4) to colorless or light pink (due to the formation of manganese(II) ions).

Using sodium oxalate for this purpose is advantageous due to its stability and the ease with which it dissolves in water to form a consistent solution for titration. These properties make sodium oxalate a reliable primary standard for determining the concentration of KMnO4 in volumetric analysis, which is critical for accurate and precise analytical measurements.