Why ${\mathrm{KMnO}}_4$ is not used as a primary standard?

Primary standard:

1. A reagent that is extremely pure which represents the number of moles in the material and is easy to weigh is known as a primary standard.

Potassium Permanganate:

1. Potassium permanganate has the chemical formula ${\mathrm{KMnO}}_4$.
2. It is a flexible and potent oxidant that may be used to classify a variety of substances by direct or indirect titration.
3. It is not used as a major standard since obtaining the pure form of ${\mathrm{KMnO}}_4$ is challenging because it is not free of ${\mathrm{MnO}}_2$.
4. Furthermore, the color of Potassium permanganate is so vibrant that it serves as its own indicator.
5. Hence, ${\mathrm{KMnO}}_4$ is not used as a primary standard, because it is difficult to obtain the pure state of KMnO4 as it is not free from MnO2. Also, the colour is so intense that it acts as its own indicator.