Physical Properties of Potassium Permanganate

Potassium permanganate occurs as dark purple crystals, melting at 513 K -- a somewhat lower melting point than that of potassium dichromate (671 K), consistent with the more covalent, less purely ionic character generally associated with the very high (+7) oxidation state of manganese in this compound. In terms of aqueous solubility, potassium permanganate is sparingly soluble in cold water, but its solubility increases considerably in hot water -- broadly the same temperature-dependent solubility pattern already noted for potassium dichromate (section 4.4.2.2), and one that similarly underlies standard laboratory practice: KMnO₄ solutions used as titrants in volumetric analysis are typically prepared and dissolved using hot water to ensure the requ …