Permanganic acid (HMnO4), potassium salt.
Potassium permanganate (KMnO4) [7722-64-7].
» Potassium Permanganate contains not less than 99.0 percent and not more than 100.5 percent of KMnO4, calculated on the dried basis.
Caution: Observe great care in handling Potassium Permanganate, as dangerous explosions may occur if it is brought into contact with organic or other readily oxidizable substances, either in solution or in the dry state.
Packaging and storage Preserve in well-closed containers.
Identification A solution of it is deep violet-red when concentrated and pink when highly diluted, and responds to the tests for Permanganate 191.
Loss on drying 731 Dry it over silica gel for 18 hours: it loses not more than 0.5% of its weight.
Insoluble substances Dissolve 2.0 g in 150 mL of water that previously has been warmed to steam-bath temperature, and filter immediately through a tared, medium-porosity filtering crucible. Wash the filter with three 50-mL portions of the warm water, and dry the filtering crucible and the residue at 105 for 3 hours: not more than 4 mg of residue is obtained (0.2%).
Assay Transfer about 1000 mg of Potassium Permanganate, accurately weighed, and for each mg of Potassium Permanganate taken, 2.13 mg of sodium oxalate, previously dried at 110 to constant weight and accurately weighed, to a 500-mL conical flask. Add 150 mL of water and 20 mL of 7 N sulfuric acid, heat to about 80, and titrate the excess oxalic acid with 0.03 N potassium permanganate VS. Calculate the quantity, in mg, of KMnO4 in the portion of Potassium Permanganate taken by the formula:
0.4718WS 0.9482Vin which 0.4718 is the KMnO4 equivalent, in mg, of each mg of sodium oxalate, WS is the weight, in mg, of sodium oxalate taken, 0.9482 is the quantity of KMnO4, in mg, in each mL of 0.03 N potassium permanganate, and V is the volume, in mL, of 0.03 N potassium permanganate consumed.