3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||119.94 g mol-1|
|Main hazards||Oxidant, Corrosive|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Permanganic acid (or manganic(VII) acid) is the inorganic compound with the formula HMnO4. This strong oxoacid has been isolated as its dihydrate. It is the conjugate acid of permanganate salts. It is the subject of few publications and its characterization as well as its uses are very limited.
Permanganic acid has also been prepared through the reaction of hydrofluorosilicic acid with potassium permanganate, through electrolysis, and through hydrolysis of manganese heptoxide, though the last route often results in explosions.
Crystalline permanganic acid has been prepared at low temperatures as the dihydrate, HMnO4·2H2O.
Although its structure has not been verified spectroscopically or crystallographically, HMnO4 is assumed to be adopt a tetrahedral structure akin to that for perchloric acid.
Permanganic acid solutions are unstable, and gradually decompose into manganese dioxide, oxygen, and water, with initially formed manganese dioxide catalyzing further decomposition. Decomposition is accelerated by heat, light, and acids. Concentrated solutions decompose more rapidly than dilute.