Ammonium permanganate

Ammonium permanganate

Names
IUPAC name Ammonium manganate(VII)
Other names Azanium permanganate Permanganic acid, ammonium salt
Properties
Chemical formula	NH4MnO4
Molar mass	136.974 g/mol
Appearance	Violet-brown or dark purple metallic crystals
Odor	Odorless (fresh) Nitrogen oxide-like (old)
Density	2.200 g/cm3 (at 20 °C)
Melting point	Decomposes violently above 60 °C
Boiling point	Explodes
Solubility in water	8.0 g/100 ml (at 15 °C) 8.57594 g/100 ml (at 25 °C)
Solubility	Insoluble in acetone
Thermochemistry
Std enthalpy of formation (ΔfHo298)	-703.171 - -686.429 kJ/mol
Hazards
Safety data sheet	Chemexper.net
Related compounds
Related compounds	Permanganic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ammonium permanganate is an energetic chemical compound with the chemical formula NH₄MnO₄. It is a strong oxidizer as well as a moderately strong explosive.

Properties

Chemical

Ammonium permanganate decomposes explosively, releasing nitrogen, water vapors and a copious cloud of dark brownish manganese dioxide dust.

NH₄MnO₄ → MnO₂ + ½ N₂ + H₂O

Physical

Ammonium permanganate is a violet-brown or dark purple metallic crystalline or powder, which slowly turns steel-gray over time. Aqueous solutions are magenta–rose in color. It is slightly soluble in water and insoluble in acetone. The density of NH₄MnO₄ is given different values in literature, with the most recent measurement being 2.2 g/cm³ at 20 °C.

Explosive

Ammonium permanganate is a moderately strong explosive, due to the combination of oxidizer permanganate anion and reducing ammonium cation. Dry ammonium permanganate in sensitive to heat, shock and friction, and may explode at temperatures above 60 °C (110 °C according to Crespi). Its oxygen balance is zero.

Availability

Ammonium permanganate is not sold by any entities due to its sensitivity and has to be prepared in situ.

Preparation

Ammonium permanganate can be prepared through several ways.

The best involves the reaction of silver permanganate and ammonium chloride in water. Silver chloride precipitates and is removed via filtration. The aqueous ammonium permanganate solution is concentrated by evaporating the water in vacuum and then cooled to precipitate NH₄MnO₄ crystals.

The same process can be used for the reaction of barium permanganate and ammonium sulfate.

Another way is to mix a concentrated solution of ammonium chlorate/perchlorate with another of sodium permanganate. Sodium chlorate/perchlorate will remain in the solution due to its high solubility, while ammonium permanganate will precipitate due to its low solubility in water. The solution is filtered and the precipitate is washed thoroughly to remove any chlorate/perchlorate traces.

Projects

• Make bang snaps
• Make very fine MnO₂ powder

Handling

Safety

Ammonium permanganate is corrosive to skin, eyes, mouth and lungs, and contact will stain them brown, casing burns.

Being a strong oxidizer, avoid contact with flammable materials. As it's explosive, proper protection must be worn when handling it. It is sensitive to heat, friction and shock.

Storage

Ammonium permanganate should only be stored for short periods of time, in a cool dark place away from light and organic materials and must be used as soon as possible.

Ammonium permanganate decomposes slowly in storage even at room temperatures. A sample stored for 3 months was only 96% pure and after 6 months it assumed color of iodine and had strong smell of nitrogen oxides.

Disposal

Ammonium permanganate can be neutralized by dissolving it in water and adding a reducing agent such as sodium metabisulfite, sodium sulfite, sodium thiosulfate, sulfur dioxide, which converts it into ammonium sulfate and manganese(II) sulfate.

Detonation of NH₄MnO₄ will give a fine, irritant and corrosive manganese dioxide mist.

References

Relevant Sciencemadness threads

• Ammonium permanganate preparation