Barium permanganate is a chemical compound, with the formula Ba(MnO
4)
2. It forms violet to brown crystals that are sparingly soluble in water.
Preparation
Barium permanganate may be produced by
disproportionation
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. More generally, the term can ...
of
barium manganate
Barium manganate is an inorganic compound with the formula BaMnO4. It is used as an oxidant in organic chemistry. It belongs to a class of compounds known as manganates in which the manganese resides in a +6 oxidation state. Manganate should not ...
in a mildly acidic solution,
including solutions
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
or
sulfuric acid:
:3 BaMnO
4 + 2 CO
2 → Ba(MnO
4)
2 + 2 BaCO
3 + MnO
2
:3 BaMnO
4 + 2 H
2SO
4 → Ba(MnO
4)
2 + 2 BaSO
4 + MnO
2 + 2 H
2O
It can also be prepared by oxidation of barium manganate with strong oxidants. Preparations relying on aqueous reactions of barium manganate are extremely slow process due to the low solubility of the manganate.
Another way to synthesize barium permanganate is by the reaction between silver permanganate and barium chloride. Highly pure samples can be obtained from the similar reaction between
potassium permanganate
Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution.
Potassium permanganate is widely used in the c ...
and
aluminium sulfate to form
aluminium permanganate, which is then reacted with a stoichiometric amount of
barium hydroxide
Barium hydroxide is a chemical compound with the chemical formula Ba(OH)2. The monohydrate (''x'' = 1), known as baryta or baryta-water, is one of the principal compounds of barium. This white granular monohydrate is the usual commercial form.
...
.
Reactions
Barium permanganate is a strong oxidizer. It is thermally stable up to 180 °C, above which it decomposes in two stages between 180–350 and 500–700 °C.
:2 Ba(MnO
4)
2 → 2 BaMnO
3 + 2 MnO
2 + 3 O
2
:4 BaMnO
3 → 4 BaO + 2 Mn
2O
3 + O
2
The decomposition has been shown to proceed at slow rates above 160 °C, and that irradiation with UV or X-rays lowers this temperature.
Crystal defects and impurities play a role in the mechanism.
Permanganic acid
Permanganic acid (or manganic(VII) acid) is the inorganic compound with the formula H MnO4. 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 c ...
can be prepared by the reaction of dilute
sulfuric acid with a solution barium permanganate, the insoluble
barium sulfate byproduct being removed by filtering:
:Ba(MnO
4)
2 + H
2SO
4 → 2 HMnO
4 + BaSO
4
The sulfuric acid used must be dilute; reactions of permanganates with concentrated sulfuric acid yield the
anhydride
An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the pa ...
,
manganese heptoxide.
References
Barium compounds
Permanganates
{{inorganic-compound-stub