Potassium permanganate

CAS number : 7722-64-7

Molecular weight :158.03

Molecular formula/chemical symbol :KMnO4

Description :

Potassium permanganate is an inorganic chemical compound with the formula KMnO₄. It is a salt consisting of K⁺ and MnO₄^? ions. Formerly known as permanganate of potash or Condy‘s crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the evaporation of which leaves prismatic purplish-black glistening crystals.

Potassium permanganate is produced industrially from manganese dioxide, which also occurs as the mineral pyrolusite. The MnO₂ is fused with potassium hydroxide and heated in air or with a source of oxygen, like potassium nitrate or chlorate. This process gives potassium manganate, which upon electrolytic oxidation in alkaline media, or by boiling the manganate solution in the presence of carbon dioxide until all the green color is discharged, gives potassium permanganate.

2 MnO₂ + 4 KOH + O₂ → 2 K₂MnO₄ + 2 H₂O

2 MnO₄^2– + Cl₂ → 2 MnO₄^– + 2 Cl^–

or:

3 K₂MnO₄ + 2 CO₂ → 2 KMnO₄ + 2 K₂CO₃ + MnO₂

In which the potassium permanganate is separated by filtering the insoluble manganese dioxide, evaporating the solution to 1/3 and recrystallizing it.

Permanganate salts can also be generated by treating a solution of Mn²⁺ ions with strong oxidants such as lead dioxide (PbO₂), or sodium bismuthate (NaBiO₃). Tests for the presence of manganese exploit the vivid violet color of permanganate produced by these reagents.

KMnO₄ forms orthorhombic crystals with constants: a = 910.5 pm, b = 572.0 pm, c = 742.5 pm. The overall motif is similar to that for barium sulfate, with which it forms solid solutions. In the solid (as in solution), each MnO₄^- centres are tetrahedral. The Mn-O distances are 1.62 ?.

Potassium permanganate
IUPAC name Potassium manganate(VII)
Other names Potassium permanganate Potassium manganate(VII) Chameleon mineral Condy‘s crystals Permanganate of potash
Identifiers
CAS number	7722-64-7 Y
PubChem	516875
ChemSpider	22810 Y
EC number	231-760-3
UN number	1490
KEGG	D02053 Y
RTECS number	SD6475000
ATC code	D08AX06,V03AB18
Jmol-3D images	Image 1
SMILES ·                                 [K+].[O-][Mn](=O)(=O)=O
InChI ·                                 InChI=1S/K.Mn.4O/q+1;;;;;-1 Y Key: VZJVWSHVAAUDKD-UHFFFAOYSA-N Y
Properties
Molecular formula	KMnO4
Molar mass	158.034 g/mol
Appearance	purplish-bronze-gray needles magenta–rose in solution
Odor	odorless
Density	2.703 g/cm3
Melting point	240 °C, 513 K, 464 °F (decomp.)
Solubility in water	6.38 g/100 mL (20 °C) 25 g/100 mL (65 °C)
Solubility	decomposes in alcohol and organic solvents
Refractive index (nD)	1.59
Structure
Crystal structure	Orthorhombic
Thermochemistry
Std enthalpy of formation ΔfHo298	?813.4 kJ/mol
Standard molar entropy So298	171.7 J K–1 mol–1
Hazards
MSDS	External MSDS
EU Index	025-002-00-9
EU classification	Oxidant (O) Harmful (Xn) Dangerous for the environment (N) Non-Flammable
R-phrases	R8, R22, R50/53
S-phrases	(S2), S60, S61
Related compounds
Other anions	Potassium manganite Potassium manganate
Other cations	Sodium permanganate Ammonium permanganate
Related compounds	Manganese heptoxide
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

USES :

The capacity of the oxidation-reduction method determination reagent.

Chromatography analysis of the reagents used. For emission spectrometric analysis.

Spot analysis of barium, silver, sulfate, iron, vanadium and tin, clinical shedding cell inspection.