Potassium permanganate: Wikis

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Potassium permanganate
Potassium-permanganate-2004-unit-cell-3D-balls.png
Potassium-permanganate-sample.jpg
IUPAC name
Other names Potassium permanganate
Potassium manganate(VII)
Chameleon mineral
Condy's crystals
Permanganate of potash
Identifiers
CAS number 7722-64-7 Yes check.svgY
PubChem 24400
EC number 231-760-3
UN number 1490
KEGG D02053
RTECS number SD6475000
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 decomp.

Solubility in water 6.38 g/100 ml (20 °C)
25 g/100 mL (65 °C)
Solubility decomposes in alcohol and organic solvents
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)
R-phrases R8, R22, R50/53
S-phrases (S2), S60, S61
NFPA 704
NFPA 704.svg
0
3
3
OX
Related compounds
Other anions Potassium manganite
Potassium manganate
Other cations Sodium permanganate
Ammonium permanganate
Related compounds Manganese heptoxide
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Potassium permanganate is the 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 intense purple solutions, the evaporation of which gives prismatic purplish-black glistening crystals.[1]

In 2000, worldwide production was estimated at 30 000 tonnes.[2] In this compound, manganese is in the +7 oxidation state.

Contents

Structure

It forms orthorhombic crystals with constants: a = 910.5 pm, b = 572.0 pm, c = 742.5 pm. The Mn-O bond distances are 162.9 pm.

Preparation

Potassium permanganate is manufactured on a large scale from manganese dioxide. The mineral pyrolusite is fused with potassium hydroxide and heated in air or with potassium nitrate (a source of oxygen). This process gives potassium manganate, which upon electrolytic oxidation in alkaline solution gives potassium permanganate.

2 MnO2 + 4 KOH + O2 → 2 K2MnO4 + 2 H2O
2 MnO42- + Cl2 → 2 MnO4- + 2 Cl-

Permanganates can also be generated by treating a solution of Mn2+ ions with strong oxidants such as lead dioxide (PbO2), or sodium bismuthate (NaBiO3). These reactions use the vivid violet colour of permanganate as a test for the presence of manganese.

Uses

Almost all applications of potassium permanganate exploit its oxidizing properties.[2] As a strong oxidant that does not generate toxic byproducts, KMnO4 has many niche uses.

Potassium permanganate is one of the principle chemicals utilised in the film and television industries to "age" props and set dressings. Its oxidising effects create "hundred year old" or "ancient" looks on hessian cloth, ropes, timber and glass.[3] It was used on props and sets in films such as "Troy", "300" and "Indiana Jones".

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Disinfectant and water treatment

As an oxidant, potassium permanganate can act as a disinfectant. For example, dilute solutions are used to treat canker sores (ulcers), disinfectant for the hands and treatment for mild pompholyx, dermatitis,[4][5] and fungal infections of the hands or feet.[6] Potassium permanganate, obtainable at pool supply stores, is used in rural areas to remove iron and hydrogen sulfide (rotten egg smell) from well and waste water. Historically it was used to disinfect drinking water.[7]

Biomedical uses

Related to the use of KMnO4 for water treatment, this salt is often employed as a specialized disinfectant for treating human and animal ailments. In histology, it is used to bleach melanin which obscures tissue detail. Potassium permanganate can also be used to differentiate amyloid AA from other types of amyloid pathologically deposited in body tissues. Incubation of fixed tissue with potassium permanganate will prevent amyloid AA from staining with congo red whereas other types of amyloid are unaffected.[8][9] Permanganate washes were once used to treat gonorrhea and are still used to treat candidiasis.[10]

Organic synthesis

Aside from its use in water treatment, the other major application of KMnO4 is as a reagent for the synthesis of organic compounds.[11] Significant amounts are required for the synthesis of ascorbic acid, chloramphenicol, saccharine, isonicotinic acid, and pyrazinoic acid.[2]

Chemistry

Analytical

Potassium permanganate can be used to quantitatively determine the total oxidisable organic material in an aqueous sample. The value determined is known as the permanganate value. In analytical chemistry, a standardized aqueous solution of KMnO4 is sometimes used as an oxidizing titrant for redox titrations. In a related way, it is used as a reagent to determine the Kappa number of wood pulp. For the standardization of KMnO4 solutions, reduction by oxalic acid [12] is often used.

A solution of KMnO4 in water, in a volumetric flask

Aqueous, acidic solutions of KMnO4 are used to collect gaseous mercury in flue gas during stationary source emissions testing.[13]

Organic

Dilute solutions of KMnO4 convert alkenes into diols (glycols). This behaviour is also used as a qualitative test for the presence of double or triple bonds in a molecule, since the reaction decolourises the permanganate solution; thus it is sometimes referred to as Baeyer's reagent. However, bromine serves better in measuring unsaturation (double or triple bonds) quantitatively, since KMnO4, being a very strong oxidizing agent, can react with impurities in a sample.

Under acidic conditions, the alkene double bond is cleaved to give the appropriate carboxylic acid:[14]

CH3(CH2)17CH=CH2 + [O] → CH3(CH2)17COOH

Potassium permanganate oxidizes aldehydes to carboxylic acids, such as the conversion of n-heptanal to heptanoic acid:[15]

C6H13CHO + [O] → C6H13COOH

Even an alkyl group (with a benzylic hydrogen) on an aromatic ring is oxidized, e.g. toluene to benzoic acid.[16]

Glycols are highly reactive toward KMnO4. This vigorous reaction is used in survival kits as a fire starter. For example, a mixture of potassium permanganate and glycerol or pulverized glucose ignites readily. Its sterilizing properties are another reason for inclusion of KMnO4 in a survival kit.[17]

Reaction with acids

Concentrated sulfuric acid reacts with KMnO4 to give Mn2O7, which can be explosive.[18][19][20] Similarly concentrated hydrochloric acid gives chlorine. The Mn-containing products from redox reactions depend on the pH. Acidic solutions of permanganate are reduced to the faintly pink manganese(II) ion (Mn2+) and water. In neutral solution, permanganate is only reduced by 3e to give MnO2, wherein Mn is in a +4 oxidation state. This is the material that stains one's skin when handling KMnO4. KMnO4 spontaneously reduces in an alkaline solution to green K2MnO4, wherein manganese is in the +6 oxidation state. Potassium permanganate and sulfuric acid react to produce some ozone, which has a high oxidising power and rapidly oxidises the alcohol, causing it to combust. As a similar reaction produces explosive Mn2O7, this should only be attempted with great care. An approximate equation for the ozone formation is shown below.

6 KMnO4 (aq) + 9 H2SO4 (aq) → 6 MnSO4 (aq) + 3 K2SO4 (aq) + 9 H2O (l) + 5 O3 (g)

Handling

As an oxidizer that generates the dark brown product MnO2, potassium permanganate rapidly stains virtually any organic material such as skin, paper, and clothing. This staining effect is used to "develop" TLC plates. The redox reaction is used for artistic purposes as an agent to prepare paper for fast bleaching. Lemon juice is enough to quickly remove colour from the paper and applied with a paint brush this can create interesting aesthetics. Even glassware containing solutions of KMnO4 can become brown. MnO2 can be removed by scrubbing with dilute acids.

History

In 1659 a German chemist, J.R. Glauber, fused a mixture of the mineral pyrolusite and potassium carbonate to obtain a material that, when dissolved in water, gave a green solution (potassium manganate) which slowly shifted to violet potassium permanganate and then finally red. This report represents the first description of the production of potassium permanganate.[21] Just under two hundred years later London chemist Henry Bollmann Condy had an interest in disinfectants, and marketed several products including ozonised water. He found that fusing pyrolusite with NaOH and dissolving it in water produced a solution with disinfectant properties. He patented this solution, and marketed it as Condy's Fluid. Although effective, the solution was not very stable. This was overcome by using KOH rather than NaOH. This was more stable, and had the advantage of easy conversion to the equally effective potassium permanganate crystals. This crystalline material was known as Condy’s crystals or Condy’s powder. Potassium permanganate was comparatively easy to manufacture so Condy was subsequently forced to spend considerable time in litigation in order to stop competitors from marketing products similar to Condy's Fluid or Condy's Crystals.

Early photographers used it as a component of flash powder. It is now replaced with other oxidizers, due to the instability of permanganate mixtures. Aqueous solutions of KMnO4 have been used together with T-Stoff (i.e. 80% hydrogen peroxide) as propellant for the rocket plane Messerschmitt Me 163. In this application, it was known as Z-Stoff. This combination of propellants is sometimes still used in torpedoes.

Safety

Solid KMnO4 is a strong oxidizer and thus should be kept separated from oxidizable substances. Reaction with concentrated sulfuric acid produces the highly explosive manganese(VII) oxide (Mn2O7). When solid KMnO4 is mixed with pure glycerol it will result in a violent combustion reaction.

References

  1. ^ F. Burriel, F. Lucena, S. Arribas and J. Hernández, (1985), Química Analítica Cualitativa, page 688, ISBN 84-9732-140-5.
  2. ^ a b c Arno H. Reidies "Manganese Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a16_123
  3. ^ Ester Brody (February 2000). "Victor DeLor contractor profile". PaintPRO 2 (1). http://www.paintpro.net/Articles/PP201/PP201-Contractor_Profile.cfm. Retrieved 2009-11-12. "One of the techniques DeLor is known for among designers and clients is the special effects he creates with various chemical solutions. When applied to wood surfaces, these chemicals give a weathered appearance to new wood. ... To achieve the aesthetic on interior surfaces, DeLor often uses a mixture of water and potassium permanganate, a dry powder chemical.".  
  4. ^ BIRT AR (March 1964). "Drugs for eczema of children". Can Med Assoc J 90 (11): 693–4. PMID 14127384.  
  5. ^ Stalder JF, Fleury M, Sourisse M, et al. (1992). "Comparative effects of two topical antiseptics (chlorhexidine vs KMn04) on bacterial skin flora in atopic dermatitis". Acta Derm Venereol Suppl (Stockh) 176: 132–4. PMID 1476027.  
  6. ^ "Skin diseases". Health Technol Dir 8 (3): 1–10. 1988. PMID 12282068.  
  7. ^ . p. 98. ISBN 9780309029315. http://books.google.de/books?id=uVlQ_TUP-f0C&pg=PA98I.  
  8. ^ Wright, J. R.; Calkins E.; Humphrey R. L. (1977). "Potassium permanganate reaction in amyloidosis. A histologic method to assist in differentiating forms of this disease". Lab Invest. 36 (3): 274–81. PMID 839739.  
  9. ^ van Rijswijk, M. H.; van Heusden, C. W. (1979). "The potassium permanganate method. A reliable method for differentiating amyloid AA from other forms of amyloid in routine laboratory practice". Am J Pathol. 97 (1): 43–58. PMID 495695.  
  10. ^ Haseltine, Florence; Yvonne Yaw (1976). "Private Medicine". Woman Doctor: the Internship of a Modern Woman (Book Club ed.). Houghton Mifflin. p. 32.  
  11. ^ A. Fatiadi (1987). "The Classical Permanganate Ion: Still a Novel Oxidant in Organic Chemistry" (review). Synthesis 1987 (2): 85–127. doi:10.1055/s-1987-27859.  
  12. ^ Kovacs KA, Grof P, Burai L, Riedel M (2004). "Revising the Mechanism of the Permanganate/Oxalate Reaction". J. Phys. Chem. A 108: 11026. doi:10.1021/jp047061u.  
  13. ^ Code of Federal Regulations(7-1-07) Edition,Title 40, Part 60, Appendix A-8, Method 29, Section 7.3.1
  14. ^ Donald G. Lee, Shannon E. Lamb, and Victor S. Chang (1990), "Carboxylic Acids from the Oxidation of Terminal Alkenes by Permanganate: Nonadecanoic Acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv7p0397  ; Coll. Vol. 7: 397  
  15. ^ John R. Ruhoff, "n-Heptanoic acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p0315  ; Coll. Vol. 2: 315  
  16. ^ Gardner KA, Mayer JM (1995). "Understanding C-H Bond Oxidations: H· and H- Transfer in the Oxidation of Toluene by Permanganate". Science 269: 1849. doi:10.1126/science.7569922.  
  17. ^ Bob Gillis and Dino Labiste. "Chemical Fire". http://www.primitiveways.com/chemical_fire.html.  
  18. ^ F. A. Cotton, G. Wilkinson, C. A. Murillo, and M. Bochmann (April 1999). Advanced Inorganic Chemistry, 6th Edition. Wiley-VCH. ISBN 0-471-19957-5
  19. ^ Barthel, H. and Duvinage, B. (2000). "Clemens Winkler. His Experiments with Ozone in 1892". Praxis der Naturwissenschaften, Chemie 49: 18ff.  
  20. ^ Dzhabiev, T. S.; Denisov, N. N.; Moiseev, D. N. and Shilov, A. E. (2005). "Formation of Ozone During the Reduction of Potassium Permanganate in Sulfuric Acid Solutions". Russian Journal of Physical Chemistry 79: 1755–1760.  
  21. ^ Weeks, M. E. and Leicester, H. M.; Discovery of the Elements, Journal of Chemical Education 1968

External links


Simple English

Potassium permanganate
General
Other names Potassium manganate(VII)
Molecular formula KMnO4
Molar mass 158.04 g/mol
Appearance black crystals;

bright purple in solution

CAS number [7722-64-7]
Properties
Density and phase 2.703 g/cm³, solid
Solubility in water 6.38 g/100 ml (20 °C)
Melting point 270 °C decomp.
Thermodynamic data
Standard enthalpy
of formation ΔfH°solid
−813.4 kJ/mol
Standard molar entropy
S°solid
171.7 J.K−1.mol−1
Hazards
EU classification Oxidant (O)
Harmful (Xn)
Dangerous for
the environment (N)
NFPA 704

0
1
0
OX
Related compounds
Other anions Potassium hypomanganate
Other cations Sodium permanganate
Related compounds Potassium manganate
Manganese heptoxide
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
See Wikipedia:Disclaimer.

Potassium permanganate is a chemical compound. Its chemical formula is KMnO4. It contains potassium and permanganate ions. The manganese is in the +7 oxidation state. It is also known as permanganate of potash and Condy's crystals. Potassium permanganate is a strong oxidizing agent, which means it has a tendency to take electrons from other chemicals. It dissolves in water to give purple solutions. If it is evaporated, it makes purple-black shiny crystals.[2] It has a sweet taste and is odorless. [1]

Contents

History

In 1659 a German chemist, J.R. Glauber, melted a mixture of the mineral pyrolusite and potassium carbonate to obtain a material that made a green solution (potassium manganate) when dissolved in water. It slowly changed colour to violet (potassium permanganate) and then finally red. This report is the first description of the production of potassium permanganate.

Just under 200 years later a Londoner named Henry Bollmann Condy was a chemist. He had an interest in disinfectants and made some things like ozonised water. He found that when he melted pyrolusite with sodium hydroxide and dissolved it in water, it made a solution that had good disinfectant properties. He patented this solution, and sold it as Condy's Fluid. The problem was that the solution was not very stable. This was fixed by using potassium hydroxide rather than sodium hydroxide. This gave a more stable material. It also was able to be dried to the just as good potassium permanganate powder. This powder was called Condy’s crystals or Condy’s powder. Potassium permanganate was easy to make so Condy tried to stop other people from making it and selling it themselves.

Early photographers used it in flash powder.

Uses

Chemical applications

Potassium permanganate is used as an oxidizing agent.[3] It also is used in disinfectants and in deodorizers. It can be used to make many different kinds of chemicals. In waste water treatment, it is used to get rid of hydrogen sulfide, a stinky toxic gas. In analytical chemistry, an accurate concentration of KMnO4 is sometimes used to see how much of a certain reducing agent is in the titration. In a related way, it is used as a reagent for wood pulp. Mixing potassium permanganate and formaldehyde makes a mild tear gas.

As an oxidant in organic synthesis

Dilute solutions of KMnO4 convert alkenes into diols (glycols). This behaviour is also used as a qualitative test for the presence of double or triple bonds in a molecule, since the reaction makes the permanganate solution colorless. It is sometimes referred to as Baeyer's reagent.

Concentrated solutions oxidize a methyl group on an aromatic ring, e.g. toluene to benzoic acid.

KMnO4 oxidizes pseudoephedrine hydrochloride to produce methcathinone, a Schedule I drug in the United States. Consequently the DEA has restricted its use and sale by classifying it as a List I controlled precursor. Potassium permanganate is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.[2]

Acids and Potassium Permanganate

Concentrated sulfuric acid reacts with potassium permanganate to give manganese(VII) oxide, which can be explosive. [4][5][6]. This reaction also makes ozone. The ozone can ignite paper soaked in alcohol. This reaction is very dangerous.

6 KMnO4 + 9 H2SO4 → 6 MnSO4 + 3 K2SO4 + 9 H2O + 5 O3

Concentrated HCl makes chlorine.

2 KMnO4 + 16 HCl → 2 MnCl2 + 2 KCl + 8 H2O + 5 Cl2

The Mn-containing products from redox reactions depend on the pH. Acidic solutions of permanganate are reduced to the faintly pink Mn2+ ion, as in manganese(II) chloride. In neutral solution, permanganate is reduced to brown manganese(IV) oxide, where Mn is in a +4 oxidation state. Manganese(IV) oxide is the stuff that stains skin when potassium permanganate is put on it. Potassium permanganate spontaneously reduces in an basic solution to green-coloured potassium manganate, where manganese is in the +6 oxidation state.

Biomedical uses

  • Dilute solutions are used as a treatment for canker sores (ulcers) (0.25%), disinfectant for the hands (about 1%) and treatment for mild pompholyx dermatitis or fungal infections of the hands or feet.
  • A dilute solution of acidified potassium permanganate is used in histology to bleach melanin which obscures tissue detail.
  • Potassium permanganate can be used to differentiate amyloid AA from other types of amyloid pathologically deposited in body tissues. Incubation of fixed tissue with potassium permanganate will prevent amyloid AA from staining with congo red whereas other types of amyloid are unaffected.[7][8]

Miscellaneous uses

  • Solutions of KMnO4 have been used together with 80 % [[hydrogen peroxide to propel a rocket. In this use, it was called Z-Stoff. This propellant is still used in torpedoes.
  • A dilute (10mg/l) of potassium permanganate can be used to eliminate snails from plants prior to placing them in a fresh-water aquarium.
  • High-grade potassium permanganate can be found at pool supply stores and is used in rural areas to remove iron and hydrogen sulfide (rotten egg smell) from well water.
  • KMnO4 is often included in survival kits along with either glycerine or a glucose tablet for the purposes of making fire. The glucose tablet can be ground up, mixed with the potassium permanganate and caused to combust by applying friction. It can also be mixed with anti-freeze from a vehicle to produce flame, although this can be dangerous and should be done in a controlled manner ie dipping some paper into the anti-freeze and then adding a small amount of potassium permanganate. The ability to sterilize water and wounds is also advantageous and another reason for inclusion in a survival kit.
  • KMnO4 is employed to treat some parasitic diseases of fish, in treatment of drinking water, as well as an antidote in phosphorus poisoning. In Africa, it has been used as a disinfectant for vegetables such as lettuce.

Hazards

Solid potassium permanganate is a strong oxidizer and in general it should be kept separated from reducing agents. Some reactions need a bit of water. For example, powdered potassium permanganate and powdered sugar will ignite (but not explode) a few seconds after a drop of water is added. Dilute solutions of KMnO4 are not dangerous. KMnO4 forms dangerous products when mixed with concentrated acids.

Potassium permanganate stains skin and clothing and should be handled with care. Clothing stains may be washed away using acetic acid. Skin stains disappear within 48 hours.

References

  1. ^ F. Burriel, F. Lucena, S. Arribas and J. Hernández, (1985), Química Analítica Cualitativa, page 688, ISBN 84-9732-140-5.
  2. ^  Fatiadi, A. J. Synthesis 1987, 85-127. (Review) (doi:10.1055/s-1987-27859)
  3. ^  F. A. Cotton, G. Wilkinson, C. A. Murillo, and M. Bochmann (April 1999). Advanced Inorganic Chemistry, 6th Edition. Wiley-VCH. ISBN 0-471-19957-5
  4. ^  van Rijswijk MH, van Heusden CW.American Journal of Pathology.1979Oct;97(1):43-58. PMID: 495695
  5. ^ Dzhabiev, T. S.; Denisov, N. N.; Moiseev, D. N. and Shilov, A. E., "Formation of Ozone During the Reduction of Potassium Permanganate in Sulfuric Acid Solutions", Russian Journal of Physical Chemistry, 2005, volume 79, pages 1755-1760.
  6. ^ Barthel, H. and Duvinage, B., "Clemens Winkler. His Experiments with Ozone in 1892", Praxis der Naturwissenschaften, Chemie, 2000, volume 49, page 18ff.
  7. ^ Wright JR, Calkins E, Humphrey RL.Laboratory Investigation. 1977 Mar;36(3):274-81. PMID: 839739
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