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Potassium Permanganate, a potent and very useful oxidizer

Updated on March 17, 2016
Potassium Permanganate
Potassium Permanganate | Source

Description

Potassium permanganate is a violet crystalline solid with a bronze tinge. It contains manganese in the +7 oxidation state. It is a powerful oxidant and contamination of the solid with organics and combustibles can lead to spontaneous ignition or even explosion. Not to mention that the chemical is toxic and caustic to human tissue. It leaves dark brown stains on skin that are difficult to remove. Great care must be exercised when performing reactions involving potassium permanganate.

Potassium permanganate is an inorganic ionic salt that is soluble in water. The solubility varies with temperature. Attempts to purify this compound by crystallization from water must not be heated above 60 degrees Centigrade. Above that temperature, the salt is likely to decompose. Below is a table with water solubility from 0ºC, 30ºC, and 60ºC for reference purposes.

Below is the list of contents for the rest of this article. In this article, several of the key chemical properties of potassium permangante will be elaborated on.

  1. Solubility of Potassium Permanganate
  2. Safety Warning
  3. Potassium Permanganate and Glycerine Reaction
  4. Oxidation of Halides
  5. Chlorine Generator using Permanganate
  6. Removing Iron from your water
  7. Antiseptic and Sterilizer
  8. Permangante the Chameleon Mineral
  9. Color Change Chameleon
  10. Reagent in Organic Synthesis
  11. Potassium Permangante Makes Fire!

Solubility of Potassium Permanganate in Water at Various Temperatures

0ºC
30ºC
60ºC
2.83
9.03
22.1
 
 
 
 
 
 
Solubility of potassium permanganate in water at various temperatures. Values are given in grams per 100 grams of water at 1 atmosphere of pressure.

Safety First!

Although potassium permanganate is a colorful and useful chemical it can be very dangerous if misused. Potassium permanganate is a powerful and unstable oxidant. It is also toxic and caustic to human tissue.

The oxidizing properties of potassium permanganate present a special reactivity hazard. Many chemical products interact with potassium permanganate to generate toxic gasses, great amounts of heat, and even fire and explosions. With halogen acids like hydrochloric and hydrobromic acids, toxic and corrosive chlorine and bromine are produced. Mixtures of potassium permanganate with glycerine and other glycols generate a chain reaction that leads to spontaneous ignition. This is call a hypergolic reaction. Potassium permanganate is caustic and burns skin and leaves brownish stains on skin. This substance must be kept out of eyes at all cost.

Proper safety gear includes gloves, chemical goggles or face shield, and apron to protect clothing. Potassium permanganate must be kept away from sources of ignition and combustible materials. This also includes materials not considered combustible but forming hypergolic mixtures such as glycerine,break fluid, or other products that may be glycol based.

Potassium Permanganate and Glycerine Reaction

Oxidation of halides

When acidified potassium permanganate oxidizes chloride, bromide and iodide to the free halogen and reducing the manganese to the +2 oxidation state. When hydrochloric acid is the acidulant, copious amounts of chlorine gas is evolved. Another useful reaction is to acidulate potassium permanganate solution with dilute sulfuric acid then add to a bromide such as potassium bromide. The free element of bromine is liberated.

Chlorine Generator Using Permanganate

Chlorine Gas Generator Using Permanganate.  This chlorine in this set up is used for making chlorate.
Chlorine Gas Generator Using Permanganate. This chlorine in this set up is used for making chlorate. | Source

Removing iron from your water

Potassium permanganate is very useful for oxidizing dissolved iron in water supples into insoluble iron oxide which can easily removed by filtration. This improves the taste of drinking water.

Antiseptic and sterlizer

The oxidative properties of permanganate makingit a useful antiseptic. In it used to treat various skin conditions like athletes foot. It is also useful for sterlizing surfaces used in food preparation to prevent the spread of cholera. This same property makes potassium permanganate sought after by survivalists and outdoors enthusiast for purifying water by killing harmful microbes.

Permanganate The Chameleon Mineral

Potassium permanganate is a chemical compound of a transistion metal called manganese. A transition metal is just a fancy technical way of saying an element can bond to varying proportions of other elements through changes in electrical charge. This is accomplished by either oxidation or reduction. Potassium permanganate, like many other transition metal compounds is intensely colored. Manganese has various charge states and most are vividly colored. The video shows a fascinating color change when a solution of potassium permanganate is added to a stirred solution of sodium hydroxide(lye) and sucrose(table sugar).

Colour Change Chameleon

Reagent in Organic synthesis

A dilute solution of potassium permanganate can convert alkene( hydrocarbons with double bonds) into glycols which will decolorize the pink solution. This reaction is also used in analytical chemistry to determine the presence of double bonds in a sample.

When acidified, the permanganate cleaves the double bond forming carboxylic acids.

CH3(CH2)17CH=CH2 + 2 KMnO4 + 3 H2SO4 → CH3(CH2)17COOH + CO2 + 4 H2O + K2SO4 + 2 MnSO4

Potassium permangante is also useful in oxidizing alcohols and aldheydes into there corresponding carboxylic acids. Aromatic hydrocarbons with side chains like toluene are oxidized. Toluene is converted into benzoic acid.

Permanganate is very reactive towards glycols and carbonhydrates. When a small pile of permanganate is mooistened with glycerol, there is spontaneous vigorous ignition after a bried delay. Simular results are witnessed with sugar.

Potassium permanganate make fire!

Potassium Permanganate

As already mentioned, potassium permanganate enters a self sustaining pyrotechnical reaction with glycerine simply by mixing and waiting. This property is also notable with other poly glycols such as ethylene and propylene glycols. The reaction with simple alcohols is even faster and may present a dangerous explosion hazard. Should be noted that sensitive and unpredictable mixtures with sulfur, phosphorus, and powdered metals should be avoided. If the powder mixes mentioned above are made then certainly they should not be stored for any length of time hence they may ignite spontaneouslay by themselves!

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