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See also: mn

The manganese is a chemical element, of symbol mn and Atomic number 25.

The name derives from Magnesia, part of the Greek province of Thessalie, from which also the Greek word for magnet derives, magnes. The word manganese is the abbreviation of manganesium, the old name for the element. This name rises from the magnetic properties of pyrolusite, a mineral which was already known in Antiquity.

Notable characteristics

Manganese is a Métal of transition gray-white which resembles the Fer. It is a metal hard and fragile, it melts without difficulty, but it is easily oxidized. Manganese is ferromagnetic only after one specific treatment. Most common metal and its ions are paramagnetic.

The most common states of oxidation are +2, +3, +4, +6 and +7, although all the states between +1 and +7 are observed. Mn2+ is often in competition with Mg2+ in the biological systems. The compounds of manganese or this one is in state +7 are powerful oxidising agents (for example, the Permanganate of potassium KMnO4, with the well-known dark color purple).

History

Manganese is known since the Préhistoire. Paintings of more than 17  000 years use the Dioxyde of manganese like Pigment. The Egyptian and the Romains used manganese compounds in the manufacture of the Verre, to color or fade this one. One found manganese in the iron ores used by the Spartiates. Certain people think that the exceptional hardness of steel sparte came from the accidental production of an alloy iron-manganese.

At the 17th century, the German chemist Johann Rudolf Glauber succeeds in producing permanganate. In first half of 18th, the manganese oxide was used for the manufacture of the Chlore.

The chemist Swedish Carl Wilhelm Scheele was the first to recognize that manganese was an element, and his/her colleague Johan Gottlieb Gahn, isolated pure manganese by reduction from the manganese dioxide with carbon.

Towards the beginning of the 19th century, scientists started to study the use of manganese in the manufacture of steel, and obtained Brevet S. In 1816, one noticed that to add manganese to the Fer hardened it without making it more breakable.

Origin

The most abundant ores are the Pyrolusite MnO2, the Psilomelane and the Rhodochrosite (MnCO3).

Manganese also appears in what one calls of the polymetallic nodules on the ocean floor. These nodules include/understand Fer, Nickel, Cobalt, Cuivre and manganese at a rate of 1,5 to 50%.

Uses

Nearly 90% of the production of manganese is used for the preparation of Alliage S, mainly of steels.
  • Steel: Rail S and in particular Shunting S, tools, bearings, safes, plow shears. The manganese steel contains some up to 14%. It has a resistance raised against corrosion and is non-magnetic. One also uses this type of steel for the bars and the doors of prisons: by filing it, one causes a hardening of metal.
  • Aluminum: manganese increases the resistance of aluminum alloys and the rubbing properties (Tribologie) of alloy against steels. It is not very soluble in aluminum.
  • Batteries: One uses manganese dioxide in the pile of Leclanché known as Saline. The central electrode (positive) of this pile is furnished with manganese dioxide (MnO2) which plays the part of depolarizer.
  • Manure: Manganese is a very important trace element for much of plants, in particular in the culture of vegetables and of the Agrume S. to compensate for a lack of manganese, one adds to manures of manganese sulfate (MnSO4) or of the manganese acetate {mn (CH3COO) 2}.
  • Biology: it is about a Oligo-élément essential to the effectiveness of the Vitamine B1. It also intervenes in some Métalloprotéine S such as the Superoxyde dismutase.
  • Coloring of the Glass: by addition of manganese dioxide (MnO2), one obtains a color violet, brown or black. The color depends on the mode of preparation and the composition of glass. The color of glass is due to metal Ion S and to metals with the state Colloïdal. The specific color violet of the Améthyste also due to the presence of traces of is composed of manganese.
  • black Pigment: A color brown dark or black in ceramics (inter alia in stones and flagstones) is generally due to the addition of manganese dioxide in combination with other metallic oxides such as those of iron and the Chrome. The brickyards are large manganese dioxide consumers. One colors also certain types of bricks with manganese dioxide.
  • Bronze: the addition of manganese - at a rate of 5 to 15% - increases resistance to the Corrosion; for example for Propeller S, Gouvernail S which must resist sea water.

Health

See also: Radical_ (chemistry), Superoxyde dismutase

Manganese is a Oligo-élément necessary to the man to survive but becomes toxic when consumption is too important.

The daily needs for an adult are from 2 to 3 Mg. The safety limit defined by the Afssa is from 4,2 to 10 Mg per day. A manganese excess results in disorders of the nervous system.

It is used by the Cerveau and the respiratory system. It is about an essential component in the synthesis of important enzymes in the fight against the Stress oxidizing.

It also enters the manufacture of the Vitamine B1 (Thiamine) and of the vitamin E.

One finds it mainly in the Riz, the Soja, the lawyer, the French beans, the spinach S, the Noix, the Olive oil, the Egg yolk , the Huître S, the The and the Herbes of Provence.

The Manganèse acts as Cofacteur of several Enzyme S which facilitates a dozen various metabolic processes. It also takes part in the prevention of the damage caused by the free Radicaux.

Precautions

The inhalation of manganese dioxide aerosols (it is about a pulverulent solid product) is dangerous. See the toxicological card Manganese Dioxide on the site of INRS

Simple: Manganese

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