Magnesium is a fairly strong, silvery-white, light-weight metal (one third lighter than aluminum)
that slightly tarnishes when exposed to air.
In a powder, this metal heats and ignites when exposed to air and burns with a white flame.
It is difficult to ignite in bulk, though it is easy to light if it is shaved in to thin strips.
Magnesium compounds, primarily magnesium oxide, are used mainly as refractory material in furnace linings for producing iron and steel, nonferrous metals, glass, and cement. Magnesium oxide and other compounds also are used in agricultural, chemical, and construction industries. This element's principal use is as an alloying additive to aluminum with these aluminum-magnesium alloys being used mainly for beverage cans[?]. Magnesium alloys also are used as structural components of automobiles and machinery. Another use of this metal is to aid the removal of sulfur from iron and steel.
Other uses include:
Magnesium, like aluminum, is strong and light, so it is often used in high grade car wheels, called "mag wheels."
Combined in alloys this metal is essential for airplane and missile construction.
When used as an alloying agent, this metal improves the mechanical, fabrication, and welding characteristics of aluminum.
Additive agent for conventional propellants and used in producing nodular graphite in cast iron.
Reducing agent for the production of pure uranium and other metals from their salts.
The name originates from the Greek word for a district in Thessaly called Magnesia[?].
Joseph Black[?] in England recognized magnesium as being an element in 1755, Sir Humphrey Davey electrolytically isolated pure magnesium metal in 1808 from a mix of magnesia and HgO and AA Bussy[?] prepared it in coherent form in 1831. Magnesium is the eighth most abundant element in the earth's crust. It is a rare earth element and therefore doesn't occur uncombined with other elements. It is found in large deposits of magnesite[?], dolomite, and other minerals.
Organic magnesium is important in both plant and animal life. Chlorophylls are magnesium-centered porphyrins.
The adult daily nutritional requirement, which is affected by various factors include weight and size, is about 300 mg/day.
Magnesium-26 is a stable isotope that has found application in isotopicgeology, similar to that of aluminum. Mg-26 is a radiogenic daughter product of Al-26 (half -life[?] = 0.72x106 yr). Large enrichments of stable Mg-26 have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite[?]meteorites. The anomalous abundance of Mg-26 is attributed to the decay of its parent Al-26 in the inclusions. Therefore, the meteorite must have formed in ation sources and external links: the solar nebula before the Al-26 had decayed. Hence, these fragments are among the oldest objects in the solar system and have preserved information about its earliest history.
It is conventional to plot Mg-26/Mg-24 against an Al/Mg ratio. In an isochron plot[?], the Al/Mg ratio plotted is Al-27/Mg-24. The slope of the isochron has no age significance, but indicates the initial Al-26/Al-27 ratio in the sample at the time when the systems were separated from a common reservoir.
Magnesium metal is highly flammable in its pure form, especially when it is a powder.
Magnesium metal quickly reacts exothermically upon contact with air or water and should be handeld with care.
Water should not be used to extinguish magnesium fires.
quelle horreur ne/ne.html">ne fut-il pas saisi en voyant ce champ.html">champ presque
besogne, en jetant les dernières gerbes dans un obscur abîme
vous aviez dit que vous moissonneriez ce champ là-bas?
--J'ai/ai.html">ai dit, répondit le gnome.html">gnome.html">gnome.html">gnome.html">gnome, que j'allais récolter votre blé,
parlez est.html">est à Wilhelm, n'est-il pas vrai?
--Oui, malheureux que je suis!
Et, tombant à genoux pour implorer le gnome, Carl lui demanda
gerbe; puis la terre se referma, ne laissant aucune trace qui pût
engloutie.
--Maintenant, comme vous voyez, j'ai fermé la porte de ma grange,
bonjour, Carl!
Et il s'éloigna d'un air.html">air calme et satisfait.
Carl erra ça et là, à moitié fou, oubliant jusqu'à son dîner.
vouloir répondre aux questions affectueuses de sa soeur, il alla
bouleversée sur l'oreiller, qu'une voix vint le réveiller, et lui
ainsi réveillez-vous et m'écoutez.
Il sortit sa tête de dessous les couvertures, et vit que sa
gnome assis sur le parquet de la chambre.
--Ah! misérable! s'écria-t-il, viens-tu/tu.html">tu me voler mon.html">mon.html">mon repos,
vengeance sur toi.
--Allons, allons, dit le gnome en riant, tu raffoles!... Ne
vaudrait essayer d'étreindre l'air que de tenter de m'étreindre,
richesses sans fin; car vous êtes un homme selon mon coeur:
Écoutez-moi donc, mon bon Carl. Venez me trouver demain au soir,
l'excessive abondance dépasse toute imagination humaine.
soeur serait une excellente victime, car il a des amis qui
qu'il pourrait vous en donner serait de peu d'importance pour
vous parle, vous en viendrez à dédaigner les sommes minimes que
jolis rêves!
La lumière s'évanouit et le gnome partit.
.
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