MAGNESIUM


Here is a brief description of magnesium.

Year discovered: 1808

Atomic No.: 12

Symbol: Mg

Atomic weight: 24.305

Melting point: 648.8º C ± 0.5

Standard state: solid at 298 K

Colour: silvery white

Classification: Metallic

Availability: magnesium is available in several forms including chips, granules, powder, rod, foil, sheet, rod, turnings, and ribbon.


Magnesium is the eighth most abundant element in the earth’s crust. There’s enough of it already dissolved in seawater to satisfy the world’s requirements until the Millennium. Magnesium was discovered as a chemical element by Sir Humphrey Davy in 1808, but it took 22 more years and French scientist A. Bussy to isolate it via magnesium chloride reduction. Magnesium is used as the main alloying element in aluminum sheet for the production of aluminum cans, and the use of magnesium alloys in die casting is increasing rapidly.

SOURCE:

Magnesium is produced for profit in such places as the United States and Canada, Western Europe, South America and Asia. In the Commonwealth of Independent States (CIS) it is produced for hard Western cash and, like aluminum, seems to be exported to the West in pursuit not of profit but for what the traffic will bear.

Magnesium tarnishes slightly in air, and finely divided magnesium readily ignites upon heating in air and burns with a dazzling white flame. Normally magnesium is coated with a layer of oxide, MgO, that protects magnesium from air and water.


Isolation :

Here is a brief summary of the isolation of magnesium.

Magnesium can be made commercially by several processes and would not normally be made in the laboratory because of its ready availability. There are massive amounts of magnesium in seawater. This can be recovered as magnesium chloride, MgCl2 through reaction with calcium oxide, CaO.


CaO + H2O  Ca2+ + 2OH-

Mg2+ + 2OH-  Mg(OH)2

Mg(OH)2 + 2HCl  MgCl2 + 2H2O

Electrolysis of hot molten MgCl2 affords magnesium as a liquid whih is poured off and chlorine gas.

cathode: Mg2+(l) + 2e-  Mg anode: Cl-(l)  1/2Cl2 (g) + e-

The other methos used to produce magnesium is non electrolytic and involves dolomite, [MgCa(CO3)2], an important magnesium mineral. This is "calcined" by heating to form calcined dolomite, MgO.CaO, and this reacted with ferrosilicon alloy.

2[MgO.CaO] + FeSi  2Mg + Ca2SiO4 + Fe

The magnesium may be distilled out from this mixture of products.