Magnesium

 

Magnesium

Chemical formula	Mg
Atomic Number	12
OTP appearance	silver grey solid
Molar Mass(g/mol)	24.3
Melting Point(°C)	650
Boiling Point(°C)	1091
Density(g/cc)	1.8
NFPA 704	1 0 1

Uses

Justification Questioned

Other

• structural material
• high temperature deflagration
• Key component of Grignard reactions.

Natural occurence

• Elemental magnesium does not occur naturally
• magnesium carbonate occurs as the mineral magnesite
• magnesium hydroxide occurs as the mineral brucite
• magnesium sulfate occurs as the mineral epsomite

Production

Extraction

from magnesium chloride

A patent covers this process

1. Produce a saturated solution of magnesium chloride
2. Add liquid mercury
3. Run 4-5V through the solution and mercury, amalgamating the magnesium and freeing the chlorine.

   N.B. Good operating percentage is 2-4%Mg (w/w) in HgMg amalgam, which is 15-30% (molar)

   MgCl₂(aq) + Hg(l)

   {

   →

   4-5V, 80°C}

   HgMg(l) + Cl₂(g)

4. Flow the mercury out of the tube and cool it, producing a solid and liquid phase

   HgMg amalgam

   {

   →

   0°C}

   Hg₅Mg₂(s) + Hg(l)

5. Recycle the liquid mercury into the cell
6. Heat the solid, boiling the mercury and melting the magnesium

   Hg₅Mg₂

   {

   →

   ≥ 650°C}

   5 Hg(v) + 2 Mg(l)

7. Condense the vaporous mercury and recycle
8. Accumulate liquid magnesium until you have enough
9. Solidify magnesium

Purification

The most common adulterant is calcium. Magnesium oxalate is soluble in water and calcium oxalate is not.