Magnesium
(Mg)
Elemental
magnesium is a gray-white lightweight metal, two-thirds the density of
aluminium. Magnesium has the lowest melting (923 K (650 °C)) and the
lowest boiling point (1,363 K (1,090 °C)) of all the alkaline earth
metals.
Magnesium
is highly flammable, especially when powdered or
shaved into thin strips, though it is difficult to ignite in mass or
bulk. Magnesium is the eighth-most-abundant element in the Earth's
crust by mass, does not naturally occur as a metal so requires
refining from ore. Pure magnesium metal is a brittle grey solid, so
typically magnesium is alloyed with aluminium to increase ductility and
toughness.
Physical
properties
| Phase at STP |
Solid |
| Melting
point |
923 K (650 °C, 1202 °F) |
| Boiling
point |
1363 K (1091 °C, 1994 °F) |
| Density (at
STP) |
1.737 g/cc
|
Most
magnesium is produced in batch using the thermochemical Pidgeon
process, which is the reaction of ferrosilicon (FeSi) with dolomite
(MgO). The energy requirements and CO2 emissions of the Pidgeon process
for Magnesium are both very high; 102 kWh/kg and 37 kgCO2/kg,
respectively [1-2]. Another process used to produce magnesium metal
from magnesium chloride is the Weston Electrolytic Process [3] which
uses less energy than the Pidgeon process.
The
video demonstration below shows some of the characteristics of
magnesium and producing magnesium metal from magnesium chloride.
[1]
https://arpa-e.energy.gov/sites/default/files/documents/files/METALS_ProgramSummary.pdf
[2] Aghion, E., and Bartos, S., Comparative Review of Primary Magnesium
Production Technologies as Related to
Global Climate Change, 65th Annual World Magnesium Conference, Warsaw,
Poland, May 18-20, 2008.
[3]
https://www.energy.gov/sites/prod/files/2017/12/f46/Magnesium_bandwidth_study_2017.pdf