Magnesium

Magnesium is the chemical element in the periodic table that has the symbol Mg and atomic number 12. Magnesium is the eighth most abundant element and constitutes about 2% of the Earth's crust by weight, and it is the third most plentiful element dissolved in seawater. This alkaline earth metal is primarily used as an alloying agent to make aluminium-magnesium alloys, sometimes called "magnalium" or "magnelium".

Precautions

• Magnesium metal and alloys are highly flammable in their pure form when molten and when it is a powder. Magnesium metal quickly reacts exothermically upon contact with air or water and should be handled with care. One should wear safety glasses while working with magnesium. The bright white light (including ultraviolet) produced by burning magnesium can damage the eyes. Water should not be used to extinguish magnesium fires, because it can actually feed the fire, according to the reaction:

:Mg(s) + 2 H2O(l) → Mg(OH)2(aq) + H2(g)

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:Carbon dioxide fire extinguishers should not be used either, because magnesium can burn in carbon dioxide (forming magnesium oxide, MgO, and carbon). A Class D dry chemical fire extinguisher should be used if available, or else the fire should be covered with sand.

Related Topics:
Fire extinguisher - Magnesium oxide - Carbon - Class D - Sand

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• The DRI upper tolerated limit for supplemental magnesium is 350 mg/day. The most common symptom of excess magnesium is diarrhea. Infants should not be given magnesium supplements.