# Magnesium nitride

Magnesium nitride
Names
IUPAC name
Magnesium nitride
Identifiers
ECHA InfoCard 100.031.826
Properties
Mg3N2
Molar mass 100.9494 g/mol
Appearance greenish yellow powder
Density 2.712 g/cm3
Melting point approx. 1500°C
Hazards
Safety data sheet External MSDS
R-phrases R36, R37, R38
S-phrases S26, S36
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Magnesium nitride, which possesses the chemical formula Mg3N2, is an inorganic compound of magnesium and nitrogen. At room temperature and pressure it is a greenish yellow powder.

## Preparation

• By passing dry nitrogen over heated magnesium:
${\displaystyle {\begin{matrix}{}\\{\ce {{3Mg}+N2->[{\ce {800^{\circ }C}}]Mg3N2}}\\{}\end{matrix}}}$
• or ammonia:
${\displaystyle {\begin{matrix}{}\\{\ce {{3Mg}+2NH3->[{\ce {700^{\circ }C}}]{Mg3N2}+3H2}}\\{}\end{matrix}}}$

## Chemistry

Magnesium nitride reacts with water to produce magnesium hydroxide and ammonia gas, as do many metal nitrides.

Mg3N2(s) + 6 H2O(l) → 3 Mg(OH)2(aq) + 2 NH3(g)

In fact, when magnesium is burned in air, some magnesium nitride is formed in addition to the principal product, magnesium oxide.

## Uses

Magnesium nitride was the catalyst in the first practical synthesis of borazon (cubic boron nitride).[1]

Robert H. Wentorf, Jr. was trying to convert the hexagonal form of boron nitride into the cubic form by a combination of heat, pressure, and a catalyst. He had already tried all the logical catalysts (for instance, those that catalyze the synthesis of diamond), but with no success.

Out of desperation and curiosity (he called it the "make the maximum number of mistakes" approach[2]), he added some magnesium wire to the hexagonal boron nitride and gave it the same pressure and heat treatment. When he examined the wire under a microscope, he found tiny dark lumps clinging to it. These lumps could scratch a polished block of boron carbide, something only diamond was known to do.

From the smell of ammonia, caused by the reaction of magnesium nitride with the moisture in the air, he deduced that the magnesium metal had reacted with the boron nitride to form magnesium nitride, which was the true catalyst.

When isolating argon, William Ramsay passed dry air over copper to remove oxygen and over magnesium to remove the nitrogen, forming magnesium nitride.

## References

1. ^ R. H. Wentorf, Jr. (March 1961). "Synthesis of the Cubic Form of Boron Nitride". Journal of Chemical Physics. 34 (3): 809–812. doi:10.1063/1.1731679.
2. ^ Robert H. Wentorf, Jr. (October 1993). "Discovering a Material That's Harder Than Diamond". R&D Innovator. Retrieved June 28, 2006.