MAGNESIUM ARSENIDE Property

Melting point:

800°C

Density 

3.148

solubility 

insoluble in H2O

form 

solid

Sensitive 

Moisture Sensitive

CAS DataBase Reference

12044-49-4

EPA Substance Registry System

Magnesium arsenide (Mg3As2) (12044-49-4)

Safety

RIDADR 

UN1557

TSCA 

Yes

HazardClass 

6.1

PackingGroup 

II

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H301Toxic if swalloed

H331Toxic if inhaled

H400Very toxic to aquatic life

H410Very toxic to aquatic life with long lasting effects

Precautionary statements

P261Avoid breathing dust/fume/gas/mist/vapours/spray.

P304+P340IF INHALED: Remove victim to fresh air and Keep at rest in a position comfortable for breathing.

P405Store locked up.

MAGNESIUM ARSENIDE Chemical Properties,Usage,Production

Description

Magnesium arsenide has the molecular formula of Mg3As2 and the molecular weight of 223.6592 g/mol. It may be prepared by direct reaction between the elements. Since As sublimes at 614°C and Mg melts at 650°C, the latter is melted at about 675°C in an inert atmosphere like argon (not N2 which would form nitrides) and arsenic vapors are carried into the reaction zone by a stream of Ar gas:
3Mg + 2As + heat ? Mg3As2
Mg3As2 is obtained by this method as a deep-brown, X-ray amorphous powder. Magnesium arsenide has the CAS number of 12044-49-4. This compound decomposes in contact with water:
Mg3As2 + 3H2O ? 2AsH3 + 3Mg(OH)2
Thus, it must be stored under dry conditions. Its density is 3.15 g/cm³. This compound is dimorphic with the low temperature form, β-Mg3As2 being cubic (α = 12.33?) and the high-temperature form, α-Mg3As2 being hexagonal. It crystallizes in the anti-La2O3 crystal structure, with unit-cell parameters of: a = 4.264A ° , c = 6.738?, c/a = 1.580. Both of these compounds are semiconductors. The latter has a band gap, E_g, of 2.2eV (564 nm).

Uses

The structure of magnesium arsenide is not ionic but covalent. Magnesium arsenide was used as a rodenticide and insecticide. Its toxicity to humans has led to its prohibition in the US and Europe.