Supplier Data - Arsenic (As) (Goodfellow)

Discovered in the 13th. century by Albertus Magnus (although believed to have been used much earlier as an alloying addition to bronze to provide a lustrous finish).

Arsenic (As) is found in several allotropic forms and has both metallic and non-metallic properties. The grey metallic allotrope is a brittle, crystalline solid which tarnishes readily in air and burns in oxygen. Arsenic is resistant to attack by dilute acids and alkalis, but will react with hot acids and molten NaOH.

Occurrence

Arsenic is poisonous (it is thought to have been responsible for the death of Napoleon) and occurs both free and combined in many minerals (Arsenic has an abundance within the earth's crust of 1.5 ppm).

Production

The non-metallic allotropes include yellow arsenic (may be formed by rapid condensation of Arsenic vapour in an inert atmosphere) and black arsenic (may be formed by slow condensation of the vapour in an inert atmosphere).

Applications

Applications for grey Arsenic include its use as an alloying element, its use in the manufacture of certain types of glass and as a donor impurity in germanium semiconductor devices.

Key Properties

The key properties of Arsenic are tabulated below.

Table 1. Key properties

Atomic Properties
Atomic number 33
Atomic radius - Goldschmidt ( nm ) 0.125
Atomic weight ( amu ) 74.9216
Crystal structure Rhombohedral
Electronic structure Ar 3d10 4s2 4p3
Photo-electric work function ( eV ) 5.1
Thermal neutron absorption cross-section ( Barns ) 4.3
Valences shown -3, 0, 3, 5
Ionisation Potential No. eV
1 9.81
2 18.6
3 28.4
4 50.1
5 62.6
6 128
Natural Isotope Distribution Mass No. %
75 100
Electrical Properties
Electrical resistivity @ 20 °C ( µOhm.cm ) 33.3
Mechanical Properties
Material condition Polycrystalline
Bulk modulus ( GPa ) 22.0
Hardness - Vickers 57-69
Physical Properties
Boiling point (°C ) 616
Density @ 20 °C ( g.cm-3 ) 5.73
Melting point (°C ) Sublimes >300
Thermal Properties
Coefficient of thermal expansion @ 0-100 °C ( x10-6 K-1 ) 5.6
Latent heat of fusion ( J.g-1 ) 370
Specific heat @ 25 °C ( J.K-1.kg-1 ) 328
Thermal conductivity @ 0-100 °C ( W.m-1.K-1 ) 50.2

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