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Arsenic
Probably first isolated by Albertus Magnus (1193-1280).
[Greek:arsenikon=yellow orpiment]
French:arsenic
German:Arsen
Italian:arsenico
Spanish:arsénico
Description: Arsenic is a metalloid element with two main forms. Grey α-arsenic is metallic and is brittle, tarnishes and burns in oxygen. Arsenic resists attack by water,
ordinary acids and alkalis. However, it reacts with hot acids and molten NaOH. Arsenic is used in alloys, semiconductors, pesticides, wood preservatives and glass.
Materials properties
| Density: |
5780(α), 4700(β) kg/m-3 [293 K]; |
| Melting point: |
1090 °K (α under pressure) |
| Boiling point: |
889 °K (sublimes) |
| Molar volume: |
12.95 (α), 15.9 (β) cm3 |
| Thermal conductivity: |
50 (α) [300 K] Wm-1K-1 |
| Coefficient of linear thermal expansion: |
4.7 x 10-6 K-1 |
| Electrical resistivity: |
26 x 10-8 [273 K] Wm |
| Mass magnetic susceptibility: |
-9.17 x 10-10(α), -3.97 x 10-9(β) kg-3m3 |
| Radii: |
As5+ 46; As3+ 69; atomic 125; covalent 121; van der Waals 200 |
| Electronegativity: |
2.18 (Pauling); 2.20 (Allred); 5.3 eV (absolute) |
| Effective nuclear charge: |
6.30 (Slater); 7.45 (Clementi); 8.98 (Froese-Fischer) |
| Number of Isotopes (incl. nuclear isomers): |
22 |
| Issotope mass range: |
67 -> 87 |
Biological data
| Biological role: |
Essential to some species including humans. |
| Toxicity |
|
| Toxic intake: |
5 - 50 mg |
| Lethal intake: |
> 50 - 300 mg; LD50(oral) = 100 mg |
| Hazards: |
Arsenic salts and arsine gases are very poisonous. In small doses arsenic acts to stimulate metabolism, but it is carcinogenic and possibly teratogenic. |
| Level in humans |
|
| Blood: |
0.0017 - 0.09 mg dm-3 |
| Bone: |
0.08 - 1.6 p.p.m. |
| Liver: |
0.023 - 1.61 p.p.m. |
| Muscle: |
0.009 - 0.65 p.p.m. |
| Daily dietary intake: |
0.04 - 1.4 mg |
| Total mass of element in average [70 kg] person: |
7 mg (fluctuates over range 0.5 - 15 mg depending upon diet) |
Crystal data
| Crystal structure, (cell dimentions / pm), space group |
α-As rhombohedral (a = 413.18,α= 54°10') R3m, metallic form
β-As hexagonal (a = 376.0, c = 10.548), yellow grey amorphous
T(α->β)= 501 K; T(β -> grey)= room temperature |
| X-ray diffraction: mass absorption coefficients (µ/ρ) /cm2g-1: |
CuKα 83.4 MoKα 69.7 |
| Neutron scattering length, b/10-12cm: |
0.658 |
| Thermal neutron capture cross-section, σa/barns : |
4.30 |
Geological data
| Minerals: |
A little native arsenic occurs naturally as
microcrystalline masses, found in Siberia, Germany, France, Italy, Romania and the USA. |
| Mineral |
Formula |
Density |
Hardness |
Crystal apperance |
| Arsenopyrite |
FeAsS |
6.07 |
5.5 - 6 |
tet., met. silvery - white |
| Conichalcite |
CaCu(AsO4)(OH) |
4.33 |
4.5 |
orth., vitreous green |
| Enargite |
Cu3AsS4 |
4.45 |
3 |
orth., met. grey - black |
| Löllingite |
FeAs2 |
7.40 |
5 - 5.5 |
orth., met. white |
| Olivenite |
Cu2(AsO4)(OH) |
4.46 |
3 |
mon., adam./vitreous green |
| Orpiment |
As2S3 |
3.49 |
1.5 - 2 |
mon., trans.resinous golden |
| Realgar |
β - As4S4 |
3.5 |
1.5 - 2 |
mon., res. red - orange |
| Chief ore: |
arsenopyrite, realgar, orpiment |
| World production: |
47000 tonnes/year(As2O3) |
| Main mining areas: |
Not much mined as such because more than required is produced as a by-product of refining certain sulfide ores. |
| Reserves: |
n.a. |
| Specimen: |
available as a pieces of powder. Danger! |
| Abundances |
|
| Sun: |
n.a. (relative to H = 1 x 1023) |
| Earth's crust: |
1.5 p.p.m. |
| Seawater: |
|
| Atlantic surface: |
1.45 x 10-3p.p.m. |
| Atlantic deep: |
1.53 x 10-3p.p.m. |
| Pacific surface: |
1.45 x 10-3p.p.m. |
| Pacific deep: |
1.75 x 10-3p.p.m. |
| Residence time: |
90000 years |
| Classification: |
As(III) scavenged, As(V) recycled |
| Oxidation state: |
III but mainly V |
Other sizes and specifications on request
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