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Arsen (As)
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Arsen 33As74.92
Wahrscheinlich zuerst von Albertus Magnus (1193-1280) dargestellt.
[Greek: arsenikon = gelbes Auripigment, Latin: arsenicum]
French: arsenic
English: Arsenic
Italian: arsenico
Spanish: arsénico
Beschreibung: Halbmetall, existiert in mehreren Modifikationen. Graues α-As ist metallisch glänzend und spröde, es läuft an, verbrennt in O2, wird nicht von Wasser, Säuren und Laugen angegriffen. Heiße Säuren und geschmolzenes NaOH greifen es an. Verwendung: Legierungen; Halbleiter; Pestizide; Holzschutzmittel; Glas.
Further Materials properties
| Crystal structure: |
(cell dimensions/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 diffractions mass absorption coefficients: | CuKa 83.4 (µ/r) / cm2g-1 MoKa 69.7 (µ/r) / cm2g-1 |
| Neutron scattering length: | 0.658 b/10-12 cm |
| Thermal neutron capture cross-section: | 4.30 sa / barns |
| Density: | 5780 (α) 4700 (β) kg/m-3 [293 K] |
| Melting point: | 816.85 °C / 1090 °K (α, under pressure) |
| Boiling point: | 615.85 °C / 889°K |
| Molar volume: | 12.95 (α) 15.9 (β) cm3 |
| Thermal conductivity: | 50.0 (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] Ωm |
| Mass magnetic susceptibility: | -9.17 x 10-10(α). -3.97 x 10-9 (β) kg-1m3 |
| Radi: | 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 |
| Isotope 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) = 100mg |
| Hazards: | Arsenic salts and arsine gases are very poisonous. In small doses arsenic acts to stimulate metabolism, but it is carcinogetic and possibly teratogenic. |
| Level in humans | |
| Blood: | 0.0017-0.09 mg dm-3 |
| Bone: | 0.08 - 1.6 ppm |
| Liver: | 0.023 - 1.61 ppm |
| Muscle: | 0.009 - 0.65 ppm |
| Daily dietary intake: | 0.04 - 1.4 mg |
| Total mass of element in average [70 kg] person: |
7 mg |
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 |
| Enagite | 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: | arsenopytite, realgar, orpiment. |
|---|---|
| World production: | 47000 (As2O3) tonnes/year |
| 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 pieces or powder. DANGER! |
| Abundances | |
|---|---|
| Sun: | n.a. (relative to H = 1 x 1012) |
| Earth's crust: | 1.5 ppm |
| Seawater | |
| Atlantic surface: | 1.45 x 10-3 ppm |
| Atlantic deep: | 1.53 x 10-3 ppm |
| Pacific surface: | 1.45 x 10-3 ppm |
| Pacific deep: | 1.75 x 10-3 ppm |
| Residence time: | 90 000 years |
| Classification: | As(III) scavenged, As(V) recycled |
| Oxidation state: | III but mainly V |
Source: Emsley, J. (1998) The Elements (3rd Edition)
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