arsenic

Name arsenic
Symbol As
Atomic Weight 74.92160
Atomic Number 33
CAS ID 7440-38-2
Group Number 15
Group Name Pnictogen
Period Number 4
Origin of Name Greek, arsenikon = "yellow orpiment."
Year Discovered 1230
Discovery Credits Probably first isolated by Alertus Magus (1193-1280).
Class Semi-metallic
Color Metallic Grey
Standard State Solid at 77 F & 298 K
Description Metalloid with several allotropes, Grey alpha-arsenic is metallic, soft and brittle, tarnishes, burns in O2, resists attack by water, acids, and alkalis. Attacked by hot acids and molten NaOH. Uses: alloys, semiconductors, pesticides, wood preservatives, and glasses.

Diagnostic tests:
Arsenides, sulpharsenites, etc. (As2-), give off fumes when roasted on charcoal, usually easily recognized by their peculiar garlic odor. In the open tube test, they give a white, volatile, crystalline sublimate of As2O3. In the closed tube test with sulfur, they yield a sublimate of dark brown-red when hot and red or reddish yellow when cold; or a black to gray mirror sublimate of metallic arsenic.
Arsenates (AsO4) can be detected by the garlic odor yielded when a mixture of the powdered mineral with charcoal dust and Na2CO3 is heated with a reducing flame on charcoal.

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