Periodic Table ~ arsenic ~ Element ~ CAS 7440-38-2

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. (As^2-), 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.