Arsenic (As) Element Properties
Atomic Mass 74.9216
Atomic Number 33
Name Origins Greek, arsenikon = "yellow orpiment."
Year Discovered 1230
Discovery Credits Probably first isolated by Alertus Magus (1193-1280).
Remarks 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. The blue flame test for arsenic may be visible when the sublimate is blasted with the blowpipe flame.

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.

References Emsley, J., 1991; THE ELEMENTS : Sec. Ed., Clarendon Press, Oxford, 251 p.
See Also WebElements, ChemiCool
Naturally Occurring Isotopes
Symbol Isotope Mass Isotope Nuclide Number Isotope Number Natural Abundance Half-life Half-life Units Decay Mode Decay Mode MeV Decay Mode %
As 74.921594 75 33 100.0000%   Stable