| 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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