Arsenic
Nonmetallic to semimetallic chemical element, chemical
symbol As, atomic number 33.
Photograph:Arsenic (gray) with realgar (red) and orpiment
(yellow)
Arsenic (gray)
with realgar (red) and orpiment (yellow)
It exists uncombined in two stable (and several unstable)
allotropes, one gray and one yellow, but is more often found in nature as the
sulfide or oxide. The elemental form is used to form alloys of metals
(especially lead), and certain semiconductors are made from crystals of gallium
arsenide (GaAs). Arsenious oxide (arsenic trioxide or white arsenic, As2O3) is
used in pesticides, as a pigment, and as a preservative of hides and wood; this
is the poisonous “arsenic” (see arsenic poisoning) in detective stories.
Arsenic pentoxide (As2O5) is also used in insecticides, herbicides, metal
adhesives, and pigments.
