The arsenite ion
(compound) is any compound
that contains this ion.
The arsenic atom in arsenite has a valency
of 3 and is also known as trivalent arsenic
Arsenite resembles phosphite in many respects, since arsenic and phosphorus occur in the same group (column) of the periodic table.
The arsenite ion may be formed from arsenic trioxide by adding base.
Its white odorless crystals are toxic and very soluble in water. It occurs in nature as arsenolite and claudetite and is also a by-product of metal smelting. Its main use is in producing copper chrome arsenate to treat timber. It is also used for arsenic pesticides, glass production, pharmaceuticals and non-ferrous alloys.
The definition above is incomplete. In fields that commonly deal with groundwater chemistry, arsenite
commonly refers to As2
and sodium arsenite refers to NaAsO2
. Sodium arsenite is used in the water gas shift reaction to remove carbon dioxide.
Bacteria using and generating arsenate
Some species of bacteria
obtain their energy by oxidizing
various fuels while reducing arsenates
to form arsenites. The enzymes
involved are known as arsenate reductases
In 2008, bacteria were discovered that employ a version of photosynthesis with arsenites as electron donors, producing arsenates (just like ordinary photosynthesis uses water as electron donor, producing molecular oxygen). The researchers conjectured that historically these photosynthesizing organisms produced the arsenates that allowed the arsenate-reducing bacteria to thrive.