Arsenic(III) oxide (CAS: 1327-53-3)

Arsenic trioxide is the inorganic compound with the formula As2O3.

This commercially important oxide of arsenic is the main precursor to

other arsenic compounds, including organoarsenic compounds. Approximately

50,000 tonnes are produced annually. Many applications are controversial

given the high toxicity of arsenic compounds.

Uses

Large scale applications include its use as a precursor to forestry products, in

colorless glass production, and in electronics. Being the main compound of

arsenic, the trioxide is the precursor to elemental arsenic, arsenic alloys, and 

arsenide semiconductors. Organoarsenic compounds, e.g. feed additives (Roxarsone)

and pharmaceuticals (Neosalvarsan), are derived from arsenic trioxide. Bulk arsenic-based

compounds sodium arsenite and sodium cacodylate are derived from the trioxide.

A variety of applications exploit arsenic’s toxicity, including the use of the oxide as a

wood preservative. Copper arsenates, which are derived from arsenic trioxide, are used

on a large scale as a wood preservative in the US and Malaysia, but such materials are

banned in many parts of the world. This practice remains controversial. In combination

with copper(II) acetatearsenic trioxide gives the vibrant pigment known as paris green 

used in paints and as a rodenticide. This application has been discontinued.

Medical applications

Despite the well known toxicity of arsenic, arsenic trioxide has long been of biomedical

interest, dating to traditional Chinese medicine, where it is known as Pi Shuang and is still

used to treat cancer and other conditions, and to homeopathy, where it is called arsenicum

album. Some discredited patent medicines, e.g., Fowler’s solution, contained derivatives

of arsenic oxide.

Arsenic trioxide under the trade name Trisenox (manufacturer: Cephalon) is a chemotheraputic

agent of idiopathic function used to treat leukemia that is unresponsive to “first line” agents. It

is suspected that arsenic trioxide induces cancer cells to undergo apoptosis. Due to the toxic

nature of arsenic, this drug carries significant risks. Use as a cytostatic in the treatment of refractory

promyelocytic (M3) subtype of acute myeloid leukemia. The combination therapy of arsenic trioxide

and all-trans retinoic acid (ATRA) has been approved by the U.S. Food and Drug Administration (FDA)

for treatment of certain leukemias. University of Hong Kong developed a liquid form of arsenic

trioxide that can be administered orally.