Arsenic compounds (and their poisonous properties) have been known since ancient times, and the metallic form was isolated in the Middle Ages. Arsenic occurs naturally in orpiment, realgar, and other minerals, and rarely as the free element. Arsenic is used in semiconductors and some specialized alloys; its toxic compounds are widely used as herbicides and pesticides
- Chemistry of arsenic with a valency of five; of arsenic(V). Compare with arsenious.
late Middle English (denoting yellow orpiment, arsenic sulphide): via Old French from Latin arsenicum, from Greek arsenikon 'yellow orpiment', identified with arsenikos 'male', but in fact from Arabic al-zarnīḵ 'the orpiment', based on Persian zar 'gold'