#oxidation state
- Arsenous — Said of an acid or a chemical compound in which arsenic has a lower valence (usually the +3 oxidation state), such as arsenous acid (H3AsO3). In classical chemical nomenclature, this adjective differentiates trivalent arsenic compounds from pentavalent ones (called arsenic), indicating distinct physico-chemical properties, a specific solubility, and a different toxicological profile in reactions with organic substances.