Arsenic pentoxide, also known as arsenic(V) oxide, is a chemical compound. Its chemical formula is AsO. It has arsenic and oxide ions in it. The arsenic is in its +5 oxidation state. More common is arsen in its oxidation state +3 as AsO (arsenic trioxide or arsenic(III) oxide). The LD50 for arsenic pentoxide is 8mg/kg for rats. When the substance becomes wet, it turns into arsenic acid, which corrodes metals.