pentoxide
Pen*tox"ide, n. Etym: [Penta- + oxide.] (Chem.) Defn: An oxide containing five atoms of oxygen in each molecule; as, phosphorus pentoxide, P2O5.
Pen*tox"ide, n. Etym: [Penta- + oxide.] (Chem.) Defn: An oxide containing five atoms of oxygen in each molecule; as, phosphorus pentoxide, P2O5.