Pentoxide, a compound having five atoms of oxygen combined with another element or radical.
Niobium pentoxide is one kind of Pentoxide. Niobium pentoxide, is the chemical compound with the formula Nb₂O₅. It is used mainly in the production of capacitors, lithium niobate, and optical glass. Nb₂O₅ forms when niobium metal is oxidised in air. The oxidation of niobium dioxide, NbO₂ in air forms the polymorph, L-Nb₂O₅. Pure Nb₂O₅ can be prepared by hydrolysis of NbCl₅ :
    2 NbCl₅ + 5 H₂O → Nb₂O₅ + 10 HCl
A method of production via sol-gel techniques has been reported hydrolysing niobium alkoxides in the presence of acetic acid, followed by calcination of the gels to produce the polymorphic form, T-Nb₂O₅.
Phosphorus pentoxide is another kind of Pentoxide.Phosphorus pentoxide is a chemical compound with molecular formula P₄O₁₀. Its appearance is white crystalline solid, and Phosphorus pentoxide is the anhydride of phosphoric acid. It is a powerful desiccant. Phosphorus pentoxide is prepared by burning elemental phosphorus with sufficient supply of air :
    P₄ + 5O₂ → 2 P₂O₅
For most of the 20th century, phosphorus pentoxide was used to provide a supply of concentrated pure phosphoric acid. In the thermal process, the phosphorus pentoxide obtained by burning white phosphorus was dissolved in dilute phosphoric acid to produce concentrated acid. Improvements in filter technology is leading to the "wet phosphoric acid process" taking over from the thermal process, obviating the need to produce white phosphorus as a starting material. The dehydration of phosphoric acid to give phosphorus pentoxide is not practicable; on heating, metaphosphoric acid will decompose before it loses water.