Phosphorus pentoxide is a chemical compound with molecular formula P4O10 (with its common name derived from its empirical formula, P2O5). This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant and dehydrating agent.
Molar mass：283.9 g mol−1
Melting point：340 °C (644 °F; 613 K)
Boiling point：360 °C (sublimes)
Solubility in water：exothermic hydrolysis
Vapor pressure：1 mmHg @ 385 °C (stable form)
Used for preparing high purity high phosphoric acid, organic synthesis and gas desiccant, or for preparing polyphosphoric acid.