Diphosphorus pentoxide, P2O5, is sometimes called "phosphoric anhydride" because it reacts with water to form
phosphoric acid, H3PO4:
P2O5(s) + 3 H2O(
) 
2 H3PO4
The reaction releases a tremendous amount of heat and is quite violent. The solution often vaporizes and splashes out
of the container, accompanied by choking white fumes. The P2O5 is corrosive and very toxic, and the concentrated droplets of phosphoric acid solution it sprays can cause permanent eye damage and severe burns. Don't try this at home. Please.
P2O5 is prepared by burning phosphorus in extremely dry air.
Diphosphorus pentoxide dehydrates moist air and any material it comes into contact with.
It is often used as a dehydrating agent used in the synthesis of organic materials.
Author: Fred Senese senese@antoine.frostburg.edu