Dinitrogen pentoxide is a chemical compound. It is made by removing water from nitric acid. Its chemical formula is N2O5. It is a powerful oxidizing agent. It is a white solid. It is made by reacting phosphorus(V) oxide with nitric acid. The phosphorus(V) oxide removes the water from the nitric acid. It can be dissolved in chloroform to add the NO2+ group to some chemical compounds. It is toxic as it can make nitrogen dioxide gas.