Another oxide, As2O5, arsenic pentoxide, exists, but is less important.
"An Introduction to Chemical Science"
R.P. Williams
"Phosphorus pentoxide P2O5," he remarked coolly.
"Sisters Three"
Mrs. George de Horne Vaizey
The air within is very carefully dried by phosphorus 208 pentoxide before the experiment.
"The Birth-Time of the World and Other Scientific Essays"
J. (John) Joly