Phosphorus pentoxide 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. Wikipedia https://en.wikipedia.org/wiki/Phosphorus_pentoxide Added to support Critical Zone Observatory (CZO) data use cases. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.