<Tr> <Td_colspan="2"> Infobox references </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> </Tr> <P> Phosphorous acid is the compound described by the formula H PO . This acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula . Phosphorous acid is an intermediate in the preparation of other phosphorus compounds . </P> <P> H PO is more clearly described with the structural formula HPO (OH). In the solid state, HP (O) (OH) is tetrahedral with one shorter P =O bond of 148 pm and two longer P--O (H) bonds of 154 pm . This species exists in equilibrium with an extremely minor tautomer P (OH). IUPAC recommends that the latter be called phosphorous acid, whereas the dihydroxy form is called phosphonic acid . Only the reduced phosphorus compounds are spelled with an "ous" ending . </P>

What is the systematic name for aqueous h3po3