 Other acids of iodine(VII) that contain hydroxide groups are known, in particular in salts such as the "meso"periodate ion that occurs in K4[I2O8(OH)2]·8H2O.As is common outside of the alkali metals, hydroxides of the elements in lower oxidation states are complicated.For example, phosphorous acid H3PO3 predominantly has the structure OP(H)(OH)2, in equilibrium with a small amount of P(OH)3.