Periodic acid, also known as periodic acid, is an oxygenated acid of iodine (VII) in two forms, with chemical formulas of hio4 and h5io6 respectively. H + and IO4 − ions are present in the dilute solution of periodic acid. With the increase of concentration, periodate begins to exist in the form of normal periodate h5io6, and crystals can be precipitated from the solution. Normal periodic acid is dehydrated to obtain metaiodate hio4. Further dehydration generates iodine sevoxide (colorless viscous liquid). After decomposition of iodine sevoxide, iodine pentoxide (i2o5) and oxygen are obtained. Normal periodate and metaiodate can form salts respectively, which are called "normal periodate" and "metaiodate". The solubility and chemical properties of metaiodate are similar to those of perchlorate of the same halogen group, but the anion radius is larger and the oxidation is weaker. In organic chemistry, periodate can oxidize o-diol and break the carbon carbon bond to form two aldehydes, which are used to determine the structure of sugars.