HIO4

Periodic acid, with the chemical formula HIO4, is a highly oxidized iodine compound known as the acid form of the periodate ion IO4−. It represents the fully oxidized state of iodine in aqueous solution and is related to periodate salts such as sodium periodate (NaIO4) and potassium periodate (KIO4). In practice, periodic acid is used as a reagent in organic and biological chemistry where a strong oxidizing effect is required.

In solution, periodic acid acts as a strong oxidant and participates in reactions characteristic of periodates. A key property is its ability to cleave vicinal (1,2-) diols, converting each carbon of the diol into a carbonyl compound (aldehyde or ketone) and thereby fragmenting the carbon skeleton. This oxidation is a fundamental tool in carbohydrate chemistry and glycan analysis, where diol-containing structures are common. Periodic acid is also employed in histology as part of the periodic acid–Schiff staining method, where the oxidation of carbohydrate moieties generates aldehyde groups that react with Schiff reagent to produce a magenta color.

Safety and handling are important considerations. HIO4 is a strong oxidizer and a corrosive substance; it can cause burns and should be kept away from reducing agents, organic materials, and incompatible substances. It is typically used under controlled laboratory conditions, either as a solution or as a solid in stabilized formulations, with appropriate personal protective equipment.

See also: periodate, periodate oxidation, periodic acid–Schiff reaction.