| IUPAC name
| Other names
Periodic acid dihydrate (ortho)
| HIO4 (metaperiodic)|
|Molar mass|| 227.941 g/mol (H5IO6)|
190.91 g/mol (HIO4)
|Melting point||128.5 °C (263.3 °F; 401.6 K)|
|Solubility||Soluble in alcohols|
|Safety data sheet||Sigma-Aldrich (ortho)|
| Perchloric acid|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Periodic acid is the highest oxoacid of iodine, in which the iodine exists in oxidation state +7. Like all periodates it can exist in two forms: orthoperiodic acid, with the chemical formula H5IO6 and metaperiodic acid, which has the formula HIO4.
- 2 HIO4 → I2O5 + H2O + O2
Like all periodates periodic acid can be used to cleave various 1,2-difunctional compounds. Most notably periodic acid will cleave vicinal diols into two aldehyde or ketone fragments (Malaprade reaction).
This can be useful in determining the structure of carbohydrates as periodic acid can be used to open saccharide rings. This process is often used in labeling saccharides with fluorescent molecules or other tags such as biotin.
Periodic acid is also used as an oxidising agent of moderate strength.
Both orthoperiodic and metaperiodic acid are white colorless crystalline solids, very soluble in water.
Periodic acid, both the ortho- and the meta- forms can be bought from chemical suppliers.
3 + 6 HO−
− 2 e− → IO5−
6 + 3 H2O (counter ions omitted for clarity) E° = ;-1.6 V
3 + 6 HO−
+ Cl2 → IO5−
6 + 2 Cl− + 3 H2O
Orthoperiodic acid can be dehydrated to give metaperiodic acid by heating to 100 °C under reduced pressure.
- H5IO6 ⇌ HIO4 + 2 H2O
- H5IO6 → HIO4 + 2 H2O
Periodic acid is irritant, corrosive and mildly oxidizer. Proper protection should be worn when handling the compound.
In closed airtight bottles, away from moisture and reducing agents.
Should be neutralized with a base to the safer periodate salts.
- Riley, edited by Georg Brauer; translated by Scripta Technica, Inc. Translation editor Reed F. (1963). Handbook of preparative inorganic chemistry. Volume 1 (2nd ed.). New York, N.Y.: Academic Press. pp. 323–324