Iodic acid

Iodic acid
Other names
Iodic(V) acid
7782-68-5 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:24857 YesY
ChEMBL ChEMBL1161636 YesY
ChemSpider 22761 YesY
ECHA InfoCard 100.029.056
PubChem 24345
Molar mass 175.91 g/mol
Appearance White solid
Density 4.62 g/cm3, solid
Melting point 110 °C (230 °F; 383 K)
269 g/100 mL (20 °C)
Acidity (pKa) 0.75
Flash point Non-flammable
Related compounds
Other cations
Lithium iodate
Potassium iodate
Chloric acid
Bromic acid
Related compounds
Hydroiodic acid
Iodine pentoxide
Periodic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Iodic acid, HIO3, can be obtained as a white or off-white solid. It dissolves in water very well, but it also exists in the pure state, as opposed to chloric acid or bromic acid. Iodic acid contains iodine in the oxidation state +5 and it is one of the most stable oxo-acids of the halogens in its pure state. When iodic acid is carefully heated, it dehydrates to iodine pentoxide. On subsequent heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine.


Iodic acid can be produced by oxidizing I2 with strong oxidizers such as Nitric acid HNO
, Chlorine Cl
, Chloric acid HClO
or Hydrogen peroxide H
,[1] for example :

+ 6 H
+ 5 Cl
⇌ 2 HIO
+ 10 HCl


Iodic acid is a relatively strong acid with a pKa of 0.75. It is strongly oxidizing in acidic solution, less so in basic solution. When iodic acid acts as oxidizer, then the product of the reaction is either iodine, or iodide ion. Under some special conditions (very low pH and high concentration of chloride ion, e.g. in concentrated hydrochloric acid), iodic acid is reduced to iodine trichloride, a golden yellow compound in solution and no further reduction occurs. In the absence of chloride ions, when there is an excess amount of reductant, then all iodate is converted to iodide ion. When there is an excess amount of iodate, then part of the iodate is converted to iodine.


Iodic acid is used as a strong acid in analytical chemistry. It may be used to standardize solutions of both weak and strong bases, with methyl red or methyl orange as the indicator.

Use in salt industry

Iodic acid can be used to synthesize sodium or potassium iodate for increasing iodine content of salt.


  1. (German) Arnold F. Holleman, Nils Wiberg, « Lehrbuch der Anorganischen Chemie », 102. Auflage, Berlin, 2007. ISBN 978-3-11-017770-1
This article is issued from Wikipedia - version of the 6/8/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.