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The iodate anion,
Space-filling model of the iodate anion

An iodate is the anion with the formula . It is the most common form of iodine in nature, as it comprises the major iodine-containing ores.[1] Iodide salts are often colorless.


Iodate is pyramidal in structure. The O-I-O angles range from 105-97°, somewhat smaller than the O-Cl-O angles in chlorate.[2]



Iodate is one of several oxyanions of iodine. It participates in several redox reactions, e.g. the iodine clock reaction. Iodate show no tendency to disproportionate to periodate and iodide, in contrast to the situation for chlorate.

Iodate is reduced by sulfite:[1]

6HSO3- + 2IO3- -> 2NaI + 6HSO4-

Iodate oxidizes iodide:

5I- + IO3- + 3H2SO4 -> 3I2 + 3H2O + 3SO42-

Similarly chlorate oxidizes iodide:

I- + ClO3- -> Cl- + IO3-

Iodate is also obtained by reducing a periodate with a sulfide. The byproduct of the reaction is a sulfoxide.[3]


Iodate is unusual in that it forms a strong hydrogen bond with its parent acid:[2]

IO3- + HIO3 -> H[IO3]2-

The anion H[IO3]2- is referred to as biiodate.

Principal compounds

Natural occurrence

Minerals containing iodate are found in the caliche deposits of Chile. The most important iodate minerals are lautarite and brüggenite, but also copper-bearing iodates (e.g., salesite) are known.[6]


  1. ^ a b Lyday, Phyllis A. (2005). "Iodine and Iodine Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 382-390. doi:10.1002/14356007.a14_381.
  2. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. ^ Qiu, Chao; Sheng Han; Xingguo Cheng; Tianhui Ren (2005). "Distribution of Thioethers in Hydrotreated Transformer Base Oil by Oxidation and ICP-AES Analysis" (abstract). Industrial & Engineering Chemistry Research. 44 (11): 4151-4155. doi:10.1021/ie048833b. Retrieved . Thioethers can be oxidized to sulfoxides by periodate, and periodate is reduced to iodate
  4. ^ "Archived copy". Archived from the original on 2013-10-17. Retrieved .CS1 maint: archived copy as title (link)
  5. ^ "Archived copy". Archived from the original on 2013-10-18. Retrieved .CS1 maint: archived copy as title (link)
  6. ^

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