Potassium iodate or potassium iodate is an inorganic iodine compound, specifically a salt, whose chemical formula is KIO 3 . Iodine or iodine, an element from the group of halogens (F, Cl, Br, I, As), has an oxidation number of +5 in this salt; for this reason it is a strong oxidizing agent. KIO 3 dissociates in aqueous medium to create K + and IO 3 – ions .
It is synthesized by reacting potassium hydroxide with iodic acid: HIO 3 (aq) + KOH (s) => KIO 3 (aq) + H 2 O (l). Also, it can be synthesized by reacting molecular iodine with potassium hydroxide: 3I 2 (s) + 6KOH (s) => KIO 3 (aq) + 5KI (aq) + 3H 2 O (l).
Potassium iodate properties
It is an odorless white solid, with fine crystals and a monoclinic-type crystalline structure. It has a density of 3.98g / mL, a molecular weight of 214 g / mol, and has absorption bands in the infrared (IR) spectrum.
It has a melting point: 833 ºK (560 ºC), consistent with the strong ionic interactions between the K + and IO 3 – ions . At higher temperatures it undergoes a thermal decomposition reaction, releasing molecular oxygen and potassium iodide:
In water, it has solubilities that vary from 4.74g / 100mL at 0 ºC, up to 32.3 g / 100mL at 100 ºC, generating colorless aqueous solutions. Also, it is insoluble in alcohol and nitric acid, but it is soluble in dilute sulfuric acid.
Its affinity for water is not appreciable, which explains why it is not hygroscopic and does not exist in the form of hydrated salts (KIO 3 · H 2 O).
Potassium iodate, as indicated by its chemical formula, has three oxygen atoms. This is a strongly electronegative element and, due to this property, it leaves an electronic deficiency “discovered” in the cloud that surrounds the iodine.
This deficiency – or contribution, as the case may be – can be calculated as the oxidation number of iodine (± 1, +2, +3, +5, +7), being +5 in the case of this salt.
What does this mean? That before a species capable of giving up its electrons, iodine will accept them in its ionic form (IO 3 – ) to become molecular iodine and have an oxidation number equal to 0.
The iodine clock consists of a redox process with slow and fast steps, in which the fast steps are marked by a KIO 3 solution in sulfuric acid to which starch is added. Next, the starch – once the species I 3 has been produced and anchored between its structure – – will turn the solution from colorless to dark blue.
IO 3 – + 3 HSO 3 – → I – + 3 HSO 4 –
IO 3 – + 5 I – + 6 H + → 3 I 2 + 3 H 2 O
I 2 + HSO 3 – + H 2 O → 2 I – + HSO 4 – + 2 H + (dark blue due to starch effect)
The upper image illustrates the chemical structure of potassium iodate. The anion IO 3 – is represented by the “tripod” of red and purple spheres, while the K + ions are represented by the purple spheres.
But what do these tripods mean? The correct geometric shapes for these anions are actually trigonal pyramids, in which oxygens make up the triangular base, and the unshared pair of iodine electrons points upward, taking up space and forcing the I – O bond to bend downward and the two bonds I = O.
This molecular geometry corresponds to an sp 3 hybridization of the central iodine atom; However, another perspective suggests that one of the oxygen atoms forms bonds with the “d” orbitals of iodine, being in reality a hybridization of the sp 3 d 2 type (iodine can have its “d” orbitals expanding its layer of Valencia).
The crystals of this salt can undergo structural phase transitions (arrangements other than monoclinic) as a consequence of the different physical conditions that subject them.
Uses and applications of potassium iodate
Potassium iodate is usually used to prevent the accumulation of radioactivity in the thyroid in the form of 131 I, when this isotope is used in the determination of iodine uptake by the thyroid as a component of the functioning of the thyroid gland.
Similarly, potassium iodate is used as a topical antiseptic (0.5%) in mucosal infections.
Use in industry
It is added to the food of breeding animals as an iodine supplement. Therefore, potassium iodate is used in industry to improve the quality of flours.
In analytical chemistry, thanks to its stability, it is used as a primary standard in the standardization of standard solutions of sodium thiosulfate (Na 2 S 2 O 3 ), in order to determine the iodine concentrations in the test samples.
This means that the amounts of iodine can be known by volumetric techniques (titrations). In this reaction, potassium iodate rapidly oxidizes iodide ions I – , by means of the following chemical equation:
IO 3 – + 5I – + 6H + => 3I 2 + 3H 2 O
The iodine, I 2 , is titrated with the Na 2 S 2 O 3 solution for standardization.
Use in laser technology
Studies have demonstrated and corroborated the interesting piezoelectric, pyroelectric, electro-optical, ferroelectric and non-linear optics properties of KIO 3 crystals . This results in great potentials in the electronic field and in laser technology for materials made with this compound.
Health risks of potassium iodate
In high doses it can cause irritation to the oral mucosa, skin, eyes and respiratory tract.
Experiments on the toxicity of potassium iodate in animals have made it possible to observe that in fasting dogs, at doses of 0.2-0.25 g / kg of body weight, administered orally, the compound causes vomiting.
If these vomiting are avoided, it causes a worsening of their situation in the animals, since anorexia and prostration are induced prior to death. His autopsies revealed necrotic lesions in the liver, kidneys and intestinal mucosa.
Due to its oxidizing power, it represents a fire hazard when in contact with flammable materials.