About half of all produced<unk>  goes into various organoiodine compounds, another 15% remains as the pure element, another 15% is used to form potassium<unk> , and another 15% for other inorganic<unk>  compounds. Among the major uses of<unk>  compounds are catalysts, animal feed supplements, stabilisers, dyes, colourants and pigments, pharmaceutical, sanitation (from tincture of<unk> , and photography; minor uses include smog inhibition, cloud seeding, and various uses in analytical chemistry. Chemical analysis Testing a seed for starch with a solution of<unk>  The<unk>  and iodate anions are often used for quantitative volumetric analysis, for example in iodometry.<unk>  and starch form a blue complex, and this reaction is often used to test for either starch or<unk>  and as an indicator in iodometry. The<unk>  test for starch is still used to detect counterfeit banknotes printed on starch-containing paper. The<unk>  value is the mass of<unk>  in grams that is consumed by 100 grams of a chemical substance typically fats or oils.<unk>  numbers are often used to determine the amount of unsaturation in fatty acids. This unsaturation is in the form of double bonds, which react with<unk>  compounds. In biology, linoleic acid (C18:2 n-6), omega-6 and alpha-linolenic (C18:3 n-3) omega-3, arachidonic acid (AA) – omega-6 (C20: 4n-6), and docosahexaenoic acid (DHA) – omega-3 (C22:6n-3) synthesised with<unk>  iodolipids developed among cell membranes during the evolution of life, important in the mechanism of apoptosis, carcinogenesis and degenerative diseases. Potassium tetraiodomercurate(II), K2HgI4, is also known as Nessler's reagent. It is often used as a sensitive spot test for ammonia. Similarly, Cu2HgI4 is used as a precipitating reagent to test for alkaloids. Aqueous alkaline<unk>  solution is used in the iodoform test for methyl ketones. Spectroscopy The spectra of the<unk>  molecule,<unk> , consists of (not exclusively) tens of thousands of sharp spectral lines in the wavelength range 500–700 nm. It is therefore a commonly used wavelength reference (secondary standard). By measuring with a spectroscopic Doppler-free technique while focusing on one of these lines, the hyperfine structure of the<unk>  molecule reveals itself. A line is now resolved such that either 15 components, (from even rotational quantum numbers, Jeven), or 21 components (from odd rotational quantum numbers, Jodd) are measurable. Cesium<unk>  and thallium-doped sodium<unk>  are used in crystal scintillators for the detection of gamma rays. The efficiency is high and energy dispersive spectroscopy is possible, but the resolution is rather poor. Spacecraft propulsion In early 2021, French group ThrustMe performed an in-orbit demonstration of an electric-powered ion thruster for spacecraft, where<unk>  was used in lieu of xenon as the source of plasma, in order to generate thrust by accelerating ions with an electrostatic field. Propulsion systems employing<unk>  as the propellant can be built more compactly, with less mass (and cost), and operate more efficiently than the gridded ion thrusters that were utilised to propel previous spacecraft, such as Japan's Hayabusa probes, the ESA's GOCE satellite, or NASA's DART mission, all of which used xenon as the reaction mass. Yet<unk> 's atomic weight is only 3.3% less than that of xenon, while its first two ionisation energies average 12% less; together, these make<unk>  ions a promising substitute. Use of<unk>  should allow more widespread application of ion-thrust technology, particularly with smaller-scale space vehicles. According to the European Space Agency, "This small but potentially disruptive innovation could help to clear the skies of space junk, by enabling tiny satellites to self-destruct cheaply and easily at the end of their missions, by steering themselves into the atmosphere where they would burn up." Medicine Elemental<unk>  Elemental<unk>  is used as an antiseptic either as the element, or as the water-soluble triiodide anion I3− generated in situ by adding<unk>  to poorly water-soluble elemental<unk>  (the reverse chemical reaction makes some free elemental<unk>  available for antisepsis). Elemental<unk>  may also be used to treat<unk>  deficiency. In the alternative,<unk>  may be produced from iodophors, which contain<unk>  complexed with a solubilizing agent (the<unk>  ion may be thought of loosely as the iodophor in triiodide water solutions). Examples of such preparations include: * Tincture of<unk> :<unk>  in ethanol, or<unk>  and sodium<unk>  in a mixture of ethanol and water. * Lugol's<unk> :<unk>  and<unk>  in water alone, forming mostly triiodide. Unlike tincture of<unk> , Lugol's<unk>  has a minimised amount of the free<unk>  <unk>  component. * Povidone<unk>  (an iodophor). The antimicrobial action of<unk>  is quick and works at low concentrations, and thus it is used in operating theatres. Its specific mode of action is unknown. It penetrates into microorganisms and attacks particular amino acids (such as cysteine and methionine), nucleotides, and fatty acids, ultimately resulting in cell death. It also has an antiviral action, but nonlipid viruses and parvoviruses are less sensitive than lipid enveloped viruses.<unk>  probably attacks surface proteins of enveloped viruses, and it may also destabilise membrane fatty acids by reacting with unsaturated carbon bonds. Other formulations In medicine, a saturated solution of potassium<unk>  is used to treat acute thyrotoxicosis. It is also used to block uptake of<unk> -131 in the thyroid gland (see isotopes section above), when this isotope is used as part of radiopharmaceuticals (such as iobenguane) that are not targeted to the thyroid or thyroid-type tissues.<unk> -131 (usually as<unk>  is a component of nuclear fallout, and is particularly dangerous owing to the thyroid gland's propensity to concentrate ingested<unk>  and retain it for periods longer than this isotope's radiological half-life of eight days. For this reason, people at risk of exposure to environmental radioactive<unk> <unk> -131) in fallout may be instructed to take non-radioactive potassium<unk>  tablets. The typical adult dose is one 130 mg tablet per 24 hours, supplying 100 mg (100,000 micrograms) of ionic<unk> . (The typical daily dose of<unk>  for normal health is of order 100 micrograms; see "Dietary Intake" below.) Ingestion of this large dose of non-radioactive<unk>  minimises the uptake of radioactive<unk>  by the thyroid gland. Diatrizoic acid, an<unk> -containing radiocontrast agent As an element with high electron density and atomic number,<unk>  absorbs X-rays weaker than 33.3 keV due to the photoelectric effect of the innermost electrons. Organoiodine compounds are used with intravenous injection as X-ray radiocontrast agents. This application is often in conjunction with advanced X-ray techniques such as angiography and CT scanning. At present, all water-soluble radiocontrast agents rely on<unk> . Others The production of ethylenediamine dihydroiodide, provided as a nutritional supplement for livestock, consumes a large portion of available<unk> . Another significant use is a catalyst for the production of acetic acid by the Monsanto and Cativa processes. In these technologies, which support the world's demand for acetic acid, hydroiodic acid converts the methanol feedstock into methyl<unk> , which undergoes carbonylation. Hydrolysis of the resulting acetyl<unk>  regenerates hydroiodic acid and gives acetic acid. Inorganic<unk> s find specialised uses. Titanium, zirconium, hafnium, and thorium are purified by the van Arkel–de Boer process, which involves the reversible formation of the tetraiodides of these elements. Silver<unk>  is a major ingredient to traditional photographic film. Thousands of kilograms of silver<unk>  are used annually for cloud seeding to induce rain. The organoiodine compound erythrosine is an important food coloring agent. Perfluoroalkyl<unk> s are precursors to important surfactants, such as perfluorooctanesulfonic acid. The<unk>  clock reaction (in which<unk>  also serves as a test for starch, forming a dark blue complex), is a popular educational demonstration experiment and example of a seemingly oscillating reaction (it is only the concentration of an intermediate product that oscillates). Although<unk>  has widespread roles in many species, agents containing it can exert a differential effect upon different species in an agricultural system. The growth of all strains of Fusarium verticillioides is significantly inhibited by an<unk> -containing fungistatic (AJ1629-34EC) at concentrations that do not harm the crop. This might be a less toxic anti-fungal agricultural treatment due to its relatively natural chemistry. I is used as the radiolabel in investigating which ligands go to which plant pattern recognition receptors (PRRs).
Iodine
Lindane
Copper 
Chorus
Fluoride
Amine fluoride
Hydrogen fluoride
Sodium fluoride