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Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at 114 °C (237 °F), and boils to a violet gas at 184 °C (363 °F). The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek Ιώδης, meaning 'violet'.
The Winkler test is used to determine the concentration of dissolved oxygen in water samples. Dissolved oxygen (D.O.) is widely used in water quality studies and routine operation of water reclamation facilities to analyze its level of oxygen saturation.
Potassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer when the solid is heated at high temperature although it usually reacts very slowly in solution with reducing agents or organic substances. This colorless crystalline solid is a common oxidizer used in fireworks, ammunition percussion caps, explosive primers, and is used variously in propellants, flash compositions, stars, and sparklers. It has been used as a solid rocket propellant, although in that application it has mostly been replaced by the more performant ammonium perchlorate.
Sodium thiosulfate is an inorganic compound with the formula Na2S2O3·(H2O)(x). Typically it is available as the white or colorless pentahydrate. It is a white solid that dissolves well in water. The compound is a reducing agent and a ligand, and these properties underpin its applications.
In chemistry, the iodine value is the mass of iodine in grams that is consumed by 100 grams of a chemical substance. Iodine numbers are often used to determine the degree of unsaturation in fats, oils and waxes. In fatty acids, unsaturation occurs mainly as double bonds which are very reactive towards halogens, the iodine in this case. Thus, the higher the iodine value, the more unsaturations are present in the fat. It can be seen from the table that coconut oil is very saturated, which means it is good for making soap. On the other hand, linseed oil is highly unsaturated, which makes it a drying oil, well suited for making oil paints.
Hydrogen iodide (HI) is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under standard conditions, whereas the other is an aqueous solution of the gas. They are interconvertible. HI is used in organic and inorganic synthesis as one of the primary sources of iodine and as a reducing agent.
An iodate is the polyatomic anion with the formula IO−3. It is the most common form of iodine in nature, as it comprises the major iodine-containing ores. Iodate salts are often colorless. They are the salts of iodic acid.
Iodic acid is a white water-soluble solid with the chemical formula HIO3. Its robustness contrasts with the instability of chloric acid and bromic acid. Iodic acid features iodine in the oxidation state +5 and is one of the most stable oxo-acids of the halogens. When heated, samples dehydrate to give iodine pentoxide. On further heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine.
Iodometry, known as iodometric titration, is a method of volumetric chemical analysis, a redox titration where the appearance or disappearance of elementary iodine indicates the end point.
The bisulfite ion (IUPAC-recommended nomenclature: hydrogensulfite) is the ion HSO−
3. Salts containing the HSO−
3 ion are also known as "sulfite lyes". Sodium bisulfite is used interchangeably with sodium metabisulfite (Na2S2O5). Sodium metabisulfite dissolves in water to give a solution of Na+HSO−
3.
The Old Nassau reaction or Halloween reaction is a chemical clock reaction in which a clear solution turns orange and then black. This reaction was discovered by two undergraduate students at Princeton University researching the inhibition of the iodine clock reaction (or Landolt reaction) by Hg2+, resulting in the formation of orange HgI2. Orange and black are the school colors of Princeton University, and "Old Nassau" is a nickname for Princeton, named for its historic administration building, Nassau Hall.
The Briggs–Rauscher oscillating reaction is one of a small number of known oscillating chemical reactions. It is especially well suited for demonstration purposes because of its visually striking colour changes: the freshly prepared colourless solution slowly turns an amber colour, then suddenly changes to a very dark blue. This slowly fades to colourless and the process repeats, about ten times in the most popular formulation, before ending as a dark blue liquid smelling strongly of iodine.
Thiosulfate is an oxyanion of sulfur with the chemical formula S2O2−3. Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, such as sodium thiosulfate Na2S2O3 and ammonium thiosulfate (NH4)2S2O3. Thiosulfate salts occur naturally. It rapidly dechlorinates water and is notable for its use to halt bleaching in the paper-making industry. Thiosulfate salts are mainly used in dying in textiles and the bleaching of natural substances.
Potassium iodate (KIO3) is an ionic inorganic compound with the formula KIO3. It is a white salt that is soluble in water.
Sodium iodate (NaIO3) is the sodium salt of iodic acid. Sodium iodate is an oxidizing agent. It has several uses.
Iodine monochloride is an interhalogen compound with the formula ICl. It is a red-brown chemical compound that melts near room temperature. Because of the difference in the electronegativity of iodine and chlorine, this molecule is highly polar and behaves as a source of I+. Discovered in 1814 by Gay-Lussac, iodine monochloride is the first interhalogen compound discovered.
Iodine compounds are compounds containing the element iodine. Iodine can form compounds using multiple oxidation states. Iodine is quite reactive, but it is much less reactive than the other halogens. For example, while chlorine gas will halogenate carbon monoxide, nitric oxide, and sulfur dioxide, iodine will not do so. Furthermore, iodination of metals tends to result in lower oxidation states than chlorination or bromination; for example, rhenium metal reacts with chlorine to form rhenium hexachloride, but with bromine it forms only rhenium pentabromide and iodine can achieve only rhenium tetraiodide. By the same token, however, since iodine has the lowest ionisation energy among the halogens and is the most easily oxidised of them, it has a more significant cationic chemistry and its higher oxidation states are rather more stable than those of bromine and chlorine, for example in iodine heptafluoride.
A disulfite, commonly known as metabisulfite or pyrosulfite, is a chemical compound containing the ion S
2O2−
5. It is a colorless dianion that is primarily marketed in the form of sodium metabisulfite or potassium metabisulfite. When dissolved in water, these salts release the hydrogensulfite HSO−
3 anion. These salts act equivalently to sodium hydrogensulfite or potassium hydrogensulfite.
Polythionates are oxyanions with the formula −O3S−Sn−SO−3 (n ≥ 0). They occur naturally and are the products of redox reactions of thiosulfate. Polythionates are readily isolable, unlike the parent polythionic acids.
Astatine compounds are compounds that contain the element astatine (At). As this element is very radioactive, few compounds have been studied. Less reactive than iodine, astatine is the least reactive of the halogens. Its compounds have been synthesized in nano-scale amounts and studied as intensively as possible before their radioactive disintegration. The reactions involved have been typically tested with dilute solutions of astatine mixed with larger amounts of iodine. Acting as a carrier, the iodine ensures there is sufficient material for laboratory techniques to work. Like iodine, astatine has been shown to adopt odd-numbered oxidation states ranging from −1 to +7.
References
- ↑ See:
- Landolt, H. (1886). "Ueber die Zeitdauer der Reaction zwischen Jodsäure und schwefliger Säure" [On the duration of the reaction between iodic acid and sulfurous acid]. Berichte der Deutschen Chemischen Gesellschaft (in German). 19 (1): 1317–1365. doi:10.1002/cber.188601901293.
- Landolt, H. (1887). "Ueber die Zeitdauer der Reaction zwischen Jodsäure und schwefliger Säure [Part 2]" [On the duration of the reaction between iodic acid and sulfurous acid]. Berichte der Deutschen Chemischen Gesellschaft (in German). 20 (1): 745–760. doi:10.1002/cber.188702001173.
- ↑ Limpanuparb, T.; Ruchawapol, C.; Sathainthammanee, D. (2019). "Clock Reaction Revisited: Catalyzed Redox Substrate-Depletive Reactions". Journal of Chemical Education. 96 (4): 812–818. Bibcode:2019JChEd..96..812L. doi:10.1021/acs.jchemed.8b00547. S2CID 104370691.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ "Experiment 6: THE RATE LAWS OF AN IODINE CLOCK REACTION" (PDF). Archived from the original (PDF) on 2018-05-17. Retrieved 2018-04-30.
- ↑ Hugh Cartwright (2006). "Kinetics of the Persulfate-iodide Clock Reaction" (PDF). 2nd/3rd Year Physical Chemistry Practical Course. Oxford University. Retrieved 25 March 2018.
- ↑ André P. Oliveira and Roberto B. Faria (2005). "The chlorate-iodine clock reaction". J. Am. Chem. Soc. 127 (51): 18022–18023. doi:10.1021/ja0570537. PMID 16366551.