Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive, as it reacts with all other elements, except for argon, neon, and helium. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite , the primary mineral source of fluorine which gave the element its name, was first described in ; as it was added to metal ores to lower their melting points for smelting , the Latin verb fluo meaning "flow" gave the mineral its name. Proposed as an element in , fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis , a process still employed for modern production.
Whether in a dry Egyptian tomb or buried in wet tropical soil, a piece of obsidian seemingly has a surface that is saturated with a molecular film of water. Consequently, the key to absolute dating of obsidian is to evaluate K for different temperatures. Even without such knowledge, hydration rims are useful for relative dating within a region of uniform climate. Like most absolute chronometers, obsidian dating has its problems and limitations.
Specimens that have been exposed to fire or to severe abrasion must be avoided. Furthermore, artifacts reused repeatedly do not give ages corresponding to the culture layer in which they were found but instead to an earlier time, when they were fashioned.
Finally, there is the problem that layers may flake off beyond 40 micrometres 0. Measuring several slices from the same specimen is wise in this regard, and such a procedure is recommended regardless of age.
Sediment in former or present water bodies, salt dissolved in the oceanand fluorine in bones are three kinds of natural accumulations and possible time indicators. To serve as geochronometers, the records must be complete and the accumulation rates known.
Other articles where Fluorine dating is discussed: geochronology: Accumulational processes: Fluorine dating is therefore not the simple procedure that Middleton envisioned. Fluorine dating is therefore not the simple procedure that Middleton envisioned. Still, the idea that hydroxyapatite in buried bone undergoes gradual change to fluorapatite is a correct one. In a restricted locality where there is uniformity of climate and soil, the extent of fluorine addition is at least a measure of relative age and has been. fluorine-dating definition: Noun (plural fluorine datings) 1. (archaeology) A technique used to date bones by measuring the amount of fluorine absorbed from the surrounding soil.
The fossiliferous part of the geologic column includes perhapsmetres of sedimentary rock if maximum thicknesses are selected from throughout the world. During the late s, attempts were made to estimate the time over which it formed by assuming an average rate of sedimentation.
Because there was great diversity among the rates assumed, the range of estimates was also large-from a high of 2. In spite of this tremendous spread, most geologists felt that time in the hundreds of millions of years was necessary to explain the sedimentary record.
If the geologic column see below were made up entirely of annual layers, its duration would be easy to determine. Varves arise in response to seasonal changes. In moist, temperate climates, lake sediments collecting in the summer are richer in organic matter than those that settle during winter. This feature is beautifully seen in the seasonal progression of plant microfossils found in shales at Oensingen, Switz.
In the thick oil shales of Wyoming and Colorado in the United States, the flora is not so well defined, but layers alternating in organic richness seem to communicate the same seasonal cycle. These so-called Green River Shales also contain abundant freshwater-fish fossils that confirm deposition in a lake. At their thickest, they span vertical metres. InGeorgius Agricola described fluorite as an additive used to lower the melting point of metals during smelting.
The name later evolved into fluorspar still commonly used and then fluorite. Hydrofluoric acid was used in glass etching from onwards. Initial studies on fluorine were so dangerous that several 19th-century experimenters were deemed "fluorine martyrs" after misfortunes with hydrofluoric acid. To prevent rapid corrosion of the platinum in his electrochemical cellshe cooled the reaction to extremely low temperatures in a special bath and forged cells from a more resistant mixture of platinum and iridiumand used fluorite stoppers.
Intwo months before his death, Moissan received the Nobel Prize in Chemistry with the following citation: .
The whole world has admired the great experimental skill with which you have studied that savage beast among the elements. It replaced earlier and more toxic compounds, increased demand for kitchen refrigerators, and became profitable; by DuPont had bought out Kinetic and marketed several other Freon compounds.
Plunkett while working on refrigerants at Kinetic, and its superlative chemical and thermal resistance lent it to accelerated commercialization and mass production by Large-scale production of elemental fluorine began during World War II. Germany used high-temperature electrolysis to make tons of the planned incendiary chlorine trifluoride  and the Manhattan Project used huge quantities to produce uranium hexafluoride for uranium enrichment.
Since UF 6 is as corrosive as fluorine, gaseous diffusion plants required special materials: nickel for membranes, fluoropolymers for seals, and liquid fluorocarbons as coolants and lubricants.
This burgeoning nuclear industry later drove post-war fluorochemical development. Fluorine has a rich chemistry, encompassing organic and inorganic domains. Alkali metals form ionic and highly soluble monofluorides ; these have the cubic arrangement of sodium chloride and analogous chlorides. Hydrogen and fluorine combine to yield hydrogen fluoride, in which discrete molecules form clusters by hydrogen bonding, resembling water more than hydrogen chloride.
Unlike the other hydrohalic acids, which are stronghydrofluoric acid is a weak acid at low concentrations. Binary fluorides of metalloids and p-block nonmetals are generally covalent and volatile, with varying reactivities. Period 3 and heavier nonmetals can form hypervalent fluorides. Boron trifluoride is planar and possesses an incomplete octet. It functions as a Lewis acid and combines with Lewis bases like ammonia to form adducts.
The latter are stabilized by more fluorine atoms and lighter central atoms, so sulfur hexafluoride is especially inert. Noble gaseshaving complete electron shells, defied reaction with other elements until when Neil Bartlett reported synthesis of xenon hexafluoroplatinate ; xenon difluoridetetrafluoridehexafluorideand multiple oxyfluorides have been isolated since then.
The carbon-fluorine bond is organic chemistry 's strongest, and gives stability to organofluorines. Research in this area is usually driven by commercial applications; the compounds involved are diverse and reflect the complexity inherent in organic chemistry.
The substitution of hydrogen atoms in an alkane by progressively more fluorine atoms gradually alters several properties: melting and boiling points are lowered, density increases, solubility in hydrocarbons decreases and overall stability increases. Perfluorocarbons, [note 16] in which all hydrogen atoms are substituted, are insoluble in most organic solvents, reacting at ambient conditions only with sodium in liquid ammonia.
The term perfluorinated compound is used for what would otherwise be a perfluorocarbon if not for the presence of a functional group[note 17] often a carboxylic acid.
These compounds share many properties with perfluorocarbons such as stability and hydrophobicitywhile the functional group augments their reactivity, enabling them to adhere to surfaces or act as surfactants ; Fluorosurfactantsin particular, can lower the surface tension of water more than their hydrocarbon-based analogues.
Fluorotelomerswhich have some unfluorinated carbon atoms near the functional group, are also regarded as perfluorinated. Polymers exhibit the same stability increases afforded by fluorine substitution for hydrogen in discrete molecules; their melting points generally increase too. Elemental fluorine and virtually all fluorine compounds are produced from hydrogen fluoride or its aqueous solutions, hydrofluoric acid.
These species are produced by treatment of fluorite CaF 2 with sulfuric acid:. KF, which acts as catalyst, is essential since pure HF cannot be electrolyzed. In the laboratory, glassware may carry fluorine gas under low pressure and anhydrous conditions; some sources instead recommend nickel-Monel-PTFE systems.
While preparing for a conference to celebrate the centennial of Moissan's achievement, Karl O. Christe reasoned that chemical fluorine generation should be feasible since some metal fluoride anions have no stable neutral counterparts; their acidification potentially triggers oxidation instead. He devised a method which evolves fluorine at high yield and atmospheric pressure:.
Christe later commented that the reactants "had been known for more than years and even Moissan could have come up with this scheme. Fluorite mining, which supplies most global fluorine, peaked in when 5. Chlorofluorocarbon restrictions lowered this to 3. Around 4. Most processes using free fluorine in large amounts employ in situ generation under vertical integration. Fluorine is used to fluorinate uranium tetrafluorideitself formed from uranium dioxide and hydrofluoric acid.
Fluorinated pharmaceuticals use sulfur tetrafluoride instead. Electrochemical fluorination subjects hydrocarbons to electrolysis in hydrogen fluoride, and the Fowler process treats them with solid fluorine carriers like cobalt trifluoride. Halogenated refrigerants, termed Freons in informal contexts, [note 18] are identified by R-numbers that denote the amount of fluorine, chlorine, carbon, and hydrogen present.
Used for air conditioning systems, propellants and solvents, their production was below one-tenth of this peak by the early s, after widespread international prohibition. It is also used in the chemical industry where corrosion resistance is needed, in coating pipes, tubing, and gaskets. Another major use is in PFTE-coated fiberglass cloth for stadium roofs.
The major consumer application is for non-stick cookware. Films from two different fluoropolymers replace glass in solar cells. The chemically resistant but expensive fluorinated ionomers are used as electrochemical cell membranes, of which the first and most prominent example is Nafion. Developed in the s, it was initially deployed as fuel cell material in spacecraft and then replaced mercury-based chloralkali process cells. Recently, the fuel cell application has reemerged with efforts to install proton exchange membrane fuel cells into automobiles.
Fluorosurfactants are small organofluorine molecules used for repelling water and stains. Fluorine substitution, usually of a single atom or at most a trifluoromethyl group, is a robust modification with effects analogous to fluorinated pharmaceuticals: increased biological stay time, membrane crossing, and altering of molecular recognition.
First synthesized in the late 19th century, it was recognized as an insecticide in the early 20th, and was later deployed in its current use. New Zealand, the largest consumer ofuses it to protect kiwis from the invasive Australian common brushtail possum. Population studies from the midth century onwards show topical fluoride reduces dental caries. This was first attributed to the conversion of tooth enamel hydroxyapatite into the more durable fluorapatite, but studies on pre-fluoridated teeth refuted this hypothesis, and current theories involve fluoride aiding enamel growth in small caries.
Twenty percent of modern pharmaceuticals contain fluorine. Tricyclics and other pres antidepressants had several side effects due to their non-selective interference with neurotransmitters other than the serotonin target; the fluorinated fluoxetine was selective and one of the first to avoid this problem. Many current antidepressants receive this same treatment, including the selective serotonin reuptake inhibitors : citalopramits isomer escitalopramand fluvoxamine and paroxetine.
These include ciprofloxacin and levofloxacin. Later compounds such as the fluorinated ethers sevoflurane and desflurane are better than halothane and are almost insoluble in blood, allowing faster waking times. Fluorine is often found in radioactive tracers for positron emission tomography, as its half-life of almost two hours is long enough to allow for its transport from production facilities to imaging centers.
Liquid fluorocarbons can hold large volumes of oxygen or carbon dioxide, more so than blood, and have attracted attention for their possible uses in artificial blood and in liquid breathing.
Partial and complete lung filling have been considered, though only the former has had any significant tests in humans.
Fluorine is not essential for humans and mammals, but small amounts are known to be beneficial for the strengthening of dental enamel where the formation of fluorapatite makes the enamel more resistant to attack, from acids produced by bacterial fermentation of sugars.
Small amounts of fluorine may be beneficial for bone strength, but the latter has not been definitively established. Natural organofluorines have been found in microorganisms and plants  but not animals. Elemental fluorine is highly toxic to living organisms. Its effects in humans start at concentrations lower than hydrogen cyanide 's 50 ppm and are similar to those of chlorine: significant irritation of the eyes and respiratory system as well as liver and kidney damage occur above 25 ppm, which is the immediately dangerous to life and health value for fluorine.
Hydrofluoric acid is the weakest of the hydrohalic acids, having a pKa of 3. It is able to attack glass, concrete, metals, organic matter. Hydrofluoric acid is a contact poison with greater hazards than many strong acids like sulfuric acid even though it is weak: it remains neutral in aqueous solution and thus penetrates tissue faster, whether through inhalation, ingestion or the skin, and at least nine U.
It reacts with calcium and magnesium in the blood leading to hypocalcemia and possible death through cardiac arrhythmia. If skin has been exposed to HF, damage can be reduced by rinsing it under a jet of water for minutes and removing contaminated clothing.
Using calcium chloride - a common laboratory reagent - in lieu of calcium gluconate is contraindicated, and may lead to severe complications. Excision or amputation of affected parts may be required. Exposure limits are determined by urine testing of the body's ability to clear fluoride ions. Historically, most cases of fluoride poisoning have been caused by accidental ingestion of insecticides containing inorganic fluorides.
The Montreal Protocolsigned inset strict regulations on chlorofluorocarbons CFCs and bromofluorocarbons due to their ozone damaging potential ODP. The high stability which suited them to their original applications also meant that they were not decomposing until they reached higher altitudes, where liberated chlorine and bromine atoms attacked ozone molecules. Organofluorines exhibit biopersistence due to the strength of the carbon-fluorine bond.
Perfluoroalkyl acids PFAAswhich are sparingly water-soluble owing to their acidic functional groups, are noted persistent organic pollutants ; perfluorooctanesulfonic acid PFOS and perfluorooctanoic acid PFOA are most often researched. A review showed a slight correlation between groundwater and soil PFAA levels and human activity; there was no clear pattern of one chemical dominating, and higher amounts of PFOS were correlated to higher amounts of PFOA. Dwell time in the body varies greatly by species, with half-lives of days in rodents, and years in humans.
From Wikipedia, the free encyclopedia. Not to be confused with fluorene or fluoride. Chemical element with atomic number 9 and a atomic mass of Chemical element with atomic number 9. Liquid fluorine at extremely low temperatures. Main article: Chemical characteristics of fluorine.
Main article: Phases of fluorine. Main article: Isotopes of fluorine. Main article: Origin and occurrence of fluorine. See also: List of countries by fluorite production. Main article: History of fluorine. Main article: Compounds of fluorine.
See also: Fluoride volatility. Main articles: Hydrogen fluoride and hydrofluoric acid. Main article: Noble gas compound. Main article: Organofluorine chemistry. Main articles: Fluorocarbon and Perfluorinated compound. Main article: Fluorochemical industry. See also: Industrial gas. See also: Refrigerant. Main article: Fluoropolymer.
Main articles: Fluorinated surfactant and Durable water repellent. Main articles: Fluoride therapyWater fluoridationand Water fluoridation controversy. Main article: Positron emission tomography. See also: Blood substitute and Liquid breathing.
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Main article: Biological cts of fluorine. Main article: Fluorine-related hazards. GHS hazard statements. See also: Chemical burn.
See also: Fluoride toxicity. See also: Ozone depletion and global warming. Main article: Biopersistence of fluorinated organics. Chemistry portal. Electrophilic and radical fluorination 19 F NMR Fluorine absorption dating Fluorous chemistrya process used to separate reagents from organic solvents Fluoride selective electrodewhich measures fluoride concentration Krypton and argon fluoride lasers.
Samples may shatter and sample windows blow out. In general the spin endows them with angular momentum and with a magnetic moment; the first because of their mass, the second because all or part of their electric charge may be rotating with the mass. Moissan also experienced serious hydrogen fluoride poisoning. Hydrogen bonding is another possibility. Pure and Applied Chemistry. Journal of Agricultural and Food Chemistry. ACS Publications. Archived from the original on 13 November Retrieved 2 January Safety data sheet".
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Aug 12, Fluorine dating is a method that measures the amount of fluoride absorbed by bones in order to determine their relative age. Unlike radiometric dating methods, it cannot provide a chronometric (or calendrical) date. Fluorine absorption dating is a method used to determine the amount of time an object has been underground. Fluorine absorption dating can be carried out based on the fact that groundwater contains fluoride ions. Items such as bone that are in the soil will absorb fluoride from the groundwater over time. From the amount of absorbed fluoride in the item, the time that the Astronomic time: Cosmic Calendar, Ephemeris, .
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Fluorine analysis can be used only as a relative dating method because the rate of decay and the amount of dissolved minerals in the ground water varies from site to site. In other words, the biochemical clock that this method relies on runs at a different rate in different environments. Fluorine dating advantages - Men looking for a woman - Women looking for a woman. Find single woman in the US with online dating. Looking for love in all the wrong places? Now, try the right place. Want to meet eligible single man who share your zest for life? Indeed, for those who've tried and failed to find the right man offline, relations can provide. Fluorine dating definition, a method of determining the relative age of fossil bones found in the same excavation by comparing their fluorine content. See more.
Barry, Patrick L. National Aeronautics and Space Administration. Retrieved 6 January Proceedings of the Chemical Society 6 : Beasley, Michael August Guidelines for the safe use of sodium fluoroacetate. Archived from the original on 11 November Retrieved 11 November Retrieved 15 October Angewandte Chemie International Edition in English.
Bioorganic and Medicinal Chemistry of Fluorine. Environmental Health Perspectives. Bihary, Z. Canon of Kings Lists of kings Limmu.
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