Exceeding the Tolerable Upper Intake Level of 400 micrograms per day can lead to selenosis. Part 34. [82] There are, however, a few species that have been seen to survive these events and tolerate the increased selenium. Zinc selenide was the first material for blue LEDs, but gallium nitride dominates that market. Three days later, a pharmacy released a statement explaining that the horses had received an incorrect dose of one of the ingredients used in a vitamin/mineral supplement compound that had been incorrectly prepared by a compounding pharmacy. [7], The most stable and dense form of selenium is gray and has a hexagonal crystal lattice consisting of helical polymeric chains, where the Se-Se distance is 237.3 pm and Se-Se-Se angle is 130.1° . Selenium is a chemical element with the symbol Se and atomic number 34. The pyrite from the Falun Mine created a red precipitate in the lead chambers which was presumed to be an arsenic compound, so the pyrite's use to make acid was discontinued. [116] Selenium also occurs in organic compounds, such as dimethyl selenide, selenomethionine, selenocysteine and methylselenocysteine, all of which have high bioavailability and are toxic in large doses. The selenium cell was used in the photophone developed by Alexander Graham Bell in 1879. Google has many special features to help you find exactly what you're looking for. In 1954, the first hints of specific biological functions of selenium were discovered in microorganisms by biochemist, Jane Pinsent. Peaches and pears given a foliar selenium spray contained higher levels selenium and also stayed firm and ripe longer when in storage. Fish affected by selenium may experience swelling of the gill lamellae, which impedes oxygen diffusion across the gills and blood flow within the gills. Small amounts of organoselenium compounds have been used to modify the catalysts used for the vulcanization for the production of rubber.[52]. The glutathione peroxidase family of enzymes (GSH-Px) catalyze certain reactions that remove reactive oxygen species such as hydrogen peroxide and organic hydroperoxides: The thyroid gland and every cell that uses thyroid hormone use selenium, which is a cofactor for the three of the four known types of thyroid hormone deiodinases, which activate and then deactivate various thyroid hormones and their metabolites; the iodothyronine deiodinases are the subfamily of deiodinase enzymes that use selenium as the otherwise rare amino acid selenocysteine. Selenium—from Ancient Greek σελήνη (selḗnē) "Moon" – was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. [48], Selenium is most commonly produced from selenide in many sulfide ores, such as those of copper, nickel, or lead. The only stable chloride is selenium monochloride (Se2Cl2), which might be better known as selenium(I) chloride; the corresponding bromide is also known. Selenium was also recognized as an important veterinary toxin, which is seen in animals that have eaten high-selenium plants. This smell was not typical of arsenic, but a similar odor was known from tellurium compounds. [42][43] Ocean water contains significant amounts of selenium. In X-ray crystallography, incorporation of one or more selenium atoms in place of sulfur helps with multiple-wavelength anomalous dispersion and single wavelength anomalous dispersion phasing. Inorganic selenium bioaccumulates more readily in phytoplankton than zooplankton. – DHS Chemicals of Interest 1 1 The acronyms used in this appendix have the following meaning: ACG = A Commercial Grade; APA = A Placarded Amount; CW/CWP = Chemical Weapons/Chemical Weapons Precursors; WME = Weapons of Mass Effect; EXP/IEDP = Explosives/Improvised Explosive Device Precursors Chemicals of Interest (COI) Synonym Security Issue: Chemical … Polylactic acid, or polylactide (PLA) is a thermoplastic polyester with backbone formula (C 3 H 4 O 2) n or [–C(CH 3)HC(=O)O–] n, formally obtained by condensation of lactic acid C(CH 3)(OH)HCOOH with loss of water (hence its name). [118] The resultant high selenium levels in waterways were found to cause congenital disorders in oviparous species, including wetland birds[119] and fish. Analysis of blood levels of inorganic compounds in the supplement indicated the selenium concentrations were 10 to 15 times higher than normal in the blood samples, and 15 to 20 times higher than normal in the liver samples. Illustrative selenides include mercury selenide (HgSe), lead selenide (PbSe), zinc selenide (ZnSe), and copper indium gallium diselenide (Cu(Ga,In)Se2). Especially common are selenides (R2Se, analogues of thioethers), diselenides (R2Se2, analogues of disulfides), and selenols (RSeH, analogues of thiols). [97], Trace elements involved in GSH-Px and superoxide dismutase enzymes activities, i.e. These include silver selenite (Ag2SeO3) and sodium selenite (Na2SeO3). [42][43], In living systems, selenium is found in the amino acids selenomethionine, selenocysteine, and methylselenocysteine. [6], Analogous to the behavior of other chalcogens, selenium forms hydrogen selenide, H2Se. Selenium transmits an electric current proportional to the amount of light falling on its surface. Nearly 200 years ago, Alexis St. Martin was shot in the stomach. Increasing cAMP production in the proximal tubular cells and the medullary part of the thick ascending limb of the loop of Henle inhibits the Na+-H+ exchanger and the Na+,K+-ATPase pump. [20] Alkali metal selenides react with selenium to form polyselenides, Se2−n, which exist as chains. They all have relatively low, monoclinic crystal symmetries and contain nearly identical puckered Se8 rings with different arrangements, as in sulfur. In low doses, selenium has shown a beneficial effect on plant resistance to various environmental stress factors including drought, UV-B, soil salinity, and cold or hot temperatures. [117], Selenium poisoning of water systems may result whenever new agricultural runoff courses through normally dry, undeveloped lands. [96] Marine organisms retained and sometimes expanded their selenoproteomes, whereas the selenoproteomes of some terrestrial organisms were reduced or completely lost. The selenocysteine-containing form occurs in species as diverse as green algae, diatoms, sea urchins, fish, and chickens. [128], Selenium deficiency, defined by low (<60% of normal) selenoenzyme activity levels in brain and endocrine tissues, occurs only when a low selenium level is linked with an additional stress, such as high exposures to mercury[129] or increased oxidant stress from vitamin E deficiency. Anthony G. M. Barrett, Derek H. R. Barton, Richard A. Russell and David A. Widdowson Abstract. It is more acidic than H2S. Selenium pollution is impacting oceans across the world and is mainly caused by anthropogenic factors such as farming runoff and industrial processes. A few of these appeared more recently, in the last 50–200 million years, in fruits and flowers of angiosperm plants. [23], Selenium reacts with cyanides to yield selenocyanates:[6], Selenium, especially in the II oxidation state, forms stable bonds to carbon, which are structurally analogous to the corresponding organosulfur compounds. The minimum distance between chains is 343.6 pm. Reactions of methylindoles and 2,5-dimethylpyrrole with allenic carbenes . Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. [12] Isotopes lighter than the stable isotopes primarily undergo beta plus decay to isotopes of arsenic, and isotopes heavier than the stable isotopes undergo beta minus decay to isotopes of bromine, with some minor neutron emission branches in the heaviest known isotopes. Chemical - Part 4 is a Quest in Escape from Tarkov. [109], Although selenium is an essential trace element, it is toxic if taken in excess. With highly electropositive metals, such as aluminium, these selenides are prone to hydrolysis:[6]. This coal was shown to have selenium content as high as 9.1%, the highest concentration in coal ever recorded.[113]. These COI are categorized under three main security issues: Release: Toxic, flammable, or explosive chemicals or materials that can be released at a facility. [81] With so many humans consuming fish as a source of protein, it is important to be aware of the selenium pollution occurring in the oceans they get their fish from so we know what we are putting in our bodies. Part 34. Copper indium gallium selenide is a material used in solar cells. Chemical Watch empowers our members to transform product safety management and unlock the full value of regulatory compliance within their business. Selenium as a dietary supplement is available in many forms, including multi-vitamins/mineral supplements, which typically contain 55 or 70 µg/serving. [74], Selenium is used in the toning of photographic prints, and it is sold as a toner by numerous photographic manufacturers. From about 500 million years ago, freshwater and terrestrial plants slowly optimized the production of "new" endogenous antioxidants such as ascorbic acid (vitamin C), polyphenols (including flavonoids), tocopherols, etc. [106], The selenium content in the human body is believed to be in the 13–20 mg range. National Research Council, Committee on Nutrient Requirements of Small Ruminants (2007). Selenium dichloride is an important reagent in the preparation of selenium compounds (e.g. By contrast, selenates and selenites have an oxidant mode of action similar to that of arsenic trioxide and are very toxic. The recoding mechanism was worked out first in bacteria and then in mammals (see SECIS element).[40]. LEARN MORE Discover what our award-winning news, invaluable tools and resources, international events, custom intelligence and insights, and class leading platform can do for you. Selenium does not exhibit the changes in viscosity that sulfur undergoes when gradually heated. Selenous acid is bubbled with sulfur dioxide (reduction step) to give elemental selenium. Its use as a photoconductor in plain-paper copiers once was a leading application, but in the 1980s, the photoconductor application declined (although it was still a large end-use) as more and more copiers switched to organic photoconductors. Hence, Berzelius's first letter to Alexander Marcet stated that this was a tellurium compound. Indian Standard. Selenium forms two oxides: selenium dioxide (SeO2) and selenium trioxide (SeO3). [41] Isolation of selenium is often complicated by the presence of other compounds and elements. This color cancels out the green or yellow tints that arise from iron impurities typical for most glass. selenium, vanadium, magnesium, copper, and zinc, may have been lacking in some terrestrial mineral-deficient areas. Another source was the mud from the lead chambers of sulfuric acid plants, a process that is no longer used. In high concentrations, selenium acts as an environmental contaminant. [112] In China, people who ingested corn grown in extremely selenium-rich stony coal (carbonaceous shale) have suffered from selenium toxicity. [83], Although it is toxic in large doses, selenium is an essential micronutrient for animals. Some analytical techniques are capable of distinguishing organic from inorganic forms of the element. Signs and symptoms of selenosis include a garlic odor on the breath, gastrointestinal disorders, hair loss, sloughing of nails, fatigue, irritability, and neurological damage. This phenomenon was used in the design of light meters and similar devices. [33][34][35] These lasted in commercial applications until the 1970s, following which they were replaced with less expensive and even more efficient silicon rectifiers. [130], Selenium interacts with other nutrients, such as iodine and vitamin E. The effect of selenium deficiency on health remains uncertain, particularly in relation to Kashin-Beck disease. [7], The red α, β, and γ forms are produced from solutions of black selenium by varying the evaporation rate of the solvent (usually CS2). [25] Both chemists owned a chemistry plant near Gripsholm, Sweden, producing sulfuric acid by the lead chamber process. Respiratory capacity is further reduced due to selenium binding to hemoglobin. Chemical warfare involves using the toxic properties of chemical substances as weapons. Selenium can be refined from these muds by a number of methods. IS 3025-34 (1988): Methods of sampling and test (physical and chemical) for water and wastewater, Part 34: Nitrogen [CHD 32: Environmental Protection and Waste Management] ‘UDC 628’11.3 : 543’37 ( First Reprint APRIL 1992 ) IS : 3025 ( Part 34 ) - 1988. Kolaflavanone, a new biflavanone from the nuts of Garcinia kola Heckel. [131] Also, selenium interacts with other minerals, such as zinc and copper. [110] This 400 µg Tolerable Upper Intake Level is based primarily on a 1986 study of five Chinese patients who exhibited overt signs of selenosis and a follow up study on the same five people in 1992. Berzelius and Gahn wanted to use the pyrite and they also observed that the red precipitate gave off a smell like horseradish when burned. Substantial physiological changes may occur in fish with high tissue concentrations of selenium. Name of Legally Binding Document: 3025 (Part 34): Method of Sampling and Test (Physical and Chemical) for Water and Wastewater, Part 34: Nitrogen (First Revision) Name of Standards Organization: Bureau of Indian Standards (BIS) LEGALLY BINDING DOCUMENT. [55][57], The largest commercial use of Se, accounting for about 50% of consumption, is for the production of glass. the preparation of Se7). It is recommended that a water concentration of 2 μg Se/L be considered highly hazardous to sensitive fish and aquatic birds. #Class 7 #Standard 7 # Changes: Physical and Chemical #General Science # Maharashtra State Board It is prepared by treating selenium with sulfuryl chloride (SO2Cl2). It has an approximate composition of SeS2, with individual rings varying in composition, such as Se4S4 and Se2S6. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. Whereas other Se forms are insulators, gray Se is a semiconductor showing appreciable photoconductivity. The consumption in 2010 was divided as follows: metallurgy – 30%, glass manufacturing – 30%, agriculture – 10%, chemicals and pigments – 10%, and electronics – 10%. The lithium–selenium (Li–Se) battery is one of the most promising systems for energy storage in the family of lithium batteries. Se compounds confer a red color to glass. [71] Cadmium selenide was an important component in quantum dots. The factors that influence the solubility of gases and vapours in water at 298 K, and a new method for its determination . [24], Selenium (Greek σελήνη selene meaning "Moon") was discovered in 1817 by Jöns Jacob Berzelius and Johan Gottlieb Gahn. In fact, the angiosperms (the dominant type of plant today) and most of their antioxidant pigments evolved during the late Jurassic period. Five of these, 74Se, 76Se, 77Se, 78Se, 80Se, are stable, with 80Se being the most abundant (49.6% natural abundance). In these compounds, selenium plays a role analogous to that of sulfur. For every tonne of manganese, an average 2 kg selenium oxide is used. [100][101][102][103], Dietary selenium comes from meat, nuts, cereals and mushrooms. A previous sharp increase was observed in 2004 from $4–$5 to $27/lb. High doses of Se supplements in pregnant animals might disturb the Zn:Cu ratio and lead to Zn reduction; in such treatment cases, Zn levels should be monitored. Iodides of selenium are not well known. [120] Elevated dietary methylmercury levels can amplify the harm of selenium toxicity in oviparous species. pH-dependent plant pigments that can be used as pH indicators occur in many plants, including hibiscus, red cabbage (anthocyanin), and grapes ().The juice of citrus fruits is acidic mainly because it contains citric acid.Other carboxylic acids occur in many living systems. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot. )[108], Selenium may be measured in blood, plasma, serum, or urine to monitor excessive environmental or occupational exposure, to confirm a diagnosis of poisoning in hospitalized victims, or investigate a suspected case of fatal overdose. Further concentration through bioaccumulation occurs along the food chain, as predators consume selenium rich prey. [82] To help reduce the amount of selenium entering our oceans, policies can be put into place such as using microbes or enzymes that target and break down metalloids like selenium. [38][39] In the 1970s, it was shown to be present in two independent sets of enzymes. [5] See more on plant nutrition below. [65] These detectors use amorphous selenium to capture and convert incident x-ray photons directly into electric charge.[66]. National Research Council, Subcommittee on Sheep Nutrition (1985). During the 1980s, selenocysteine was shown to be encoded by the codon UGA. [46][47], Anthropogenic sources of selenium include coal burning, and the mining and smelting of sulfide ores. Hydrogen sulfide reacts with aqueous selenous acid to produce selenium disulfide: Selenium disulfide consists of 8-membered rings. Phytoplankton can concentrate inorganic selenium by a factor of 3000. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 0.2 mg/m3 over an 8-hour workday. The main selenium indicator plants are Astragalus species (including some locoweeds), prince's plume (Stanleya sp. In Belews Lake North Carolina, 19 species of fish were eliminated from the lake due to 150-200 μg Se/L wastewater discharged from 1974 to 1986 from a Duke Energy coal-fired power plant. It is a strongly odiferous, toxic, and colorless gas. Previous Article Next Article. The selenide dianion Se2− forms a variety of compounds, including the minerals from which selenium is obtained commercially. In humans, selenium is a trace element nutrient that functions as cofactor for reduction of antioxidant enzymes, such as glutathione peroxidases[84] and certain forms of thioredoxin reductase found in animals and some plants (this enzyme occurs in all living organisms, but not all forms of it in plants require selenium). The high bioaccumulation of selenium in aquatic environments cause large fish kills depending on the species in the affected area. The chief commercial uses for selenium today are glassmaking and pigments. Watch Chemistry Chemical Bonding part 34 (Numerical) CBSE class 11 XI - dogbzock on Dailymotion I am going to show you how to complete chemical part 3 for skier in escape from tarkov. Another naturally occurring organoselenium compound is dimethyl selenide. [6][8], Owing to its use as a photoconductor in flat-panel x-ray detectors (see below), the optical properties of amorphous selenium (α-Se) thin films have been the subject of intense research.[9][10][11]. Their use continued into the 1990s. [75][76][77], 75Se is used as a gamma source in industrial radiography.[78]. [30][31][32] The development of selenium rectifiers began during the early 1930s, and these replaced copper oxide rectifiers because they were more efficient.