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59-483: The program is directed by Deborah Blum . KSJ@MIT has hosted more than 300 fellows from a wide range of national and international publications, including The New York Times , The Wall Street Journal , Forbes , Time , Scientific American , Science , the Associated Press , ABC News , and CNN . Eligible applicants can work for print, broadcast or the web as reporters, writers, editors, or producers. In 2016,

118-470: A byproduct, obtained from the anode mud of copper refineries. Another source was the mud from the lead chambers of sulfuric acid plants, a process that is no longer used. Selenium can be refined from these muds by a number of methods. However, most elemental selenium comes as a byproduct of refining copper or producing sulfuric acid . Since its invention, solvent extraction and electrowinning (SX/EW) production of copper produces an increasing share of

177-488: A chemistry plant near Gripsholm , Sweden, producing sulfuric acid by the lead chamber process . Pyrite samples from the Falun Mine produced a red solid precipitate in the lead chambers, which was presumed to be an arsenic compound, so the use of pyrite to make acid was discontinued. Berzelius and Gahn, who wanted to use the pyrite, observed that the red precipitate gave off an odor like horseradish when burned. This smell

236-499: A digital science magazine published under the auspices of the KSJ program. In July 2016, David Corcoran, former editor of Science Times at The New York Times , joined the program as a senior editor at the magazine and associate director of the program. Blum is the eldest of four daughters born to entomologist Murray S. Blum and Nancy Ann Blum, an educator and writer. Blum and her husband have two sons. Selenium Selenium

295-475: A glass dye, and a reducing agent in fireworks . Selenium trioxide may be synthesized by dehydrating selenic acid , H 2 SeO 4 , which is itself produced by the oxidation of selenium dioxide with hydrogen peroxide : Hot, concentrated selenic acid reacts with gold to form gold(III) selenate. Selenium reacts with fluorine to form selenium hexafluoride : In comparison with its sulfur counterpart ( sulfur hexafluoride ), selenium hexafluoride (SeF 6 )

354-788: A member of the governing board of the World Federation of Science Writers and has also served on such panels for the Council for the Advancement of Science Writing, the AAAS Committee on Public Understanding of Science and Technology, the National Research Council's Board on Agriculture and Natural Resources, the Society for Science & the Public and a US Congress committee on science. Blum

413-546: A non-graded, non-credit basis at MIT , Harvard University , and other nearby institutions including Boston University , Tufts University , Northeastern University , and Brandeis University . Deborah Blum Deborah Leigh Blum (born October 19, 1954) is an American science journalist and the director of the Knight Science Journalism program at the Massachusetts Institute of Technology . She

472-468: A product of nuclear fission . Selenium also has numerous unstable synthetic isotopes ranging from Se to Se; the most stable are Se with a half-life of 119.78 days and Se with a half-life of 8.4 days. 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

531-493: A ring are not equivalent (i.e. they are not mapped one onto another by any symmetry operation), and in fact in the γ-monoclinic form, half the rings are in one configuration (and its mirror image) and half in another. The packing is most dense in the α form. In the Se 8 rings, the Se–Se distance varies depending on where the pair of atoms is in the ring, but the average is 233.5 pm, and

590-488: A role analogous to that of sulfur. Another naturally occurring organoselenium compound is dimethyl selenide . Certain soils are selenium-rich, and selenium can be bioconcentrated by some plants. In soils, selenium most often occurs in soluble forms such as selenate (analogous to sulfate), which are leached into rivers very easily by runoff. Ocean water contains significant amounts of selenium. Typical background concentrations of selenium do not exceed 1 ng/m in

649-554: Is 343.6 pm. Gray selenium is formed by mild heating of other allotropes, by slow cooling of molten selenium, or by condensing selenium vapor just below the melting point. Whereas other selenium forms are insulators , gray selenium is a semiconductor showing appreciable photoconductivity . Unlike the other allotropes, it is insoluble in CS 2 . It resists oxidation by air and is not attacked by nonoxidizing acids . With strong reducing agents, it forms polyselenides. Selenium does not exhibit

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708-477: Is a chemical element ; it has the symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust . Selenium (from Ancient Greek σελήνη ( selḗnē )  'moon') was discovered in 1817 by Jöns Jacob Berzelius , who noted

767-690: Is a semiconductor and is used in photocells . Applications in electronics , once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot . Although trace amounts of selenium are necessary for cellular function in many animals, including humans, both elemental selenium and (especially) selenium salts are toxic in even small doses, causing selenosis . Symptoms include (in decreasing order of frequency): diarrhea, fatigue, hair loss, joint pain, nail brittleness or discoloration, nausea, headache, tingling, vomiting, and fever. Selenium

826-407: Is a rare mineral, which does not usually form good crystals, but, when it does, they are steep rhombohedra or tiny acicular (hair-like) crystals. Isolation of selenium is often complicated by the presence of other compounds and elements. Selenium occurs naturally in a number of inorganic forms, including selenide , selenate , and selenite , but these minerals are rare. The common mineral selenite

885-1045: Is a strongly odiferous , toxic, and colorless gas. It is more acidic than H 2 S. In solution it ionizes to HSe . The selenide dianion Se forms a variety of compounds, including the minerals from which selenium is obtained commercially. Illustrative selenides include mercury selenide (HgSe), lead selenide (PbSe), zinc selenide (ZnSe), and copper indium gallium diselenide (Cu(Ga,In)Se 2 ). These materials are semiconductors . With highly electropositive metals, such as aluminium , these selenides are prone to hydrolysis, which may be described by this idealized equation: Al 2 Se 3 + 6 H 2 O ⟶ 2 Al ( OH ) 3 + 3 H 2 Se {\displaystyle {\ce {Al2Se3 + 6 H2O -> 2 Al(OH)3 + 3 H2Se}}} Alkali metal selenides react with selenium to form polyselenides, Se n , which exist as chains and rings. Tetraselenium tetranitride, Se 4 N 4 ,

944-469: Is an explosive orange compound analogous to tetrasulfur tetranitride (S 4 N 4 ). It can be synthesized by the reaction of selenium tetrachloride (SeCl 4 ) with [((CH 3 ) 3 Si) 2 N] 2 Se . Selenium reacts with cyanides to yield selenocyanates : 8 KCN + Se 8 ⟶ 8 KSeCN {\displaystyle {\ce {8 KCN + Se8 -> 8 KSeCN}}} Selenium, especially in

1003-650: Is co-editor, with Mary Knudson and Robin Marantz Henig, of the book A Field Guide for Science Writers . Blum became director of the Knight Science Journalism Program (KSJ), a fellowship program endowed by the James S. and John L. Knight Foundation to encourage "a select breed of journalist", in July 2015. The following year, she and former New York Times reporter and columnist Tom Zeller Jr. co-founded Undark ,

1062-482: Is for the production of glass. Selenium compounds confer a red color to glass. This color cancels out the green or yellow tints that arise from iron impurities typical for most glass. For this purpose, various selenite and selenate salts are added. For other applications, a red color may be desired, produced by mixtures of CdSe and CdS. Selenium is used with bismuth in brasses to replace more toxic lead . The regulation of lead in drinking water applications such as in

1121-405: Is formed by combustion of elemental selenium: It is a polymeric solid that forms monomeric SeO 2 molecules in the gas phase. It dissolves in water to form selenous acid , H 2 SeO 3 . Selenous acid can also be made directly by oxidizing elemental selenium with nitric acid : Unlike sulfur, which forms a stable trioxide , selenium trioxide is thermodynamically unstable and decomposes to

1180-585: Is listed as an ingredient in many multivitamins and other dietary supplements, as well as in infant formula , and is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase (which indirectly reduce certain oxidized molecules in animals and some plants) as well as in three deiodinase enzymes. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts and others apparently not requiring any. Selenium forms several allotropes that interconvert with temperature changes, depending somewhat on

1239-496: Is mixed with water and acidified to form selenous acid ( oxidation step). Selenous acid is bubbled with sulfur dioxide ( reduction step) to give elemental selenium. About 2,000 tonnes of selenium were produced in 2011 worldwide, mostly in Germany (650 t), Japan (630 t), Belgium (200 t), and Russia (140 t), and the total reserves were estimated at 93,000 tonnes. These data exclude two major producers:

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1298-461: Is more reactive and is a toxic pulmonary irritant. Selenium tetrafluoride is a laboratory-scale fluorinating agent . The only stable chlorides are selenium tetrachloride (SeCl 4 ) and selenium monochloride (Se 2 Cl 2 ), which might be better known as selenium(I) chloride and is structurally analogous to disulfur dichloride . Metastable solutions of selenium dichloride can be prepared from sulfuryl chloride and selenium (reaction of

1357-467: Is not a selenium mineral, and contains no selenite ion , but is rather a type of gypsum (calcium sulfate hydrate) named like selenium for the moon well before the discovery of selenium. Selenium is most commonly found as an impurity, replacing a small part of the sulfur in sulfide ores of many metals. In living systems, selenium is found in the amino acids selenomethionine , selenocysteine , and methylselenocysteine . In these compounds, selenium plays

1416-465: Is represented in selenium chemistry by the selenoxides (formula RSe(O)R), which are intermediates in organic synthesis, as illustrated by the selenoxide elimination reaction. Consistent with trends indicated by the double bond rule , selenoketones, R(C=Se)R, and selenaldehydes, R(C=Se)H, are rarely observed. Selenium ( Greek σελήνη selene meaning "Moon") was discovered in 1817 by Jöns Jacob Berzelius and Johan Gottlieb Gahn . Both chemists owned

1475-556: Is the author of several books, including The Poisoner's Handbook (2010) and The Poison Squad (2018), and has been a columnist for The New York Times and a blogger, via her blog titled Elemental, for Wired . As a science writer for the Sacramento Bee , Blum wrote a series of articles examining the professional, ethical, and emotional conflicts between scientists who use animals in their research and animal rights activists who oppose that research. Titled "The Monkey Wars,"

1534-445: Is the dominant consumer of selenium at 1,500–2,000 tonnes/year. During the electrowinning of manganese, the addition of selenium dioxide decreases the power necessary to operate the electrolysis cells . China is the largest consumer of selenium dioxide for this purpose. For every tonne of manganese, an average 2 kg selenium oxide is used. The largest commercial use of selenium, accounting for about 50% of consumption,

1593-601: The Alfred P. Sloan Foundation , the Mellon Foundation , and the Kavli Foundation . The nine-month program is designed to offer selected fellows a year away from deadlines to pursue intellectual enrichment, develop new sources, and explore aspects of science and its interaction with economic, political, and cultural forces that would ordinarily be out of reach for a working science journalist. Fellows typically audit courses on

1652-829: The Kesterson National Wildlife Refuge , where poor management of irrigation runoff had polluted the wetland with toxic levels of the element selenium . Her work for the Fresno Bee put the mid-sized paper ahead of much larger regional rivals, including the San Francisco Chronicle and the Los Angeles Times in covering this major environmental story. In 1984, Blum joined the staff of the Sacramento Bee , where she broadened her range, covering science subjects. Her series "California: The Weapons Master"

1711-702: The Los Angeles Times , Discover , Psychology Today , Rolling Stone , the Utne Reader , and Mother Jones . In 2013, she began writing "Poison Pen" which appears as a column in The New York Times and as a blog post in the newspaper's online edition. website. After becoming director of the Knight Science Journalism Program, she created and became publisher of a new on-line science magazine, Undark . From 1997 until 2015, she

1770-496: The carrier lifetime . As of now, the only defect-engineering strategy that has been investigated for selenium thin-film solar cells involves crystallizing selenium using a laser . Amorphous selenium (α-Se) thin films have found application as photoconductors in flat-panel X-ray detectors . These detectors use amorphous selenium to capture and convert incident X-ray photons directly into electric charge. Selenium has been chosen for this application among other semiconductors owing to

1829-417: The 1950s, research on selenium thin-film solar cells declined. As a result, the record efficiency of 5.0% demonstrated by Tokio Nakada and Akio Kunioka in 1985 remained unchanged for more than 30 years. In 2017, researchers from IBM achieved a new record efficiency of 6.5% by redesigning the device structure. Following this achievement, selenium has gained renewed interest as a wide bandgap photoabsorber with

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1888-466: The 1970s, following which they were replaced with less expensive and even more efficient silicon rectifiers . Selenium came to medical notice later because of its toxicity to industrial workers. Selenium was also recognized as an important veterinary toxin, which is seen in animals that have eaten high-selenium plants. In 1954, the first hints of specific biological functions of selenium were discovered in microorganisms by biochemist, Jane Pinsent . It

1947-564: The Earth, Berzelius named the new element after the Moon . In 1873, Willoughby Smith found that the electrical conductivity of grey selenium was affected by light. This led to its use as a cell for sensing light. The first commercial products using selenium were developed by Werner Siemens in the mid-1870s. The selenium cell was used in the photophone developed by Alexander Graham Bell in 1879. Selenium transmits an electric current proportional to

2006-537: The II oxidation state, forms a variety of organic derivatives. They are structurally analogous to the corresponding organosulfur compounds . Especially common are selenides (R 2 Se, analogues of thioethers ), diselenides (R 2 Se 2 , analogues of disulfides ), and selenols (RSeH, analogues of thiols ). Representatives of selenides, diselenides, and selenols include respectively selenomethionine , diphenyldiselenide , and benzeneselenol . The sulfoxide in sulfur chemistry

2065-457: The Se–Se–Se angle is on average 105.7°. Other selenium allotropes may contain Se 6 or Se 7 rings. The most stable and dense form of selenium is gray and has a chiral hexagonal crystal lattice (space group 152 or 154 depending on the chirality) consisting of helical polymeric chains, where the Se–Se distance is 237.3 pm and Se–Se–Se angle is 103.1°. The minimum distance between chains

2124-509: The US with the Safe Drinking Water Act of 1974, made a reduction of lead in brass necessary. The new brass is marketed under the name EnviroBrass. Like lead and sulfur, selenium improves the machinability of steel at concentrations around 0.15%. Selenium produces the same machinability improvement in copper alloys. The lithium–selenium (Li–Se) battery was considered for energy storage in

2183-461: The United States and China. A previous sharp increase was observed in 2004 from $ 4–$ 5 to $ 27/lb. The price was relatively stable during 2004–2010 at about US$ 30 per pound (in 100 pound lots) but increased to $ 65/lb in 2011. The consumption in 2010 was divided as follows: metallurgy – 30%, glass manufacturing – 30%, agriculture – 10%, chemicals and pigments – 10%, and electronics – 10%. China

2242-409: The amount of light falling on its surface. This phenomenon was used in the design of light meters and similar devices. Selenium's semiconductor properties found numerous other applications in electronics. The development of selenium rectifiers began during the early 1930s, and these replaced copper oxide rectifiers because they were more efficient. These lasted in commercial applications until

2301-399: The atmosphere; 1 mg/kg in soil and vegetation and 0.5 μg/L in freshwater and seawater. Anthropogenic sources of selenium include coal burning, and the mining and smelting of sulfide ores. Selenium is most commonly produced from selenide in many sulfide ores , such as those of copper , nickel , or lead . Electrolytic metal refining is particularly productive of selenium as

2360-441: The changes in viscosity that sulfur undergoes when gradually heated. Selenium has seven naturally occurring isotopes . Five of these, Se, Se, Se, Se, Se, are stable, with Se being the most abundant (49.6% natural abundance). Also naturally occurring is the long-lived primordial radionuclide Se, with a half-life of 8.76×10 years. The non-primordial radioisotope Se also occurs in minute quantities in uranium ores as

2419-703: The dioxide above 185 °C: Selenium trioxide is produced in the laboratory by the reaction of anhydrous potassium selenate (K 2 SeO 4 ) and sulfur trioxide (SO 3 ). Salts of selenous acid are called selenites. These include silver selenite (Ag 2 SeO 3 ) and sodium selenite (Na 2 SeO 3 ). Hydrogen sulfide reacts with aqueous selenous acid to produce selenium disulfide : Selenium disulfide consists of 8-membered rings. It has an approximate composition of SeS 2 , with individual rings varying in composition, such as Se 4 S 4 and Se 2 S 6 . Selenium disulfide has been used in shampoo as an anti dandruff agent, an inhibitor in polymer chemistry,

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2478-402: The elements generates the tetrachloride instead), and constitute an important reagent in the preparation of selenium compounds (e.g. Se 7 ). The corresponding bromides are all known, and recapitulate the same stability and structure as the chlorides. The iodides of selenium are not well known, and for a long time were believed not to exist. There is limited spectroscopic evidence that

2537-476: The family of lithium batteries in the 2010s. Selenium was used as the photoabsorbing layer in the first solid-state solar cell, which was demonstrated by the English physicist William Grylls Adams and his student Richard Evans Day in 1876. Only a few years layer, Charles Fritts fabricated the first thin-film solar cell, also using selenium as the photoabsorber. However, with the emergence of silicon solar cells in

2596-449: The heaviest known isotopes. Selenium compounds commonly exist in the oxidation states −2, +2, +4, and +6. 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 . Selenium forms two oxides : selenium dioxide (SeO 2 ) and selenium trioxide (SeO 3 ). Selenium dioxide

2655-474: The life and career of groundbreaking psychology researcher Harry Harlow , and in Ghost Hunters she follows a quest by 19th century psychologist-philosopher William James and colleagues to apply objective scientific methods to the study of paranormal phenomena. In The Poisoner's Handbook she explores the pioneering work of two unheralded scientists who paved the way for modern forensic detectives. This book

2714-428: The lower iodides may form in bi-elemental solutions with nonpolar solvents, such as carbon disulfide and carbon tetrachloride ; but even these appear to decompose under illumination . Some selenium oxyhalides— seleninyl fluoride (SeOF 2 ) and selenium oxychloride (SeOCl 2 )—have been used as specialty solvents. Analogous to the behavior of other chalcogens, selenium forms hydrogen selenide , H 2 Se. It

2773-450: The potential of being integrated in tandem with lower bandgap photoabsorbers. In 2024, the first selenium-based tandem solar cell was demonstrated, showcasing a selenium top cell monolithically integrated with a silicon bottom cell. However, a significant deficit in the open-circuit voltage is currently the main limiting factor to further improve the efficiency, necessitating defect-engineering strategies for selenium thin-films to enhance

2832-655: The program launched an editorially independent digital science magazine called Undark . KSJ@MIT was launched in 1983 by Victor McElheny . It is administratively a part of the Program in Science, Technology, and Society (STS) located in the MIT School of Humanities, Arts and Social Sciences. The program and its activities is primarily funded by an endowment from the John S. and James L. Knight Foundation. Additional funding has been provided by

2891-555: The rate of temperature change. When prepared in chemical reactions, selenium is usually an amorphous , brick-red powder. When rapidly melted, it forms the black, vitreous form, usually sold commercially as beads. The structure of black selenium is irregular and complex and consists of polymeric rings with up to 1000 atoms per ring. Black selenium is a brittle, lustrous solid that is slightly soluble in CS 2 . Upon heating, it softens at 50 °C and converts to gray selenium at 180 °C;

2950-714: The series won the 1992 Pulitzer Prize for Beat Reporting . Born in Urbana, Illinois , Blum grew up in Baton Rouge, Louisiana , Bristol, England , and Athens, Georgia . She graduated from the University of Georgia , where she majored in journalism and was chief editor of the student newspaper, The Red and Black . She worked as a reporter covering police, fires, courts, and other general assignment beats for newspapers in Georgia, Florida and California before she turned to science writing. She

3009-462: The similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in metal sulfide ores , where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments . Selenium

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3068-413: The transformation temperature is reduced by presence of halogens and amines . The red α, β, and γ forms are produced from solutions of black selenium by varying the evaporation rate of the solvent (usually CS 2 ). They all have a relatively low, monoclinic crystal symmetry ( space group 14) and contain nearly identical puckered cyclooctaselenium (Se 8 ) rings as in sulfur . The eight atoms of

3127-431: The worldwide copper supply. This changes the availability of selenium because only a comparably small part of the selenium in the ore is leached with the copper. Industrial production of selenium usually involves the extraction of selenium dioxide from residues obtained during the purification of copper. Common production from the residue then begins by oxidation with sodium carbonate to produce selenium dioxide, which

3186-635: Was a professor in the School of Journalism and Mass Communication at the University of Wisconsin–Madison. In 2005 she was appointed Helen Firstbrook Franklin Professor of Journalism, an endowed faculty position within the University of Wisconsin journalism school. In July 2015, she became director of Knight Science Journalism at MIT. A past president of the National Association of Science Writers , she has been

3245-630: Was awarded the 1987 Livingston Award for National Reporting. In 1992 the American Association for the Advancement of Science awarded her its AAAS-Westinghouse Award for Science Journalism, also for the "Monkey Wars" series. Blum expanded the Pulitzer Prize-winning newspaper series into a book of the same title. Her second book, Sex on the Brain examines the biological differences between men and women. In Love at Goon Park , she explores

3304-424: Was discovered to be essential for mammalian life in 1957. In the 1970s, it was shown to be present in two independent sets of enzymes . This was followed by the discovery of selenocysteine in proteins. During the 1980s, selenocysteine was shown to be encoded by the codon UGA . The recoding mechanism was worked out first in bacteria and then in mammals (see SECIS element ). Native (i.e., elemental) selenium

3363-475: Was not typical of arsenic, but a similar odor was known from tellurium compounds. Hence, Berzelius's first letter to Alexander Marcet stated that this was a tellurium compound. However, the lack of tellurium compounds in the Falun Mine minerals eventually led Berzelius to reanalyze the red precipitate, and in 1818 he wrote a second letter to Marcet describing a newly found element similar to sulfur and tellurium. Because of its similarity to tellurium, named for

3422-552: Was on the staffs of the Macon Telegraph , the St. Petersburg Times and the Fresno Bee , among other publications. After earning a master's degree in environmental journalism from the University of Wisconsin–Madison , Blum returned to the Fresno Bee , where she became an award-winning environmental reporter. She was the first to report on the incidence of severely deformed waterfowl at

3481-546: Was promoted on Point of Inquiry . She received the James T. Grady-James H. Stack Award for Interpreting Chemistry for the Public from the American Chemical Society in 2015 for this book. Blum has written, most often about science and its interrelationship with American culture, for publications that have included The New York Times , The Wall Street Journal , The Boston Globe , Time , The Washington Post ,

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