Electric arc furnace
An electric arc furnace is a furnace that heats charged material by means of an electric arc. Industrial arc furnaces range in size from small units of one ton capacity up to about 400 ton units used for secondary steelmaking. Arc furnaces used in research laboratories and by dentists may have a capacity of only a few dozen grams. Industrial electric arc furnace temperatures can be up to 1,800 °C, while laboratory units can exceed 3,000 °C. Arc furnaces differ from induction furnaces in that the charge material is directly exposed to an electric arc and the current in the furnace terminals passes through the charged material. In the 19th century, a number of men had employed an electric arc to melt iron. Sir Humphry Davy conducted an experimental demonstration in 1810; the first successful and operational furnace was invented by James Burgess Readman in Edinburgh, Scotland in 1888 and patented in 1889. This was for the creation of phosphorus. Further electric arc furnaces were developed by Paul Héroult, of France, with a commercial plant established in the United States in 1907.
The Sanderson brothers formed The Sanderson Brothers steel Co. in Syracuse, New York, installing the first electric arc furnace in the U. S; this furnace is now on display at Station Square, Pennsylvania. "electric steel" was a specialty product for such uses as machine tools and spring steel. Arc furnaces were used to prepare calcium carbide for use in carbide lamps; the Stassano electric furnace is an arc type furnace that rotates to mix the bath. The Girod furnace is similar to the Héroult furnace. While EAFs were used in World War II for production of alloy steels, it was only that electric steelmaking began to expand; the low capital cost for a mini-mill—around US$140–200 per ton of annual installed capacity, compared with US$1,000 per ton of annual installed capacity for an integrated steel mill—allowed mills to be established in war-ravaged Europe, allowed them to compete with the big United States steelmakers, such as Bethlehem Steel and U. S. Steel, for low-cost, carbon steel "long products" in the U.
S. market. When Nucor—now one of the largest steel producers in the U. S.—decided to enter the long products market in 1969, they chose to start up a mini-mill, with an EAF as its steelmaking furnace, soon followed by other manufacturers. Whilst Nucor expanded in the Eastern U. S. the companies that followed them into mini-mill operations concentrated on local markets for long products, where the use of an EAF allowed the plants to vary production according to local demand. This pattern was followed globally, with EAF steel production used for long products, while integrated mills, using blast furnaces and basic oxygen furnaces, cornered the markets for "flat products"—sheet steel and heavier steel plate. In 1987, Nucor made the decision to expand into the flat products market, still using the EAF production method. An electric arc furnace used for steelmaking consists of a refractory-lined vessel water-cooled in larger sizes, covered with a retractable roof, through which one or more graphite electrodes enter the furnace.
The furnace is split into three sections: the shell, which consists of the sidewalls and lower steel "bowl". The roof supports the refractory delta in its centre, through which one or more graphite electrodes enter; the hearth may be hemispherical in shape, or in an eccentric bottom tapping furnace, the hearth has the shape of a halved egg. In modern meltshops, the furnace is raised off the ground floor, so that ladles and slag pots can be maneuvered under either end of the furnace. Separate from the furnace structure is the electrode support and electrical system, the tilting platform on which the furnace rests. Two configurations are possible: the electrode supports and the roof tilt with the furnace, or are fixed to the raised platform. A typical alternating current furnace is powered by a three-phase electrical supply and therefore has three electrodes. Electrodes are round in section, in segments with threaded couplings, so that as the electrodes wear, new segments can be added; the arc forms between the charged material and the electrode, the charge is heated both by current passing through the charge and by the radiant energy evolved by the arc.
The electric arc temperature reaches around 3000 °C, thus causing the lower sections of the electrodes to glow incandescently when in operation. The electrodes are automatically raised and lowered by a positioning system, which may use either electric winch hoists or hydraulic cylinders; the regulating system maintains constant current and power input during the melting of the charge though scrap may move under the electrodes as it melts. The mast arms holding the electrodes can either carry heavy busbars or be "hot arms", where the whole arm carries the current, increasing efficiency. Hot arms can be made from copper-clad steel or aluminium. Large water-cooled cables connect the bus tubes or arms with the transformer located adjacent to the furnace; the transformer is installed in a vault and is wa
Chemins de fer de l'Est
The Compagnie des chemins de fer de l'Est referred to as the Est company, was an early French railway company. The company was formed in 1853 by fusion from Compagnie du chemin de fer de Paris à Strasbourg, operating the Paris-Strasbourg line, Compagnie du chemin de fer de Montereau à Troyes. In 1938 it became part of the majority state-owned Société Nationale des Chemins de fer Français. In 1854 the company absorbed the Compagnie du chemin de fer de Strasbourg à Bale, in 1858 the Compagnie du chemin de fer de Mulhouse à Thann and in 1863 the railway network of the compagnie du chemin de fer des Ardennes. Demeur, R.. "Compagnie des chemins de fer de l'Est". Les chemins de fer français en 1860: Statuts des compagnies, notices historiques-situations financières. Pp. 92–115. Ministère des travaux publics, Recueil des lois et conventions relatives aux chemins de fer du Nord, de l'Est, d'Orléans, de Paris-Lyon-Méditerranée et du Midi: 1883 à 1910, Imprimerie Nationale. 1911. Rigouard, Jean-Pierre. Paris-Strasbourg, de la Compagnie de l'est au TGV, Mémoire en images.
Alan Sutton. ISBN 2849105503. Ellenberger, Marc. La Compagnie des chemins de fer de l'Est et la guerre de 1914-1918. Bures-sur-Yvette: Ellenberger. Forthoffer, Joël. "Le transport ferroviaire de denrées périssables en Alsace: l'exemple de la bière". Revue de l'histoire des chemins de fer de l'AHICF: 179–186. ISSN 0996-9403; the author reports on the transport of perishable goods by rail in Alsace in the 20th century. It traces the evolution of the market of la Compagnie des chemins de fer de l'Est in 1852 to la Reichsbahn Elsass Lothringen
Iridium is a chemical element with symbol Ir and atomic number 77. A hard, silvery-white transition metal of the platinum group, iridium is the second-densest metal with a density of 22.56 g/cm3 as defined by experimental X-ray crystallography. At room temperature and standard atmospheric pressure, iridium has a density of 22.65 g/cm3, 0.04 g/cm3 higher than osmium measured the same way. It is the most corrosion-resistant metal at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable. Iridium was discovered in 1803 among insoluble impurities in natural platinum. Smithson Tennant, the primary discoverer, named iridium for the Greek goddess Iris, personification of the rainbow, because of the striking and diverse colors of its salts. Iridium is one of the rarest elements in Earth's crust, with annual production and consumption of only three tonnes. 191Ir and 193Ir are the only two occurring isotopes of iridium, as well as the only stable isotopes.
The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium forms a number of organometallic compounds used in industrial catalysis, in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, as in high-performance spark plugs, crucibles for recrystallization of semiconductors at high temperatures, electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators. Iridium is found in meteorites in much higher abundance than in the Earth's crust. For this reason, the unusually high abundance of iridium in the clay layer at the Cretaceous–Paleogene boundary gave rise to the Alvarez hypothesis that the impact of a massive extraterrestrial object caused the extinction of dinosaurs and many other species 66 million years ago. An iridium anomaly in core samples from the Pacific Ocean suggested the Eltanin impact of about 2.5 million years ago.
It is thought that the total amount of iridium in the planet Earth is much higher than that observed in crustal rocks, but as with other platinum-group metals, the high density and tendency of iridium to bond with iron caused most iridium to descend below the crust when the planet was young and still molten. A member of the platinum group metals, iridium is white, resembling platinum, but with a slight yellowish cast; because of its hardness and high melting point, solid iridium is difficult to machine, form, or work. It is the only metal to maintain good mechanical properties in air at temperatures above 1,600 °C, it has the 10th highest boiling point among all elements and becomes a superconductor at temperatures below 0.14 K. Iridium's modulus of elasticity is the second-highest among the metals, only being surpassed by osmium. This, together with a high shear modulus and a low figure for Poisson's ratio, indicate the high degree of stiffness and resistance to deformation that have rendered its fabrication into useful components a matter of great difficulty.
Despite these limitations and iridium's high cost, a number of applications have developed where mechanical strength is an essential factor in some of the severe conditions encountered in modern technology. The measured density of iridium is only lower than that of osmium, the densest metal known; some ambiguity occurred regarding which of the two elements was denser, due to the small size of the difference in density and difficulties in measuring it but, with increased accuracy in factors used for calculating density X-ray crystallographic data yielded densities of 22.56 g/cm3 for iridium and 22.59 g/cm3 for osmium. Iridium is the most corrosion-resistant metal known: it is not attacked by any acid, aqua regia, molten metals, or silicates at high temperatures, it can, however, be attacked by some molten salts, such as sodium cyanide and potassium cyanide, as well as oxygen and the halogens at higher temperatures. Iridium reacts directly with sulfur at atmospheric pressure to yield iridium disulfide.
Iridium forms compounds in oxidation states between −3 and +9. Well-characterized examples of the high +6 oxidation state are rare, but include IrF6 and two mixed oxides Sr2MgIrO6 and Sr2CaIrO6. In addition, it was reported in 2009 that iridium oxide was prepared under matrix isolation conditions by UV irradiation of an iridium-peroxo complex; this species, however, is not expected to be stable as a bulk solid at higher temperatures. The highest oxidation state, the highest recorded for any element, is only known in one cation, IrO+4. Iridium dioxide, IrO2, a blue black solid, is the only well-characterized oxide of iridium. A sesquioxide, Ir2O3, has been described as a blue-black powder, oxidized to IrO2 by HNO3; the corresponding disulfides, diselenides and sesquiselenides are known, IrS3 has been reported. Iridium forms iridates with oxidation states +4 and +5, such as K2IrO3 and KIrO3, which can be prepared from the reaction of potassium oxide or potassium superoxide with iridium at high temperatures.
Although no binary hydrides of iridium, IrxHy are known, complexes are known that contain IrH4−5 and IrH3−6, where iridium has the +1 and +3 oxidation states, respectively. The ternary hydride Mg6Ir2H11 is believed to contain both the IrH4−5 and
Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a toxic pale yellow diatomic gas at standard conditions; as the most electronegative element, it is reactive, as it reacts with all other elements, except for helium and neon. Among the elements, fluorine ranks 24th in universal 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, a process still employed for modern production. Industrial production of fluorine gas for uranium enrichment, its largest application, began during the Manhattan Project in World War II. Owing to the expense of refining pure fluorine, most commercial applications use fluorine compounds, with about half of mined fluorite used in steelmaking.
The rest of the fluorite is converted into corrosive hydrogen fluoride en route to various organic fluorides, or into cryolite, which plays a key role in aluminium refining. Molecules containing a Carbon–fluorine bond have high chemical and thermal stability. Pharmaceuticals such as atorvastatin and fluoxetine contain C-F bonds, the fluoride ion inhibits dental cavities, so finds use in toothpaste and water fluoridation. Global fluorochemical sales amount to more than US$15 billion a year. Fluorocarbon gases are greenhouse gases with global-warming potentials 100 to 20,000 times that of carbon dioxide. Organofluorine compounds persist in the environment due to the strength of the carbon–fluorine bond. Fluorine has no known metabolic role in mammals. Fluorine atoms have nine electrons, one fewer than neon, electron configuration 1s22s22p5: two electrons in a filled inner shell and seven in an outer shell requiring one more to be filled; the outer electrons are ineffective at nuclear shielding, experience a high effective nuclear charge of 9 − 2 = 7.
Fluorine's first ionization energy is third-highest among all elements, behind helium and neon, which complicates the removal of electrons from neutral fluorine atoms. It has a high electron affinity, second only to chlorine, tends to capture an electron to become isoelectronic with the noble gas neon. Fluorine atoms have a small covalent radius of around 60 picometers, similar to those of its period neighbors oxygen and neon; the bond energy of difluorine is much lower than that of either Cl2 or Br2 and similar to the cleaved peroxide bond. Conversely, bonds to other atoms are strong because of fluorine's high electronegativity. Unreactive substances like powdered steel, glass fragments, asbestos fibers react with cold fluorine gas. Reactions of elemental fluorine with metals require varying conditions. Alkali metals cause; some solid nonmetals react vigorously in liquid air temperature fluorine. Hydrogen sulfide and sulfur dioxide combine with fluorine, the latter sometimes explosively. Hydrogen, like some of the alkali metals, reacts explosively with fluorine.
Carbon, as lamp black, reacts at room temperature to yield fluoromethane. Graphite combines with fluorine above 400 °C to produce non-stoichiometric carbon monofluoride. Carbon dioxide and carbon monoxide react at or just above room temperature, whereas paraffins and other organic chemicals generate strong reactions: fully substituted haloalkanes such as carbon tetrachloride incombustible, may explode. Although nitrogen trifluoride is stable, nitrogen requires an electric discharge at elevated temperatures for reaction with fluorine to occur, due to the strong triple bond in elemental nitrogen. Oxygen does not combine with fluorine under ambient conditions, but can be made to react using electric discharge at low temperatures and pressures. Heavier halogens react with fluorine as does the noble gas radon. At room temperature, fluorine is a gas of diatomic molecules, pale yellow, it has a characteristic halogen-like biting odor detectable at 20 ppb. Fluorine condenses into a bright yellow liquid at −188 °C, a transition temperature similar to those of oxygen and nitrogen.
Fluorine has two solid forms, α- and β-fluorine. The latter crystallizes at −220 °C and is transparent and sof
Chemistry is the scientific discipline involved with elements and compounds composed of atoms and ions: their composition, properties and the changes they undergo during a reaction with other substances. In the scope of its subject, chemistry occupies an intermediate position between physics and biology, it is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry, the formation of igneous rocks, how atmospheric ozone is formed and how environmental pollutants are degraded, the properties of the soil on the moon, how medications work, how to collect DNA evidence at a crime scene. Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron; the word chemistry comes from alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, philosophy, astronomy and medicine.
It is seen as linked to the quest to turn lead or another common starting material into gold, though in ancient times the study encompassed many of the questions of modern chemistry being defined as the study of the composition of waters, growth, disembodying, drawing the spirits from bodies and bonding the spirits within bodies by the early 4th century Greek-Egyptian alchemist Zosimos. An alchemist was called a'chemist' in popular speech, the suffix "-ry" was added to this to describe the art of the chemist as "chemistry"; the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία; this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, in turn derived from the word Kemet, the ancient name of Egypt in the Egyptian language. Alternately, al-kīmīā may derive from χημεία, meaning "cast together"; the current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, molecules, metals and other aggregates of matter.
This matter can be studied in isolation or in combination. The interactions and transformations that are studied in chemistry are the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together; such behaviors are studied in a chemistry laboratory. The chemistry laboratory stereotypically uses various forms of laboratory glassware; however glassware is not central to chemistry, a great deal of experimental chemistry is done without it. A chemical reaction is a transformation of some substances into one or more different substances; the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which involves atoms as subjects; the number of atoms on the left and the right in the equation for a chemical transformation is equal. The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions, they can be analyzed using the tools of e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; the particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a mixture of substances; the atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud; the nucleus is made up of positively charged protons and uncharged neutrons, while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons.
The nucleus is dense. The atom is the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state, coordination number, preferred types of bonds to form. A chemical element is a pure substance, composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z; the mass number is the sum of the number of neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same
Elliott Cresson Medal
The Elliott Cresson Medal known as the Elliott Cresson Gold Medal, was the highest award given by the Franklin Institute. The award was established by Elliott Cresson, life member of the Franklin Institute, with $1,000 granted in 1848; the endowed award was to be "for some discovery in the Arts and Sciences, or for the invention or improvement of some useful machine, or for some new process or combination of materials in manufactures, or for ingenuity skill or perfection in workmanship." The medal was first awarded 21 years after Cresson's death. The Franklin Institute continued awarding the medal on an occasional basis until 1998 when they reorganized their endowed awards under one umbrella, The Benjamin Franklin Awards. A total of 268 Elliott Cresson Medals were given out during the award's lifetime
Paris is the capital and most populous city of France, with an area of 105 square kilometres and an official estimated population of 2,140,526 residents as of 1 January 2019. Since the 17th century, Paris has been one of Europe's major centres of finance, commerce, fashion and the arts; the City of Paris is the centre and seat of government of the Île-de-France, or Paris Region, which has an estimated official 2019 population of 12,213,364, or about 18 percent of the population of France. The Paris Region had a GDP of €681 billion in 2016, accounting for 31 percent of the GDP of France, was the 5th largest region by GDP in the world. According to the Economist Intelligence Unit Worldwide Cost of Living Survey in 2018, Paris was the second most expensive city in the world, after Singapore, ahead of Zurich, Hong Kong and Geneva. Another source ranked Paris as most expensive, on a par with Singapore and Hong-Kong, in 2018; the city is a major rail and air-transport hub served by two international airports: Paris-Charles de Gaulle and Paris-Orly.
Opened in 1900, the city's subway system, the Paris Métro, serves 5.23 million passengers daily, is the second busiest metro system in Europe after Moscow Metro. Gare du Nord is the 24th busiest railway station in the world, the first located outside Japan, with 262 million passengers in 2015. Paris is known for its museums and architectural landmarks: the Louvre was the most visited art museum in the world in 2018, with 10.2 million visitors. The Musée d'Orsay and Musée de l'Orangerie are noted for their collections of French Impressionist art, the Pompidou Centre Musée National d'Art Moderne has the largest collection of modern and contemporary art in Europe; the historical district along the Seine in the city centre is classified as a UNESCO Heritage Site. Popular landmarks in the centre of the city include the Cathedral of Notre Dame de Paris and the Gothic royal chapel of Sainte-Chapelle, both on the Île de la Cité. Paris received 23 million visitors in 2017, measured by hotel stays, with the largest numbers of foreign visitors coming from the United States, the UK, Germany and China.
It was ranked as the third most visited travel destination in the world in 2017, after Bangkok and London. The football club Paris Saint-Germain and the rugby union club Stade Français are based in Paris; the 80,000-seat Stade de France, built for the 1998 FIFA World Cup, is located just north of Paris in the neighbouring commune of Saint-Denis. Paris hosts the annual French Open Grand Slam tennis tournament on the red clay of Roland Garros. Paris will host the 2024 Summer Olympics; the 1938 and 1998 FIFA World Cups, the 2007 Rugby World Cup, the 1960, 1984, 2016 UEFA European Championships were held in the city and, every July, the Tour de France bicycle race finishes there. The name "Paris" is derived from the Celtic Parisii tribe; the city's name is not related to the Paris of Greek mythology. Paris is referred to as the City of Light, both because of its leading role during the Age of Enlightenment and more because Paris was one of the first large European cities to use gas street lighting on a grand scale on its boulevards and monuments.
Gas lights were installed on the Place du Carousel, Rue de Rivoli and Place Vendome in 1829. By 1857, the Grand boulevards were lit. By the 1860s, the boulevards and streets of Paris were illuminated by 56,000 gas lamps. Since the late 19th century, Paris has been known as Panam in French slang. Inhabitants are known in French as Parisiens, they are pejoratively called Parigots. The Parisii, a sub-tribe of the Celtic Senones, inhabited the Paris area from around the middle of the 3rd century BC. One of the area's major north–south trade routes crossed the Seine on the île de la Cité; the Parisii minted their own coins for that purpose. The Romans began their settlement on Paris' Left Bank; the Roman town was called Lutetia. It became a prosperous city with a forum, temples, an amphitheatre. By the end of the Western Roman Empire, the town was known as Parisius, a Latin name that would become Paris in French. Christianity was introduced in the middle of the 3rd century AD by Saint Denis, the first Bishop of Paris: according to legend, when he refused to renounce his faith before the Roman occupiers, he was beheaded on the hill which became known as Mons Martyrum "Montmartre", from where he walked headless to the north of the city.
Clovis the Frank, the first king of the Merovingian dynasty, made the city his capital from 508. As the Frankish domination of Gaul began, there was a gradual immigration by the Franks to Paris and the Parisian Francien dialects were born. Fortification of the Île-de-la-Citie failed to avert sacking by Vikings in 845, but Paris' strategic importance—with its bridges prevent