An explosion is a rapid increase in volume and release of energy in an extreme manner with the generation of high temperatures and the release of gases. Supersonic explosions created by high explosives are known as detonations and travel via supersonic shock waves. Subsonic explosions are created by low explosives through a slower burning process known as deflagration. Explosions can occur in nature due to a large influx of energy. Most natural explosions arise from volcanic processes of various sorts. Explosive volcanic eruptions occur. Explosions occur as a result of impact events and in phenomena such as hydrothermal explosions. Explosions can occur outside of Earth in the universe in events such as supernova. Explosions occur during bushfires in eucalyptus forests where the volatile oils in the tree tops combust. Among the largest known explosions in the universe are supernovae, which results when a star explodes from the sudden starting or stopping of nuclear fusion gamma-ray bursts, whose nature is still in some dispute.
Solar flares are an example of a common explosion on the Sun, on most other stars as well. The energy source for solar flare activity comes from the tangling of magnetic field lines resulting from the rotation of the Sun's conductive plasma. Another type of large astronomical explosion occurs when a large meteoroid or an asteroid impacts the surface of another object, such as a planet; the most common artificial explosives are chemical explosives involving a rapid and violent oxidation reaction that produces large amounts of hot gas. Gunpowder was the first explosive to put to use. Other notable early developments in chemical explosive technology were Frederick Augustus Abel's development of nitrocellulose in 1865 and Alfred Nobel's invention of dynamite in 1866. Chemical explosions are initiated by an electric spark or flame in the presence of Oxygen. Accidental explosions may occur in rocket engines, etc.. A high current electrical fault can create an'electrical explosion' by forming a high energy electrical arc which vaporizes metal and insulation material.
This arc flash hazard is a danger to persons working on energized switchgear. Excessive magnetic pressure within an ultra-strong electromagnet can cause a magnetic explosion. A physical process, as opposed to chemical or nuclear, e.g. the bursting of a sealed or sealed container under internal pressure is referred to as an explosion. Examples include a simple tin can of beans tossed into a fire. Boiling liquid expanding vapor explosions are one type of mechanical explosion that can occur when a vessel containing a pressurized liquid is ruptured, causing a rapid increase in volume as the liquid evaporates. Note that the contents of the container may cause a subsequent chemical explosion, the effects of which can be more serious, such as a propane tank in the midst of a fire. In such a case, to the effects of the mechanical explosion when the tank fails are added the effects from the explosion resulting from the released propane in the presence of an ignition source. For this reason, emergency workers differentiate between the two events.
In addition to stellar nuclear explosions, a man-made nuclear weapon is a type of explosive weapon that derives its destructive force from nuclear fission or from a combination of fission and fusion. As a result a nuclear weapon with a small yield is more powerful than the largest conventional explosives available, with a single weapon capable of destroying an entire city. Explosive force is released in a direction perpendicular to the surface of the explosive. If a grenade is in mid air during the explosion, the direction of the blast will be 360°. In contrast, in a shaped charge the explosive forces are focused to produce a greater local effect; the speed of the reaction is what distinguishes an explosive reaction from an ordinary combustion reaction. Unless the reaction occurs rapidly, the thermally expanding gases will be moderately dissipated in the medium, with no large differential in pressure and there will be no explosion. Consider a wood fire; as the fire burns, there is the evolution of heat and the formation of gases, but neither is liberated enough to build up a sudden substantial pressure differential and cause an explosion.
This can be likened to the difference between the energy discharge of a battery, slow, that of a flash capacitor like that in a camera flash, which releases its energy all at once. The generation of heat in large quantities accompanies most explosive chemical reactions; the exceptions are called entropic explosives and include organic peroxides such as acetone peroxide. It is the rapid liberation of heat that causes the gaseous products of most explosive reactions to expand and generate high pressures; this rapid generation of high pressures of the released gas constitutes the explosion. The liberation of heat with insufficient rapidity will not cause an explosion. For example, although a unit mass of coal yields five times as much heat as a unit mass of nitroglycerin, the coal cannot be used as an explosive because the rate at which it yields this heat is quite slow. In fact, a substance which burns less may evolve more total heat than an explosive which detonates rapidly. In the form
State Council of the People's Republic of China
The State Council, constitutionally synonymous with the Central People's Government since 1954, is the chief administrative authority of the People's Republic of China. It is chaired by the premier and includes the heads of each of the cabinet-level executive departments; the council has 35 members: the premier, one executive vice premier, three other vice premiers, five state councilors, 25 additional ministers and chairs of major agencies. In the politics of the People's Republic of China, the Central People's Government forms one of three interlocking branches of power, the others being the Communist Party of China and the People's Liberation Army; the State Council directly oversees the various subordinate People's Governments in the provinces, in practice maintains membership with the top levels of the Communist Party of China. The State Council meets every six months. Between meetings it is guided by a Standing Committee; the standing committee includes the premier, one executive vice premier, three vice premiers, five other state councilors.
The vice-premiers and state councilors are nominated by the premier, appointed by the president with National People's Congress' approval. Incumbents may serve two successive five-year terms; each vice premier oversees certain areas of administration. Each State Councilor performs duties as designated by the Premier; the secretary-general heads the General Office which handles the day-to-day work of the State Council. The secretary-general has little power and should not be confused with the General Secretary of the Communist Party of China; each ministry supervises one sector. Commissions outrank ministries and set policies for and coordinate the related activities of different administrative organs. Offices deal with matters of ongoing concern. Bureaus and administrations rank below ministries. In addition to the 25 ministries, there are 38 centrally administered government organizations that report directly to the state council; the heads of these organizations attend full meetings of the state committee on an irregular basis.
The State Council is formally responsible to the NPC and its Standing Committee in conducting a wide range of government functions both at the national and at the local levels, nominally acts by virtue of the NPC's authority. There has been at least one case where the NPC has outright rejected an initiative of the State Council and a few cases where the State Council has withdrawn or modified a proposal in response to NPC opposition; the State Council and the Communist Party of China are tightly interlocked. With rare exceptions, State Councilors are high-ranking members of the CPC. Although, as Party members, they are supposed to follow Party instructions, because they tend to be senior members of the Party they have substantial influence over what those instructions are; this results in a system, unlike the Soviet practice in which the Party controlled the State. Rather, the Party and State are fused at this level of government; the members of the State Council derive their authority from being members of the state, while as members of the Party they coordinate their activities and determine key decisions such as the naming of personnel.
There were attempts to separate the party and state in the late 1980s under Zhao Ziyang and have the Party in charge of formulating policy and the State Council executing policy, but these efforts were abandoned in the early 1990s. As the chief administrative organ of government, its main functions are to formulate administrative measures, issue decisions and orders, monitor their implementation; the State Council is the functional center of state power and clearinghouse for government initiatives at all levels. With the government's emphasis on economic modernization, the State Council acquired additional importance and influence; the State Council controls the Ministry for National Defense but does not control the People's Liberation Army, instead controlled by the Central Military Commission. Secretary-General of the State Council Deputy Secretary-Generals of the State Council State-owned Assets Supervision and Administration Commission, established in 2003 General Administration of Customs of the People's Republic of China State Administration of Taxation State Administration for Market Regulation National Radio and Television Administration General Administration of Sport National Bureau of Statistics China International Development Cooperation Agency National Healthcare Security Administration Counselor's Office of the State Council National Government Offices Administration the "Government Offices Administration of the State Council" National Press and Publication Administration, additional name "National Copyright Administration", a name reserved by the Publicity Department of the Communist Party of China National Religious Affairs Administration, a name reserved by the United Front Work Department of the Communist Party of China Hong Kong and Macau Affairs Office of the State Council State Council Research Office Overseas Chinese Affairs Office of the State Council, a name reserved by the United Front Work Department of the Communist Party of China Taiwan Affai
A chemical substance is a form of matter having constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. Chemical substances can be chemical compounds, or alloys. Chemical elements may not be included in the definition, depending on expert viewpoint. Chemical substances are called'pure' to set them apart from mixtures. A common example of a chemical substance is pure water. Other chemical substances encountered in pure form are diamond, table salt and refined sugar. However, in practice, no substance is pure, chemical purity is specified according to the intended use of the chemical. Chemical substances exist as solids, gases, or plasma, may change between these phases of matter with changes in temperature or pressure. Chemical substances may be converted to others by means of chemical reactions. Forms of energy, such as light and heat, are not matter, are thus not "substances" in this regard.
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook. According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; the chemical substance index published by CAS includes several alloys of uncertain composition. Non-stoichiometric compounds are a special case that violates the law of constant composition, for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature". In geology, substances of uniform composition are called minerals, while physical mixtures of several minerals are defined as rocks.
Many minerals, mutually dissolve into solid solutions, such that a single rock is a uniform substance despite being a mixture in stoichiometric terms. Feldspars are a common example: anorthoclase is an alkali aluminum silicate, where the alkali metal is interchangeably either sodium or potassium. In law, "chemical substances" may include both pure substances and mixtures with a defined composition or manufacturing process. For example, the EU regulation REACH defines "monoconstituent substances", "multiconstituent substances" and "substances of unknown or variable composition"; the latter two consist of multiple chemical substances. For example, charcoal is an complex polymeric mixture that can be defined by its manufacturing process. Therefore, although the exact chemical identity is unknown, identification can be made to a sufficient accuracy; the CAS index includes mixtures. Polymers always appear as mixtures of molecules of multiple molar masses, each of which could be considered a separate chemical substance.
However, the polymer may be defined by a known precursor or reaction and the molar mass distribution. For example, polyethylene is a mixture of long chains of -CH2- repeating units, is sold in several molar mass distributions, LDPE, MDPE, HDPE and UHMWPE; the concept of a "chemical substance" became established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate. He deduced; this is now known as the law of constant composition. With the advancement of methods for chemical synthesis in the realm of organic chemistry. However, there are some controversies regarding this definition because the large number of chemical substances reported in chemistry literature need to be indexed. Isomerism caused much consternation to early researchers, since isomers have the same composition, but differ in configuration of the atoms. For example, there was much speculation for the chemical identity of benzene, until the correct structure was described by Friedrich August Kekulé.
The idea of stereoisomerism – that atoms have rigid three-dimensional structure and can thus form isomers that differ only in their three-dimensional arrangement – was another crucial step in understanding the concept of distinct chemical substances. For example, tartaric acid has three distinct isomers, a pair of diastereomers with one diastereomer forming two enantiomers. An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmuted into another element through a nuclear reaction; this is so, beca
The Amur River or Heilong Jiang is the world's tenth longest river, forming the border between the Russian Far East and Northeastern China. The largest fish species in the Amur is the kaluga; the river basin is home to a variety of large predatory fish such as northern snakehead, Amur pike, Amur catfish, predatory carp and yellowcheek, as well as the northernmost populations of the Amur softshell turtle and Indian lotus. It was common to refer to a river as "water"; the word for "water" is similar in a number of Asiatic languages: mul in Korean, muren in Mongolian, mizu in Japanese. The name "Amur" may have evolved from a root word for water, coupled with a size modifier for "Big Water"; the Chinese name for the river, Heilong Jiang, means Black Dragon River in Chinese, its Mongolian name, Khar mörön, means Black River. The river rises in the hills in the western part of Northeast China at the confluence of its two major affluents, the Shilka River and the Ergune River, at an elevation of 303 metres.
It flows east forming the border between China and Russia, makes a great arc to the southeast for about 400 kilometres, receiving many tributaries and passing many small towns. At Huma, it is joined by the Huma River. Afterwards it continues to flow south until between the cities of Blagoveschensk and Heihe, it widens as it is joined by the Zeya River, one of its most important tributaries; the Amur arcs to the east and turns southeast again at the confluence with the Bureya River does not receive another significant tributary for nearly 250 kilometres before its confluence with its largest tributary, the Songhua River, at Tongjiang. At the confluence with the Songhua the river turns northeast, now flowing towards Khabarovsk, where it joins the Ussuri River and ceases to define the Russia–China border. Now the river spreads out into a braided character, flowing north-northeast through a wide valley in eastern Russia, passing Amursk and Komsomolsk-on-Amur; the valley narrows after about 200 kilometres and the river again flows north onto plains at the confluence with the Amgun River.
Shortly after, the Amur turns east and into an estuary at Nikolayevsk-on-Amur, about 20 kilometres downstream of which it flows into the Strait of Tartary. In many historical references these two geopolitical entities are known as Outer Manchuria and Inner Manchuria, respectively; the Chinese province of Heilongjiang on the south bank of the river is named after it, as is the Russian Amur Oblast on the north bank. The name Black River was used by the native Manchu people and their Qing Empire of China, who regarded this river as sacred; the Amur River is an important symbol of, geopolitical factor in, Chinese–Russian relations. The Amur was important in the period following the Sino–Soviet political split in the 1960s. For many centuries the Amur Valley was populated by the Tungusic, Mongol people, some Ainu and, near its mouth, by the Nivkhs. For many of them, fishing in the Amur and its tributaries was the main source of their livelihood; until the 17th century, these people were not known to the Europeans, little known to the Han Chinese, who sometimes collectively described them as the Wild Jurchens.
The term Yupi Dazi was used for the Nanais and related groups as well, owing to their traditional clothes made of fish skins. The Mongols, ruling the region as the Yuan dynasty, established a tenuous military presence on the lower Amur in the 13–14th centuries. During the Yongle and Xuande eras, the Ming dynasty reached the Amur as well in their drive to establish control over the lands adjacent to the Ming Empire to the northeast, which were to become known as Manchuria. Expeditions headed by the eunuch Yishiha reached Tyr several times between 1411 and the early 1430s, re-building the Yongning Temple and obtaining at least the nominal allegiance of the lower Amur's tribes to the Ming government; some sources report a Chinese presence during the same period on the middle Amur – a fort existed at Aigun for about 20 years during the Yongle era on the left shore of the Amur downstream from the mouth of the Zeya River. This Ming Dynasty Aigun was located on the opposite bank to the Aigun, relocated during the Qing Dynasty.
In any event, the Ming presence on the Amur was as short-lived. Chinese cultural and religious influence such as Chinese New Year, the "Chinese god", Chinese motifs like the dragon, spirals and material goods like agriculture, heating, iron cooking pots and cotton spread among the Amur natives like the Udeghes and Nanais. Russian Cossack expeditions led by Vassili Poyarkov and Yerofey Khabarov explored the Amur and its tributaries in 1643–44 and 1649–51, respectively; the Cossacks established the fort of Albazin on the upper Amur, at the site of the former capital of the Solons. At the time, the Manchus were busy with conquering the region.
Sea of Okhotsk
The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaido to the south, the island of Sakhalin along the west, a long stretch of eastern Siberian coast along the west and north. The northeast corner is the Shelikhov Gulf; the sea is named after the first Russian settlement in the Far East. The Sea of Okhotsk covers an area of 1,583,000 square kilometres, with a mean depth of 859 metres and a maximum depth of 3,372 metres, it is connected to the Sea of Japan on either side of Sakhalin: on the west through the Sakhalin Gulf and the Gulf of Tartary. In winter, navigation on much of the Sea of Okhotsk becomes difficult or impossible due to the formation of large ice floes; this is due to the large amount of freshwater from the Amur River, lowering the salinity of upper levels raising the freezing point of the sea surface. The distribution and thickness of ice floes depends on many factors: the location, the time of year, water currents, the sea temperatures.
With the exception of Hokkaido, one of the Japanese home islands, the sea is surrounded on all sides by territory administered by the Russian Federation. The International Hydrographic Organization defines the limits of the Sea of Okhotsk as follows: On the Southwest; the Northeastern and Northern limits on the Japan Sea. On the Southeast. A line running from Nosyappu Saki in the Island of Hokusyû through the Kuril or Tisima Islands to Cape Lopatka in such a way that all the narrow waters between Hokusyû and Kamchatka are included in the Sea of Okhotsk; some of the Sea of Okhotsk's islands are quite large, including Japan's second largest island, Hokkaido, as well as Russia's largest island, Sakhalin. All of the sea's islands are either in coastal waters or belong to the various islands making up the Kuril Islands chain; these fall either under undisputed Japanese or Russian ownership or disputed ownership between Japan and Russia. Iony Island is the only island located in open waters and belongs to the Khabarovsk Krai of the Russian Federation.
The majority of the sea's islands are uninhabited making them ideal breeding grounds for seals, sea lions and other sea island fauna. Large colonies, with over a million individuals, of crested auklets use the Sea of Okhotsk as a nesting site; the Okhotsk culture is an archaeological coastal fishing and hunter-gatherer culture of the lands surrounding the Sea of Okhotsk. Some believe. Russian explorers Ivan Moskvitin and Vassili Poyarkov were the first Europeans to visit the Sea of Okhotsk in the 1640s; the Dutch captain Maarten Gerritsz Vries in the Breskens entered the Sea of Okhotsk from the south-east in 1643, charted parts of the Sakhalin coast and Kurile Islands, but failed to realize that either Sakhalin or Hokkaido are islands. The first and foremost Russian settlement on the shore was the port of Okhotsk, which relinquished commercial supremacy to Ayan in the 1840s; the Russian-American Company all but monopolized the commercial navigation of the sea in the first half of the 19th century.
The Second Kamchatka Expedition under Vitus Bering systematically mapped the entire coast of the sea, starting in 1733. Jean-François de La Pérouse and William Robert Broughton were the first non-Russian European navigators known to have passed through these waters other than Maarten Gerritsz Vries. Ivan Krusenstern explored the eastern coast of Sakhalin in 1805. Mamiya Rinzō and Gennady Nevelskoy determined that the Sakhalin was indeed an island separated from the mainland by a narrow strait; the first detailed summary of the hydrology of the Okhotsk sea was prepared and published by Stepan Makarov in 1894. The Sea of Okhotsk is one of the world's richest in biological resources, with various kinds of fish and crabs; the harsh conditions of crab fishing in the Sea of Okhotsk is the subject of the most famous novel of the Japanese writer Takiji Kobayashi,'The Crab Cannery Ship'. American and European whaleships hunted whales in the sea in the nineteenth and early twentieth centuries, they caught right and bowhead whales.
A number of ships were wrecked in the sea. During the Cold War, the Sea of Okhotsk was the scene of several successful U. S. Navy operations to tap Soviet Navy undersea communications cables; these operations were documented in the book Blind Man's Bluff: The Untold Story of American Submarine Espionage. The sea were the scene of the Soviet attack on Korean Air Flight 007 in 1983; the Soviet Pacific Fleet used the Sea as a ballistic missile submarine bastion, a strategy that Russia continues. In the Japanese language, the sea has no traditional Japanese name despite its close location to the Japanese territories and is called Ohōtsuku-kai, a transcription of the Russian name. Additionally, Okhotsk Subprefecture, Hokkaidō which faces the sea known as Okhotsk region, is named after the sea. 29 zones of possible oil and gas accumulation have been identified on the Sea of Okhotsk shelf, which runs along the coast. Total reserves are estimated at 3.5 billion tons of equivalent fuel, including 1.2 billion tons of oil and 1.5 billion cubic meters of gas.
On 18 Decembe
Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor, it freezes to give greenish-yellow crystals. It is produced on a large scale from benzene as a precursor to aniline. In the laboratory, it is used as a solvent for electrophilic reagents. Nitrobenzene is prepared by nitration of benzene with a mixture of concentrated sulfuric acid and nitric acid; this mixture is sometimes called "mixed acid." The production of nitrobenzene is one of the most dangerous processes conducted in the chemical industry because of the exothermicity of the reaction. World capacity for nitrobenzene in 1985 was about 1.7×106 tonnes. The nitration process involves formation of the nitronium ion, followed by an electrophilic aromatic substitution reaction of it with benzene; the nitronium ion is generated by the reaction of nitric acid and an acidic dehydration agent sulfuric acid: HNO3 + H+ ⇌ NO2+ + H2O Approximately 95% of nitrobenzene is consumed in the production of aniline: C6H5NO2 + 3 H2 → C6H5NH2 + 2 H2OAniline is a precursor to urethane polymers, rubber chemicals, dyes and pharmaceuticals.
Nitrobenzene is used to mask unpleasant odors in shoe and floor polishes, leather dressings, paint solvents, other materials. Redistilled, as oil of mirbane, nitrobenzene had been used as an inexpensive perfume for soaps, it has been replaced by less toxic chemicals for this purpose. A significant merchant market for nitrobenzene is its use in the production of the analgesic paracetamol. Nitrobenzene is used in Kerr cells, as it has an unusually large Kerr constant. Evidence suggests its use in agriculture as a plant growth/flowering stimulant. Aside from its conversion to aniline, nitrobenzene can be selectively reduced to azoxybenzene, nitrosobenzene and phenylhydroxylamine. Nitrobenzene is toxic and absorbed through the skin. Prolonged exposure may cause serious damage to the central nervous system, impair vision, cause liver or kidney damage and lung irritation. Inhalation of vapors may induce headache, fatigue, cyanosis, weakness in the arms and legs, in rare cases may be fatal; the oil is absorbed through the skin and may increase heart rate, cause convulsions or death.
Ingestion may cause headaches, nausea and gastrointestinal irritation, loss of sensation/use in limbs and causes internal bleeding. Nitrobenzene is considered a human carcinogen by the United States Environmental Protection Agency, is classified by the IARC as a Group 2B carcinogen, "possibly carcinogenic to humans", it has been shown to cause liver and thyroid adenomas and carcinomas in rats. It is classified as an hazardous substance in the United States as defined in Section 302 of the U. S. Emergency Planning and Community Right-to-Know Act, is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities; the 1927 short story The Avenging Chance by Anthony Berkeley discusses contemporary uses of nitrobenzene. It is at the centre of the plot in Berkeley's The Poisoned Chocolates Case of 1929. In the 1937 Nero Wolfe detective novel The Red Box by Rex Stout, a person is murdered by having oil of mirbane spilled on him in his car. In Belfast, during the Troubles's Bloody Friday, the bombs used contained timers affixed to bags full of nitrobenzene.
International Chemical Safety Card 0065 NIOSH Pocket Guide to Chemical Hazards IARC Monograph: "Nitrobenzene" US EPA factsheet https://patents.google.com/patent/US9113628
Benzene is an organic chemical compound with the chemical formula C6H6. The benzene molecule is composed of six carbon atoms joined in a ring with one hydrogen atom attached to each; as it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is one of the elementary petrochemicals. Due to the cyclic continuous pi bond between the carbon atoms, benzene is classed as an aromatic hydrocarbon, the second -annulene, it is sometimes abbreviated PhH. Benzene is a colorless and flammable liquid with a sweet smell, is responsible for the aroma around petrol stations, it is used as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. As benzene has a high octane number, aromatic derivatives like toluene and xylene comprise up to 25% of gasoline. Benzene itself has been limited to less than 1 % in gasoline. Most non-industrial applications have been limited as well for the same reason.
The word "benzene" derives from "gum benzoin", an aromatic resin known to European pharmacists and perfumers since the 15th century as a product of southeast Asia. An acidic material was derived from benzoin by sublimation, named "flowers of benzoin", or benzoic acid; the hydrocarbon derived from benzoic acid thus acquired benzol, or benzene. Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, giving it the name bicarburet of hydrogen. In 1833, Eilhard Mitscherlich produced it by distilling benzoic lime, he gave the compound the name benzin. In 1836, the French chemist Auguste Laurent named the substance "phène". In 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years Mansfield began the first industrial-scale production of benzene, based on the coal-tar method; the sense developed among chemists that a number of substances were chemically related to benzene, comprising a diverse chemical family.
In 1855, Hofmann used the word "aromatic" to designate this family relationship, after a characteristic property of many of its members. In 1997, benzene was detected in deep space; the empirical formula for benzene was long known, but its polyunsaturated structure, with just one hydrogen atom for each carbon atom, was challenging to determine. Archibald Scott Couper in 1858 and Joseph Loschmidt in 1861 suggested possible structures that contained multiple double bonds or multiple rings, but too little evidence was available to help chemists decide on any particular structure. In 1865, the German chemist Friedrich August Kekulé published a paper in French suggesting that the structure contained a ring of six carbon atoms with alternating single and double bonds; the next year he published a much longer paper in German on the same subject. Kekulé used evidence that had accumulated in the intervening years—namely, that there always appeared to be only one isomer of any monoderivative of benzene, that there always appeared to be three isomers of every disubstituted derivative—now understood to correspond to the ortho and para patterns of arene substitution—to argue in support of his proposed structure.
Kekulé's symmetrical ring could explain these curious facts, as well as benzene's 1:1 carbon-hydrogen ratio. The new understanding of benzene, hence of all aromatic compounds, proved to be so important for both pure and applied chemistry that in 1890 the German Chemical Society organized an elaborate appreciation in Kekulé's honor, celebrating the twenty-fifth anniversary of his first benzene paper. Here Kekulé spoke of the creation of the theory, he said that he had discovered the ring shape of the benzene molecule after having a reverie or day-dream of a snake seizing its own tail. This vision, came to him after years of studying the nature of carbon-carbon bonds; this was 7 years after he had solved the problem of how carbon atoms could bond to up to four other atoms at the same time. Curiously, a similar, humorous depiction of benzene had appeared in 1886 in a pamphlet entitled Berichte der Durstigen Chemischen Gesellschaft, a parody of the Berichte der Deutschen Chemischen Gesellschaft, only the parody had monkeys seizing each other in a circle, rather than snakes as in Kekulé's anecdote.
Some historians have suggested that the parody was a lampoon of the snake anecdote already well known through oral transmission if it had not yet appeared in print. Kekulé's 1890 speech in which this anecdote appeared has been translated into English. If the anecdote is the memory of a real event, circumstances mentioned in the story suggest that it must have happened early in 1862; the cyclic nature of benzene was confirmed by the crystallographer Kathleen Lonsdale in 1929. The German chemist Wilhelm Körner suggested the prefixes ortho-, meta-, para- to distinguish di-substituted benzene derivatives in 1867, it was the German chemist Karl Gräbe who, in 1869, first used the prefixes ortho-, meta-, para- to denote specific relative locations of the substituents on a di-substituted aromatic ring (viz, nap