1.
M-Xylene
–
M-Xylene is an aromatic hydrocarbon, based on benzene with two methyl substituents. It is an isomer of o-xylene and p-xylene, the m stands for meta, meaning the two methyl substituents are at locants 1 and 3 on the aromatic ring. M-Xylene is commonly produced in BTX processes, and separated as needed from the aromatic hydrocarbons. To convert m-xylene on a scale to isophthalic acid, the two methyl groups are both catalytically oxidized to carboxyl groups. It is also used as a raw material in the manufacture of 2, 4- and 2, 6-xylidine as well as a range of smaller-volume chemicals
2.
P-Xylene
–
It is one of the three isomers of dimethylbenzene known collectively as xylenes. The p- stands for para-, indicating that the two groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4, as illustrated here in the schematic representation. It is in the positions of the two groups, their arene substitution pattern, that it differs from the other isomers. Each of the three isomers has two methyl substituents attached to the ring, ignoring the substitution patterns they therefore all have the same chemical formula C6H42. Like all xylene isomers, p-xylene is dangerously flammable, according to convenience, the chemical formula may be represented as C8H10 or C6H42. P-Xylene is a colorless, flammable liquid practically insoluble in water, the boiling point is 138.35 °C and the melting point 13.2 °C. Its specific gravity is 0.86. p-Xylene is highly flammable, the odor threshold of p-xylene is 0.62 parts per million. The production of p-xylene is industrially significant world-wide, with annual demand estimated at 37 million tons in 2014, p-Xylene is produced by catalytic reforming of petroleum naphtha as part of the BTX aromatics extracted from the catalytic reformate. The p-xylene is then separated out in a series of distillation, adsorption or crystallization and reaction processes from the m-xylene, o-xylene and ethylbenzene. Its melting point is the highest among this series of isomers, such separation procedures are major cost factors in the production of p-xylene, and the search for alternative methods continues. For example, a technique has now been proposed to improve various aspects of the processes. P-Xylene is an important chemical feedstock, among other industrial applications, it is a raw material in the large scale synthesis of various polymers. In particular it is a component in the production of acid for polyesters such as polyethylene terephthalate. It also may be polymerised directly to produce parylene, inhaling p-xylene can cause dizziness, headache, drowsiness, and nausea. If exposure through inhalation occurs, first aid includes fresh air, rest, through the use of ventilation or breathing protection, exposure to p-xylene through inhalation can be prevented. Exposure of p-xylene through the skin can cause dry skin and redness, exposure can be prevented through the use of protective gloves. Exposure of p-xylene to eyes can cause redness and pain, if eyes are exposed, first aid includes rinsing of the eyes with water for several minutes, removal of contact lenses if applicable, and medical attention. Eye exposure can be prevented through the use of safety glasses or safety goggles, ingestion of p-xylene can result in a burning sensation, abdominal pain, dizziness, drowsiness, headache, and nausea
3.
Ancient Greek
–
Ancient Greek includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD. It is often divided into the Archaic period, Classical period. It is antedated in the second millennium BC by Mycenaean Greek, the language of the Hellenistic phase is known as Koine. Koine is regarded as a historical stage of its own, although in its earliest form it closely resembled Attic Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects, Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language, Ancient Greek was a pluricentric language, divided into many dialects. The main dialect groups are Attic and Ionic, Aeolic, Arcadocypriot, some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are also several historical forms, homeric Greek is a literary form of Archaic Greek used in the epic poems, the Iliad and Odyssey, and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic, the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period and they have the same general outline, but differ in some of the detail. The invasion would not be Dorian unless the invaders had some relationship to the historical Dorians. The invasion is known to have displaced population to the later Attic-Ionic regions, the Greeks of this period believed there were three major divisions of all Greek people—Dorians, Aeolians, and Ionians, each with their own defining and distinctive dialects. Often non-west is called East Greek, Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, and Northern Peloponnesus Doric. The Lesbian dialect was Aeolic Greek and this dialect slowly replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek, by about the 6th century AD, the Koine had slowly metamorphosized into Medieval Greek
4.
Isomer
–
An isomer is a molecule with the same molecular formula as another molecule, but with a different chemical structure. That is, isomers contain the number of atoms of each element. Isomers do not necessarily share similar properties, unless they also have the functional groups. There are two forms of isomerism, structural isomerism and stereoisomerism. In structural isomers, sometimes referred to as constitutional isomers, the atoms, Structural isomers have different IUPAC names and may or may not belong to the same functional group. For example, two position isomers would be 2-fluoropropane and 1-fluoropropane, illustrated on the side of the diagram above. In skeletal isomers the main chain is different between the two isomers. This type of isomerism is most identifiable in secondary and tertiary alcohol isomers, tautomers are structural isomers that spontaneously interconvert with each other, even when pure. They have different chemical properties and, as a consequence, distinct reactions characteristic to each form are observed, if the interconversion reaction is fast enough, tautomers cannot be isolated from each other. An example is when they differ by the position of a proton, such as in keto/enol tautomerism, there is, however, another isomer of C3H8O that has significantly different properties, methoxyethane. Unlike the isomers of propanol, methoxyethane has an oxygen connected to two carbons rather than to one carbon and one hydrogen. Methoxyethane is an ether, not an alcohol, because it lacks a hydroxyl group, propadiene and propyne are examples of isomers containing different bond types. Propadiene contains two double bonds, whereas propyne contains one triple bond, in stereoisomers the bond structure is the same, but the geometrical positioning of atoms and functional groups in space differs. This class includes enantiomers which are non-superposable mirror-images of each other, and diastereomers, enantiomers always contain chiral centers and diastereomers often do, but there are some diastereomers that neither are chiral nor contain chiral centers. Another type of isomer, conformational isomers, may be rotamers, diastereomers, for example, ortho- position-locked biphenyl systems have enantiomers. E/Z isomers, which have restricted rotation at a bond, are configurational isomers. They are classified as diastereomers, whether or not they contain any chiral centers, e/Z notation depicts absolute stereochemistry, which is an unambiguous descriptor based on CIP priorities. Cis–trans isomers are used to describe any molecules with restricted rotation in the molecule, for molecules with C=C double bonds, these descriptors describe relative stereochemistry only based on group bulkiness or principal carbon chain, and so can be ambiguous
5.
Benzene
–
Benzene is an important organic chemical compound with the chemical formula C6H6. The benzene molecule is composed of 6 carbon atoms joined in a ring with 1 hydrogen atom attached to each, because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a constituent of crude oil and is one of the elementary petrochemicals. Because of the cyclic continuous pi bond between the atoms, benzene is classed as an aromatic hydrocarbon, the second -annulene. Benzene is a colorless and highly flammable liquid with a sweet smell and it is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced. Because benzene has a high number, it is an important component of gasoline. Because benzene is a carcinogen, most non-industrial applications have been limited. The word benzene derives historically from gum benzoin, a resin known to European pharmacists. An acidic material was derived from benzoin by sublimation, and named flowers of benzoin, the hydrocarbon derived from benzoic acid thus acquired the name benzin, benzol, or benzene. Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, in 1833, Eilhard Mitscherlich produced it by distilling benzoic acid and lime. He gave the compound the name benzin, in 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years later, Mansfield began the first industrial-scale production of benzene, gradually, 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, in 1997, benzene was detected in deep space. The empirical formula for benzene was known, but its highly polyunsaturated 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. Kekulés symmetrical ring could explain these facts, as well as benzenes 1,1 carbon-hydrogen ratio. Here Kekulé spoke of the creation of the theory and 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, he said, came to him years of studying the nature of carbon-carbon bonds
6.
Methyl group
–
A methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms — CH3. In formulas, the group is often abbreviated Me, such hydrocarbon groups occur in many organic compounds. It is a stable group in most molecules. While the methyl group is part of a larger molecule. The anion has eight electrons, the radical seven and the cation six. All three forms are highly reactive and rarely observed, the methylium cation exists in the gas phase, but is otherwise not encountered. Some compounds are considered to be sources of the CH3+ cation, the methanide anion exists only in rarefied gas phase or under exotic conditions. It can be produced by electrical discharge in ketene at low pressure, such reagents are generally prepared from the methyl halides, M + CH3X → MCH3 where M is an alkali metal. The methyl radical has the formula CH3 and it exists in dilute gases, but in more concentrated form it readily dimerizes to ethane. It can be produced by decomposition of only certain compounds. The reactivity of a methyl group depends on the adjacent substituents, methyl groups can be quite unreactive. For example, in compounds, the methyl group resists attack by even the strongest acids. The oxidation of a group occurs widely in nature and industry. The oxidation products derived from methyl are CH2OH, CHO, for example, permanganate often converts a methyl group to a carboxyl group, e. g. the conversion of toluene to benzoic acid. Ultimately oxidation of methyl groups gives protons and carbon dioxide, as seen in combustion, demethylation is a common process, and reagents that undergo this reaction are called methylating agents. Common methylating agents are dimethyl sulfate, methyl iodide, and methyl triflate, methanogenesis, the source of natural gas, arises via a demethylation reaction. Certain methyl groups can be deprotonated, for example, the acidity of the methyl groups in acetone is about 1020 more acidic than methane. The resulting carbanions are key intermediates in many reactions in organic synthesis and biosynthesis, fatty acids are produced in this way
7.
Arene substitution pattern
–
Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon. In ortho-substitution, two substituents occupy positions next to other, which may be numbered 1 and 2. In the diagram, these positions are marked R and ortho, in meta-substitution the substituents occupy positions 1 and 3. In para-substitution, the substituents occupy the opposite ends, the toluidines serve as an example for these three types of substitution. Ipso-substitution describes two substituents sharing the same ring position in a compound in an electrophilic aromatic substitution. Me3Si, t-Bu, and iPr groups can form stable carbocation, meso-substitution refers to the substituents occupying a benzylic position. It is observed in such as calixarenes and acridines. Peri-substitution occurs in naphthalenes for substituents at the 1 and 8 positions, in cine-substitution, the entering group takes up a position adjacent to that occupied by the leaving group. For example, cine-substitution is observed in aryne chemistry, tele-substitution occurs when the new position is more than one atom away on the ring. The prefixes ortho, meta, and para are all derived from Greek, meaning correct, following, the relationship to the current meaning is perhaps not obvious. The ortho description was used to designate the original compound. For instance, the trivial names orthophosphoric acid and trimetaphosphoric acid have nothing to do with aromatics at all, likewise, the description para was reserved for just closely related compounds. Thus Berzelius originally called the form of aspartic acid paraaspartic acid in 1830. It was the German chemist Karl Gräbe who, in 1869, first used the prefixes ortho-, in 1870, the German chemist Viktor Meyer first applied Gräbes nomenclature to benzene. The current nomenclature was introduced by the Chemical Society in 1879
8.
Petrochemical
–
Petrochemicals, also called petroleum distillates, are chemical products derived from petroleum. Some chemical compounds made from petroleum are also obtained from fossil fuels, such as coal or natural gas. The two most common classes are olefins and aromatics. Oil refineries produce olefins and aromatics by fluid catalytic cracking of petroleum fractions, chemical plants produce olefins by steam cracking of natural gas liquids like ethane and propane. Aromatics are produced by catalytic reforming of naphtha, Olefins and aromatics are the building-blocks for a wide range of materials such as solvents, detergents, and adhesives. Olefins are the basis for polymers and oligomers used in plastics, resins, fibers, elastomers, lubricants, global ethylene and propylene production are about 115 million tonnes and 70 million tonnes per annum, respectively. Aromatics production is approximately 70 million tonnes, the largest petrochemical industries are located in the USA and Western Europe, however, major growth in new production capacity is in the Middle East and Asia. There is substantial inter-regional petrochemical trade, primary petrochemicals are divided into three groups depending on their chemical structure, Olefins includes ethylene, propylene, and butadiene. Ethylene and propylene are important sources of chemicals and plastics products. Butadiene is used in making synthetic rubber, aromatics includes benzene, toluene, and xylenes. Benzene is a raw material for dyes and synthetic detergents, manufacturers use xylenes to produce plastics and synthetic fibers. Synthesis gas is a mixture of carbon monoxide and hydrogen used to make ammonia, ammonia is used to make the fertilizer urea and methanol is used as a solvent and chemical intermediate. The prefix petro- is an abbreviation of the word petroleum, since petro- is Ancient Greek for rock. Therefore, the correct term would be oleochemicals. However, the term oleochemical is used to describe chemicals derived from plant, benzene, toluene and xylenes, as a whole referred to as BTX and primarily obtained from petroleum refineries by extraction from the reformate produced in catalytic reformers. Methane and BTX are used directly as feedstocks for producing petrochemicals, the output ethylene capacity of large steam crackers ranged up to as much as 1.0 –1.5 Mt per year. Steam crackers are not to be confused with steam reforming plants used to produce hydrogen, like commodity chemicals, petrochemicals are made on a very large scale. Petrochemical manufacturing units differ from commodity chemical plants in that often produce a number of related products
9.
Catalytic reforming
–
The process converts low-octane linear hydrocarbons into branched alkanes and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane, however, the benzene content of reformate makes it carcinogenic, which has led to governmental regulations effectively requiring further processing to reduce its benzene content. Nor is this process to be confused with various other catalytic reforming processes that use methanol or biomass-derived feedstocks to produce hydrogen for fuel cells or other uses. In the 1940s, Vladimir Haensel, a research chemist working for Universal Oil Products, haensels process was subsequently commercialized by UOP in 1949 for producing a high octane gasoline from low octane naphthas and the UOP process become known as the Platforming process. The first Platforming unit was built in 1949 at the refinery of the Old Dutch Refining Company in Muskegon, in the years since then, many other versions of the process have been developed by some of the major oil companies and other organizations. Today, the majority of gasoline produced worldwide is derived from the catalytic reforming process. To name a few of the catalytic reforming versions that were developed, all of which utilized a platinum and/or a rhenium catalyst, Rheniforming. Powerforming, Developed by Esso Oil Company, currently known as ExxonMobil, magnaforming, Developed by Engelhard and Atlantic Richfield Oil Company. Ultraforming, Developed by Standard Oil of Indiana, now a part of the British Petroleum Company, houdriforming, Developed by the Houdry Process Corporation. CCR Platforming, A Platforming version, designed for continuous catalyst regeneration, Octanizing, A catalytic reforming version developed by Axens, a subsidiary of Institut francais du petrole, designed for continuous catalyst regeneration. Before describing the reaction chemistry of the reforming process as used in petroleum refineries. A petroleum refinery includes many unit operations and unit processes, the first unit operation in a refinery is the continuous distillation of the petroleum crude oil being refined. The naphtha is a mixture of many different hydrocarbon compounds. The heavy naphtha has a boiling point of about 140 to 150 °C. The naphthas derived from the distillation of crude oils are referred to as straight-run naphthas and it should be noted that there are a great many petroleum crude oil sources worldwide and each crude oil has its own unique composition or assay. Also, not all refineries process the same crude oils and each refinery produces its own straight-run naphthas with their own unique initial and final boiling points, in other words, naphtha is a generic term rather than a specific term. The table just below lists some fairly typical straight-run heavy naphtha feedstocks, available for catalytic reforming, some refineries may also desulfurize and catalytically reform those naphthas
10.
Carbonization
–
Carbonization is the term for the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation. It is often used in chemistry with reference to the generation of coal gas. Fossil fuels generally are the products of the carbonization of vegetable matter, the term carbonization is also applied to the pyrolysis of coal to produce coke. In the wool processing industry, carbonising is the name for a process by which vegetable matter is removed from wool. Carbonization differs from coalification in that it much faster, due to its reaction rate being faster by many orders of magnitude. For the final temperature, the amount of heat applied controls the degree of carbonization. For example, at T ∼1200 K the carbon content of the residue exceeds a mass fraction of 90 wt. %, whereas at T ∼1600 K more than 99 wt. % carbon is found. Carbonization is often exothermic, which means that it could in principle be made self-sustaining, in the case of glucose, the reaction releases about 237 calories per gram. When biomaterial is exposed to sudden searing heat, it can be carbonized extremely quickly, in the destruction of Herculaneum by a volcano, many organic objects such as furniture were carbonized by the intense heat. The carbonization of wood in a setting usually requires a temperature above 280°C. This carbonization, which can also be seen as a breakdown of the wood. Unless further external heat is provided, the stops and the temperature reaches a maximum of about 400°C. This charcoal, however, will still contain appreciable amounts of tarry residue, carbonisation produces substances which can prove harmful and simple precautions should be taken to reduce risks. The gas produced by carbonization has a content of carbon monoxide which is poisonous when breathed. The tars and smoke produced from carbonization, although not directly poisonous, the tars and pyroligneous liquors can also seriously contaminate streams and affect drinking water supplies for humans and animals. Fish may also be adversely affected, fortunately kilns and pits, as distinct from retorts and other sophisticated systems, do not normally produce liquid effluent - the by-products are mostly dispersed into the air as vapours. Precautions against airborne contamination of the environment are of importance in this case. In one study, carbonization was used to create a new catalyst for the generation of biodiesel from ethanol, the catalyst was created by carbonization of simple sugars such as glucose and sucrose
11.
Coke (fuel)
–
Coke is a fuel with few impurities and a high carbon content, usually made from coal. It is the carbonaceous material derived from destructive distillation of low-ash. Cokes made from coal are grey, hard, and porous, while coke can be formed naturally, the commonly used form is man-made. The form known as coke, or pet coke, is derived from oil refinery coker units or other cracking processes. Coke is used in preparation of producer gas which is a mixture of carbon monoxide, producer gas is produced by passing air over red-hot coke. Coke is also used to water gas. Historical sources dating to the 4th century describe the production of coke in ancient China, the Chinese first used coke for heating and cooking no later than the ninth century. By the first decades of the century, Chinese ironworkers in the Yellow River valley began to fuel their furnaces with coke. In 1589 a patent was granted to Thomas Proctor and William Peterson for making iron and steel and melting lead with earth-coal, sea-coal, turf, the patent contains a distinct allusion to the preparation of coal by cooking. In 1590 a patent was granted to the Dean of York to purify pit-coal, in 1620 a patent was granted to a company composed of William St. John, Robert Follensbee and other knights, mentioning the use of coke in smelting ores and manufacturing metals. In 1627 a patent was granted to Sir John Hacket and Octavius de Strada for a method of rendering sea-coal and pit-coal as useful as charcoal for burning in houses, without offense by smell or smoke. In 1603 Hugh Plat suggested that coal might be charred in an analogous to the way charcoal is produced from wood. In 1709 Abraham Darby I established a coke-fired blast furnace to produce cast iron, cokes superior crushing strength allowed blast furnaces to become taller and larger. The ensuing availability of iron was one of the factors leading to the Industrial Revolution. Before this time, iron-making used large quantities of charcoal, produced by burning wood, in the late 18th century, brick beehive ovens were developed, which allowed more control over the burning process. In 1768 John Wilkinson built a more practical oven for converting coal into coke, with greater skill in the firing, covering and quenching of the heaps, yields were increased from about 33 per cent to 65 per cent by the middle of the 19th century. The Scottish iron industry expanded rapidly in the second quarter of the 19th century. In 1802 a battery of beehives was set up near Sheffield, by 1870, there were 14,000 beehive ovens in operation on the West Durham coalfields, capable of producing 4.2 million tons of coke
12.
Gasoline
–
Gasoline /ˈɡæsəliːn/, known as petrol /ˈpɛtrəl/ outside North America, is a transparent, petroleum-derived liquid that is used primarily as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the distillation of petroleum. On average, a 42-gallon barrel of oil yields about 19 US gallons of gasoline when processed in an oil refinery. The characteristic of a gasoline blend to resist igniting too early is measured by its octane rating. Gasoline is produced in several grades of octane rating, sometimes, gasoline also contains ethanol as an alternative fuel, for economic or environmental reasons. Gasoline, as used worldwide in the vast number of combustion engines used in transport and industry, has a significant impact on the environment. Gasoline may also enter the environment uncombusted, as liquid and as vapors, from leakage and handling during production, transport and delivery, from tanks, from spills. As an example of efforts to control leakage, many storage tanks are required to have extensive measures in place to detect. Gasoline contains benzene and other known carcinogens, Gasoline inhalation can produce an intense high, however the practice is thought to cause severe organ damage, including mental retardation. The first automotive combustion engines, so-called Otto engines, were developed in the last quarter of the 19th century in Germany, the fuel was a relatively volatile hydrocarbon obtained from coal gas. With a boiling point near 85 °C, it was suited for early carburetors. The development of a spray nozzle carburetor enabled the use of less volatile fuels, further improvements in engine efficiency were attempted at higher compression ratios, but early attempts were blocked by knocking. In the 1920s, antiknock compounds were introduced by Thomas Midgley Jr. and Boyd and this innovation started a cycle of improvements in fuel efficiency that coincided with the large-scale development of oil refining to provide more products in the boiling range of gasoline. In the 1950s oil refineries started to focus on high octane fuels, the 1970s witnessed greater attention to the environmental consequences of burning gasoline. These considerations led to the out of TEL and its replacement by other antiknock compounds. Subsequently, low-sulfur gasoline was introduced, in part to preserve the catalysts in modern exhaust systems, Gasoline is the term that is used in North America to refer to the most popular automobile fuel. The Oxford English Dictionary dates the first use to 1863, when it was spelled gasolene and it was never a trademark, although it may have been derived from older trademarks such as Cazeline and Gazeline. Variant spellings of gasoline had been used to refer to raw petroleum since the 16th century, Petrol is the preferred term in most Commonwealth countries
13.
Jet fuel
–
Jet fuel, aviation turbine fuel, or avtur, is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is colorless to straw-colored in appearance, the most commonly used fuels for commercial aviation are Jet A and Jet A-1, which are produced to a standardized international specification. The only other jet fuel used in civilian turbine-engine powered aviation is Jet B. Jet fuel is a mixture of a number of different hydrocarbons. The range of their sizes is defined by the requirements for the product, kerosene-type jet fuel has a carbon number distribution between about 8 and 16, wide-cut or naphtha-type jet fuel, between about 5 and 15. Fuel for piston-engine powered aircraft has a low point to improve its ignition characteristics. Turbine engines can operate with a range of fuels, and jet-aircraft engines typically use fuels with higher flash points. Gasoline was an option but unattractive due to high fuel consumption. Other fuels used were kerosene or kerosene and gasoline mixtures, most jet fuels in use since the end of World War II are kerosene-based. Both British and American standards for jet fuels were first established at the end of World War II, British standards derived from standards for kerosene use for lamps—known as paraffin in the UK—whereas American standards derived from aviation gasoline practices. Over the subsequent years, details of specifications were adjusted, such as freezing point, to balance performance requirements. Very low temperature freezing points reduce the availability of fuel, higher flash point products required for use on aircraft carriers are more expensive to produce. In the United States, ASTM International produces standards for civilian fuel types, the British Ministry of Defence establishes standards for both civil and military jet fuels. For reasons of inter-operational ability, British and United States military standards are harmonized to a degree, both Jet A and Jet A-1 have a flash point higher than 38 °C, with an autoignition temperature of 210 °C. The primary difference is the freezing point of A-1, Jet As is −40 °C Jet A-1s is −47 °C The other difference is the mandatory addition of an anti-static additive to Jet A-1. Jet A trucks, storage tanks, and plumbing that carry Jet A are marked with a sticker with Jet A in white printed on it. Jet A-1 fuel must meet, DEF STAN 91-91, ASTM specification D1655, Jet A fuel must reach ASTM specification D1655 Typical physical properties for Jet A / Jet A-1 Jet B is a fuel in the naphtha-kerosene region that is used for its enhanced cold-weather performance. However, Jet Bs lighter composition makes it dangerous to handle
14.
BTX (chemistry)
–
In the petroleum refining and petrochemical industries, the initialism BTX refers to mixtures of benzene, toluene, and the three xylene isomers, all of which are aromatic hydrocarbons. The xylene isomers are distinguished by the designations ortho –, meta –, if ethylbenzene is included, the mixture is sometimes referred to as BTEX. The BTX aromatics are very important petrochemical materials, global consumption of benzene, estimated at more than 40,000,000 tons in 2010, showed an unprecedented growth of more than 3,000,000 tons from the level seen in 2009. Likewise, the para-xylene consumption showed unprecedented growth in 2010, growing by 2,800,000 tons, toluene is also a valuable petrochemical for use as a solvent and intermediate in chemical manufacturing processes and as a high octane gasoline component. The table below lists some of the properties of the BTX aromatic hydrocarbons, all of which are liquids at room conditions, Benzene, toluene. However, most BTX production is based on the recovery of aromatics derived from the catalytic reforming of naphtha in a petroleum refinery. The pyrolysis gasoline typically consists of C6 to C8 aromatics, heavier aromatics containing 9 to 11 or 12 carbon atoms, about 70 percent of the global production of benzene is by extraction from either reformate or pyrolysis gasoline. The BTX aromatics can be extracted from catalytic reformate or from pyrolysis gasoline by many different methods, most of those methods, but not all, involve the use of a solvent either for liquid-liquid extraction or extractive distillation. Many different solvents are suitable, including sulfolane, furfural, tetraethylene glycol, dimethylsulfoxide, and N-methyl-2-pyrrolidone. The following diagram shows the leading from the BTX components to some of the petrochemicals that can be produced from those components, Aromaticity BTEX Catalysis Pyrolysis J. H. Gary. Donald L. Burdick and William L. Leffler, Benzene Supply Trends and Proposed Method For Enhanced Recovery, David Netzer. Presented to 2005 World Petrochemical Conference, March 2005, Houston, Texas, aromatics Complex, James A. Johnson, Feb.12,2009. From the website of GTC Technology, Houston, Texas
15.
Toluene
–
Toluene /ˈtɒljuːiːn/, also known as toluol /ˈtɒljuːɒl/, is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a benzene derivative, consisting of a CH3 group attached to a phenyl group. As such, its IUPAC systematic name is methylbenzene, Toluene is widely used as an industrial feedstock and a solvent. In 2013, worldwide sales of toluene amounted to about 24.5 billion US-dollars, as the solvent in some types of paint thinner, contact cement and model airplane glue, toluene is sometimes used as a recreational inhalant and has the potential of causing severe neurological harm. The compound was first isolated in 1837 through a distillation of oil by a Polish chemist named Filip Walter. In 1843, Jöns Jacob Berzelius recommended the name toluin, in 1850, French chemist Auguste Cahours isolated from a distillate of wood a hydrocarbon which he recognized as similar to Devilles benzoène and which Cahours named toluène. Toluene reacts as an aromatic hydrocarbon in electrophilic aromatic substitution. Because the methyl group has greater electron-releasing properties than an atom in the same position. It undergoes sulfonation to give p-toluenesulfonic acid, and chlorination by Cl2 in the presence of FeCl3 to give ortho, importantly, the methyl side chain in toluene is susceptible to oxidation. Toluene reacts with Potassium permanganate to yield benzoic acid, and with chromyl chloride to yield benzaldehyde, the methyl group undergoes halogenation under free radical conditions. For example, N-bromosuccinimide heated with toluene in the presence of AIBN leads to benzyl bromide, the same conversion can be effected with elemental bromine in the presence of UV light or even sunlight. Toluene may also be brominated by treating it with HBr and H2O2 in the presence of light. C6H5CH3 + Br2 → C6H5CH2Br + HBr C6H5CH2Br + Br2 → C6H5CHBr2 + HBr The methyl group in toluene undergoes deprotonation only with strong bases. Catalytic hydrogenation of toluene gives methylcyclohexane, the reaction requires a high pressure of hydrogen and a catalyst. Final separation and purification is done by any of the distillation or solvent extraction processes used for BTX aromatics, Toluene is so inexpensively produced industrially that it is not prepared in the laboratory. In principle it could be prepared by a variety of methods, Toluene is mainly used as a precursor to benzene via hydrodealkylation, C6H5CH3 + H2 → C6H6 + CH4 The second ranked application involves its disproportionation to a mixture of benzene and xylene. When oxidized it yields benzaldehyde and benzoic acid, two important intermediates in chemistry, in addition to the synthesis of benzene and xylene, toluene is a feedstock for toluene diisocyanate, trinitrotoluene, and a number of synthetic drugs. Toluene is a solvent, e. g. for paints, paint thinners, silicone sealants, many chemical reactants, rubber, printing ink, adhesives, lacquers, leather tanners
16.
Singapore
–
Singapore, officially the Republic of Singapore, sometimes referred to as the Lion City or the Little Red Dot, is a sovereign city-state in Southeast Asia. It lies one degree north of the equator, at the tip of peninsular Malaysia. Singapores territory consists of one island along with 62 other islets. Since independence, extensive land reclamation has increased its size by 23%. During the Second World War, Singapore was occupied by Japan, after early years of turbulence, and despite lacking natural resources and a hinterland, the nation developed rapidly as an Asian Tiger economy, based on external trade and its workforce. Singapore is a global commerce, finance and transport hub, the country has also been identified as a tax haven. Singapore ranks 5th internationally and first in Asia on the UN Human Development Index and it is ranked highly in education, healthcare, life expectancy, quality of life, personal safety, and housing, but does not fare well on the Democracy index. Although income inequality is high, 90% of homes are owner-occupied, 38% of Singapores 5.6 million residents are permanent residents and other foreign nationals. There are four languages on the island, Malay, Mandarin, Tamil. English is its language, most Singaporeans are bilingual. Singapore is a multiparty parliamentary republic, with a Westminster system of unicameral parliamentary government. The Peoples Action Party has won every election since self-government in 1959, however, it is unlikely that lions ever lived on the island, Sang Nila Utama, the Srivijayan prince said to have founded and named the island Singapura, perhaps saw a Malayan tiger. There are however other suggestions for the origin of the name, the central island has also been called Pulau Ujong as far back as the third century CE, literally island at the end in Malay. In 1299, according to the Malay Annals, the Kingdom of Singapura was founded on the island by Sang Nila Utama and these Indianized Kingdoms, a term coined by George Cœdès were characterized by surprising resilience, political integrity and administrative stability. In 1613, Portuguese raiders burned down the settlement, which by then was part of the Johor Sultanate. The wider maritime region and much trade was under Dutch control for the following period, in 1824 the entire island, as well as the Temenggong, became a British possession after a further treaty with the Sultan. In 1826, Singapore became part of the Straits Settlements, under the jurisdiction of British India, prior to Raffles arrival, there were only about a thousand people living on the island, mostly indigenous Malays along with a handful of Chinese. By 1860 the population had swelled to over 80,000, many of these early immigrants came to work on the pepper and gambier plantations
17.
Tar
–
Tar is a black mixture of hydrocarbons and free carbon obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat, production and trade in pine-derived tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot, the largest user was the Royal Navy. Demand for tar declined with the advent of iron and steel ships, tar-like products can also be produced from other forms of organic matter, such as peat. Mineral products resembling tar can be produced from hydrocarbons, such as petroleum. Coal tar is produced from coal as a byproduct of coke production, Bitumen is a term used for natural deposits of oil tar, such as at the La Brea Tar Pits. In Northern Europe, the word tar refers primarily to a substance that is derived from the wood, in earlier times it was often used as a water repellent coating for boats, ships, and roofs. It is still used as an additive in the flavoring of candy, alcohol, producing tar from wood was known in ancient Greece and has probably been used in Scandinavia since the Iron Age. For centuries, dating back at least to the 14th century, sweden exported 13,000 barrels of tar in 1615 and 227,000 barrels in the peak year of 1863. Production nearly stopped in the early 20th century, when other chemicals replaced tar, traditional wooden boats are still sometimes tarred. The heating of wood causes tar and pitch to drip away from the wood. Birch bark is used to make particularly fine tar, known as Russian oil, the by-products of wood tar are turpentine and charcoal. When deciduous tree woods are subjected to distillation, the products are methanol. Tar kilns are dry distillation ovens, historically used in Scandinavia for producing tar from wood and they were built close to the forest, from limestone or from more primitive holes in the ground. The bottom is sloped into a hole to allow the tar to pour out. The wood is split into dimensions of a finger, stacked densely, if oxygen can enter, the wood might catch fire, and the production would be ruined. On top of this, a fire is stacked and lit, after a few hours, the tar starts to pour out and continues to do so for a few days. Tar was used as seal for roofing shingles and tar paper and to seal the hulls of ships, for millennia, wood tar was used to waterproof sails and boats, but today, sails made from inherently waterproof synthetic substances have reduced the demand for tar
18.
Carbon
–
Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
19.
Atom
–
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms, Atoms are very small, typical sizes are around 100 picometers. Atoms are small enough that attempting to predict their behavior using classical physics - as if they were billiard balls, through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Every atom is composed of a nucleus and one or more bound to the nucleus. The nucleus is made of one or more protons and typically a number of neutrons. Protons and neutrons are called nucleons, more than 99. 94% of an atoms mass is in the nucleus. The protons have an electric charge, the electrons have a negative electric charge. If the number of protons and electrons are equal, that atom is electrically neutral, if an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion. The electrons of an atom are attracted to the protons in a nucleus by this electromagnetic force. The number of protons in the nucleus defines to what chemical element the atom belongs, for example, the number of neutrons defines the isotope of the element. The number of influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the changes observed in nature. The idea that matter is made up of units is a very old idea, appearing in many ancient cultures such as Greece. The word atom was coined by ancient Greek philosophers, however, these ideas were founded in philosophical and theological reasoning rather than evidence and experimentation. As a result, their views on what look like. They also could not convince everybody, so atomism was but one of a number of competing theories on the nature of matter. It was not until the 19th century that the idea was embraced and refined by scientists, in the early 1800s, John Dalton used the concept of atoms to explain why elements always react in ratios of small whole numbers
20.
IUPAC nomenclature of organic chemistry
–
It is published in the Nomenclature of Organic Chemistry. Ideally, every possible organic compound should have a name from which a structural formula can be created. There is also an IUPAC nomenclature of inorganic chemistry, otherwise the common or trivial name may be used, often derived from the source of the compound. In addition, very long names may be less concise than structural formulae, in chemistry, a number of prefixes, suffixes and infixes are used to describe the type and position of functional groups in the compound. The steps for naming an organic compound are, Identification of the parent hydrocarbon chain and this chain must obey the following rules, in order of precedence, It should have the maximum number of substituents of the suffix functional group. By suffix, it is meant that the parent functional group should have a suffix, if more than one functional group is present, the one with highest precedence should be used. It should have the number of multiple bonds It should have the maximum number of single bonds. It should have the maximum length, Identification of the parent functional group, if any, with the highest order of precedence. Side chains are the chains that are not in the parent chain. Identification of the functional groups, if any, and naming them by their ionic prefixes. Different side-chains and functional groups will be grouped together in alphabetical order, when both side chains and secondary functional groups are present, they should be written mixed together in one group rather than in two separate groups. Locants are the numbers on the carbons to which the substituent is directly attached, has the lowest-numbered locants for multiple bonds. Has the lowest-numbered locants for prefixes, numbering of the various substituents and bonds with their locants. If there are two side-chains with the alpha carbon, the number will be written twice. If there are double bonds and triple bonds, en is written before yne. When the main group is a terminal functional group, there is no need to number it. Wherever it says with numbers, it is understood that between the word and the numbers, the prefix is used. Adding of punctuation, Commas are put between numbers Hyphens are put between a number and a letter Successive words are merged into one word Note, IUPAC uses one-word names throughout and this is why all parts are connected
21.
Terephthalic acid
–
Terephthalic acid is the organic compound with formula C6H42. This white solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing, several million tonnes are produced annually. Terephthalic acid was first isolated by the French chemist Amédée Cailliot in 1846, the importance of the terephthalic acid was realized after World War II. The first companies to commercialize the use of the fibers made from polyethylene terephthalate were Imperial Chemical Industries in the UK in 1949, the fibers were made from dimethyl terephthalate by transesterification with ethylene glycol. Terephthalic acid was produced by oxidation of p-xylene with dilute nitric acid and this type of oxidation involved the use of air in the initial oxidation step to minimize the consumption of nitric acid and difficulty in purification. Growth in the industry led to increase in demand of TPA. In the 1960s, all the acid produced was converted to its dimethyl ester, since TPA was infusible. Presently TPA is manufactured by oxidation of p-xylene, Terephthalic acid is poorly soluble in water and alcohols, consequently, until about 1970 terephthalic acid was purified as its dimethyl ester. In the Amoco process, terephthalic acid is produced by oxidation of p-xylene by oxygen in air, the bromide source can be sodium bromide, hydrogen bromide or tetrabromoethane where bromine functions as a regenerative source of free radicals. In this process, acetic acid is the solvent and oxygen from compressed air is the oxidant, the combination of bromine and acetic acid is found to be highly corrosive and hence the equipment is lined with titanium. A feed mixture containing p-xylene, acetic acid, the catalyst system, the oxidation of the methyl group takes place in two steps where p-xylene is converted to p-toluic acid and the byproduct undesirable 4-carboxybenzaldehyde along with crude p-toluic acid. It is further purified to obtain the p-toluic acid with the removal of the 4-carboxybenzaldehyde using crystallization, centrifugation and filtration, 98% of the p-xylene is reacted to give more than 95 mol% TPA. The solvent losses are low, and hence the Amoco process is followed by the industries. This reaction proceeds through a p-toluic acid intermediate which is oxidized to terephthalic acid. The commercial process utilizes acetic acid as solvent and a catalyst composed of cobalt and manganese salts, the most problematic impurity is 4-formylbenzoic acid, which is removed by hydrogenation of a hot aqueous solution. This solution is cooled in a stepwise manner to crystallize highly pure terephthalic acid. Despite optimized yields greater than 95% with excellent purity, the synthesis has shortcomings, due to high reaction temperature, approximately 5% of the acetic acid solvent is lost by decomposition or burning. Solvent burning is a significant economic factor in the oxidation process, in addition, product loss by decarboxylation to benzoic acid is common
22.
Methylation
–
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom by a methyl group. Methylation is a form of alkylation, with a group, rather than a larger carbon chain. These terms are used in chemistry, biochemistry, soil science. Chemical methylation of tissue samples is one method for reducing certain histological staining artifacts. The counterpart of methylation is demethylation, methanogenesis, the process that generated natural gas, is the result of a series of methylation reactions. These methylation reactions are affected by a set of enzymes harbored by a family of anaerobic microbes, in reverse methanogenesis, methane serves as the methylating agent. A wide variety of phenols undergo O-methylation to give anisole derivatives and this process, catalyzed by enzymes such as caffeoyl-CoA O-methyltransferase, is a key reaction in the biosynthesis of lignols, precursors to lignin, a major structural component of plants. Methionine synthase catalyzes the final step in the regeneration of methionine from homocysteine, the overall reaction transforms 5-methyltetrahydrofolate into tetrahydrofolate while transferring a methyl group to Hcy to form Met. In methylcobalamin-dependent forms of the enzyme, the proceeds by two steps in a ping-pong reaction. Then, a Hcy that has coordinated to an enzyme-bound zinc to form a reactive thiolate reacts with the Me-Cob, the activated methyl group is transferred from Me-Cob to the Hcy thiolate, which regenerates Co in Cob, and Met is released from the enzyme. DNA methylation in vertebrates typically occurs at CpG sites and this methylation results in the conversion of the cytosine to 5-methylcytosine. The formation of Me-CpG is catalyzed by the enzyme DNA methyltransferase, human DNA has about 80–90% of CpG sites methylated, but there are certain areas, known as CpG islands, that are GC-rich, wherein none are methylated. These are associated with the promoters of 56% of mammalian genes, one to two percent of the human genome are CpG clusters, and there is an inverse relationship between CpG methylation and transcriptional activity. Methylation contributing to epigenetic inheritance can occur through either DNA methylation or protein methylation, similarly, RNA methylation occurs in different RNA species viz. tRNA, rRNA, mRNA, tmRNA, snRNA, snoRNA, miRNA, and viral RNA. Different catalytic strategies are employed for RNA methylation by a variety of RNA-methyltransferases, RNA methylation is thought to have existed before DNA methylation in the early forms of life evolving on earth. N6-methyladenosine is the most common and abundant methylation modification in RNA molecules present in eukaryotes, 5-methylcytosine also commonly occurs in various RNA molecules. Protein methylation typically takes place on arginine or lysine amino acid residues in the protein sequence, arginine can be methylated once or twice, with either both methyl groups on one terminal nitrogen or one on both nitrogens, by protein arginine methyltransferases. Lysine can be methylated once, twice, or three times by lysine methyltransferases, protein methylation has been most studied in the histones
23.
Ethylbenzene
–
Ethylbenzene is an organic compound with the formula C6H5CH2CH3. It is a flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the industry as an intermediate in the production of styrene, the precursor to polystyrene. In 2012, more than 99% of ethylbenzene produced was consumed in the production of styrene, Ethylbenzene is also used to make other chemicals, in fuel, and as a solvent in inks, rubber adhesives, varnishes, and paints. Ethylbenzene exposure can be determined by testing for the products in urine. Ethylbenzene is a liquid that smells similar to gasoline with a sweet aroma. It has an odor with an odor threshold at 2.3 ppm and a melting point of −95 °C. It is classified as an aromatic hydrocarbon since it is a compound that contains one aromatic ring. Ethylbenzene occurs naturally in coal tar and petroleum, although this is not the source of this compound. The dominant application of ethylbenzene is role as an intermediate in the production of polystyrene. Catalytic dehydrogenation of ethylbenzene gives hydrogen and styrene, C 6H 5CH 2CH3 → C6H5CH=CH2 + H2 As of May 2012, Ethylbenzene is added to gasoline as an anti-knock agent, meaning it reduces engine knocking and increase the octane rating. Ethylbenzene is often found in manufactured products, including pesticides, cellulose acetate, synthetic rubber, paints. Used in the recovery of gas, ethylbenzene may be injected into the ground. Thus, manufacturers of ethylbenzene are the buyers of benzene. Small amounts of ethylbenzene are recovered from the mix of xylenes by superfractioning, in the 1980s a zeolite-based process using vapor phase alkylation, offered a higher purity and yield. Then a liquid phase process was introduced using zeolite catalysts and this offers low benzene-to-ethylene ratios, reducing the size of the required equipment and lowering byproduct production. Approximately 24,700,000 tons were produced in 1999, the acute toxicity of ethylbenzene is low, with an LD50 of about 4 grams per kilogram of body weight. The longer term toxicity and carcinogenicity is ambiguous, eye and throat sensitivity can occur when high level exposure to ethylbenzene in the air occurs
24.
Transalkylation
–
Transalkylation is a chemical reaction involving the transfer of an alkyl group from one organic compound to another. The reaction is used for the transfer of methyl and ethyl groups between benzene rings and this is of particular value in the petrochemical industry to manufacture p-xylene, styrene, and other aromatic compounds. Motivation for using transalkylation reactions is based on a difference in production and demand for benzene, toluene, transalkylation can convert toluene, which is overproduced, into benzene and xylene, which are under-produced. Zeolites are often used as catalysts in transalkylation reactions, transalkylation, as used by the petrochemical industry, is often used to convert toluene into benzene and xylenes. This is achieved through a reaction of toluene in which one toluene molecule transfers its methyl group to another one. The reaction is not selective, and the xylene produced can be ortho, meta, there is a higher demand for para xylene, so it is often separated, and the mixture is allowed to reequilibrate to give more para product. Diethylbenzenes arise as side-products of the alkylation of benzene with ethylene, the reaction occurs via equilibrium, so the product is not pure xylene. Many products are produced with varying numbers of methyl groups, the quantities in which each product is produced depends on the M/R ratio. This is the ratio of the number of groups to the number of benzene rings in all of the substrates. For example, in the disproportionation of toluene, the M/R ratio is 1, side reactions in which alkanes are produced reduce the number of methyl groups available which decreases the M/R ratio. This can be mitigated by adding compounds with numbers of methyl groups. The ratio of products produced depends only on the M/R ratio so different starting materials can produce the same compounds via transalkylation, transalkylation reactions are often performed using zeolite catalysts. Zeolites are crystalline solids composed of AlO4 and SiO4 and these crystals are porous in nature with varying pore size. Zeolites of varying sizes are used to perform transalkylation on different substrates, for example, zeolites with a pore size of 5. 5Å are suitable for trimethylbenzene transalkylations
25.
Zeolite
–
Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts. Based on this, he called the material zeolite, from the Greek ζέω, meaning to boil and λίθος, the classic reference for the field has been Zeolite molecular sieves, structure, chemistry, and use by Donald W. Breck. Zeolites occur naturally but are produced industrially on a large scale. As of September 2016,232 unique zeolite frameworks have been identified, every new zeolite structure that is obtained has to be approved by the International Zeolite Association Structure Commission and receives a three letter designation. Zeolites have a structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+. These positive ions are rather loosely held and can readily be exchanged for others in a contact solution, some of the more common mineral zeolites are analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite. An example of the formula of a zeolite is, Na2Al2Si3O10·2H2O. Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater, Zeolites also crystallize in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basins. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, metals, quartz, for this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential. Zeolites are the members of the family of microporous solids known as molecular sieves mainly consisting of Si, Al, O, and metals including Ti, Sn, Zn. The term molecular sieve refers to a property of these materials. This is due to a very regular structure of molecular dimensions. The maximum size of the molecular or ionic species that can enter the pores of a zeolite is controlled by the dimensions of the channels, therefore, the pores in many zeolites are not cylindrical. Zeolites transform to other minerals under weathering, hydrothermal alteration or metamorphic conditions, the sequence of silica-poor volcanic rocks commonly progresses from, Cowlesite → levyne–offretite → analcime → thomsonite–mesolite-scolecite → chabazite → calcite. Industrially important zeolites are produced synthetically, typical procedures entail heating aqueous solutions of alumina and silica with sodium hydroxide. Equivalent reagents include sodium aluminate and sodium silicate, further variations include changes in the cations to include quaternary ammonium cations. Synthetic zeolites hold some key advantages over their natural analogues, the synthetic materials are manufactured in a uniform, phase-pure state. It is also possible to produce zeolite structures that do not appear in nature, Zeolite A is a well-known example
26.
ZSM-5
–
ZSM-5, Zeolite Socony Mobil–5, is an aluminosilicate zeolite belonging to the pentasil family of zeolites. Patented by Mobil Oil Company in 1975, it is used in the petroleum industry as a heterogeneous catalyst for hydrocarbon isomerization reactions. ZSM-5 is composed of several pentasil units linked together by bridges to form pentasil chains. A pentasil unit consists of eight five-membered rings, in these rings, the vertices are Al or Si and an O is assumed to be bonded between the vertices. The pentasil chains are interconnected by bridges to form corrugated sheets with 10-ring holes. Like the pentasil units, each 10-ring hole has Al or Si as vertices with an O assumed to be bonded between each vertex, adjacent layers of the sheets are related by an inversion point. The estimated pore size of the channel running parallel with the corrugations is 5. 4–5.6 Å. The crystallographic unit cell of ZSM-5 has 96 T sites,192 O sites, and a number of compensating cations depending on the Si/Al ratio and it is a medium pore zeolite with channels defined by ten-membered rings. The synthesis involves three different solutions, the first solution is the source of alumina, sodium ions, and hydroxide ions, in the presence of excess base the alumina will form soluble Al4− ions. The second solution has the tetrapropylammonium cation that acts as a templating agent, the third solution is the source of silica, one of the basic building blocks for the framework structure of a zeolite. Mixing the three solutions produces supersaturated tetrapropylammonium ZSM-5, which can be heated to recrystallize and produce a solid, pentasil-zeolites are defined by their structure type, and more specifically by their X-ray diffraction patterns. ZSM-5 is the name of a pentasil-zeolite. Subsequent publications have disclosed methods of conducting the synthesis of pentasil-zeolites without requiring the very expensive, toxic, still other subsequent publications have disclosed substitutes for these amines. In addition to their expense, toxicity and flammability, such amines are disfavored because they are subject to thermal decomposition which can destroy the zeolite structure, further publications have disclosed modifications of the Argauer and Landolt process directed towards improving the reactivity of the SiO2 and Al2O3 starting materials. ZSM-5 is a zeolite, closely related to ZSM-11. ZSM-5 has a high silicon to aluminum ratio, whenever an Al3+ cation replaces a Si4+ cation, an additional positive charge is required to keep the material charge-neutral. With proton as the cation, the material becomes very acidic, thus the acidity is proportional to the Al content. The very regular 3-D structure and the acidity of ZSM-5 can be utilized for acid-catalyzed reactions such as hydrocarbon isomerization, one such reaction is the isomerization of meta-xylene to para-xylene
27.
Pound (mass)
–
The pound or pound-mass is a unit of mass used in the imperial, United States customary and other systems of measurement. The international standard symbol for the pound is lb. The unit is descended from the Roman libra, the English word pound is cognate with, among others, German Pfund, Dutch pond, and Swedish pund. All ultimately derive from a borrowing into Proto-Germanic of the Latin expression lībra pondō, usage of the unqualified term pound reflects the historical conflation of mass and weight. This accounts for the modern distinguishing terms pound-mass and pound-force, the United States and countries of the Commonwealth of Nations agreed upon common definitions for the pound and the yard. Since 1 July 1959, the avoirdupois pound has been defined as exactly 0.45359237 kg. In the United Kingdom, the use of the pound was implemented in the Weights and Measures Act 1963.9144 metre exactly. An avoirdupois pound is equal to 16 avoirdupois ounces and to exactly 7,000 grains, the conversion factor between the kilogram and the international pound was therefore chosen to be divisible by 7, and an grain is thus equal to exactly 64.79891 milligrams. The US has not adopted the system despite many efforts to do so. Historically, in different parts of the world, at different points in time, and for different applications, the libra is an ancient Roman unit of mass that was equivalent to approximately 328.9 grams. It was divided into 12 unciae, or ounces, the libra is the origin of the abbreviation for pound, lb. A number of different definitions of the pound have historically used in Britain. Amongst these were the avoirdupois pound and the tower, merchants. Historically, the sterling was a tower pound of silver. In 1528, the standard was changed to the Troy pound, the avoirdupois pound, also known as the wool pound, first came into general use c. It was initially equal to 6992 troy grains, the pound avoirdupois was divided into 16 ounces. During the reign of Queen Elizabeth, the pound was redefined as 7,000 troy grains. Since then, the grain has often been a part of the avoirdupois system
28.
Gallon
–
The gallon is a unit of measurement for liquid capacity in both the US customary units and the British imperial systems of measurement. Three significantly different sizes are in current use, the imperial gallon defined as 4, while there is no official symbol for the gallon, gal is in common use. The gallon currently has one definition in the system. Historically, there were many definitions and redefinitions, there were more than a few systems of liquid measurements in the pre-1884 United Kingdom. The imperial fluid ounce is defined as 1⁄160 of a gallon, there are four quarts in a gallon. The US gallon is legally defined as 231 cubic inches, which is exactly 3.785411784 liters, a US liquid gallon of water weighs about 8.34 pounds or 3.78 kilograms at 62 °F, making it about 16. 6% lighter than the imperial gallon. There are four quarts in a gallon, two pints in a quart and 16 US fluid ounces in a US pint, which makes the US fluid ounce equal to 1⁄128 of a US gallon. For example, the volume of products and alcoholic beverages are both referenced to 60 °F in government regulations. This dry measure is one-eighth of a US Winchester bushel of 2150.42 cubic inches, the US dry gallon is not used in commerce, and is not listed in the relevant statute, which jumps from the dry quart to the peck. The Imperial gallon is used in life in the United Kingdom. Gallons used in fuel economy expression in Canada are Imperial gallons, the gallon was removed from the list of legally defined primary units of measure catalogued in the EU directive 80/181/EEC, for trading and official purposes, with effect from 31 December 1994. Under the directive the gallon could still be used – but only as a supplementary or secondary unit, Ireland also passed legislation in response to the EU directive with the effective date being 31 December 1993. Though the gallon has ceased to be the legally defined primary unit, it can still be used in both the UK and Ireland as a supplementary unit. The Imperial gallon continues to be used as a unit of measure in Anguilla, Antigua and Barbuda, the Bahamas, the British Virgin Islands, the Cayman Is. Dominica, Grenada, Montserrat, Myanmar, St. Kitts & Nevis, St. Lucia, and St. Vincent & the Grenadines. Other than the United States, the US gallon is used in Liberia, Belize, Colombia, The Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Nicaragua, and Peru. The United Arab Emirates started selling gasoline by the litre in 2010, along with Guyana, the two former had used the Imperial gallon, and the latter the US gallon until they switched. Antigua and Barbuda plan to switch over to using litres by 2015
29.
Properties of water
–
Water is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue. This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the solvent for its ability to dissolve many substances. This allows it to be the solvent of life and it is the only common substance to exist as a solid, liquid, and gas in nature. Water molecules form hydrogen bonds with other and are strongly polar. This polarity allows it to separate ions in salts and strongly bond to other substances such as alcohols and acids. Water is amphoteric, meaning it is both an acid and a base—it produces H+ and OH− ions by self ionization and this regulates the concentrations of H+ and OH− ions in water. Due to water being a good solvent, it is rarely pure. However, there are many compounds that are essentially, if not completely, insoluble in water, such as fats, oils. The accepted IUPAC name of water is oxidane or simply water, or its equivalent in different languages, oxidane is only intended to be used as the name of the mononuclear parent hydride used for naming derivatives of water by substituent nomenclature. These derivatives commonly have other recommended names, for example, the name hydroxyl is recommended over oxidanyl for the –OH group. The name oxane is explicitly mentioned by the IUPAC as being unsuitable for this purpose, the simplest systematic name of water is hydrogen oxide. This is analogous to related compounds such as hydrogen peroxide, hydrogen sulfide, the polarized form of the water molecule, H+OH−, is also called hydron hydroxide by IUPAC nomenclature. It is a rarely used name of water, and mostly used in various hoaxes or spoofs that call for this chemical to be banned. Other systematic names for water include hydroxic acid, hydroxylic acid, none of these exotic names are used widely. Water is the substance with chemical formula H 2O, one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water is a tasteless, odorless liquid at ambient temperature and pressure, ice also appears colorless, and water vapor is essentially invisible as a gas. The elements surrounding oxygen in the table, nitrogen, fluorine, phosphorus, sulfur and chlorine. The reason that water forms a liquid is that oxygen is more electronegative than all of elements with the exception of fluorine
30.
Chemical formula
–
These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
31.
Simplified molecular-input line-entry system
–
The simplified molecular-input line-entry system is a specification in form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules, the original SMILES specification was initiated in the 1980s. It has since modified and extended. In 2007, a standard called OpenSMILES was developed in the open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. The Environmental Protection Agency funded the project to develop SMILES. It has since modified and extended by others, most notably by Daylight Chemical Information Systems. In 2007, a standard called OpenSMILES was developed by the Blue Obelisk open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, in July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is generally considered to have the advantage of being slightly more human-readable than InChI, the term SMILES refers to a line notation for encoding molecular structures and specific instances should strictly be called SMILES strings. However, the term SMILES is also used to refer to both a single SMILES string and a number of SMILES strings, the exact meaning is usually apparent from the context. The terms canonical and isomeric can lead to confusion when applied to SMILES. The terms describe different attributes of SMILES strings and are not mutually exclusive, typically, a number of equally valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol, algorithms have been developed to generate the same SMILES string for a given molecule, of the many possible strings, these algorithms choose only one of them. This SMILES is unique for each structure, although dependent on the algorithm used to generate it. These algorithms first convert the SMILES to a representation of the molecular structure. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database, there is currently no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, and these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES
32.
Density
–
The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
33.
Phase (matter)
–
In the physical sciences, a phase is a region of space, throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, magnetization, a simple description is that a phase is a region of material that is chemically uniform, physically distinct, and mechanically separable. In a system consisting of ice and water in a jar, the ice cubes are one phase, the water is a second phase. The glass of the jar is another separate phase, the term phase is sometimes used as a synonym for state of matter, but there can be several immiscible phases of the same state of matter. Also, the phase is sometimes used to refer to a set of equilibrium states demarcated in terms of state variables such as pressure and temperature by a phase boundary on a phase diagram. Distinct phases may be described as different states of such as gas, liquid, solid. Useful mesophases between solid and liquid form other states of matter, distinct phases may also exist within a given state of matter. As shown in the diagram for iron alloys, several phases exist for both the solid and liquid states, phases may also be differentiated based on solubility as in polar or non-polar. A mixture of water and oil will separate into two phases. Water has a low solubility in oil, and oil has a low solubility in water. Solubility is the amount of a solute that can dissolve in a solvent before the solute ceases to dissolve. A mixture can separate into more than two phases and the concept of phase separation extends to solids, i. e. solids can form solid solutions or crystallize into distinct crystal phases. Metal pairs that are mutually soluble can form alloys, whereas metal pairs that are mutually insoluble cannot, as many as eight immiscible liquid phases have been observed. Mutually immiscible liquid phases are formed from water, hydrophobic solvents, perfluorocarbons, silicones, several different metals. Not all organic solvents are completely miscible, e. g. a mixture of ethylene glycol, phases do not need to macroscopically separate spontaneously. Emulsions and colloids are examples of immiscible phase pair combinations that do not physically separate, left to equilibration, many compositions will form a uniform single phase, but depending on the temperature and pressure even a single substance may separate into two or more distinct phases. Within each phase, the properties are uniform but between the two phases properties differ, water in a closed jar with an air space over it forms a two phase system. Most of the water is in the phase, where it is held by the mutual attraction of water molecules
34.
Solubility
–
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution. Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0.1 g per 100 mL of solvent. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point. Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization. Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. This is a factor in acidity/alkalinity and much environmental and geochemical work. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis
35.
Aromatic hydrocarbon
–
An aromatic hydrocarbon or arene is a hydrocarbon with sigma bonds and delocalized pi electrons between carbon atoms forming a circle. In contrast, aliphatic hydrocarbons lack this delocalization, the term aromatic was assigned before the physical mechanism determining aromaticity was discovered, the term was coined as such simply because many of the compounds have a sweet or pleasant odour. The configuration of six carbon atoms in compounds is known as a benzene ring, after the simplest possible such hydrocarbon. Aromatic hydrocarbons can be monocyclic or polycyclic, some non-benzene-based compounds called heteroarenes, which follow Hückels rule, are also called aromatic compounds. In these compounds, at least one atom is replaced by one of the heteroatoms oxygen, nitrogen. Benzene, C6H6, is the simplest aromatic hydrocarbon, and it was the first one named as such, the nature of its bonding was first recognized by August Kekulé in the 19th century. Each carbon atom in the cycle has four electrons to share. One goes to the atom, and one each to the two neighbouring carbons. The structure is alternatively illustrated as a circle around the inside of the ring to show six electrons floating around in delocalized molecular orbitals the size of the ring itself. This depiction represents the equivalent nature of the six carbon–carbon bonds all of bond order 1.5, the electrons are visualized as floating above and below the ring with the electromagnetic fields they generate acting to keep the ring flat. The proper use of the symbol is debated, it is used to describe any cyclic π system in some publications, jensen argues that, in line with Robinsons original proposal, the use of the circle symbol should be limited to monocyclic 6 π-electron systems. In this way the symbol for a six-center six-electron bond can be compared to the Y symbol for a three-center two-electron bond. A reaction that forms a compound from an unsaturated or partially unsaturated cyclic precursor is simply called an aromatization. Many laboratory methods exist for the synthesis of arenes from non-arene precursors. Many methods rely on cycloaddition reactions, alkyne trimerization describes the cyclization of three alkynes, in the Dötz reaction an alkyne, carbon monoxide and a chromium carbene complex are the reactants. Diels–Alder reactions of alkynes with pyrone or cyclopentadienone with expulsion of carbon dioxide or carbon monoxide also form arene compounds, in Bergman cyclization the reactants are an enyne plus a hydrogen donor. Arenes are reactants in many organic reactions, in aromatic substitution one substituent on the arene ring, usually hydrogen, is replaced by another substituent. The two main types are electrophilic aromatic substitution when the reagent is an electrophile and nucleophilic aromatic substitution when the reagent is a nucleophile
36.
Melting point
–
The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium, the melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the change from liquid to solid. Because of the ability of some substances to supercool, the point is not considered as a characteristic property of a substance. For most substances, melting and freezing points are approximately equal, for example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures, for example, agar melts at 85 °C and solidifies from 31 °C to 40 °C, such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances the freezing point of water is the same as the melting point, the chemical element with the highest melting point is tungsten, at 3687 K, this property makes tungsten excellent for use as filaments in light bulbs. Many laboratory techniques exist for the determination of melting points, a Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point, differential scanning calorimetry gives information on melting point together with its enthalpy of fusion. A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window, the several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated and with the aid of the melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, the measurement can also be made continuously with an operating process. For instance, oil refineries measure the point of diesel fuel online, meaning that the sample is taken from the process. This allows for more frequent measurements as the sample does not have to be manually collected, for refractory materials the extremely high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees, the spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature, in this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer, for temperatures above the calibration range of the source, an extrapolation technique must be employed
37.
Boiling point
–
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
38.
Viscosity
–
The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the concept of thickness, for example. Viscosity is a property of the fluid which opposes the motion between the two surfaces of the fluid in a fluid that are moving at different velocities. For a given velocity pattern, the stress required is proportional to the fluids viscosity, a fluid that has no resistance to shear stress is known as an ideal or inviscid fluid. Zero viscosity is observed only at low temperatures in superfluids. Otherwise, all fluids have positive viscosity, and are said to be viscous or viscid. A fluid with a high viscosity, such as pitch. The word viscosity is derived from the Latin viscum, meaning mistletoe, the dynamic viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. It can be defined through the situation known as a Couette flow. This fluid has to be homogeneous in the layer and at different shear stresses, if the speed of the top plate is small enough, the fluid particles will move parallel to it, and their speed will vary linearly from zero at the bottom to u at the top. Each layer of fluid will move faster than the one just below it, in particular, the fluid will apply on the top plate a force in the direction opposite to its motion, and an equal but opposite one to the bottom plate. An external force is required in order to keep the top plate moving at constant speed. The magnitude F of this force is found to be proportional to the u and the area A of each plate. The proportionality factor μ in this formula is the viscosity of the fluid, the ratio u/y is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the plates. Isaac Newton expressed the forces by the differential equation τ = μ ∂ u ∂ y, where τ = F/A. This formula assumes that the flow is moving along parallel lines and this equation can be used where the velocity does not vary linearly with y, such as in fluid flowing through a pipe. Use of the Greek letter mu for the dynamic viscosity is common among mechanical and chemical engineers. However, the Greek letter eta is used by chemists, physicists
39.
Safety data sheet
–
A safety data sheet, material safety data sheet, or product safety data sheet is an important component of product stewardship, occupational safety and health, and spill-handling procedures. SDS formats can vary from source to source within a country depending on national requirements, SDSs are a widely used system for cataloging information on chemicals, chemical compounds, and chemical mixtures. SDS information may include instructions for the use and potential hazards associated with a particular material or product. The SDS should be available for reference in the area where the chemicals are being stored or in use, there is also a duty to properly label substances on the basis of physico-chemical, health and/or environmental risk. Labels can include hazard symbols such as the European Union standard symbols, a SDS for a substance is not primarily intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting. It is important to use an SDS specific to country and supplier, as the same product can have different formulations in different countries. The formulation and hazard of a product using a name may vary between manufacturers in the same country. Safety data sheets have made an integral part of the system of Regulation No 1907/2006. The SDS must be supplied in a language of the Member State where the substance or mixture is placed on the market. The 16 sections are, SECTION1, Identification of the substance/mixture, relevant identified uses of the substance or mixture and uses advised against 1.3. Details of the supplier of the safety data sheet 1.4, Emergency telephone number SECTION2, Hazards identification 2.1. Classification of the substance or mixture 2.2, Other hazards SECTION3, Composition/information on ingredients 3.1. Mixtures SECTION4, First aid measures 4.1, Description of first aid measures 4.2. Most important symptoms and effects, both acute and delayed 4.3, indication of any immediate medical attention and special treatment needed SECTION5, Firefighting measures 5.1. Special hazards arising from the substance or mixture 5.3, advice for firefighters SECTION6, Accidental release measure 6.1. Personal precautions, protective equipment and emergency procedures 6.2, methods and material for containment and cleaning up 6.4. Reference to other sections SECTION7, Handling and storage 7.1, conditions for safe storage, including any incompatibilities 7.3. Specific end use SECTION8, Exposure controls/personal protection 8.1, Exposure controls SECTION9, Physical and chemical properties 9.1
40.
Flash point
–
The flash point is the lowest temperature at which vapours of a volatile material will ignite, when given an ignition source. The flash point may sometimes be confused with the autoignition temperature, the fire point is the lowest temperature at which the vapor will keep burning after being ignited and the ignition source removed. The fire point is higher than the point, because at the flash point the vapor may be reliably expected to cease burning when the ignition source is removed. The flash point is a characteristic that is used to distinguish between flammable liquids, such as petrol, and combustible liquids, such as diesel. It is also used to characterize the fire hazards of liquids, all liquids have a specific vapor pressure, which is a function of that liquids temperature and is subject to Boyles Law. As temperature increases, vapor pressure increases, as vapor pressure increases, the concentration of vapor of a flammable or combustible liquid in the air increases. Hence, temperature determines the concentration of vapor of the liquid in the air. The flash point is the lowest temperature at which there will be enough flammable vapor to induce ignition when a source is applied. There are two types of flash point measurement, open cup and closed cup. In open cup devices, the sample is contained in a cup which is heated and, at intervals. The measured flash point will vary with the height of the flame above the liquid surface and, at sufficient height. The best-known example is the Cleveland open cup, in both these types, the cups are sealed with a lid through which the ignition source can be introduced. Closed cup testers normally give lower values for the point than open cup and are a better approximation to the temperature at which the vapour pressure reaches the lower flammable limit. The flash point is an empirical measurement rather than a physical parameter. The measured value will vary with equipment and test protocol variations, including temperature ramp rate, time allowed for the sample to equilibrate, sample volume, methods for determining the flash point of a liquid are specified in many standards. For example, testing by the Pensky-Martens closed cup method is detailed in ASTM D93, IP34, ISO2719, DIN51758, JIS K2265 and AFNOR M07-019. Determination of flash point by the Small Scale closed cup method is detailed in ASTM D3828 and D3278, EN ISO3679 and 3680, cEN/TR15138 Guide to Flash Point Testing and ISO TR29662 Guidance for Flash Point Testing cover the key aspects of flash point testing. Gasoline is a used in a spark-ignition engine
. PMID 21180450.
Chisholm, Hugh, ed. (1911). "Xylene". Encyclopædia Britannica (11th ed.). Cambridge University Press.
Chisholm, Hugh, ed. (1911). "