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77-397: The products are now sold in over 125 countries around the world. In 1905, August Fischer, a dispensing chemist , purchased a small chemical plant aiming to manufacture inks , rubber stamp pads, paints and adhesives. In 1932, Fischer developed a clear synthetic resin adhesive which displayed the ability to affix almost any material. Following the custom of the time to name products in

154-815: A Master of Science or a Doctor of Philosophy (PhD.). Most undergraduate programs emphasize mathematics and physics as well as chemistry, partly because chemistry is also known as " the central science ", thus chemists ought to have a well-rounded knowledge about science. At the Master's level and higher, students tend to specialize in a particular field. Fields of specialization include biochemistry , nuclear chemistry , organic chemistry , inorganic chemistry , polymer chemistry , analytical chemistry , physical chemistry , theoretical chemistry , quantum chemistry , environmental chemistry , and thermochemistry . Postdoctoral experience may be required for certain positions. Workers whose work involves chemistry, but not at

231-817: A candle 's flame takes the shape of a sphere. ). Microgravity combustion research contributes to the understanding of a wide variety of aspects that are relevant to both the environment of a spacecraft (e.g., fire dynamics relevant to crew safety on the International Space Station ) and terrestrial (Earth-based) conditions (e.g., droplet combustion dynamics to assist developing new fuel blends for improved combustion, materials fabrication processes , thermal management of electronic systems , multiphase flow boiling dynamics, and many others). Combustion processes that happen in very small volumes are considered micro-combustion . The high surface-to-volume ratio increases specific heat loss. Quenching distance plays

308-412: A detonation . The type of burning that actually occurs depends on the degree to which the fuel and oxidizer are mixed prior to heating: for example, a diffusion flame is formed if the fuel and oxidizer are separated initially, whereas a premixed flame is formed otherwise. Similarly, the type of burning also depends on the pressure: a detonation, for example, is an autoignitive reaction front coupled to

385-399: A triplet spin state . Bonding can be described with three bonding electron pairs and two antibonding electrons, with spins aligned, such that the molecule has nonzero total angular momentum. Most fuels, on the other hand, are in a singlet state, with paired spins and zero total angular momentum. Interaction between the two is quantum mechanically a " forbidden transition ", i.e. possible with

462-817: A M.S. as professors too (and rarely, some big universities who need part-time or temporary instructors, or temporary staff), but when the positions are scarce and the applicants are many, they might prefer Ph.D. holders instead. Skills that a chemist may need on the job include: Most chemists begin their lives in research laboratories . Many chemists continue working at universities. Other chemists may start companies, teach at high schools or colleges, take samples outside (as environmental chemists ), or work in medical examiner offices or police departments (as forensic chemists ). Some software that chemists may find themselves using include: Increasingly, chemists may also find themselves using artificial intelligence , such as for drug discovery . Chemistry typically

539-403: A Master of Science (M.S.) in chemistry or in a very related discipline may find chemist roles that allow them to enjoy more independence, leadership and responsibility earlier in their careers with less years of experience than those with a bachelor's degree as highest degree. Sometimes, M.S. chemists receive more complex tasks duties in comparison with the roles and positions found by chemists with

616-559: A Ph.D. more often than not. Chemists with a Ph.D. as the highest academic degree are found typically on the research-and-development department of an enterprise and can also hold university positions as professors. Professors for research universities or for big universities usually have a Ph.D., and some research-oriented institutions might require post-doctoral training. Some smaller colleges (including some smaller four-year colleges or smaller non-research universities for undergraduates) as well as community colleges usually hire chemists with

693-604: A bachelor's degree are most commonly involved in positions related to either research assistance (working under the guidance of senior chemists in a research-oriented activity), or, alternatively, they may work on distinct (chemistry-related) aspects of a business, organization or enterprise including aspects that involve quality control, quality assurance, manufacturing, production, formulation, inspection, method validation, visitation for troubleshooting of chemistry-related instruments, regulatory affairs , "on-demand" technical services, chemical analysis for non-research purposes (e.g., as

770-466: A bachelor's degree as their highest academic degree and with the same or close-to-same years of job experience. There are positions that are open only to those that at least have a degree related to chemistry at the master's level. Although good chemists without a Ph.D. degree but with relatively many years of experience may be allowed some applied research positions, the general rule is that Ph.D. chemists are preferred for research positions and are typically

847-444: A cigarette, a short-circuited wire) and the persistent combustion of biomass behind the flaming fronts of wildfires . Spontaneous combustion is a type of combustion that occurs by self-heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self-heating which rapidly accelerates to high temperatures) and finally, ignition. For example, phosphorus self-ignites at room temperature without

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924-435: A combination of education, experience and personal achievements), the higher the responsibility given to that chemist and the more complicated the task might be. Chemistry, as a field, have so many applications that different tasks and objectives can be given to workers or scientists with these different levels of education or experience. The specific title of each job varies from position to position, depending on factors such as

1001-410: A complexity requiring an education with a chemistry degree, are commonly referred to as chemical technicians . Such technicians commonly do such work as simpler, routine analyses for quality control or in clinical laboratories , having an associate degree . A chemical technologist has more education or experience than a chemical technician but less than a chemist, often having a bachelor's degree in

1078-409: A different field of science with also an associate degree in chemistry (or many credits related to chemistry) or having the same education as a chemical technician but more experience. There are also degrees specific to become a chemical technologist, which are somewhat distinct from those required when a student is interested in becoming a professional chemist. A Chemical technologist is more involved in

1155-548: A given offgas temperature, the NOx level is lowest when excess oxygen is kept lowest. Adherence to these two principles is furthered by making material and heat balances on the combustion process. The material balance directly relates the air/fuel ratio to the percentage of O 2 in the combustion gas. The heat balance relates the heat available for the charge to the overall net heat produced by fuel combustion. Additional material and heat balances can be made to quantify

1232-463: A hydroperoxide radical (HOO). This reacts further to give hydroperoxides, which break up to give hydroxyl radicals . There are a great variety of these processes that produce fuel radicals and oxidizing radicals. Oxidizing species include singlet oxygen, hydroxyl, monatomic oxygen, and hydroperoxyl . Such intermediates are short-lived and cannot be isolated. However, non-radical intermediates are stable and are produced in incomplete combustion. An example

1309-507: A legal request, for testing purposes, or for government or non-profit agencies); chemists may also work in environmental evaluation and assessment. Other jobs or roles may include sales and marketing of chemical products and chemistry-related instruments or technical writing. The more experience obtained, the more independence and leadership or management roles these chemists may perform in those organizations. Some chemists with relatively higher experience might change jobs or job position to become

1386-468: A manager of a chemistry-related enterprise, a supervisor, an entrepreneur or a chemistry consultant. Other chemists choose to combine their education and experience as a chemist with a distinct credential to provide different services (e.g., forensic chemists, chemistry-related software development, patent law specialists, environmental law firm staff, scientific news reporting staff, engineering design staff, etc.). In comparison, chemists who have obtained

1463-449: A mixture termed as smoke . Combustion does not always result in fire , because a flame is only visible when substances undergoing combustion vaporize, but when it does, a flame is a characteristic indicator of the reaction. While activation energy must be supplied to initiate combustion (e.g., using a lit match to light a fire), the heat from a flame may provide enough energy to make the reaction self-sustaining. The study of combustion

1540-414: A strong shock wave giving it its characteristic high-pressure peak and high detonation velocity . The act of combustion consists of three relatively distinct but overlapping phases: Efficient process heating requires recovery of the largest possible part of a fuel's heat of combustion into the material being processed. There are many avenues of loss in the operation of a heating process. Typically,

1617-426: A very low probability. To initiate combustion, energy is required to force dioxygen into a spin-paired state, or singlet oxygen . This intermediate is extremely reactive. The energy is supplied as heat , and the reaction then produces additional heat, which allows it to continue. Combustion of hydrocarbons is thought to be initiated by hydrogen atom abstraction (not proton abstraction) from the fuel to oxygen, to give

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1694-445: A vital role in stabilizing the flame in such combustion chambers . Generally, the chemical equation for stoichiometric combustion of a hydrocarbon in oxygen is: For example, the stoichiometric combustion of methane in oxygen is: If the stoichiometric combustion takes place using air as the oxygen source, the nitrogen present in the air ( Atmosphere of Earth ) can be added to the equation (although it does not react) to show

1771-460: Is acetaldehyde produced in the combustion of ethanol . An intermediate in the combustion of carbon and hydrocarbons, carbon monoxide , is of special importance because it is a poisonous gas , but also economically useful for the production of syngas . Solid and heavy liquid fuels also undergo a great number of pyrolysis reactions that give more easily oxidized, gaseous fuels. These reactions are endothermic and require constant energy input from

1848-400: Is 'low' (i.e., 'micro' in the sense of 'small' and not necessarily a millionth of Earth's normal gravity) such that the influence of buoyancy on physical processes may be considered small relative to other flow processes that would be present at normal gravity. In such an environment, the thermal and flow transport dynamics can behave quite differently than in normal gravity conditions (e.g.,

1925-419: Is 1 / (1 + 2 + 7.54) = 9.49% vol. The stoichiometric combustion reaction for C α H β O γ in air: The stoichiometric combustion reaction for C α H β O γ S δ : The stoichiometric combustion reaction for C α H β O γ N δ S ε : The stoichiometric combustion reaction for C α H β O γ F δ : Various other substances begin to appear in significant amounts in combustion products when

2002-439: Is a stub . You can help Misplaced Pages by expanding it . Chemist A chemist (from Greek chēm(ía) alchemy; replacing chymist from Medieval Latin alchemist ) is a graduated scientist trained in the study of chemistry , or an officially enrolled student in the field. Chemists study the composition of matter and its properties. Chemists carefully describe the properties they study in terms of quantities, with detail on

2079-463: Is converted to carbon monoxide , and some of the hydrogens remain unreacted. A complete set of equations for the combustion of a hydrocarbon in the air, therefore, requires an additional calculation for the distribution of oxygen between the carbon and hydrogen in the fuel. The amount of air required for complete combustion is known as the "theoretical air" or "stoichiometric air". The amount of air above this value actually needed for optimal combustion

2156-461: Is derived from the Neo-Latin noun chimista , an abbreviation of alchimista ( alchemist ). Alchemists discovered many chemical processes that led to the development of modern chemistry. Chemistry as we know it today, was invented by Antoine Lavoisier with his law of conservation of mass in 1783. The discoveries of the chemical elements has a long history culminating in the creation of

2233-1094: Is divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry. There is a great deal of overlap between different branches of chemistry, as well as with other scientific fields such as biology, medicine, physics, radiology , and several engineering disciplines. All the above major areas of chemistry employ chemists. Other fields where chemical degrees are useful include astrochemistry (and cosmochemistry ), atmospheric chemistry , chemical engineering , chemo-informatics , electrochemistry , environmental science , forensic science , geochemistry , green chemistry , history of chemistry , materials science , medical science , molecular biology , molecular genetics , nanotechnology , nuclear chemistry , oenology , organometallic chemistry , petrochemistry , pharmacology , photochemistry , phytochemistry , polymer chemistry , supramolecular chemistry and surface chemistry . Chemists may belong to professional societies specifically for professionals and researchers within

2310-581: Is greatly preferred especially as carbon monoxide is a poisonous gas. When breathed, carbon monoxide takes the place of oxygen and combines with some of the hemoglobin in the blood, rendering it unable to transport oxygen. These oxides combine with water and oxygen in the atmosphere, creating nitric acid and sulfuric acids , which return to Earth's surface as acid deposition, or "acid rain." Acid deposition harms aquatic organisms and kills trees. Due to its formation of certain nutrients that are less available to plants such as calcium and phosphorus, it reduces

2387-532: Is harvested for diverse uses such as cooking , production of electricity or industrial or domestic heating. Combustion is also currently the only reaction used to power rockets . Combustion is also used to destroy ( incinerate ) waste, both nonhazardous and hazardous. Oxidants for combustion have high oxidation potential and include atmospheric or pure oxygen , chlorine , fluorine , chlorine trifluoride , nitrous oxide and nitric acid . For instance, hydrogen burns in chlorine to form hydrogen chloride with

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2464-399: Is known as combustion science . Combustion is often a complicated sequence of elementary radical reactions . Solid fuels , such as wood and coal , first undergo endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the heat required to produce more of them. Combustion is often hot enough that incandescent light in the form of either glowing or a flame

2541-428: Is known as the "excess air", and can vary from 5% for a natural gas boiler, to 40% for anthracite coal, to 300% for a gas turbine . Incomplete combustion will occur when there is not enough oxygen to allow the fuel to react completely to produce carbon dioxide and water. It also happens when the combustion is quenched by a heat sink, such as a solid surface or flame trap. As is the case with complete combustion, water

2618-438: Is positively correlated with the risk of heart disease. People who survive severe carbon monoxide poisoning may suffer long-term health problems. Carbon monoxide from the air is absorbed in the lungs which then binds with hemoglobin in human's red blood cells. This reduces the capacity of red blood cells that carry oxygen throughout the body. Smoldering is the slow, low-temperature, flameless form of combustion, sustained by

2695-548: Is produced by incomplete combustion; however, carbon and carbon monoxide are produced instead of carbon dioxide. For most fuels, such as diesel oil, coal, or wood, pyrolysis occurs before combustion. In incomplete combustion, products of pyrolysis remain unburnt and contaminate the smoke with noxious particulate matter and gases. Partially oxidized compounds are also a concern; partial oxidation of ethanol can produce harmful acetaldehyde , and carbon can produce toxic carbon monoxide. The designs of combustion devices can improve

2772-420: Is produced. A simple example can be seen in the combustion of hydrogen and oxygen into water vapor , a reaction which is commonly used to fuel rocket engines . This reaction releases 242   kJ/mol of heat and reduces the enthalpy accordingly (at constant temperature and pressure): Uncatalyzed combustion in air requires relatively high temperatures. Complete combustion is stoichiometric concerning

2849-478: Is referred to by them as 'Uhu'. Another version of the origin of the company's name is that it supplied the glue in kits for a model airplane named "UHU" (Owl). This model design was built by German youngsters for an annual contest named " Der Kleine Uhu " (the small owl) that began around 1950. The contest was very popular, and the glue became a popular item with German hobbyists, so the name stuck. In 1971, Fischer's company, renamed UHU after its leading product,

2926-417: Is the source of oxygen ( O 2 ). In the air, each mole of oxygen is mixed with approximately 3.71  mol of nitrogen. Nitrogen does not take part in combustion, but at high temperatures, some nitrogen will be converted to NO x (mostly NO , with much smaller amounts of NO 2 ). On the other hand, when there is insufficient oxygen to combust the fuel completely, some fuel carbon

3003-510: Is the vapor that burns, not the liquid. Therefore, a liquid will normally catch fire only above a certain temperature: its flash point . The flash point of liquid fuel is the lowest temperature at which it can form an ignitable mix with air. It is the minimum temperature at which there is enough evaporated fuel in the air to start combustion. Combustion of gaseous fuels may occur through one of four distinctive types of burning: diffusion flame , premixed flame , autoignitive reaction front , or as

3080-648: Is theoretically needed to ensure that all the fuel burns. For methane ( CH 4 ) combustion, for example, slightly more than two molecules of oxygen are required. The second principle of combustion management, however, is to not use too much oxygen. The correct amount of oxygen requires three types of measurement: first, active control of air and fuel flow; second, offgas oxygen measurement; and third, measurement of offgas combustibles. For each heating process, there exists an optimum condition of minimal offgas heat loss with acceptable levels of combustibles concentration. Minimizing excess oxygen pays an additional benefit: for

3157-457: The efficiency of a burner during the combustion process. Also, the efficiency of an internal combustion engine can be measured in this way, and some U.S. states and local municipalities use combustion analysis to define and rate the efficiency of vehicles on the road today. Carbon monoxide is one of the products from incomplete combustion . The formation of carbon monoxide produces less heat than formation of carbon dioxide so complete combustion

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3234-410: The flame temperature is above about 1600  K . When excess air is used, nitrogen may oxidize to NO and, to a much lesser extent, to NO 2 . CO forms by disproportionation of CO 2 , and H 2 and OH form by disproportionation of H 2 O . For example, when 1  mol of propane is burned with 28.6  mol of air (120% of the stoichiometric amount),

3311-446: The heat-treatment of metals and for gas carburizing . The general reaction equation for incomplete combustion of one mole of a hydrocarbon in oxygen is: When z falls below roughly 50% of the stoichiometric value, CH 4 can become an important combustion product; when z falls below roughly 35% of the stoichiometric value, elemental carbon may become stable. The products of incomplete combustion can be calculated with

3388-609: The periodic table by Dmitri Mendeleev . The Nobel Prize in Chemistry created in 1901 gives an excellent overview of chemical discovery since the start of the 20th century. At the Washington Academy of Sciences during World War I , it was said that the side with the best chemists would win the war. Jobs for chemists generally require at least a bachelor's degree in chemistry, which takes four years. However, many positions, especially those in research, require

3465-553: The 2015 Hague Ethical Guidelines . The highest honor awarded to chemists is the Nobel Prize in Chemistry , awarded since 1901, by the Royal Swedish Academy of Sciences . Combustion Combustion , or burning , is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant , usually atmospheric oxygen , that produces oxidized, often gaseous products, in

3542-525: The United States and European Union enforce limits to vehicle nitrogen oxide emissions, which necessitate the use of special catalytic converters or treatment of the exhaust with urea (see Diesel exhaust fluid ). The incomplete (partial) combustion of a hydrocarbon with oxygen produces a gas mixture containing mainly CO 2 , CO , H 2 O , and H 2 . Such gas mixtures are commonly prepared for use as protective atmospheres for

3619-424: The aid of a material balance , together with the assumption that the combustion products reach equilibrium . For example, in the combustion of one mole of propane ( C 3 H 8 ) with four moles of O 2 , seven moles of combustion gas are formed, and z is 80% of the stoichiometric value. The three elemental balance equations are: These three equations are insufficient in themselves to calculate

3696-418: The application of heat. Organic materials undergoing bacterial composting can generate enough heat to reach the point of combustion. Combustion resulting in a turbulent flame is the most used for industrial applications (e.g. gas turbines , gasoline engines , etc.) because the turbulence helps the mixing process between the fuel and oxidizer . The term 'micro' gravity refers to a gravitational state that

3773-408: The combustion gas composition. However, at the equilibrium position, the water-gas shift reaction gives another equation: For example, at 1200  K the value of K eq is 0.728. Solving, the combustion gas consists of 42.4% H 2 O , 29.0% CO 2 , 14.7% H 2 , and 13.9% CO . Carbon becomes a stable phase at 1200  K and 1  atm pressure when z is less than 30% of

3850-457: The combustion products contain 3.3% O 2 . At 1400  K , the equilibrium combustion products contain 0.03% NO and 0.002% OH . At 1800  K , the combustion products contain 0.17% NO , 0.05% OH , 0.01% CO , and 0.004% H 2 . Diesel engines are run with an excess of oxygen to combust small particles that tend to form with only a stoichiometric amount of oxygen, necessarily producing nitrogen oxide emissions. Both

3927-400: The dominant loss is sensible heat leaving with the offgas (i.e., the flue gas ). The temperature and quantity of offgas indicates its heat content ( enthalpy ), so keeping its quantity low minimizes heat loss. In a perfect furnace, the combustion air flow would be matched to the fuel flow to give each fuel molecule the exact amount of oxygen needed to cause complete combustion. However, in

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4004-420: The exact roles of these chemistry-related workers as standard for that given level of education. Because of these factors affecting exact job titles with distinct responsibilities, some chemists might begin doing technician tasks while other chemists might begin doing more complicated tasks than those of a technician, such as tasks that also involve formal applied research, management, or supervision included within

4081-915: The field of chemistry, such as the Royal Society of Chemistry in the United Kingdom, the American Chemical Society (ACS) in the United States, or the Institution of Chemists in India. The "Global Chemists' Code of Ethics" suggests several ethical principles that all chemists should follow: This code of ethics was codified in a 2016 conference held in Kuala Lumpur, Malaysia , run by the American Chemical Society. The points listed are inspired by

4158-423: The fuel, where there is no remaining fuel, and ideally, no residual oxidant. Thermodynamically, the chemical equilibrium of combustion in air is overwhelmingly on the side of the products. However, complete combustion is almost impossible to achieve, since the chemical equilibrium is not necessarily reached, or may contain unburnt products such as carbon monoxide , hydrogen and even carbon ( soot or ash). Thus,

4235-486: The heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. It is a typically incomplete combustion reaction. Solid materials that can sustain a smoldering reaction include coal, cellulose , wood , cotton , tobacco , peat , duff , humus , synthetic foams, charring polymers (including polyurethane foam ) and dust . Common examples of smoldering phenomena are the initiation of residential fires on upholstered furniture by weak heat sources (e.g.,

4312-419: The kind of industry, the routine level of the task, the current needs of a particular enterprise, the size of the enterprise or hiring firm, the philosophy and management principles of the hiring firm, the visibility of the competency and individual achievements of the one seeking employment, economic factors such as recession or economic depression , among other factors, so this makes it difficult to categorize

4389-611: The level of molecules and their component atoms . Chemists carefully measure substance proportions, chemical reaction rates, and other chemical properties . In Commonwealth English, pharmacists are often called chemists. Chemists use their knowledge to learn the composition and properties of unfamiliar substances, as well as to reproduce and synthesize large quantities of useful naturally occurring substances and create new artificial substances and useful processes. Chemists may specialize in any number of subdisciplines of chemistry . Materials scientists and metallurgists share much of

4466-402: The liberation of heat and light characteristic of combustion. Although usually not catalyzed, combustion can be catalyzed by platinum or vanadium , as in the contact process . In complete combustion, the reactant burns in oxygen and produces a limited number of products. When a hydrocarbon burns in oxygen, the reaction will primarily yield carbon dioxide and water. When elements are burned,

4543-425: The management and operation of the equipment and instrumentation necessary to perform chemical analyzes than a chemical technician. They are part of the team of a chemical laboratory in which the quality of the raw material, intermediate products and finished products is analyzed. They also perform functions in the areas of environmental quality control and the operational phase of a chemical plant. In addition to all

4620-420: The maximum degree of oxidation, and it can be temperature-dependent. For example, sulfur trioxide is not produced quantitatively by the combustion of sulfur. NO x species appear in significant amounts above about 2,800 °F (1,540 °C), and more is produced at higher temperatures. The amount of NO x is also a function of oxygen excess. In most industrial applications and in fires , air

4697-428: The phenomenon of burning . Fire was a mystical force that transformed one substance into another and thus was of primary interest to mankind. It was fire that led to the discovery of iron and glasses . After gold was discovered and became a precious metal, many people were interested to find a method that could convert other substances into gold. This led to the protoscience called alchemy . The word chemist

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4774-450: The preferred choice for the highest administrative positions on big enterprises involved in chemistry-related duties. Some positions, especially research oriented, will only allow those chemists who are Ph.D. holders. Jobs that involve intensive research and actively seek to lead the discovery of completely new chemical compounds under specifically assigned monetary funds and resources or jobs that seek to develop new scientific theories require

4851-576: The produced smoke is usually toxic and contains unburned or partially oxidized products. Any combustion at high temperatures in atmospheric air , which is 78 percent nitrogen , will also create small amounts of several nitrogen oxides , commonly referred to as NOx , since the combustion of nitrogen is thermodynamically favored at high, but not low temperatures. Since burning is rarely clean, fuel gas cleaning or catalytic converters may be required by law. Fires occur naturally, ignited by lightning strikes or by volcanic products. Combustion ( fire )

4928-463: The productivity of the ecosystem and farms. An additional problem associated with nitrogen oxides is that they, along with hydrocarbon pollutants, contribute to the formation of ground level ozone , a major component of smog. Breathing carbon monoxide causes headache, dizziness, vomiting, and nausea. If carbon monoxide levels are high enough, humans become unconscious or die. Exposure to moderate and high levels of carbon monoxide over long periods

5005-425: The products are primarily the most common oxides. Carbon will yield carbon dioxide , sulfur will yield sulfur dioxide , and iron will yield iron(III) oxide . Nitrogen is not considered to be a combustible substance when oxygen is the oxidant . Still, small amounts of various nitrogen oxides (commonly designated NO x species) form when the air is the oxidative. Combustion is not necessarily favorable to

5082-644: The quality of combustion, such as burners and internal combustion engines . Further improvements are achievable by catalytic after-burning devices (such as catalytic converters ) or by the simple partial return of the exhaust gases into the combustion process. Such devices are required by environmental legislation for cars in most countries. They may be necessary to enable large combustion devices, such as thermal power stations , to reach legal emission standards . The degree of combustion can be measured and analyzed with test equipment. HVAC contractors, firefighters and engineers use combustion analyzers to test

5159-422: The real world, combustion does not proceed in a perfect manner. Unburned fuel (usually CO and H 2 ) discharged from the system represents a heating value loss (as well as a safety hazard). Since combustibles are undesirable in the offgas, while the presence of unreacted oxygen there presents minimal safety and environmental concerns, the first principle of combustion management is to provide more oxygen than

5236-414: The responsibilities of that same job title. The level of supervision given to that chemist also varies in a similar manner, with factors similar to those that affect the tasks demanded for a particular chemist It is important that those interested in a Chemistry degree understand the variety of roles available to them (on average), which vary depending on education and job experience. Those Chemists who hold

5313-460: The same education and skills with chemists. The work of chemists is often related to the work of chemical engineers , who are primarily concerned with the proper design, construction and evaluation of the most cost-effective large-scale chemical plants and work closely with industrial chemists on the development of new processes and methods for the commercial-scale manufacture of chemicals and related products. The roots of chemistry can be traced to

5390-499: The stoichiometric composition of the fuel in air and the composition of the resultant flue gas. Treating all non-oxygen components in air as nitrogen gives a 'nitrogen' to oxygen ratio of 3.77, i.e. (100% − O 2 %) / O 2 % where O 2 % is 20.95% vol: where z = x + y 4 {\displaystyle z=x+{y \over 4}} . For example, the stoichiometric combustion of methane in air is: The stoichiometric composition of methane in air

5467-414: The stoichiometric value, at which point the combustion products contain more than 98% H 2 and CO and about 0.5% CH 4 . Substances or materials which undergo combustion are called fuels . The most common examples are natural gas, propane, kerosene , diesel , petrol, charcoal, coal, wood, etc. Combustion of a liquid fuel in an oxidizing atmosphere actually happens in the gas phase. It

5544-404: The thermal advantage from preheating the combustion air, or enriching it in oxygen. Combustion in oxygen is a chain reaction in which many distinct radical intermediates participate. The high energy required for initiation is explained by the unusual structure of the dioxygen molecule. The lowest-energy configuration of the dioxygen molecule is a stable, relatively unreactive diradical in

5621-412: The training usually given to chemical technologists in their respective degree (or one given via an associate degree), a chemist is also trained to understand more details related to chemical phenomena so that the chemist can be capable of more planning on the steps to achieve a distinct goal via a chemistry-related endeavor. The higher the competency level achieved in the field of chemistry (as assessed via

5698-594: The writing goods sector after birds, Fischer named the glue UHU (pronounced in German as [ˈuːhu] , with / ˈ juː h uː / in being common in many English-speaking countries) after Uhu , the onomatopoeic German name for the eagle-owl , a bird which at the time could still be found in the Black Forest . There is an account of glue being used by British prisoners of war in Germany during WW2 , and this

5775-663: Was taken over by the Beecham Group of England (which subsequently became a part of GlaxoSmithKline ), but regained independence for a few years after a management buyout in 1989. In 1994, UHU became a totally owned subsidiary of the Bolton Group , an Italian manufacturer of branded consumer goods. The company has achieved one world record in Germany , in October 2007. A Ford pickup truck weighing about four tonnes

5852-504: Was suspended from a crane with the help of UHU glue. Two steel parts 7 centimetres (2.8 in) in diameter were glued together with an UHU derivative and were used to connect car and crane hook. This record was subsequently beaten in March 2009 by the German firm Henkel , who lifted a similar Ford truck, this time with a Smart microcar in the back, giving a total weight of 5.02 tonnes. This German corporation or company article

5929-456: Was the first controlled chemical reaction discovered by humans, in the form of campfires and bonfires , and continues to be the main method to produce energy for humanity. Usually, the fuel is carbon , hydrocarbons , or more complicated mixtures such as wood that contain partially oxidized hydrocarbons. The thermal energy produced from the combustion of either fossil fuels such as coal or oil , or from renewable fuels such as firewood ,

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