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CAS Registry Number
A CAS REGISTRY NUMBER, also referred to as CASRN or CAS NUMBER, is a unique numerical identifier assigned by Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature (currently including those described from at least 1957 through the present), including organic and inorganic compounds, minerals , isotopes , alloys and nonstructurable materials (UVCBs, of Unknown, Variable Composition, or Biological origin). The Registry maintained by CAS is an authoritative collection of disclosed chemical substance information. It currently identifies more than 129 million organic and inorganic substances and 67 million protein and DNA sequences, plus additional information about each substance. It is updated with around 15,000 additional new substances daily. CONTENTS * 1 Use * 2 Format * 3 Granularity * 4 Search engines * 5 See also * 6 Notes * 7 External links USE _ This section DOES NOT CITE ANY SOURCES . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (June 2017)_ _(Learn how and when to remove this template message )_Historically, chemicals have been identified by a wide variety of synonyms. Frequently these are arcane and constructed according to regional naming conventions relating to chemical formulae, structures or origins
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Identifier
An IDENTIFIER is a name that identifies (that is, labels the identity of) either a unique object or a unique class of objects, where the "object" or class may be an idea, physical object (or class thereof), or physical substance (or class thereof). The abbreviation ID often refers to identity, identification (the process of identifying), or an identifier (that is, an instance of identification). An identifier may be a word, number, letter, symbol, or any combination of those. The words, numbers, letters, or symbols may follow an encoding system (wherein letters, digits, words, or symbols stand for (represent) ideas or longer names) or they may simply be arbitrary. When an identifier follows an encoding system, it is often referred to as a CODE or ID CODE. Identifiers that do not follow any encoding scheme are often said to be ARBITRARY IDS; they are arbitrarily assigned and have no greater meaning. (Sometimes identifiers are called "codes" even when they are actually arbitrary, whether because the speaker believes that they have deeper meaning or simply because he is speaking casually and imprecisely.) The unique identifier (UID) is an identifier that refers to only one instance—only one particular object in the universe
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Chemical Abstracts Service
CHEMICAL ABSTRACTS SERVICE (CAS) is a division of the American Chemical Society . It is a source of chemical information. CAS is located in Columbus, Ohio , United States . CONTENTS * 1 Print periodicals * 2 Databases * 2.1 CAplus * 2.2 Registry * 3 Products * 3.1 STN * 3.2 SciFinder * 3.3 CASSI * 4 History * 5 See also * 6 References * 7 External links PRINT PERIODICALS _Chemical Abstracts_ ABBREVIATED TITLE ( ISO 4 ) _Chem. Abstr._ DISCIPLINE Chemistry (index) LANGUAGE English PUBLICATION DETAILS PUBLISHER Chemical Abstracts Service (United States) PUBLICATION HISTORY 1907-2010 FREQUENCY Weekly INDEXING ISSN 0009-2258 LCCN 09004698 CODEN CHABA8 OCLC NO. 1553947 LINKS * Journal homepage_CHEMICAL ABSTRACTS_ is a periodical index that provides summaries and indexes of disclosures in recently published scientific documents. Approximately 8,000 journals , technical reports , dissertations , conference proceedings , and new books , in any of 50 languages, are monitored yearly, as are patent specifications from 27 countries and two international organizations. _Chemical Abstracts_ ceased print publication on January 1, 2010. DATABASESThe two principal databases that support the different products are CAplus and Registry
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Organic Compounds
An ORGANIC COMPOUND is virtually any chemical compound that contains carbon , although a consensus definition remains elusive and likely arbitrary. Organic compounds are rare terrestrially, but of central importance because all known life is based on organic compounds. The most basic petrochemicals are considered the building blocks of organic chemistry . CONTENTS * 1 Definitions of organic vs inorganic * 2 History * 2.1 Vitalism * 2.2 Modern classification * 3 Classification * 3.1 Natural compounds * 3.2 Synthetic compounds * 3.3 Biotechnology * 4 Databases * 5 Structure determination * 6 See also * 7 References * 8 External links DEFINITIONS OF ORGANIC VS INORGANICFor historical reasons discussed below, a few types of carbon-containing compounds, such as carbides , carbonates , simple oxides of carbon (for example, CO and CO2), and cyanides are considered inorganic . The distinction between _organic and inorganic _ carbon compounds, while "useful in organizing the vast subject of chemistry... is somewhat arbitrary". Organic chemistry is the science concerned with all aspects of organic compounds. Organic synthesis is the methodology of their preparation. HISTORYVITALISM Main article: Vitalism For many centuries, Western alchemists believed in vitalism
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Inorganic Compounds
A chemical compound is termed INORGANIC if it fulfills one or more of the following criteria: * There is an absence of carbon in its composition * It is of a non-biologic origin * It cannot be found or incorporated into a living organismThere is no clear or universally agreed-upon distinction between organic and inorganic compounds. Organic chemists traditionally and generally refer to any molecule containing carbon as an organic compound and by default this means that inorganic chemistry deals with molecules lacking carbon. As many minerals are of biological origin, biologists may distinguish organic from inorganic compounds in a different way that does not hinge on the presence of a carbon atom. Pools of organic matter, for example, that have been metabolically incorporated into living tissues persist in decomposing tissues , but as molecules become oxidized into the open environment, such as atmospheric CO2, this creates a separate pool of inorganic compounds. The International Union of Pure and Applied Chemistry , an agency widely recognized for defining chemical terms, does not offer definitions of inorganic or organic compounds. Hence, the definition for an inorganic versus an organic compound in a multidisciplinary context spans the division between organic life living (or animate) and inorganic non-living (or inanimate) matter
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Mineral
A MINERAL is a naturally occurring chemical compound , usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition , whereas a rock can be an aggregate of different minerals or mineraloids . The study of minerals is called mineralogy . There are over 5,300 known mineral species; as of March 2017 , over 5,230 of these have been approved by the International Mineralogical Association (IMA). The silicate minerals compose over 90% of the Earth\'s crust . The diversity and abundance of mineral species is controlled by the Earth's chemistry. Silicon
Silicon
and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals. Minerals are distinguished by various chemical and physical properties . Differences in chemical composition and crystal structure distinguish the various species, which were determined by the mineral's geological environment when formed. Changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various physical properties, which are related to their chemical structure and composition. Common distinguishing characteristics include crystal structure and habit , hardness , lustre , diaphaneity , colour, streak , tenacity , cleavage , fracture , parting, and specific gravity
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Isotope
ISOTOPES are variants of a particular chemical element which differ in neutron number . All isotopes of a given element have the same number of protons in each atom . The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table . The number of protons within the atom\'s nucleus is called atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons . The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number , and each isotope of a given element has a different mass number. For example, carbon-12 , carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively. CONTENTS * 1 Isotope vs
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Alloys
An ALLOY is a mixture of metals or a mixture of a metal and another element . Alloys are defined by a metallic bonding character. An alloy may be a solid solution of metal elements (a single phase) or a mixture of metallic phases (two or more solutions). Intermetallic compounds are alloys with a defined stoichiometry and crystal structure. Zintl phases are also sometimes considered alloys depending on bond types (see also: Van Arkel-Ketelaar triangle for information on classifying bonding in binary compounds). Alloys are used in a wide variety of applications. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties. In other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are steel , solder , brass , pewter , duralumin , bronze and amalgams . The alloy constituents are usually measured by mass. Alloys are usually classified as substitutional or interstitial alloys , depending on the atomic arrangement that forms the alloy. They can be further classified as homogeneous (consisting of a single phase), or heterogeneous (consisting of two or more phases) or intermetallic
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Check Digit
A CHECK DIGIT is a form of redundancy check used for error detection on identification numbers, such as bank account numbers, which are used in an application where they will at least sometimes be input manually. It is analogous to a binary parity bit used to check for errors in computer-generated data. It consists of one or more digits computed by an algorithm from the other digits (or letters) in the sequence input. With a check digit, one can detect simple errors in the input of a series of characters (usually digits) such as a single mistyped digit or some permutations of two successive digits. CONTENTS * 1 Design * 2 Examples * 2.1 UPC * 2.2 ISBN 10 * 2.3 ISBN 13 * 2.4 EAN (GLN, GTIN, EAN numbers administered by GS1) * 2.5 Other examples of check digits * 2.5.1 International * 2.5.2 In the USA * 2.5.3 In Central America * 2.5.4 In Eurasia * 2.5.5 In Oceania * 3 Algorithms * 4 See also * 5 References * 6 External links DESIGN This section DOES NOT CITE ANY SOURCES . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2010) (Learn how and when to remove this template message ) Check digit algorithms are generally designed to capture human transcription errors
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Modular Arithmetic
In mathematics , MODULAR ARITHMETIC is a system of arithmetic for integers , where numbers "wrap around" upon reaching a certain value—the MODULUS (plural MODULI). The modern approach to modular arithmetic was developed by Carl Friedrich Gauss in his book _ Disquisitiones Arithmeticae _, published in 1801. A familiar use of modular arithmetic is in the 12-hour clock , in which the day is divided into two 12-hour periods. If the time is 7:00 now, then 8 hours later it will be 3:00. Usual addition would suggest that the later time should be 7 + 8 = 15, but this is not the answer because clock time "wraps around" every 12 hours. Because the hour number starts over after it reaches 12, this is arithmetic _modulo_ 12. According to the definition below, 12 is congruent not only to 12 itself, but also to 0, so the time called "12:00" could also be called "0:00", since 12 is congruent to 0 modulo 12. CONTENTS* 1 Definition of congruence relation * 1.1 Examples * 2 Properties * 3 Congruence classes * 4 Residue systems * 4.1 Reduced residue systems * 5 Integers modulo _n_ * 6 Applications * 7 Computational complexity * 8 Example implementations * 9 See also * 10 Notes * 11 References * 12 External links DEFINITION OF CONGRUENCE RELATION This section is about the (mod _n_) notation. For the binary _mod_ operation, see modulo operation
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Water
WATER is a transparent and nearly colorless chemical substance that is the main constituent of Earth's streams , lakes , and oceans , and the fluids of most living organisms . Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms , that are connected by covalent bonds . Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure ; but it often refers also to its solid state (ice ) or its gaseous state (steam or water vapor ). It also occurs in nature as snow , glaciers , ice packs and icebergs , clouds , fog , dew , aquifers , and atmospheric humidity . Water covers 71% of the Earth's surface. It is vital for all known forms of life . On Earth, 96.5% of the planet's crust water is found in seas and oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor , clouds (formed of ice and liquid water suspended in air), and precipitation . Only 2.5% of this water is freshwater , and 98.8% of that water is in ice (excepting ice in clouds) and groundwater . Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products. A greater quantity of water is found in the earth's interior
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Stereoisomer
In stereochemistry , STEREOISOMERS are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers , which share the same molecular formula , but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer. CONTENTS * 1 Enantiomers * 2 Diastereomers * 2.1 Cis–trans and E-Z isomerism * 3 Conformers * 4 Anomers * 5 Atropisomers * 6 More definitions * 7 Le Bel-van\'t Hoff rule * 8 References ENANTIOMERS Main articles: Chirality (chemistry)
Chirality (chemistry)
and Enantiomer
Enantiomer
ENANTIOMERS, also known as OPTICAL ISOMERS, are two stereoisomers that are related to each other by a reflection: They are mirror images of each other that are non-superimposable. Human hands are a macroscopic analog of stereoisomerism. Every stereogenic center in one has the opposite configuration in the other. Two compounds that are enantiomers of each other have the same physical properties, except for the direction in which they rotate polarized light and how they interact with different optical isomers of other compounds. As a result, different enantiomers of a compound may have substantially different biological effects
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Racemic Mixture
In chemistry , a RACEMIC MIXTURE, or RACEMATE /reɪˈsimeɪt/ , is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was racemic acid , which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid . A sample with only a single enantiomer is an _enantiomerically pure_, _enantiopure_ or _homochiral_ compound. CONTENTS * 1 Etymology * 2 Nomenclature * 3 Properties * 4 Crystallization * 5 Resolution * 6 Synthesis * 7 Racemic pharmaceuticals * 8 Wallach\'s rule * 9 See also * 10 References ETYMOLOGYFrom racemic acid found in grapes; from Latin _racemus_, meaning a bunch of grapes. NOMENCLATUREA racemic mixture is denoted by the prefix (±)- or DL- (for sugars the prefix DL- may be used), indicating an equal (1:1) mixture of dextro and levo isomers. Also the prefix _RAC-_ (or _RACEM-_) or the symbols _RS_ and _SR_ (all in _italic_ letters) are used. If the ratio is not 1:1 (or is not known), the prefix (+)/(−), D/L- or D/L- (with a slash) is used instead. The usage of d and l is strongly discouraged by IUPAC . PROPERTIESA racemate is optically inactive , meaning that there is no net rotation of plane-polarized light. Although the two enantiomers rotate plane-polarized light in opposite directions, the rotations cancel because they are present in equal amounts
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Epinephrine
EPINEPHRINE, also known as ADRENALIN or ADRENALINE, is a hormone , neurotransmitter and medication . Epinephrine is normally produced by both the adrenal glands and certain neurons . It plays an important role in the fight-or-flight response by increasing blood flow to muscles, output of the heart , pupil dilation , and blood sugar . It does this by binding to alpha and beta receptors . It is found in many animals and some single cell organisms . Napoleon Cybulski first isolated epinephrine in 1895. As a medication it is used to treat a number of conditions including anaphylaxis , cardiac arrest , and superficial bleeding. Inhaled epinephrine may be used to improve the symptoms of croup . It may also be used for asthma when other treatments are not effective. It is given intravenously , by injection into a muscle, by inhalation, or by injection just under the skin. Common side effects include shakiness, anxiety , and sweating. A fast heart rate and high blood pressure may occur. Occasionally it may result in an abnormal heart rhythm . While the safety of its use during pregnancy and breastfeeding is unclear, the benefits to the mother must be taken into account
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Phase (matter)
In the physical sciences , a PHASE is a region of space (a thermodynamic system ), throughout which all physical properties of a material are essentially uniform. :86 :3 Examples of physical properties include density , index of refraction , magnetization and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air over the water is a third phase. The glass of the jar is another separate phase. (See state of matter#Glass ) 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 term 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 . Because phase boundaries relate to changes in the organization of matter, such as a change from liquid to solid or a more subtle change from one crystal structure to another, this latter usage is similar to the use of "phase" as a synonym for state of matter. However, the state of matter and phase diagram usages are not commensurate with the formal definition given above and the intended meaning must be determined in part from the context in which the term is used
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Carbon
CARBON (from Latin : _carbo_ "coal") 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
Carbon
is one of the few elements known since antiquity . Carbon
Carbon
is the 15th most abundant element in the Earth\'s crust , and the fourth most abundant element in the universe by mass after hydrogen , helium , and oxygen . Carbon's abundance, its unique diversity of organic compounds , and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve as a common element of all known life . It is the second most abundant element in the human body by mass (about 18.5%) 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
Graphite
is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known
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