A CAS Registry Number,also referred to as CASRN or CAS Number, is a unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature (currently including all substances described from 1957 through the present, plus some substances from the early or mid 1900s), including organic and inorganic compounds, minerals, isotopes, alloys and nonstructurable materials (UVCBs, substances of unknown or variable composition, complex reaction products, or biological origin).
An identifier is a name that identifies either a unique object or a unique class of objects, where the "object" or class may be an idea, physical [countable] object, or physical [noncountable] substance. The abbreviation ID often refers to identity, identification, or an identifier. An identifier may be a word, number, letter, symbol, or any combination of those.
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.
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be simple substances, chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.
The registry maintained by CAS is an authoritative collection of disclosed chemical substance information. It currently identifies more than 144 million unique 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.
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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. Well-known chemicals may additionally be known via multiple generic, historical, commercial, and/or (black)-market names.
CAS Registry Numbers (CASRN) are simple and regular, convenient for database searches. They offer a reliable, common and international link to every specific substance across the various nomenclatures and disciplines used by branches of science, industry, and regulatory bodies. Almost all molecule databases today allow searching by CAS Registry Number.
On the other hand, CASRNs are not related to chemistry, are proprietary and unrelated to any previous systems, and do not readily form phonetic analogs or synonyms.
A CAS Registry Number has no inherent meaning but is assigned in sequential, increasing order when the substance is identified by CAS scientists for inclusion in the CAS REGISTRY database.
A CASRN is separated by hyphens into three parts, the first consisting from two up to seven digits,the second consisting of two digits, and the third consisting of a single digit serving as a check digit. This current format gives CAS a maximum capacity of 1,000,000,000 unique identifiers.
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 in the sequence input.
The check digit is found by taking the last digit times 1, the preceding digit times 2, the preceding digit times 3 etc., adding all these up and computing the sum modulo 10. For example, the CAS number of water is 7732-18-5: the checksum 5 is calculated as (8×1 + 1×2 + 2×3 + 3×4 + 7×5 + 7×6) = 105; 105 mod 10 = 5.
In mathematics, modular arithmetic is a system of arithmetic for integers, where numbers "wrap around" when reaching a certain value—the modulus. The modern approach to modular arithmetic was developed by Carl Friedrich Gauss in his book Disquisitiones Arithmeticae, published in 1801.
Water is a transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere, and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H2O at standard ambient temperature and pressure. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea.
In chemistry, a racemic mixture, or racemate, 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 or enantiopure compound.
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 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 is a third phase over the ice and water. The glass of the jar is another separate phase.
Carbon is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.
The Canadian Centre for Occupational Health and Safety (CCOHS) is an independent departmental corporation under Schedule II of the Financial Administration Act and is accountable to Parliament through the Minister of Labour.
The United States National Library of Medicine (NLM), operated by the United States federal government, is the world's largest medical library.
The Royal Society of Chemistry (RSC) is a learned society in the United Kingdom with the goal of "advancing the chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society, and the Society for Analytical Chemistry with a new Royal Charter and the dual role of learned society and professional body. At its inception, the Society had a combined membership of 34,000 in the UK and a further 8,000 abroad. The headquarters of the Society are at Burlington House, Piccadilly, London. It also has offices in Thomas Graham House in Cambridge where RSC Publishing is based. The Society has offices in the United States at the University City Science Center, Philadelphia, in both Beijing and Shanghai, China and Bangalore, India. The organisation carries out research, publishes journals, books and databases, as well as hosting conferences, seminars and workshops. It is the professional body for chemistry in the UK, with the ability to award the status of Chartered Chemist (CChem) and, through the Science Council the awards of Chartered Scientist (CSci), Registered Scientist (RSci) and Registered Science Technician (RScTech) to suitably qualified candidates. The designation FRSC is given to a group of elected Fellows of the society who have made major contributions to chemistry and other interface disciplines such as biological chemistry. The names of Fellows are published each year in The Times (London). Honorary Fellowship of the Society ("HonFRSC") is awarded for distinguished service in the field of chemistry.
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To find the CAS number of a compound given its name, formula or structure, the following free resources can be used:
UN numbers are four-digit numbers that identify hazardous materials, and articles in the framework of international transport. Some hazardous substances have their own UN numbers, while sometimes groups of chemicals or products with similar properties receive a common UN number. A chemical in its solid state may receive a different UN number than the liquid phase if their hazardous properties differ significantly; substances with different levels of purity may also receive different UN numbers.
The Merck Index is an encyclopedia of chemicals, drugs and biologicals with over 10,000 monograph on single substances or groups of related compounds published online by the Royal Society of Chemistry.
Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, has a formula of HgO. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is very rarely found.
This article discusses some common molecular file formats, including usage and converting between them.
The IUPAC International Chemical Identifier is a textual identifier for chemical substances, designed to provide a standard way to encode molecular information and to facilitate the search for such information in databases and on the web. Initially developed by IUPAC and NIST from 2000 to 2005, the format and algorithms are non-proprietary.
The Beilstein database is the largest database in the field of organic chemistry, in which compounds are uniquely identified by their Beilstein Registry Number. The database covers the scientific literature from 1771 to the present and contains experimentally validated information on millions of chemical reactions and substances from original scientific publications. The electronic database was created from Beilstein's Handbook of Organic Chemistry, founded by Friedrich Konrad Beilstein in 1881, but has appeared online under a number of different names, including Crossfire Beilstein. Since 2009, the content has been maintained and distributed by Elsevier Information Systems in Frankfurt under the product name "Reaxys".
PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information (NCBI), a component of the National Library of Medicine, which is part of the United States National Institutes of Health (NIH). PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be freely downloaded via FTP. PubChem contains substance descriptions and small molecules with fewer than 1000 atoms and 1000 bonds. More than 80 database vendors contribute to the growing PubChem database.
The European Community number is a unique seven-digit identifier that was assigned to substances for regulatory purposes within the European Union by the European Commission. The EC Inventory comprises three individual inventories, EINECS, ELINCS and the NLP list.
ChemSpider is a database of chemicals. ChemSpider is owned by the Royal Society of Chemistry.
Dichlorodiphenyldichloroethane (DDD) is an organochlorine insecticide that is slightly irritating to the skin. DDD is a metabolite of DDT. DDD is colorless and crystalline; it is closely related chemically and is similar in properties to DDT, but it is considered to be less toxic to animals than DDT. The molecular formula for DDD is (ClC6H4)2CHCHCl2 or C14H10Cl4, whereas the formula for DDT is (ClC6H4)2CHCCl3 or C14H9Cl5.
A chemical compound is a chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds. Two atoms of the same element bonded in a molecule do not form a chemical compound, since this would require two different elements.
2-Fluoroethanol is the chemical compound with the formula CH2FCH2OH and the simplest fluorohydrin. This colorless liquid is one of the simplest stable fluorinated alcohols. It was developed for use as a rodenticide, insecticide, and acaricide. Owing to its easy oxidation to fluoroacetic acid, fluoroethanol is highly toxic (LD50 = 10 mg/kg). The related difluoro- and trifluoroethanols are far less dangerous.
The Hazardous Substances Data Bank (HSDB) is a toxicology database on the U.S. National Library of Medicine's (NLM) Toxicology Data Network (TOXNET). It focuses on the toxicology of potentially hazardous chemicals, and includes information on human exposure, industrial hygiene, emergency handling procedures, environmental fate, regulatory requirements, and related areas. All data are referenced and derived from a core set of books, government documents, technical reports, and selected primary journal literature. All entries are peer-reviewed by a Scientific Review Panel (SRP), members of which represent a spectrum of professions and interests. Current Chairs of the SRP are Dr. Marcel J. Cassavant, MD, Toxicology Group, and Dr. Roland Everett Langford, PhD, Environmental Fate Group.
Chematica is a software/database that uses algorithms and a collective database of 250 years of organic chemical information to predict and provide synthesis pathways for molecules. The software development, led by Bartosz A. Grzybowski, took place for a decade when it was finally publicized in August, 2012.
The CompTox Chemicals Dashboard is a freely accessible online database created and maintained by the U.S. Environmental Protection Agency (EPA). The database provides access to multiple types of data including physicochemical properties, environmental fate and transport, exposure, usage, in vivo toxicity, and in vitro bioassay. EPA and other scientists use the data and models contained within the dashboard to help identify chemicals that require further testing and reduce the use of animals in chemical testing. The Dashboard is also used to provide public access to information from EPA Action Plans, e.g. around perfluorinated alkylated substances.,
Poly(ethyl methacrylate) (PEMA) is a hydrophobic synthetic acrylate polymer. It has properties similar to the more common PMMA, however it produces less heat during polymerization, has a higher modulus of elasticity and an overall softer texture. It may be vulcanized using lead oxide as a catalyst and it can be softened using ethanol.