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74-404: Conc may refer to: Concentration in a chemical mixture Dominika Čonč (born 1993), Slovenian footballer Vladimir Čonč (1928–2012), Croatian footballer Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Conc . If an internal link led you here, you may wish to change

148-493: A kilogram is a milligram , not a microkilogram . The BIPM specifies 24 prefixes for the International System of Units (SI): The base units and the derived units formed as the product of powers of the base units with a numerical factor of one form a coherent system of units . Every physical quantity has exactly one coherent SI unit. For example, 1 m/s = 1 m / (1 s) is the coherent derived unit for velocity. With

222-408: A list of non-SI units accepted for use with SI , including the hour, minute, degree of angle, litre, and decibel. Although the term metric system is often used as an informal alternative name for the International System of Units, other metric systems exist, some of which were in widespread use in the past or are even still used in particular areas. There are also individual metric units such as

296-410: A positive or negative power. It can also be combined with other unit symbols to form compound unit symbols. For example, g/cm is an SI unit of density , where cm is to be interpreted as ( cm ) . Prefixes are added to unit names to produce multiples and submultiples of the original unit. All of these are integer powers of ten, and above a hundred or below a hundredth all are integer powers of

370-511: A single place, bringing to a common center, was used in post-classical Latin in 1550 or earlier, similar terms attested in Italian (1589), Spanish (1589), English (1606), French (1632). Often in informal, non-technical language, concentration is described in a qualitative way, through the use of adjectives such as "dilute" for solutions of relatively low concentration and "concentrated" for solutions of relatively high concentration. To concentrate

444-413: A solution, one must add more solute (for example, alcohol), or reduce the amount of solvent (for example, water). By contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute. Unless two substances are miscible , there exists a concentration at which no further solute will dissolve in a solution. At this point, the solution is said to be saturated . If additional solute

518-569: A specification for units of measurement. The International Bureau of Weights and Measures (BIPM) has described SI as "the modern form of metric system". In 1971 the mole became the seventh base unit of the SI. After the metre was redefined in 1960, the International Prototype of the Kilogram (IPK) was the only physical artefact upon which base units (directly the kilogram and indirectly

592-411: A thousand. For example, kilo- denotes a multiple of a thousand and milli- denotes a multiple of a thousandth, so there are one thousand millimetres to the metre and one thousand metres to the kilometre. The prefixes are never combined, so for example a millionth of a metre is a micrometre , not a millimillimetre . Multiples of the kilogram are named as if the gram were the base unit, so a millionth of

666-594: A version of the CGPM document (NIST SP 330) which clarifies usage for English-language publications that use American English . The concept of a system of units emerged a hundred years before the SI. In the 1860s, James Clerk Maxwell , William Thomson (later Lord Kelvin), and others working under the auspices of the British Association for the Advancement of Science , building on previous work of Carl Gauss , developed

740-421: A wide range. For example, driving distances are normally given in kilometres (symbol km ) rather than in metres. Here the metric prefix ' kilo- ' (symbol 'k') stands for a factor of 1000; thus, 1 km = 1000 m . The SI provides twenty-four metric prefixes that signify decimal powers ranging from 10 to 10 , the most recent being adopted in 2022. Most prefixes correspond to integer powers of 1000;

814-531: Is a decimal and metric system of units established in 1960 and periodically updated since then. The SI has an official status in most countries, including the United States , Canada , and the United Kingdom , although these three countries are among the handful of nations that, to various degrees, also continue to use their customary systems. Nevertheless, with this nearly universal level of acceptance,

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888-441: Is added to a saturated solution, it will not dissolve, except in certain circumstances, when supersaturation may occur. Instead, phase separation will occur, leading to coexisting phases, either completely separated or mixed as a suspension . The point of saturation depends on many variables, such as ambient temperature and the precise chemical nature of the solvent and solute. Concentrations are often called levels , reflecting

962-500: Is defined as the molar concentration c i {\displaystyle c_{i}} divided by an equivalence factor f e q {\displaystyle f_{\mathrm {eq} }} . Since the definition of the equivalence factor depends on context (which reaction is being studied), the International Union of Pure and Applied Chemistry and National Institute of Standards and Technology discourage

1036-512: Is expressed as a number, e.g., 0.18 or 18%. There seems to be no standard notation in the English literature. The letter σ i {\displaystyle \sigma _{i}} used here is normative in German literature (see Volumenkonzentration ). Several other quantities can be used to describe the composition of a mixture. These should not be called concentrations. Normality

1110-458: Is important not to use the unit alone to specify the quantity. As the SI Brochure states, "this applies not only to technical texts, but also, for example, to measuring instruments (i.e. the instrument read-out needs to indicate both the unit and the quantity measured)". Furthermore, the same coherent SI unit may be a base unit in one context, but a coherent derived unit in another. For example,

1184-424: Is kg/kg. However, the deprecated parts-per notation is often used to describe small mass fractions. The mass ratio ζ i {\displaystyle \zeta _{i}} is defined as the mass of a constituent m i {\displaystyle m_{i}} divided by the total mass of all other constituents in a mixture: If m i {\displaystyle m_{i}}

1258-431: Is mol/kg. The mole fraction x i {\displaystyle x_{i}} is defined as the amount of a constituent n i {\displaystyle n_{i}} (in moles) divided by the total amount of all constituents in a mixture n t o t {\displaystyle n_{\mathrm {tot} }} : The SI unit is mol/mol. However, the deprecated parts-per notation

1332-508: Is much smaller than m t o t {\displaystyle m_{\mathrm {tot} }} , the mass ratio is almost identical to the mass fraction. The SI unit is kg/kg. However, the deprecated parts-per notation is often used to describe small mass ratios. Concentration depends on the variation of the volume of the solution with temperature, due mainly to thermal expansion . International System of Units The International System of Units , internationally known by

1406-545: Is not coherent. The principle of coherence was successfully used to define a number of units of measure based on the CGS, including the erg for energy , the dyne for force , the barye for pressure , the poise for dynamic viscosity and the stokes for kinematic viscosity . A French-inspired initiative for international cooperation in metrology led to the signing in 1875 of the Metre Convention , also called Treaty of

1480-410: Is not fundamental or even unique – it is a matter of convention. The system allows for an unlimited number of additional units, called derived units , which can always be represented as products of powers of the base units, possibly with a nontrivial numeric multiplier. When that multiplier is one, the unit is called a coherent derived unit. For example, the coherent derived SI unit of velocity

1554-520: Is not the only way in which a base unit can be determined: the SI Brochure states that "any method consistent with the laws of physics could be used to realise any SI unit". Various consultative committees of the CIPM decided in 2016 that more than one mise en pratique would be developed for determining the value of each unit. These methods include the following: The International System of Units, or SI,

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1628-482: Is often used to describe small mole fractions. The mole ratio r i {\displaystyle r_{i}} is defined as the amount of a constituent n i {\displaystyle n_{i}} divided by the total amount of all other constituents in a mixture: If n i {\displaystyle n_{i}} is much smaller than n t o t {\displaystyle n_{\mathrm {tot} }} ,

1702-468: Is otherwise identical to the SI Brochure. For example, since 1979, the litre may exceptionally be written using either an uppercase "L" or a lowercase "l", a decision prompted by the similarity of the lowercase letter "l" to the numeral "1", especially with certain typefaces or English-style handwriting. The American NIST recommends that within the United States "L" be used rather than "l". Metrologists carefully distinguish between

1776-427: Is the metre per second , with the symbol m/s . The base and coherent derived units of the SI together form a coherent system of units ( the set of coherent SI units ). A useful property of a coherent system is that when the numerical values of physical quantities are expressed in terms of the units of the system, then the equations between the numerical values have exactly the same form, including numerical factors, as

1850-424: Is the inverse of electrical resistance , with the consequence that the siemens is the inverse of the ohm, and similarly, the ohm and siemens can be replaced with a ratio of an ampere and a volt, because those quantities bear a defined relationship to each other. Other useful derived quantities can be specified in terms of the SI base and derived units that have no named units in the SI, such as acceleration, which has

1924-591: The ISO/IEC 80000 series of standards, which define the International System of Quantities (ISQ), specifies base and derived quantities that necessarily have the corresponding SI units. Many non-SI units continue to be used in the scientific, technical, and commercial literature. Some units are deeply embedded in history and culture, and their use has not been entirely replaced by their SI alternatives. The CIPM recognised and acknowledged such traditions by compiling

1998-399: The centimetre–gram–second system of units or cgs system in 1874. The systems formalised the concept of a collection of related units called a coherent system of units. In a coherent system, base units combine to define derived units without extra factors. For example, using meters per second is coherent in a system that uses meter for length and seconds for time, but kilometre per hour

2072-433: The mass of a constituent m i {\displaystyle m_{i}} divided by the volume of the mixture V {\displaystyle V} : The SI unit is kg/m (equal to g/L). The molar concentration c i {\displaystyle c_{i}} is defined as the amount of a constituent n i {\displaystyle n_{i}} (in moles) divided by

2146-658: The speed of light in vacuum c , the hyperfine transition frequency of caesium Δ ν Cs , the Planck constant h , the elementary charge e , the Boltzmann constant k , the Avogadro constant N A , and the luminous efficacy K cd . The nature of the defining constants ranges from fundamental constants of nature such as c to the purely technical constant K cd . The values assigned to these constants were fixed to ensure continuity with previous definitions of

2220-419: The sverdrup and the darcy that exist outside of any system of units. Most of the units of the other metric systems are not recognised by the SI. Sometimes, SI unit name variations are introduced, mixing information about the corresponding physical quantity or the conditions of its measurement; however, this practice is unacceptable with the SI. "Unacceptability of mixing information with units: When one gives

2294-496: The BIPM publishes a mises en pratique , ( French for 'putting into practice; implementation', ) describing the current best practical realisations of the unit. The separation of the defining constants from the definitions of units means that improved measurements can be developed leading to changes in the mises en pratique as science and technology develop, without having to revise the definitions. The published mise en pratique

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2368-475: The IPK. During extraordinary verifications carried out in 2014 preparatory to redefinition of metric standards, continuing divergence was not confirmed. Nonetheless, the residual and irreducible instability of a physical IPK undermined the reliability of the entire metric system to precision measurement from small (atomic) to large (astrophysical) scales. By avoiding the use of an artefact to define units, all issues with

2442-583: The International Committee for Weights and Measures (CIPM ), and the International Bureau of Weights and Measures (BIPM ). All the decisions and recommendations concerning units are collected in a brochure called The International System of Units (SI) , which is published in French and English by the BIPM and periodically updated. The writing and maintenance of the brochure is carried out by one of

2516-475: The Metre Convention". This working document was Practical system of units of measurement . Based on this study, the 10th CGPM in 1954 defined an international system derived six base units: the metre, kilogram, second, ampere, degree Kelvin, and candela. The 9th CGPM also approved the first formal recommendation for the writing of symbols in the metric system when the basis of the rules as they are now known

2590-471: The Metre, by 17 nations. The General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM), which was established by the Metre Convention, brought together many international organisations to establish the definitions and standards of a new system and to standardise the rules for writing and presenting measurements. Initially the convention only covered standards for

2664-402: The SI "has been used around the world as the preferred system of units, the basic language for science, technology, industry, and trade." The only other types of measurement system that still have widespread use across the world are the imperial and US customary measurement systems . The international yard and pound are defined in terms of the SI. The quantities and equations that provide

2738-509: The SI Brochure notes that the name of the unit with the symbol °C is correctly spelled as 'degree Celsius ': the first letter of the name of the unit, 'd', is in lowercase, while the modifier 'Celsius' is capitalised because it is a proper name. The English spelling and even names for certain SI units and metric prefixes depend on the variety of English used. US English uses the spelling deka- , meter , and liter , and International English uses deca- , metre , and litre . The name of

2812-455: The SI unit m/s . A combination of base and derived units may be used to express a derived unit. For example, the SI unit of force is the newton (N), the SI unit of pressure is the pascal (Pa) – and the pascal can be defined as one newton per square metre (N/m ). Like all metric systems, the SI uses metric prefixes to systematically construct, for the same physical quantity, a set of units that are decimal multiples of each other over

2886-490: The SI units. The ISQ is formalised, in part, in the international standard ISO/IEC 80000 , which was completed in 2009 with the publication of ISO 80000-1 , and has largely been revised in 2019–2020. The SI is regulated and continually developed by three international organisations that were established in 1875 under the terms of the Metre Convention . They are the General Conference on Weights and Measures (CGPM ),

2960-403: The abbreviation SI (from French Système international d'unités ), is the modern form of the metric system and the world's most widely used system of measurement . Coordinated by the International Bureau of Weights and Measures (abbreviated BIPM from French : Bureau international des poids et mesures ) it is the only system of measurement with official status in nearly every country in

3034-461: The ampere is a base unit when it is a unit of electric current, but a coherent derived unit when it is a unit of magnetomotive force. According to the SI Brochure, unit names should be treated as common nouns of the context language. This means that they should be typeset in the same character set as other common nouns (e.g. Latin alphabet in English, Cyrillic script in Russian, etc.), following

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3108-428: The ampere, mole and candela) depended for their definition, making these units subject to periodic comparisons of national standard kilograms with the IPK. During the 2nd and 3rd Periodic Verification of National Prototypes of the Kilogram, a significant divergence had occurred between the mass of the IPK and all of its official copies stored around the world: the copies had all noticeably increased in mass with respect to

3182-515: The base units. The SI selects seven units to serve as base units , corresponding to seven base physical quantities. They are the second , with the symbol s , which is the SI unit of the physical quantity of time ; the metre , symbol m , the SI unit of length ; kilogram ( kg , the unit of mass ); ampere ( A , electric current ); kelvin ( K , thermodynamic temperature ); mole ( mol , amount of substance ); and candela ( cd , luminous intensity ). The base units are defined in terms of

3256-445: The base units. After the redefinition, the SI is defined by fixing the numerical values of seven defining constants. This has the effect that the distinction between the base units and derived units is, in principle, not needed, since all units, base as well as derived, may be constructed directly from the defining constants. Nevertheless, the distinction is retained because "it is useful and historically well established", and also because

3330-416: The base units. Twenty-two coherent derived units have been provided with special names and symbols. The seven base units and the 22 coherent derived units with special names and symbols may be used in combination to express other coherent derived units. Since the sizes of coherent units will be convenient for only some applications and not for others, the SI provides twenty-four prefixes which, when added to

3404-401: The coherent set and the multiples and sub-multiples of coherent units formed by using the SI prefixes. The kilogram is the only coherent SI unit whose name and symbol include a prefix. For historical reasons, the names and symbols for multiples and sub-multiples of the unit of mass are formed as if the gram were the base unit. Prefix names and symbols are attached to the unit name gram and

3478-463: The committees of the CIPM. The definitions of the terms "quantity", "unit", "dimension", etc. that are used in the SI Brochure are those given in the international vocabulary of metrology . The brochure leaves some scope for local variations, particularly regarding unit names and terms in different languages. For example, the United States' National Institute of Standards and Technology (NIST) has produced

3552-476: The context in which the SI units are defined are now referred to as the International System of Quantities (ISQ). The ISQ is based on the quantities underlying each of the seven base units of the SI . Other quantities, such as area , pressure , and electrical resistance , are derived from these base quantities by clear, non-contradictory equations. The ISQ defines the quantities that are measured with

3626-595: The corresponding equations between the physical quantities. Twenty-two coherent derived units have been provided with special names and symbols as shown in the table below. The radian and steradian have no base units but are treated as derived units for historical reasons. The derived units in the SI are formed by powers, products, or quotients of the base units and are unlimited in number. Derived units apply to some derived quantities , which may by definition be expressed in terms of base quantities , and thus are not independent; for example, electrical conductance

3700-497: The defining constants. For example, the kilogram is defined by taking the Planck constant h to be 6.626 070 15 × 10  J⋅s , giving the expression in terms of the defining constants All units in the SI can be expressed in terms of the base units, and the base units serve as a preferred set for expressing or analysing the relationships between units. The choice of which and even how many quantities to use as base quantities

3774-410: The definition of a unit and its realisation. The SI units are defined by declaring that seven defining constants have certain exact numerical values when expressed in terms of their SI units. The realisation of the definition of a unit is the procedure by which the definition may be used to establish the value and associated uncertainty of a quantity of the same kind as the unit. For each base unit

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3848-403: The definitions. A consequence is that as science and technologies develop, new and superior realisations may be introduced without the need to redefine the unit. One problem with artefacts is that they can be lost, damaged, or changed; another is that they introduce uncertainties that cannot be reduced by advancements in science and technology. The original motivation for the development of the SI

3922-517: The development of the CGS system. The International System of Units consists of a set of defining constants with corresponding base units, derived units, and a set of decimal-based multipliers that are used as prefixes. The seven defining constants are the most fundamental feature of the definition of the system of units. The magnitudes of all SI units are defined by declaring that seven constants have certain exact numerical values when expressed in terms of their SI units. These defining constants are

3996-534: The electrical units in terms of length, mass, and time using dimensional analysis was beset with difficulties – the dimensions depended on whether one used the ESU or EMU systems. This anomaly was resolved in 1901 when Giovanni Giorgi published a paper in which he advocated using a fourth base unit alongside the existing three base units. The fourth unit could be chosen to be electric current , voltage , or electrical resistance . Electric current with named unit 'ampere'

4070-439: The exception of the kilogram (for which the prefix kilo- is required for a coherent unit), when prefixes are used with the coherent SI units, the resulting units are no longer coherent, because the prefix introduces a numerical factor other than one. For example, the metre, kilometre, centimetre, nanometre, etc. are all SI units of length, though only the metre is a coherent SI unit. The complete set of SI units consists of both

4144-432: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Conc&oldid=1174385889 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Concentration Concentration- , concentratio , action or an act of coming together at

4218-492: The loss, damage, and change of the artefact are avoided. A proposal was made that: The new definitions were adopted at the 26th CGPM on 16 November 2018, and came into effect on 20 May 2019. The change was adopted by the European Union through Directive (EU) 2019/1258. Prior to its redefinition in 2019, the SI was defined through the seven base units from which the derived units were constructed as products of powers of

4292-399: The mental schema of levels on the vertical axis of a graph , which can be high or low (for example, "high serum levels of bilirubin" are concentrations of bilirubin in the blood serum that are greater than normal ). There are four quantities that describe concentration: The mass concentration ρ i {\displaystyle \rho _{i}} is defined as

4366-574: The metre and the kilogram. This became the foundation of the MKS system of units. At the close of the 19th century three different systems of units of measure existed for electrical measurements: a CGS-based system for electrostatic units , also known as the Gaussian or ESU system, a CGS-based system for electromechanical units (EMU), and an International system based on units defined by the Metre Convention for electrical distribution systems. Attempts to resolve

4440-447: The mixture V {\displaystyle V} : The SI unit is 1/m . The volume concentration σ i {\displaystyle \sigma _{i}} (not to be confused with volume fraction ) is defined as the volume of a constituent V i {\displaystyle V_{i}} divided by the volume of the mixture V {\displaystyle V} : Being dimensionless, it

4514-509: The mole ratio is almost identical to the mole fraction. The SI unit is mol/mol. However, the deprecated parts-per notation is often used to describe small mole ratios. The mass fraction w i {\displaystyle w_{i}} is the fraction of one substance with mass m i {\displaystyle m_{i}} to the mass of the total mixture m t o t {\displaystyle m_{\mathrm {tot} }} , defined as: The SI unit

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4588-431: The name and symbol of a coherent unit produce twenty-four additional (non-coherent) SI units for the same quantity; these non-coherent units are always decimal (i.e. power-of-ten) multiples and sub-multiples of the coherent unit. The current way of defining the SI is a result of a decades-long move towards increasingly abstract and idealised formulation in which the realisations of the units are separated conceptually from

4662-453: The only ones that do not are those for 10, 1/10, 100, and 1/100. The conversion between different SI units for one and the same physical quantity is always through a power of ten. This is why the SI (and metric systems more generally) are called decimal systems of measurement units . The grouping formed by a prefix symbol attached to a unit symbol (e.g. ' km ', ' cm ') constitutes a new inseparable unit symbol. This new symbol can be raised to

4736-478: The quantity symbols, formatting of numbers and the decimal marker, expressing measurement uncertainty, multiplication and division of quantity symbols, and the use of pure numbers and various angles. In the United States, the guideline produced by the National Institute of Standards and Technology (NIST) clarifies language-specific details for American English that were left unclear by the SI Brochure, but

4810-465: The unit symbol g respectively. For example, 10  kg is written milligram and mg , not microkilogram and μkg . Several different quantities may share the same coherent SI unit. For example, the joule per kelvin (symbol J/K ) is the coherent SI unit for two distinct quantities: heat capacity and entropy ; another example is the ampere, which is the coherent SI unit for both electric current and magnetomotive force . This illustrates why it

4884-545: The unit whose symbol is t and which is defined according to 1 t = 10  kg is 'metric ton' in US English and 'tonne' in International English. Symbols of SI units are intended to be unique and universal, independent of the context language. The SI Brochure has specific rules for writing them. In addition, the SI Brochure provides style conventions for among other aspects of displaying quantities units:

4958-439: The use of normality. The molality of a solution b i {\displaystyle b_{i}} is defined as the amount of a constituent n i {\displaystyle n_{i}} (in moles) divided by the mass of the solvent m s o l v e n t {\displaystyle m_{\mathrm {solvent} }} ( not the mass of the solution): The SI unit for molality

5032-435: The usual grammatical and orthographical rules of the context language. For example, in English and French, even when the unit is named after a person and its symbol begins with a capital letter, the unit name in running text should start with a lowercase letter (e.g., newton, hertz, pascal) and is capitalised only at the beginning of a sentence and in headings and publication titles . As a nontrivial application of this rule,

5106-401: The volume of the mixture V {\displaystyle V} : The SI unit is mol/m . However, more commonly the unit mol/L (= mol/dm ) is used. The number concentration C i {\displaystyle C_{i}} is defined as the number of entities of a constituent N i {\displaystyle N_{i}} in a mixture divided by the volume of

5180-626: The world, employed in science, technology, industry, and everyday commerce. The SI comprises a coherent system of units of measurement starting with seven base units , which are the second (symbol s, the unit of time ), metre (m, length ), kilogram (kg, mass ), ampere (A, electric current ), kelvin (K, thermodynamic temperature ), mole (mol, amount of substance ), and candela (cd, luminous intensity ). The system can accommodate coherent units for an unlimited number of additional quantities. These are called coherent derived units , which can always be represented as products of powers of

5254-465: Was chosen as the base unit, and the other electrical quantities derived from it according to the laws of physics. When combined with the MKS the new system, known as MKSA, was approved in 1946. In 1948, the 9th CGPM commissioned a study to assess the measurement needs of the scientific, technical, and educational communities and "to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to

5328-402: Was established by the Metre Convention of 1875, brought together many international organisations to establish the definitions and standards of a new system and to standardise the rules for writing and presenting measurements. The system was published in 1960 as a result of an initiative that began in 1948, and is based on the metre–kilogram–second system of units (MKS) combined with ideas from

5402-464: Was laid down. These rules were subsequently extended and now cover unit symbols and names, prefix symbols and names, how quantity symbols should be written and used, and how the values of quantities should be expressed. The 10th CGPM in 1954 resolved to create an international system of units and in 1960, the 11th CGPM adopted the International System of Units , abbreviated SI from the French name Le Système international d'unités , which included

5476-399: Was the diversity of units that had sprung up within the centimetre–gram–second (CGS) systems (specifically the inconsistency between the systems of electrostatic units and electromagnetic units ) and the lack of coordination between the various disciplines that used them. The General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM), which

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