concentration

1. Chemistry the strength of a solution, esp the amount of dissolved substance in a given volume of solvent, usually expressed in moles per cubic metre or cubic decimetre (litre).

2. Economics the degree to which the output or employment in an industry is accounted for by only a few firms

3. another name (esp US) for Pelmanism

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

concentration

The diameter of the telescopic image of a point-source of light, such as a star. The image is increased from point size by unavoidable optical effects in the telescope, specifically diffraction (see Airy disk), and for ground-based telescopes it is further increased by distortion due to atmospheric conditions at the time of observation, i.e. by the seeing.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

concentration

[‚kän·sən′trā·shən]

(chemistry)

In solutions, the mass, volume, or number of moles of solute present in proportion to the amount of solvent or total solution.

(hydrology)

The ratio of the area of the sea covered by ice to the total area of sea surface.

(mathematics)

An operation that provides a relatively sharp boundary to a fuzzy set; for a fuzzy set A with membership function m_A, a concentration of A is a fuzzy set whose membership function has the value [m_A (x)]^αfor every element x, where α is a fixed number that is greater than 1.

(mining engineering)

Separation and accumulation of economic minerals from gangue.

concentration

In communications, the combining of multiple channels into one.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Concentration

in chemistry, the value representing the relative quantity of a given component (independent constituent) in a physicochemical system (mixture, solution, melt). The most commonly used methods of expressing concentration are (1) mass fraction—the ratio of the mass of the given component to the mass of the entire system; this ratio multiplied by 100 yields the concentration in weight percent; (2) atomic, or mole, fraction—the ratio of the number of gram atoms (moles) of a given component to the total number of gram atoms (moles) of the system; this ratio multiplied by 100 yields the concentration in atom (mole) percent; and (3) volume fraction—the ratio of the volume of the given component to the total volume of the system; this ratio multiplied by 100 yields the concentration in volume percent.

The concentration of liquid systems is often expressed by the weight of the substance dissolved in 100 g (sometimes in 1 l) of solvent or by the number of moles of substance per 1,000 moles of solvent. In the study of solutions, the concepts of molarity (the number of moles of solute per 1 l of solvent) and molality (the number of moles of solute per 1,000 grams of solvent) are often used. In volumetric analysis, the concentration is expressed by normality (the number of gram equivalents of the active constituent per 1 l of solution) and by titer (the number of grams of active substance or the substance being determined per 1 ml of solution).

In practice, concentration is determined using both the standard methods of quantitative analysis and certain instrumental methods, which make it possible to perform rapid and sufficiently accurate calculations of the content of the main component (for example, determination of the concentration of aqueous solutions of acids, alkalis, salts, and ethyl alcohol by measuring density with the aid of a hydrometer).

REFERENCES

Anosov, V. Ia, and S. A. Pogodin. Osnovnye nachalafizikokhimicheskogo analiza. Moscow-Leningrad, 1947. Pages 81–83.
Terminologiia termodinamiki; sborniki rekomenduemykh terminov, fasc. 7. Edited by A. M. Terpigorev. Moscow, 1952.
Kireev, V. A. Kurs fizicheskoi khimii. Moscow, 1955. Pages 340–44.
Vinogradov, G. V. Nomogrammy perescheta kontsentratsii. Moscow-Leningrad, 1948.

S. A. POGODIN

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