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Quantities and units in analytical chemistry.

Brown, R J C (2008) Quantities and units in analytical chemistry. Int. J. Env. Anal. Chem., 88 (10). pp. 681-687.

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Analytical chemistry is largely concerned with the determination of the composition of mixtures. The result of analysis for a component in a mixture should comprise a 'numerical value' and a 'unit' in order to express the value of the 'quantity' being measured (and an associated statement of uncertainty, of course). 'Amount of substance', often shortened to 'amount', the quantity used to characterise a number of (chemical) entities, is rarely measured directly in analytical chemistry. In practical usage, the amount, mass or volume of a substance (intensive quantities - those whose magnitude is proportional to the size of the system described) is usually combined with the amount, mass, or volume of the entire mixture (more intensive quantities), to derive quantities that express the composition of mixtures (extensive quantities - those whose magnitude is independent of the size of the system described). These quantities are subtly different and can often be confused and misused, so it is helpful to clarify their meaning and the advantages and drawbacks of their usage.

Item Type: Article
Keywords: Analytical chemistry, units of measurement
Subjects: Analytical Science
Analytical Science > Trace Analysis and Electrochemistry
Last Modified: 23 Jul 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4195

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