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A new definition for the mole based on the Avogadro constant: a journey from physics to chemistry.

Milton, M J T (2011) A new definition for the mole based on the Avogadro constant: a journey from physics to chemistry. Philos. Trans. R. Soc. Lond. A, Math. Phys. Eng. Sci., 369 (1953). pp. 3993-4003.

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Abstract

The mole is the most recent addition to the set of SI base units, although the pre-cursor to it, the 'gram-molecule', had been in use by both physicists and chemists for more than 120 years. A proposal has been published recently to establish a new definition for the mole based on a fixed value for the Avogadro Constant. Whilst this would make no change to the system of relative atomic masses ('atomic weights'), it would introduce consistent relative uncertainties for the molar and the atomic masses. Although the proposal would have little impact on the measurement uncertainty of practical work, it has stimulated considerable debate about the mole and the nature of the quantity amount of substance.

In this paper, the rationale for the new definition is explained against the background of changes in the way the quantity amount of substance has been used, from its first use during the early development of thermodynamics through to the use of the 'number of gram molecules' at the end of the nineteenth century.

Item Type: Article
Keywords: mole, amount of substance, Avogadro constant, International System of units, SI
Subjects: Analytical Science
Analytical Science > Gas Standards
Identification number/DOI: 10.1098/rsta.2011.0176
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5238

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