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| Nigel Wheatley. |
| This discussion paper, circulated in advance of the 17th meeting of the Consultative Committee for Amount of Substance, addresses the proposed redefinition of the mole in terms of a fixed numerical value for the Avogadro constant. It gives ten reasons why the Avogadro constant should not be given a fixed numerical value in the International System of Units, noting that there would be no metrological benefit from such a change, and that the proposed redefinition would be more conceptually complex that the current one and divorced from practical measurement and historical background. As the conditions for redefinition of the kilogram have not been met, and no mise en pratique has been produced for the proposed new definition, the paper concludes that the... |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/5828/version/1 |
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| Nigel Wheatley. |
| The conventional definition of amount of substance _n_ is as a quantity proportional to number of entities _N_. This implies that n is discrete for small _N_ while _n_ is considered to be continuous at the macroscopic scale, leading to a sorites paradox. A practical criterion is proposed for distinguishing between amount of substance and number of entities, and the implications for the conventional definition of amount of substance are discussed. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2011 |
URL: http://precedings.nature.com/documents/5568/version/1 |
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| Nigel Wheatley. |
| There is a common misconception among educators, and even some metrologists, that the Avogadro constant _N_~A~ is (or should be) a pure number, and not a constant of dimension *N*^–1^ (where *N* is the dimension amount of substance). Amount of substance is measured, and has always been measured, as ratios of other physical quantities, and not in terms of a specified pure number of elementary entities. Hence the Avogadro constant has always been defined in terms of the unit of amount of substance, and not vice versa. The proposed redefinition of the mole in terms of a fixed value of the Avogadro constant would cause additional conceptual complexity for no metrological benefit. |
| Tipo: Manuscript |
Palavras-chave: Chemistry. |
| Ano: 2010 |
URL: http://precedings.nature.com/documents/5138/version/1 |
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