Redefinition of the kilogram and the impact on its future dissemination

Gläser, Michael; Borys, Michael; Ratschko, D.; Schwartz, Roman

doi:10.1088/0026-1394/47/4/007

Cited by 46 publications

(43 citation statements)

References 21 publications

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“…The result is also a significant step towards demonstrating a successful mise en pratique of a kilogram definition based on a fixed value of the Avogadro constant or of the Planck constant. The agreement between the different realizations is not yet as good as it is required to retire (for the time being) the Pt-Ir kilogram prototype, but, considering the capabilities already developed and the envisaged improvements, it seems to be realistic that the targeted uncertainty may be achieved in the foreseeable future [22].…”

Section: Results and Outlookmentioning

confidence: 99%

The Avogadro constant: determining the number of atoms in a single-crystal ²⁸ Si sphere

Becker

Bettin

2011

Phil. Trans. R. Soc. A.

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The Avogadro constant, the number of entities in an amount of substance of one mole, links the atomic and the macroscopic properties of matter. Since the molar Planck constant-the product of the Planck constant and the Avogadro constant-is very well known via the measurement of the Rydberg constant, the Avogadro constant is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a new definition of the kilogram in terms of a fundamental constant. Here, we describe a new and unique approach to determine the Avogadro constant from the number of atoms in 1 kg single-crystal spheres that are highly enriched with the 28 Si isotope. This approach has enabled us to apply isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, N A = 6.022 140 82(18) × 10 23 mol −1 , is now the most accurate input datum for a new definition of the kilogram.

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Section: Results and Outlookmentioning

confidence: 99%

The Avogadro constant: determining the number of atoms in a single-crystal ²⁸ Si sphere

Becker

Bettin

2011

Phil. Trans. R. Soc. A.

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“…The first attempt to review and quantify all of the necessary elements to achieve continuity was published in 2010 [7] and foresaw the necessity to realize and disseminate mass at the level of 1 kg with a standard uncertainty of 20 µg. This formed the basis for a recommendation made by the CCM in 2010 [8].…”

Section: The Ccm Recommendation G1 (2013)mentioning

confidence: 99%

Towards a new SI: a review of progress made since 2011

2014

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In 2011, the General Conference on Weights and Measures (CGPM) confirmed its intention to adopt new definitions for four of the base units of the SI based on fixed numerical values of selected constants. These will be the kilogram, the ampere, the kelvin and the mole. The CGPM was not able to adopt the new definitions at that time because certain experimental and coordination work was not complete. This paper reviews criteria proposed by the Consultative Committees of the CIPM for such a ‘new SI’ to be adopted and reports on recent progress with work to address them. We also report on work being undertaken to demonstrate that the most important technical aspects of realizing such a new system are practicable. The progress reported here confirms the consensus developing amongst the Consultative Committees and the National Metrology Institutes that it will be possible for the CGPM to adopt these new definitions in 2018.

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“…Mohr.) However, they have been under discussion for more than 10 years, and have been the subject of many published papers (see [6][7][8][9][10][11]). Even assuming that these proposals are approved by the CGPM in 2011, they are still unlikely to be adopted for a further 2-4 years because we await the results of experiments still in progress, which will improve our knowledge of the numerical values for the fundamental constants to be used in the definitions.…”

Section: Definitions and Changes In The Definitions Of The Base Unitsmentioning

confidence: 99%

Adapting the International System of Units to the twenty-first century

Mills

Mohr

Quinn

et al. 2011

Phil. Trans. R. Soc. A.

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We review the proposal of the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM), currently being considered by the General Conference on Weights and Measures (Conférences Générales des Poids et Mesures, CGPM), to revise the International System of Units (Le Système International d'Unitès, SI). The proposal includes new definitions for four of the seven base units of the SI, and a new form of words to present the definitions of all the units. The objective of the proposed changes is to adopt definitions referenced to constants of nature, taken in the widest sense, so that the definitions may be based on what are believed to be true invariants. In particular, whereas in the current SI the kilogram, ampere, kelvin and mole are linked to exact numerical values of the mass of the international prototype of the kilogram, the magnetic constant (permeability of vacuum), the triple-point temperature of water and the molar mass of carbon-12, respectively, in the new SI these units are linked to exact numerical values of the Planck constant, the elementary charge, the Boltzmann constant and the Avogadro constant, respectively. The new wording used expresses the definitions in a simple and unambiguous manner without the need for the distinction between base and derived units. The importance of relations among the fundamental constants to the definitions, and the importance of establishing a mise en pratique for the realization of each definition, are also discussed.

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Redefinition of the kilogram and the impact on its future dissemination

Cited by 46 publications

References 21 publications

The Avogadro constant: determining the number of atoms in a single-crystal ²⁸ Si sphere

The Avogadro constant: determining the number of atoms in a single-crystal ²⁸ Si sphere

Towards a new SI: a review of progress made since 2011

Adapting the International System of Units to the twenty-first century

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Redefinition of the kilogram and the impact on its future dissemination

Cited by 46 publications

References 21 publications

The Avogadro constant: determining the number of atoms in a single-crystal 28 Si sphere

The Avogadro constant: determining the number of atoms in a single-crystal 28 Si sphere

Towards a new SI: a review of progress made since 2011

Adapting the International System of Units to the twenty-first century

Contact Info

Product

Resources

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The Avogadro constant: determining the number of atoms in a single-crystal ²⁸ Si sphere

The Avogadro constant: determining the number of atoms in a single-crystal ²⁸ Si sphere