Abstract
The kilogram is the unit of mass and was defined in 1889 by the international prototype of the kilogram. The mole is the unit of amount of substance and was defined in 1960 by the number of atoms in 0.012 kg of 12C. These definitions were revised in May 2019. The new definitions of the kilogram and the mole are based on the Planck constant h and the Avogadro constant NA, respectively. The values of h and NA used in the new definitions were determined by summarizing measurement results of the two physical constants by several national metrology institutes around the world. In this review, the history of the two units and measurement technologies used to derive the new definitions are described. The effect of the revision on the development of new measurement technologies is also introduced.
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24 February 2023
A Correction to this paper has been published: https://doi.org/10.1007/s44211-023-00294-9
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Acknowledgments
The research work to redefine the kilogram and the mole at NMIJ was partly supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers 24360037, 16H03901, and 20H02630.
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The original online version of this article was revised: opting for Open Choice the copyright of the article changed to ©The Author(s) 2020.
Naoki Kuramotois the Group Leader of the Mass Standards Group of the National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). He received his Ph.D. degree in chemistry from Saga University in 1998. Since 1999, he has been working at NMIJ/ AIST, where he developed an optical interferometer to measure the volume of28Si-enriched spheres for the redefinition of the kilogram. The lanck constant determined by Kuramoto et al. in 201 had a significant impact on the determination of the Planck constant in the new definition of the kilogram. His research interests include development of new mass measurement principles based on the Planck constant. He also serves as the Coordinator of the International Avogadro Coordination project.
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Kuramoto, N. New Definitions of the Kilogram and the Mole: Paradigm Shift to the Definitions Based on Physical Constants. ANAL. SCI. 37, 177–188 (2021). https://doi.org/10.2116/analsci.20SAR08
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DOI: https://doi.org/10.2116/analsci.20SAR08