Freeing the mole from the kilogram: How the redefinition of the kilogram shaped our definition of the Avogadro number

Epstein, Jessica

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https://hdl.handle.net/2142/128633 Copy

Description

Title

Freeing the mole from the kilogram: How the redefinition of the kilogram shaped our definition of the Avogadro number

Author(s)

Epstein, Jessica

Issue Date

2022-07-15

Keyword(s)

• Chemistry
• History
• Mole
• Kilogram

Abstract

An update to the scientific system of measurement went into effect on May 20, 2019, redefining the mole and the kilogram, along with the ampere and kelvin. These units follow the meter, candela and second to be defined by fundamental universal constants. The update to the kilogram is most symbolic, because it renders obsolete a metal cylinder kept in a vault near Paris that has defined the kilogram for 130 years and is part of a long history to search for a standardized system of measurement that would span across cultures and prove reliable and replaceable if destroyed by war, fire or other disaster. An update to the kilogram necessitates an update to the mole since historically the two have been intimately linked. Most people will never notice the change, but just below the surface, it represents a significant breakthrough in our relationship to base units of measurements and the Avogadro constant. This paper explores the origins of some widely used units, followed by an overview of standardization and the metric system, and finally the development of our current value for the mole and how it is tied to the most recent revisions to the International System of Units (SI).

Publisher

Division of the History of Chemistry

ISSN

1053-4385

Type of Resource

text

Genre of Resource

article

Language

eng

Permalink

https://hdl.handle.net/2142/128633

DOI

https://doi.org/10.70359/bhc2022v047p231

Copyright and License Information

Copyright 2022 Division of the History of Chemistry

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