Editing Volume (section)

=== Metrication and redefinitions ===
{{Further|History of the metric system}}

On 7 April 1795, the metric system was formally defined in French law using six units. Three of these are related to volume: the ''[[stère]]''&nbsp;(1&nbsp;m<sup>3</sup>) for volume of firewood; the ''[[litre]]''&nbsp;(1&nbsp;dm<sup>3</sup>) for volumes of liquid; and the ''[[gram]]me'', for mass—defined as the mass of one cubic centimetre of water at the temperature of melting ice.<ref>
{{cite thesis
 | last = Cox | first = Edward Franklin
 | id = {{ProQuest|301905667}}
 | pages = 99–100
 | publisher = Indiana University
 | title = A History of the Metric System of Weights and Measures, with Emphasis on Campaigns for its Adoption in Great Britain, and in The United States Prior to 1914
 | type = PhD thesis
 | year = 1958
}}</ref> Thirty years later in 1824, the [[imperial gallon]] was defined to be the volume occupied by ten [[Pound (mass)|pounds]] of water at {{Cvt|62|F|C|order=flip}}.<ref name="Treese-2018" />{{Rp|page=394}} This definition was further refined until the United Kingdom's [[Weights and Measures Act 1985]], which makes 1 imperial gallon precisely equal to 4.54609&nbsp;litres with no use of water.<ref>{{Cite book |last=Cook |first=James L. |url= |title=Conversion Factors |date=1991 |publisher=[[Oxford University Press]] |isbn=0-19-856349-3 |location=Oxford [England] |pages=xvi |oclc=22861139}}</ref>

The 1960 redefinition of the metre from the [[International Prototype Metre]] to the orange-red [[Spectral line|emission line]] of [[krypton-86]] atoms unbounded the metre, cubic metre, and litre from physical objects. This also make the metre and metre-derived units of volume resilient to changes to the International Prototype Metre.<ref>{{cite book |last=Marion |first=Jerry B. |title=Physics For Science and Engineering |publisher=CBS College Publishing |year=1982 |isbn=978-4-8337-0098-6 |page=3}}</ref> The definition of the metre was redefined again in 1983 to use the [[speed of light]] and [[second]] (which is derived from the [[caesium standard]]) and [[2019 revision of the SI|reworded for clarity in 2019]].<ref>{{Cite web |date=20 May 2019 |title=''Mise en pratique'' for the definition of the metre in the SI |url=https://www.bipm.org/documents/20126/41489670/SI-App2-metre.pdf |website=[[International Bureau of Weights and Measures]] |publisher=Consultative Committee for Length |pages=1 |access-date=13 August 2022 |archive-date=13 August 2022 |archive-url=https://web.archive.org/web/20220813164032/https://www.bipm.org/documents/20126/41489670/SI-App2-metre.pdf |url-status=live }}</ref>