Réaumur scale
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| from Réaumur | to Réaumur | |
|---|---|---|
| Celsius | [°C] = [°Ré] × 5⁄4 | [°Ré] = [°C] × 4⁄5 |
| Fahrenheit | [°F] = [°Ré] × 9⁄4 + 32 | [°Ré] = ([°F] − 32) × 4⁄9 |
| Kelvin | [K] = [°Ré] × 5⁄4 + 273.15 | [°Ré] = ([K] − 273.15) × 4⁄5 |
| Rankine | [°R] = [°Ré] × 9⁄4 + 491.67 | [°Ré] = ([°R] − 491.67) × 4⁄9 |
| For temperature intervals rather than specific temperatures, 1 °Ré = 1.25 °C = 2.25 °F Comparisons among various temperature scales |
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The Réaumur scale (°Ré, °Re, °R), also known as the "octogesimal division",[1] is a temperature scale in which the freezing and boiling points of water are set to 0 and 80 degrees respectively. The scale is named after René Antoine Ferchault de Réaumur, who first proposed it in 1730.[2]
Réaumur’s thermometer was constructed on the principle of taking the freezing point of water as 0°, and graduating the tube into degrees each of which was one-thousandth of the volume contained by the bulb and tube up to the zero mark. It was the dilatability of the particular quality of alcohol employed which made the boiling point of water 80°.[citation needed] Mercurial thermometers, the stems of which are graduated into eighty equal parts between the freezing and boiling points of water, are not Réaumur thermometers in anything but name. Réaumur may have chosen the octogesimal division because the number 80 could be halved 4 times and still be an integer (40, 20, 10, 5);[citation needed] the number 100, for instance, could only suffer this process twice (50, 25). Alternatively, the number 80 is also not unnatural in the French language in which numbers up to 16 (80 divided by 5) have individual names (in English, only eleven and twelve have names that are not immediately metric) and the number 80 is referred to as quatre-vingts (4 times 20).
[edit] Use
The Réaumur scale saw widespread use in Europe, particularly in France and Germany as well as Russia, as referenced in works of Dostoyevsky, Tolstoy, and Nabokov.[3][4][5] But by the 1790s, France chose the Celsius scale for the metric system over the Réaumur measurements.[2] Its only modern use is in the measuring of milk temperature in cheese production. It is used in some Italian dairies making Parmigiano-Reggiano and Grana Padano cheeses and in Swiss Alp cheeses.[6]
[edit] References
- ^ Division octogesimale in French.
- ^ a b Simons, Paul (17 October 2007). "How Reaumur fell off the temperature scale". The Times. http://www.timesonline.co.uk/tol/news/weather/article2673568.ece. Retrieved 2008-03-10.
- ^ Fyodor Dostoyevsky, Crime and Punishment, p. 268 Vintage Books
- ^ Leo Tolstoy, Anna Karenina, p. 685, Wordsworth Editions Limited
- ^ Vladimir Nabokov, The Real Life of Sebastian Knight, p. 1. Penguin Books.
- ^ Reaumur thermometer for Parmigiano-Reggiano cheese)
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