Degree Réaumur (°Ré)
A scale proposed in 1730 by René Réaumur in which water freezes at 0° and boils at 80°. Used across Europe until the 19th century and in Russia until the early 20th.
0 degrees Réaumur = 273.15 kelvins (exactly).
About the degree Réaumur
René Antoine Ferchault de Réaumur proposed a thermometer scale in 1730, and it still carries his name. He placed zero at the melting point of water and divided the tube so that each degree was one thousandth of the volume of the bulb and stem below the zero mark. His liquid was diluted alcohol, mixed so that it began to boil after expanding by 8 percent, which gave the familiar 80 degrees for boiling water. The method is also called the octogesimal division.
Instrument makers often filled their tubes with other liquids while still marking 80 for boiling water, which caused real confusion until mercury became nearly universal from the late 18th century, following Jean-André Deluc's tests in 1772. The scale was common in France, Germany and Russia, and appears in the writing of Jefferson, Dostoevsky and Tolstoy. France moved to the centigrade scale in the 1790s, but Réaumur readings lingered in parts of Europe until at least the mid-19th century and in parts of Russia into the early 20th.
Because the interval from freezing to boiling is 80 degrees instead of 100, one degree Réaumur equals 1.25 degrees Celsius, so Celsius is the Réaumur reading times 5/4. Kelvin is that figure plus 273.15. Today the scale survives mainly among some Italian and Swiss cheesemakers, who use it for milk temperatures.
Sources: Wikipedia: Réaumur scale
Degree Réaumur conversion chart
100 degrees Réaumur expressed in every other temperature unit:
| Unit | 100 degrees Réaumur |
|---|---|
| Kelvin | 398.15 |
| Celsius | 125 |
| Fahrenheit | 257 |
| Rankine | 716.67 |
| Delisle | -37.5 |
| Newton | 41.25 |
| Rømer | 73.125 |
More French (Ancien Régime) units
- degree Delisle (temperature)
- ligne (length)
- pouce (length)
- pied du roi (length)
- toise (length)
- lieue (Paris league) (length)
- arpent (North American) (area)
- poncelet (power)
- pièze (pressure)
- sthène (force)
All French (Ancien Régime) units
Browse all temperature units.