Réaumur

The Réaumur is a unit of temperature named after René Antoine Ferchault de Réaumur, who first proposed it in 1731. The freezing point of water is 0° Reaumur, the boiling point 80° Reaumur. Hence a degree Reaumur is 1.25 degrees Celsius or kelvin.

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°; and 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.

The Reaumur scale saw widespread use in Europe, particularly in France and Germany, but was eventually replaced by the Celsius scale. Today it is of historical significance.

Other temperature scales include Newton (~1700), Rømer (1701), Fahrenheit (1724), Delisle or de Lisle (1738), Celsius (1742), Rankine (1859), kelvin (1862) and Leyden (ca. 1894?). (Note that "kelvin" is lower-cased because it is an SI unit, even though it is named after a person).

Reaumur temperature conversion formulas

Conversion from	to	Formula
Réaumur	Fahrenheit	°F = °Ré × 2.25 + 32
Fahrenheit	Réaumur	°Ré = (°F - 32) / 2.25
Reaumur	Celsius	°C = °Ré × 1.25
Celsius	Réaumur	°Ré = °C × 0.8
Réaumur	Kelvin	K = °Ré × 1.25 + 273.15
Kelvin	Réaumur	°Ré = (K - 273.15) × 0.8
Réaumur	Rankine	°Ra = °Ré × 2.25 + 32 + 459.67
Rankine	Réaumur	°Ré = (°Ra - 32 - 459.67) / 2.25

External link

• Temperature Conversions: Celsius (Centigrade), Fahrenheit, Kelvin, Reaumur, and Rankine

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Réaumur is also the name of a commune in the Vendée département, in France.