Réaumur

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This article is about the temperature scale. Réaumur is also the name of a commune in the Vendée département, in France; see Réaumur.

The degree 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 degrees Réaumur, the boiling point 80 degrees Réaumur. Hence a Reaumur degree is 1.25 Celsius degrees or kelvins. The Réaumur temperature scale is also known as the octogesimal division (division octogesimale).

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. Chances are that he choose the octogesimal division because the number 80 could be halved 4 times and still be an integer (40, 20, 10, 5); the number 100, for instance, could only suffer this process 2 times (50, 25).

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

Degree Réaumur
Kelvin [K] = [°Ré] · 5/4 + 273.15 [°Ré] = ([K] − 273.15) · 4/5
Celsius [°C] = [°Ré] · 5/4 [°Ré] = [°C] · 4/5
Fahrenheit [°F] = [°Ré] · 9/4 + 32 [°Ré] = ([°F] − 32) · 4/9
Rankine [°Ra] = [°Ré] · 9/4 + 491.67 [°Ré] = ([°Ra] − 491.67) · 4/9
Newton [°N] = [°Ré] · 33/80 [°Ré] = [°N] · 80/33
Rømer [°Rø] = [°Ré] · 21/32 + 7.5 [°Ré] = ([°Rø] − 7.5) · 32/21
Delisle [°De] = (80 − [°Ré]) · 15/8 [°Ré] = 80 − [°De] · 8/15

Degree Réaumur
Kelvin	[K] = [°Ré] · 5/4 + 273.15	[°Ré] = ([K] − 273.15) · 4/5
Celsius	[°C] = [°Ré] · 5/4	[°Ré] = [°C] · 4/5
Fahrenheit	[°F] = [°Ré] · 9/4 + 32	[°Ré] = ([°F] − 32) · 4/9
Rankine	[°Ra] = [°Ré] · 9/4 + 491.67	[°Ré] = ([°Ra] − 491.67) · 4/9
Newton	[°N] = [°Ré] · 33/80	[°Ré] = [°N] · 80/33
Rømer	[°Rø] = [°Ré] · 21/32 + 7.5	[°Ré] = ([°Rø] − 7.5) · 32/21
Delisle	[°De] = (80 − [°Ré]) · 15/8	[°Ré] = 80 − [°De] · 8/15

Comparison of temperature scales

Comparison of temperature scales
Comment	Kelvin	Celsius	Fahrenheit	Rankine	Delisle	Newton	Réaumur	Rømer
Absolute zero	0	−273.15	−459.67	0	559.725	−90.14	−218.52	−135.90
Coldest recorded surface temperature on Earth (Vostok, Antarctica - July 21, 1983)	184	−89	−128.2	331.47	283.5	−29.37	−71.2	−39.225
Fahrenheit's ice/salt mixture	255.37	−17.78	0	459.67	176.67	−5.87	−14.22	−1.83
standard pressure)	273.15	0	32	491.67	150	0	0	7.5
Average surface temperature on Earth	288	15	59	518.67	127.5	4.95	12	15.375
Average human body temperature ¹	309.95	36.8	98.24	557.91	94.8	12.144	29.44	26.82
(Al 'Aziziyah>Al 'Aziziyah, Libya - September 13, 1922)	331	58	136.4	596.07	63	19.14	46.4	37.95
standard pressure)	373.15	100	212	671.67	0	33	80	60
Titanium melts	1941	1668	3034	3494	−2352	550	1334	883
surface of the Sun	5800	5526	9980	10440	−8140	1823	4421	2909

¹ Normal human body temperature is 36.8 °C ±0.7 °C, or 98.2 °F ±1.3 °F. The commonly given value 98.6 °F is simply the exact conversion of the nineteenth-century German standard of 37 °C. Since it does not list an acceptable range, it could therefore be said to have excess (invalid) precision. Here's a [list] of various measurements.
Some numbers in this table have been rounded off.

External link

[Conversion calculator for units of temperature]

Temperature scale (measurement)>scales
Celsius		Fahrenheit		Kelvin
Delisle	Leyden	Newton	Rankine	Réaumur	Rømer
Conversion formulas

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