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The Réaumur scale (; °Ré, °Re, °r), also known as the "octogesimal division", is a
temperature
Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
scale for which the
melting
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...
and
boiling point
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
The boiling point of a liquid varies depending upon the surrounding envi ...
s of
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
are defined as 0 and 80 degrees respectively. The scale is named for
René Antoine Ferchault de Réaumur, who first proposed a similar scale in 1730.
Change in scale
Réaumur's
thermometer
A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
contained diluted
alcohol
Alcohol may refer to:
Common uses
* Alcohol (chemistry), a class of compounds
* Ethanol, one of several alcohols, commonly known as alcohol in everyday life
** Alcohol (drug), intoxicant found in alcoholic beverages
** Alcoholic beverage, an alco ...
(ethanol) and was constructed on the principle of using 0° for the melting temperature of water, 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. He suggested that the concentration of alcohol employed be such that it began boiling at 80 °Ré – that is, when it had expanded in volume by 8%. He chose alcohol instead of mercury because it expands more visibly, but this posed problems: his original thermometers were very bulky, and the low boiling point of alcohol made them unsuitable for many applications. Instrument-makers generally chose different liquids, and then used 80 °Ré to signify the boiling point of water, causing much confusion.
During 1772
Jean-André Deluc
Jean-André Deluc or de Luc (8 February 1727 – 7 November 1817) was a geologist, natural philosopher and meteorologist from the Republic of Geneva. He also devised measuring instruments.
Biography
Jean-André Deluc was born in Geneva. His ...
studied the several substances then used in thermometers and concluded that
mercury thermometers were the best for practical use, on the grounds that among these substances its volume varies the most linearly with the method of mixtures. In detail, if two portions of water of equal masses A, B were mixed, and let the resulting water be C, and if we immerse a thermometer in A, B, C, we obtain lengths
. Deluc expected that
, and similarly for other ratios of mixtures. He found that thermometers made using mercury allowed the closest fit to his expectation of linearity.
From the late 18th century mercury was used almost without exception.
Use
The Réaumur scale was used widely in Europe, particularly in France, Germany and Russia, and was referenced in the works of
Thomas Jefferson
Thomas Jefferson (, 1743July 4, 1826) was an American Founding Fathers of the United States, Founding Father and the third president of the United States from 1801 to 1809. He was the primary author of the United States Declaration of Indepe ...
,
Thomas Mann
Paul Thomas Mann ( , ; ; 6 June 1875 – 12 August 1955) was a German novelist, short story writer, social critic, philanthropist, essayist, and the 1929 Nobel Prize in Literature laureate. His highly symbolic and ironic epic novels and novell ...
,
Fyodor Dostoevsky
Fyodor Mikhailovich Dostoevsky. () was a Russian novelist, short story writer, essayist and journalist. He is regarded as one of the greatest novelists in both Russian and world literature, and many of his works are considered highly influent ...
,
Gustave Flaubert
Gustave Flaubert ( , ; ; 12 December 1821 – 8 May 1880) was a French novelist. He has been considered the leading exponent of literary realism in his country and abroad. According to the literary theorist Kornelije Kvas, "in Flaubert, realis ...
,
James Joyce
James Augustine Aloysius Joyce (born James Augusta Joyce; 2 February 1882 – 13 January 1941) was an Irish novelist, poet, and literary critic. He contributed to the modernist avant-garde movement and is regarded as one of the most influentia ...
,
Leo Tolstoy
Count Lev Nikolayevich Tolstoy Tolstoy pronounced his first name as , which corresponds to the romanization ''Lyov''. () (; ,Throughout Tolstoy's whole life, his name was written as using Reforms of Russian orthography#The post-revolution re ...
, and
Vladimir Nabokov
Vladimir Vladimirovich Nabokov ( ; 2 July 1977), also known by the pen name Vladimir Sirin (), was a Russian and American novelist, poet, translator, and entomologist. Born in Imperial Russia in 1899, Nabokov wrote his first nine novels in Rus ...
. For example, in Query VII of ''
Notes on the State of Virginia'', Jefferson converts readings from the Fahrenheit thermometer at Williamsburg to the Réaumur scale. At the beginning of Book X of ''
The Brothers Karamazov'', the narrator says, "We had eleven degrees of frost", i.e. −11 °Ré, equivalent to or . By the 1790s, France had chosen the
Celsius
The degree Celsius is the unit of temperature on the Celsius temperature scale "Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the melting point of water and 100 ° for the boiling point ...
scale as part of the
metric system
The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...
, rather than the Réaumur measurement,
but the Réaumur scale continued to be used in some parts of Europe until at least the mid-19th century, and in parts of Russia until the early 20th. Its main modern uses are in some Italian and Swiss factories for measuring milk temperature during cheese production, and in the Netherlands for measuring temperature when cooking sugar syrup for desserts and sweets.
Uses outside of Europe include a Mexican colonel in
Santa Anna's army in San Antonio, Texas in 1836 recording the night's temperature as and 1 °Ré.
Conversion between different temperature units
313.15 K = 40 °C = 104 °F = 563.67 °Ra = 28.5 °Ro = 13.2 °N = 90 °D = 32 ºRé
See also
*
Outline of metrology and measurement
The following is a topical outline of the English language Wikipedia articles on the topic of metrology and measurement. Metrology is the science of measurement and its application.
Main articles
* Metrology
* Measurement
Metrology overviews
...
Notes and references
{{DEFAULTSORT:Reaumur Scale
Obsolete units of measurement
Scales of temperature
Science and technology in France
Scales in meteorology