The Réaumur scale also known as the "octogesimal division", is a temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 scale in which the freezing

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 and boiling point

Boiling point

The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

s of water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 are set to 0 and 80 degrees respectively. The scale is named after René Antoine Ferchault de Réaumur

René Antoine Ferchault de Réaumur

René Antoine Ferchault de Réaumur was a French scientist who contributed to many different fields, especially the study of insects.-Life:Réaumur was born in a prominent La Rochelle family and educated in Paris...

, who first proposed something similar in 1730.

Réaumur’s thermometer

Thermometer

Developed during the 16th and 17th centuries, a thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor Developed during the 16th and 17th centuries, a thermometer (from the...

 contained diluted alcohol and 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. He suggested that the quality of alcohol

Alcohol

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 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 on the grounds that it expanded 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. In 1772 Jean-André Deluc

Jean-André Deluc

Jean-André Deluc or de Luc was a Swiss geologist and meteorologist.-Life:He was born at Geneva, descended from a family which had emigrated from Lucca and settled at Geneva in the 15th century...

 studied the several substances then used in thermometers in the light of new theories of heat and came to the conclusion that mercurial

Mercury (element)

Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

 thermometers were the best for practical use; for example, if two equal amounts of water at x and y degrees were mixed, the temperature of the result was then the average of x and y degrees, and this relationship only held reliably when mercury was used. From the late 18th century mercury was used almost without exception. These thermometers, the stems of which are graduated into eighty equal parts between the freezing and boiling points of water, are not Réaumur's original thermometers in anything but name.

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

Leo Tolstoy

Lev Nikolayevich Tolstoy was a Russian writer who primarily wrote novels and short stories. Later in life, he also wrote plays and essays. His two most famous works, the novels War and Peace and Anna Karenina, are acknowledged as two of the greatest novels of all time and a pinnacle of realist...

, and Nabokov

Vladimir Nabokov

Vladimir Vladimirovich Nabokov was a multilingual Russian novelist and short story writer. Nabokov wrote his first nine novels in Russian, then rose to international prominence as a master English prose stylist...

. By the 1790s, France chose the Celsius

Celsius

Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

 scale for the metric system

Metric system

The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

 over the Réaumur measurements. Its only modern use is in the measuring of milk temperature in cheese production. It is used in some Italian dairies making Parmigiano-Reggiano

Parmigiano Reggiano

Parmigiano-Reggiano , also known in English as Parmesan , is a hard granular cheese, cooked but not pressed, named after the producing areas near Parma, Reggio Emilia, Modena, and Bologna , and Mantova , Italy...

 and Grana Padano cheeses and in Swiss Alp cheeses.