Daniel Gabriel Fahrenheit

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German physicist (1686–1736)

Possibly owing to a business failure, Fahrenheit emigrated to Amsterdam from his native Danzig (now Gdańsk in Poland) to become a glass blower and instrument maker. He specialized in the making of meteorological instruments, and proceeded to develop a reliable and accurate thermometer. Galileo had invented the thermometer in about 1600, using changes in air volume as an indicator. Since the volume of air also varied considerably with changes in atmospheric pressure liquids of various kinds were quickly substituted. Fahrenheit was the first to use mercury in 1714. He fixed his zero point by using the freezing point of a mixture of ice and salt as this gave him the lowest temperature he could reach. His other fixed point was taken from the temperature of the human body, which he put at 96°. Given these two fixed points the freezing and boiling points of water then work out at the familiar 32° and 212°. One advantage of the system is that, for most ordinary purposes, negative degrees are rarely needed.

Using his thermometer, Fahrenheit measured the boiling point of various liquids and found that each had a characteristic boiling point, which changed with changes in atmospheric pressure.

The German instrument maker Gabriel Daniel Fahrenheit (1686-1736) made the first reliable thermometers. The temperature scale he originated is named after him.

Born in Danzig on May 14, 1686, Gabriel Fahrenheit was the son of a well-to-do merchant. He lost both parents on the same day, Aug. 14, 1701, and was thereafter apprenticed to a shopkeeper in Amsterdam. After completing a term of 4 years there, he turned to physics and became an instrument maker and glassblower. Although he lived in Amsterdam most of his life, he traveled widely and spent considerable time in England, where he became a member of the Royal Society.

Fahrenheit completed his first two thermometers by 1714. They contained alcohol and agreed exactly in readings. The scale which was to bear Fahrenheit's name had not yet been calibrated, and many different scales were tried before he settled on one. He soon decided to replace the alcohol with mercury and completed a series of investigations based on the work of G. Amontons, in which he determined the boiling point of water and other liquids and studied the expansion properties of mercury. These experiments led to the discovery that the boiling point of water varied with changes in atmospheric pressure. Fahrenheit also discovered the phenomenon of supercooling of water, that is, cooling water to below its normal freezing point without converting it to ice.

Taking all of these factors into consideration, Fahrenheit was led to doubt the reliability of the freezing and boiling points of water and finally settled on a temperature scale ranging from 0 to 212. In 1724, announcing his method of making thermometers in the Philosophical Transactions of the Royal Society, he wrote concerning his scale, " … degree 48, which in my thermometers holds the middle place between the limit of the most intense cold obtainable artificially in a mixture of water, of ice, and of sal ammoniac or even of sea salt, and the limit of heat which is found in the blood of a healthy man." (It has been suggested that the 96-degree range was chosen simply for the convenience of that number when laying off the scale by halving spaces on the thermometer stem.) Thus, finding the temperatures of the human body and of his freezing mixture to be reliable parameters, he set 0 as the temperature of the mixture; 32 as the temperature of water and ice; and 212, a point selected by chance, as about the boiling point of water.

Fahrenheit's thermometers were highly esteemed. He used mercury successfully because of his technique for cleaning it, and he introduced the use of cylindrical bulbs instead of spherical ones. However, his detailed technique for making thermometers was not disclosed for some 18 years, since it was a trade secret. Among the other instruments which he devised were a constant-weight hydrometer of excellent design and a "thermobarometer" for estimating barometric pressure by determining the boiling point of water.

On Sept. 16, 1736, Fahrenheit died, unmarried, in the Netherlands, presumably in The Hague, where he was buried.

Further Reading

Henry Lipson, The Great Experiments in Physics (1968), includes a chapter on heat with reference to Fahrenheit. For background and additional material on Fahrenheit see Florian Cajori, A History of Physics (1899; rev. ed. 1929); Max von Laue, History of Physics (1947; trans. 1950); and Allen L. King, Thermophysics (1962).

Daniel Gabriel Fahrenheit
Born	24 May 1686 (in old British sources as 14 May Old Style) Danzig (Gdańsk) Polish–Lithuanian Commonwealth
Died	16 September 1736 (aged 50) The Hague, Netherlands
Fields	Physics, thermometry
Known for	Fahrenheit temperature scale, Fahrenheit hydrometer

Fahrenheit's birthplace at 95 Ogarna Street, Gdańsk, Poland.

Daniel Gabriel Fahrenheit^[1] (14 May 1686 – 16 September 1736) was a physicist and engineer who determined a temperature scale now named after him.

Contents 1 Biography 2 Fahrenheit scale 3 See also 4 References 5 Further reading 6 External links

Biography

Fahrenheit was born in 1686 in Gdańsk (German: Danzig), Royal Prussia, a province of the Polish-Lithuanian Commonwealth^[2], but lived most of his life in the Dutch Republic. The Fahrenheits were a Hanse merchant family who had lived in several Hanseatic cities. Fahrenheit's great-grandfather had lived in Rostock, and research suggests that the Fahrenheit family originated in Hildesheim.^[3] Daniel's grandfather moved from Kneiphof (Knipawa) (in Königsberg (Królewiec)) to Danzig and settled there as a merchant in 1650. His son, Daniel Fahrenheit (the father of the subject of this article), married Concordia (widowed name, Runge), daughter of the well-known Danzig business family of Schumann. Daniel Gabriel was the eldest of the five Fahrenheit children (two sons, three daughters) who survived childhood. His sister, Virgina Elisabeth Fahrenheit, married Benjamin Ephraim Krueger of a patrician family of Danzig.^[4]

At age 16, Daniel Gabriel Fahrenheit began training as a merchant in Amsterdam after his parents died on August 14 in 1701 from accidentally eating poisonous mushrooms. However, Fahrenheit's interest in natural science caused him to begin studies and experimentation in that field. From 1707, he traveled to Berlin, Halle, Leipzig, Dresden, Kopenhagen, and also to his hometown, where his brother still lived. During that time, Fahrenheit met or was in contact with Ole Rømer, Christian Wolff, and Gottfried Leibniz. In 1717, Fahrenheit settled in The Hague with the trade of glassblowing, making barometers, altimeters, and thermometers. From 1718 onwards, he lectured in chemistry in Amsterdam. He visited England in 1724 and became a member of the Royal Society.^[5] Fahrenheit died in The Hague and was buried there at the Kloosterkerk (Cloister Church).

Fahrenheit scale

The Celsius and Fahrenheit scales.

Main article: Fahrenheit

According to Fahrenheit's 1724 article^[6][7], he determined his scale by reference to three fixed points of temperature. The lowest temperature was achieved by preparing a frigorific mixture of ice, water, and ammonium chloride (a salt), and waiting for it to reach equilibrium. The thermometer then was placed into the mixture and the liquid in the thermometer allowed to descend to its lowest point. The thermometer's reading there was taken as 0 °F. The second reference point was selected as the reading of the thermometer when it was placed in still water when ice was just forming on the surface.^[8] This was assigned as 32 °F. The third calibration point, taken as 96 °F, was selected as the thermometer's reading when the instrument was placed under the arm or in the mouth.

Fahrenheit noted that mercury boils around 600 degrees on this temperature scale. Work by others showed that water boils about 180 degrees above its freezing point. The Fahrenheit scale later was redefined to make the freezing-to-boiling interval exactly 180 degrees^[6], a convenient value as 180 is a highly composite number, meaning that it is evenly divisible into many fractions. It is because of the scale's redefinition that normal body temperature today is taken as 98.6 degrees, whereas it was 96 degrees on Fahrenheit's original scale.^[9]

Until the switch to the Celsius scale, the Fahrenheit one was widely used in Europe. It is still used for everyday temperature measurements by the general population in the United States and Belize and, less so, in the UK.^[10]

See also

• Fahrenheit hydrometer

References

1. ^ He signed as D. G. Fahrenheit in a 1736 letter
2. ^ Gottfried Stolterfoth: Kurzgefasste Geschichte und Staats-Verfassung von Polnisch-Preussen inalten und neueren Zeiten, 1764 S. 581
3. ^ Kant, Horst (1984). G. D. Fahrenheit / R. -A. F. de Réaumur / A. Celsius. B. G. Teubner. http://books.google.com/books?id=XYKtGQAACAAJ. Retrieved 2008-06-14. 
4. ^ See the Fahrenheit and Krueger genealogies.
5. ^ The Royal Society Archive catalogue
6. ^ ^{a b} "Fahrenheit temperature scale". Sizes, Inc. 2006-12-10. http://www.sizes.com/units/temperature_Fahrenheit.htm. Retrieved 2008-05-09. 
7. ^ Fahrenheit describes, in Latin, these numerical choices in the following paper: Fahrenheit, D. G. (1724). "Experimenta et Observationes de Congelatione aquae in vacuo factae". Philosophical Transactions (London) 33: 78. doi:10.1098/rstl.1724.0016. 
8. ^ Heath, Jonathan. "Why does the Fahrenheit scale use 32 degrees as a freezing point?". PhysLink. http://www.physlink.com/Education/AskExperts/ae64.cfm?CFID=21412834&CFTOKEN=55577927. Retrieved 2008-05-09. 
9. ^ Elert, Glenn (2002), "Temperature of a Healthy Human (Body Temperature)", Scandinavian Journal of Caring Sciences 16: 122, doi:10.1046/j.1471-6712.2002.00069.x, http://hypertextbook.com/facts/LenaWong.shtml, retrieved 04-12-2008 
10. ^ For an early attempt to replace the Fahrenheit scale in the United States, see Johnson, Albert (1916). Abolish the Fahrenheit Thermometer. Washington, DC. http://books.google.com/books?id=Bv5gc38ezBAC&printsec=frontcover&dq=Abolish+the+Fahrenheit+Thermometer. 

Further reading

Memorial plaque at Fahrenheit's burial site in The Hague.

• Bolton, Henry Carrington (1900). Evolution of the Thermometer, 1592-1743. Easton, Pennsylvania: The Chemical Publishing Company. pp. 66 – 79. http://books.google.com/books?id=7A9JAAAAIAAJ&printsec=frontcover&dq=evolution+thermometer#PPA1,M2. 
• Fahrenheit, D. G. (1724). "Experimenta circa gradum caloris liquorum nonnullorum ebullientium instituta (Experiments done on the degree of heat of a few boiling liquids)". Philosophical Transactions (London) 33: 1. http://web.lemoyne.edu/~giunta/fahrenheit.html. 
• Fahrenheit, D. G. (1724). "Experimenta et Observationes de Congelatione aquae in vacuo factae". Philosophical Transactions (London) 33: 78. doi:10.1098/rstl.1724.0016.  (Latin)
• Klemm, Friedrich: Daniel Gabriel Fahrenheit. In: Neue Deutsche Biographie (NDB). Band 4, Duncker & Humblot, Berlin 1959, S. 746 f. (German)
• Kops, J (1976), "Who was G.D. Fahrenheit?", Zdravotnická pracovnice 26 (2): 118–9, 1976 Feb, PMID 775856  (Czech)
• Lommel: Fahrenheit, Gabriel Daniel. In: Allgemeine Deutsche Biographie (ADB). Band 6, Duncker & Humblot, Leipzig 1877, S. 535. (German)
• Friedrich Klemm: Daniel Gabriel Fahrenheit. In: Neue Deutsche Biographie (NDB). Band 4, Duncker & Humblot, Berlin 1959, S. 746 f. (German)
• Middleton, W. E. Knowles (1966). A History of the Thermometer and its Use in Meteorology. Baltimore, Maryland: Johns Hopkins Press. 
• Sorokina, T S (1986), "Creators of medical thermometry (on the 300th anniversary of the birth of Gabriel Daniel Fahrenheit--24 May 1686 and on the 350th anniversary of the death of Santorio Santorio--22 February 1636)", Klinicheskaia meditsina 64 (10): 147–51, 1986 Oct, PMID 3543477  (Russian)
• Van Der Star, P., ed. (1984), Fahrenheit's Letters to Leibniz and Boerhaave, Editions Rodopi 

External links

• Daniel Gabriel Fahrenheit in the German National Library catalogue (German)
• Letter from Daniel Gabriel Fahrenheit (scan) to Carl Linnaeus, 7 May 1736 n.s., [1] (German)
• Senese, Fred (2005). "Why isn't 0°F the lowest possible temperature for a salt/ice/water mixture?". http://antoine.frostburg.edu/chem/senese/101/solutions/faq/zero-fahrenheit.shtml. 

Persondata
NAME	Fahrenheit, Daniel Gabriel
ALTERNATIVE NAMES
SHORT DESCRIPTION	Physicist
DATE OF BIRTH	24 May 1686
PLACE OF BIRTH	Gdansk
DATE OF DEATH	16 September 1736
PLACE OF DEATH	The Hague, Netherlands

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