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Daniel Gabriel Fahrenheit

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Daniel Gabriel Fahrenheit, also called Gabriel Fahrenheit (May 24, 1686 - September 16, 1736), was a physicist and an engineer, who most of his life worked in Netherlands and for whom the Fahrenheit scale of temperature is named.

Fahrenheit was born in Gdansk, Poland. He was the son of businessman Daniel Fahrenheit and Concordia Fahrenheit (widowed name Runge), who was the daughter of the well-known Gdansk business family Schumann. Of the five Fahrenheit children who survived childhood (2 sons, 3 daughters), Daniel was the oldest. The Fahrenheits came to Gdansk in 1650 when Daniel's grandfather Reinhold Fahrenheit vom Kneiphof of Königsberg settled there as a businessman. Research suggests that the Fahrenheit family originated in Hildesheim, although they lived in Rostock before moving to Königsberg.[1]

Upon the early death of his parents he had to take up business training. However, his interest in natural sciences caused him to take up studies and experimentation in that field. Fahrenheit's studies brought him to Amsterdam, where he gave lectures in chemistry. In 1724 he became a member of the Royal Society.

He developed precise thermometers. The Fahrenheit scale was widely used in Europe until a switch to the centigrade or Celsius scale. It is still used by the general population for everyday temperature measurement in the United States.

When he first made his thermometers, he used alcohol instead of mercury. Later he used mercury, which gave better results.

Wikipedia: Mercury-in-glass thermometer

A mercury-in-glass thermometer is a thermometer consisting of mercury, in a glass tube. The thermometer can be used to determine temperature, this is done measured by examining how much of the tube's volume is filled by the mercury.

The thermometer was used by the originators of the Fahrenheit and Celsius temperature scales.

Anders Celsius devised the Celsius scale, which was described in his publication The Origin of the Celsius Temperature Scale in 1742.

Celsius used two fixed points in his scale: the temperature of melting ice and the temperature of boiling water. This wasn't a new idea, since Isaac Newton was already working on something similar. The distinction of Celsius was to use the melting temperature and not the freezing temperature. The experiments for reaching a good calibration of his thermometer lasted for 2 winters. By performing the same experiment over and over again, he discovered that ice always melted at the same temperature. He found a similar fixed point in the temperature of boiling water vapour. At the moment that he removed the thermometer from the vapour, the mercury level climbed slightly. This was related to the rapid cooling (and contraction) of the glass.

The air pressure influences the boiling point of water. Celsius claimed that the level of the mercury in boiling water is proportional to the height of the barometer.

When Celsius decided to use his own temperature scale, he chose to set the boiling point of pure water at 0º C and the freezing point at 100º C. Later it was decided by a great Swedish instrument maker that it was better the other way around.

Finally, Celsius proposed a method of calibrating a thermometer. This follows the following three steps and is the same everywhere in the world, a method which can also be used to construct a thermometer: 1. Place the cylinder of the thermometer in melting pure water and mark the point where the fluid in the thermometer stabilises. This point is the freeze/thaw point of water. 2. In the same manner mark the point where the fluid stabilises when the thermometer is placed in boiling water vapour. 3. Divide the length between the two marks into 100 equal pieces.

Timeline of temperature and pressure measurement technology

  • 1592 - Galileo Galilei builds a crude thermometer using the contraction of air to draw water up a tube
  • 1612 - Santorre Santorio puts thermometer to medical use
  • 1643 - Evangelista Torricelli invents the mercury barometer
  • 1714 - Daniel Gabriel Fahrenheit invents the mercury in glass thermometer
  • 1821 - T.J. Seebeck invents the thermocouple
  • 1864 - Henri Becquerel suggests an optical pyrometer
  • 1885 - Calender-Van Duesen invented the platinum resistance temperature device
  • 1892 - Henri-Louis Le Châtelier builds the first optical pyrometer

References

G.D.Fahrenheit / R.-A.F.de Réaumur / A. Celsius by Horst Kant, 1984.