Johann Gottlob Leidenfrost

Johann Gottlob Leidenfrost (November 27, 1715 - December 2, 1794) was a German doctor and theologian who first described the scientific phenomenon eponymously named the Leidenfrost effect.

Personal life and career

Johann Gottlob Leidenfrost was born on November 27, 1715 in the town of Ortenberg in the County of Stollberg, Germany. His father, Johann Heinrich Leidenfrost, was a well-known minister. Little is know of Leidenfrost's life prior to the start of his academic career.

Leidenfrost first attended Justus Liebig University where he followed in his father's footsteps by studying theology. He soon switched his academic concentration to medicine, following that career path in his subsequent attendance at the University of Leipzig and the University of Halle in Westphalia.

In 1741 he was awarded a doctorate in medicine largely based on a well-received treatise on the study of the movement of the human body, entitled "On the Harmonious Relationship of Movements in the Human Body." After the conclusion of his academic studies, Leidenfrost spent some years traveling and took a post as a field physician in the first Silesian War.

In 1743 Leidenfrost was offered and accepted a professorship at University of Duisburg. In 1745 he married a local Duisburg woman, Anna Cornelia Kalckhoff. Johann and Anna had seven children together, including Johanna Ulricke (1752-1819), who was later the wife of the noted German theologian, Christian Krafft. In addition to teaching medicine, physics and chemistry at the University of Duisburg, Leidenfrost also functioned as the university's rector, all the while maintaining a private medical practice.

In 1756, Leidenfrost became a member of the "Berlin Academy of Sciences". During his lifetime, Leidenfrost published more than seventy manuscripts, including "De Aquae Communis Nonnullis Qualitatibus Tractatus" (1756) ("A Tract About Some Qualities of Common Water") in which the Leidenfrost effect was first described (although the phenomenon had been previously observed by Herman Boerhaave in 1732). Leidenfrost died on December 2, 1794 in Duisburg, exactly two hundred years to the day after Gerardus Mercator.

The Leidenfrost Effect

The effect Leidenfrost described is a phenomenon in which a liquid, in near contact with a mass significantly hotter than its boiling point, produces an insulating vapor layer which keeps that liquid from boiling rapidly. This is most commonly seen when cooking; one sprinkles drops of water in a skillet to gauge its temperature—if the skillet's temperature is at or above the "Leidenfrost point", the water skitters across the metal and takes "longer" to evaporate than it would in a skillet that is hot, but at a temperature below the "Leidenfrost point." It has also been used in some dangerous demonstrations, such as dipping a "wet" finger in molten lead and blowing out a mouthful of liquid nitrogen, both enacted without injury to the demonstrator.

References

*everything2.com (2006). [http://www.everything2.com/index.pl?node_id=850481 "Leidenfrost effect"] . Retrieved March 10, 2006.
*Volcaniclightning.tripod.com/leidenfr.htm (2006) [http://volcaniclightning.tripod.com/leidenfr.htm "Leidenfrost`s Phenomenon J.G.Leidenfrost"] . Retrieved March 10, 2006.
* [http://de.wikipedia.org/wiki/Johann_Gottlob_Leidenfrost Johann Gottlob Leidenfrost] from the German-language Wikipedia. Retrieved March 10, 2006 and containing the internal references:
*Born, Gernot and Kopatschek, Frank, "Die alte Universität Duisburg 1655 - 1818"; Duisburg 1992.
*Ring, Walter "Geschichte der Universität Duisburg. Mit einem Lageplan"; Duisburg 1920.
*von Roden, Günter, "Geschichte der Stadt Duisburg"; 2 Bde., 2. verbess. Aufl., Duisburg 1979.

External links

*De icon [http://www.leidenfrost-ahnen.de Leidenfrost - Ahnen (genealogy)] .
* [http://news.bbc.co.uk/1/hi/sci/tech/4955398.stm Scientists make water run uphill]