Johann Josef Loschmidt

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Jan or Johann Josef Loschmidt (March 15 1821 - July 8 1895) who referred to himself mostly as Josef Loschmidt (omitting his first name), was a notable Austrian scientist with groundbreaking work in the fields of chemistry and physics (thermodynamics, optics, electrodynamics).

Born in Počerny near Karlsbad/Carlsbad, Bohemia (now the Czech Republic), he became professor for physical chemistry at the University of Vienna in 1868. His fields of research were thermodynamics, electrodynamics, optics and crystal forms.

In 1856 he determined the size of the molecules in air.

In his 1861 booklet, Chemische Studien, Loschmidt proposed two-dimensional representations for over 300 molecules in a style [remarkably similar] to that used by modern chemists. Among these were cyclic molecules such as benzene (C₆H₆, aka benzol) and related triazines. Although Loschmidt's work appeared four years before that of the much better known Kekulé, it is Kekulé who has traditionally been credited with the discovery of benzene's cyclic structure. This may be an instance of the Matthew effect.

Loschmidt was the first to determine, in 1865, the number of molecules of an ideal gas in 1 cm³, now known as the "Loschmidt number" L = 2.687 × 10¹⁹ cm^-3. This later became known as Avogadro's Number, although Avogadro actually never calculated the number of molecules as Loschmidt did, but determined that any gas under the same conditions had the same number of molecules in 1 Mole (Mol.) - that number being, as determined by Loschmidt's calculations, 6.023 × 10²³ molecules. This is why on rare occasions this "Avogadro number" may be referred to as the "Loschmidt number" in English (in German, though, "Loschmidt'sche Zahl" is the commonly used - and historically correct - name).

He retired from university in 1891 and died in 1895 in Vienna. His only child had died before him at the age of ten.

References

Peter M. Schuster: From Curiosity to Passion: Loschmidt's Route from Philosophy to Natural Science, in: W. Fleischhacker and T. Schönfeld (Editors): Pioneering Ideas for the Physical and Chemical Sciences, Proceedings of the Josef Loschmidt Symposium, held in Vienna, Austria, June 25-27, 1995; Plenum Press, 1997, New York. - ISBN 0-306-45684-2

John Buckingham: Chasing the Molecule; Sutton Publishing, 2004, Glaucestershire. - ISBN 0-7509-3345-3

External links

http://www.physicstoday.org/pt/vol-54/iss-3/p45.html
http://scienceweek.com/2004/rmps-15.htm
http://www.uh.edu/engines/epi1858.htm
http://www.loschmidt.cz/
http://www.ch.ic.ac.uk/rzepa/loschmidt/

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