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 of air, and in 1861 he proposed representations of the structure of benzene (C6H6, aka benzol) and related cyclic triazines much like the modern ones, and before the much more well known "discovery" by Kekulé.
He also proposed a structure for Ozone and many other molecules, and introduced the nowadays common depiction of chemical structures.
Loschmidt also 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 to be the Avagadro constant, who 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