Johann F. C. Hessel

Friedrich Hessel (* April 27, 1796 in Nuremberg, † June 3, 1872 in Marburg ) was a German crystallographer and high school teachers.

Life and work

Hessel was in 1825 professor of mineralogy in Marburg. He was also a member of the city council in Marburg. For his services he was on November 9, 1840 Honorary Citizen of the city of Marburg. 1830/31 he was rector of the University of Marburg.

As one of the first Hessel derived the 32 crystallographic point groups (crystal classes). His investigations it was based exclusively on the crystal morphology. He was aware of the symmetry laws that had been found by René -Just Haiiy and whom he greatly admired. It is noteworthy that at the time of Hessels studies, not all 32 point groups in the form of crystals and minerals were found. He headed the point groups therefore theoretically by a combination of symmetry operations from.

Hessel published his results in 1830 in the article crystal in Johann Samuel Traugott Gehler 's physical dictionary ( Volume 5, Part 2). This article was long unnoticed. It was not until a new edition of the article in 1897 reached more attention. A little earlier, were the 32 point groups carried Moritz Ludwig Frankenheim found ( 1826). His work, however, remained unnoticed for over 150 years. Later derivatives of the 32 point groups derived by Auguste Bravais (1849 ) and Axel Wilhelmowitsch Gadolin (1867 ).

In general, the arguments of Hessel are considered difficult to understand. That may have helped that his work has largely been overlooked.

Important works

• Crystal. In: HW Brandes ( ed.): Johann Samuel Traugott Gehler Physical dictionary. Vol V. II division. I to K, EB Schwieckert, Leipzig 1830, pp. 1023-1340 ( full text in the Google Book Search ).
• Krystallometrie, or Krystallonomie and crystallography, Ostwald's classic of Exact Sciences, Volume 88, 89, Leipzig 1897
• Overview of equal angular polyhedron, Marburg 1871