August Wilhelm von Hofmann
|August Wilhelm von Hofmann|
August Wilhelm von Hofmann
8 April 1818|
Giessen, Grand Duchy of Hesse
|Died||5 May 1892
Berlin, Province of Brandenburg
|Institutions||University of Bonn, Royal College of Chemistry, Berlin University|
|Alma mater||University of Göttingen|
|Doctoral advisor||Justus von Liebig|
|Doctoral students||Richard Abegg, Adolf Pinner, Fritz Haber, Karl Friedrich von Auwers, Rudolf Hugo Nietzki, Ferdinand Tiemann, Eugen Bamberger|
|Known for||Hofmann rearrangement
|Influenced||William Henry Perkin|
Hofmann was born at Giessen, Grand Duchy of Hesse. Not intending originally to devote himself to physical science, he first took up the study of law and philology at Göttingen. But he then turned to chemistry, and studied under Justus von Liebig at University of Giessen. When, in 1845, a school of practical chemistry was started in London, under the style of the Royal College of Chemistry, Hofmann, largely through the influence of the Prince Consort, was appointed its first director. It was with some hesitation that he, then a Privatdozent at Bonn, accepted the position, which may well have seemed rather a precarious one; but the difficulty was removed by his appointment as extraordinary professor at Bonn, with leave of absence for two years, so that he could resume his career in Germany if his English proved unsatisfactory. Fortunately the college was more or less successful, owing largely to his enthusiasm and energy, and many of the men who were trained there subsequently made their mark in chemical history. In 1864 he returned to Bonn, and in the succeeding year he was selected to succeed Eilhard Mitscherlich as professor of chemistry and director of the laboratory in Berlin University.
Hofmann's work covered a wide range of organic chemistry. His first research, carried out in Liebig's laboratory at Giessen, was on coal tar and his investigation of the organic bases in naphtha established the nature of aniline. This substance he referred to as his first love, and it was a love to which he remained faithful throughout his life. His perception of the analogy between it and ammonia led to his famous work on the amines and ammonium bases and the allied organic phosphorus compounds, while his researches on rosaniline, which he first prepared, formed the first of a series of investigations on coloring matter which only ended with quinoline red in 1887.
The Hofmann rearrangement and Hofmann elimination reaction bear his namesake. Hoffmann isolated sorbic acid from rowanberries' oil in 1859, a chemical compound that is widely used as a food preservative.
Hofmann also was the first to introduce molecular models into public lectures, around 1860 following the earlier (1855) suggestion by his colleague William Odling that carbon is tetravalent. Hofmann's colour scheme is still in use by some scientists: carbon = black, hydrogen = white, nitrogen = blue, oxygen = red, chlorine = green, and sulfur = yellow. His models look rather odd nowadays, primarily because Hofmann had them built so that they were, in essence, two-dimensional representations of molecules, and with the carbon atom smaller in size than the hydrogen. (It was Loschmidt in 1861 who probably first appreciated the variations in atomic sizes). After 1874, when van't Hoff and Le Bel independently suggested organic molecules can be three dimensional, molecular models began to assume their modern appearance.
Hofmann voltameter 
The Hofmann voltameter is an apparatus for electrolyzing water, invented by August Wilhelm von Hofmann. It consists of three joined upright cylinders, usually glass. The inner cylinder is open at the top to allow addition of water and an ionic compound to improve conductivity, such as a small amount of sulphuric acid. A platinum electrode is placed inside the bottom of each of the two side cylinders, connected to the positive and negative terminals of a source of electricity. When current is run through Hofmann's Voltameter, gaseous oxygen forms at the anode and gaseous hydrogen at the cathode. Each gas displaces water and collects at the top of the two outer tubes.
See also 
|Wikisource has original works written by or about:
|Wikimedia Commons has media related to: August Wilhelm von Hofmann|
- Ollis, W. D. (1972). "Models and Molecules". Proceedings of the Royal Institution of Great Britain 45: 1–31.
- "Friedhof der Dorotheenstädtischen und Friedrichswerderschen Gemeinden". Retrieved 2009-06-20.
- Oesper, Ralph E. (1968). "The burial place of August Wilhelm Hofmann (1818-1892)". Journal of Chemical Education 45 (3): 153. Bibcode:1968JChEd..45..153O. doi:10.1021/ed045p153.
- "Library and Archive Catalogue". Royal Society. Retrieved 2012-03-10.
- von Hofmann, A. W. Introduction to Modern Chemistry: Experimental and Theoretic; Embodying Twelve Lectures Delivered in the Royal College of Chemistry, London. Walton and Maberly, London, 1866. 
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Hofmann, August Wilhelm von". Encyclopædia Britannica (11th ed.). Cambridge University Press.
Further reading 
- Theodore A. Alston (2003). "The Contributions of A. W. Hofmann". Anesthesia Analgesia 96 (2): 622–625. doi:10.1097/00000539-200302000-00058. PMID 12538223.
- John J. Beer (1960). "A. W. Hofmann and the Founding of the Royal College of Chemistry". Journal of Chemical Education 37 (5): 248–251. Bibcode:1960JChEd..37..248B. doi:10.1021/ed037p248.
- Christoph Meinel (1992). "August Wilhelm Hofmann - Reigning Chemist-in-Chief". Angewandte Chemie International Edition in English 31 (10): 1265–1282. doi:10.1002/anie.199212653.
- William Henry Perkin (1896). "The origin of the coal-tar colour industry, and the contributions of Hofmann and his pupils". Journal Chemical Society Transaction 69: 596. doi:10.1039/CT8966900596.
- Anthony S. Travis (1992). "August Wilhelm Hofmann (1818–1892)". Endeavour 16 (2): 59–65. doi:10.1016/0160-9327(92)90003-8.