Johann Wilhelm Hittorf
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Johann Wilhelm Hittorf (27 March 1824 – 28 November 1914) was a German physicist who was born in Bonn and died in
Münster Münster (; ) is an independent city#Germany, independent city (''Kreisfreie Stadt'') in North Rhine-Westphalia, Germany. It is in the northern part of the state and is considered to be the cultural centre of the Westphalia region. It is also a ...
, Germany. Hittorf was the first to compute the electricity-carrying capacity of charged atoms and molecules ( ions), an important factor for understanding electrochemical reactions. He formulated ion transport numbers and the first method for their measurements. He experimented with tubes containing energy rays extending from a negative electrode. These rays produced a fluorescence when they hit the glass walls of the tubes. In 1876 the effect was named " cathode rays" by Eugen Goldstein. Hittorf's early investigations concerned the allotropes of
phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
and selenium. Between 1853 and 1859 his most important work concerned ion movement caused by electric current. In 1853 Hittorf revealed that some ions traveled more rapidly than others. This observation resulted in the concept of transport number, the fraction of the electric current carried by each ionic species. He measured the changes of the concentration of electrolyzed solutions, computed from these the transport numbers (relative carrying capacities) of many ions, and, in 1869, published his principles governing the migration of ions. He became professor of physics and chemistry for the University of Münster and director of laboratories there from 1879 until 1889. He also investigated the light spectra of gases and vapours, worked on the passage of electricity through gases, and discovered new properties of cathode rays (electron rays). In 1869 he ascertained that the cathode rays glowed different colours because of different gasses and pressures. He noticed that when there was any object placed between the cathode and the illuminating side of the tube, then the shadow of that object appeared. His work resulted in the development of
cathode-ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...
s. The measurement of current in a vacuum tube was an important factor for the development of vacuum tube diodes.


References


Further reading


Biographical sketch and reprint of paper on migration of ions


External links

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{{DEFAULTSORT:Hittorf, Johann Wilhelm 1824 births 1914 deaths 19th-century German physicists Electrochemists Recipients of the Pour le Mérite (civil class) Scientists from Bonn