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Friedrich Ernst Dorn

Friedrich Ernst Dorn

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Friedrich Ernst Dorn was a German physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

 who was the first to discover that a radioactive substance, later named radon
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...

, is emitted from radium
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...

.

Life and work


Dorn was born in Guttstadt (Dobre Miasto)
Dobre Miasto
Dobre Miasto is a town in Poland, in Olsztyn County in the Warmian-Masurian Voivodeship. It has 10,579 inhabitants . It is situated in the northwestern part of the Masurian Lake District in the heart of the historical region Warmia...

, Province of Prussia
Province of Prussia
The Province of Prussia was a province of the Kingdom of Prussia from 1829-1878 created out of the provinces of East Prussia and West Prussia....

, and died in Halle
Halle, Saxony-Anhalt
Halle is the largest city in the German state of Saxony-Anhalt. It is also called Halle an der Saale in order to distinguish it from the town of Halle in North Rhine-Westphalia...

, Province of Saxony
Province of Saxony
The Province of Saxony was a province of the Kingdom of Prussia and later the Free State of Prussia from 1816 until 1945. Its capital was Magdeburg.-History:The province was created in 1816 out of the following territories:...

. He was educated at Königsberg
Königsberg
Königsberg was the capital of East Prussia from the Late Middle Ages until 1945 as well as the northernmost and easternmost German city with 286,666 inhabitants . Due to the multicultural society in and around the city, there are several local names for it...

 and went on to teach at the university level. In 1885, at Halle University, Dorn took over the position of personal ordinarius professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...

 for theoretical physics from Anton Oberbeck
Anton Oberbeck
Anton Oberbeck was a German physicist from Berlin. He studied at Heidelberg and the University of Berlin, obtaining his doctorate from the latter in 1868...

. Since Dorn was already an ordinarius professor, he was allowed to assume the title so as to not appear as having been demoted. In 1895, Dorn succeeded Hermann Knoblauch at Halle as the ordinarius professor for experimental physics and director of the physics institute. Dorn’s previous duties were assumed by Karl Schmidt, who had been a Privatdozent
Privatdozent
Privatdozent or Private lecturer is a title conferred in some European university systems, especially in German-speaking countries, for someone who pursues an academic career and holds all formal qualifications to become a tenured university professor...

 and was called as an extraordinarius professor for theoretical physics.

In 1900, Dorn published a paper in which he described experiments that repeated and extended some earlier work on thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....

 by Ernest Rutherford
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson OM, FRS was a New Zealand-born British chemist and physicist who became known as the father of nuclear physics...

. Dorn verified Rutherford's observation that a radioactive material was emitted by thorium, and discovered that a similar emission arose from the element radium
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...

. Additional work by Rutherford and Soddy showed that the same emission came from both thorium and radium, that it was a gas, and that it was actually a new element.

Dorn called the radioactive gaseous product from radium simply "emanation", but in 1904 Rutherford introduced the name "radium emanation" for the same material. Ramsay later suggested "niton", from the Latin word "nitens" meaning "shining". In 1923 the name was again changed, this time to radon
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...

 by an international body of scientists.

Marshall and Marshall have examined the original papers leading to radon's discovery and their work should be consulted for a full treatment and extensive references. They conclude that it is actually Rutherford who should be awarded credit for radon's discovery since he was the first to detect the element being emitted from any radioisotope (thorium) and the first to demonstrate radon's gaseous nature. Rutherford was also the first to integrate his own work on radon with that of others on radon's atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

, its spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

, and its position on the periodic table
Periodic table
The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...

.

Further reading

  • Jungnickel, Christa and Russell McCormmach. Intellectual Mastery of Nature. Theoretical Physics from Ohm to Einstein, Volume 1: The Torch of Mathematics, 1800 to 1870. University of Chicago Press, 1990a.
  • Jungnickel, Christa and Russell McCormmach. Intellectual Mastery of Nature. Theoretical Physics from Ohm to Einstein, Volume 2: The Now Mighty Theoretical Physics, 1870 to 1925. University of Chicago Press, 1990b.