William Crookes
Sir William Crookes (born June 17, 1832 in London , † April 4, 1919 ibid) was a British physicist , chemist , science journalist and parapsychologist . Crookes made cathode rays visible, discovered the fundamentals of luminescence and isotopes , and developed methods to detect ionizing radiation . He discovered the chemical element thallium and the thorium isotope 234 Th.
Live and act
William Crookes was born the eldest son of the second wife of Joseph Crookes, a very wealthy tailor. He attended high school until, at the age of 16, he switched to the Royal College of Chemistry , where August Wilhelm von Hofmann taught. When he was nineteen, Crookes became an assistant at Hofmann's school. A year earlier he had already found a strange residue after experiments with selenium cyanide, which was later characterized as the new chemical element thallium . In 1854 Crookes got a position as a meteorologist at the Ratcliffe Observatory in Oxford and in the same year an apprenticeship as a chemist in Chester .
In 1856 he married Ellen Humphrey and in 1857 he became secretary of the Photographic Society in London.
In addition to his work as a scientist, William Crookes also worked as a journalist. In 1859 he founded “Chemical News”, of which he was editor for many years. In the following years he dealt with luminous phenomena in electron tubes and researched rare earths, which he tried to separate chemically. Another field of activity that Crookes moved around 1900 was radioactivity. He studied substances like uranium and dealt with substances that enabled him to detect radioactivity.
In the course of his life, William Crookes received many honors and awards, including becoming a member of the Royal Society in 1863 and knighted in London in 1897 . In 1910 he received the Order of Merit .
In the last years of his life, one could see that Crookes, like some of his fellow scientists, was attracted to spiritism . He was also a member of the Theosophical Society and called himself a parapsychologist.
Scientific achievements
In 1859 Robert Bunsen and Gustav Robert Kirchhoff developed spectral analysis . Now Crookes was able to detect the chemical element thallium in his earlier selenium separations in spectroscopic experiments - at the same time as Claude Auguste Lamy . It is named after the Greek word thallos ("green scion") because of the green light effect in spectral analysis. The weight of the element was determined by him and gave an atomic weight of 204.04 u. In his weighings he found very small anomalies. These were based on the pressure effect of the light on the evacuated leaves in the balance box and the pressure change due to the influence of temperature according to the kinetic gas theory . These radiometric forces that cause attraction or repulsion are based on electromagnetic radiation such as light. A gimmick still offered in some shops today, the so-called “light windmill” or “ light mill ”, was invented by Crookes in 1873. The device is also called a radiometer in English-speaking countries .
In addition to Wilhelm Hittorf , Crookes also dealt with cathode rays . In a heavily evacuated glass tube, Crookes was able to detect the cathode rays as a shadow- casting cross (in the shadow cross tube ) through a special construction of the anode (made of aluminum ). Cathode rays are - in contrast to canal rays - as invisible as sound waves, but if they hit glass or other substances, this results in a fluorescent glow. By improving the vacuum, Crookes was able to achieve very straight cathode rays; he believed he was observing radiating atoms or matter in a special state.
Crookes called this radiant kind of matter a fourth state of aggregation . In this state matter and force merge. In doing so, he set the basic intellectual building blocks for Einstein's later energy formula .
Different types of vacuum-sealed glass bulbs that exhibit different effects of cathode rays are called Crookes' tubes . E.g. a Crookes Railway Tube in which a wheel with 6 to 8 mica blades rolls with its aluminum axle on a glass rail. The Crookes dark space around the anode in a Crookes tube is named after him, depending on its size and the degree of vacuum .
W. Hittorf had already described the cathode rays before, but without being able to attract the necessary attention. The cathode rays caught the interest of many other scientists. Heinrich Hertz discovered in 1892 that cathode rays can penetrate very thin layers of solid matter. Philipp Lenard extended the experiment by drilling a small hole in the anode and covering it with a thin aluminum foil ( Lenard window ). The rays penetrated the thin foil and also the glass wall and made a substance outside the tube glow. Lenard had proven the free electrons . Joseph John Thomson exposed the cathode rays to a magnetic field. These experiments later led to the determination of the mass of charge carriers and to mass spectroscopy .
Crookes went on to study the state of plasma in evacuated glass tubes under high voltage. He developed the so-called Crookes light tube , with which the basis for the mass production of fluorescent tubes was created.
From 1881 Crookes investigated the influence of cathode rays on chemical substances. He observed the fluorescent light ( luminescent light ) that emanated from the substances through the action of the cathode rays. Using spectral analysis, he now clarified the spectra of numerous substances. With this, Crookes laid the foundations for X-ray spectroscopy . After the spectral analysis he believed he had come across a new chemical element in some substances. In fact, it is about another light phenomenon of heavy metal oxides, the phosphorescence . P. Lenard brought the clarification.
When observing the spectra of rare earths and other metals, Crookes was able to observe many different spectral lines. He assumed that a chemical element not only has one atomic weight, but also consists of atoms with different atomic weights, whereby a certain atomic weight can also clearly predominate. The later work of Soddy, Fajans and Aston was based on these considerations, who were able to determine different atomic weights for an element with the same atomic number (number of protons) by means of mass spectroscopy . Crookes' hypothesis that a chemical element is composed of atoms of different mass was thus confirmed.
Inspired by the discoveries of Marie and Pierre Curie and Henri Becquerels , Crookes turned to uranium salts around 1900 . He precipitated a highly radiation-rich uranium compound (uranium X) from the uranium salt with ammonium carbonate solution . The dissolved uranium salt no longer showed any radioactivity on the photographic plate. Later Sir Ernest Rutherford and Frederick Soddy developed a theory of nuclear decay caused by the emission of α-radiation and the conversion into an atom of another element. Kasimir Fajans was able to use uranium X to explain the exponential function of the β-decay of a radioactive element.
In 1903 Crookes - at the same time as Julius Elster and Hans FK Geitel - was able to detect radioactive radiation from scintillation substances such as zinc sulfide . Crookes developed a small apparatus, a spinariscope , to detect nuclear decay.
In 1900 he discovered the thorium isotope 234 Th. He thus provided the first indication that radioactivity involves the conversion of one element into another.
Crookes was interested in spiritualism and experimented with numerous media , including Daniel Dunglas Home and Florence Cook . He was a member of the Theosophical Society and published some articles in the theosophical journal Sphinx . From 1896 to 1897 he was President of the Society for Psychical Research . In 1906 he was admitted to the Académie des Sciences in Paris and in 1913 to the National Academy of Sciences . Since 1886 he was an elected member of the American Philosophical Society . In 1970 a moon crater was named after him.
Other services
In 1866 he was entrusted by the government with a department for disinfectants against the cattle disease. He pointed out the value of phenols in disinfection. In 1870, Crookes published a paper on beet sugar production . In 1899 he dealt with the sewage issue. In 1908 a document for the production of artificial diamonds followed . In 1910 he wrote a monograph on scandium . From 1910 he developed types of glass for protective goggles against UV rays in glass manufacture. In recognition of this, Crookes Peak has had his name since 1959 , a mountain in Graham Land in Antarctica.
Works
- Spiritualism and science ; Oswald Mutze, Leipzig 1871
- Radiant matter or the fourth state of matter ; Quant and Handel, Leipzig 1879
- Diamonds, by Sir William Crookes. Harpers Brothers, London / New York 1909
literature
- William H. Brock : William Crookes (1832-1919) and the Commercialization of Science. Ashgate 2008.
- Rudolf Tischner (ed.): The medium DD Home, investigations and observations, (after Crookes, Butlerow, Varley, Aksakow and Lord Dunraven). Oswald Mutze, Leipzig 1925.
- Rudolf Tischner (Ed.): Materialization attempts by William Crookes. Oswald Mutze, Leipzig 1923.
- René Zey (ed.): Lexicon of researchers and inventors. Rowohlt Taschenbuch Verlag, ISBN 3-499-16516-3 .
- Crookes, Sir William . In: Encyclopædia Britannica . 11th edition. tape 7 : Constantine Pavlovich - Demidov . London 1910, p. 501–502 (English, full text [ Wikisource ]).
- Günther Bugge: The book of the great chemists. Volume II. Verlag Chemie, Weinheim 1974, ISBN 3-527-25021-2 , pp. 288-298.
- Carus Stars: Radiant Matter . In: The Gazebo . Issue 14, 1880, pp. 224–226 ( full text [ Wikisource ]).
Web links
- Literature by and about William Crookes in the catalog of the German National Library
- Entry to Crookes; Sir; William (1832-1919); Knight Chemist in the Archives of the Royal Society , London
- Overview of historical Crookes tubes. (English)
Individual evidence
- ↑ Cathode ray tube according to Crookes: The Railway Tube No. 1. ( Memento of the original from March 8, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Documentation of the collection of vacuum tubes. Peter Schnetzer, Baden (AG), Switzerland. Around 2005, accessed March 7, 2016.
- ^ List of members since 1666: Letter C. Académie des sciences, accessed on November 3, 2019 (French).
- ^ Member History: Sir William Crookes. American Philosophical Society, accessed July 2, 2018 .
- ↑ Crookes (moon crater) in the Gazetteer of Planetary Nomenclature of the IAU (WGPSN) / USGS
| personal data | |
|---|---|
| SURNAME | Crookes, William |
| BRIEF DESCRIPTION | English physicist, chemist and science journalist |
| DATE OF BIRTH | June 17, 1832 |
| PLACE OF BIRTH | London |
| DATE OF DEATH | April 4, 1919 |
| Place of death | London |