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It is the least electronegative element with stable isotopes, of which it has only one, caesium-133. Caesium is mined mostly from pollucite, while the radioisotopes, especially caesium-137, are extracted from waste produced by nuclear reactors. German chemists Robert Bunsen and Gustav Kirchhoff discovered caesium in 1860 by flame spectroscopy.
Robert Wilhelm Eberhard Bunsen (German:; 30 March 1811 [a] – 16 August 1899) was a German chemist.He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. [11]
[note 1] [74] [75] [76] Caesium was the first element to be discovered with a spectroscope, which had been invented by Bunsen and Kirchhoff only a year previously. [ 17 ] To obtain a pure sample of caesium, 44,000 litres (9,700 imp gal; 12,000 US gal) of mineral water had to be evaporated to yield 240 kilograms (530 lb) of concentrated salt ...
In 1860, the unexpected appearance of sky-blue and dark red was observed in spectral emissions by Robert Bunsen and Gustav Kirchhoff, leading to the discovery of two alkali metals, caesium and rubidium (dark red). [4] [1] Today, this low-cost method is used in secondary education to teach students to detect metals in samples qualitatively. [2]
Prices of hydrogen produced by distributed steam methane reforming, as predicted by H2A Production Model from United States Department of Energy, [9] assuming price of natural gas of US$3/MMBtu (US$10/MWh; US$0.10/m 3). Does not include cost of storage and distribution. 1: 2 H (D) Deuterium: 0.0001667 [10] 13 400: 2.23: 2020: CIL [11]
Bunsen was joined in his research by Gustav Kirchhoff. Kirchhoff used the concept of the dispersion of white light by a prism in the invention of the spectroscope , a device with a prism at its centre which split the light from Bunsen's flames into distinct bands of its constituent colours – the element's spectral lines .
He also worked at different chemical institutions. Around this period, Kirchhoff and Bunsen invented the spectroscope. Kirchhoff used the instrument to pioneer the identification of the elements in the Sun. In 1859, he showed that the Sun contained sodium. Kirchhoff and Bunsen discovered caesium and rubidium in 1861.
1860–61: Discovery of caesium and rubidium by Robert Bunsen and Gustav Kirchhoff [139] 1860: Erlenmeyer flask by Emil Erlenmeyer [ 140 ] 1863–64: Discovery of indium by Ferdinand Reich and Hieronymous Theodor Richter [ 141 ] [ 142 ] [ 143 ]