Indium
Indium is a metal element denoted by the atomic symbol In. Its atomic number is 49 and its atomic weight is 114.82. It has a melting point of 313.9°F (156.6°C) and a boiling point of 3,761.6°F (2,072°C). Indium does not occur in an elemental state in nature, but its sulfide is a common impurity in ores of zinc and lead. The element is a very lustrous, silvery metal that bends easily.
The development of spectroscopic analysis by Gustav Kirchhoffand Robert Bunsen in 1859 rapidly lead to the discovery of four new elements, cesium, rubidium, thallium, and indium. The last of these was found by Ferdinand Reich (1799-1882) and Hieronymus Theodor Richter (1824-1898) in 1863.
Reich was born in Bernburg, Germany, on February 19, 1799. He was educated in chemistry and mineralogy at Leipzig, Freiberg, Göttingen, and Paris. He was associated with the Freiberg School of Mines for more than forty years, from 1824 to 1866. During that time, Reich served as inspector of the school and taught courses in mineralogy and chemistry. He also assumed many administrative duties including supervision of the mineral collection, purchasing of supplies, cataloging library resources, and maintaining school records. While in Paris, Reich learned about the metric system. When he returned to Saxony, he promoted the new system enthusiastically and oversaw its adoption throughout the state.
In 1863, Reich took up the study of zinc ores recovered from a mine at Himmelfürst. His analysis produced a yellow precipitate that he suspected might contain a new element. The best way to confirm his beliefs was to conduct a spectroscopic analysis of the material. At this point, however, Reich had to confront a physical handicap. He was color-blind. He would not be able to detect the distinctive lines produced by the spectroscope, and recognize the presence of the new element. As a result, he turned the yellow material over to his assistant, Richter, for spectroscopic analysis.
Richter was born in Dresden on November 21, 1824. He studied metallurgy eventually becoming an authority in assaying and blow-pipe analysis. In 1875, Richter became director of the Freiberg School of Mines. Richter rather quickly confirmed Reich's suspicions about the yellow precipitate. When heated in a Bunsen burner flame and then observed with the spectroscope, the material produced two distinctive blue lines that had not previously been observed. Because of this characteristic blue color, Reich and Richter named the element indium, for "indigo." In 1863, they obtained an impure sample of the metal itself. The joint project on indium did not end well. For some time, Richter tried to suggest that he alone had discovered the element. No doubt exists, however, about Reich's role in initiating the project.
Indium is used in making alloys, one of which—with gallium—is liquid at room temperature. Other alloys are used in bearings, in dental amalgams, and in nuclear control rods. Compounds of the metal, such as the antimonide, arsenide, phosphide, selenide, and telluride, are also used in solid-state electronic devices and in electronics research.
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