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Two Hundred Years Selenium Fathi Habashi Laval University From the SelectedWorks of Fathi Habashi July, 2017 Two Hundred Years Selenium Fathi Habashi Available at: https://works.bepress.com/fathi_habashi/217/ METALL-RUBMETALL-HISTORIKRISCH Two Hundred Years Selenium Habashi, F. (1) Beside selenium discovered in 1817, Jöns Jacob Berzelius (1779-1848) discov- ered cerium in 1814, thorium in 1815, and silicon in 1823. Together with his stu- dent Johan August Arfwedson (1792-1841) he discovered lithium in 1817 and played an important role in the discovery of vanadium. elenium was discovered in 1817 in the red mud accumulated at the bottom of a sulfuric acid lead chamber plant in which Berzelius S(Fig. 1) was a partner. The acid was manu- Fig. 3: A representation of Selene the god- factured from pyrite from Falun – the dess of the Moon old mine in Sweden (Figure 2). Berzelius named the new element after Selene the ent on purity. Thus, the conductivity of goddess of the Moon (Figure 3) in anal- selenium, including the poorly conducting ogy with tellurium meaning Earth which amorphous form, can be increased consid- was discovered earlier in 1782 in a gold ore erably by traces (a few parts per million) of in Transylvania in the Austrian Empire. halide ions or by alloying elements such as The element was first mistaken for tellu- tellurium or arsenic. Because the electri- rium but on careful examination Berzelius cal properties are sensitive to the presence of crystal defects, the purity of selenium, which can be deliberately controlled by doping or alloying with other elements, plays an important role in its use in electri- cal and electronic applications. The relative abundance in Earth’s crust is 9 x 10-6 %. In its compounds, selenium exhibits the Fig. 2: Falun Mine in Sweden oxidation states -2, +4, and +6. Selenium burns in air to form selenium dioxide, ing of these metals to 2 - 15% from which which has the smell of rotten radishes. it is obtained by a long processing. Selenium is oxidized by nitric acid to sele- Red amorphous selenium is produced by reducing selenous acid with sulfur diox- ide, by crystallization from solution, or by quenching of selenium vapor or molten selenium. It consists of Se8 rings (Figure Fig. 1: Jöns Jacob Berzelius (1779-1848) 5) similar to elemental sulfur, soluble in carbon disulfide giving red solutions from found that it was a new element. When he which selenium can be crystallized. Red digested the mass with aqua regia at mod- selenium is an electrical non-conductor. erate temperature was able to isolate the On heating at 100-150°C is transformed new element. He reported that selenium into the stable, grey, hexagonal metal-like had properties between sulfur and telluri- form in an exothermic reaction (Figure um. Later he investigated the Falun pyrite 6, Table 1). In the vapor phase, red sele- Fig. 4: Grey and red selenium and found that it contained 0.15% seleni- nium exists mainly as Se8 rings. At higher um. At present all lead chamber acid plants temperature these decompose into smaller are shut down and pyrite is no longer used units, eventually forming Se2 molecules. in making sulfuric acid since all plants are The grey, hexagonal crystals have metal- using elemental sulfur. lic appearance, and is composed of helical Selenium is known in two varieties: grey chains which melts at 220°C. It is a semi- and red (Figure 4). At present it is a by- conductor whose electrical conductiv- product of the extraction of copper and ity increases by a factor >1000 under the nickel from their sulfide ores. It is concen- influence of light (photoconductivity). The Fig. 5: Structure of red selenium [top] trated in the anodic slimes of electrorefin- electrical conductivity is strongly depend- and grey selenium [bottom] 234 6/20116/2017 | 65.71. Jahrgang | METALL METALL-HISTOMETALL-RUBRISCHRIK Red Grey 1802 on galvanotherapy inspired by Volta’s Appearance Red powder Grey invention of the galvanic pile two years ear- metallic lier. In 1807, he was appointed professor of Form ---- Hexagonal medicine and pharmacy (later chemistry and pharmacy) in Stockholm, and in 1819 Density 4.42 4.80 he was appointed secretary of the Academy Melting 144°C 220.2°C of Science. There he obtained a laboratory, point a library, and an apartment in the Acad- Solubility in Slightly Insoluble emy building. His students discovered a Fig. 6: Red amorphous selenium is transformed into CS2 soluble number of metals: crystalline variety on heating W Heinrich Rose discovered niobium in Table 1: Crystalline modifications of sele- 1820 gart (1832-33) in three volumes (1,505 pag- nium W Carl Gustaf Mosander discovered lan- es) and in Quedlinburg (1833-43) in four thanum, didymium [which was resolved volumes (2,327 pages). Translations into nous acid. Hot, concentrated sulfuric acid later into praseodymium, neodymium, other languages were also published. dissolves selenium, giving a green color samarium, and europium by others], Berzelius founded and edited a chemi- and forming polymeric selenium cations, erbium, and terbium in the period 1824- cal journal and published a summary of for example: 1831 Prominent Berzelius’ students and 2+ - Se8 + 3H2SO4 → Se8 + 2HSO4 + SO2 + co workers are shown in Table 2. 2H2O Writings With chlorine, vigorous oxidation to selenium tetrachloride occurs. Selenium Berzelius’ work in chemistry was remark- reacts with electropositive elements (e.g., able. He was the first to determine accu- many metals) to form selenides and is rately the atomic weight of the elements. therefore strongly corrosive, especially at He systematized the chemical language high temperature. With hydrogen, the tox- by introducing the chemical symbols for ic gas hydrogen selenide, H2Se, is formed. the elements and compounds that we use Although selenium is an essential trace ele- today. He invented the concepts of cataly- Fig. 7: Berzelius book in Swedish Lärbok i ment, it is toxic if taken in excess. sis and isomerism. He wrote an important Kemien in six volumes [1808-1830] textbook of chemistry in Swedish (Figure Berzelius 7) which was translated into German and then revised and updated into five editions Berzelius studied medicine at the Univer- from Swedish manuscripts. Beside these, sity of Uppsala and wrote a dissertation in unauthorized editions appeared in Stutt- Table 2 - Prominent Berzelius’ students and coworkers Fig. 8 - 10: Berzelius’ Museum METALL | 65.71. Jahrgang | 6/20116/2017 235 METALL-RUBMETALL-HISTORIKRISCH him were erected in Stockholm (Figure 15) in addition to postage stamps (Figure 16) and medals in his honour (Figure 17). Occurrence of selenium Ignaz Domeyko discovered in Chile in 1861 a silver-copper mineral in Cacheuta containing 22.4 to 30.8% Se now known Fig. 16: Berzelius stamps in Sweden as cacheutite. Other minerals containing selenium were later discovered. Fig. 17: Berzelius medal mid-1870s. Selenium transmits an electric current proportional to the amount of light falling on its surface. This phenomenon was used in the design of light meters and similar devices. Selenium’s semiconductor properties found numerous other applica- tions in electronics. The development of selenium rectifiers began during the early 1930s. Fig. 11 - 13: Chemicals in Berzelius Museum References - F. Habashi, The Story of Metals - Volume 2, Métallurgie Extractive Québec 2015. Distrib- progress in chemistry each year in the form uted by Laval University Bookstore, www. of Annual Reports which were translated zone.ul.ca - F. Habashi, Chemistry and Metallurgy in in German. His scientific correspondence the Great Empires, Métallurgie Extractive with chemists of the time, published after Fig. 15: Berzelius statue in Stockholm Québec, Québec City, Canada 2009. Distrib- uted by Laval University Bookstore, www. his death in numerous volumes, filled zone.ul.ca thousands of pages. He also kept a diary of Uses - M. E. Weeks, The Discovery of the Elements, Journal of Chemical Education, Easton, PA his travels which was published in a 430- 1956 page volume. In 1873, the British electrical engineer Willoughby Smith (1828-1891) (Figure 18) Legacy found that the electrical resistance of grey (1) Fathi Habashi, Department of Mining, selenium was dependent on the ambient Metallurgical, and Materials Engi- Berzelius’ laboratory equipment, speci- light. This led to its use as a cell for sens- neering, Laval University, Quebec City, mens, and other personal effects are kept ing light. The first commercial products Canada in a Museum maintained by the Academy were developed by Werner Siemens in the in Stockholm (Figures 8-14). A statue for Se2017 – 200 Years of Selenium Reserch An international selenium conference will be held at Karolinska Institutet in Stockholm on August 13-17, 2017. The conference will cover all fields of current selenium research, with a special focus on biology, medicine, biomedicine and the environment. www.se2017.se Bild 6: Sandwich 1 (unten), Qualität schlecht (Tabelle 2). Fig. 14: Chemicals prepared by Berzelius Fig. 18: Willoughby Smith (1828-1891) 236 6/20116/2017 | 65.71. Jahrgang | METALL.
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