Ho - Holmium
|Chemical Element||Holmium||Melting Point °C||1474|
|Chemical Symbol||Ho||Boiling Point °C||2695|
|Atomic Number||67||Density g/cm3||8.8|
Holmium, similarly to most other rare earth elements, is a bright, soft, silvery metal that is also malleable and ductile. It is a member of the lanthanoid group of the Periodic Table and is the 56th most abundant element within the Earth’s crust. Holmium is slowly attacked by water and oxygen and in moist air will form a yellowish oxide. It will also dissolve in acids.
Holmium was discovered by Swedish chemist Per Theodor Cleve, in 1879, and named after Holmia, the ancient name for Stockholm. Cleve used the method championed by Carl Gustaf Mosander, searching for impurities in the oxides of other rare earth elements. Starting with erbia, the oxide of erbium, he first removed all of the identifiable contaminants and then continued processing until he obtained two new materials, holmia and thulia, the respective oxides of holmium and thulium. Independently to this, holmium was also discovered by two Swiss chemists, Marc Delafontaine and Louis Soret, who when analysing the spectral lines of erbium oxide, noticed its characteristic spectral lines and named it “element X”.
The main area of production of holmium is the rare earth mines in Inner Mongolia in China, which is responsible for 97% of all the rare earth elements. The main ores of holmium are the rare earth minerals monazite and gadolinite. In monazite, holmium can be present in as much as 0.5%. Holmium is extracted from those ores that are processed for the yttrium they contain. Other areas in which contain deposits of rare earth ores include the USA, Brazil, India, Greenland and Tanzania. Reserves of holmium are estimated to be in the region of 400,000 tonnes and annual production is said to be about 10 tonnes per year.
Holmium has few commercial applications. It can be used to colour glass yellow and is also used in ceramics, lasers and nuclear applications. Holmium has the highest magnetic moment of any naturally occurring element, and has therefore been used to create the highest known magnetic fields. These magnetic properties are likely to be further exploited in the future.
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