 Discovery Information
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| Who: Per Theodor Cleve |
| When: 1879 |
| Where: Sweden |
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| Name Origin
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| From Thule ancient name of Scandinavia. |
| "Thulium" in different languages. |
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| Sources
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| Found with other rare earths in the minerals; monazite, gadolinite, euxenite ((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6), xenotime, and others.
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| Primary producers are the USA, Brazil, India, Sri Lanka and Australia. Annual production is around 50 tons.
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| Abundance
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| Universe: 0.0001 ppm (by weight) |
| Sun: 0.0002 ppm (by weight) |
| Carbonaceous meteorite: 0.03 ppm |
| Earth's Crust: 0.48 ppm |
| Seawater: |
| Atlantic surface: 1.3 x 10-7 ppm
|
| Atlantic deep: 1.6 x 10-7 ppm
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| Pacific surface: 7 x 10-8 ppm
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| Pacific deep: 3.3 x 10-7 ppm
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| Uses
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| None of thulium's compounds is commercially important mainly due to high production costs. Radioactive thulium is used to power portable x-ray machines,
eliminating the need for electrical equipment.
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| Thulium-doped calcium sulphate (CaSO4) has been used in personal radiation dosimeters because it can register, by its fluorescence, especially low levels.
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| History
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| Thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in the oxides of other rare earth elements (this was the same method Carl Gustaf Mosander earlier used to discover some other rare earth elements). Cleve started by removing all of the known contaminants of erbia (Er2O3) and upon additional processing, obtained two new substances; one brown and one green. The brown substance turned out to
be the oxide of the element holmium and was named holmia by Cleve and the green substance was the oxide of an unknown element. Cleve named the oxide thulia and its element thulium after Thule, Scandinavia.
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| Thulium was so rare, that none of the early workers had enough of it to purify sufficiently to actually see the green colour;
they had to be content with observing the strengthening of the two characteristic absorption bands, as erbium was progressively removed. The first researcher to obtain thulium nearly pure was the British expatriate working on a large
scale at New Hampshire College in Durham NH: Charles James. In 1911, he reported his results, having used his discovered method
of bromate fractional crystallization to do the purification. He famously needed 15,000 "operations" to establish that the
material was homogeneous.
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| Notes
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| Thulium is the least abundant of the rare earth metals, is is and easy metal to work as it can be cut by a knife. Reserves
of thulium are estimated to be about 105 tonnes. World production is about 50 tonnes per year as thulium oxide.
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| Hazards
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| Thulium has a low-to-moderate acute toxic rating and should be handled with care. Metallic thulium in dust form presents a
fire and explosion hazard.
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