 Discovery Information
|
| Who: Jöns Berzelius |
| When: 1817 |
| Where: Sweden |
|
| Name Origin
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| Greek: Selene (Moon) |
| "Selenium" in different languages. |
|
| Sources
|
| Obtained from lead, silver, copper and nickel refining.
|
| Important producers are Canada, the USA, Bolivia and Russia. Around 600 tons are produced annually.
|
|
| Abundance
|
| Universe: 0.03 ppm (by weight) |
| Carbonaceous meteorite: 130 ppm |
| Earth's Crust: 0.05 ppm |
| Seawater: |
| Atlantic surface: 4.6 x 10-8 ppm
|
| Atlantic deep: 1.8 x 10-7 ppm
|
| Pacific surface: 1.5 x 10-8 ppm
|
| Pacific deep: 1.65 x 10-7 ppm
|
| Human: |
| 50 ppb by weight |
| 4 ppb by atoms |
|
| Uses
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| Used in photoelectric cells, TV cameras, as a semiconductor in solar batteries, light meters, copy machines, anti-dandruff
shampoo and rectifiers. Also colours glass red.
|
|
| History
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| Selenium was discovered in 1817 by Jöns Jakob Berzelius who found the element associated with tellurium (named for the Earth).
|
| Growth in selenium consumption was historically driven by steady development of new uses, including applications in rubber
compounding, steel alloying, and selenium rectifiers. By 1970, selenium in rectifiers had largely been replaced by silicon, but its use as a photoconductor in plain paper copiers had become its leading application. During the 1980s, the photoconductor
application declined (although it was still a large end-use) as more and more copiers using organic photoconductors were produced.
Presently, the largest use of selenium world-wide is in glass manufacturing, followed by uses in chemicals and pigments. Electronic
use, despite a number of continued applications, continues to decline.
|
| In 1996, continuing research showed a positive correlation between selenium supplementation and cancer prevention in humans,
but widespread direct application of this important finding would not add significantly to demand owing to the small doses
required. In the late 1990s, the use of selenium (usually with bismuth) as an additive to plumbing brasses to meet no-lead environmental standards, became important. At present, total world selenium production continues to increase modestly.
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|
| Notes
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| Conducts electricity when struck by light. Selenium is found (and even appears to be required at very low levels) in humans,
but in trace amounts.
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| Some clinical studies have shown that selenium may help cut the risk of certain cancers. |
|
| Hazards
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| Selenium and its compounds are extremely toxic and behave in the same way as arsenic. May be fatal if inhaled, ingested or absorbed through skin.
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