 Discovery Information
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| Who: Sir William Crookes |
| When: 1861 |
| Where: England |
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| Name Origin
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| Greek: thallos (young shoot) from a bright-green line in its spectrum. |
| "Thallium" in different languages. |
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| Sources
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| Found in iron pyrites. Also in the minerals crookesite (TlCu7Se4), hutchinsonite (TlPbAs5S9) and lorandite (TlAsS2). It is found in the Earth's crust at a concentration estimated to be 0.6mg/kg. Annual production is around 30 tons.
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| Abundance
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| Universe: 0.0005 ppm (by weight) |
| Sun: 0.001 ppm (by weight) |
| Carbonaceous meteorite: 0.08 ppm |
| Earth's Crust: 0.6 ppm |
| Seawater: 1.4 x 10-5 ppm
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| Uses
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| Its compounds were used in rat and ant poisons, but this use is no longer allowed in many countries due to safety concerns. Also for in
gamma radiation detecting equipment, detecting infrared radiation and heart muscle research. Thallium sulfide's electrical
conductivity changes with exposure to infrared light therefore making this compound useful in photocells.
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| Combined with sulfur or selenium and arsenic, thallium has been used in the production of high-density glasses that have low melting points in the range of 125 and 150°C. These glasses have room temperature properties that are similar to ordinary glasses and are
durable, insoluble in water and have unique refractive indices.
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| Thallium amalgam is used in thermometers for low temperature, because it freezes at -58°C (pure mercury freezes at -38°C).
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| History
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| Thallium was discovered by Sir William Crookes in 1861 in England while he was making spectroscopic determinations for tellurium on residues from a sulfuric acid plant.
The name comes from Thallium's bright green spectral emission lines. In 1862 Crookes and Claude-Auguste Lamy isolated the metal independently of each other.
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| Notes
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| This metal is very soft and malleable and can be cut with a knife. When it is first exposed to air, thallium has a metallic
luster but quickly tarnishes with a bluish-gray tinge that resembles lead (it is preserved by keeping it under oil). A heavy layer of oxide builds up on thallium if left in air. In the presence of
water, thallium hydroxide is formed.
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| Hazards
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| Thallium and its compounds are highly toxic and should be handled with great care. Thallium is a suspected human carcinogen.
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| Thallium was once an effective murder weapon before its effects became understood and an antidote (prussian blue) discovered. |
