Thallium

Thallium (<img alt="play" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Loudspeaker.svg/11px-Loudspeaker.svg.png" width="11" height="11" /> <a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Key" title="Wikipedia:IPA for English" >ˈθæliəm</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a> <a href="http://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_key" title="Wikipedia:Pronunciation respelling key" >thal-ee-əm</a>) is a chemical element with the symbol Tl and atomic number 81. This soft gray <a href="http://en.wikipedia.org/wiki/Poor_metal" title="Poor metal" class="mw-redirect" >poor metal</a>resembles <a href="http://en.wikipedia.org/wiki/Tin" title="Tin" >tin</a> but discolors when exposed to air. Chemists <a href="http://en.wikipedia.org/wiki/William_Crookes" title="William Crookes" >William Crookes</a> and <a href="http://en.wikipedia.org/wiki/Claude-Auguste_Lamy" title="Claude-Auguste Lamy" >Claude-Auguste Lamy</a> discovered thallium independently in 1861 by the newly developed method of <a href="http://en.wikipedia.org/wiki/Flame_spectroscopy" title="Flame spectroscopy" class="mw-redirect" >flame spectroscopy</a>. Each discovered the new element in residues of <a href="http://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid" >sulfuric acid</a> production.

Approximately 60–70% of thallium production is used in the <a href="http://en.wikipedia.org/wiki/Electronics_industry" title="Electronics industry" >electronics industry</a>, and the remainder is used in the <a href="http://en.wikipedia.org/wiki/Pharmaceutical_industry" title="Pharmaceutical industry" >pharmaceutical industry</a> and in <a href="http://en.wikipedia.org/wiki/Glass" title="Glass" >glass manufacturing</a>.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-sl2001-1" >[2]</a> It is also used in <a href="http://en.wikipedia.org/wiki/Infrared_detector" title="Infrared detector" >infrared detectors</a>. Thallium is highly <a href="http://en.wikipedia.org/wiki/Toxic" title="Toxic" class="mw-redirect" >toxic</a> and was used in <a href="http://en.wikipedia.org/wiki/Rat_poison" title="Rat poison" class="mw-redirect" >rat poisons</a> and<a href="http://en.wikipedia.org/wiki/Insecticide" title="Insecticide" >insecticides</a>. Its use has been reduced or eliminated in many countries because of its nonselective toxicity. Because of its use for<a href="http://en.wikipedia.org/wiki/Murder" title="Murder" >murder</a>, thallium has gained the nicknames "The Poisoner's Poison" and "Inheritance Powder" (alongside <a href="http://en.wikipedia.org/wiki/Arsenic" title="Arsenic" >arsenic</a>).<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-2" >[3]</a>

The <a href="http://en.wikipedia.org/wiki/Odor" title="Odor" >odorless</a> and <a href="http://en.wikipedia.org/wiki/Taste" title="Taste" >tasteless</a> <a href="http://en.wikipedia.org/wiki/Thallium(I)_sulfate" title="Thallium(I) sulfate" >thallium sulfate</a> was once widely used as <a href="http://en.wikipedia.org/wiki/Rat_poison" title="Rat poison" class="mw-redirect" >rat poison</a> and <a href="http://en.wikipedia.org/wiki/Ant" title="Ant" >ant</a> killer. Since 1972 this use has been prohibited in the <a href="http://en.wikipedia.org/wiki/United_States" title="United States" >United States</a> due to safety concerns.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-USGS1972-19" >[20]</a> Many other countries followed this example in the following years.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-sl2001-1" >[2]</a> Thallium salts were used in the treatment of <a href="http://en.wikipedia.org/wiki/Ringworm" title="Ringworm" class="mw-redirect" >ringworm</a>, other <a href="http://en.wikipedia.org/wiki/Skin_infection" title="Skin infection" >skin infections</a> and to reduce the<a href="http://en.wikipedia.org/wiki/Night_sweat" title="Night sweat" class="mw-redirect" >night sweating</a> of <a href="http://en.wikipedia.org/wiki/Tuberculosis" title="Tuberculosis" >tuberculosis</a> patients. However this use has been limited due to their narrow <a href="http://en.wikipedia.org/wiki/Therapeutic_index" title="Therapeutic index" >therapeutic index</a>, and the development of more-advanced medicines for these conditions.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-CRC-27" >[28]</a><a href="http://en.wikipedia.org/wiki/Thallium#cite_note-28" >[29]</a><a href="http://en.wikipedia.org/wiki/Thallium#cite_note-29" >[30]</a>

<h2 >Toxicity</h2>

<div class="rellink relarticle mainarticle" >Main article: <a href="http://en.wikipedia.org/wiki/Thallium_poisoning" title="Thallium poisoning" >Thallium poisoning</a></div>

Thallium and its compounds are extremely toxic, and should be handled with great care. There are numerous recorded cases of fatal thallium poisoning.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-44" >[45]</a> Contact with skin is dangerous, and adequate ventilation should be provided when melting this metal. Thallium(I) compounds have a high aqueous solubility and are readily absorbed through the skin. Exposure to them should not exceed 0.1 mg per m2 of skin in an 8-hour time-weighted average (40-hour work week). Thallium is a suspected human <a href="http://en.wikipedia.org/wiki/Carcinogen" title="Carcinogen" >carcinogen</a>.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-WebEl-45" >[46]</a> For a long time thallium compounds were easily available as rat poison. This fact and that it is water soluble and nearly tasteless led to frequent intoxications caused by accident or criminal intent.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-Murder-18" >[19]</a>

<h2 >[<a href="http://en.wikipedia.org/w/index.php?title=Thallium&action=edit&section=15" title="Edit section: Treatment and internal decontamination" >edit</a>]Treatment and internal decontamination</h2>

One of the main methods of removing thallium (both radioactive and normal) from humans is to use <a href="http://en.wikipedia.org/wiki/Prussian_blue" title="Prussian blue" >Prussian blue</a>, which is a material which absorbs thallium.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-46" >[47]</a> Up to 20 g per day of Prussian blue is fed by mouth to the person, and it passes through their digestive system and comes out in the <a href="http://en.wikipedia.org/wiki/Human_feces" title="Human feces" >stool</a>. <a href="http://en.wikipedia.org/wiki/Hemodialysis" title="Hemodialysis" >Hemodialysis</a> and <a href="http://en.wikipedia.org/wiki/Hemoperfusion" title="Hemoperfusion" >hemoperfusion</a> are also used to remove thallium from the blood serum. At later stage of the treatment additional potassium is used to mobilize thallium from the tissue.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-47" >[48]</a><a href="http://en.wikipedia.org/wiki/Thallium#cite_note-48" >[49]</a>

Although thallium is a modestly abundant element in the Earth's crust, with a concentration estimated to be about 0.7 mg/kg,<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-USGS-CS2010-20" >[21]</a> mostly in association with <a href="http://en.wikipedia.org/wiki/Potassium" title="Potassium" >potassium</a>-based<a href="http://en.wikipedia.org/wiki/Mineral" title="Mineral" >minerals</a> in <a href="http://en.wikipedia.org/wiki/Clay" title="Clay" >clays</a>, <a href="http://en.wikipedia.org/wiki/Soil" title="Soil" >soils</a>, and <a href="http://en.wikipedia.org/wiki/Granite" title="Granite" >granites</a>, thallium is not generally economically recoverable from these sources. The major source of thallium for practical purposes is the trace amount that is found in <a href="http://en.wikipedia.org/wiki/Copper" title="Copper" >copper</a>, <a href="http://en.wikipedia.org/wiki/Lead" title="Lead" >lead</a>, <a href="http://en.wikipedia.org/wiki/Zinc" title="Zinc" >zinc</a>, and other heavy-metal-<a href="http://en.wikipedia.org/wiki/Sulfide" title="Sulfide" >sulfide</a> <a href="http://en.wikipedia.org/wiki/Ore" title="Ore" >ores</a>.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-21" >[22]</a><a href="http://en.wikipedia.org/wiki/Thallium#cite_note-Vira-22" >[23]</a>

Crystals of <a href="http://en.wikipedia.org/wiki/Hutchinsonite" title="Hutchinsonite" >hutchinsonite</a> (TlPbAs5S9)</div>

</div>

Thallium is found in the minerals <a href="http://en.wikipedia.org/wiki/Crookesite" title="Crookesite" >crookesite</a> TlCu7Se4, <a href="http://en.wikipedia.org/wiki/Hutchinsonite" title="Hutchinsonite" >hutchinsonite</a> TlPbAs5S9, and <a href="http://en.wikipedia.org/wiki/Lorandite" title="Lorandite" >lorandite</a> TlAsS2.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-23" >[24]</a> Thallium also occurs as a trace element in <a href="http://en.wikipedia.org/wiki/Iron_pyrite" title="Iron pyrite" class="mw-redirect" >iron pyrite</a>, and thallium is extracted as a by-product of roasting this mineral for the production of <a href="http://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid" >sulfuric acid</a>.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-sl2001-1" >[2]</a><a href="http://en.wikipedia.org/wiki/Thallium#cite_note-Downs-24" >[25]</a>

Thallium can also be obtained from the <a href="http://en.wikipedia.org/wiki/Smelting" title="Smelting" >smelting</a> of lead and zinc ores. <a href="http://en.wikipedia.org/wiki/Manganese_nodule" title="Manganese nodule" >Manganese nodules</a> found on the <a href="http://en.wikipedia.org/wiki/Ocean_floor" title="Ocean floor" class="mw-redirect" >ocean floor</a> also contain some thallium, but the collection of these nodules has been and continues to be prohibitively expensive. There is also the potential for damaging the environment of the oceans.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-25" >[26]</a> In addition, several other thallium minerals, containing 16% to 60% thallium, occur in nature as complexes of sulfides or selenides that primarily contain <a href="http://en.wikipedia.org/wiki/Antimony" title="Antimony" >antimony</a>, <a href="http://en.wikipedia.org/wiki/Arsenic" title="Arsenic" >arsenic</a>, copper, lead, and/or <a href="http://en.wikipedia.org/wiki/Silver" title="Silver" >silver</a>. However, these minerals are rare, and they have had no commercial importance as sources of thallium.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-USGS-CS2010-20" >[21]</a> The <a href="http://en.wikipedia.org/wiki/Allchar_deposit" title="Allchar deposit" >Allchar deposit</a> in southern <a href="http://en.wikipedia.org/wiki/Republic_of_Macedonia" title="Republic of Macedonia" >Macedonia</a> was the only area where thallium was ever actively mined. This deposit still contains a loosely estimated 500 tonnes of thallium, and it is a source for several rare thallium minerals, for example <a href="http://en.wikipedia.org/wiki/Lorandite" title="Lorandite" >lorandite</a>.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-26" >[27]</a>

The <a href="http://en.wikipedia.org/wiki/United_States_Geological_Survey" title="United States Geological Survey" >United States Geological Survey</a> (USGS) estimates that the annual worldwide production of thallium is about 10 metric tonnes as a by-product from the smelting of copper, zinc, and lead ores.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-USGS-CS2010-20" >[21]</a> Thallium is either extracted from the dusts from the smelter flues or from residues such as <a href="http://en.wikipedia.org/wiki/Slag" title="Slag" >slag</a> that are collected at the end of the smelting process.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-USGS-CS2010-20" >[21]</a> The raw materials used for thallium production contain large amounts of other materials and therefore a purification is the first step. The thallium is leached either by the use of a base or sulfuric acid from the material. The thallium is several times precipitated from the solution and to remove further impurities. At the end it is converted to thallium sulfate and the thallium is extracted by <a href="http://en.wikipedia.org/wiki/Electrolysis" title="Electrolysis" >electrolysis</a> on <a href="http://en.wikipedia.org/wiki/Platinum" title="Platinum" >platinum</a> or <a href="http://en.wikipedia.org/wiki/Stainless_steel" title="Stainless steel" >stainless steel</a> plates.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-Downs-24" >[25]</a> The production of thallium decreased by about 33% in the period from 1995 to 2009 – from about 15 metric <a href="http://en.wikipedia.org/wiki/Tonne" title="Tonne" >tonnes</a> to about 10 tonnes. Since there are several small deposits or ores with relatively high thallium content, it would be possible to increase the production of it if a new application, such as a hypothetical thallium-containing <a href="http://en.wikipedia.org/wiki/High-temperature_superconductivity" title="High-temperature superconductivity" >high-temperature superconductor</a>, becomes practical for widespread use outside of the laboratory.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-USGS-CS2010-20" >[21]</a>

<h2 >Thallium pollution</h2>

According to the <a href="http://en.wikipedia.org/wiki/United_States_Environmental_Protection_Agency" title="United States Environmental Protection Agency" >United States Environmental Protection Agency</a> (EPA), man-made sources of thallium pollution include gaseous emission of <a href="http://en.wikipedia.org/wiki/Cement#Heavy_metal_emissions_in_the_air" title="Cement" >cement factories</a>, coal burning power plants, and metal sewers. The main source of elevated thallium concentrations in water is the leaching of thallium from ore processing operations.<a href="http://en.wikipedia.org/wiki/Thallium#cite_note-Vira-22" >[23]</a><a href="http://en.wikipedia.org/wiki/Thallium#cite_note-49" >[50]</a>

Thallium

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