AskDefine | Define thallium

Dictionary Definition

thallium n : a soft gray malleable metallic element that resembles tin but discolors on exposure to air; it is highly toxic and is used in rodent and insect poisons; occurs in zinc blende and some iron ores [syn: Tl, atomic number 81]

User Contributed Dictionary

see Thallium

English

Noun

  1. a metallic chemical element (symbol Tl) with atomic number 81.

Translations

External links

For etymology and more information refer to: http://elements.vanderkrogt.net/elem/tl.html (A lot of the translations were taken from that site with permission from the author)

Extensive Definition

Thallium () is a chemical element with the symbol Tl and atomic number 81. This soft gray malleable poor metal resembles tin but discolors when exposed to air. Approximately 60-70% of thallium production is used in the electronics industry, and the rest is used in the pharmaceutical industry and in glass manufacturing.
Thallium metal is obtained as a by-product in the production of sulfuric acid by roasting of pyrites, and also in the smelting of lead and zinc ores. This isotope of thallium can be generated using a transportable generator which is similar to the technetium cow. The generator contains lead-201 (half life 9.33 hours) which decays by electron capture to the thallium-201. The lead-201 can be produced in a cyclotron by the bombardment of thallium with protons or deuterons by the (p,3n) and (d,4n) reactions.
  • 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.
  • an 8.5% thallium amalgam is used in thermometers and switches for use in low temperatures, because it freezes at -58 °C (pure mercury freezes at -38 °C). 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.

Occurrence

Although the metal is reasonably abundant in the Earth's crust at a concentration estimated to be about 0.7 mg/kg, mostly in association with potassium minerals in clays, soils, and granites, it is not generally considered to be commercially recoverable from those forms. The major source of commercial thallium is the trace amounts found in copper, lead, zinc, and other sulfide ores.
Thallium is found in the minerals crookesite TlCu7Se4, hutchinsonite TlPbAs5S9, and lorandite TlAsS2. It also occurs as trace in pyrites and extracted as a by-product of roasting this ore for sulfuric acid production. The metal can be obtained from the smelting of lead and zinc rich ores. Manganese nodules found on the ocean floor also contain thallium, but nodule extraction is prohibitively expensive and potentially environmentally destructive. In addition, several other thallium minerals, containing 16% to 60% thallium, occur in nature as sulfide or selenide complexes with antimony, arsenic, copper, lead, and silver, but are rare, and have no commercial importance as sources of this element. See also: :Category:Thallium minerals.

Isotopes

Thallium has 25 isotopes which have atomic masses that range from 184 to 210. 203Tl and 205Tl are the only stable isotopes, and 204Tl is the most stable radioisotope, with a half-life of 3.78 years.
202Th (half life 12.23 days) can be made in a cyclotron, while 204Th (half life 3.78 years) is made by the neutron activation of stable thallium in a nuclear reactor.

Compounds

Fluorides: TlF, TlF3 Chlorides: TlCl, TlCl2, TlCl3 Bromides: TlBr, Tl2Br4 Iodides: TlI, TlI3 Hydrides: none listed Oxides: Tl2O, Tl2O3 Sulfides: Tl2S Selenides: Tl2Se Tellurides: none listed Nitrides: none listed

Toxicity

Thallium and its compounds are very toxic, and should be handled with great carehttp://www.webelements.com/webelements/elements/text/Tl/biol.html. Contact with skin is dangerous, and adequate ventilation should be provided when melting this metalhttp://www.webelements.com/webelements/elements/text/Tl/biol.htm.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 of skin in an 8-hour time-weighted average (40-hour work week). Thallium is a suspected human carcinogen.
Part of the reason for thallium's high toxicity is that, when present in aqueous solution as the univalent thallium(I) ion (Tl+), it exhibits some similarities with essential alkali metal cations, particularly potassium (as the atomic radius is almost identical). It can thus enter the body via potassium uptake pathways. However, other aspects of thallium's chemistry are very different from that of the alkali metals (e.g., its high affinity for sulfur ligands due to the presence of empty d-orbitals), and so this substitution disrupts many cellular processes (for instance, thallium may attack sulfur-containing proteins such as cysteine residues and ferredoxins).
Thallium's toxicity has led to its use (now discontinued in many countries) as a rat and ant poison.
Among the distinctive effects of thallium poisoning are loss of hair (which led it to its initial use as a depilatory before its toxicity was properly appreciated) and damage to peripheral nerves (victims may experience a sensation of walking on hot coals). Thallium was once an effective murder weapon before its effects became understood, and an antidote (prussian blue) discovered.

Treatment and internal decontamination

One of the main methods of removing thallium (both radioactive and normal) from humans is to use Prussian blue, which is a solid ion exchange material which absorbs thallium and releases potassium. The prussian blue is fed by mouth to the person, and it passes through their digestive system and comes out in the stool.

Famous uses as a poison

  • In 1953, Australian Caroline Grills was sentenced to life in prison after three family members and a close family friend died. Authorities found thallium in tea that she had given to two additional family members.
  • In 1957, Nikolai Khokhlov, a former KGB assassin, was poisoned with thallium. Khokhlov fell ill with stomach cramps and nausea and within days his hair had fallen out and he was covered with marks on his skin. He fled the Soviet Union to Germany where doctors suspected thallium poisoning and tried every known antidote without success. Khokhlov was then taken to the US hospital and treated with hydrocortisone, steroids, and blood and plasma transfusions and he eventually recovered.
  • In 1971, thallium was the main poison that Graham Frederick Young used to poison around 70 people in the English village of Bovingdon, Hertfordshire, of which 2 died.
  • Zhu Ling (1973) the victim of an unsolved 1995 thallium poisoning case in Beijing, China.In 1994, Zhu Ling was a sophomore in Class Wuhua2 (Physical Chemistry) at Tsinghua University in Beijing She began to show strange and debilitating symptoms at the end of 1994, when she reported experiencing acute stomach pain, along with extensive hair loss ultimately she was diagnosed on Usenet with poisoning by thallium .To this date speculation of the true poisoner is still discussed by many Chinese expatriates overseas
  • In 1988, members of the Carr family from Alturas, Polk County, Florida fell ill from what appeared to be thallium poisoning. Peggy Carr, the mother, died slowly and painfully from the poison. Her son and stepson were critically ill but eventually recovered. The Carr's neighbor, George J. Trepal, a chemist and member of Mensa, was convicted of murdering Mrs. Carr and attempting to murder her family and sentenced to death. The thallium was slipped into bottles of Coca-Cola at the Carr's home and Trepal's.
  • In June 2004, 25 Russian soldiers earned Honorable Mention Darwin Awards after becoming ill from thallium exposure when they found a can of mysterious white powder in a rubbish dump on their base at Khabarovsk in the Russian Far East. Oblivious to the danger of misusing an unidentified white powder from a military dump site, the conscripts added it to tobacco, and used it as a substitute for talcum powder on their feet.
  • In 2005, a 17 year old girl in Numazu, Shizuoka, Japan, admitted to attempting to murder her mother by lacing her tea with thallium, causing a national scandal.
  • In February 2007, two Americans, Marina and Yana Kovalevsky, a mother and daughter, visiting Russia were hospitalized due to thallium poisoning. Both had emigrated from the Soviet Union to the United States in 1989 and had made several trips to Russia since then.
  • In February 2008, members of Iraqi air force club and some of their children were poisoned by cake laced with thallium. Two of the children died.

In fiction

  • "Concentrated thallium" is used as the poison of choice of the Wyoming Widow in the 2006 comedy Big Nothing
thallium in Arabic: ثاليوم
thallium in Bengali: থ্যালিয়াম
thallium in Bosnian: Talijum
thallium in Catalan: Tal·li
thallium in Czech: Thallium
thallium in Corsican: Talliu
thallium in Danish: Thallium
thallium in German: Thallium
thallium in Estonian: Tallium
thallium in Modern Greek (1453-): Θάλλιο
thallium in Spanish: Talio
thallium in Esperanto: Talio
thallium in Basque: Talio
thallium in French: Thallium
thallium in Friulian: Tali
thallium in Irish: Tailliam
thallium in Manx: Thallium
thallium in Galician: Talio
thallium in Korean: 탈륨
thallium in Armenian: Թալիում
thallium in Croatian: Talij
thallium in Ido: Talio
thallium in Indonesian: Talium
thallium in Icelandic: Þallín
thallium in Italian: Tallio
thallium in Hebrew: תליום
thallium in Kannada: ಥಾಲಿಯಮ್
thallium in Swahili (macrolanguage): Tali
thallium in Haitian: Talyòm
thallium in Kurdish: Talyûm
thallium in Latin: Thallium
thallium in Latvian: Tallijs
thallium in Luxembourgish: Thallium
thallium in Lithuanian: Talis (elementas)
thallium in Lojban: jinmrtali
thallium in Hungarian: Tallium
thallium in Dutch: Thallium
thallium in Japanese: タリウム
thallium in Norwegian: Thallium
thallium in Norwegian Nynorsk: Thallium
thallium in Occitan (post 1500): Talli
thallium in Polish: Tal
thallium in Portuguese: Tálio
thallium in Quechua: Thalyu
thallium in Russian: Таллий
thallium in Sicilian: Tàlliu
thallium in Simple English: Thallium
thallium in Slovak: Tálium
thallium in Slovenian: Talij
thallium in Serbian: Талијум
thallium in Serbo-Croatian: Talijum
thallium in Finnish: Tallium
thallium in Swedish: Tallium
thallium in Thai: แทลเลียม
thallium in Vietnamese: Tali
thallium in Turkish: Talyum
thallium in Ukrainian: Талій
thallium in Chinese: 铊
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