The thallium is a chemical element of symbol Tl and atomic number 81.

History

Thallium was discovered by the English chemist William Crookes in 1861 in England whereas this one studied by spectroscopy the light emitted by an ore of Sélénium heated. Claude Auguste Lamy will be the first to be isolated, the same year, metal thallium.

Its name thallium , in scientific Latin, comes from the Greek θαλλός thallos " bourgeon" , because of its spectral line of emission green shining (same the étymon gave in French the word Thalle " connect verte").

Notable characteristics

It is a metal gray, malleable, very tender (cuts itself to the knife) which resembles lead and tarnishes as him when it is exposed to the air.

It is produced starting from pyrites at the same time as the sulphuric acid like during the extraction of lead and zinc.

It is present in the underwater manganese nodules.

Uses

  • Thermometer: Forming with mercury, an Eutectic liquid remainder up to -60 °C, the mixture Hg (91,5%) - Tl (8,5%) is used in the thermometers for very cold areas.
  • Infra-red Window : the thallium halides (chloride, bromide and iodide) are transparent with the infra-red radiation and are used to manufacture windows of entry for the detectors infra-red.
  • Lighting: It is used in certain lamps with metal halides in the form of thallium iodide which gives a green light output.
  • the 201thallium is a radioactive isotope setting in particular on the cardiac muscle and which is thus used in cardiac Scintigraphie for the study of the perfusion or myocardic viability.

It is also used in the detectors of infra-red, in particular the Tl2S. sulfide.

Precautions

Thallium is highly toxic: it is present in certain Insecticide S and was sometimes used as a Poison because, reduced out of powder, it is odorless, colorless and the lethal amount accounts for 1 gram.

The use of thallium as an insecticide tends to disappear since its carcinogenic effect was shown.

Simple: Thallium

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