Thallium - Wikipedia, the free encyclopedia. Thallium, 8. 1Tl. General properties. Gold Book PDF; FAQ; about; sitemap; A B C D E F G H I J K L M N O P Q R S T U V W X Y Z all (6414 items). Opera (in Spanish; 2001-) (partial serial archives) Opera, (Venetiis, typis F. Petteri, 1781-82), by Saint Ambrose (page images at HathiTrust) Opera; (Oxonii, E typographeo academico, 1837), by Aristotle (page images at. Woolsthorpe, England, 25 December 1642; d. London, England, 20 March 1727) mathematics, dynamics, celestial mechanics, astronomy, optics, natural philosophy. Isaac Newton was born a posthumous child, his. Name, symbolthallium, Tl. Pronunciation. THAL- ee- . This soft gray post- transition metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air. Chemists William Crookes and Claude- Auguste Lamy discovered thallium independently in 1. Both used the newly developed method of flame spectroscopy, in which thallium produces a notable green spectral line. It was isolated by both Lamy and Crookes in 1. Lamy by electrolysis and Crookes by precipitation and melting of the resultant powder. Crookes exhibited it as a powder precipitated by Zinc at the International exhibition which opened on 1 May, that year. The +3 state resembles that of the other elements in group 1. However, the +1 state, which is far more prominent in thallium than the elements above it, recalls the chemistry of alkali metals, and thallium(I) ions are found geologically mostly in potassium- based ores, and (when ingested) are handled in many ways like potassium ions (K+) by ion pumps in living cells. Commercially, however, thallium is produced not from potassium ores, but as a byproduct from refining of heavy metal sulfide ores. The radioisotope thallium- 2. Tl. Cl) is used in small, nontoxic amounts as an agent in a nuclear medicine scan, during one type of nuclear cardiac stress test. Soluble thallium salts (many of which are nearly tasteless) are highly toxic in quantity, and were historically used in rat poisons and insecticides. Use of these compounds has been restricted or banned in many countries, because of their nonselective toxicity. Notably, thallium poisoning results in hair loss. Because of its historic popularity as a murder weapon, thallium has gained notoriety as . However, due to the inert pair effect, the 6s electron pair is relativistically stabilised and it is more difficult to get them involved in chemical bonding than for the heavier elements. Thus, very few electrons are available for metallic bonding, similar to the neighboring elements mercury and lead, and hence thallium, like its congeners, is a soft, highly electrically conducting metal with a low melting point of 3.
It has a metallic luster that, when exposed to air, quickly tarnishes to a bluish- gray tinge, resembling lead. It may be preserved by immersion in oil. A heavy layer of oxide builds up on thallium if left in air. In the presence of water, thallium hydroxide is formed. Sulfuric and nitric acid dissolve thallium rapidly to make the sulfate and nitrate salts, while hydrochloric acid forms an insoluble thallium(I) chloride layer. Tl and 2. 05. Tl are the only stable isotopes and make up nearly all of natural thallium. Tl is the most stable radioisotope, with a half- life of 3. It is the most popular isotope used for thallium nuclear cardiac stress tests. They are moderately strong oxidizing agents and are usually unstable, as illustrated by the positive reduction potential for the Tl. Tl couple. Some mixed- valence compounds are also known, such as Tl. O3 and Tl. Cl. 2, which contain both thallium(I) and thallium(III). Thallium(III) oxide, Tl. O3, is a black solid which decomposes above 8. For instance, thallium(III) fluoride, Tl. F3, has the . The trichloride and tribromide disproportionate just above room temperature to give the monohalides, and thallium triiodide contains the linear triiodide anion (I. In keeping with the large size of the Tl+ cation, the chloride and bromide have the caesium chloride structure, while the fluoride and iodide have distorted sodium chloride structures. Like the analogous silver compounds, Tl. Cl, Tl. Br, and Tl. I are photosensitive. The chemical reactivity of the Tl. Thallium forms the stable . Trimethylthallium and triethylthallium are, like the corresponding gallium and indium compounds, flammable liquids with low melting points. Like indium, thallium cyclopentadienyl compounds contain thallium(I), in contrast to gallium(III). William Crookes and Claude- Auguste Lamy both started to use the new method. William Crookes used it to make spectroscopic determinations for tellurium on selenium compounds deposited in the lead chamber of a sulfuric acid production plant near Tilkerode in the Harz mountains. He had obtained the samples for his research on selenium cyanide from August Hofmann years earlier. He also noticed the new green line in the spectra and concluded that a new element was present. Lamy had received this material from the sulfuric acid plant of his friend Fr. Lamy started to isolate the new element from that source. Lamy was awarded a medal at the International Exhibition in London 1. For the discovery of a new and abundant source of thallium and after heavy protest Crookes also received a medal: thallium, for the discovery of the new element. The controversy between both scientists continued through 1. Most of the discussion ended after Crookes was elected Fellow of the Royal Society in June 1. After several accidents the use as poison was banned in the United States by the Presidential Executive Order 1. February 1. 97. 2. In the subsequent years several other countries also banned the use. The major source of thallium for practical purposes is the trace amount that is found in copper, lead, zinc, and other heavy- metal- sulfideores. Manganese nodules found on the ocean floor 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. However, these minerals are rare, and they have had no commercial importance as sources of thallium. This deposit still contains a loosely estimated 5. 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 electrolysis on platinum or stainless steel plates. 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 high- temperature superconductor, becomes practical for widespread use outside of the laboratory. Since 1. 97. 2 this use has been prohibited in the United States due to safety concerns. Thallium salts were used in the treatment of ringworm, other skin infections and to reduce the night sweating of tuberculosis patients. However this use has been limited due to their narrow therapeutic index, and the development of more advanced medicines for these conditions. The trade name KRS- 5 refers to this material. 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 1. These glasses have room temperature properties that are similar to ordinary glasses and are durable, insoluble in water and have unique refractive indices. In these, the sodium iodide crystals are doped with a small amount of thallium to improve their efficiency as scintillation generators. The research in applications started after the discovery of the first thallium barium calcium copper oxide superconductor in 1. Some mercury- doped thallium- cuprate superconductors have transition temperatures above 1. K at ambient pressure, nearly as high as the world- record- holding mercury cuprates. The nuclide is still used for stress tests for risk stratification in patients with coronary artery disease (CAD). The lead- 2. 01 can be produced in a cyclotron by the bombardment of thallium with protons or deuterons by the (p,3n) and (d,4n) reactions. Viable cardiac cells have normal Na+/K+ ion exchange pumps. The Tl+ cation binds the K+ pumps and is transported into the cells. Exercise or dipyridamole induces widening (vasodilation) of normal coronary arteries. This produces coronary steal from areas where arteries are maximally dilated. Areas of infarct or ischemic tissue will remain . Pre- and post- stress thallium may indicate areas which will benefit from myocardial revascularization. Redistribution indicates the existence of coronary steal and the presence of ischemic coronary artery disease. This alloy is used in thermometers and low- temperature switches. It is a mobile odorless liquid whose color changes from yellowish to clear upon reducing the concentration of the thallium salts. With the density of 4. It was used in the 2. It allows to optimize the lamp temperature and color rendering. There are numerous recorded cases of fatal thallium poisoning. The Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for thallium exposure in the workplace as 0. The National Institute for Occupational Safety and Health (NIOSH) also set a recommended exposure limit (REL) of 0. At levels of 1. 5 mg/m. Thallium(I) compounds have a high aqueous solubility and are readily absorbed through the skin. Exposure by inhalation should not exceed 0. This fact and that it is water- soluble and nearly tasteless led to frequent intoxication caused by accident or criminal intent. Hemodialysis and hemoperfusion 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. The main source of elevated thallium concentrations in water is the leaching of thallium from ore processing operations. Commission on Isotopic Abundances and Atomic Weights^Standard Atomic Weights 2. Commission on Isotopic Abundances and Atomic Weights^Dong, Z.- C.; Corbett, J. CRC Handbook of Chemistry and Physics(PDF) (8. Boca Raton (FL): CRC Press. Henry Curwen Salmon Vol iv July Dec 1. Spectrum Laboratories. The Boron Elements: Boron, Aluminum, Gallium, Indium, Thallium. Rosen Publishing Group. ISBN 9. 78- 1- 4. CRC Handbook of Chemistry and Physics (9. Boca Raton, FL: CRC Press. Lehrbuch der Anorganischen Chemie (in German) (9.
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