Thallium

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Thallium, 81Tl
Thallium
Pronunciation/ˈθæliəm/ (THAL-ee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Tl)
Thallium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
In

Tl

Nh
mercurythalliumlead
kJ/mol
Heat of vaporization165 kJ/mol
Molar heat capacity26.32 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 882 977 1097 1252 1461 1758
Atomic properties
Discovery
William Crookes (1861)
First isolationClaude-Auguste Lamy (1862)
Isotopes of thallium
Main isotopes[7] Decay
abun­dance half-life (t1/2) mode pro­duct
201Tl synth 3.0421 d ε 201Hg
203Tl 29.5%
stable
204Tl synth 3.78 y
β
204Pb
ε + β+
204Hg
205Tl 70.5% stable
 Category: Thallium
| references

Thallium is a

flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, from Greek θαλλός, thallós, meaning "green shoot" or "twig", was named by Crookes. It was isolated by both Lamy and Crookes in 1862; 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.[8]

Thallium tends to form the +3 and +1 oxidation states. The +3 state resembles that of the other elements in

group 13 (boron, aluminium, gallium, indium). 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, thallium is produced not from potassium ores, but as a byproduct from refining of heavy-metal sulfide ores. Approximately 65% of thallium production is used in the electronics industry, and the remainder is used in the pharmaceutical industry and in glass manufacturing.[9] It is also used in infrared detectors. The radioisotope thallium-201 (as the soluble chloride TlCl) is used in small 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

rat poisons and insecticides. Because of their nonselective toxicity, use of these compounds has been restricted or banned in many countries. Thallium poisoning usually results in hair loss. Because of its historic popularity as a murder weapon, thallium has gained notoriety as "the poisoner's poison" and "inheritance powder" (alongside arsenic).[10]

Characteristics

A thallium atom has 81 electrons, arranged in the electron configuration [Xe]4f145d106s26p1; of these, the three outermost electrons in the sixth shell are valence electrons. Due to the

inert pair effect, the 6s electron pair is relativistically stabilised and it is more difficult to get these involved in chemical bonding than it is for the heavier elements. Thus, very few electrons are available for metallic bonding, similar to the neighboring elements mercury and lead. Thallium, then, like its congeners, is a soft, highly electrically conducting metal with a low melting point, of 304 °C.[11]

A number of standard electrode potentials, depending on the reaction under study,[12] are reported for thallium, reflecting the greatly decreased stability of the +3 oxidation state:[11]

+0.73 Tl3+ + 3 e ↔ Tl
−0.336 Tl+ + e ↔ Tl

Thallium is the first element in group 13 where the reduction of the +3 oxidation state to the +1 oxidation state is spontaneous under standard conditions.[11] Since bond energies decrease down the group, with thallium, the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the 6s-electrons.[13] Accordingly, thallium(I) oxide and hydroxide are more basic and thallium(III) oxide and hydroxide are more acidic, showing that thallium conforms to the general rule of elements being more electropositive in their lower oxidation states.[13]

Thallium is malleable and sectile enough to be cut with a knife at room temperature. 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 acids dissolve thallium rapidly to make the sulfate and nitrate salts, while hydrochloric acid forms an insoluble thallium(I) chloride layer.[14]

Isotopes

Thallium has 41

radioisotope, with a half-life of 3.78 years.[15] It is made by the neutron activation of stable thallium in a nuclear reactor.[15][16] The most useful radioisotope, 201Tl (half-life 73 hours), decays by electron capture, emitting X-rays (~70–80 keV), and photons of 135 and 167 keV in 10% total abundance;[15] therefore, it has good imaging characteristics without an excessive patient-radiation dose. It is the most popular isotope used for thallium nuclear cardiac stress tests.[17]

Compounds

Thallium(III)

Thallium(III) compounds resemble the corresponding aluminium(III) compounds. They are moderately strong oxidizing agents and are usually unstable, as illustrated by the positive reduction potential for the Tl3+/Tl couple. Some mixed-valence compounds are also known, such as Tl4O3 and TlCl2, which contain both thallium(I) and thallium(III). Thallium(III) oxide, Tl2O3, is a black solid which decomposes above 800 °C, forming the thallium(I) oxide and oxygen.[14]

The simplest possible thallium compound,

β-BiF3 structure rather than that of the lighter group 13 trifluorides, and does not form the TlF
4
complex anion in aqueous solution. The trichloride and tribromide disproportionate just above room temperature to give the monohalides, and thallium triiodide contains the linear triiodide anion (I
3
) and is actually a thallium(I) compound.[19] Thallium(III) sesquichalcogenides do not exist.[20]

Thallium(I)

The

photosensitive and display poor solubility in water.[21] The stability of thallium(I) compounds demonstrates its differences from the rest of the group: a stable oxide, hydroxide, and carbonate are known, as are many chalcogenides.[22]

The double salt Tl
4
(OH)
2
CO
3
has been shown to have hydroxyl-centred triangles of thallium, [Tl
3
(OH)]2+
, as a recurring motif throughout its solid structure.[23]

The metalorganic compound thallium ethoxide (TlOEt, TlOC2H5) is a heavy liquid (ρ 3.49 g·cm−3, m.p. −3 °C),[24] often used as a basic and soluble thallium source in organic and organometallic chemistry.[25]

Organothallium compounds

Organothallium compounds tend to be thermally unstable, in concordance with the trend of decreasing thermal stability down group 13. The chemical reactivity of the Tl–C bond is also the lowest in the group, especially for ionic compounds of the type R2TlX. Thallium forms the stable [Tl(CH3)2]+ ion in aqueous solution; like the isoelectronic Hg(CH3)2 and [Pb(CH3)2]2+, it is linear. 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).[26]

History

Thallium (

emission lines [29] derived from the Greek 'thallos', meaning a green twig.[30]

After the publication of the improved method of flame spectroscopy by Robert Bunsen and Gustav Kirchhoff[31] and the discovery of caesium and rubidium in the years 1859 to 1860, flame spectroscopy became an approved method to determine the composition of minerals and chemical products. Crookes and Lamy both started to use the new method. 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.[32][33] By 1862, Crookes was able to isolate small quantities of the new element and determine the properties of a few compounds.[34] Claude-Auguste Lamy used a spectrometer that was similar to Crookes' to determine the composition of a selenium-containing substance which was deposited during the production of sulfuric acid from pyrite. 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 Frédéric Kuhlmann and this by-product was available in large quantities. Lamy started to isolate the new element from that source.[35] The fact that Lamy was able to work ample quantities of thallium enabled him to determine the properties of several compounds and in addition he prepared a small ingot of metallic thallium which he prepared by remelting thallium he had obtained by electrolysis of thallium salts.[citation needed]

As both scientists discovered thallium independently and a large part of the work, especially the isolation of the metallic thallium was done by Lamy, Crookes tried to secure his own priority on the work. Lamy was awarded a medal at the International Exhibition in London 1862: 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 1862 and 1863. Most of the discussion ended after Crookes was elected Fellow of the Royal Society in June 1863.[36][37]

The dominant use of thallium was the use as poison for rodents. After several accidents the use as poison was banned in the United States by

Presidential Executive Order 11643 in February 1972. In subsequent years several other countries also banned its use.[38]

Occurrence and production

Thallium concentration in the Earth's crust is estimated to be 0.7 mg/kg,[39] mostly in association with potassium-based minerals in clays, soils, and granites. The major source of thallium for practical purposes is the trace amount that is found in copper, lead, zinc, and other heavy-metal-sulfide ores.[40][41]

A close view of a rock crusted with groups of glassy, lustrous, silvery-blue hutchinsonite, in tight clusters of loosely aligned needle-like crystals, among smaller clusters of tiny orange-brown crystals
Crystals of hutchinsonite ((Tl,Pb)2As5S9)

Thallium is found in the minerals

iron pyrite, and thallium is extracted as a by-product of roasting this mineral for the production of sulfuric acid.[9][43]

Thallium can also be obtained from the

ocean floor contain some thallium.[44] In addition, several other thallium minerals, containing 16% to 60% thallium, occur in nature as complexes of sulfides or selenides that primarily contain antimony, arsenic, copper, lead, and silver. These minerals are rare, and have had no commercial importance as sources of thallium.[39] The Allchar deposit in southern North Macedonia was the only area where thallium was actively mined. This deposit still contains an estimated 500 tonnes of thallium, and it is a source for several rare thallium minerals, for example lorándite.[45]

The United States Geological Survey (USGS) estimates that the annual worldwide production of thallium is 10 metric tonnes as a by-product from the smelting of copper, zinc, and lead ores.[39] Thallium is either extracted from the dusts from the smelter flues or from residues such as slag that are collected at the end of the smelting process.[39] 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 precipitated several times from the solution to remove impurities. At the end it is converted to thallium sulfate and the thallium is extracted by electrolysis on platinum or stainless steel plates.[43] The production of thallium decreased by about 33% in the period from 1995 to 2009 – from about 15 metric tonnes 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 if a new application, such as a thallium-containing high-temperature superconductor, becomes practical for widespread use outside of the laboratory.[46]

Applications

Historic uses

The odorless and tasteless

night sweating of tuberculosis patients. This use has been limited due to their narrow therapeutic index, and the development of improved medicines for these conditions.[47][48][49]

Optics

Electronics

A heavily pitted, blackish cylindrical rod, with extensive, crumbling brown-and-white corrosion
A corroded thallium rod

Thallium(I) sulfide's

dissolved oxygen analyzers contain thallium.[9]

High-temperature superconductivity

Research activity with thallium is ongoing to develop high-temperature

electric power generation and transmission. The research in applications started after the discovery of the first thallium barium calcium copper oxide superconductor in 1988.[54] Thallium cuprate superconductors have been discovered that have transition temperatures above 120 K. Some mercury-doped thallium-cuprate superconductors have transition temperatures above 130 K at ambient pressure, nearly as high as the world-record-holding mercury cuprates.[55]

Nuclear medicine

Before the widespread application of

deuterons by the (p,3n) and (d,4n) reactions.[58][59]

Thallium stress test

A thallium stress test is a form of

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 arteries in the body. This produces coronary steal by areas where arteries are maximally dilated. Areas of infarct or ischemic tissue will remain "cold". Pre- and post-stress thallium may indicate areas that will benefit from myocardial revascularization. Redistribution indicates the existence of coronary steal and the presence of ischemic coronary artery disease.[60]

Other uses

A mercury–thallium alloy, which forms a

eutectic at 8.5% thallium, is reported to freeze at −60 °C, some 20 °C below the freezing point of mercury. This alloy is used in thermometers and low-temperature switches.[47] In organic synthesis, thallium(III) salts, as thallium trinitrate or triacetate, are useful reagents for performing different transformations in aromatics, ketones and olefins, among others.[61] Thallium is a constituent of the alloy in the anode plates of magnesium seawater batteries.[9] Soluble thallium salts are added to gold plating baths to increase the speed of plating and to reduce grain size within the gold layer.[62]

A saturated solution of equal parts of thallium(I)

malonate (Tl(C3H3O4)) in water is known as Clerici solution. It is a mobile, odorless liquid which changes from yellowish to colorless upon reducing the concentration of the thallium salts. With a density of 4.25 g/cm3 at 20 °C, Clerici solution is one of the heaviest aqueous solutions known. It was used in the 20th century for measuring the density of minerals by the flotation method, but its use has discontinued due to the high toxicity and corrosiveness of the solution.[63][64]

Thallium iodide is frequently used as an additive in metal-halide lamps, often together with one or two halides of other metals. It allows optimization of the lamp temperature and color rendering,[65][66] and shifts the spectral output to the green region, which is useful for underwater lighting.[67]

Toxicity

Thallium
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H300, H330, H373, H413
P260, P264, P284, P301, P310[68]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
4
0
2

Thallium and its compounds are extremely toxic, with numerous recorded cases of fatal thallium poisoning.

immediately dangerous to life and health.[71]

Contact with skin is dangerous, and adequate ventilation is necessary when melting this metal. Thallium(I) compounds have a high aqueous solubility and are readily absorbed through the skin, and care should be taken to avoid this route of exposure, as

cutaneous absorption can exceed the absorbed dose received by inhalation at the permissible exposure limit (PEL).[72] Exposure by inhalation cannot safely exceed 0.1 mg/m2 in an eight-hour time-weighted average (40-hour work week).[73] The Centers for Disease Control and Prevention (CDC) states, "Thallium is not classifiable as a carcinogen, and it is not suspected to be a carcinogen. It is unknown whether chronic or repeated exposure to thallium increases the risk of reproductive toxicity or developmental toxicity. Chronic high level exposure to thallium through inhalation has been reported to cause nervous system effects, such as numbness of fingers and toes."[74] For a long time thallium compounds were readily available as rat poison. This fact and that it is water-soluble and nearly tasteless led to frequent intoxication caused by accident or criminal intent.[37]

One of the main methods of removing thallium (both radioactive and stable) from humans is to use Prussian blue, a material which absorbs thallium.[75] Up to 20 grams per day of Prussian blue is fed by mouth to the patient, and it passes through their digestive system and comes out in their stool. Hemodialysis and hemoperfusion are also used to remove thallium from the blood serum. At later stages of the treatment, additional potassium is used to mobilize thallium from the tissues.[76][77]

According to the United States Environmental Protection Agency (EPA), artificially-made sources of thallium pollution include gaseous emission of cement factories, 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.[41][78]

See also

Citations

  1. ^ "Standard Atomic Weights: Thallium". CIAAW. 2009.
  2. ISSN 1365-3075
    .
  3. ^ .
  4. .
  5. .
  6. .
  7. .
  8. ^ The Mining and Smelting Magazine Archived 2021-02-24 at the Wayback Machine. Ed. Henry Curwen Salmon. Vol. iv, July–Dec 1963, p. 87.
  9. ^ a b c d e "Chemical fact sheet – Thallium". Spectrum Laboratories. April 2001. Archived from the original on 2008-02-21. Retrieved 2008-02-02.
  10. .
  11. ^ a b c Greenwood and Earnshaw, pp. 222–224
  12. .
  13. ^ a b Greenwood and Earnshaw, pp. 224–7
  14. ^ .
  15. ^
  16. ^ "Manual for reactor produced radioisotopes" (PDF). International Atomic Energy Agency. 2003. Archived (PDF) from the original on 2011-05-21. Retrieved 2010-05-13.
  17. from the original on 2017-02-22. Retrieved 2016-09-26.
  18. .
  19. ^ Greenwood and Earnshaw, p. 239
  20. ^ Greenwood and Earnshaw, p. 254
  21. ^ Greenwood and Earnshaw, p. 241
  22. ^ Greenwood and Earnshaw, pp. 246–7
  23. S2CID 97334707
    .
  24. OCLC 32347397.{{cite book}}: CS1 maint: others (link
    )
  25. .
  26. ^ Greenwood and Earnshaw, pp. 262–4
  27. ^ Liddell, Henry George and Scott, Robert (eds.) "θαλλος Archived 2016-04-15 at the Wayback Machine", in A Greek–English Lexicon, Oxford University Press.
  28. from the original on 2014-07-01. Retrieved 2016-09-26.;
  29. .
  30. ^ "Thallium - Element information, properties and uses | Periodic Table". Royal Society of Chemistry. Retrieved 2 February 2024.
  31. (PDF) from the original on 2020-11-14. Retrieved 2018-04-20.
  32. .
  33. from the original on 2020-03-13. Retrieved 2019-09-12.
  34. .
  35. ^ Lamy, Claude-Auguste (1862). "De l'existencè d'un nouveau métal, le thallium". Comptes Rendus. 54: 1255–1262. Archived from the original on 2016-05-15. Retrieved 2008-11-11.
  36. JSTOR 531576
    .
  37. ^ from the original on 2020-03-07. Retrieved 2016-09-26.
  38. ^ a b Staff of the Nonferrous Metals Division (1972). "Thallium". Minerals yearbook metals, minerals, and fuels. Vol. 1. United States Geological Survey. p. 1358. Archived from the original on 2014-03-22. Retrieved 2010-06-01.
  39. ^ a b c d Guberman, David E. "Mineral Commodity Summaries 2010: Thallium" (PDF). United States Geological Survey. Archived (PDF) from the original on 2010-07-15. Retrieved 2010-05-13.
  40. S2CID 40955658
    .
  41. ^ .
  42. .
  43. ^ from the original on 2017-02-22. Retrieved 2016-09-26.
  44. .
  45. .
  46. ^ Smith, Gerald R. "Mineral commodity summaries 1996: Thallium" (PDF). United States Geological Survey. Archived (PDF) from the original on 2010-05-29. Retrieved 2010-05-13.
  47. ^ .
  48. .
  49. .
  50. .
  51. from the original on 2020-03-11. Retrieved 2016-09-26.
  52. .
  53. .
  54. .
  55. from the original on 2020-03-16. Retrieved 2019-07-01.
  56. from the original on 2017-02-19. Retrieved 2016-09-26.
  57. from the original on 2007-10-12. Retrieved 2006-11-23.
  58. ^ Thallium-201 production Archived 2006-09-13 at the Wayback Machine from Harvard Medical School's Joint Program in Nuclear Medicine.
  59. from the original on 2008-10-11. Retrieved 2010-05-13.
  60. from the original on 2020-03-12. Retrieved 2016-09-26.
  61. .
  62. from the original on 2014-07-01. Retrieved 2016-09-26.
  63. ^ Jahns, R. H. (1939). "Clerici solution for the specific gravity determination of small mineral grains" (PDF). American Mineralogist. 24: 116. Archived (PDF) from the original on 2012-07-24. Retrieved 2009-11-06.
  64. from the original on 2020-03-17. Retrieved 2016-09-26.
  65. .
  66. .
  67. ^ Wilford, John Noble (1987-08-11). "UNDERSEA QUEST FOR GIANT SQUIDS AND RARE SHARKS". The New York Times. Archived from the original on 2016-12-20. Retrieved 2017-02-13.
  68. ^ "Thallium 277932". Sigma-Aldrich. Archived from the original on 2018-10-02. Retrieved 2018-10-02.
  69. ^ "A 15-year-old case yields a timely clue in deadly thallium poisoning". nj. 2011-02-13. Retrieved 2023-02-12.
  70. ^ Jennifer Ouellette (25 December 2018). "Study brings us one step closer to solving 1994 thallium poisoning case". Ars Technica. Archived from the original on 26 December 2018. Retrieved 26 December 2018.
  71. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Thallium (soluble compounds, as Tl)". www.cdc.gov. Archived from the original on 2015-09-24. Retrieved 2015-11-24.
  72. ^ "Surface Contamination - Overview | Occupational Safety and Health Administration". www.osha.gov. Retrieved 2023-02-12.
  73. ^ Chemical Sampling Information | Thallium, soluble compounds (as Tl) Archived 2014-03-22 at the Wayback Machine. Osha.gov. Retrieved on 2013-09-05.
  74. ^ "CDC – The Emergency Response Safety and Health Database: Systemic Agent: THALLIUM – NIOSH". www.cdc.gov. Archived from the original on 2019-11-15. Retrieved 2019-12-11.
  75. from the original on 2020-03-15. Retrieved 2019-07-01.
  76. ^ Prussian blue fact sheet Archived 2013-10-20 at the Wayback Machine. US Centers for Disease Control and Prevention.
  77. PMID 9022660
    .
  78. ^ "Factsheet on: Thallium" (PDF). US Environmental Protection Agency. Archived (PDF) from the original on 2012-01-11. Retrieved 2009-09-15.

General bibliography

External links