Chemical Properties
silver-grey metal, tarnishing quickly in air
Chemical Properties
Thallium is a soft, bluish-white, heavy, very soft metal insoluble in water and organic solvents. It turns gray on exposure to air.
Definition
ChEBI: A metallic element first identified and named from the brilliant green line in its flame spectrum (from Greek thetaalphalambdalambdaomicronsigma, a green shoot).
Uses
In semi-conductor industry; alloyed with mercury for switches and closures which operate at subzero temperetures. In manufacture of highly refractive optical glass. Has been used in admixture with 97-98% of inert substances as poison for rats and other rodents.
General Description
Bluish-white soft malleable metal or gray granules. Density 11.85 g/cm3. Emits toxic fumes when heated. May be packaged under water.
Hazard
Forms toxic compounds on contact with
moisture; keep from skin contact. Gastrointestinal
damage and peripheral neuropathy.
Reactivity Profile
THALLIUM(7440-28-0) is a reducing agent. Reacts so vigorously with fluorine that the metal becomes incandescent [Mellor 5:421 1946-47].
Air & Water Reactions
Flammable in the form of powder or dust. Insoluble in water.
Potential Exposure
Thallium is usually obtained as a byproduct from the flue dust generated during the roasting of pyrite ores in the smelting and refining of lead and zinc. Thallium has not been produced in the United States since 1984, but is imported for use in the manufacture of electronics, optical lenses, and imitation precious jewels. It also has use in some chemical reactions and medical procedures. Thallium and its compounds are used as a rodenticide and fungicide; in the manufacture of plates and prisms, high-density liquids; as insecticides, catalysts; in certain organic reactions, in phosphor activators; in bromoiodide crystals for lenses, plates, and prisms in infrared optical instruments; in photoelectric cells; in mineralogical analysis; alloyed with mercury in low-temperature thermometers, switches and closures; in high-density liquids; in dyes and pigments; in fire-works; and imitation precious jewelry. It forms a stainless alloy with silver and a corrosion-resistant alloy with lead. Its medicinal use for epilation has been almost discontinued. Highly persistent in the environment. Note: Thallium was used in the past as a rodenticide, it has been banned in the United States due to its toxicity from accidental exposure. In some countries, thallium(I)sulfate(2:1) is still used as a rat poison and ant bait.
First aid
Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Do not use mouth-to-mouth method if victim ingested or in haled the substance; give artificial respiration with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device. Administer oxygen if breathing is difficult. Skin : If this chemical contacts the skin, remove contaminated clothing and immediately flush skin or eyes with running water for at least 20 minutes. For minor skin contact, avoid spreading material on unaffected skin. Keep victim warm and quiet. Effects of exposure to substance may be delayed. The symptoms of acute thallium poisoning (except for gastrointestinal symptoms) may not become manifest until 12 hours to 4 days after exposure. Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. Medical observation is also recommended for at least 24 to 48 hours after breathing overexposure as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a drug or otherinhalation therapy. Cigarette smoking may exacerbate pulmonary injury and should be discouraged for at least 72 hours following exposure. Eyes: If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. Inhalation: If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. Ingestion: Get medical attention. If patient is conscious, give a slurry of activated charcoal in water to drink and induce vomiting. Do not make an unconscious person vomit. Note for qualified medical personnel: For severe poisoning consider BAL (British Anti-Lewisite), dimercaprol, dithiopropanol (C3H8OS2) which has been used to treat toxic symptoms of certain heavy metals poisoning. In the case of thallium it may have some value. Although BAL is reported to have a large margin of safety, caution must be exercised, because toxic effects may be caused by excessive dosage. Most can be prevented by premedication with 1-ephedrine sulfate (CAS: 134-72-5).
Shipping
Thallium: UN3288 Toxic solids, inorganic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required. UN1707 Thallium compounds, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required.
Incompatibilities
Varies. Cold thallium ignites on contact with fluorine. Thallium metal reacts violently with strong acids (such as hydrochloric, sulfuric, and nitric) and strong oxidizers (such as chlorine, bromine, and fluorine). Cold thallium ignites on contact with fluorine. Reacts with other halogens at room temperature.
Description
Thallium was discovered in 1861 by Sir William Crookes (and
independently by Claude-Auguste Lamy a year later) and
occurs in the lithosphere at 0.7 ppm. The name thallium is in
reference to the particularly bright green spectral lines seen in
the spectra resultant from a flame spectroscopy test (from
Greek thallos, meaning a green shoot or twig), the one used in
its discovery. Thallium is a heavy metallic element that exists in
the environment mainly combined with other elements
(primarily oxygen, sulfur, and the halogens) in inorganic
compounds.
Waste Disposal
Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal. Dilute thallium solutions may be disposed of in chemical waste landfills. When possible, thallium should be recovered and returned to the suppliers.
Isotopes
There are a total of 55 isotopes for thallium. All are radioactive with relativelyshort half-lives, and only two are stable. The stable ones are Tl-203, which constitutes29.524% of the element’s existence in the Earth’s crust, and Tl-205, which makes up70.476% of the element’s natural abundance found in the Earth’s crust.
Origin of Name
From the Greek word thallos, meaning “young shoot” or “green twig.”
Named for the green spectral line produced by the light from the element in a spectroscope.
Occurrence
Thallium is the 59th most abundant element found in the Earth’s crust. It is widely distributedover the Earth, but in very low concentrations. It is found in the mineral/ores ofcrooksite (a copper ore; CuThSe), lorandite (TlAsS2), and hutchinsonite (lead ore, PbTl). Itis found mainly in the ores of copper, iron, sulfides, and selenium, but not in its elementalmetallic state. Significant amounts of thallium are recovered from the flue dust of industrialsmokestacks where zinc and lead ores are smelted.
Characteristics
Elemental thallium metal is rare in nature mainly because it oxidizes if exposed to air (oxygen)and water vapor, forming thallium oxide, a black powder. Although some compounds ofthallium are both toxic and carcinogenic, they have some uses in the field of medicine. Somecompounds have the ability to alter their electrical conductivity when exposed to infraredlight.
Production Methods
Thallium sulfide is insoluble in alkaline solution, but soluble in acid,
allowing its separation from group I elements. Thallium
chloride is only slightly soluble in cold water, which permits
its separation from chlorides of cadmium, copper, tellurium,
and zinc.
Thallium metal may be obtained from the compounds in
several ways: by electrolysis of carbonates, sulfates, or
perchlorates; by precipitation of metallic thallium with
zinc; and by reduction of thallous oxalate or chloride. A
number of industrial processes for the recovery of thallium
have been described in the literature. Several of them depend
on the extraction of thallium from flue dust by boiling it in
acidified water.
Health Hazard
Thallium and its soluble compounds arehighly toxic in experimental animals. Theacute toxic symptoms in humans are nausea,vomiting, diarrhea, polyneuritis, convulsion,and coma. Ingestion of 0.5 g can be fatalto humans. Severe chronic toxicity can leadto kidney and liver damage, deafness, andloss of vision. Other signs of toxicity fromchronic exposure include reddening of theskin, abdominal pain, polyneuritis, loss ofhair, pain in legs, and occasionally cataracts.Ingestion of thallium salts in children hascaused neurological abnormalities, mentalretardation, and psychoses.
Hoffman (2000) reviewed thallium poisoningin women during pregnancy and cited acase that began in the first trimester of pregnancyresulting in fetal demise. John Peter andViraraghavan (2005) have reviewed toxicityof thallium and public health risk and discussedenvironmental concerns and variousremoval technologies from aquatic system.
.
Carcinogenicity
Female mice treated orally or
cutaneously with high doses of thallium showed a degenerative
process in the genital tract similar to that found in
castrated animals or after uterine denervation. The diagnoses
were papilloma, precancerous lesions, and cancer. The control
mice did not develop cancer.
Environmental Fate
Metallic thallium (TI) is bluish white or gray; it is very soft
and malleable. The element can exist in the environment
mainly combined with other elements (primarily oxygen,
sulfur, and the halogens) in inorganic compounds. Thallium
exists in monovalent (thallous, thallium (I), Tl+1) and
trivalent (thallic, thallium (III), Tl+3) states. Monovalent
thallium ions also are more stable in aqueous solution, but
trivalent thallium (Tl+3) can be stabilized by complexing
agents. Monovalent thallium is similar to potassium (K+) in
ionic radius and electrical charge, which contribute to its
toxic nature.
Compounds of thallium, however, are generally soluble in
water and the element is found primarily as the monovalent
ion (Tl+). Thallium tends to adsorb to soils and sediments,
and to bioconcentrate in aquatic plants, invertebrates, and
fish. Terrestrial plants can also absorb thallium from soil. Thallium is quite stable in the environment because it is
neither transformed nor biodegraded. However, thallium may
be bioconcentrated by organisms from water. The US Environmental
Protection Agency has identified several National
Priorities List sites polluted by thallium.
Toxicity evaluation
Several mechanisms have been postulated for the toxic action
of thallium; however, the exact mechanism or mechanisms of
toxicity are unknown. Thallium’s mechanism of toxicity is
related to its ability to interfere with potassium ion functions
because both obtain similar ionic radii. In addition, there is
evidence that thallium interferes with energy production at
essential steps in glycolysis, the Kreb’s cycle, and oxidative
phosphorylation that adversely affects protein synthesis. Other
effects include inhibition of sodium–potassium–adenosine
triphosphatase and binding to sulfhydryl groups.
