Chemical Properties
Silvery-white, lustrous solid with metal
characteristics. Soluble in sulfuric
acid, nitric acid, potassium hydroxide, and potassium
cyanide solutions; insoluble in water. Imparts
garlic-like odor to breath, can be depilatory. It is a ptype
semiconductor and its conductivity is sensitive
to light exposure.
Chemical Properties
Tellurium is a grayish or silvery white, lustrous, crystalline, semimetallic element. It may exist in a hexagonal crystalline form or an amorphous powder. It is found in sulfide ores and is produced as a by-product of copper or bismuth refining.
General Description
Grayish-white, lustrous, brittle, crystalline solid; dark-gray to brown, amorphous powder with metallic characteristics. Used as a coloring agent in chinaware, porcelains, enamels, glass; producing black finish on silverware; semiconductor devices and research; manufacturing special alloys of marked electrical resistance. Improves mechanical properties of lead; powerful carbide stabilizer in cast iron, TELLURIUM(13494-80-9) vapor in "daylight" lamps, vulcanization of rubber. Blasting caps. Semiconductor research.
Hazard
(Metal and compounds as tellurium) Toxic
by inhalation. Halitosis.
Reactivity Profile
TELLURIUM is attacked by chlorine fluoride with incandescence. When tellurium and potassium are warmed in an atmosphere of hydrogen, combination occurs with incandescence [Mellor 11:40. 1946-47]. Burning tellurium produces toxic tellurium oxide gas. Avoid solid sodium, halogens, interhalogens, metals, hexalithium disilicide. Reacts with nitric acid; reacts with concentrated sulfuric acid forming a red solution. Dissolves in potassium hydroxide in the presence of air with formation of deep red solution; combines with halogens. Avoid antimony and chlorine trifluoride; chlorine trifluoride reacts vigorously with tellurium producing flame. Fluorine and tellurium react with incandescence. Lithium silicide attacks tellurium with incandescence. Reaction with zinc is accompanied by incandescence (same potential with cadmium, only hazard is less). A vigorous reaction results when liquid tellurium is poured over solid sodium [EPA, 1998].
Air & Water Reactions
A finely divided suspension of elemental tellurium in air will explode. Insoluble in water.
Health Hazard
Causes central nervous system depression. Moderate skin and eye irritant. Tellurium is capable of doing harm within the body by replacing the essential element sulfur.
Potential Exposure
The primary use of tellurium is in the vulcanization of rubber and as an additive in ferritic steel production. It is also used as a carbide stabilizer in cast iron, a chemical catalyst; a coloring agent in glazes and glass; a thermocoupling material in refrigerating equipment; as an additive to selenium rectifiers; in alloys of lead, copper, steel, and tin for increased resistance to corrosion and stress, workability, machinability, and creep strength; and in certain culture media in bacteriology. Since tellurium is present in silver, copper, lead, and bismuth ores, exposure may occur during purification of these ores.
Fire Hazard
A finely divided suspension of elemental tellurium in air will explode. Burning tellurium produces toxic tellurium oxide gas. Avoid solid sodium, halogens, interhalogens, metals, hexalithium disilicide. Reacts with nitric acid; reacts with concentrated sulfuric acid forming a red solution. Dissolves in potassium hydroxide in the presence of air with formation of deep red solution; combines with halogens. Avoid antimony and chlorine trifluoride; chlorine trifluoride reacts vigorously with tellurium producing flame. Fluorine and tellurium react with incandescence. Lithium silicide attacks tellurium with incandescence. Reaction with zinc is accompanied by incandescence (same potential with cadmium, only hazard is less). A vigorous reaction results when liquid tellurium is poured over solid sodium.
First aid
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. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. 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. When this chemical has been swallowed, get medical attention. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures. Give a slurry of activated charcoal in water to drink. Seek medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit. Medical observation is recommended for 24-48 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 other inhalation therapy.
Shipping
UN3288 Toxic solids, inorganic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required.
Incompatibilities
Finely divided powder or dust may be flammable and explosive. Violent reaction with halogens, interhalogens, zinc and lithium silicide; with incandescence. Incompatible with oxidizers, cadmium; strong bases; chemically active metals; silver bromate; nitric acid.
Description
Tellurium is one of the rarest elements on earth similar to
selenium, and was discovered in Transylvania in 1782 by
Franz-Joseph Muller von Reichenstein. The name derived from
the Latin word for earth. Tellurium is occasionally found
naturally, more often as telluride of gold, calaverite.
Physical properties
Tellurium is a silver-white, brittle crystal with a metallic luster and has semiconductorcharacteristics. It is a metalloid that shares properties with both metals and nonmetals, andit has some properties similar to selenium and sulfur, located just above it in group 16 of theperiodic table.
There are two allotropic forms of tellurium: (1) the crystalline form that has a silvery metallicappearance and a density of 6.24 g/cm3, a melting point of 499.51°C, and a boiling point of988°C; and (2) the amorphous allotrope that is brown in color and has a density of 6.015g/cm3and ranges for the melting and boiling point temperatures similar to the crystalline form.
Isotopes
There are a total of 48 isotopes of tellurium. Eight of these are consideredstable. Three of the stable ones are actually radioactive but have such long half-livesthat they still contribute to the natural abundance of tellurium in the crust of the Earth.The isotope Te-123 (half-life of 6×10+14 years) contributes 0.89% of the total telluriumfound on Earth, Te-128 (half-life of 7.7×10+24 years) contributes 31.74% to the naturalabundance, and Te-130 (half-life of 0.79×10+21 years) contributes 34.08% to the telluriumin the Earth’s crust. The other five stable isotopes and the percentage of theirnatural abundance are as follows: Te-120 = 0.09%, Te-122 = 2.55%, Te-124 = 4.74%,Te-125 = 7.07%, and Te-126 = 18.84%. The other 40 isotopes are all radioactive withshort half-lives.
Origin of Name
The name “tellurium” is derived from the Latin word for Earth, tellus.
Occurrence
Tellurium is the 71st most abundant element on Earth. It makes up a small portion ofigneous rocks and is sometimes found as a free element, but is more often recovered fromseveral ores. Its major ores are sylvanite (AgAuTe4), also known as graphic tellurium, calaverite,sylvanite, and krennerite, all with the same general formula (AuTe2). Other minor ores arenagyagite, black tellurium, hessite, altaite, and coloradoite. In addition, it is recovered fromgold telluride (AuTe2). Significant quantities are also recovered from the anode “slime” of theelectrolytic refining process of copper production.
Characteristics
The pure form of tellurium burns with a blue flame and forms tellurium dioxide (TeO2).It is brittle and is a poor conductor of electricity. It reacts with the halogens of group 17, butnot with many metals. When it reacts with gold, it forms gold telluride. Tellurium is insolublein water but readily reacts with nitric acid to produce tellurous acid. If inhaled, it produces agarlic-like odor on one’s breath.
Purification Methods
Purify it by zone refining and repeated sublimation to an impurity of less than 1 part in 108 (except for surface contamination by TeO2). [Machol & Westrum J Am Chem Soc 80 2950 1958.] Tellurium is volatile at 500o/0.2mm. It has also been purified by electrode deposition [Mathers & Turner Trans Amer Electrochem Soc 54 293 1928].
Flammability and Explosibility
Nonflammable
Environmental Fate
Metals are recalcitrant to degradation; therefore, no biodegradation studies have been performed on tellurium. No aquatic bioaccumulation data exist for tellurium; however, based on its density and low water solubility, it is unlikely to present a concern for bioaccumulation in the water column. No environmental monitoring data are available on the levels of tellurium in sediment or sediment-dwelling organisms. Therefore, it is unclear whether tellurium has the potential to bioaccumulate in this compartment. In humans, tellurium accumulates in the bones. Based on this, it may be assumed that tellurium has the potential to bioaccumulate in vertebrates.
Toxicity evaluation
Tellurium has a low toxicity in its elemental form, but dimethyltelluride
is formed in the body. Tellurium caused a highly
synchronous primary demyelination of peripheral nerves,
related to the inhibition of squalene epoxidase, which blocks
cholesterol synthesis. The sequence of metabolic events in
sciatic nerve following tellurium treatment initially involves
inhibition of the conversion of squalene to 2,3-epoxysqualene,
and this block in the cholesterol biosynthesis pathway results,
either directly or indirectly, in the inhibition of the synthesis of
myelin components and the breakdown of myelin. The efficacy
of garlic as a lipid-lowering agent has been recognized, but the
biochemical mechanisms underlying this action are currently
unknown. It is possible that organic tellurium compounds,
which are found in high concentration in fresh garlic buds, may
contribute to this action by inhibiting squalene epoxidase, the
penultimate enzyme in the synthetic pathway of cholesterol.
Weanling rats fed a diet rich in tellurium develop a demyelinating
polyneuropathy because of inhibition of this enzyme in
peripheral nerves. Chronic exposure to small amounts of
tellurium found in garlic might reduce endogenous cholesterol production through inhibition of hepatic squalene epoxidase
and so reduce cholesterol levels. Tellurium may also contribute
to the characteristic odor of garlic.
