Tellurium (pronounced /tɨˈlʊəriəm, tɛˈlʊəriəm/ te-LOOR-ee-əm)
is a chemical element that has the symbol Te and
atomic number 52. A brittle, mildly toxic,
silver-white metalloid which looks similar to tin,
tellurium is chemically related to selenium
and sulfur.
Tellurium was discovered in 1782 by Franz-Joseph Müller von
Reichenstein in a mineral containing gold
and tellurium. Martin Heinrich Klaproth
named the new element in 1798 after the Latin word for "earth", tellus.
Although several gold deposits contain tellurium minerals, the main commercial
source for tellurium is as a by-product of copper
and lead
production. Tellurium is primarily used in alloys,
foremost in steel and copper to improve machinability. Applications in solar panels and as a semiconductor
material also consume a considerable fraction of tellurium production.
Detailed
description
Tellurium has no
biological function, although fungi can incorporate it in place of sulfur and
selenium into amino acids such as telluro-cysteine and telluro-methionine. In
humans, tellurium is partly metabolized into dimethyl
telluride, (CH3)2Te,
a gas with a garlic-like odor which is exhaled in the
breath of victims of tellurium toxicity or exposure.
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History
Tellurium (Latin tellus meaning "earth") was
discovered in the 18th century in a gold ore from the mines in Zlatna, near what is now Sibiu, Transylvania. This ore was known as
"Faczebajer weißes blättriges Golderz" (white leafy gold ore from
Faczebaja) or antimonalischer Goldkies (antimonic gold pyrite), and,
according to Anton von Rupprecht, was Spießglaskönig (argent
molybdique), containing native antimony.[2] In 1782 Franz-Joseph Müller von Reichenstein, who was then serving as the
Hungarian chief inspector of mines in Transylvania, concluded that the ore did
not contain antimony, but that it was bismuth sulfide.[3] The following year, he reported that
this was erroneous and that the ore contained mostly gold and an unknown metal
very similar to antimony. After a thorough investigation which lasted for three
years and consisted of more than fifty tests, Müller determined the specific gravity of the mineral and noted the radish-like odor of the white smoke which passed off
when the new metal was heated, the red color which the metal imparts to sulfuric acid, and the black precipitate which this
solution gives when diluted with water. Nevertheless, he was not able to
identify this metal and gave it the names aurum paradoxium and metallum
problematicum, as it did not show the properties predicted for the expected
antimony.[4][5][6]
In 1789, another
Hungarian scientist, Pál Kitaibel, also discovered the element
independently in an ore from Deutsch-Pilsen which had been regarded as
argentiferous molybdenite, but later he gave the credit to
Müller. In 1798, it was named by Martin
Heinrich Klaproth
who earlier isolated it from the mineral calaverite.[5][6][7]
Tellurium was
used as a chemical bonder in the making of the outer shell of the first atomic bomb. The 1960s brought growth in thermoelectric
applications for tellurium, as well as its use in free-machining steel, which became the dominant use.[citation needed]
Characteristics
Physical properties
When crystalline, tellurium is silvery-white and when
it is in pure state it has a metallic luster. It is a brittle and easily
pulverized metalloid. Amorphous tellurium is found by precipitating it from a
solution of tellurous or telluric acid (Te(OH)6).[8] Tellurium is a p-type semiconductor that shows a greater electrical
conductivity in certain directions which depends on atomic alignment; the conductivity increases
slightly when exposed to light (photoconductivity).[9] When in its molten state, tellurium
is corrosive to copper, iron and stainless steel.
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