World tellurium market. World Tellurium Market Examples of Problem Solving
Hardly anyone will believe the story of the sea captain, who is, moreover, a professional circus wrestler, a famous metallurgist and a consultant doctor of a surgical clinic. In the world of chemical elements, such a variety of professions is a very common phenomenon, and the expression of Kozma Prutkov is inapplicable to them: "A specialist is like a gumboil: his completeness is one-sided." Let's remember (even before talking about the main object of our story) iron in cars and iron in blood, iron is a magnetic field concentrator and iron - component part ocher ... True, the "professional training" of the elements sometimes took much more time than the preparation of an average yogi. So element number 52, which we are about to tell, has been used for many years only in order to demonstrate what it really is, this element, named after our planet: "tellurium" - from tellus, which in Latin means "Earth ".
This element was discovered almost two centuries ago. In 1782, mining inspector Franz Josef Müller (later Baron von Reichenstein) investigated the gold-bearing ore found in Semigorye, on the territory of what was then Austria-Hungary. It turned out to be so difficult to decipher the composition of the ore that it was named Aurum problematicum - "doubtful gold". It was from this "gold" that Muller singled out a new metal, but there was no complete confidence that it was really new. (Subsequently, it turned out that Mueller was wrong about something else: the element he discovered was new, but it can only be attributed to the number of metals with a great stretch.)
To dispel doubts, Müller turned to a prominent specialist, the Swedish mineralogist and analytical chemist Bergman.
Unfortunately, the scientist died before he could finish the analysis of the sent substance - in those years, analytical methods were already quite accurate, but the analysis took a lot of time.
Other scientists tried to study the element discovered by Müller, but only 16 years after its discovery, Martin Heinrich Klaproth, one of the greatest chemists of that time, irrefutably proved that this element was actually new, and suggested the name "tellurium" for it.
As always, following the discovery of the element, the search for its applications began. Apparently, proceeding from the old, even from the times of iatrochemistry, the principle - the world is a pharmacy, the Frenchman Fournier tried to treat some serious diseases with tellurium, in particular leprosy. But without success - only many years later tellurium was able to provide doctors with some "minor services". More precisely, not tellurium itself, but the salts of telluric acid K 2 TeO 3 and Na 2 TeO 3, which began to be used in microbiology as dyes that impart a certain color to the bacteria under study. So, with the help of tellurium compounds, the diphtheria bacillus is reliably isolated from the mass of bacteria. If not in treatment, then at least in diagnostics, element No. 52 was useful to doctors.
But sometimes this element, and to an even greater extent some of its compounds, add hassle to doctors. Tellurium Fairly toxic. In our country, the maximum permissible concentration of tellurium in the air is 0.01 mg / m3. Of the tellurium compounds, the most dangerous is hydrogen telluride H 2 Te, a colorless poisonous gas with an unpleasant odor. The latter is quite natural: tellurium is an analogue of sulfur, which means that H 2 Te should be like hydrogen sulfide. It irritates the bronchi, has a harmful effect on the nervous system.
These unpleasant properties did not prevent tellurium from entering technology, acquiring many "professions".
Metallurgists are interested in tellurium because even its small additions to lead greatly increase the strength and chemical resistance of this important metal... Lead doped with tellurium is used in the cable and chemical industries. Thus, the service life of apparatus for sulfuric acid production, coated from the inside with a lead-tellurium alloy (up to 0.5% Te), is twice as long as that of the same apparatus, simply lined with lead. The addition of tellurium to copper and steel facilitates their machining.
In glass production, tellurium is used to give glass a brown color and a higher refractive index. In the rubber industry, as an analogue of sulfur, it is sometimes used for vulcanizing rubbers.
Tellurium - semiconductor
However, these industries were not responsible for the jump in prices and demand for element No. 52. This jump took place in the early 60s of our century. Tellurium is a typical semiconductor, and the semiconductor is technologically advanced. Unlike germanium and silicon, it melts relatively easily (melting point 449.8 ° C) and evaporates (boils at a temperature just below 1000 ° C). Hence, it is easy to obtain thin semiconductor films from it, which are of particular interest in modern microelectronics.
However, pure tellurium as a semiconductor is used to a limited extent - for the manufacture of field-effect transistors of some types and in devices that measure the intensity of gamma radiation. Moreover, an impurity of tellurium is deliberately introduced into gallium arsenide (the third most important semiconductor after silicon and germanium) in order to create an electronic type of conductivity in it.
The area of application of some tellurides - tellurium compounds with metals is much broader. Bismuth tellurides Bi 2 Te 3 and antimony Sb 2 Te 3 have become the most important materials for thermoelectric generators. To explain why this happened, we will make a small digression into the field of physics and history.
A century and a half ago (in 1821), the German physicist Seebeck discovered that in a closed electrical circuit consisting of different materials, the contacts between which are at different temperatures, an electromotive force is created (it is called thermo-EMF). After 12 years, the Swiss Peltier discovered an effect opposite to the Seebeck effect: when an electric current flows through a circuit made up of different materials, in the places of contacts, in addition to the usual Joule heat, a certain amount of heat is released or absorbed (depending on the direction of the current).
For about 100 years, these discoveries remained a "thing in itself", curious facts, nothing more. And it would not be an exaggeration to say that a new life for both of these effects began after Academician A.F. Ioffe and his co-workers developed the theory of using semiconductor materials for the manufacture of thermoelements. And soon this theory was embodied in real thermoelectric generators and thermoelectric refrigerators for various purposes.
In particular, thermoelectric generators, in which bismuth, lead and antimony tellurides are used, provide energy to artificial earth satellites, navigation and meteorological installations, and cathodic protection devices for main pipelines. The same materials help maintain the desired temperature in many electronic and microelectronic devices.
V last years another one is of great interest chemical compound tellurium with semiconducting properties - cadmium telluride CdTe. This material is used for the manufacture of solar panels, lasers, photoconductors, counters. radioactive radiation... Cadmium telluride is also famous for the fact that it is one of the few semiconductors in which the Hahn effect is noticeably manifested.
The essence of the latter is that the very introduction of a small plate of the corresponding semiconductor into a sufficiently strong electric field leads to the generation of high-frequency radio emission. The Hahn effect has already found applications in radar technology.
In conclusion, we can say that quantitatively the main "profession" of tellurium is alloying of lead and other metals. Qualitatively, the main thing, of course, is the work of tellurium and tellurides as semiconductors.
Useful admixture
In the periodic table, the place of tellurium is in the main subgroup of group VI, next to sulfur and selenium. These three elements are similar in chemical properties and often accompany each other in nature. But the share of sulfur in the earth's crust is 0.03%, selenium is only 10-5%, tellurium is still an order of magnitude less - 10-6%. Naturally, tellurium, like selenium, is most often found in natural sulfur compounds - as an impurity. It happens, however (remember the mineral in which tellurium was discovered) that it comes into contact with gold, silver, copper and other elements. More than 110 deposits of forty tellurium minerals have been discovered on our planet. But it is always mined at the same time either with selenium, or with gold, or with other metals.
Copper-nickel tellurium-bearing ores of Pechenga and Monchegorsk, tellurium-bearing lead-zinc ores of Altai and a number of other deposits are known in Russia.
Tellurium is isolated from copper ore at the stage of purification of blister copper by electrolysis. A sediment - sludge - flows to the bottom of the electrolyzer. This is a very expensive intermediate product. Here, for illustration, the composition of the sludge from one of the Canadian plants: 49.8% copper, 1.976% gold, 10.52% silver, 28.42% selenium and 3.83% tellurium. All these most valuable components of the sludge must be separated, and there are several ways for this. Here is one of them.
The sludge is melted in a furnace and air is passed through the melt. Metals, except for gold and silver, are oxidized and pass into slag. Selenium and tellurium are also oxidized, but into volatile oxides, which are captured in special devices (scrubbers), then dissolved and converted into acids - selenium H 2 SeO3 and telluride H 2 TeO3. If sulfur dioxide S0 2 is passed through this solution, reactions will occur
H 2 Se0 3 + 2S0 2 + H 2 0 → Se ↓ + 2H 2 S0 4.
H2Te03 + 2S02 + H20 → Te ↓ + 2H 2 S0 4.
Tellurium and selenium fall out at the same time, which is highly undesirable - we need them separately. Therefore, the process conditions are selected in such a way that, in accordance with the laws of chemical thermodynamics, predominantly selenium is reduced first. This is facilitated by the selection of the optimal concentration of hydrochloric acid added to the solution.
Then tellurium is besieged. The fallen gray powder, of course, contains a certain amount of selenium and, in addition, sulfur, lead, copper, sodium, silicon, aluminum, iron, tin, antimony, bismuth, silver, magnesium, gold, arsenic, chlorine. Tellurium has to be cleaned of all these elements first. chemical methods, then distillation or zone melting. Naturally, tellurium is extracted in different ways from different ores.
Tellurium is harmful
Tellurium is used more and more widely and, therefore, the number of those working with it is increasing. In the first part of the story about element No. 52, we have already mentioned the toxicity of tellurium and its compounds. Let's talk about this in more detail - precisely because more and more people have to work with tellurium. Here is a quote from a dissertation on tellurium as an industrial poison: white rats, which were injected with tellurium aerosol, "showed anxiety, sneezed, rubbed their faces, became lethargic and drowsy." Tellurium has a similar effect on humans.
And myself tellurium and its compounds can bring misfortunes of different calibers. They, for example, cause baldness, affect the composition of the blood, and can block various enzyme systems. Symptoms of chronic poisoning with elemental tellurium - nausea, drowsiness, emaciation; exhaled air takes on a nasty garlic smell of alkyl tellurides.
In acute poisoning with tellurium, serum with glucose is administered intravenously and sometimes even morphine. As a prophylactic agent they use ascorbic acid... But the main prevention is the reliable sealing of the apparatus, the automation of processes in which tellurium and its compounds are involved.
Element number 52 is very useful and therefore deserves attention. But working with him requires caution, clarity and, again, focused attention.
APPEARANCE OF TELLURIUM. Crystalline tellurium is most similar to antimony. Its color is silvery white. Crystals are hexagonal, the atoms in them form spiral chains and are linked by covalent bonds with the nearest neighbors. Therefore, elemental tellurium can be considered an inorganic polymer. Crystalline tellurium is characterized by a metallic luster, although by its complex of chemical properties it can rather be attributed to non-metals. Tellurium is fragile and can be easily turned into powder. The question of the existence of an amorphous modification of tellurium has not been unambiguously resolved. When tellurium is reduced from telluric or telluric acids, a precipitate is formed, but it is still not clear whether these particles are truly amorphous or just very small crystals.
TWO-COLOR ANHYDRID. As befits an analogue of sulfur, tellurium exhibits valencies 2-, 4+, and 6+, and much less often 2+. Tellurium monoxide TeO can exist only in gaseous form and is easily oxidized to TeO 2. It is a white, non-hygroscopic, completely stable crystalline substance that melts without decomposition at 733 ° C; it has a polymeric structure.
Tellurium dioxide almost does not dissolve in water - only one part of TeO 2 per 1.5 million parts of water passes into the solution and a solution of weak tellurous acid H 2 TeO 3 of negligible concentration is formed. The acidic properties of telluric acid are also weakly expressed.
H 6 TeO 6. This formula (and not Н 2 TeO 4 was assigned to it after the salts of the composition Ag 6 Te0 6 and Hg 3 Te0 6, which are readily soluble in water, were obtained. modifications - yellow and gray: α-TeOs and β-TeOs. Gray telluric anhydride is very stable: even when heated, acids and concentrated alkalis do not act on it. It is purified from the yellow variety by boiling the mixture in concentrated potassium hydroxide.
SECOND EXCEPTION. When creating the periodic table, Mendeleev put tellurium and the neighboring iodine (as well as argon and potassium) in groups VI and VII not in accordance with, but in spite of their atomic weights. Indeed, the atomic mass of tellurium is 127.61, and that of iodine is 126.91 This means that iodine should have stood not behind tellurium, but in front of it. Mendeleev, however, did not doubt the right
the validity of his reasoning, since he believed that the atomic weights of these elements were not determined accurately enough. Mendeleev's close friend, the Czech chemist Boguslav Brauner, carefully checked the atomic weights of tellurium and iodine, but his data coincided with the previous ones. The legitimacy of the exceptions confirming the rule was established only when the basis of the periodic table was formed not by atomic weights, but by the charges of nuclei, when the isotopic composition of both elements became known. Tellurium, unlike iodine, is dominated by heavy isotopes.
By the way, about isotones. Now there are 22 known isotopes of element number 52. Eight of them - with mass numbers 120, 122, 123, 124, 125, 126, 128 and 130 - are stable. The last two isotopes are the most common: 31.79 and 34.48%, respectively.
MINERALS TELLURIUM. Although tellurium is much less abundant on earth than selenium, there are more minerals known for element 52 than its counterpart. By their composition, tellurium minerals are twofold: either tellurides, or the oxidation products of tellurides in the earth's crust. Among the first are calaverite AuTe 2 and krennerite (Au, Ag) Te2, which are among the few natural gold compounds. Natural tellurides of bismuth, lead, and mercury are also known. Native tellurium is very rarely found in nature. Even before the discovery of this element, it was sometimes found in sulfide ores, but could not be correctly identified. Tellurium minerals have no practical value - all industrial tellurium is a by-product of processing other metal ores.
Tellurium
TELLURIUM[te], -a; m.[from lat. tellus (telluris) - earth] Chemical element (Te), a brittle crystalline metal of a silvery-gray color (used in the manufacture of brown dyes, semiconductor materials).
◁ Telluric, th, th.
tellurium(lat. Tellurium), chemical element of group VI of the periodic system. Named from lat. tellus, genus. n. telluris - Earth. Silver-gray, very fragile crystals with a metallic luster, density 6.25 g / cm 3, t pl 450 ° C; semiconductor. It is stable in air, at high temperatures it burns with the formation of TeO 2 dioxide. It occurs naturally in the form of tellurides and as native tellurium; often accompanies sulfur and selenium; extracted from copper electrolysis waste. Alloy component (copper, lead, cast iron); dye for glass and ceramics (brown). Many tellurium compounds are semiconductor materials, infrared receivers.
TELLURIUMTellurium (Latin Tellurium from Latin tellus - Earth), Te (read "tellurium"), a chemical element with atomic number 52, atomic mass 127.60. Natural tellurium consists of eight stable isotopes: 120 Te (content 0.089% by mass), 122 Te (2.46%), 123 Te (2.46%), 124 Te (4.74%), 125 Te (7, 03%), 126 Te (18.72%), 128 Te (31.75%) and 130 Te (34.27%). The radius of the atom is 0.17 nm. Ion radii: Te 2– - 0.207 nm (coordination number 6), Te 4+ - 0.066 nm (3), 0.08 nm (4), 0.111 nm (6), Te 6+ - 0.057 (4) and 0.070 nm (6). Sequential ionization energies: 9.009, 18.6, 28.0, 37.42 and 58.8 eV. Located in group VIA, in the 5th period of the periodic table of elements. Chalcogen (cm. HALCOGENS),
non-metal. Configuration of the outer electron layer 5 s 2
p 4
... Oxidation states: –2, +2, +4, +6 (valencies II, IV and VI). Pauling electronegativity (cm. POLING Linus) 2,10.
Tellurium is a fragile silvery-white substance with a metallic luster.
Discovery history
It was first discovered in 1782 in the gold-bearing ores of Transylvania by the mining inspector F.I.Müller, who took it for a new metal. In 1798 M.G. Klaprot (cm. KLAPROT Martin Heinrich) isolated tellurium and determined its most important properties.
Being in nature
The content in the earth's crust is 1 · 10 -6% by weight. About 100 tellurium minerals are known. The most important of them: altaite PbTe, sylvanite AgAuTe 4, calaverite AuTe 2, tetradymite Bi 2 Te 2 S. There are oxygen compounds of tellurium, for example TeO 2 - telluric ocher. Native tellurium is also found together with selenium (cm. SELENIUM) and gray (cm. SULFUR)(Japanese tellurium sulfur contains 0.17% Te and 0.06% Se).
An important source of tellurium is copper and lead ores.
Receiving
Primary source - copper electrolytic refining sludge (cm. COPPER) and lead. (cm. LEAD) The sludge is calcined, the tellurium remains in the cinder, which is washed hydrochloric acid... Tellurium is isolated from the obtained hydrochloric acid solution by passing sulfur dioxide SO 2 through it.
Sulfuric acid is added to separate selenium and tellurium. In this case, tellurium dioxide TeO 2 precipitates, and selenous acid remains in solution.
To isolate Te from the slimes, they are sintered with soda, followed by leaching. Those passes into an alkaline solution, from which, upon neutralization, it precipitates in the form of TeO 2:
Na 2 TeO 3 + 2HC = TeO 2 Ї + 2NaCl.
Tellurium is reduced from TeO 2 oxide with coal.
To purify tellurium from S and Se, use its ability under the action of a reducing agent (Al) in alkaline environment to convert to soluble disodium ditelluride Na 2 Te 2:
6Te + 2Al + 8NaOH = 3Na 2 Te 2 + 2Na.
To precipitate tellurium, air or oxygen is passed through the solution:
2Na 2 Te 2 + 2H 2 O + O 2 = 4Te + 4NaOH.
To obtain tellurium of special purity, it is chlorinated:
Te + 2Cl 2 = TeCl 4.
The resulting tetrachloride is purified by distillation or rectification. Then the tetrachloride is hydrolyzed with water:
TeCl 4 + 2H 2 O = TeO 2 Ї + 4HCl,
and the formed TeO 2 is reduced with hydrogen:
TeO 2 + 4H 2 = Te + 2H 2 O.
Physical and chemical properties
Thallur is a fragile silvery-white substance with a metallic luster. The crystal lattice is hexagonal, a= 0.44566 nm, c= 0.59268 nm. The structure consists of parallel spiral chains. Density 6.247 g / cm 3. Melting point 449.8 ° C, boiling point 990 ° C. In thin layers, red-brown in the light, in pairs - golden-yellow.
P-type semiconductor. The band gap is 0.32 eV. Electrical conductivity increases with lighting.
During precipitation, amorphous tellurium is released from solutions, the density is 5.9 g / cm 3. At 4.2 GPa and 25 ° C, a modification with a b-Sn (Te-II) type structure is formed. At 6.3 GPa, the Te-III modification with a rhombohedral structure was obtained. Te-II and Te-III exhibit the properties of metals.
Stable in air at room temperature, even in a finely dispersed state. When heated in air, it burns with a bluish-green flame with the formation of TeO 2 dioxide. Standard half-reaction potential:
TeO 3 2– + 3H 2 O + 4e = Te + 6OH -: 0.56V.
At 100–160 ° C it is oxidized by water:
Te + 2H 2 O = TeO 2 + 2H 2
When boiled in alkaline solutions, tellurium disproportionates to the formation of telluride and tellurite:
8Te + 6KOH = 2K 2 Te + K 2 TeO 3 + 3H 2 O.
Te does not react with hydrochloric and dilute sulfuric acids. Concentrated H 2 SO 4 dissolves Te, the resulting Te 4 2+ cations color the solution red. Diluted HNO 3 oxidizes Te to tellurous acid H 2 TeO 3:
3Te + 4HNO 3 + H 2 O = 3H 2 TeO 3 + 4NO.
Strong oxidants (HClO 3, KMnO 4) oxidize Te to weak telluric acid H 6 TeO 6:
Te + HClO 3 + 3H 2 O = HCl + H 6 TeO 6.
With halogens (cm. HALOGENS)(except for fluorine) forms tetrahalides. Fluorine oxidizes Te to TeF6 hexafluoride.
Hydrogen telluride H 2 Te is a colorless poisonous gas with an unpleasant odor formed during hydrolysis of tellurides.
Tellurium compounds (+2) are unstable and prone to disproportionation:
2TeCl 2 = TeCl 4 + Te.
Application
The main application of Te and its compounds is in semiconductor technology. Te additives in cast iron (cm. CAST IRON) and steel (cm. STEEL), lead (cm. LEAD) or copper increases their mechanical and chemical resistance. Those and its compounds are used in the production of catalysts, special glasses, insecticides, herbicides.
Physiological action
Tellurium and its volatile compounds are toxic. Ingestion causes nausea, bronchitis, pneumonia. MPC in air 0.01 mg / m 3, in water 0.01 mg / l. In case of poisoning, tellurium is excreted from the body in the form of disgusting-smelling organo-tellurium compounds.
Trace amounts of Te are always found in living organisms, and its biological role has not been clarified.
encyclopedic Dictionary. 2009 .
Synonyms:See what "tellurium" is in other dictionaries:
- (new lat., from lat. Tellus, Telluris earth, goddess of the earth). A simple body, similar to sulfur in its properties of compounds, was discovered in gold ore in 1872 and belongs to metals and metalloids. Dictionary of foreign words included in the Russian language. ... ... Dictionary of foreign words of the Russian language
M l, Te. Trig. Gab. prisms, up to needle-like. Sp. owls. along the prism. Agr .: fine-grained and columnar. Tin white. Bl. metal. TV. 2 2.5. Ud. v. 6.3. In hydrotherm. veins with native Au, tellurides Au and Ag, sulfides. Geological ... ... Geological encyclopedia
- (lat. Tellurium) Those, chemical element of group VI of the periodic system, atomic number 52, atomic mass 127.60. Name from lat. tellus genus. n. telluris Earth. Silvery gray, very fragile crystals with a metallic luster, density 6.24 ... ... Big Encyclopedic Dictionary
Tellurium, chalcogen, sylvan Dictionary of Russian synonyms. tellurium n., number of synonyms: 8 mineral (5627) ... Synonym dictionary
TELLURIUM- TELLURIUM, Tellurium, chem. The symbol Te ranks 52nd in the periodic table. Homologue of sulfur and selenium (group VІ). At. weight 127.5. T. amorphous black powder or brittle pieces of silver white, with a metallic sheen; beats weight 6,24, t ° ... ... Big medical encyclopedia
- (Tellurium), Te, chemical element of group VI of the periodic table, atomic number 52, atomic mass 127.60; refers to chalcogenes; non-metal. Highlighted by the Hungarian scientist F. Müller von Reichenstein in 1782 ... Modern encyclopedia
- (symbol Te), a silvery white chemical element, discovered in 1782. It occurs naturally in combination with gold in sylvanite. Its main source is a by-product of the electrolytic refining of copper. The shiny, fragile element is used in ... Scientific and technical encyclopedic dictionary
Tellurium, tellurium, pl. no, husband. (from Latin tellus earth) (chem.). Chemical element, crystalline substance, silvery white. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary
Tellurium is a non-metal that has a metallic luster. Its color is silvery white. This element is very rare and scattered. It was discovered by the mining inspector Franz Josef Müller in 1782. Tellurium is extracted from polymetallic ore. This substance is contained in the form of compounds in hydrothermal gold deposits and others.
Thallium is a brittle material that acquires plastic properties during heating. The density value of this non-metal is 6.25 g / cm3. Tellium begins to melt when the temperature reaches 450 ° C, and boils at 990 ° C. The material has the properties of a diamagnetic and at 18 ° C the value of the specific magnetic susceptibility is -0.31.10-6.
Tellurium is a p-type semiconductor when ambient conditions are normal or when the material is heated to a boil. When a non-metal is cooled, at a transition around -100 ° C, it changes its properties and acquires n-type conductivity. The forbidden zone in width is 0.34 eV. The transition temperature decreases depending on the purity of the substance.
Thallium is used as an alloying additive in the production of lead. It improves strength and chemical resistance. Lead-tellurium alloy is used in cable and chemical industries. Tellurium is also alloyed with copper and steel. This improves their machining.
Tellurium is also used in glass production. Glass, thanks to such an impurity, acquires a brown color, and its refractive index increases. In the rubber industry, tellurium is used in the rubber vulcanization process.
Significant demand for tellurium is due to its semiconducting properties. It is considered both a typical and a technological semiconductor. This substance is used in microelectronics. It produces a thin film that melts at lower temperatures than many metals.
In its pure form, tellurium, in the form of a semiconductor, is rarely used due to its limited supply in the bowels of the Earth. In most cases, it is used in the manufacture of transistors and devices that are designed to measure the intensity of gamma radiation.
Most often, the industry uses not pure non-metal, but its compounds with metals, which are called tellurides. With their use, important parts of thermoelectric generators are produced.
Sale of non-ferrous metals in Moscow -.
Tellurium Tellurium (lat. Tellurium) is a chemical element with atomic number 52 in the periodic table and atomic weight 127.60; denoted by the symbol Te, belongs to the family of metalloids. In nature, it occurs in the form of eight stable isotopes with mass numbers 120, 128, 130, of which the most common are 128Te and 130Te. Of the artificially obtained radioactive isotopes, 127Te and 129Te are widely used as labeled atoms.
From history It was first found in 1782 in the gold-bearing ores of Transylvania by the mining inspector Franz Josef Müller (later Baron von Reichenstein), on the territory of Austria-Hungary. In 1798 Martin Heinrich Klaproth isolated tellurium and determined its most important properties. The first systematic studies of the chemistry of tellurium were carried out in the 30s. 19th century I. Ya. Berzelius.
"Aurum paradoxum" is a paradoxical gold, as tellurium was called, after it was discovered by Reichenstein at the end of the 18th century in combination with silver and a yellow metal in the mineral sylvanite. An unexpected phenomenon seemed the fact that gold, usually always found in a native state, was found in conjunction with tellurium. That is why, having ascribed properties similar to the yellow metal, it was called the paradoxical yellow metal.
Origin of the name Later (1798), when M. Klaproth investigated the new substance in more detail, he named it tellurium in honor of the Earth, the bearer of chemical "miracles" (from the Latin word "tellus" - earth). This name is used by chemists of all countries.
Being in nature The content in the earth's crust is 1 · 10-6% by weight. Metallic tellurium can be found only in the laboratory, but its compounds can be found around us much more often than you might think. About 100 tellurium minerals are known. The most important of them: altaite PbTe, sylvanite AgAuTe 4, calaverite AuTe 2, tetradymite Bi 2 Te 2 S, krennsrite AuTe 2, petcite AgAuTe 2. There are oxygen compounds of tellurium, for example TeO2 telluric ocher. Native tellurium is also found together with selenium and sulfur (Japanese tellurium sulfur contains 0.17% Te and 0.06% Se).
Peltier Module Many people are familiar with Peltier thermoelectric modules, which are used in portable refrigerators, thermoelectric generators and sometimes for extreme cooling of computers. The main semiconductor material in such modules is bismuth telluride. It is currently the most widely used semiconductor material. If you look at the thermoelectric module from the side, you can see rows of small "cubes".
Physical properties Tellurium is silvery-white in color with a metallic luster, is fragile, and becomes ductile when heated. Crystallizes in a hexagonal system. Tellurium is a semiconductor. Under normal conditions and up to the melting point, pure Tellurium has p-type conductivity. With a decrease in temperature in the range (100 ° C) - (-80 ° C), a transition occurs: the conductivity of Tellurium becomes n-type. The temperature of this transition depends on the purity of the sample, and it is the lower, the cleaner the sample. Density = 6.24 g / cm ³ Melting point = 450 ° C Boiling point = 990 ° C Heat of fusion = 17.91 kJ / mol Heat of vaporization = 49.8 kJ / mol Molar heat capacity = 25.8 J / (K mol) Molar volume = 20.5 cm³ / mol
Tellurium is a non-metal. In compounds tellurium exhibits oxidation states: -2, +4, +6 (valence II, IV, VI). Tellurium is chemically less active than sulfur and oxygen. Tellurium is stable in air, but at high temperatures it burns with the formation of TeO 2 dioxide. Te interacts with halogens in the cold. When heated, it reacts with many metals to give tellurides. Let's dissolve in alkalis. Under the action of nitric acid, Te is converted into telluric acid, and under the action of aqua regia or 30% hydrogen peroxide, into telluric acid. Chemical properties 128 Te))))) e = 52, p = 52, n = e 8e 8e 8e 6e
Physiological action When heated, Tellurium interacts with hydrogen to form hydrogen telluride - H 2 Te, a colorless poisonous gas with a pungent, unpleasant odor. Tellurium and its volatile compounds are toxic. Ingestion causes nausea, bronchitis, pneumonia. The maximum permissible concentration in air varies for various compounds 0.0070.01 mg / m³, in water 0.0010.01 mg / l.
Obtaining Main source of copper and lead electrolytic refining sludge. The sludge is calcined, the tellurium remains in the cinder, which is washed with hydrochloric acid. Tellurium is isolated from the obtained hydrochloric acid solution by passing sulfur dioxide SO 2 through it. Sulfuric acid is added to separate selenium and tellurium. This precipitates tellurium dioxide TeO 2, and H 2 SeO 3 remains in solution. Tellurium is reduced from TeO 2 oxide with coal. To purify tellurium from sulfur and selenium, use is made of its ability, under the action of a reducing agent (Al) in an alkaline medium, to transform into soluble disodium ditelluride Na 2 Te 2: 6Te + 2Al + 8NaOH = 3Na 2 Te 2 + 2Na. To precipitate tellurium, air or oxygen is passed through the solution: 2Na 2 Te 2 + 2H 2 O + O 2 = 4Te + 4NaOH. To obtain tellurium of special purity, it is chlorinated with Te + 2Cl 2 = TeCl 4. The resulting tetrachloride is purified by distillation or rectification. Then the tetrachloride is hydrolyzed with water: TeCl 4 + 2H 2 O = TeO 2 + 4HCl, and the formed TeO 2 is reduced with hydrogen: TeO 2 + 4H 2 = Te + 2H 2 O.
Tellurium exists in two modifications - crystalline and amorphous.
Crystalline tellurium is obtained by cooling tellurium vapor, and amorphous tellurium is obtained by reducing telluric acid with sulfur dioxide or another similar reagent:
Amorphous tellurium is a fine black powder that transforms into metallic tellurium when heated. The density of amorphous tellurium is 5.85-5.1 g / cm3.
For crystalline tellurium, two polymorphic species are known: α-Te and β-Te. The α → β transition occurs at 354 ° С. Crystalline tellurium has a white-silver color. Its density is 6.25 g / cm2. The hardness of crystalline tellurium is 2.3; at ordinary temperatures it is brittle, easily crushed into powder, and at higher temperatures it becomes so plastic that it can be pressed.
The melting point of tellurium is 438-452 ° C, and the boiling point is 1390 ° C. Tellurium is characterized by high vapor pressure, which, depending on the temperature, is expressed in the following numbers:
Tellurium has a semiconducting character of conductivity. The electrical resistance of polycrystalline tellurium at 0 ° C is 0.102 ohm * cm. With increasing temperature, the electrical resistivity of tellurium decreases:
In contrast to selenium, the electrical resistance of tellurium is not very sensitive to light. However, at low temperatures, the effect of lighting is still felt; so, at -180 ° C, the electrical resistance of tellurium under the influence of illumination decreases by 70%.
Chemical properties
In terms of its chemical properties, tellurium is similar to selenium, but has a more pronounced metallic character. At room temperature, compact tellurium is resistant to air and oxygen; when heated, it oxidizes and burns with a blue flame with a green border, forming TeO2.
In a dispersed state and in the presence of moisture, tellurium is oxidized at ordinary temperatures. Tellurium at room temperature reacts with halogens and forms chemically stronger halides (TeCl4; TeBr4) than selenium.
Tellurium does not directly combine with hydrogen under normal conditions, but upon heating it forms H2Te. When heated with many metals, tellurium forms tellurides: K2Te, Ag2Te, MgTe, Al2Te, etc.
Metallic tellurium reacts with water at 100-160 ° C, and freshly precipitated (amorphous tellurium) - at room temperature:
Te + 2Н2О → TeO2 + 2Н2.
Tellurium does not dissolve in CS2; dissolves very slowly in dilute HCl. In concentrated and diluted HNO3, tellurium is oxidized to form H2TeO3:
3Те + 4HNО3 + H2O = 3Н2ТеО3 + 4NO.
Tellurous acid is readily decomposed by sulfur dioxide with the release of tellurium:
H2TeO3 + 2SO2 + H2O → Te + 2H2SO4.
This reaction is used to obtain pure tellurium.
Tellurium is an almost constant companion of heavy non-ferrous metals in sulfides (iron and copper pyrite, lead luster), but it also occurs in the form of minerals sylvanite, calaverite (Au, Ag) Te2, etc.
The main source of production of industrial tellurium is the waste of processing sulfide ores of copper and lead - dust, in which tellurium is present in the form of TeO2, obtained during the roasting of sulfide ores; as well as anode sludge obtained during the electrolytic refining of copper and lead.
17.03.2020
The creation of volumetric models today is relevant not only for animation, but also for technical purposes. Also, often using 3D modeling, they create interior models ...
16.03.2020
Like the currently popular laminate flooring, modern parquet boards are quite easy to install. Place it on the floor of the owner's living or technical room ...
16.03.2020
Registration on the portal is almost instantaneous, you can create an account by entering the address Email or use your own account in one of 20 ...
16.03.2020
It doesn't matter what gadget you have, play through mobile version you can even use the oldest smartphone. To start playing, you first have to register ...
16.03.2020
Among floor coverings, carpet is especially interesting because it combines excellent insulating qualities, luxurious appearance and simple styling technology ...
16.03.2020
First, you need to understand how industrial chillers work. Such a device resembles an ordinary refrigerator, a special pump pumps out liquid, cooling ...
15.03.2020
When planning repair work in your home, you first need to decide on the range of action. Depending on the condition of the premises, the area will depend ...
14.03.2020
Owners can use drywall panels in various cases. Especially often drywall is used for wall cladding ....
13.03.2020
V modern world it is difficult to imagine at least one high-profile festive event without the use of various pyrotechnics, which is represented, in simple words, by colorful ...
13.03.2020
Paving slabs- it is used to create a hard surface of streets, design of pedestrian zones, roads, etc. Can be formed from various materials. They...