Tin is one of the few metals known to man since prehistoric times. Tin and copper were discovered before iron, and their alloy, bronze, is, apparently, the very first "artificial" material, the first material prepared by man.
The results of archaeological excavations suggest that as far back as five millennia BC, people were able to smelt tin itself. It is known that the ancient Egyptians brought tin for the production of bronze from Persia.
Under the name "trapu" this metal is described in ancient Indian literature. The Latin name for tin, stannum, comes from the Sanskrit "hundred", which means "solid".
The mention of tin is also found in Homer. Almost ten centuries before the new era, the Phoenicians delivered tin ore from the British Isles, then called the Cassiterids. Hence the name cassiterite, the most important of the tin minerals; composition of its SnO 2 . Another important mineral is stannin, or tin pyrite, Cu 2 FeSnS 4 . The remaining 14 minerals of element No. 50 are much rarer and have no industrial value. By the way, our ancestors had richer tin ores than we do. It was possible to smelt metal directly from ores located on the surface of the Earth and enriched during the natural processes of weathering and washing out. Nowadays, such ores no longer exist. In modern conditions, the process of obtaining tin is multistage and laborious. The ores from which tin is now smelted are complex in composition: in addition to element No. 50 (in the form of oxide or sulfide), they usually contain silicon, iron, lead, copper, zinc, arsenic, aluminum, calcium, tungsten and other elements. Present-day tin ores rarely contain more than 1% Sn, and placers contain even less: 0.01...0.02% Sn. This means that to obtain a kilogram of tin, it is necessary to mine and process at least a centner of ore.
How is tin obtained from ores
The production of element No. 50 from ores and placers always begins with enrichment. Methods of enrichment of tin ores are quite diverse. In particular, the gravitational method is used, based on the difference in the density of the main and accompanying minerals. At the same time, we must not forget that the accompanying ones are far from always an empty breed. Often they contain valuable metals, such as tungsten, titanium, lanthanides. In such cases, they try to extract all valuable components from tin ore.
The composition of the resulting tin concentrate depends on the raw materials, and also on how this concentrate was obtained. The tin content in it ranges from 40 to 70%. The concentrate is sent to kilns (at 600...700°C), where relatively volatile impurities of arsenic and sulfur are removed from it. And most of the iron, antimony, bismuth and some other metals are leached with hydrochloric acid after firing. After this is done, it remains to separate the tin from oxygen and silicon. Therefore, the last stage in the production of black tin is smelting with coal and fluxes in reverberatory or electric furnaces. From a physicochemical point of view, this process is similar to a blast furnace: carbon “takes away” oxygen from tin, and fluxes turn silicon dioxide into a light slag compared to metal.
There are still quite a lot of impurities in rough tin: 5 ... 8%. To obtain metal of high-quality grades (96.5 ... 99.9% Sn), fire or less often electrolytic refining is used. And the tin necessary for the semiconductor industry with a purity of almost six nines - 99.99985% Sn - is obtained mainly by zone melting.
Another source
In order to get a kilogram of tin, it is not necessary to process a centner of ore. You can do otherwise: "peel" 2000 old cans.
Only half a gram of tin per can. But multiplied by the scale of production, these half-grams turn into tens of tons ... The share of "secondary" tin in the industry of the capitalist countries is about a third of the total production. There are about a hundred industrial tin recovery plants in operation in our country.
How is tin removed from tinplate? It is almost impossible to do this mechanically, so they use the difference in the chemical properties of iron and tin. Most often, tin is treated with gaseous chlorine. Iron in the absence of moisture does not react with it. Tin combines with chlorine very easily. A smoking liquid is formed - tin chloride SnCl 4, which is used in the chemical and textile industries or sent to an electrolyzer to get metallic tin from it. And again the “circle” will begin: steel sheets will be covered with this tin, they will receive tinplate. It will be made into jars, the jars will be filled with food and sealed. Then they will open them, eat canned food, throw away the cans. And then they (not all, unfortunately) will again get to the factories of "secondary" tin.
Other elements make a cycle in nature with the participation of plants, microorganisms, etc. The tin cycle is the work of human hands.
Tin in alloys
About half of the world's tin production goes to tin cans. The other half - in metallurgy, to obtain various alloys. We will not talk in detail about the most famous of the tin alloys - bronze, referring readers to an article about copper - another important component of bronzes. This is all the more justified because there are tinless bronzes, but there are no “copperless” ones. One of the main reasons for the creation of tinless bronzes is the scarcity of element No. 50. Nevertheless, tin-containing bronze is still an important material for both mechanical engineering and art.
The technique also needs other tin alloys. True, they are almost never used as structural materials: they are not strong enough and too expensive. But they have other properties that make it possible to solve important technical problems at a relatively low cost of material.
Most often, tin alloys are used as antifriction materials or solders. The first allow you to save machines and mechanisms, reducing friction losses; the second connect metal parts.
Of all antifriction alloys, tin babbits, which contain up to 90% tin, have the best properties. Soft and low-melting lead-tin solders well wet the surface of most metals, have high ductility and fatigue resistance. However, the scope of their application is limited due to the insufficient mechanical strength of the solders themselves.
Tin is also part of the typographic alloy hart. Finally, tin-based alloys are very necessary for electrical engineering. The most important material for electric capacitors is steel; this is almost pure tin, turned into thin sheets (the share of other metals in staniol does not exceed 5%).
Incidentally, many tin alloys are true chemical compounds of element #50 with other metals. Fusing, tin interacts with calcium, magnesium, zirconium, titanium, and many rare earth elements. The resulting compounds are characterized by a rather high refractoriness. Thus, zirconium stannide Zr 3 Sn 2 melts only at 1985°C. And not only the refractoriness of zirconium is "to blame" here, but also the nature of the alloy, the chemical bond between the substances that form it. Or another example. Magnesium cannot be classified as a refractory metal, 651 ° C is far from a record melting point. Tin melts at an even lower temperature of 232°C. And their alloy - the Mg 2 Sn compound - has a melting point of 778 ° C.
The fact that element No. 50 forms quite numerous alloys of this kind forces us to critically consider the statement that only 7% of the tin produced in the world is consumed in the form of chemical compounds (“Brief Chemical Encyclopedia”, vol. 3, p. 739). Apparently, we are talking here only about compounds with non-metals.
Compounds with non-metals
Of these substances, chlorides are the most important. Tin tetrachloride SnCl 4 dissolves iodine, phosphorus, sulfur, and many organic substances. Therefore, it is mainly used as a very specific solvent. Tin dichloride SnCl 2 is used as a mordant in dyeing and as a reducing agent in the synthesis of organic dyes. Another compound of element No. 50, sodium stannate Na 2 SnO 3, has the same functions in textile production. In addition, with its help, silk is weighed down.
Industry also uses tin oxides to a limited extent. SnO is used to produce ruby glass, and SnO 2 is used to produce white glaze. Golden-yellow crystals of tin disulfide SnS 2 are often called gold leaf, which “golden” wood, gypsum. This is, so to speak, the most "anti-modern" use of tin compounds. What about the most modern?
If we keep in mind only tin compounds, then this is the use of barium stannate BaSnO 3 in radio engineering as an excellent dielectric. And one of the isotopes of tin, 119 Sn, played a significant role in the study of the Mössbauer effect - a phenomenon due to which a new research method was created - gamma-resonance spectroscopy. And this is not the only case when the ancient metal served modern science.
On the example of gray tin - one of the modifications of element No. 50 - a relationship was revealed between the properties and the chemical nature of the semiconductor material. And this, apparently, is the only thing for which gray tin can be remembered with a kind word: it brought more harm, the more good. We will come back to this variety of element #50 after talking about another large and important group of tin compounds.
About organotin
There are a great many organoelement compounds containing tin. The first of them was received in 1852.
At first, substances of this class were obtained in only one way - in the exchange reaction between inorganic tin compounds and Grignard reagents. Here is an example of such a reaction:
SnCl 4 + 4RMgX → SnR 4 + 4MgXCl
(R here is a hydrocarbon radical, X is a halogen).
Compounds of composition SnR 4 have not found wide practical application. But it is from them that other organotin substances are obtained, the benefits of which are undoubted.
For the first time, interest in organotin arose during the First World War. Almost all organic tin compounds obtained by that time were toxic. These compounds were not used as toxic substances; their toxicity to insects, molds, and harmful microbes was used later. On the basis of triphenyltin acetate (C 6 H 5) 3 SnOOCCH 3, an effective drug was created to combat fungal diseases of potatoes and sugar beets. This drug turned out to have another useful property: it stimulated the growth and development of plants.
To combat fungi that develop in the apparatus of the pulp and paper industry, another substance is used - tributyltin hydroxide (C 4 H 9) 3 SnOH. This greatly improves the performance of the hardware.
Dibutyltin dilaurinate (C 4 H 9) 2 Sn (OCOC 11 H 23) 2 has many "professions". It is used in veterinary practice as a remedy for helminths (worms). The same substance is widely used in the chemical industry as a stabilizer for polyvinyl chloride and other polymeric materials and as a catalyst. The reaction rate of formation of urethanes (monomers of polyurethane rubbers) in the presence of such a catalyst increases by 37 thousand times.
Effective insecticides have been created on the basis of organotin compounds; organotin glasses reliably protect against x-ray radiation, polymeric lead and organotin paints cover the underwater parts of ships so that mollusks do not grow on them.
These are all compounds of tetravalent tin. The limited scope of the article does not allow talking about many other useful substances of this class.
Organic compounds of divalent tin, on the contrary, are few in number and have so far found almost no practical application.
About gray tin
In the frosty winter of 1916, a batch of tin was sent by rail from the Far East to the European part of Russia. But it was not silvery-white ingots that arrived at the site, but mostly fine gray powder.
Four years earlier, a catastrophe had occurred with the expedition of polar explorer Robert Scott. The expedition, heading to the South Pole, was left without fuel: it leaked out of iron vessels through the seams soldered with tin.
Around the same years, the famous Russian chemist V.V. Markovnikov was asked by the commissariat to explain what was happening with the tin-plated teapots that were supplied to the Russian army. The teapot, which was brought to the laboratory as a case study, was covered with gray spots and growths that crumbled even with light tapping by hand. The analysis showed that both dust and growths consisted only of tin, without any impurities.
What happened to the metal in all these cases?
Like many other elements, tin has several allotropic modifications, several states. (The word “allotropy” is translated from Greek as “another property”, “another turn.”) At normal positive temperatures, tin looks so that no one can doubt that it belongs to the class of metals.
White metal, ductile, malleable. Crystals of white tin (it is also called beta-tin) are tetragonal. The length of the edges of the elementary crystal lattice is 5.82 and 3.18 Å. But below 13.2°C, the "normal" state of tin is different. As soon as this temperature threshold is reached, a rearrangement begins in the crystal structure of the tin ingot. White tin is converted into powdered gray or alpha tin, and the lower the temperature, the greater the rate of this transformation. It reaches its maximum at minus 39°C.
Gray tin crystals of a cubic configuration; the dimensions of their elementary cells are larger - the edge length is 6.49 Å. Therefore, the density of gray tin is noticeably less than that of white: 5.76 and 7.3 g/cm3, respectively.
The result of white tin turning gray is sometimes referred to as "tin plague". Stains and growths on army teapots, wagons with tin dust, seams that have become permeable to liquid are the consequences of this “disease”.
Why don't stories like this happen now? Only for one reason: they learned to “treat” the tin plague. Its physico-chemical nature has been clarified, it has been established how certain additives affect the metal's susceptibility to the "plague". It turned out that aluminum and zinc contribute to this process, while bismuth, lead and antimony, on the contrary, counteract it.
In addition to white and gray tin, another allotropic modification of element No. 50 was found - gamma tin, which is stable at temperatures above 161°C. A distinctive feature of such tin is fragility. Like all metals, tin becomes more ductile with increasing temperature, but only at temperatures below 161°C. Then it completely loses its plasticity, turning into gamma tin, and becomes so brittle that it can be crushed into powder.
More about scarcity
Often articles about the elements end with the author's reasoning about the future of his "hero". As a rule, it is drawn in pink light. The author of the article about tin is deprived of this opportunity: the future of tin, a metal that is undoubtedly the most useful, is unclear. It is not clear for one reason only.
A few years ago, the US Bureau of Mines published calculations that indicated that the proven reserves of element 50 would last the world at most 35 years. True, after that several new deposits were found, including the largest in Europe, located on the territory of the Polish People's Republic. Nevertheless, the shortage of tin continues to worry specialists.
Therefore, finishing the story about element No. 50, we want to once again remind you of the need to save and protect tin.
The lack of this metal worried even the classics of literature. Remember Andersen? “Twenty-four soldiers were exactly the same, and the twenty-fifth soldier was one-legged. It was cast last, and there was a little lack of tin.” Now the tin is missing not a little. No wonder even bipedal tin soldiers have become a rarity - plastic ones are more common. But with all due respect to polymers, they can not always replace tin.
isotopes
Tin is one of the most “multi-isotopic” elements: natural tin consists of ten isotopes with mass numbers 112, 114...120, 122 and 124. The most common of them is 120 Sn, it accounts for about 33% of all terrestrial tin. Almost 100 times smaller than tin-115, the rarest isotope of element #50. Another 15 isotopes of tin with mass numbers 108...111, 113, 121, 123, 125...132 were obtained artificially. The lifetime of these isotopes is far from the same. So, tin-123 has a half-life of 136 days, and tin-132 is only 2.2 minutes.
Why is bronze called bronze?
The word "bronze" sounds almost the same in many European languages. Its origin is associated with the name of a small Italian port on the Adriatic Sea - Brindisi. It was through this port that bronze was delivered to Europe in the old days, and in ancient Rome this alloy was called "es brindisi" - copper from Brindisi.
In honor of the inventor
The Latin word frictio means friction. Hence the name of anti-friction materials, that is, materials "against friction". They wear out a little, are soft and ductile. Their main application is the manufacture of bearing shells. The first antifriction alloy based on tin and lead was proposed in 1839 by the engineer Babbitt. Hence the name of a large and very important group of antifriction alloys - babbits.
Tin for canning
The method of long-term preservation of food products by canning in tin-plated tin cans was first proposed by the French chef F. Appert in 1809.
From the bottom of the ocean
In 1976, an unusual enterprise began to operate, which is abbreviated as REP. It is deciphered as follows: exploration and production enterprise. It is located mainly on ships. Beyond the Arctic Circle, in the Laptev Sea, in the area of Vankina Bay, REP extracts tin-bearing sand from the seabed. Here, on board one of the ships, there is an enrichment plant.
World production
According to American data, the world production of tin in 1975 was 174...180 thousand tons.
Tin is a chemical element with the symbol Sn (from Latin: stannum) and atomic number 50. It is a post-transition metal in group 14 of the periodic table of the elements. Tin is obtained mainly from the mineral tin ore containing tin dioxide SnO2. Tin shares chemical similarities with its two group 14 neighbors, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most common element and has the most stable isotopes on the periodic table (with 10 stable isotopes), thanks to its "magic" number of protons. Tin has two main allotropes: at room temperature, the stable allotrope is β-tin, a silvery-white, malleable metal, but at low temperatures, tin turns into a less dense gray α-tin, which has a diamond cubic structure. Metal tin is not easily oxidized in the air. The first alloy to be used on a large scale was bronze, made from tin and copper, beginning around 3000 BC. e. After 600 BC. e. produced pure metallic tin. An alloy of tin and lead, in which tin is 85-90%, usually composed of copper, antimony, and lead, was used to make utensils from the Bronze Age until the 20th century. Nowadays, tin is used in many alloys, most commonly in soft tin/lead alloys, which typically contain 60% or more tin. Another common use for tin is as a corrosion resistant coating on steel. Inorganic tin compounds are rather non-toxic. Due to its low toxicity, tinned metal has been used to package food with tin cans, which are, in fact, mostly made of steel or aluminum. However, overexposure to tin can cause problems with the metabolism of essential micronutrients such as copper and zinc, and some organotin compounds can be nearly as toxic as cyanide.
Characteristics
Physical
Tin is a soft, malleable, ductile and highly crystalline silver-white metal. When a plate of tin is bent, a crackling sound known as "tin crack" can be heard from the twinning of the crystals. Tin melts at a low temperature, around 232 °C, the lowest in group 14. The melting point further decreases to 177.3 °C for 11 nm particles. β-tin (metal form, or white tin, BCT structure), which is stabilized at room temperature and above, malleable. In contrast, α-tin (the non-metallic form, or gray tin), which is stabilized up to 13.2 °C, is brittle. α-tin has a cubic crystal structure similar to diamond, silicon or germanium. α-tin has no metallic properties at all, because its atoms form a covalent structure in which electrons cannot move freely. It is a dull gray powdery material that does not have any wide application beyond a few specialized semiconductor applications. These two allotropes, α-tin and β-tin, are better known as tin gray and tin white, respectively. Two more allotropes, γ and σ, exist at temperatures above 161 °C and pressures above several gigapascals. Under cold conditions, β-tin spontaneously transforms into α-tin. This phenomenon is known as "tin plague". Although the α-β transformation temperature is nominally 13.2 °C and impurities (eg Al, Zn, etc.) are below the transition temperature below 0 °C and, with the addition of Sb or Bi, the transformation may not occur at all, increasing the durability of the tin. Commercial grades of tin (99.8%) resist transformation due to the inhibitory effect of small amounts of bismuth, antimony, lead and silver present as impurities. Alloying elements such as copper, antimony, bismuth, cadmium, silver increase the hardness of the substance. Tin quite easily forms hard, brittle intermetallic phases, which are often undesirable. Tin does not form many solid solutions in other metals in general, and several elements have appreciable solid solubility in tin. Simple eutectic systems, however, are observed with bismuth, gallium, lead, thallium, and zinc. Tin becomes a superconductor below 3.72 K and is one of the first superconductors to be studied; The Meissner effect, one of the characteristic features of superconductors, was first observed in superconducting tin crystals.
Chemical properties
Tin resists corrosion from water, but can be attacked by acids and alkalis. Tin can be highly polished and used as a protective coating for other metals. A protective oxide (passive) layer prevents further oxidation, the same that forms on pewter and other pewter alloys. Tin acts as a catalyst when oxygen is in solution and helps speed up chemical corrosion.
isotopes
Tin has ten stable isotopes with atomic masses 112, 114 through 120, 122 and 124, the largest number of any element. The most common of these are 120Sn (nearly a third of all tin), 118Sn and 116Sn, while the least common are 115Sn. Isotopes with even mass numbers have no nuclear spin, while isotopes with odd numbers have spin +1/2. Tin, with three common isotopes 116Sn, 118Sn and 120Sn, is one of the easiest elements to detect and analyze using NMR spectroscopy. This large number of stable isotopes is thought to be a direct result of the atomic number 50, the "magic number" in nuclear physics. Tin also occurs in 29 unstable isotopes, spanning all other atomic masses from 99 to 137. Except for 126Sn, with a half-life of 230,000 years, all radioisotopes have a half-life of less than a year. Radioactive 100Sn, discovered in 1994, and 132Sn are among the few nuclides with a "double magic" nucleus: despite being unstable, with very uneven proton-neutron ratios, they represent endpoints beyond which stability drops off rapidly. Another 30 metastable isomers were characteristic of isotopes between 111 and 131, the most stable being 121mSn with a half-life of 43.9 years. The relative differences in the abundance of stable tin isotopes can be explained by their different modes of formation in stellar nucleosynthesis. 116Sn through 120Sn inclusive are formed in the s-process (slow neutrons) in most stars and, therefore, they are the most common isotopes, while 122Sn and 124Sn are not only formed in the R-process (fast neutrons) in supernovae and less frequently. (Isotopes 117Sn through 120Sn also benefit from the r-process.) Finally, the rarest proton-rich isotopes, 112Sn, 114Sn, and 115Sn, cannot be produced in significant quantities in the s- and r-processes and are considered among the p- nuclei, the origin of which is not fully understood. Some of the proposed mechanisms for their formation include proton capture as well as photocleavage, although 115Sn can also be partially produced in the s-process, both at once, and as a "daughter" of long-lived 115In.
Etymology
The English word tin (tin) is common to the Germanic languages and can be traced back to the reconstructed Proto-Germanic *tin-om; cognates include German Zinn, Swedish tenn and Dutch tin. The word does not occur in other branches of the Indo-European languages, with the exception of a borrowing from Germanic (for example, the Irish word tinne comes from the English tin). The Latin name stannum originally meant an alloy of silver and lead, and in the 4th century BC. e. it came to mean "tin" - the earlier Latin word for it was plumbum quandum, or "white lead". The word stannum seems to have come from an earlier stāgnum (same substance), the origin of the Romanesque and Celtic designation for tin. The origin of stannum/stāgnum is unknown; it may be pre-Indo-European. Conversely, according to Meyer's Collegiate Dictionary, stannum is thought to be derived from the Cornish stean and is proof that Cornwall was the main source of tin in the first centuries AD.
Story
The extraction and use of tin began in the Bronze Age, around 3000 BC. e., when it was noted that copper objects formed from polymetallic ores with different metal content have different physical properties. The earliest bronze objects contained less than 2% tin or arsenic and are therefore thought to be the result of unintentional alloying by tracing the metal content of the copper ore. Adding a second metal to copper increases its strength, lowers its melting point, and improves the casting process by creating a more fluid melt that is denser and less spongy when cooled. This allowed the creation of much more complex forms of closed bronze objects. Arsenic bronze objects appeared primarily in the Middle East, where arsenic is often found in association with copper ore, however, the health risks associated with the use of such objects soon became clear, and the search for sources of much less hazardous tin ores began early. bronze age. This created a demand for the rare metallic tin and formed a trade network linking distant sources of tin to the markets of Bronze Age cultures. Cassiterite, or tin ore (SnO2), tin oxide, was most likely the original source of tin in antiquity. Other forms of tin ores are the less common sulfides, such as stannite, which require a more aggressive smelting process. Cassiterite often accumulates in alluvial channels as placer deposits because it is heavier, harder, and more chemically resistant than granite. Cassiterite is usually black or generally dark in color, and its deposits are easily visible along river banks. Alluvial (placer) deposits can be easily collected and separated by methods similar to gold panning.
Compounds and chemistry
In the vast majority, tin has an oxidation state of II or IV.
inorganic compounds
Halogen compounds are known for both oxidation states. For SN(IV), all four halides are well known: SnF4, SnCl4, SnBr4, and SnI4. The three heaviest elements are volatile molecular compounds, while tetrafluoride is polymeric. All four halides for Sn(II) are also known: SnF2, SnCl2, SnBr2, and SnI2. All are polymeric solids. Of these eight compounds, only iodides are colored. Tin(II) chloride (also known as stannous chloride) is the most important commercial tin halide. Chlorine reacts with tin metal to create SnCl4 while the reaction of hydrochloric acid and tin produces SnCl2 and hydrogenated gas. In addition, SnCl4 and Sn combine with tin chloride through a process called co-proportionation: SnCl4 + CH → 2 Sncl2 Tin can form many oxides, sulfides, and other chalcogenide derivatives. SnO2 dioxide (cassiterite) is formed when tin is heated in the presence of air. SnO2 is amphoteric in nature, which means that it dissolves in both acidic and basic solutions. Stannates with the structure Sn(OH)6]2, such as K2, are also known, although the free stannic acid H2[CH(one)6] is unknown. Tin sulfides exist in both +2 and +4 oxidation states: tin(II) sulfide and tin(IV) sulfide (mosaic gold).
hydrides
Stannan (SnH4), with tin in the +4 oxidation state, is unstable. Organotin hydrides, however, are well known, eg tributyline hydride (Sn(C4H9)3H). These compounds release transient tributyltin tin radicals, which are rare examples of tin(III) compounds.
Organotin compounds
Organotin compounds, sometimes referred to as stannanes, are chemical compounds with tin–carbon bonds. Of the tin compounds, organic derivatives are the most useful commercially. Some organotin compounds are highly toxic and are used as biocides. The first known organotin compound was diethyltindiodide (C2H5)2SnI2) discovered by Edward Frankland in 1849. Most organotin compounds are colorless liquids or solids that are resistant to air and water. They adopt a tetrahedral geometry. Tetraalkyl and tetraaryltin compounds can be prepared using Grignard's reagents:
4 + 4 RMgBr → R
Mixed halide alkyls, which are more common and of greater commercial value than tetraorganic derivatives, are made by redistributing reactions:
4Sn → 2SnCl2R2
Divalent organotin compounds are rare, although more common than divalent organogermanium and organosilicon compounds. The great stabilization that Sn(II) has is due to the "inert pair effect". Organotin(II) compounds include both stannylenes (formula: R2Sn, as seen for singlet carbenes) and distannylenes (R4Sn2), which are roughly equivalent to alkenes. Both classes show unusual reactions.
emergence
Tin is formed in a long s-process in low- and medium-mass stars (with masses from 0.6 to 10 times that of the Sun) and, finally, in the beta decay of heavy isotopes of indium. Tin is the most abundant element 49 in the Earth's crust, at 2 ppm compared to 75 mg/L for zinc, 50 mg/L for copper, and 14 ppm for lead. Tin does not occur as a native element, but must be extracted from various ores. Cassiterite (SnO2) is the only commercially important source of tin, although small amounts of tin are recovered from complex sulfides such as stannite, cypindrite, frankeite, canfieldite, and thilite. Tin minerals are almost always associated with granitic rock, usually at levels of 1% tin oxide. Due to the high specific gravity of tin dioxide, about 80% of the mined tin comes from secondary deposits found from primary deposits. Tin is often recovered from pellets washed downstream in the past and deposited in valleys or the sea. The most economical methods of extracting tin are by dredging, hydraulics or open pits. Most of the world's tin is produced from alluvial deposits, which may contain as little as 0.015% tin. World reserves of tin mines (tons, 2011)
Indonesia 800000
Brazil 590000
Bolivia 400000
Russia 350000
Australia 180000
Thailand 170000
Others 180000
Total 4800000
China 1500000
Malaysia 250000
Approximately 253,000 tons of tin were mined in 2011, mainly in China (110,000 tons), Indonesia (51,000 tons), Peru (34,600 tons), Bolivia (20,700 tons) and Brazil (12,000 tons). Estimates of tin production have historically varied depending on the dynamics of economic feasibility and the development of mining technologies, but it is estimated that at current consumption rates and technologies, tin mining will end on Earth in 40 years. Lester Brown suggested that tin could run out within 20 years based on an extremely conservative extrapolation of 2% growth per year. Economically recoverable tin reserves: Mln. tons per year
Secondary, or scrap, tin is also an important source of this metal. Recovery of tin through secondary production or processing of scrap tin is growing rapidly. While the United States has not mined tin since 1993, nor smelted tin since 1989, it was the largest secondary producer of tin, recycling almost 14,000 tons in 2006. New deposits are located in the south of Mongolia, and in 2009 new deposits of tin were discovered in Colombia by Seminole Group Colombia CI, SAS.
Production
Tin is obtained by carbothermal reduction of oxide ore using carbon or coke. Reverberatory furnaces and electric furnaces can be used.
Price and exchange
Tin is unique among other mineral commodities due to complex agreements between producing and consuming countries dating back to 1921. Earlier agreements tended to be somewhat informal and sporadic and led to the "First International Tin Agreement" in 1956, the first of a permanent series of agreements that effectively ceased in 1985. Through this series of agreements, the International Tin Council (ITC) has had a significant impact on tin prices. The MCO supported the price of tin during periods of low prices by buying tin for its buffer stock and was able to keep the price down during periods of high prices by selling tin from this stock. This was an anti-market approach designed to ensure that tin would flow to the consuming countries and make a profit for the producing countries. However, the buffer stock was not large enough, and for most of those 29 years, tin prices rose, sometimes dramatically, especially from 1973 to 1980, when rampant inflation plagued many of the world's economies. In the late 1970s and early 1980s, the US government's tin holdings were in an aggressive selling mode, in part to take advantage of historically high tin prices. The sharp recession of 1981-82 proved to be quite harsh for the tin industry. Tin consumption has dropped sharply. The MSO was able to avoid a really sharp cut by buying fast for its buffer stock; this activity has required MSOs to borrow extensively from banks and steel trading firms to augment their resources. MCO continued to borrow funds until the end of 1985, when it reached its credit limit. Immediately after that came the big “tin crisis”, and then tin was excluded from trading on the London Metal Exchange for a period of three years, the MCO soon collapsed, and the price of tin, already in a free market, fell sharply to $ 4 per pound (453 g) and remained at this level until the 1990s. The price increased again by 2010 with a rebound in consumption following the 2008-09 World Economic Crisis, accompanying a resumption and continued growth in consumption in the developing world. The London Metal Exchange (LME) is the main trading floor for tin. Other tin markets are the Kuala Lumpur Tin Market (KLTM) and the Indonesian Tin Exchange (INATIN).
Applications
In 2006, about half of all tin produced was used in solder. The rest of the applications were divided between tin plating, tin chemicals, brass and bronze alloys, and niche uses.
Solder
Tin has long been used in alloys with lead as solder, ranging from 5 to 70%. Tin forms a eutectic mixture with lead in the proportion of 63% tin and 37% lead. Such solders are used to connect pipes or electrical circuits. On July 1, 2006, the Waste Electrical and Electronic Equipment Directive (WEEE Directive) and the Restriction of Hazardous Substances Directive came into force. The lead content in such alloys has decreased. Replacing lead comes with many problems, including a higher melting point and tin whiskers. "Tin plague" can be observed in lead-free solders.
Tinning
Tin bonds iron well and are used to coat lead, zinc and steel to prevent corrosion. Tinned steel containers are widely used for food preservation and this forms the majority of the metal tin market. In London, in 1812, a tin canister for food preservation was first made. In British English, such banks are called "tins", and in America they are called "cans" or "tin cans". The slang term for a can of beer is "tinnie" or "tinny". Copper cooking vessels such as pots and pans are often lined with a thin layer of tin, as combining acidic food with copper can be toxic.
Specialized Alloys
Tin combines with other elements to form many useful alloys. Tin is most commonly alloyed with copper. An alloy of tin with lead has 85-99% tin; bearing metal also contains a high percentage of tin. The bronze is mostly copper (12% tin), while the addition of phosphorus produces phosphor bronze. Bell bronze is also a copper-tin alloy containing 22% tin. Tin was sometimes used in coins to create American and Canadian pennies. Due to the fact that copper is often the base metal in such coins, sometimes including zinc, they may be referred to as bronze and/or brass alloys. The niobium-tin compound Nb3Sn has been commercially used in coils of superconducting magnets due to its high critical temperature (18 K) and critical magnetic field (25 T). A superconducting magnet weighing only two kilograms is capable of creating the same magnetic field as electromagnets with ordinary weight. A small proportion of tin is added to zirconium alloys for lining nuclear fuel. Most metal pipes on an organ have varying amounts of tin/lead, with 50/50 alloys being the most common. The amount of tin in the pipe determines the tone of the pipe, as the tin gives the instrument the desired resonance. When the tin/lead alloy is cooled, the lead cools slightly faster and produces a speckled or mottled effect. This metal alloy is called spotted metal. The main advantages of using tin for pipes are its appearance, workability and resistance to corrosion.
Other uses
Perforated tinned steel is an artisan technique that originated in Central Europe to create household items that were both functional and decorative. Perforated tin lanterns are the most common application of this technique. Candle light shining through the perforation creates a decorative light pattern. Lanterns and other perforated pewter have been made in the New World since the earliest European settlements. A famous example is the Revere lantern, named after Pavel Revere. Until the modern era, in a number of areas of the Alps, a goat or ram horn was sharpened and metal was pierced through it in the form of an alphabet and numbers from one to nine. This learning tool was known simply as the "horn". Modern reproductions are decorated with motifs such as hearts and tulips. In America, wooden cabinets of various styles and sizes were used for cakes and food before refrigeration, designed to repel pests and insects and keep perishable foods from dust. These were either floor or hanging cabinets. These cabinets had tin inserts in the doors and sometimes on the sides. Window panes are most commonly made by placing molten glass on top of molten tin (float glass is sheet glass made from molten metal), resulting in a flawlessly smooth surface. This is also called the "Pilkington process". Tin is also used as the negative electrode in modern lithium-ion batteries. Its use is somewhat limited by the fact that some tin surfaces catalyze the decomposition of carbonate electrolytes used in lithium-ion batteries. Tin(II) fluoride is added to some dentifrice products (SnF2). Tin(II) fluoride can be mixed with calcium abrasives, while the more common sodium fluoride gradually becomes biologically inactive in the presence of calcium compounds. It has also been shown to be more effective than sodium fluoride in controlling gingivitis.
Organotin compounds
Among all the chemical compounds of tin, organotin compounds are the most commonly used. Their world industrial production probably exceeds 50,000 tons.
PVC stabilizers
The main commercial use of organotin compounds is in the stabilization of PVC plastics. In the absence of such stabilizers, PVC would otherwise rapidly degrade when exposed to heat, light and atmospheric oxygen, causing the product to become discolored and brittle. The tin scavenges the labile chloride ions (Cl−) which would otherwise cause the loss of HCl from the plastic. Typical tin compounds are carboxylic acids derived from dibutyltin dichloride such as dibutyltin dilaurate.
Biocides
Some organotin compounds are relatively toxic, which has its advantages and disadvantages. They are used for their biocidal properties as fungicides, pesticides, algicides, wood preservatives and anti-rot agents. Tributyltin oxide is used as a wood preservative. Tributyltin has been used as an additive in marine paint to prevent the growth of marine organisms on ships, although use has declined since organotin compounds were recognized as persistent organic pollutants with extremely high toxicity to certain marine organisms (e.g., purplish). The EU banned the use of organotin compounds in 2003, while concerns about the toxicity of these compounds to marine life and damage to the reproduction and growth of some marine species (some reports describe biological effects on marine life at a concentration of 1 nm per liter) have led to worldwide ban by the International Maritime Organization. Currently, many states restrict the use of organotin compounds to vessels over 25 m in length.
Organic chemistry
Some tin reagents are useful in organic chemistry. In its most common application, stannous chloride is a common reducing agent for the conversion of nitro and oxime groups to amines. The Steele reaction binds organotin compounds to organic halides or pseudohalides.
Li-ion batteries
Tin forms several intermetallic phases with lithium metal, making it a potentially attractive material for battery applications. The large volume expansion of tin upon doping with lithium and the instability of the organotin electrolyte interface at low electrochemical potentials are the greatest difficulties for use in commercial cells. The problem has been partially resolved by Sony. Tin intermetallic compounds with cobalt and carbon are implemented by Sony in their Nexelion cells released in the late 2000s. The composition of the active substance is approximately Sn0.3Co0.4C0.3. Recent studies have shown that only certain crystal faces of tetragonal (beta) Sn are responsible for undesired electrochemical activity.
Tin (lat. Stannum; denoted by the symbol Sn) is an element of the main subgroup of the fourth group, the fifth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 50. It belongs to the group of light metals. Under normal conditions, the simple substance tin is a ductile, malleable and fusible shiny metal of a silvery-white color. Tin forms two allotropic modifications: below 13.2 °C stable α-tin (grey tin) with a cubic diamond-type lattice, above 13.2 °C stable β-tin (white tin) with a tetragonal crystal lattice.
Story
Tin was known to man already in the 4th millennium BC. e. This metal was inaccessible and expensive, since products from it are rarely found among Roman and Greek antiquities. Tin is mentioned in the Bible, the Fourth Book of Moses. Tin is (along with copper) one of the components of bronze (see History of Copper and Bronze), invented at the end or middle of the 3rd millennium BC. Since bronze was the most durable of the metals and alloys known at that time, tin was a “strategic metal” during the entire “Bronze Age”, more than 2000 years (very approximately: 35-11 centuries BC).
origin of name
The Latin name stannum, associated with the Sanskrit word meaning "resistant, strong", originally referred to an alloy of lead and silver, and later to another alloy that imitates it, containing about 67% tin; by the 4th century, this word began to be called tin itself.
The word tin is a common Slavic word that has correspondences in the Baltic languages (cf. Lit. alavas, alvas - “tin”, Prussian alwis - “lead”). It is a suffix from the root ol- (cf. Old High German elo - "yellow", Latin albus - "white", etc.), so the metal is named for its color.
Production
During the production process, ore-bearing rock (cassiterite) is crushed to an average particle size of ~ 10 mm in industrial mills, after which cassiterite, due to its relatively high density and mass, is separated from waste rock by the vibration-gravity method on concentrating tables. In addition, the flotation method of ore enrichment/purification is used. The resulting tin ore concentrate is smelted in furnaces. In the process of smelting, it is restored to a free state through the use of charcoal in the reduction, the layers of which are stacked alternately with the layers of ore.
Application
1. Tin is mainly used as a safe, non-toxic, corrosion-resistant coating in its pure form or in alloys with other metals. The main industrial applications of tin are in tinplate (tinned iron) for food packaging, solders for electronics, house plumbing, bearing alloys, and coatings of tin and its alloys. The most important alloy of tin is bronze (with copper). Another well-known alloy, pewter, is used to make tableware. Recently, there has been a revival of interest in the use of metal, since it is the most “environmentally friendly” among heavy non-ferrous metals. It is used to create superconducting wires based on the Nb 3 Sn intermetallic compound.
2. Intermetallic compounds of tin and zirconium have high melting points (up to 2000 °C) and resistance to oxidation when heated in air, and have a number of applications.
3. Tin is the most important alloying component in the production of structural titanium alloys.
4. Tin dioxide is a very effective abrasive material used in "finishing" the surface of optical glass.
5. A mixture of tin salts - "yellow composition" - was previously used as a dye for wool.
6. Tin is also used in chemical current sources as an anode material, for example: manganese-tin element, oxide-mercury-tin element. The use of tin in a lead-tin battery is promising; so, for example, at equal voltage, in comparison with a lead battery, a lead-tin battery has 2.5 times more capacity and 5 times more energy density per unit volume, its internal resistance is much lower.
The chemical element tin is one of the seven ancient metals that are known to mankind. This metal is part of bronze, which is of great importance. At present, the chemical element tin has lost its demand, but its properties deserve detailed consideration and study.
What is an element
It is located in the fifth period, in the fourth group (the main subgroup). This arrangement indicates that the chemical element tin is an amphoteric compound capable of exhibiting both basic and acidic properties. The relative atomic mass is 50, so it is considered a light element.
Peculiarities
The chemical element tin is a plastic, malleable, light silvery white substance. As it is used, it loses its luster, which is considered a minus of its characteristics. Tin is a diffuse metal, so there are difficulties with its extraction. The element has a high boiling point (2600 degrees), a low melting point (231.9 C), high electrical conductivity, and excellent malleability. It has high tear resistance.
Tin is an element that does not have toxic properties, does not adversely affect the human body, and therefore is in demand in food production.
What other property does tin have? When choosing this element for the manufacture of dishes and water pipelines, you do not have to fear for your safety.
Being in the body
What else characterizes tin (a chemical element)? How is its formula read? These issues are addressed in the course of the school curriculum. In our body, this element is located in the bones, contributing to the process of bone tissue regeneration. It is classified as a macronutrient, therefore, for a full-fledged life, a person needs from two to ten mg of tin per day.
This element enters the body in larger quantities with food, but the intestines absorb no more than five percent of the intake, so the likelihood of poisoning is minimal.
With a lack of this metal, growth slows down, hearing loss occurs, the composition of bone tissue changes, and baldness is observed. Poisoning is caused by the absorption of dust or vapors of this metal, as well as its compounds.
Basic properties
The density of tin has an average value. The metal has a high corrosion resistance, so it is used in the national economy. For example, tin is in demand in the manufacture of cans.
What else characterizes tin? The use of this metal is also based on its ability to combine various metals, creating an environment resistant to aggressive environments. For example, the metal itself is necessary for tinning household items and utensils, and its solders are needed for radio engineering and electricity.
Characteristics
According to its external characteristics, this metal is similar to aluminum. In reality, the similarity between them is insignificant, limited only by lightness and metallic luster, resistance to chemical corrosion. Aluminum exhibits amphoteric properties, therefore it easily reacts with alkalis and acids.
For example, if acetic acid acts on aluminum, a chemical reaction is observed. Tin is able to interact only with strong concentrated acids.
Advantages and disadvantages of tin
This metal is practically not used in construction, since it does not have high mechanical strength. Basically, not pure metal is currently used, but its alloys.
Let's highlight the main advantages of this metal. Of particular importance is malleability, it is used in the process of manufacturing household items. For example, stands, lamps made of this metal look aesthetically pleasing.
Tin coating allows to significantly reduce friction, thanks to which the product is protected from premature wear.
Among the main disadvantages of this metal, one can mention its slight strength. Tin is unsuitable for the manufacture of parts and parts that require significant loads.
Metal mining
Tin is melted at a low temperature, but due to the difficulty of its extraction, the metal is considered an expensive substance. Due to the low melting point, when applying tin to the metal surface, significant savings in electrical energy can be obtained.
Structure
The metal has a homogeneous structure, but, depending on the temperature, its different phases are possible, differing in characteristics. Among the most common modifications of this metal, we note the β-variant that exists at a temperature of 20 degrees. Thermal conductivity, its boiling point, are the main characteristics given for tin. When the temperature drops from 13.2 C, an α-modification is formed, called gray tin. This form does not have plasticity and malleability, has a lower density, since it has a different crystal lattice.
During the transition from one form to another, a change in volume is observed, since there is a difference in density, as a result of which the destruction of the tin product occurs. This phenomenon is called "tin plague". This feature leads to the fact that the area of \u200b\u200buse of the metal is significantly reduced.
Under natural conditions, tin can be found in the composition of rocks in the form of a trace element; in addition, its mineral forms are known. For example, cassiterite contains its oxide, and tin pyrite contains its sulfide.
Production
Tin ores, in which the metal content is not less than 0.1 percent, are considered promising for industrial processing. But at present, those deposits are also being exploited, in which the metal content is only 0.01 percent. For the extraction of the mineral, various methods are used, taking into account the specifics of the deposit, as well as its variety.
Basically, tin ores are presented in the form of sands. Extraction is reduced to its constant washing, as well as to the concentration of the ore mineral. It is much more difficult to develop a primary deposit, since additional facilities, construction and operation of mines are required.
The mineral concentrate is transported to a plant specializing in non-ferrous metal smelting. Further, repeated enrichment of the ore, grinding, then washing is carried out. Ore concentrate is restored using special furnaces. For complete recovery of tin, this process is carried out several times. At the final stage, the process of cleaning from impurities of crude tin is carried out using a thermal or electrolytic method.
Usage
As the main characteristic that allows the use of tin, its high corrosion resistance is distinguished. This metal, as well as its alloys, are among the most stable compounds in relation to aggressive chemicals. More than half of all tin produced in the world is used to make tinplate. This technology, associated with the application of a thin layer of tin on steel, began to be used to protect cans from chemical corrosion.
The ability of tin to roll out is used to produce thin-walled pipes from it. Due to the instability of this metal to low temperatures, its domestic use is quite limited.
Tin alloys have a significantly lower thermal conductivity than steel, so they can be used for the production of washbasins and bathtubs, as well as for the manufacture of various sanitary fittings.
Tin is suitable for the production of minor decorative and household items, making dishes, creating original jewelry. This dim and malleable metal, when combined with copper, has long become one of the most favorite materials of sculptors. Bronze combines high strength, resistance to chemical and natural corrosion. This alloy is in demand as a decorative and building material.
Tin is a tonal-resonant metal. For example, when it is combined with lead, an alloy is obtained that is used to make modern musical instruments. Bronze bells have been known since ancient times. To create organ pipes, an alloy of tin and lead is used.
Conclusion
Increasing attention of modern production to issues related to environmental protection, as well as to problems related to the preservation of public health, has influenced the composition of materials used in the manufacture of electronics. For example, there has been increased interest in lead-free soldering technology. Lead is a material that causes significant harm to human health, so it has ceased to be used in electrical engineering. Soldering requirements were tightened, and tin alloys began to be used instead of dangerous lead.
Pure tin is practically not used in industry, as there are problems with the development of the "tin plague". Among the main areas of application of this rare scattered element, we highlight the manufacture of superconducting wires.
Plating pure tin on the contact surfaces allows you to increase the soldering process, protect the metal from the corrosion process.
As a result of the transition to lead-free technology, many steel manufacturers began to use natural tin for coating contact surfaces and leads. This option allows you to obtain a high-quality protective coating at an affordable cost. Due to the absence of impurities, the new technology is not only considered environmentally friendly, but also makes it possible to obtain excellent results at an affordable cost. Manufacturers consider tin to be a promising and modern metal in electrical engineering and radio electronics.
Introduction
Bibliography
Introduction
The most important stage of development was the use of iron and its alloys. In the middle of the 19th century, the converter method of steel production was mastered, and by the end of the century, the open-hearth method.
Iron-based alloys are currently the main structural material.
The rapid growth of industry requires the appearance of materials with a variety of properties.
The middle of the 20th century was marked by the appearance of polymers, new materials whose properties differ sharply from those of metals.
Polymers are also widely used in various fields of technology: mechanical engineering, chemical and food industries, and a number of other areas.
The development of technology requires materials with new unique properties. Nuclear power and space technology require materials that can operate at very high temperatures.
Computer technology became possible only by using materials with special electrical properties.
Thus, materials science is one of the most important, priority sciences that determine technical progress.
Tin is one of the few metals known to man since prehistoric times. Tin and copper were discovered before iron, and their alloy, bronze, is, apparently, the very first "artificial" material, the first material prepared by man.
The results of archaeological excavations suggest that as far back as five millennia BC, people were able to smelt tin itself. It is known that the ancient Egyptians brought tin for the production of bronze from Persia.
Under the name "trapu" this metal is described in ancient Indian literature. The Latin name for tin stannum comes from the Sanskrit "hundred", which means "solid".
Tin
Tin properties:
Atomic number e50
Atomic mass 118.710
Stable 112, 114-120, 122, 124
Unstable 108-111, 113, 121, 123, 125-127
Melting point, ° С 231.9
Boiling point, ° С 262.5
Density, g/cm3 7.29
Hardness (according to Brinell) 3.9
The production of tin from ores and placers always begins with enrichment. Methods of enrichment of tin ores are quite diverse. In particular, the gravitational method is used, based on the difference in the density of the main and accompanying minerals. At the same time, we must not forget that the accompanying ones are far from always an empty breed. Often they contain valuable metals, such as tungsten, titanium, lanthanides. In such cases, they try to extract all valuable components from tin ore.
The composition of the resulting tin concentrate depends on the raw materials, and also on how this concentrate was obtained. The tin content in it ranges from 40 to 70%. The concentrate is sent to kilns (at 600...700°C), where relatively volatile impurities of arsenic and sulfur are removed from it. And most of the iron, antimony, bismuth and some other metals are leached with hydrochloric acid after firing. After this is done, it remains to separate the tin from oxygen and silicon. Therefore, the last stage in the production of crude tin is smelting with coal and fluxes in reverberatory or electric furnaces. From a physicochemical point of view, this process is similar to a blast furnace: carbon “takes away” oxygen from tin, and fluxes turn silicon dioxide into a light slag compared to metal.
There are still quite a lot of impurities in rough tin: 5 ... 8%. To obtain metal of high-quality grades (96.5 ... 99.9% Sn), fire or less often electrolytic refining is used. And the tin necessary for the semiconductor industry with a purity of almost six nines - 99.99985% Sn - is obtained mainly by zone melting.
Tin is also obtained by the regeneration of tinplate waste. In order to get a kilogram of tin, it is not necessary to process a centner of ore, you can do otherwise: "peel" 2000 old cans.
Only half a gram of tin per can. But multiplied by the scale of production, these half-grams turn into tens of tons ... The share of "secondary" tin in the industry of the capitalist countries is about a third of the total production. There are about a hundred industrial tin recovery plants in operation in our country.
It is almost impossible to remove tin from tinplate by mechanical means, so they use the difference in the chemical properties of iron and tin. Most often, tin is treated with gaseous chlorine. Iron in the absence of moisture does not react with it. Tin combines with chlorine very easily. A fuming liquid is formed - tin chloride SnCl4, which is used in the chemical and textile industries or sent to an electrolyzer to obtain metallic tin from it. And again the "circle" will begin: steel sheets will be covered with this tin, they will receive tinplate. It will be made into jars, the jars will be filled with food and sealed. Then they will open them, eat canned food, throw away the cans. And then they (not all, unfortunately) will again get to the factories of "secondary" tin.
Other elements make a cycle in nature with the participation of plants, microorganisms, etc. The tin cycle is the work of human hands.
Alloys. One third of the tin is used to make solders. Solders are alloys of tin, mainly with lead in different proportions, depending on the purpose. An alloy containing 62% Sn and 38% Pb is called eutectic and has the lowest melting point among the alloys of the Sn - Pb system. It is included in the compositions used in electronics and electrical engineering. Other lead-tin alloys, such as 30% Sn + 70% Pb, having a wide solidification area, are used for soldering pipelines and as filler material. Lead-free tin solders are also used. Tin alloys with antimony and copper are used as antifriction alloys (babbits, bronzes) in bearing technology for various mechanisms.
Composition and properties of some tin alloys
Many tin alloys are true chemical compounds of element #50 with other metals. Fusing, tin interacts with calcium, magnesium, zirconium, titanium, and many rare earth elements. The resulting compounds are characterized by a rather high refractoriness. Thus, zirconium stannide Zr3Sn2 melts only at 1985°C. And not only the refractoriness of zirconium is "to blame" here, but also the nature of the alloy, the chemical bond between the substances that form it. Or another example. Magnesium cannot be attributed to the number of refractory metals, 651 ° C is far from a record melting point. Tin melts at an even lower temperature - 232°C. And their alloy - the Mg2Sn compound - has a melting point of 778°C. Modern tin-lead alloys contain 90-97% Sn and small additions of copper and antimony to increase hardness and strength.
Connections. Tin forms various chemical compounds, many of which have important industrial uses. In addition to numerous inorganic compounds, the tin atom is capable of forming a chemical bond with carbon, which makes it possible to obtain organometallic compounds known as organotin compounds. Aqueous solutions of tin chlorides, sulfates, and fluoroborates serve as electrolytes for the deposition of tin and its alloys. Tin oxide is used as a glaze for ceramics; it gives the glaze opacity and serves as a coloring pigment. Tin oxide can also be deposited from solutions as a thin film on various products, which gives strength to glass products (or reduces the weight of vessels while maintaining their strength). The introduction of zinc stannate and other tin derivatives into plastic and synthetic materials reduces their flammability and prevents the formation of toxic fumes, and this area of application becomes important for tin compounds. A huge amount of organotin compounds is consumed as stabilizers for polyvinyl chloride - a substance used for the manufacture of containers, pipelines, transparent roofing material, window frames, gutters, etc. Other organotin compounds are used as agricultural chemicals, for the manufacture of paints and wood preservation.
The most important connections:
Tin dioxide SnO 2 is insoluble in water. In nature - the mineral cassiterite (tin stone). Obtained by oxidizing tin with oxygen. Application: for obtaining tin, white pigment for enamels, glasses, glazes.
Tin oxide SnO, black crystals. Oxidized in air above 400°C, insoluble in water. Application: black pigment in the production of ruby glass, for the production of tin salts.
Tin hydride SnH 2 is obtained in small quantities as an impurity to hydrogen during the decomposition of tin-magnesium alloys with acids (ie, under the action of hydrogen at the time of isolation). During storage, it gradually decomposes into free tin and hydrogen.
Tin tetrachloride SnCl 4 liquid fuming in air, soluble in water. Application: mordant for dyeing fabrics, polymerization catalyst.
Tin dichloride SnCl 2 is soluble in water. Forms a dihydrate. Application: reducing agent in organic synthesis, mordant for dyeing fabrics, for bleaching petroleum oils.
Tin disulfide SnS 2, golden yellow crystals, insoluble. "Gold leaf" - for finishing under the gold of wood, gypsum.
