Antimony

Antimony. It is a chemical element with atomic number 51 located in group 15 of the periodic table of elements. Its name and abbreviation (Sb) comes from Stybian , a term now in disuse, which in turn comes (from the Latin stibium “Shiny gray sandbar”), where the word Estibio is derived. In the UK , the variable vowel is generally pronounced as a schwa. In the United States it is pronounced like an omega.

This semi-metallic element has four allotropic forms. Its stable form is a bluish-white metal. Black and yellow antimony are unstable non-metallic forms. It is mainly used in metallic alloys and some of their compounds to give resistance against fire , in paints, ceramics , enamels, vulcanization of rubber and fireworks .

Summary

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  • 1 Main features
  • 2 Applications
  • 3 Metallic uses
  • 4 Non-metallic uses
  • 5 History
  • 6 Antimony and environment
  • 7 Abundance and obtaining
  • 8 Compounds
  • 9 Precautions
  • 10 External links
  • 11 Sources

Main features

Antimony in its elemental form is a silver-white, brittle, meltable, crystalline solid that exhibits low electrical and thermal conductivity and evaporates at low temperatures. This semi-metallic element resembles metals in appearance and physical properties, but chemically behaves like a nonmetal. It can also be attacked by oxidizing acids and halogens .

Estimates of the abundance of antimony in the earth’s crust range from 0.2 to 0.5 ppm. Antimony is chalcophilic, occurring with Sulfur and other metals such as Lead , Copper and Silver .

Applications

Antimony is of growing importance in the semiconductor industry in the production of Diodes , infrared detectors and Hall Effect devices .

Used as an alloying agent, this semimetal greatly increases the hardness and mechanical strength of lead. It is also used in different alloys such as Pewter, Antifriction Metal (alloyed with Tin ), English Metal (formed by zinc and antimony), etc.

Some more specific applications:

  • Batteries and accumulators
  • Types of printing
  • Cable jacket
  • Bearings and bearings

Antimony compounds in the form of antimony oxides, sulfides, antimonates, and halides are used in the manufacture of fire-resistant materials, enamels, glasses , paints, and ceramics. Antimony trioxide is the most important and is used primarily as a flame retardant. These applications as flame retardants cover different markets such as clothing, toys , or seat covers.

Metallic uses

Since the LA battery was developed in the 19th century , it has been by far the most important secondary (or rechargeable) battery in the world. The batteries LA are used in motor vehicles, or industrial batteries.

Industrial batteries include traction batteries in mine locomotives, golf carts , and so on, “emergency power” batteries. Antimony alloyed with lead is used for certain battery parts for which resistance to corrosion was necessary.

Antimony is a minor but important component of many soft solders, which are solders that melt in temperatures below 625 K. These solders can contain between 0.5 and 3% antimony. The function of antimony in these solders is to consolidate the solder and suppress the formation of the tin allotropes at low temperatures , which would otherwise degrade the structural integrity of the soldered joints at temperatures below the point of phase transition (289 K ). Antimony has been used as a hardener for lead used in ammunition.

In the United States, its use is largely confined to the ammunition of small pistols and the barrel of some shotguns. Contamination of groundwater, soil, and the food chain with toxic lead has been a concern for many years, and environmental regulations have led to the replacement of lead with antimony, by a tungsten alloy .

Lead alloys containing about 2 to 8% antimony are resistant to atmospheric wear and corrosion and are therefore used in the construction of channels and moisture barriers. In the chemical industry, alloys containing from 4 to 15% antimony provide protection against various liquid states of chemicals, especially sulfuric acidor sulfate. Alloyed with bismuth, lead, and tin, antimony is a component of some of the fusible alloys used in fire safety devices. The metal used to manufacture characters and other typographic material is obtained from an alloy of lead, antimony and tin. Lead is used for easy melting and for making the alloy ductile and compact. The antimony serves to give more strength to the metal so that it does not crush so easily during repeated and numerous runs. The alloys are diverse, depending on the size of the types and the use to which they are put.

So for the manufacture of the metal intended for targets, the following alloy is usually used, called ordinary: 75 parts of lead, 20 parts of antimony, 5 parts of tin. Small amounts of high-purity antimony are used in DVDs .

Non-metallic uses

The tip of the safety matches contains [antimony trisulfide]. Combustion is an exothermic reaction maintained by internally generated free radicals and radiant heat. Halogen flame retardants work by interfering with the radical chain mechanism in the gas phase (the flame). When used by themselves, halogen flame retardants must be used in very large quantities. This problem is avoided by adding antimony trioxide, which works in conjunction with halogens , reducing the required amount of flame retardant and also reducing the cost of the total treatment. The mechanism of antimony and halogens working together has been tried to explain in various ways, but none is definitive.

Many common plastics are susceptible to degradation by heat and ultraviolet (UV) light and products made from them must be protected during their service life by the addition of compounds known as stabilizers. Antimony has been used since the 1950s as an effective heat stabilizer for PVC, especially in rigid forms of plastic.

Antimony trioxide is used as a catalyst in the polymerization of Polyethylene Terephthalate, which is a plastic used in bottles, films, food packaging, and many other products. Antimony compounds, along with germanium dioxide , are the preferred catalysts for PET.

Germanium dioxide gives a product with better clarity than antimony, but which is too expensive for many PET applications. Antimony trioxide is also used as a white pigment for exterior paints, where its resistance to wear by atmospheric action made it a valuable object, however, when its toxic capacity was discovered, antimony trioxide has been supplanted by carbon dioxide. titanium (TiO 2 ).

It is still used in significant quantities as a color stabilizer, where it is important to maintain color intensity and avoid hue shift, for example in the yellow paints used for school buses (American and South African) and in the applied yellow stripes. to the pavements of the road.

Electrically conductive pigments of tin oxide (SnO) with antimony have been introduced in recent years to be incorporated into plastic coatings that protect computers and other electronic components against static electricity.

Antimony was used in medicine for its good expectorant, emetic and purgative attitudes. And treatises were written on his medical qualities. Until it was decided to declare it poison, officially, on August 3 , 1866 .

At present, antimony does not have any specific use in aeronautics, however it is used in the same situations as in other industries: PET, paints, welding , etc.

History

Archaeological and historical studies indicate that antimony and its sulfides have been used by humans for at least the last 6 millennia. In ancient times antimonite or Stibnite, Sb 2 S 3 , the most common form of antimony sulfide was the main ingredient in “kohl”, a black paste used by the Egyptians among others as eye makeup. The Babylonians knew how to obtain antimony from its compounds and used it as an ornament for vessels.

The alchemist Basil Valentine ( 1565 – 1624 ), sometimes presented as the discoverer of antimony, was the first to describe the extraction of antimony from its compounds in his treatise “Triumph Wagens des Antimonij” (The Triumphal Chariot of Antimony).

The name antimony comes from a Latinization of the Arabic word (“al-ithmid”), which in turn consisted of an Arabization of the Latin word stibium.

Other theories suggest that antimony is a compound of the Latin words “anti” (fear) and “mono” (alone), which would refer to its existence in nature normally as compound. The use of the symbol “feminine” could also reveal a satirical pun on this origin.

After the invention of the printing press in the 16th century , antimony was used as an alloy for typographic stamps. On cooling, liquid antimony has the exceptional property of expanding while solidifying. In this way, it fills in the cracks in the molds, which is why the edges of the pieces obtained are very sharp. For this reason, it was used to make typefaces. In the 19th century its alloy with zinc (English metal) was used in cutlery and candle holders.

After the invention of the LA battery, it was found that the use of lead antimony alloy made batteries last much longer. During the Great War a production peak was reached, due to its use in weapons, since this semi-metal greatly increases the hardness and mechanical strength of lead and tin. With the development of the automobile industry the use of antimony has been increasing year after year, although the levels of the Great War were not reached again until the 1990s .

Antimony and environment

Antimony is released into the environment from natural and industrial sources. It can remain in the air attached to very small particles for many days. Most antimony in the air settles on the ground, where it sticks firmly to particles that contain iron , manganese, or aluminum . The air we breathe if it contains high levels of antimony for long periods of time can irritate the eyes and lungs and can cause respiratory, heart , and stomach problems .

The occupational exposure limit is 0.5 mg of antimony per m 3 of air for an 8-hour working day. The maximum allowed level of antimony in drinking water in Europe is 0.006 ppm.

In urban air, the main sources of antimony are fossil fuel combustion in motor vehicles, power plants, and incinerators.

The US Environmental Protection Agency (EPA) toxic inventory for the period 1993 to 2005 showed that US industrial plants released more than 900 T / year of antimony in all forms to land and about 25 t / year to groundwater. Of the antimony released to the ground by major industries, primary copper smelters account for about 60%; primary smelters for other non-ferrous metals, 20%; Secondary non-ferrous smelters 7% and oil refineries 2%. The remaining 11% is attributed to the manufacture of various antimony products. The post-consumer release of antimony from discarded end-use products is also of importance.

There is concern, especially in Europe , about the leaching of antimony pigments, heat stabilizers, and flame retardants from discarded plastics products. These concerns have contributed to a shift to calcium-zinc stabilizers in Europe and to tin-based stabilizers in the US and Japan . It is believed that the country that releases the most antimony into the atmosphere is China , due to the great use made of this element in that country, since it contains the main antimony mines in the world.

Abundance and obtaining

Antimony is found in nature in many minerals, although it is a rare element. Although it is possible to find it free, it is normally in the form of sulfides; the main antimony ore is Antimonite (also called Stibnite), Sb 2 S 3 .

By roasting antimony sulfide, antimony (III) oxide, Sb 2 O 3 , is obtained, which can be reduced with Coke to obtain antimony.

2Sb 2 O 3 + 3C? 4Sb + 3CO 2

It can also be obtained by direct reduction of sulfur, for example with iron scrap:

Sb 2 S 3 + 3Fe? 2Sb + 3FeS

Compounds

Its most common oxidation states are 3 and 5.

“Crude antimony” and “crudum” are terms applied to mineral containing more than 90% antimony, and to liquefied sulfide mineral, which is essentially an antimony-sulfide mixture containing 70% or more antimony. The refined metal of antimony is the common stable form of antimony.

Yellow antimony or alpha-antimony is produced by the action of ozone in liquid SbH 3 , -90 ° C. It is amorphous and poorly soluble in carbon disulfide. Yellow antimony is very unstable and easily transforms at temperatures above -90 ° C to black antimony, which can also be formed directly from liquid SbH 3 and oxygen at -40 ° C. Black antimony spontaneously oxidizes in air and becomes ordinary rhombohedral antimony or beta-antimony. The fourth allotropic form of antimony is explosive antimony that is formed from the electrolysis of antimony chloride.

This form transforms at 475 K into the most common allotropic form producing an explosion. Studies are trying to show that yellow antimony is actually impure antimony and is not a true allotropic form of antimony.

Due to its toughness, brittleness, and lack of malleability, antimony has no application as a metal by itself except for the small amounts used for ornamental castings and semiconductor devices. However, it is a minor component in many lead- tin alloys .

Most of the antimony that is used in the metallic state, such as in LA batteries, cable jacket, and various other uses, is used as some form of antimonial lead, which can contain up to 25% antimony, but more commonly contains single digit percentages. Antimony is also a component of various tin alloys, such as brittany metal, antifriction metal, and tin-antimony-silver solders used to assemble drinking water pipes.

Antimony forms a very large number of inorganic compounds. Sulfides predominate in nature and are commercially available as processed antimony minerals. In terms of the quantities produced, the most important synthetic antimony compound by far is trioxide (Sb 2 O 3 ), which is used by itself for some applications.

Other compounds used in substantial amounts are pentoxide (Sb 2 O 5 ), trisulfide (Sb 2 S 3 ) and pentasulfide (Sb 2 S 5 ). These compounds are used as flame retardants, in pigments, heat and radiation stabilizers in plastics and catalysts.

All of its trihalogenides, SbX 3 , and the pentafluoride and pentachloride, SbX 5 , are known . Trifluoride is used as a fluoridant. Pentafluoride together with HSO 3 F forms a SbF 5 -FSO 3 H system with superacid properties. With these halides different complexes can be prepared. The hydride SbH 3 ( stibnine ) is known, but it is not very stable and decomposes very easily.

Antimony trioxide, Sb 2 O 3 and pentoxide, Sb 2 O 5 are known .

Precautions

Antimony and many of its compounds are toxic, and the greatest possible care must be taken when handling them. Reacts violently with strong oxidants (example: halogens, alkali permanganates and nitrates) causing risk of fire and explosion. It reacts in an acidic medium with nascent hydrogen, producing a very toxic gas (stibamine). In contact with hot concentrated acids, it emits toxic gases (stibamine). These compounds are formed in the presence of metals that can be attacked by the acid that is being used, such as iron, so metallic objects (containers, tweezers, etc.) should never be used when cleaning with antimony mineral acid.

Its autoignition temperature is 900 ° C, and its storage must be carried out separately from food and feed, strong oxidants, acids, reducing substances. It should be handled with gloves and protective glasses.

 

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