Sulfur is a fairly common chemical element in nature (sixteenth in content in the earth's crust and sixth in natural waters). There are both native sulfur (the free state of the element) and its compounds.
Sulfur in nature
Iron pyrite, sphalerite, galena, cinnabar, antimonite are among the most important natural sulfur minerals. The World Ocean contains mainly in the form of calcium, magnesium and sodium sulfates, which cause the hardness of natural waters.
How is sulfur obtained?
Extraction of sulfur ores is carried out by different methods. The main way to obtain sulfur is to smelt it directly in the field.
Open pit mining involves the use of excavators to remove rock layers that cover the sulfur ore. After crushing the ore layers by explosions, they are sent to the sulfur smelter.
In industry, sulfur is obtained as a by-product of processes in smelting furnaces, during oil refining. It is present in large quantities in natural gas (assulfur dioxide or hydrogen sulfide), the extraction of which is deposited on the walls of the equipment used. The finely dispersed sulfur captured from the gas is used in the chemical industry as a raw material for the production of various products.
This substance can also be obtained from natural sulfur dioxide. For this, the Claus method is used. It consists in the use of "sulfur pits" in which sulfur is degassed. The result is a modified sulfur widely used in the asph alt industry.
Main allotropic modifications of sulfur
Sulfur has allotropy. A large number of allotropic modifications are known. The most famous are rhombic (crystalline), monoclinic (acicular) and plastic sulfur. The first two modifications are stable, the third one turns into a rhombic one upon solidification.
Physical properties characterizing sulfur
Molecules of orthorhombic (α-S) and monoclinic (β-S) modifications contain 8 sulfur atoms each, which are connected in a closed cycle by single covalent bonds.
Under normal conditions, sulfur has a rhombic modification. It is a yellow solid crystalline substance with a density of 2.07 g/cm3. Melts at 113°C. The density of monoclinic sulfur is 1.96 g/cm3, its melting point is 119.3 °C.
When melted, sulfur expands and becomes a yellow liquid that turns brown at 160 °C andturns into a viscous dark brown mass when it reaches about 190 °C. At temperatures above this value, the viscosity of sulfur decreases. At about 300 °C, it again passes into a liquid fluid state. This is due to the fact that during heating, sulfur polymerizes, increasing the chain length with increasing temperature. And when the temperature reaches more than 190 ° C, the destruction of polymer units is observed.
When the sulfur melt is cooled naturally in cylindrical crucibles, the so-called lump sulfur is formed - rhombic crystals of large sizes, having a distorted shape in the form of octahedrons with partially "cut" faces or corners.
If the molten substance is subjected to rapid cooling (for example, using cold water), then plastic sulfur can be obtained, which is an elastic rubber-like mass of brownish or dark red color with a density of 2.046 g/cm 3. This modification, in contrast to the rhombic and monoclinic, is unstable. Gradually (over several hours) it changes color to yellow, becomes brittle and turns into a rhombic.
When sulfur vapor (highly heated) is frozen with liquid nitrogen, its purple modification is formed, which is stable at temperatures below minus 80 °C.
Sulfur practically does not dissolve in the aquatic environment. However, it is characterized by good solubility in organic solvents. Poor conductor of electricity and heat.
The boiling point of sulfur is 444.6 °C. The boiling process is accompanied by the release of orange-yellow vapors, consisting mainly of S8 molecules, which, upon subsequent heating, dissociate, resulting in the formation of equilibrium forms S6, S4 and S2. Further, when heated, large molecules decompose, and at temperatures above 900 degrees, the pairs consist practically only of S2 molecules, dissociating into atoms at 1500 ° С.
What are the chemical properties of sulfur?
Sulfur is a typical non-metal. chemically active. Oxidizing-reducing properties of sulfur are manifested in relation to a variety of elements. When heated, it easily combines with almost all elements, which explains its mandatory presence in metal ores. The exceptions are Pt, Au, I2, N2 and inert gases. The oxidation states that sulfur exhibits in compounds are -2, +4, +6.
The properties of sulfur and oxygen cause it to burn in air. The result of this interaction is the formation of sulfurous (SO2) and sulfuric (SO3) anhydrides, which are used to produce sulfurous and sulfuric acids.
At room temperature, the reducing properties of sulfur are manifested only in relation to fluorine, in the reaction with which sulfur hexafluoride is formed:
S + 3F2=SF6.
When heated (in the form of a melt) interacts with chlorine, phosphorus, silicon, carbon. As a result of reactions with hydrogen, in addition to hydrogen sulfide, it forms sulfanes combined with a commonformula H2SX.
The oxidizing properties of sulfur are observed when interacting with metals. In some cases, quite violent reactions can be observed. As a result of interaction with metals, sulfides (sulphurous compounds) and polysulfides (polysulphurous metals) are formed.
When heated for a long time, it reacts with concentrated oxidizing acids, oxidizing at the same time.
Next, consider the main properties of sulfur compounds.
Sulfur dioxide
Sulfur oxide (IV), also called sulfur dioxide and sulfurous anhydride, is a gas (colorless) with a pungent, asphyxiating odor. It tends to liquefy under pressure at room temperature. SO2 is an acid oxide. It is characterized by good solubility in water. In this case, a weak, unstable sulfurous acid is formed, which exists only in an aqueous solution. As a result of the interaction of sulfur dioxide with alkalis, sulfites are formed.
It has a fairly high chemical activity. The most pronounced are the reducing chemical properties of sulfur oxide (IV). Such reactions are accompanied by an increase in the oxidation state of sulfur.
The oxidizing chemical properties of sulfur oxide appear in the presence of strong reducing agents (such as carbon monoxide).
Sulfur trioxide
Sulfur trioxide (sulfuric anhydride) - the highest oxide of sulfur (VI). Under normal conditions, it is a colorless, volatile liquid with a suffocating odor. Has the ability to freeze at temperaturesbelow 16.9 degrees. In this case, a mixture of different crystalline modifications of solid sulfur trioxide is formed. The high hygroscopic properties of sulfur oxide cause it to "smoke" in humid air. As a result, droplets of sulfuric acid are formed.
Hydrogen sulfide
Hydrogen sulfide is a binary chemical compound of hydrogen and sulfur. H2S is a poisonous colorless gas characterized by a sweetish taste and a rotten egg smell. It melts at minus 86 °С, boils at minus 60 °С. Thermally unstable. At temperatures above 400 °C, hydrogen sulfide decomposes into S and H2. It is characterized by good solubility in ethanol. It is poorly soluble in water. As a result of dissolution in water, weak hydrosulphuric acid is formed. Hydrogen sulfide is a strong reducing agent.
Flammable. When it burns in air, a blue flame can be observed. In high concentrations, it can react with many metals.
Sulfuric acid
Sulfuric acid (H2SO4) can be of different concentration and purity. In the anhydrous state, it is a colorless, odorless, oily liquid.
The temperature at which the substance melts is 10 °C. The boiling point is 296 °C. It dissolves well in water. When sulfuric acid is dissolved, hydrates are formed, and a large amount of heat is released. The boiling point of all aqueous solutions atpressure 760 mm Hg. Art. exceeds 100 °C. An increase in the boiling point occurs with an increase in the concentration of the acid.
The acidic properties of a substance are manifested when interacting with basic oxides and bases. H2SO4 is a dibasic acid, due to which it can form both sulfates (medium s alts) and hydrosulfates (acid s alts), most of which are soluble in water.
The properties of sulfuric acid are most clearly manifested in redox reactions. This is due to the fact that in the composition of H2SO4 sulfur has the highest oxidation state (+6). An example of the manifestation of the oxidizing properties of sulfuric acid is the reaction with copper:
Cu + 2H2SO4 =CuSO4 + 2H 2O + SO2.
Sulfur: useful properties
Sulfur is a trace element essential for living organisms. It is an integral part of amino acids (methionine and cysteine), enzymes and vitamins. This element takes part in the formation of the tertiary structure of the protein. The amount of chemically bound sulfur contained in proteins ranges from 0.8 to 2.4% by weight. The content of the element in the human body is about 2 grams per 1 kg of weight (that is, approximately 0.2% is sulfur).
The useful properties of the microelement can hardly be overestimated. Protecting blood protoplasm, sulfur is an active helper of the body in the fight against harmful bacteria. Blood clotting depends on its quantity, that is, the element helpsmaintain a sufficient level. Sulfur also plays an important role in maintaining the normal values of the concentration of bile produced by the body.
Often referred to as the "beauty mineral" because it is essential for maintaining he althy skin, nails and hair. Sulfur has the ability to protect the body from various types of negative environmental impacts. This helps slow down the aging process. Sulfur cleanses the body of toxins and protects against radiation, which is especially important at the present time, given the current environmental situation.
Insufficient amounts of microelements in the body can lead to poor excretion of toxins, reduced immunity and vitality.
Sulfur is a participant in bacterial photosynthesis. It is a component of bacteriochlorophyll, and hydrogen sulfide is a source of hydrogen.
Sulfur: properties and industrial applications
The most widely used sulfur is to produce sulfuric acid. Also, the properties of this substance make it possible to use it for the vulcanization of rubber, as a fungicide in agriculture, and even as a drug (colloidal sulfur). In addition, sulfur is used for the production of matches and pyrotechnic compositions, it is part of the sulfur-bitumen compositions for the production of sulfur asph alt.
