Description and properties of sulfur

Sulfur is a substance that is in group 16, under the third period and has an atomic number of 16. It can be found both in native and bound form. Sulfur is designated by the letter S. Known sulfur formula– (Ne)3s 2 3p 4 . Sulfur as an element is included in many proteins.

The photo shows sulfur crystals

If speak about atomic structure of the element sulfur, then in its outer orbit there are electrons whose valence number reaches six.

This explains the element's property of being maximally hexavalent in most combinations. There are four isotopes in the structure of a natural chemical element, and these are 32S, 33S, 34S and 36S. Speaking about the outer electron shell, the atom has a 3s2 3p4 scheme. The radius of the atom is 0.104 nanometers.

Properties of sulfur are primarily divided into physical types. This includes the fact that the element has a solid crystalline composition. Two allotropic modifications are the main state in which this sulfur element is stable.

The first modification is rhombic, lemon-yellow in color. Its stability is lower than 95.6 °C. The second is monoclinic, having a honey-yellow color. Its resistance ranges from 95.6 °C and 119.3 °C.

The photo shows the mineral sulfur

During smelting, the chemical element becomes a moving liquid that is yellow in color. It turns brown, reaching temperatures of more than 160 °C. And at 190 °C sulfur color turns into dark brown. After reaching 190 °C, a decrease in the viscosity of the substance is observed, which nevertheless becomes liquid after heating to 300 °C.

Other properties of sulfur:

Practically does not conduct heat or electricity.

Does not dissolve when immersed in water.

It is soluble in ammonia, which has an anhydrous structure.

It is also soluble in carbon disulfide and other organic solvents.

TO characteristics of the element sulfur it is important to add its chemical features. She is active in this regard. If sulfur is heated, it can simply combine with almost any chemical element.

The photo shows a sample of sulfur mined in Uzbekistan

With the exception of inert gases. Upon contact with metals, chemicals. the element forms sulfides. Room temperature allows the element to react with. Increased temperature increases the activity of sulfur.

Let's consider how sulfur behaves with individual substances:

With metals it is an oxidizing agent. Forms sulfides.

Active interaction occurs with hydrogen at high temperatures – up to 200 °C.

With oxygen. Oxides form at temperatures up to 280 °C.

With phosphorus, carbon – it is an oxidizing agent. Only if there is no air during the reaction.

With fluorine it acts as a reducing agent.

With substances that have a complex structure - also as a reducing agent.

Sulfur deposits and production

The main source for obtaining sulfur is its deposits. In total, there are 1.4 billion tons of reserves of this substance worldwide. It is mined both by open and underground mining and by smelting from underground.

The photo shows sulfur mining in the Kawa Ijen volcano

If the latter case applies, then water is used, which is overheated and melts the sulfur with it. In low-grade ores, the element is contained in approximately 12%. Rich – 25% and more.

Common types of deposits:

Stratiform – up to 60%.

Salt dome - up to 35%.

Volcanogenic – up to 5%.

The first type is associated with strata called sulfate-carbonate. At the same time, ore bodies that have a thickness of up to several tens of meters and a size of up to hundreds of meters are located in sulfate rocks.

Also, these strata deposits can be found among rocks of sulfate and carbonate origin. The second type is characterized by gray deposits, which are confined to salt domes.

The latter type is associated with volcanoes that have a young and modern structure. In this case, the ore element has a sheet-like, lens-shaped shape. It may contain sulfur in the amount of 40%. This type of deposit is common in the Pacific volcanic belt.

Sulfur deposit in Eurasia is located in Turkmenistan, the Volga region and other places. Sulfur rocks are found near the left banks of the Volga, which stretch from Samara. The width of the rock strip reaches several kilometers. Moreover, they can be found all the way to Kazan.

The photo shows sulfur in rock

In Texas and Louisiana, huge amounts of sulfur are found in the roofs of salt domes. Particularly beautiful Italians of this element are found in Romagna and Sicily. And on the island of Vulcano they find monoclinic sulfur. The element, which was oxidized by pyrite, was found in the Urals in the Chelyabinsk region.

For mining sulfur chemical element use different methods. It all depends on the conditions of its occurrence. At the same time, of course, special attention is paid to safety.

Since hydrogen sulfide accumulates along with sulfur ore, it is necessary to take a particularly serious approach to any mining method, because this gas is poisonous to humans. Sulfur also tends to ignite.

Most often they use the open method. So, with the help of excavators, significant parts of the rocks are removed. Then the ore part is crushed using explosions. The lumps are sent to the factory for enrichment. Then - to the sulfur smelting plant, where sulfur is obtained from concentrate.

The photo shows sulfur in the port, brought by sea

In the case of deep occurrence of sulfur in many volumes, the Frasch method is used. The sulfur melts while still underground. Then, like oil, it is pumped out through a broken well. This approach is based on the fact that the element melts easily and has a low density.

A separation method using centrifuges is also known. Only this method has a drawback: sulfur is obtained with impurities. And then it is necessary to carry out additional cleaning.

In some cases, the borehole method is used. Other possibilities for mining the sulfur element:

Steam-water.

Filtration.

Thermal.

Centrifugal.

Extraction.

Application of sulfur

Most of the mined sulfur is used to make sulfuric acid. And the role of this substance is very huge in chemical production. It is noteworthy that to obtain 1 ton of sulfuric substance, 300 kg of sulfur is needed.

Sparklers, which glow brightly and have many dyes, are also made using sulfur. The paper industry is another area where a significant portion of the extracted substance goes.

Pictured is sulfur ointment

More often application of sulfur finds when meeting production needs. Here are some of them:

Use in chemical production.

For the production of sulfites, sulfates.

Production of substances for fertilizing plants.

To obtain non-ferrous types of metals.

To give steel additional properties.

For making matches, materials for explosions and pyrotechnics.

Paints and fibers from artificial materials are produced using this element.

For bleaching fabrics.

In some cases sulfur element included in ointments that treat skin diseases.

Sulfur price

According to the latest news, the need for sulfur is actively growing. The cost of a Russian product is 130 dollars. For the Canadian version – $145. But in the Middle East, prices increased to $8, resulting in a cost of $149.

The photo shows a large specimen of the mineral sulfur

In pharmacies you can find ground sulfur powder at a price of 10 to 30 rubles. In addition, it is possible to buy it in bulk. Some organizations offer to purchase granular technical equipment at a low price. gas sulfur.

Chalcogens are a group of elements to which sulfur belongs. Its chemical symbol is S, the first letter of the Latin name Sulfur. The composition of a simple substance is written using this symbol without an index. Let's consider the main points concerning the structure, properties, production and use of this element. The characteristics of sulfur will be presented in as much detail as possible.

General characteristics and differences of chalcogens

Sulfur belongs to the oxygen subgroup. This is the 16th group in the modern long-period form of the periodic system (PS). The outdated version of the number and index is VIA. Names of chemical elements of the group, chemical symbols:

• oxygen (O);
• sulfur (S);
• selenium (Se);
• tellurium (Te);
• polonium (Po).

The outer electronic shell of the above elements has the same structure. In total, it contains 6 which can participate in the formation of chemical bonds with other atoms. Hydrogen compounds correspond to the composition H 2 R, for example, H 2 S is hydrogen sulfide. Names of chemical elements that form two types of compounds with oxygen: sulfur, selenium and tellurium. The general formulas of the oxides of these elements are RO 2, RO 3.

Chalcogens correspond to simple substances that differ significantly in physical properties. The most common chalcogens in the earth's crust are oxygen and sulfur. The first element forms two gases, the second - solids. Polonium, a radioactive element, is rarely found in the earth's crust. In the group from oxygen to polonium, non-metallic properties decrease and metallic properties increase. For example, sulfur is a typical non-metal, while tellurium has a metallic luster and electrical conductivity.

Element No. 16 of the periodic table D.I. Mendeleev

The relative atomic mass of sulfur is 32.064. Of the natural isotopes, 32 S is the most common (more than 95% by weight). Nuclides with atomic masses 33, 34 and 36 are found in smaller quantities. Characteristics of sulfur by position in the PS and atomic structure:

• serial number - 16;
• the charge of the atomic nucleus is +16;
• atomic radius - 0.104 nm;
• ionization energy -10.36 eV;
• relative electronegativity - 2.6;
• oxidation state in compounds - +6, +4, +2, -2;
• valency - II(-), II(+), IV(+), VI (+).

Sulfur is in the third period; electrons in an atom are located at three energy levels: on the first - 2, on the second - 8, on the third - 6. All external electrons are valence. When interacting with more electronegative elements, sulfur gives up 4 or 6 electrons, acquiring typical oxidation states of +6, +4. In reactions with hydrogen and metals, the atom attracts the missing 2 electrons until the octet is filled and a stable state is achieved. in this case it is reduced to -2.

Physical properties of rhombic and monoclinic allotropic forms

Under normal conditions, sulfur atoms are connected to each other at an angle to form stable chains. They can be closed in rings, which suggests the existence of cyclic sulfur molecules. Their composition is reflected by the formulas S 6 and S 8.

The characteristics of sulfur should be supplemented by a description of the differences between allotropic modifications that have different physical properties.

Rhombic, or α-sulfur, is the most stable crystalline form. These are bright yellow crystals consisting of S 8 molecules. The density of rhombic sulfur is 2.07 g/cm3. Light yellow monoclinic crystals are formed by β-sulfur with a density of 1.96 g/cm3. The boiling point reaches 444.5°C.

Preparation of amorphous sulfur

What color is sulfur in its plastic state? It is a dark brown mass, completely different from the yellow powder or crystals. To obtain it, you need to melt orthorhombic or monoclinic sulfur. At temperatures above 110°C, a liquid is formed; with further heating it darkens, and at 200°C it becomes thick and viscous. If you quickly pour molten sulfur into cold water, it will solidify to form zigzag chains, the composition of which is reflected by the formula S n.

Sulfur solubility

Some modifications in carbon disulfide, benzene, toluene and liquid ammonia. If organic solutions are slowly cooled, needle-shaped crystals of monoclinic sulfur are formed. When liquids evaporate, transparent lemon-yellow crystals of rhombic sulfur are released. They are fragile and can be easily ground into powder. Sulfur does not dissolve in water. The crystals sink to the bottom of the vessel, and the powder may float on the surface (not wetted).

Chemical properties

The reactions exhibit the typical non-metallic properties of element No. 16:

• sulfur oxidizes metals and hydrogen and is reduced to the S 2- ion;
• combustion in air and oxygen produces sulfur di- and trioxide, which are acid anhydrides;
• in a reaction with another more electronegative element - fluorine - sulfur also loses its electrons (oxidizes).

Free sulfur in nature

In terms of abundance in the earth's crust, sulfur is in 15th place among the chemical elements. The average content of S atoms is 0.05% of the mass of the earth's crust.

What color is sulfur in nature (native)? It is a light yellow powder with a characteristic odor or yellow crystals with a glassy luster. Deposits in the form of placers, crystalline layers of sulfur are found in areas of ancient and modern volcanism: in Italy, Poland, Central Asia, Japan, Mexico, and the USA. Often, beautiful druses and giant single crystals are found during mining.

Hydrogen sulfide and oxides in nature

In areas of volcanism, gaseous sulfur compounds come to the surface. The Black Sea at a depth of over 200 m is lifeless due to the release of hydrogen sulfide H 2 S. The formula of sulfur oxide is divalent - SO 2, trivalent - SO 3. The listed gaseous compounds are present in some deposits of oil, gas, and natural waters. Sulfur is a component of coal. It is necessary for the construction of many organic compounds. When the whites of a chicken egg rot, hydrogen sulfide is released, which is why this gas is often said to have the smell of rotten eggs. Sulfur is a biogenic element; it is necessary for the growth and development of humans, animals and plants.

The importance of natural sulfides and sulfates

The characterization of sulfur will be incomplete if it is not said that the element is found not only in the form of simple substances and oxides. The most common natural compounds are salts of hydrogen sulfide and sulfuric acids. Sulfides of copper, iron, zinc, mercury, and lead are found in the minerals sphalerite, cinnabar and galena. Sulfates include sodium, calcium, barium and magnesium salts, which are formed in nature by minerals and rocks (mirabilite, gypsum, selenite, barite, kieserite, epsomite). All these compounds are used in various sectors of the economy, used as raw materials for industrial processing, fertilizers, and building materials. Some crystalline hydrates are of great medical importance.

Receipt

The yellow substance in a free state is found in nature at different depths. If necessary, sulfur is smelted from rocks, not by raising them to the surface, but by pumping superheated water into the depths. Another method involves sublimation from crushed rocks in special furnaces. Other methods involve dissolution with carbon disulfide or flotation.

Industry needs for sulfur are great, so its compounds are used to obtain the elemental substance. In hydrogen sulfide and sulfides, sulfur is in reduced form. The oxidation state of the element is -2. Sulfur is oxidized, increasing this value to 0. For example, according to the Leblanc method, sodium sulfate is reduced with coal to sulfide. Then calcium sulfide is obtained from it, treated with carbon dioxide and water vapor. The resulting hydrogen sulfide is oxidized with atmospheric oxygen in the presence of a catalyst: 2H 2 S + O 2 = 2H 2 O + 2S. Determination of sulfur obtained by different methods sometimes gives low purity values. Refining or purification is carried out by distillation, rectification, and treatment with mixtures of acids.

Application of sulfur in modern industry

Granulated sulfur is used for various production needs:

1. Production of sulfuric acid in the chemical industry.
2. Production of sulfites and sulfates.
3. Production of preparations for plant nutrition, combating diseases and pests of agricultural crops.
4. Sulfur-containing ores are processed at mining and chemical plants to produce non-ferrous metals. A related production is sulfuric acid production.
5. Introduction to the composition of certain types of steel to impart special properties.
6. Thanks they get rubber.
7. Production of matches, pyrotechnics, explosives.
8. Use for the preparation of paints, pigments, artificial fibers.
9. Bleaching of fabrics.

Toxicity of sulfur and its compounds

Dust particles with an unpleasant odor irritate the mucous membranes of the nasal cavity and respiratory tract, eyes, and skin. But the toxicity of elemental sulfur is not considered particularly high. Inhalation of hydrogen sulfide and dioxide can cause severe poisoning.

If during the roasting of sulfur-containing ores at metallurgical plants the exhaust gases are not captured, they enter the atmosphere. Combining with drops and water vapor, oxides of sulfur and nitrogen give rise to so-called acid rain.

Sulfur and its compounds in agriculture

Plants absorb sulfate ions along with the soil solution. A decrease in sulfur content leads to a slowdown in the metabolism of amino acids and proteins in green cells. Therefore, sulfates are used for fertilizing agricultural crops.

To disinfect poultry houses, basements, and vegetable stores, the simple substance is burned or the premises are treated with modern sulfur-containing preparations. Sulfur oxide has antimicrobial properties, which has long been used in the production of wines and in the storage of vegetables and fruits. Sulfur preparations are used as pesticides to combat diseases and pests of agricultural crops (powdery mildew and spider mites).

Application in medicine

The great ancient healers Avicenna and Paracelsus attached great importance to the study of the medicinal properties of yellow powder. Later it was found that a person who does not receive enough sulfur in food becomes weaker and experiences health problems (these include itching and flaking of the skin, weakening of hair and nails). The fact is that without sulfur, the synthesis of amino acids, keratin, and biochemical processes in the body is disrupted.

Medical sulfur is included in ointments for the treatment of skin diseases: acne, eczema, psoriasis, allergies, seborrhea. Baths with sulfur can relieve pain from rheumatism and gout. For better absorption by the body, water-soluble sulfur-containing preparations have been created. This is not a yellow powder, but a white, finely crystalline substance. When this compound is used externally, it is included in a cosmetic product for skin care.

Plaster has long been used to immobilize injured parts of the human body. prescribed as a laxative medicine. Magnesia lowers blood pressure, which is used in the treatment of hypertension.

Sulfur in history

Even in ancient times, a yellow non-metallic substance attracted human attention. But it was not until 1789 that the great chemist Lavoisier discovered that powders and crystals found in nature were composed of sulfur atoms. It was believed that the unpleasant odor produced by burning it repels all evil spirits. The formula of sulfur oxide, which is obtained during combustion, is SO 2 (dioxide). It is a toxic gas and inhaling it is hazardous to health. Scientists explain several cases of mass extinction of people by entire villages on the coasts and in the lowlands by the release of hydrogen sulfide or sulfur dioxide from the ground or water.

The invention of black powder increased military interest in yellow crystals. Many battles were won thanks to the ability of craftsmen to combine sulfur with other substances during the manufacturing process. The most important compound - sulfuric acid - was also learned to be used a very long time ago. In the Middle Ages, this substance was called oil of vitriol, and salts were called vitriol. Copper sulfate CuSO 4 and iron sulfate FeSO 4 have still not lost their importance in industry and agriculture.

SULFUR

Dissolving sulfur

Sulfur, which is known to be insoluble in water and dissolves in small quantities in benzene, alcohol or ether, is perfectly soluble in carbon disulfide cs2.

If you slowly evaporate a solution of a small amount of sulfur in carbon disulfide on a watch glass, you will get large crystals of the so-called rhombic or a-sulfur. But let’s not forget about the flammability and toxicity of carbon disulfide, so let’s turn off all the burners and place the watch glass under the draft or in front of the window.

Another form - monoclinic or b-cepa - can be obtained by patiently crystallizing needles about 1 cm long from toluene (toluene is also flammable!).

Production of hydrogen sulfide and experiments with it

Place a little (about the size of a pea) of the resulting iron sulfide in a test tube and add dilute hydrochloric acid. Substances interact with violent gas release:

fes + 2hcl = h2s + fecl2

An unpleasant smell of rotten eggs comes from the test tube - this is hydrogen sulfide evaporating. If you pass it through water, it will partially dissolve. A weak acid is formed, a solution of which is often called hydrogen sulfide water.

Extreme care must be taken when working with hydrogen sulfide, as the gas is almost as poisonous as hydrocyanic acid hcn. It causes paralysis of the respiratory tract and death if the concentration of hydrogen sulfide in the air is 1.2-2.8 mg/l.

Chemically, hydrogen sulfide is detected using wet lead reagent paper. To obtain it, we moisten filter paper with a dilute solution of lead acetate or nitrate, dry it and cut it into strips 1 cm wide. Hydrogen sulfide reacts with lead ions, resulting in the formation of black lead sulfide. This method can detect hydrogen sulfide in spoiled food products (eggs, meat).

We recommend producing hydrogen sulfide using the dry method, since in this case the gas flow can be easily adjusted and shut off at the right time. For this purpose, melt about 25 g of paraffin in a porcelain cup and mix 15 g of sulfur with the melt. Then remove the burner and stir the mixture until it hardens. Grind the solid mass and save it for further experiments.

When it is necessary to obtain hydrogen sulfide, we heat several pieces of a mixture of paraffin and sulfur in a test tube to a temperature above 170°C. As the temperature rises, the gas output increases, and if the burner is removed, it stops. During the reaction, paraffin hydrogen interacts with sulfur, resulting in the formation of hydrogen sulfide, and carbon remains in the test tube, for example:

c40h82 + 41s = 41h2s + 40c

We obtain sulfides

To examine the color of precipitated metal sulfides, let us pass hydrogen sulfide through solutions of various metal salts. Sulfides of manganese, zinc, cobalt, nickel and iron will precipitate if an alkaline environment is created in the solution (for example, by adding ammonium hydroxide). Lead, copper, bismuth, cadmium, antimony and tin sulfides will precipitate in the hydrochloric acid solution.

Hydrogen sulfide combustion

Having made a preliminary test for detonating gas, let’s ignite the hydrogen sulfide coming out of a glass tube drawn at the end. Hydrogen sulfide burns with a pale flame with a blue halo:

ЗН2s + ЗО2 = 2h2o + 2so2

As a result of combustion, sulfur oxide (iv) or sulfur dioxide is produced. It is easily identified by its pungent odor and the redness of wet blue litmus paper. If there is insufficient access to oxygen, hydrogen sulfide is oxidized only to sulfur. Activated carbon catalytically accelerates this process. This method is often used for fine purification of industrial gases, the sulfur content of which should not exceed 25 g/m3:

2h2s + O2 = 2H2O + 2s

It is not difficult to reproduce this process. The installation diagram is shown in the figure. The main thing is to pass air and hydrogen sulfide through activated carbon in a ratio of 1: 3. Yellow sulfur will be released on the carbon.

Activated carbon can be cleaned of sulfur by washing it in carbon disulfide. In technology, a solution of ammonium sulfide (nh4)2s is most often used for this purpose.

Experiments with sulfurous acid

Sulfur oxide (iv) - sulfur dioxide - is extremely soluble in water, resulting in the formation of sulfurous acid:

h2o + so2 = h2so3

It kills germs and has a whitening effect; In breweries and wineries, barrels are fumigated with sulfur. Sulfur dioxide is also used to bleach wicker baskets, wet wool, straw, cotton and silk. Stains

From blueberries, for example, they are eliminated if you keep a moist, contaminated area in the “vapor” of burning sulfur for a long time.

Let's check the bleaching effect of sulfurous acid. To do this, let’s lower the cylinder, where pieces of sulfur have been burning for some time, into various colored objects (flowers, wet pieces of fabric, important litmus paper, etc.), cover the cylinder well with a glass plate and wait for a while.

Anyone who has ever studied the atomic structure of elements knows that the sulfur atom has six so-called valence electrons in its outer orbit. Therefore, sulfur can be maximally hexavalent in compounds. This oxidation state corresponds to sulfur oxide (vi) with the formula so3. It is a sulfuric anhydride:

h2o + so3 = h2so4

When sulfur is burned under normal conditions, sulfur oxide (iv) is always produced. And if a certain amount of sulfur oxide (vi) is formed, then most often it immediately decomposes under the influence of heat into sulfur oxide (iv) and oxygen:

2so3 = 2so2 + o2

In the production of sulfuric acid, the main problem is the conversion of sO2 to so3. For this purpose, two methods are now used: chamber (or improved - tower) and contact. (see experiment "Preparation of sulfuric acid)

Preparation of sulfuric acid

Chamber method

Let's fill a large vessel (500 ml round-bottomed flask) with sulfur oxide (iv) so2, placing burning pieces of sulfur in it for a while or supplying gas from the apparatus where it is formed. Sulfur oxide (iv) can also be prepared relatively easily by dropping concentrated sulfuric acid into a concentrated solution of sodium sulfite na2so3. In this case, sulfuric acid, being stronger, will displace the weak acid from its salts.

When the flask is filled with gas, close it with a stopper with three holes. In one, as shown in the figure, we insert a glass tube bent at a right angle, connected to the side outlet of the test tube, in which, when pieces of copper and nitric acid interact, nitric oxide is formed (iv):

4hno3 + Сu = cu(no3)2 + 2h2o + 2no2

The acid concentration should be about 60% (wt). Attention! no2 is a strong poison!

Into another hole we will insert a glass tube connected to the test tube, through which water vapor will later flow.

In the third hole we insert a short piece of tube with a Bunsen valve - a short piece of rubber hose with a slot. First, let's create a strong influx of nitrogen oxide into the flask. (Caution! Poison!) But there is no reaction yet. The flask contains a mixture of brown no2 and colorless so2. As soon as we pass water vapor, a change in color will indicate that the reaction has begun. Under the influence of water vapor, nitrogen oxide (iv) oxidizes sulfur oxide (iv) to sulfur oxide (vi), which immediately, interacting with water vapor, turns into sulfuric acid:

2no2 + 2so2 = 2no + so3

Colorless condensate will collect at the bottom of the flask, and excess gas and vapor will escape through the Bunsen valve. Let's pour the colorless liquid from the flask into a test tube, check the acidic reaction with litmus paper and detect the sulfate ion so42- of the resulting sulfuric acid by adding a solution of barium chloride. A thick white precipitate of barium sulfate will indicate to us that the experiment was successful.

By this principle, but on a much larger scale, sulfuric acid is produced in technology. Previously, reaction chambers were lined with lead, as it is resistant to sulfuric acid vapor. In modern tower installations, ceramic-based reactors are used. But larger quantities of sulfuric acid are now produced using the contact method.

Contact method

Various cheeses are used in the production of sulfuric acid. Pure sulfur began to be used only in the 60s. In most cases, enterprises produce sulfur oxide (iv) by roasting sulfide ores. In a rotary tube kiln or multi-deck kiln, pyrite reacts with atmospheric oxygen according to the following equation:

4fes2 + 11O2 = 3fe2o3 + 8so2

The resulting iron(iii) oxide is removed from the furnace as scale and further processed in iron production plants. Crush several pieces of pyrite in a mortar and place them in a refractory glass tube, which we close with a stopper with a hole. Then use a burner to heat the tube strongly, while simultaneously passing air through it using a rubber bulb. In order for the volatile dust from the roasting gas to settle, we will take it into an empty glass vessel, and from it into a second refractory tube, which contains a catalyst heated to 400-500 °C. In technology, vanadium (v) oxide v2o5 or sodium vanadate navo3 is most often used as a catalyst, and for this purpose we will use red iron oxide (iii) fe2O3. Apply finely ground iron oxide onto glass wool, which we distribute in a tube in a layer 5 cm long. Heat the tube with the catalyst until it reaches red heat. On the catalyst, sulfur oxide (iv) interacts with atmospheric oxygen; as a result, sulfur oxide (vi) is formed

2so2 + o2 = 2so3

which we distinguish by its ability to form fog in moist air. Collect so2 in an empty flask and, shaking vigorously, mix with a small amount of water. We will obtain sulfuric acid - we will prove its presence, as in the previous method.

You can also place the glass wool and catalyst separated in one of the glass tubes. You can also work in a test tube with a side outlet. Let's put pyrite on the test tubes, a layer of glass wool on it, and then glass wool with a catalyst. We introduce air from above into the tube, which should fit close to the catalyst. On the side branch we will attach a tube bent at an angle, which leads into the test tube.

If there is no pyrite, then in a test tube with a side outlet we will obtain sulfur oxide (iv) from sodium sulfite or hydrosulfite of sulfuric acid, and then pass the resulting gas over the catalyst along with a stream of air or oxygen. Chromium oxide (III) can also be used as a catalyst, which should be calcined in an iron crucible and finely crushed in a mortar. For the same purpose, you can soak a clay shard with a solution of iron (ii) sulfate and then strongly calcinate it. In this case, a fine powder of oxide iron (iii) is formed on the clay.

Acid from gypsum

If there are few metal sulfides (as, for example, in Germany), the starting products for the production of sulfuric acid can be caso4 anhydrite and caso4-h2o gypsum. The method for obtaining sulfur oxide (iv) from these products was developed by Müller and Kuehne 60 years ago.

Methods for producing sulfuric acid from anhydrite will continue to be important in the future, since sulfuric acid is the most common chemical product. Sulfates can be decomposed using high (up to 2000 °C) temperatures. Müller found that the decomposition temperature of calcium sulfate could be reduced to 1200 °C by adding finely ground coke. First, at 900 °C, coke reduces calcium sulfate to sulfide, which in turn, at a temperature of 1200 °C, reacts with undecomposed sulfate; in this case, sulfur oxide (iv) and quicklime are formed:

caso4 + 2c = cas + 2co2

cas + 3caso4 = 4cao + 4so2

It is possible to decompose calcium sulfate in laboratory conditions only when using appropriate high temperature. We will work with equipment similar to that which was used for firing pyrite, only we will take a porcelain or iron tube for combustion. Close the tube with plugs wrapped in asbestos fabric for thermal insulation. We will insert a capillary into the hole in the first plug, and into the second, a simple glass tube, which we will connect with a washing bottle half filled with water or a fuchsin solution.

Let's prepare the reaction mixture as follows. Grind 10 g of gypsum, 5 g of kaolin (clay) and 1.5 g of active powdered carbon in a mortar. Dry the mixture by heating it for some time at 200 °C in a porcelain cup. After cooling (preferably in a desiccator), add the mixture to the middle of the combustion tube. At the same time, pay attention to ensure that it does not fill the entire cross-section of the tube. Then we heat the tube strongly using two burners (one from below, the second obliquely from above) and, when the tube is heated, we pass a not too strong air flow through the entire system. Within 10 minutes, due to the formation of sulfurous acid, the fuchsin solution in the washing bottle will become discolored. Turn off the water jet pump and stop heating.

We can also get a high temperature if we wrap a porcelain tube as tightly as possible with a 750-1000 W heating coil (see figure). We connect the ends of the spiral with thick copper wire, which we also wrap around the tube many times, and then insulate it with porcelain beads and connect it to the plug. (Careful when working with 220 V!) Naturally, a glass torch or blowtorch can also be useful as a heating source.

The technique works with a mixture of anhydrite, coke, clay, sand and pyrite cinder fe2o3. A worm conveyor delivers the mixture to a 70-meter rotating tube furnace, where the pulverized coal is burned. The temperature at the end of the furnace, at the combustion site, is approximately 1400 °C. At this temperature, the quicklime formed during the reaction is fused with clay, sand and pyrite cinder to form cement clinker. The cooled clinker is ground and mixed with a few percent of gypsum. The resulting high-quality Portland cement goes on sale. With careful implementation and control of the process, from 100 tons of anhydrite (plus clay, sand, coke and pyrite cinder) you can get about 72 tons of sulfuric acid and 62 tons of cement clinker.

Sulfuric acid can also be obtained from kieserite (magnesium sulfate mgso4 -H2O).

For the experiment, we will use the same setup as for the decomposition of gypsum, but this time we will take a tube made of refractory glass. We obtain the reaction mixture by calcining 5 g of magnesium sulfate in a porcelain bowl, and 0.5 g of active carbon in an iron crucible with a lid, and then mixing them and growing in a mortar to a dusty state. Transfer the mixture to a porcelain boat and place it in the reaction tube.

The white mass that will be obtained at the end of the experiment in a porcelain boat consists of magnesium oxide. In technology, it is processed into Sorel cement, which is the basis for the production of xylolite.

The production of derivative products such as cement clinker and xylolite, which are important for the construction industry, makes the production of sulfuric acid from local raw materials particularly economical. Processing intermediates and by-products into valuable raw materials or final products is an important principle of the chemical industry.

Let's get xylolite

Mix equal parts of magnesium oxide and sawdust with a solution of magnesium chloride and apply a layer of the resulting slurry about 1 cm thick to the substrate. After 24-48 hours the mass will harden like stone. It does not burn, it can be drilled, sawed and nailed. In the construction of houses, xylolite is used as a flooring material. Wood fiber, hardened without filling the gaps with Sorel cement (magnesium cement), pressed and glued into slabs, is used as a lightweight, heat- and sound-proof building material (Heraclitus slabs).

Sulfur and its compounds.

Equipment, reagents:

Sulfur (small pieces), sulfur (powder), reduced iron, dry sodium sulfite, concentrated sulfuric acid, copper, sodium hydroxide, phenolphthalein, fuchsin, sugar, crystalline potassium permanganate, alcohol, copper (II) oxide.

Large test tubes - 5 pcs., small test tubes - 6 pcs., a test tube rack, a prefabricated rack, a mortar and pestle, a small crucible, a small flask with a gas outlet tube and a dropping funnel, a small glass, glass stirring rods, flasks, cotton wool, porcelain cups, tiles. electric.

Sulfur and its properties

Features of sulfur melting.

Small pieces of sulfur are placed in a test tube to fill 1/3 of its volume (sulfur color is less suitable for these purposes, since strong foaming is observed when it melts). The test tube with sulfur is heated until the sulfur melts (119 "C). With further heating, the sulfur darkens and begins to thicken (maximum thickening at 200 "C). At this moment, the test tube is turned upside down for a moment, and the sulfur will not spill out. With even stronger heating, the sulfur liquefies again, and at 445 "C it boils. Boiling sulfur is poured into a glass or crystallizer with water, while making a circular motion with the test tube. Plastic sulfur solidifies in the water. If you remove it from the water (using a glass rod) , then it stretches like rubber.

Reaction between sulfur and iron.

a) The experiment is carried out in a test tube. First, prepare a mixture of substances in a ratio of 7: 4

(Ar(Fe): Ar(S) = 56: 32). For example, it is enough to take 3.5 g of iron and 2 g of sulfur. In the resulting mixture, individual particles of sulfur, iron and the color of these substances are distinguishable. If you throw a little of the mixture into a glass of water, the sulfur floats (not wetted by water), and the iron sinks (wetted by water).

The mixture can be separated using a magnet. To do this, a magnet is brought to the mixture on a watch glass or glass plate covered with paper, which attracts iron, the sulfur remains on the watch

glass The mixture is transferred into a test tube, which is fixed in a tripod leg at a slightly inclined angle and heated. It is enough to achieve the start of the reaction (red-hot) in one place of the mixture - and the reaction continues by itself (the process is exothermic). To extract the resulting iron sulfide, the test tube is broken. So, from two substances, if they were taken in quantities corresponding to the calculations, one substance was obtained, having properties different from the properties of the original substances.

Possible problems during the experiment

1. For the experiment, you need to take only reduced iron. When using ordinary sawdust, the reaction does not occur, since each grain is covered with a thin film of iron oxides, which

prevents the contact of iron with sulfur.

2. The reaction will not proceed or only isolated outbreaks will be observed if the mixture is poorly mixed and there is not sufficient contact of sulfur with iron.

3. The reaction will not work if the grains of iron are very large, therefore, the surface of contact with sulfur is small.

Sulfur (IV) oxide and sulfurous acid.

Preparation of sulfur (IV) oxide.

a) The flask with solid sodium sulfite is closed with a stopper and a dropping funnel. When adding concentrated sulfuric acid (the acid must be added drop by drop. When observed

strong gas evolution, then the addition of acid is stopped) sulfur oxide (IV) is released. The reaction occurs without heating.

b) Concentrated sulfuric acid is added to copper (shavings, sawdust or wire) and heated. Sulfur (IV) oxide is collected by displacing air.

Dissolution of sulfur (IV) oxide in water.

Place the cylinder with the hole facing up and fill it with sulfur (IV) oxide. The completeness of filling is controlled as with carbon dioxide with a burning torch. The cylinder is covered with glass

plate and hole downwards are lowered into a crystallizer with water. When the cylinder is rocked, water gradually enters it. The solubility of sulfur (IV) oxide in water is very high and at room conditions is on average 40 volumes of gas per 1 volume of water, which is approximately 10% by weight. High solubility always allows students to conclude that in this case a chemical reaction occurs between the dissolving gas and the solvent.

reaction.

Chemical properties of sulfurous acid.

100 - 150 ml of water is poured into a flask and sulfur (IV) oxide is passed through for several minutes so that the solution has a strong odor. This bottle is closed with a stopper.

a) 1/3 of the volume of the test tube is filled with water tinted with magenta. Add sulfurous acid to the colored water and stir the solution. Sulfurous acid gives a colorless solution with organic dyes. Heat the solution to boiling. The magenta color is restored again. Why?

If it's a chemical compound and is found in water from open water sources, then in insignificant concentrations. It is found in the bottom layers, where it is formed due to difficult aeration and lack of wind mixing of water bodies. This process occurs mainly in the winter months, while in the summer it is caused by intense biochemical oxidation of organic matter located in the water column. Excessive hydrogen sulfide saturation is an indicator of serious organic pollution of a reservoir.

It should be noted that this sulfur compound is characterized by three forms of presence in water:

H 2 S - undissociated molecules;

HS - hydrosulfide ions;

S 2- - sulfide ions (this form is much less common than others).

The ratio of their concentrations is built on the basis of the pH values ​​of a particular water body:

pH< 10 (насыщенность сульфидными ионами можно в расчет не принимать);

pH = 7 (H2S and HS- are in approximately equal proportions);

pH = 4 (99.8% of hydrogen sulfide is H 2 S molecules).

The primary suppliers of sulfides and hydrogen sulfide include reduction processes that occur against the background of biochemical oxidation and bacterial decomposition of various compounds. The processes occurring in underground sources and in the bottom layers of open reservoirs are particularly intense. Natural catalysts are: oxygen deficiency and weak mixing of water masses. The reaction involves both compounds of organic origin and substances coming from household wastewater.

These compounds enter water bodies in the discharges of metallurgy and food industry enterprises, and are added with discharges from chemical plants. For example, during the production of kraft pulp, about 0.01-0.014 milligrams of these compounds per liter are released into water. Receipts from oil refineries and from municipal sewage drains are also significant. A high percentage of sulfides and hydrogen sulfide is mixed into the water with mineral fertilizers.

Oxygen enrichment and microbiological activity quickly reduce hydrogen sulfide saturation. As a result of the oxidation and vital activity of thionic, colorless and colored sulfur bacteria, sulfates and sulfur are released into the water. The process takes place with high intensity - up to 0.5 g of hydrogen sulfide can be formed in a liter of water per day. This sulfur compound is toxic and has an unpleasant odor, which seriously impairs the organoleptic characteristics of water. Such water cannot be used for drinking or household purposes.

There is no maximum permissible concentration for sulfides and hydrogen sulfide for fishing water bodies and water bodies for cultural and domestic use. The presence of these substances is unacceptable.

Sulfates

These important anions are found in almost any body of water located on the surface. Sources of entry in nature are the oxidation of sulfur and sulfides, as well as chemicals. weathering and dissolution of gypsum and other sulfur-containing minerals.

2S + 3O 2 + 2H 2 O = 2H 2 SO 4;

2FeS 2 + 7O 2 + 2H 2 O = 2FeSO 4 + 2H 2 SO 4.

However, there are many other ways for sulfates to enter water bodies. Suppliers of these compounds are processes such as the death and oxidation of aquatic organisms, as well as substances entering the water with terrestrial plants and animals. They are carried in with underground runoff. They are carried out by wastewater from municipal and agricultural activities. Mine waters and industrial discharges (for example, after pyrite oxidation), where the use of sulfuric acid is necessary, are also rich in sulfate impurities.

The SO 4 2- form is inherent only in the ionic composition of water with low mineralization. With an increase in mineral saturation, sulfates tend to combine into stable associated neutral ion pairs (for example, CaSO 4, MgSO 4). Calcium sulfate is characterized by a relatively low level of solubility in water (L = 6.1.10-5 - product of solubility), as a result - with an insignificant concentration of calcium sulfate in water, sulfate ions are not detected in significant concentrations. The presence of other salt impurities and low calcium content can cause a significant increase in the concentration of dissolved sulfates in water.

In the multi-stage sulfur cycle, sulfates have a specific place. Sulfate-reducing bacteria (in the absence of oxygen) reduce these compounds to sulfides and hydrogen sulfide, which will be oxidized to sulfates as soon as the amount of oxygen increases again. Heterotrophic bacteria release sulfur, which is contained in the form of hydrogen sulfide in the proteins of dead living cells. Sulfates are filtered out of water by autotrophic organisms, such as trees, to be used to build proteins.

The content of sulfates varies for waters of different types of sources. Based on the results of the analysis, you can find:
Rivers and fresh lakes - 5-10 mg/dm 3 (sometimes the sulfate content can reach 60 mg/dm 3);
Rain water - 1-10 mg/dm3.
Samples taken from underground water sources tend to have much higher sulfite levels.

The concentration of sulfates often correlates with the total salt content of a reservoir and is subject to significant fluctuations depending on the current season. Of the factors involved in the formation of the sulfate regime, the most significant are changes in the ratio of surface and underground runoff. The balance of oxidative and reduction processes, as well as anthropogenic pollution of the reservoir and the content of organic substances, have a significant influence.

Oversaturation with sulfates worsens organoleptic characteristics. Such water is dangerous due to its physiological effects on the body. The obvious laxative effect characteristic of sulfates has become the reason for strict regulation of their maximum permissible concentrations (the limits are reflected in regulations). The taste threshold for magnesium sulfate is characterized by indicators of 400-600 mg/dm 3, for calcium sulfate - 250-800 mg/dm 3. The requirements for water used in steam power plants are particularly stringent (calcium, when interacting with sulfates, forms a difficult-to-remove sediment - scale). The presence of these compounds in water for industrial and drinking purposes can be beneficial, but can also be harmful.

MPC drinking water - 500 mg/dm 3 ;
Maximum permissible concentration for fish farms is 100 mg/dm3.

The influence of sulfates on corrosion processes has not been detected, however, concentrations above 200 mg/dm 3 are fraught with leaching of lead from lead pipes.

Carbon disulfide

A transparent substance with a pungent odor. Volatile liquid. A polytropic poison that causes both acute and chronic intoxication.

Impact results:

- Damage to the peripheral and central nervous systems;

- Impaired cardiovascular activity;

- Damage to the gastrointestinal tract;

- Disturbances in the exchange of nicotinic acid and vitamin B6.

One of the sources of this compound entering open water bodies is industrial discharges from factories producing silk from viscose, effluents from artificial leather factories, as well as waste from many other technological cycles. Carbon disulfide has a depressing effect on the development of microflora (saprophytic forms) even at a concentration of 30-40 mg/dm 3 . Fish are able to withstand 100 mg/dm3.

MPC of drinking water (organoleptic limit on the harmfulness indicator) - 1.0 mg/dm 3 ;
Maximum permissible concentration for fish farms (toxicological limit in terms of harmfulness) - 1.0 mg/dm 3 .

Dear sirs, if you have a need to correct sulfur-containing compounds to bring water quality to certain standards, please contact the company’s specialists Waterman. We will develop for you the optimal technological scheme for water purification.