Sulfur is one of the oldest pesticides used in horticulture. It began to be made in the 40s of the XX century. as a by-product in the purification of coke oven gases from hydrogen sulfide.

Application and purpose of fungicide Colloidal sulfur

Initially, sulfur was used to fight powdery mildew in cucumbers, but later it showed great effectiveness in the fight against other fungal diseases. In addition, colloidal sulfur inhibits the vital activity of ticks. She will not be able to completely destroy them, but will stop their spread. Until recently, sulfur was widely used to combat fungal diseases in vegetable bases, but now it has been replaced by more modern drugs. The effectiveness of sulfur is based on the vapors it emits. It is sulfur vapor that stops the development of fungal diseases, without penetrating into the plant. It is most effective against powdery mildew, rust and scab.

Ground sulfur is successfully used for grapes in the fight against oidium. This is a dangerous fungal disease of grapes that affects all green parts of the plant. When a plant is damaged, it becomes covered with a gray coating with an unpleasant fishy odor. Inflorescences dry up, fruits crack. To combat oidium, pollination with ground sulfur is used. At temperatures above 35 0 C, it is mixed with talc. Colloidal sulfur treatment is carried out four times per season. Starting from the appearance of the first leaves and ending with preventive treatment after harvest.

To destroy the keel in cabbage, the earth is shed with sulfuric solution when planting seedlings.

Ground sulfur has found its application for blueberries. For successful cultivation of this berry, acidic soils are needed. To acidify the soil for future plantings, it is necessary to add ground sulfur to the soil a year before planting blueberry seedlings at the rate of 250 g per 1 m 2 of land.

Sulfur is produced in the form of water-soluble granules or smoke grenades. The latter are conveniently used in basements or cellars to get rid of pathogens of fungal diseases.

Treatment with colloidal sulfur is best done in the morning or in the evening when it is calm. Do not use sulfur during the flowering period. Some cucurbits and gooseberry varieties are especially sensitive to the action of sulfur, they have burns on the leaves and their fall.

Attention! It is necessary to spray the leaves of plants from both sides, because. sulfur cannot accumulate in plants.

The protective effect of sulfur lasts for about 10 days, begins to act three to four hours after application. The last treatment with sulfur should take place no later than 3 days before harvest.

How to dilute colloidal sulfur: a package of sulfur (40 grams) is diluted in five liters of liquid. To make a solution, pour sulfur into the required volume of water with constant stirring until a homogeneous suspension is obtained. Sulfur solution is not stored, it must be used on the day of preparation.

Important! The temperature range for the use of sulfur is from +20 0 C to +35 0 C. Sulfur cannot be used during periods of drought and heat.

The mechanism of action of sulfur as a fungicide is that sulfur penetrates into the fungus, dissolves in the substance of its cell and combines with hydrogen, displacing oxygen, thus inhibiting the respiratory function of the cell, from which it dies. Sulfur cannot be used at air temperatures above 35 0 С, because this can lead to burns or leaf fall on plants. At temperatures below 20 0 C, the effectiveness of the drug is reduced to zero. The highest efficiency of sulfur occurs at temperatures up to 27 0 C. Sulfur should not be used simultaneously with other pesticides. It is compatible with many of them except ferrous sulfate and those containing mineral oils and phosphorus compounds. In the case of the latter, it is necessary to maintain a buffer interval - 2 weeks before the treatment of plants with pesticides with mineral oils and 2 weeks after.

Sulfur against powdery mildew

As soon as the first signs of disease of plants with powdery mildew appear, treatment should begin. Colloidal sulfur is used for strawberries and other berry crops, as well as fruit trees. Processing is carried out before flowering. As soon as flower stalks appear in strawberries, they should be treated with a solution of 10% karbofos and colloidal sulfur (50 g of sulfur solution per bucket). Depending on the crop, the treatment is repeated up to 6 times with a waiting time of 1 day.

Sulfur against ticks

Important! Ticks develop immunity to the same pesticide, so the means for their destruction must be alternated.

Unfortunately, colloidal sulfur is not able to completely rid plants of mites, so it is better to use it in combination with other drugs (for example, phytoverm, bitoxibacillin) and as a means of prevention.

Consumption rates

Observe the consumption rate indicated on the packaging.

The drug is diluted based on the calculation of 3:1 (g / l), for example, 30 g per 10 liters of water. Multiplicity of processing for a season no more than 5 times. The drug works for one and a half weeks. For processing fruit trees, the rate is increased to 80 g per 10 liters. To combat ticks, 10 g per 10 liters of water is enough.

For open ground cucumbers, the consumption rate is less than 20 g per 10 liters.

Precautionary measures

Colloidal sulfur belongs to the third hazard class. Before spraying crops with sulfur, pets and children should be isolated from the place of treatment. When treating with sulfur, it is necessary to completely protect the mucous membranes and skin from its ingress: use a protective bandage, goggles, protective clothing, rubber gloves and a headgear. After finishing the treatment, the protective equipment should be washed, hands and face should be washed with soap and the mouth should be rinsed.

Do not use food containers to prepare a sulfur solution. Experts recommend burying used containers in the ground after use away from residential buildings. In horticultural conditions, this is not easy to do, in which case it is recommended to clean the container as much as possible and store it separately from other containers. Do not use for other purposes. Opened packaging of sulfur must not be stored on the soil surface and thrown into the water, and must not be disposed of with household waste. Pack the used colloidal sulfur packaging as well as possible for its disposal.

First aid for poisoning

Sulfur is slightly toxic to humans: if it comes into contact with the skin, contact dermatitis may occur, inhalation of sulfur causes sulfuric bronchitis. If sulfur gets on the skin, they should be washed well with soap and water, if it gets into the eyes, rinse with plenty of water. If sulfur is swallowed, drink plenty of water with activated charcoal (1g:1kg person). For any sulfur poisoning, it is better to consult a doctor.

Storage

Sulfur is stored in dry rooms at a temperature not exceeding +30 0 C, away from food, out of reach of children and pets.

Attention! Sulfur must not be allowed to heat up!

Do not store sulfur in a place that can heat up in the sun, do not mix it with mineral fertilizers, and even more so with nitrogen-containing fertilizers. This may cause it to ignite.

Sulfur is widely distributed on Earth. Numerous deposits of sulfur in a free state are located in Mexico, Poland, on the island of Sicily, in the USA, the USSR and Japan. Sulfur deposits in Poland are the second in the world, they are estimated at 110 million tons and are almost as good as the Mexican ones. Deposits in Poland were fully evaluated only in 1951, development began in 1957. In 1970, 2.6 million tons were already produced, and then the annual production reached 5 million tons.

Sulfur is found in various minerals and can be found in seawater as sulfites. Plant and animal organisms contain protein-bound sulfur; in the coal, which is formed from plants, there is sulfur bound in organic compounds or in the form of compounds with iron (sulfur pyrite FeS2). Brown coal can contain up to 6% sulfur. The coal-processing industry of the GDR annually receives 100,000 tons of sulfur from the purification of coke, water and producer gas.

Dissolving sulfur

Sulfur vapor reacts with hot coal to form carbon disulphide CS2 (carbon disulfide), a flammable liquid with an unpleasant odor. It is indispensable in the production of rayon and staple. Sulfur, which, as is known, does not dissolve in water and dissolves in small amounts in benzene, alcohol or ether, is perfectly soluble in carbon disulfide.

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

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. Consider the main points regarding the structure, properties, production and use of this element. The characterization of sulfur will be presented in as much detail as possible.

Common features and differences of chalcogens

Sulfur belongs to the oxygen subgroup. This is the 16th group in the modern long-period form of the Periodic Table (PS). An obsolete version of the number and index is VIA. Names of the chemical elements of the group, chemical signs:

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

The outer electron shell of the above elements has the same structure. In total, it contains 6 which can participate in the formation of a chemical bond with other atoms. Hydrogen compounds correspond to the composition H 2 R, for example, H 2 S is hydrogen sulfide. The names of the 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 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 of 33, 34 and 36 are found in smaller quantities. Characteristics of sulfur by position in PS and atomic structure:

• serial number - 16;
• the charge of the nucleus of an atom 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 on 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 steady state is reached. in this case it drops to -2.

Physical properties of rhombic and monoclinic allotropic forms

Under normal conditions, sulfur atoms are connected to each other at an angle into stable chains. They can be closed in rings, which allows us to speak about the existence of cyclic sulfur molecules. Their composition reflect the formulas S 6 and S 8 .

The characterization of sulfur should be supplemented by a description of the differences between allotropic modifications with different physical properties.

Rhombic or α-sulfur is the most stable crystalline form. These are bright yellow crystals composed 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.

Obtaining amorphous sulfur

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

Solubility of sulfur

Some modifications in carbon disulfide, benzene, toluene and liquid ammonia. If organic solutions are cooled slowly, needle-like crystals of monoclinic sulfur are formed. When liquids evaporate, transparent lemon-yellow crystals of rhombic sulfur are released. They are brittle 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 can float on the surface (not wetted).

Chemical properties

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

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

Free sulfur in nature

In terms of prevalence in the earth's crust, sulfur is in 15th place among the chemical elements. The average content of S atoms in 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, when mining, beautiful druze and giant single crystals are found.

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 oil, gas, and natural water fields. Sulfur is part of coal. It is necessary for the construction of many organic compounds. When egg whites rot, hydrogen sulfide is released, which is why it is often said that this gas has the smell of rotten eggs. Sulfur is a biogenic element, it is necessary for the growth and development of humans, animals and plants.

Importance of natural sulfides and sulfates

The characterization of sulfur will be incomplete, if not to say that the element occurs not only in the form of a simple substance and oxides. The most common natural compounds are salts of hydrosulfide and sulfuric acids. Sulfides of copper, iron, zinc, mercury, lead are found in the minerals sphalerite, cinnabar and galena. Sulfates include sodium, calcium, barium and magnesium salts, which form minerals and rocks in nature (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, building materials. The medical value of some crystalline hydrates is great.

Receipt

A yellow substance in a free state occurs in nature at different depths. If necessary, sulfur is smelted from rocks, not by raising them to the surface, but by forcing superheated rocks to a depth. Another method is associated with sublimation from crushed rocks in special furnaces. Other methods involve dissolution with carbon disulfide or flotation.

The needs of industry for sulfur are great, therefore, its compounds are used to obtain elemental matter. 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. The determination of sulfur obtained by various methods sometimes gives low purity values. Refining or purification is carried out by distillation, rectification, treatment with mixtures of acids.

The use of sulfur in modern industry

Sulfur granulated is used for various production needs:

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

Toxicity of sulfur and its compounds

Dust-like 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, exhaust gases are not captured, then they enter the atmosphere. Combining with drops and water vapor, sulfur and nitrogen oxides give rise to the 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 crops.

To disinfect poultry houses, basements, vegetable stores, a 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, in the storage of vegetables and fruits. Sulfur preparations are used as pesticides to control diseases and pests of agricultural crops (powdery mildew and spider mites).

Application in medicine

The great healers of antiquity 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 with food becomes weaker, 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. Sulfur baths can relieve the pain of 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 crystalline substance. When used externally, this compound is incorporated into a skin care cosmetic.

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

Sulfur in history

Even in ancient times, a non-metallic yellow substance attracted the attention of a person. But it wasn't until 1789 that the great chemist Lavoisier established that powders and crystals found in nature were composed of sulfur atoms. It was believed that the unpleasant smell that occurs when it is burned, repels all evil spirits. The formula for sulfur oxide, which is obtained during combustion, is SO 2 (dioxide). It is a toxic gas and is hazardous to health if inhaled. Several cases of mass extinction of people by entire villages on the coasts, in the lowlands, scientists explain the release of hydrogen sulfide or sulfur dioxide from the earth 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 in the manufacturing process. The most important compound - sulfuric acid - also learned to use a very long time ago. In the Middle Ages, this substance was called vitriol oil, and salts were called vitriol. Copper sulphate CuSO 4 and ferrous sulphate FeSO 4 still have not lost their importance in industry and agriculture.

Sulfur is located in the VIa group of the Periodic system of chemical elements of D.I. Mendeleev.
The outer energy level of sulfur contains 6 electrons, which have 3s 2 3p 4 . In compounds with metals and hydrogen, sulfur exhibits a negative oxidation state of elements -2, in compounds with oxygen and other active non-metals - positive +2, +4, +6. Sulfur is a typical non-metal, depending on the type of transformation, it can be an oxidizing agent and a reducing agent.

Finding sulfur in nature

Sulfur occurs in the free (native) state and bound form.

The most important natural sulfur compounds:

FeS 2 - iron pyrite or pyrite,

ZnS - zinc blende or sphalerite (wurtzite),

PbS - lead gloss or galena,

HgS - cinnabar,

Sb 2 S 3 - antimonite.

In addition, sulfur is present in oil, natural coal, natural gases, in natural waters (in the form of a sulfate ion and causes the “permanent” hardness of fresh water). A vital element for higher organisms, an integral part of many proteins, is concentrated in the hair.

Allotropic modifications of sulfur

Allotropy- this is the ability of the same element to exist in different molecular forms (molecules contain a different number of atoms of the same element, for example, O 2 and O 3, S 2 and S 8, P 2 and P 4, etc.).

Sulfur is distinguished by its ability to form stable chains and cycles of atoms. The most stable are S 8 , which form rhombic and monoclinic sulfur. This is crystalline sulfur - a brittle yellow substance.

Open chains have plastic sulfur, a brown substance, which is obtained by sharp cooling of the sulfur melt (plastic sulfur becomes brittle after a few hours, turns yellow and gradually turns into rhombic).

1) rhombic - S 8

t°pl. = 113°C; r \u003d 2.07 g / cm 3

The most stable version.

2) monoclinic - dark yellow needles

t°pl. = 119°C; r \u003d 1.96 g / cm 3

Stable at temperatures over 96°C; under normal conditions, it turns into a rhombic one.

3) plastic - brown rubbery (amorphous) mass

Unstable, when hardened, turns into a rhombic

Sulfur recovery

1. The industrial method is the smelting of ore with the help of steam.
2. Incomplete oxidation of hydrogen sulfide (with a lack of oxygen):

2H 2 S + O 2 → 2S + 2H 2 O

1. Wackenroder reaction:

2H 2 S + SO 2 → 3S + 2H 2 O

Chemical properties of sulfur

Oxidizing properties of sulfur
(S 0 + 2ē→ S -2 )

1) Sulfur reacts with alkaline without heating:

S + O 2 – t° → S +4 O 2

2S + 3O 2 - t °; pt → 2S +6 O 3

4) (except for iodine):

S + Cl2 → S +2 Cl 2

S+3F2 → SF6

With complex substances:

5) with acids - oxidizing agents:

S + 2H 2 SO 4 (conc) → 3S +4 O 2 + 2H 2 O

S + 6HNO 3 (conc) → H 2 S +6 O 4 + 6NO 2 + 2H 2 O

Disproportionation reactions:

6) 3S 0 + 6KOH → K 2 S +4 O 3 + 2K 2 S -2 + 3H 2 O

7) sulfur dissolves in a concentrated solution of sodium sulfite:

S 0 + Na 2 S +4 O 3 → Na 2 S 2 O 3 sodium thiosulfate

SULFUR

Dissolving sulfur

Sulfur, which, as is known, does not dissolve in water and dissolves in small amounts in benzene, alcohol or ether, is perfectly soluble in carbon disulfide cs2.

If a solution of a small amount of sulfur in carbon disulfide is slowly evaporated on a watch glass, then we 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 we will put out all the burners and put the watch glass under draft or in front of the window.

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

Obtaining hydrogen sulfide and experiments with it

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

fes + 2hcl = h2s + fecl2

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

Extreme care must be taken when working with hydrogen sulfide, since 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 reactive paper. To obtain it, we moisten filter paper with a dilute solution of lead acetate or lead nitrate, dry it and cut it into strips 1 cm wide. Hydrogen sulfide interacts with lead ions, resulting in the formation of black lead sulfide. In this way, hydrogen sulfide can be detected in spoiled food (eggs, meat).

We recommend to obtain hydrogen sulfide by the dry method, since in this case the gas flow can be easily regulated 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 mass until it solidifies. Grind the solid mass and save for further experiments.

When it is necessary to obtain hydrogen sulfide, several pieces of a mixture of paraffin and sulfur are heated 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, the 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 get sulfides

To consider 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 fall out if an alkaline environment is created in the solution (for example, by adding ammonium hydroxide). In a hydrochloric acid solution, sulfides of lead, copper, bismuth, cadmium, antimony and tin will precipitate.

Burning hydrogen sulfide

Having made a preliminary test for explosive gas, we set fire to hydrogen sulfide coming out of a glass tube drawn at the end. Hydrogen sulfide burns with the appearance of a pale flame with a blue halo:

ЗН2s + ЗО2 = 2h2o + 2so2

As a result of combustion, sulfur oxide (iv) or sulfurous gas is produced. It is easily identified by its pungent odor and the redness of wet blue litmus paper. With insufficient access to oxygen, hydrogen sulfide is oxidized only to sulfur. Active 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 that air and hydrogen sulfide are passed through activated carbon in a ratio of 1: 3. Yellow sulfur will be released on the coal.

Active carbon can be purified from sulfur by washing it in carbon disulfide. In engineering, ammonium sulfide solution (nh4)2s is most often used for this purpose.

Experiments with sulfurous acid

Sulfur oxide (iv) - sulfur dioxide - is extremely soluble in water, as a result of which sulfurous acid is formed:

h2o + so2 = h2so3

It kills microbes 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. Spots

From blueberries, for example, they are removed if a moistened contaminated place is kept in the "fumes" of burning sulfur for a long time.

Let's check the bleaching effect of sulfuric acid. To do this, the cylinder, where pieces of sulfur burned for some time, we lower various colored objects (flowers, wet pieces of cloth, important litmus paper, etc.), close the cylinder well with a glass plate and wait for a while.

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

h2o + so3 = h2so4

When sulfur is burned under normal conditions, sulfur oxide (iv) is always obtained. And if a certain amount of sulfur oxide (vi) is formed, then most often it immediately decomposes under the action 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 experience "Obtaining sulfuric acid)

Getting sulfuric acid

chamber method

Let us fill a large vessel (500 ml round-bottom 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 obtained relatively easily by dropping concentrated sulfuric acid into a concentrated solution of sodium sulfite na2so3. In this case, sulfuric acid, as a stronger one, 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 (iv) is formed:

4hno3 + Cu = cu(no3)2 + 2h2o + 2no2

The acid concentration should be about 60% (mass.). Attention! no2 - strong poison!

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

Insert a short piece of tube with a Bunsen valve into the third hole - a short piece of rubber hose with a slot. First, let's create a strong influx of oxy-nitrogen 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 color change will indicate that the reaction has begun. Under the action of water vapor, nitric oxide (iv) oxidizes sulfur oxide (iv) to sulfur oxide (vi), which immediately, interacting with water vapor, turns into sulfuric acid:

2no2 + 2so2 = 2no + so3

A colorless condensate will collect at the bottom of the flask, and the excess gas and vapor will escape through the Bunsen valve. We pour the colorless liquid from the flask into a test tube, check the acid 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 the success of the experiment.

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

contact method

In the production of sulfuric acid, various cheeses are used. 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 kiln or stacked kiln, pyrite reacts with atmospheric oxygen according to the following equation:

4fes2 + 11О2 = Зfe2o3 + 8so2

The formed oxide of iron (iii) is removed from the furnace in the form of scale and processed further at enterprises for the production of pig iron. Crush a few pieces of pyrite in a mortar and place them in a refractory glass tube, which we close with a cork with a hole. Then, with a burner, we heat the tube strongly, at the same time passing air through it with the help of a rubber bulb. In order for the flying dust from the roasting gas to settle, we will take it into an empty glass vessel, and from it into the second refractory tube, in which there is a catalyst heated to 400-500 ° C. In technology, vanadium oxide (v) v2o5 or sodium vanadate navo3 is most often used as a catalyst, and for this purpose we will use red iron oxide (iii) fe2O3. We apply finely ground iron oxide to glass wool, which we distribute in a tube with a layer 5 cm long. We heat the tube with the catalyst until red heat begins. 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. Let us collect the so2 in an empty flask and, shaking it vigorously, mix it with a small amount of water. We get sulfuric acid - we prove its presence, as in the previous method.

You can also place the catalyst separated by glass wool in one of the glass tubes. You can also work in a test tube with a side arm. We put pyrite on 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 come close to the catalyst. On the side outlet we will fix 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 sulfuric acid sulfite or hydrosulfite, 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, it is possible to impregnate a clay shard with a solution of iron (ii) sulfate and then ignite it strongly. At the same time, a fine powder of iron oxide (iii) is formed on clay.

Gypsum acid

If there are few metal sulfides (as, for example, in Germany), anhydrite caso4 and gypsum caso4-h2o can serve as starting products for the production of sulfuric acid. 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 also be important in the future, since sulfuric acid is the most common chemical product. Sulfates can be decomposed by applying high (up to 2000 °C) temperature. Müller found that the decomposition temperature of calcium sulfate could be lowered to 1200°C by adding finely ground coke. First, at 900 °C, coke reduces calcium sulfate to sulfide, which, in turn, interacts with undecomposed sulfate at a temperature of 1200 °C; this produces sulfur oxide (iv) and quicklime:

caso4 + 2c = cas + 2co2

cas + 3caso4 = 4cao + 4so2

Calcium sulfate can be decomposed in laboratory conditions only when an appropriate high temperature is applied. We will work with equipment similar to that which was used in the firing of pyrite, only we will take a porcelain or iron tube for combustion. Close the tube with stoppers wrapped in asbestos cloth for thermal insulation. We insert a capillary into the hole in the first stopper, and into the second - a simple glass tube, which we will connect: with a washing bottle half-filled with water or a solution of fuchsin.

The reaction mixture is prepared as follows. We crush in a mortar 10 g of gypsum, 5 g of kaolin (clay) and 1.5 g of active powdered coal. Dry the mixture by heating for some time at 200 °C in a porcelain cup. After cooling (preferably in a desiccator), we introduce the mixture into the middle of the combustion tube. At the same time, we pay attention to the fact that it does not fill the entire cross section of the tube. Then we heat the tube strongly with the help of two burners (one from below, the second obliquely from above) and, when the tube heats up, we pass a not too strong air flow through the entire system. Already after 10 minutes, due to the formation of sulfurous acid, the fuchsin solution in the wash bottle will discolor. Turn off the water jet pump and stop heating.

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

In technology, they work with a mixture of anhydrite, coke, clay, sand and pyrite cinder fe2o3. The worm conveyor delivers the mixture to a 70-meter rotary kiln, where pulverized coal is burned. The temperature at the end of the furnace, at the place of combustion, is approximately 1400 °C. At this temperature, the quicklime formed during the reaction is fused with clay, sand and pyrite cinder, resulting in 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 conduct 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 installation as for the decomposition of gypsum, but this time we will take a tube of refractory glass. The reaction mixture is obtained 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, which 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 important for the construction industry, such as cement clinker and xylolite, makes the production of sulfuric acid from local raw materials particularly economical. The processing of intermediates and by-products into valuable raw materials or final products is an important principle of the chemical industry.

Get Xylolite

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