Quicklime: the formula requires detailed familiarization. Quicklime formula

The history of the use of lime has more than a dozen centuries. This material has firmly taken its place in the most diverse spheres of human activity. The product has a mass useful characteristics, while the raw material itself is affordable, and the manufacturing technology is quite simple. Today, over 1 million tons of lime are produced annually in our country. It is the main component of building mixtures, used in horticulture, medicine and in everyday life.

Features and manufacture

Lime is a special material. It is made by roasting and processing chalk, shell rock, as well as limestone and other carbonate-containing natural rocks. Fossils are processed in furnaces under the influence of temperatures from +1000 to +1300 degrees. Rock blocks are transformed into pieces of various sizes and shapes, which are further processed without the participation of chemical reagents and catalysts. The output is a completely natural material, consisting of 100% natural components. In lime, a small presence of clay impurities and mineral additives is allowed.

Composition and properties

In its pure form, building lime is a colorless and odorless material that is very poorly soluble in water.

There are several types of lime.

• Hasted. The chemical formula is Ca(OH) 2. It is divided into powdered fluff and lime dough.
• Quicklime. This composition with the CaO formula can be conditionally divided into ground and lumpy, depending on the processing method.
• Chloric. The formula looks like Ca(Cl)OCl. It is considered an excellent antiseptic.
• Soda. This type is represented by a mixture of slaked lime and NaOH (caustic sodium soda). It is used narrowly, where neutralization of carbonic acid is required.

Products containing basic component lime is characterized by increased strength, water resistance and density.

The advantages of the material include:

• hygroscopicity - lime is resistant to moisture, does not pass liquid and does not change its properties under the influence of adverse external conditions;
• disinfection - it is an antiseptic, all bacteria that get on the lime surface die, the composition is an unfavorable environment for the appearance of mold and fungi;
• no unpleasant odor;
• versatility - its technical characteristics are high, it can be used on old coatings, as well as on freshly painted surfaces;
• resistance to UV rays;
• good interaction with the coloring composition;
• low price.

Lime has some disadvantages.

• The likelihood of streaks, streaks and bubbles. This happens in cases where all the rules for diluting the composition are not followed: a solution that is too thin will not give the desired shade, and too thick will begin to crumble and turn into bubbles as it dries.
• The material is very corrosive. It requires compliance with safety regulations when working with the material, its storage and transportation.

Varieties

The processing technology of natural raw materials determines the division of building lime into two types:

• quicklime containing CaO;
• slaked (hydrated), the main component of which is Ca (OH) 2.

The salient features of fatty lime are:

• high quenching speed;
• heat release;
• composition plasticity.

Such material is added to mortars to increase the elasticity of the mixture and ease of use. Skinny composition has great speed quenching, and much less heat is released. As a result of processing, the composition is granular and heterogeneous, and the dough itself has low plasticity.

Lime, which tends to harden in air, is called air lime. A mixture that can solidify both in air and in water is called hydraulic. In air lime, up to 12% of the composition falls on silicates and calcium aluminoferrite, in rare cases this figure reaches 20%. Such a mixture is widely used for painting porous surfaces of concrete, brick, plaster and natural stone. The percentage of impurities in hydrate compositions is more than 25% and reaches 90%. They are common in working with surfaces that are constantly exposed to moisture.

According to the parameters of the oxide in the composition of lime, it is possible to conditionally distinguish:

• calcium - contains up to 2% MgO;
• low magnesia - contains 2–5% MgO;
• magnesia with a magnesium oxide content of 5–20%;
• dolomitic, including 20–40% of this component.

Depending on the type of processing of natural raw materials, they are conditionally distinguished the following options air lime:

• quick-cooked lump or boil, which for the most part consists of Ca (OH);
• ground quicklime - this is the material obtained as a result of crushing lump lime, it has a powdery structure;
• slaked lime is formed when lump lime is slaked;
• a lime body is another material produced as a result of the quenching of a lumpy composition with a pasty structure;
• milk of lime is lime of a light shade, calcium hydroxide is present in it both in a dissolved state and in the form of particles.

According to the rate of quenching, the material is divided into three types:

• quick-extinguishing (extinguishing speed no more than 8 minutes);
• medium extinguishing (reaction time is from 8 to 25 minutes);
• slow extinguishing (requires 25 minutes or more)

According to the type of use, bleaching, technological and other types of lime are distinguished. In addition, any lime is conditionally divided into composition with and without impurities.

Slaked and quicklime: the difference

Slaked and quicklime varieties are substances that differ in their chemical composition. Quicklime is calcium oxide, and slaked is its hydroxide, it is obtained as a result of quenching with water. By the way, during storage, quicklime gradually absorbs moisture from the air and slowly turns into slaked lime.

The scope of their application also differs. Quicklime is a component of dry building mixes, and is also used for the production of sand-lime bricks. Hydrated lime is used for painting and plastering as a binder.

Quicklime has several advantages:

• does not generate waste during operation;
• low degree of liquid absorption;
• the possibility of operation at sub-zero temperatures;
• high strength;
• wide range of uses.

Along with the advantages, the quicklime mixture also has a significant drawback - it is dangerous to health, is a caustic composition, and leads to burns. skin and mucous membranes. Working with it requires caution, the room must be ventilated, and it is also advisable to use goggles, a respirator and gloves.

How to determine which lime is in front of you - slaked or not.

• This information must be indicated on the packaging.
• Mixtures can be distinguished by touch. When touched, quicklime material feels warm, but slaked lime has a normal temperature.
• Quicklime is most often pebbles and lumps, and the slaked mixture is sold in a powdered state.
• You can check the composition with water. When liquid gets on quicklime, a reaction immediately begins, heat and gas are intensively released, and splashes fly in all directions.

Application

Lime compositions have a fairly wide scope of use.

• For disinfection of premises. After processing, fungi and mold do not form on the walls and on the ceiling.
• As a heater in private housing construction. When fluff is combined with gypsum and sawdust, an inexpensive environmentally friendly insulation is obtained, they fill voids. As it hardens, a film forms on the surface, which creates the effect of thermal protection, but does not interfere with air ventilation.
• When laying bricks. In combination with gypsum, lime compositions contribute to increased adhesion of surfaces, ahead of cement mortars in this parameter.

Slaked and quicklime have their own characteristics of use. Quicklime is used in construction. For a long time, cement was produced from it, which hardens quite well and ensures the adhesion of the coating. However, lime absorbs moisture, so mold begins to appear in the walls. This feature led to the gradual abandonment of the use of quicklime in construction.

Today, this composition is an active component of plaster, slag concrete and paints. Quicklime is used in the cold season, because when it is slaked, strong heat is released, which creates the desired temperature during hardening.

Advice: you can not use quicklime for finishing stoves, fireplaces and heated surfaces, because under the influence of high temperatures, lime emits CO2 - carbon dioxide, dangerous to human life and health.

Separately, it is worth mentioning the use of limestone in agriculture, since not a single gardener can do without it. Lime fertilizers include lake lime, marl, dolomite flour and tuff, which are produced by processing quicklime with fluff. These fertilizers are intended for painting trees (for this you need to dilute 1 kg of the composition in 4 liters of water) and spraying plants (lime water is mixed with copper sulphate).

How to extinguish?

Lime slaking takes place in accordance with the chemical formula: CaO + H2O \u003d Ca (OH) 2 + 65.1 kilojoules. To do this, limestone powder is dissolved in water, which reacts with calcium oxide. During the reaction, an active release of heat is noted, as a result, water passes into a gaseous state. The released vapors loosen the rock, the lumps are converted into a fine powder.

If during the slaking process, water is added to lime in the amount of 70-100% of its total weight, then a hydrate composition (fluff) is obtained. It is produced in factory conditions thanks to specially equipped hydrators. If limestone and water are taken in a ratio of 3: 1, then lime paste is obtained, which is used on construction sites. Keeping the mixture in a special pit for 2 weeks, it acquires a special plasticity.

During the quenching process, not a single metal oxide should remain in the limestone, otherwise the quality of the mixture will be quite low. For effective extinguishing, at least a day is required. It is optimal if this process takes 36 hours.

The main stages of extinguishing:

• limestone is poured into a container - metal containers are allowed, but they should not contain rust;
• the powder is poured with water (at the rate of 1 kg of the composition per 0.5 l for making lime dough, and 1 liter of water to create fluff); if lime is slow-extinguishing, then it is advisable to pour water in several passes;
• the mass is thoroughly mixed, it is advisable to repeat this procedure several times to prevent a decrease in steam release.

Work should be carried out with the utmost care. When quenching, the solution heats up to +150 degrees, the boiling composition actively boils and splashes. The first 30 minutes of extinguishing the mass should be stirred with a special wooden stick, so wear protective clothing to avoid accidents. After the quenching is completed, the container is closed with a lid and left for at least 2 days. It is optimal to let it "brew" for 2-3 weeks, it is during this time that the composition acquires the most effective disinfectant characteristics.

Lime is diluted with water in proportions that differ depending on the purpose of the composition. If the mixture is prepared for whitewashing walls and ceilings, then raw materials and water should be mixed in proportions of 1: 2 (2 liters of water are taken per 1 kg of limestone). The solution is left for two days, after which it is filtered. To process tree trunks, 4 liters of water are taken per 1 kg of powder, the mixture also requires infusion for 24 hours. For spraying plants, limestone is diluted in a large amount of water with copper sulphate, the resulting solution can be used after an hour.

Remember: during the preparation of slaked lime, you must not bend over the container, otherwise caustic fumes will cause burns to the skin, eyes and respiratory organs.

• so that the coating is more durable, and the plaster layer does not swell, wallpaper paste or latex-based paint is added to lime milk (up to 10-15% of the total weight of the mixture);
• in the manufacture of a mixture for whitewashing, a tablespoon of liquid green soap can be added to the milk solution - this provides a more dense sticking of the composition to the bark of trees;
• it is worth adding natural drying oil to decorative whitewash (1/3 tsp per 1 liter of composition or 5 g of salt), which will make the coating resistant to external adverse influences;
• if you add a little blue to the whitewash, it will give a slight bluish tint - this property is often used in the preparation of solutions for covering the ceiling;
• coloring lime compounds are best used in cold or damp rooms.

Storage and safety

When working with lime, compliance with safety regulations is required:

• mixing of the compositions is carried out only in a metal container;
• it is required to use personal protective equipment for the face, eyes, hands and respiratory organs;
• direct quenching begins 10-20 minutes after adding water to the lime, during the reaction an intense release of steam occurs, so it is not recommended to lean over the container and check the consistency of the mixture with your hands;
• when the material interacts with water, a specific smell is released, all work is best done in a ventilated room or in the fresh air.

There are some features of the storage of lime compositions. It is necessary to provide waterproofing of lump lime, since this substance can extinguish even the moisture contained in the air. If the mixture is stored in a paper bag, then its shelf life is short, since it loses its performance properties a month after unpacking. In the room where lime is stored, wooden floors should be equipped, raised at least 30 cm from the ground.

Remember: violation of storage rules is dangerous not only by the loss of consumer properties, the reaction of lime can lead to fire if there are electrical appliances and easily melting materials near the storage place. Do not forget that in case of fire, it is unacceptable to use water to extinguish.

Help with burns

Lime burn is a chemical skin lesion that is fraught with the most unpleasant consequences. Quicklime is an alkali that emulsifies and dissolves sebum, penetrating into the deep layers of the epidermis. Outwardly, the burn looks like a complex tissue necrosis of an off-white shade with the formation of loose scabs. When it comes into contact with the skin and mucous membranes, alkali penetrates in all directions, so the lesion is much larger than the zone of contact with lime. Damaged tissues partially lose their ability to regenerate and wounds heal for a very long time.

In case of injury, medical assistance should be provided immediately. It is necessary to promptly call a doctor, but for now she is going to try to improve the condition of the victim. If slaked lime has come into contact with the skin, then the affected areas should be washed with cold water for at least 15 minutes, and then treated with chamomile infusion or anti-inflammatory ointment.

But if a burn occurs with a quick-burn composition, then it is strictly forbidden to rinse the skin with water, because this can aggravate the situation and cause irreparable damage to health. Most of the substance will come out with tears, and its remnants must be removed with a cotton cloth and smeared with oil or fat. By the way, this is the only type of chemical damage when their use is allowed. For any other types of damage, such reagents are strictly prohibited. The wound should be covered with a sterile cloth, and then immediately go to the hospital.

The situation is more complicated in case of lime getting into the eyes. It causes quite dangerous consequences, up to partial or complete loss of vision. Small and medium fractions are not so dangerous, they can only cause conjunctivitis. Large parts literally stick to the mucous membrane of the eye and actually corrode them, penetrating inside and causing sharp pain, burning and spasm of the eyelids.

First aid includes:

• instillation of disodium salt, which binds metal ions;
• the use of painkillers, including local ones.

Lime refers to materials with astringent properties.

It is mined by roasting and further processing of carbonate rocks of fossils.

Lime in a wide variety of manifestations is used in almost all areas of human activity. What is quicklime. The formula of this substance is also indicated.

Quicklime is a white substance with a crystalline structure.

The formation of this material occurs in the process of firing chalk, limestone, as well as dolomites or any other minerals related to calcium-magnesium rock.

The amount of impurities in such material cannot exceed 6-8%. The quicklime formula is described as follows: CaO, however, magnesium oxides and other chemical compounds may be included in the composition of this substance.

This material is produced in accordance with the established GOST 9179-77. The substance is produced from carbonate rocks with a certain mineral content.

In accordance with the requirements of the established state standards, lime must be crushed to such a fraction that the number of large fragments after screening does not exceed 1.5-15%.

A substance such as quicklime is related to the second class of danger. Hydrated lime belongs to grades 1 and 2.

Varieties

What mixtures contain quicklime. The formula and application of this substance are interdependent.

Lime used as a building material is divided into 2 types: hydraulic and air.

Air lime allows concrete to harden under normal conditions. The hydraulic substance can perform binding properties even in aquatic environment, therefore, such material is often used for the construction of bridge piers.

Processing features divide the material into several subspecies:

• Lump lime is produced in the form of a mixture of lumps differing in size. The substance often consists of calcium oxides. Most of it contains magnesium. Also, aluminates, silicates, or ferrites, which are formed during the firing process, can be included in the composition of the material. Such a substance does not apply to astringent elements.
• Ground lime is produced by the lump grinding method, so the composition of these two varieties is the same. Such a substance is used in a quick form, so that the hardening process can be accelerated and the formation of waste can be avoided. Calcium chloride is added to improve hardening. If you need to slow down this process, sulfuric acid or gypsum is added to the composition of lime. Material is transported in metal and paper containers. You can store this material for about 10-15 days.
• Hydrated lime is formed during the slaking process. The composition of such material includes magnesium and calcium hydroxides, carbonate and other components.
• Lime dough is formed with the addition of water in an amount sufficient for the oxides to become hydrates.

Quicklime and slaked substance is the most popular today.

Production

Pure quicklime is rare today, despite the long history of the use of this substance in many industries.

The production of such a building material implies the course of a specific chemical process.

Lime is produced by several methods:

• Thermal decomposition of the rock is considered a traditional and rather expensive method, which requires special equipment. Its main disadvantage is the release of a small amount of carbon dioxide.
• Treatment of calcium salts, which include various acids. This is an alternative technique that is becoming increasingly popular today. During the firing process, a lot of oxygen is not consumed, so the substance is environmentally friendly.

Special equipment is used for heat treatment of raw materials. The developed modern technological devices allow the use of less expensive and harmful methods of extraction of quicklime.

Consider several types of modern furnaces:

• The most popular is the so-called mine stove, which consumes gas. Thanks to this device, lime of good quality is produced at an affordable cost.
• Installations operating on the pouring principle come across much less frequently. Coal is used for heating. This is considered the most economical and productive method, the main disadvantage of which is a large amount of emissions into the environment.
• The rotary kiln makes it possible to produce high-quality lime, but the production cost is relatively high.
• The design of the stove with a removable firebox allows you to get pure lime with a minimum amount of all kinds of impurities. The stove can run on solid fuel, and in terms of performance it is quite comparable with analogues.
• Ring and floor units are practically not used because their performance is very low. Old products are still in use, but modern equipment is gradually pushing them out of the market.

Specifications substances are determined by the established state standard quality. The manufactured product belongs to the 2nd category of chemical hazard.

Application

As mentioned above, in a wide variety of areas of activity, such material as quicklime is used. The formula and the production of this substance in large quantities make it affordable and practical to use. The largest consumers of such material include:

• Metallurgy industry.
• Sugar production.
• Agriculture.
• Chemical industry.

CaO is naturally used even in the construction industry. In the field of ecology, such a chemical compound is of great importance. The substance is used to clean flue gases from the sulfur and oxide contained in them. This combination promotes precipitation. organic matter in water and its subsequent softening.

The use of quicklime contributes to the neutralization of the components in Wastewater Oh. If lime comes into contact with the soil, the acidity level decreases, growing conditions cultivated plants are improving. Quicklime helps to increase the level of calcium in the soil. Thus, the cultivation of the land is greatly facilitated, the process of decay of humus is significantly accelerated.

How to extinguish lime - on the video:

Some of the materials used today in various fields have been known for a long time, and their properties, as a rule, were determined quite by accident. Lime is one of these materials. By this word, which comes from the Greek "asbestos", which means "inextinguishable", they mean quicklime, which is successfully used today in many industries.

Peculiarities

Quicklime is a product of roasting rocks mined in special mines. A special furnace is used as a tool, and the materials used to obtain the final product are limestone, dolomite, chalk and other rocks of the calcium-magnesium type, which are sorted by size and crushed before firing if the particles exceed the allowable dimensions.

The design of the furnaces used for roasting rock can be different, but the ultimate goal is always the same - to obtain material suitable for further use.

The shaft type furnace, where gas is used as fuel, is one of the most popular designs. The reason for their popularity is quite banal: the cost of processing the material is low, and the final product is of very good quality.

Furnaces that use coal as fuel and the firing process is based on the pouring principle of operation are gradually becoming a thing of the past. Although this method of processing the material is more economical and productive, but due to emissions into the environment, it is becoming less and less common.

Due to the high cost of the firing process, even more rarely are kilns with a rotating design that allow you to get the final product. highest quality. Remote fired kilns ensure purity and a minimum percentage of impurities in the final firing product. This type of furnace, in which solid fuel is used for heating and maintaining the temperature, has a small power compared to similar designs, therefore it is not widely used.

The type of ring and floor ovens was developed a very long time ago. Compared to more modern designs, they have lower productivity and consume more fuel during processing, so they are gradually being phased out of production, replacing more perfect species ovens.

The substance obtained as a result of firing has a white tint and a crystalline structure with a small proportion of impurities. As a rule, their value does not exceed 6-8% in the total mass. The generally accepted chemical formula for quicklime is CaO, or calcium oxide.

The composition of the substance may also include other compounds, most often it is magnesium oxide - MgO.

Specifications

Any materials extracted from nature and subjected to industrial processing have a certain standard, and quicklime is no exception. For quicklime, which belongs to the second hazard class used in construction, there is a quality standard - GOST No. 9179-77, which clearly spells out the physical and chemical parameters of this material.

According to the prescribed requirements, the lime particles after grinding must have a certain size. To determine the degree of grinding, a sample is taken and sifted through sieves with different cells. The amount of sifted lime is expressed as a percentage. When passing through a sieve with cells No. 02, 98.5% of the substance from total weight samples, and for a sieve with smaller cells No. 008, 85% of the substance is allowed to pass.

According to technical requirements, additives are allowed in lime. This composition is divided into two grades: the first and second. Pure lime is characterized by three grades: the first, second and third.

To determine the grade of lime, indicators are used: active CO + MgO, active Mg, CO2 level and unextinguished grains. Their number is indicated as a percentage, the numerical indicator of which depends on the variety, the presence or absence of additives in the samples, as well as on the breed. If, according to some indicators, the lime sample corresponds to different varieties, then the indicator with the value corresponding to the lowest grade is taken as the basis.

For carrying out chemical analysis, as well as determining the physical and mechanical properties of samples, they rely on GOST-22688.

Advantages and disadvantages

Like any other material, lime has its advantages and disadvantages. As a rule, it is compared with slaked lime. The main advantage of the material is a wide range of applications and a fairly low cost of the final product. When working with this material, regardless of the industry, there is no waste, which is very beneficial from an economic point of view.

The material perfectly absorbs moisture, which allows it to be successfully used as an additional element in the preparation of mortars and concrete mixtures to increase their density and strength. Release of material during hydration a large number thermal energy allows solutions, which include quicklime, to harden more evenly, and, as a result, have improved strength indicators of the formed surface.

The only disadvantage of this material is its high toxicity.

How is it different from slaked?

Slaked lime is a modified quicklime product, it is obtained by adding water to the original composition. As a result of a chemical reaction occurring according to the CaO + H? O → Ca (OH) ? type, a significant amount of thermal energy is released into the surrounding space, and calcium oxide is converted into calcium hydroxide.

The two types of lime also differ in other parameters, namely, in the percentage of indicators specified in GOST No. 9179-77 and the number of varieties. Slaked (hydrated) lime is characterized by 2 grades.

The values ​​of the indicator of active CO + MgO differ in two types of lime. For slaked lime without additives, depending on the variety, their quantitative content ranges from 70-90% (for calcium composition) and 65-85% (for magnesian and dolomite), and in slaked lime they are only 60-67%. In compositions with additives, active CO + MgO in calcium, magnesia and dolomite mixtures of quicklime are in the range of 50-65%, and in hydrated this indicator is only 40-50% lower.

Such an indicator as active MgO is completely absent in hydrated lime. In quicklime, this figure varies depending on the origin of the material. In calcium lime, it is only 5%, in magnesian lime - 20%, and in dolomite - 40%.

The level of CO in quicklime without additives is in the range of 3-7% (for a calcium mixture) and 5-11% (for magnesia and dolomite), in the hydrate composition the indicator does not exceed 3-5%. In compositions with additives, the level of CO? somewhat reduced. For calcium lime, it is in the range of 4-6%, for the other two types of quicklime - 6-9%. In the hydrate composition, the level of CO? – from 2 to 4%.

The indicator of not extinguished grains is relevant only for quicklime. For the first grade of calcium lime, 7% of a substance not participating in the reaction is allowed, 11% for the second and 14%, and in some cases 20% for the third grade. For the magnesian and dolomite composition, this figure is slightly higher. In the first grade, 10% is allowed, in the second - 15%, and in the third - 20%.

Kinds

Quicklime is classified according to many indicators, allowing it to be divided into different subspecies. According to the degree of grinding of particles, there are lumpy and ground lime. Lumps are characteristic of the lumpy appearance various shapes, fraction and size. In addition to calcium oxides, which are the main component, and magnesium oxide, which is present to a lesser extent in the composition, there may be other additives in the mixture.

Depending on the degree of burning of the lumpy material, medium burnt, soft burnt and hard burnt lime are distinguished. The degree of firing of the material subsequently affects the time taken for the quenching process. During the firing process, the composition is enriched with aluminates, silicates and magnesium or calcium ferrites.

The degree of roasting is affected by the time the product is in the kiln, the type of fuel and temperature. With the pouring firing method, where coke is used as a fuel, and the temperature in the furnace is maintained at a level of about 2000 ° C, carbide (CaC?) is obtained, which is subsequently used in various fields. Lump lime, regardless of how and to what extent it was calcined, is an intermediate and therefore undergoes further processing: grinding or slaking.

The composition of the ground mixture is not much different from the lumpy one. The difference lies only in the size of the lime particles. The grinding process is used for more convenient operation of calcium oxide. Crushed granulated or ground quicklime reacts faster with other components compared to the lumpy type.

According to the degree of grinding of particles, crushed and powdered lime are distinguished. Crushers and mills can be used for grinding, depending on the required particle sizes. When choosing mills and grinding schemes, they are guided by the degree of lime roasting, and also take into account the presence of solid inclusions and flaws in the firing process (underburning or overburning). Particles of material burned to a high or medium degree are crushed by impact and abrasion in special containers of ball mills.

Lumpy mixture is used to obtain different types of slaked lime. The quenching process (inorganic chemistry) occurs very rapidly, water boils during the reaction, so the lumpy mixture is called "boiling". Different percentages with water give compositions of different consistency. There are three types of slaked lime: limestone milk, limestone dough and hydrated fluff.

Limestone milk is a suspension, where a fraction of the particles are dissolved, and the other is in suspension. To obtain such a consistency, water is required in excess, as a rule, 8-10 times more than the mass of the product.

To obtain lime dough, less water is required, but its amount is still several times greater than the mass of lime prepared for slaking. As a rule, in order to obtain the desired pasty consistency, water is added to the product, which is 3-4 times larger than the main substance by weight.

A powder mixture or hydrate fluff is prepared in a similar manner, but the amount of added water is less than for a pasty or liquid composition. Fine powder or fluff, depending on the percentage in the composition of aluminoferrites and silicates, is divided into air and hydraulic types of lime.

The time required for the slaking reaction makes it possible to classify quicklime into fast-slaking, medium-slaking and slow-slaking. The quick-extinguishing type includes compositions, the conversion of which takes no more than 8 minutes. If the quenching reaction takes longer, but the transformation does not last longer than 25 minutes, then such a composition is classified as a medium quenching type. If the quenching reaction takes more than 25 minutes, then such a composition belongs to the slow-extinguishing type.

Special varieties of calcium quicklime include chlorine and soda mixture. The chlorine composition is obtained by adding chlorine to slaked lime. Soda lime is a reaction product of soda ash and calcium hydroxide.

Scope of application

Quicklime can be used in various fields of human activity. It is most widely used in construction and everyday life. The material is used as an additional component for the preparation of cement mortars. Its astringent properties give the necessary plasticity to the mixture, and also reduce the hardening time. Lime is used as an additional component in the production of silicate bricks.

Lime-based solutions are used for whitewashing various indoor surfaces. This method of processing ceiling and wall surfaces is still relevant to this day, since lime is one of the materials that is very affordable, and the decorative effect it creates is no worse than from expensive paints and varnishes.

In agriculture and horticulture, lime is also an important component. It is used to reduce acidity and enrich the soil with calcium. The quicklime composition applied to the soil contributes to the retention of nitrogen in the soil, while activating the work of beneficial microorganisms and stimulating the growth of the root system of plants.

Quicklime also has a negative impact on crop pests. To carry out preventive measures aimed at controlling insects, lime is used as a solution with which plants are sprayed or treated lower part tree trunks. For animals, lime is a source of calcium, so it is often given as a top dressing.

In everyday life and medical institutions, bleach is used as an excellent disinfectant. The solution from it kills most of the known pathogenic microorganisms, inhibiting the growth and their further development. Quicklime also helps in the neutralization of household gases and sewage.

In the food industry, lime is known as the E-529 emulsifier. Its presence makes it possible to improve the mixing process for components whose structure does not allow them to connect correctly.

How to breed?

Quicklime is packaged by manufacturers in bags. As a rule, a bag of 2-5 kg ​​is enough for processing plants and whitewashing fruit trees. In order to dilute lime correctly, it is necessary to prepare a container and follow the procedure.

Before diluting lime, it is necessary to choose a container that is suitable in size and material. The volume of the container is selected based on the expected volume, and the material of the utensils can be any, even metal utensils can be used, as long as it is free of chips and rust.

Its application.

Slaked lime (formula – Ca(OH)2) is a strong base. May be found frequently in some sources under the name calcium hydroxide or "fluff".

Properties: It is presented as a white powder, which is slightly soluble in water. The lower the temperature of the medium, the lower the solubility. The products of its reaction with acid are the corresponding calcium salts. For example, when slaked lime is immersed in sulfuric acid, calcium sulfate and water are obtained. If you leave a solution of "fluff" in the air, it will interact with one of the components of the latter - carbon dioxide. During this process, the solution becomes cloudy. The products of this reaction are calcium carbonate and water. If we continue bubbling carbon dioxide, the reaction will end with the formation of calcium bicarbonate, which is destroyed when the temperature of the solution rises. slaked lime and carbon monoxide will interact at t about 400°C, the already known carbonate and hydrogen will become its products. The substance can also react with salts, but only if the process ends with precipitation, for example, if you mix "fluff" with sodium sulfite, then sodium hydroxide and calcium sulfite will become the reaction products.

What is lime made of? The very name "slaked" already indicates that something was quenched to obtain this substance. As everyone knows, any chemical compound (and indeed anything) is usually quenched with water. And she has something to respond to. In chemistry, there is a substance called "quicklime". So, by adding water to it, the desired compound is obtained.

Application: Slaked lime is used for whitewashing any room. Also, with its help, water is softened: if you add "fluff" to calcium bicarbonate, then hydrogen oxide and an insoluble precipitate are formed - carbonate of the corresponding metal. Hydrated lime is used in tanning leather, caustification of sodium and potassium carbonates, obtaining calcium compounds, various organic acids and many other substances.

With the help of a solution of "fluff" - the notorious lime water - you can detect the presence of carbon dioxide: when it reacts with it, it becomes cloudy (photo). Dentistry cannot do without the calcium hydroxide discussed now, because thanks to it, in this branch of medicine, it is possible to disinfect the root canals of the teeth. Also, with the help of slaked lime, a lime mortar is made by mixing it with sand. A similar mixture was used in ancient times, then not a single building masonry could do without it. However, due to the unnecessary release of water during the reaction of "fluff" with sand, this solution is now successfully replaced with cement. Calcium hydroxide is used to produce lime fertilizers, it is also a food additive E526 ... And many more industries cannot do without its use.

Quicklime– Quicklime (crude calcium oxide) is obtained by calcining limestone containing very little or no clay. It very quickly combines with water, releasing a significant amount of heat and forming slaked lime (calcium hydroxide).

Quicklime has many useful properties, due to this, it is widely used in construction, industry and agriculture.

Properties: finely porous pieces of CaO with a size of 5...10 cm, obtained after firing raw materials, the average density is 1600...1700 kg/m3.
Depending on the content of magnesium oxide, air lime is divided into calcium (70 ... 90% CaO and up to 5% MO), magnesian (up to 20% Mg0) and high magnesian or dolomite (Mg0 from 20 to 40%).
Air quicklime is produced in three grades. Depending on the time of slaking lime of all grades, there are: quick-extinguishing lime (slaking time up to 8 minutes); medium-extinguishing (up to 25 min), slow-extinguishing (over 25 min).

Building air lime is divided into three grades.
The density of quicklime varies between 3.1-3.3 g / cm3 and depends mainly on the firing temperature, the presence of impurities, underburning and overburning.
The density of hydrated lime depends on the degree of its crystallization and is equal to 2.23 for Ca (OH) 2 crystallized in the form of hexagonal plates, and 2.08 g / cm3 for amorphous.
Bulk weight of lump quicklime in
piece to a large extent depends on the firing temperature and increases from 1.6 g/cm3 (lime fired at a temperature of 800°C) to 2.9 g/cm3 (long-term firing at a temperature of 1300°C).
The bulk density for other types of lime is as follows: for ground quicklime in loose-filled state 900-1100, in compacted 1100-1300 kg/m3; for hydrated lime (fluff) in a loose-filled state - 400-500, in a compacted 600-700 kg / m3; for lime test-1300-1400 kg/m3.
Plasticity, which determines the ability of the binder to give mortars and concretes workability, is the most important property of lime. The plasticity of lime is associated with its high water-holding capacity. Finely dispersed particles of calcium oxide hydrate, adsorptively retaining a significant amount of water on their surface, create a kind of lubricant for aggregate grains in a mortar or concrete mixture, reducing friction between them. As a result, lime mortars have high workability, are easily and evenly distributed in a thin layer on the surface of brick or concrete, adhere well to them, and are water-retaining even when applied to brick and other porous substrates.

Application: This substance is widely used in various fields of human activity. The largest consumers include: ferrous metallurgy, agriculture, sugar, chemical, pulp and paper industries. CaO is also used in the construction industry. The connection is of particular importance in the field of ecology. Lime is used to remove sulfur oxide from flue gases. The compound is also able to soften water and precipitate organic products and substances present in it. In addition, the use of quicklime ensures the neutralization of natural acidic and waste water. In agriculture, when in contact with soils, the compound eliminates acidity that is harmful to cultivated plants. Quicklime enriches the soil with calcium. Due to this, the workability of the land increases, and the decay of humus accelerates. At the same time, the need to apply nitrogen fertilizers in large doses is reduced.

The hydrated mixture is used in poultry and livestock for feeding. This eliminates the lack of calcium in the diet. In addition, the compound is used to improve general sanitary conditions in the maintenance and breeding of livestock. In the chemical industry, hydrated lime and sorbents are used to produce calcium fluoride and calcium hydrochloride. In the petrochemical industry, the compound neutralizes acid tars, and also acts as a reagent in the main inorganic and organic synthesis. Lime is widely used in construction. This is due to the high environmental friendliness of the material. The mixture is used in the preparation of binders, concretes and mortars, the production of products for construction.

Corrosion of metals and methods of protection against corrosion

Corrosion of metals- the process of destruction of metals and alloys due to chemical or electrochemical interaction with external environment, as a result of which metals oxidize and lose their inherent properties. Corrosion is the enemy of metal products. Every year in the world, as a result of corrosion, 10 ... 15% of the smelted metal is lost, or 1 ... 1.5% of the total metal accumulated and exploited by man.

Chemical corrosion- destruction of metals and alloys as a result of oxidation when interacting with dry gases at high temperatures or with organic liquids - petroleum products, alcohol, etc.

Electrochemical corrosion- destruction of metals and alloys in water and aqueous solutions. For the development of corrosion, it is enough that the metal is simply covered with the thinnest layer of adsorbed water (wet surface). Due to the heterogeneity of the metal structure during electrochemical corrosion, galvanic pairs (cathode - anode) are formed in it, for example, between metal grains (crystals) that differ from one another chemical composition. Metal atoms from the anode pass into solution in the form of cations. These cations combine with the anions contained in the solution to form a rust layer on the metal surface. Basically, metals are destroyed by electrochemical corrosion.

Corrosion of metals causes great economic damage, as a result of corrosion, equipment, machines, mechanisms fail, metal structures are destroyed. Particularly susceptible to corrosion of equipment in contact with an aggressive environment, such as solutions of acids, salts.

Under normal conditions, metals can enter into chemical reactions with substances contained in the environment - oxygen and water. Spots appear on the surface of metals, the metal becomes brittle and cannot withstand loads. This leads to the destruction of metal products, for the manufacture of which a large amount of raw materials, energy and human effort were spent.
Corrosion is the spontaneous destruction of metals and alloys under the influence of the environment.
A striking example of corrosion is rust on the surface of steel and cast iron products. Every year, about a quarter of all iron produced in the world is lost due to corrosion. Costs for the repair or replacement of ships, vehicles, instruments and communications, water pipes many times higher than the cost of the metal from which they are made. Corrosion products pollute the environment and adversely affect the life and health of people.
Chemical corrosion occurs in various chemical industries. In an atmosphere of active gases (hydrogen, hydrogen sulfide, chlorine), in an environment of acids, alkalis, salts, as well as in molten salts and other substances, specific reactions occur with the involvement of metallic materials from which the devices are made in which the chemical process is carried out. Gas corrosion occurs at elevated temperatures. Furnace fittings, parts of internal combustion engines fall under its influence. Electrochemical corrosion occurs if the metal is contained in any aqueous solution.
The most active environmental components that act on metals are oxygen O2, water vapor H2O, carbon (IV) oxide CO2, sulfur (IV) oxide SO2, nitrogen (IV) oxide NO2. The corrosion process is greatly accelerated when metals come into contact with salt water. For this reason, ships rust faster in sea water than in fresh water.
The essence of corrosion is the oxidation of metals. Corrosion products can be oxides, hydroxides, salts, etc. For example, the corrosion of iron can be schematically described by the following equation:
4Fe + 6H2O + 3O2 → 4Fe(OH) 3.
It is impossible to stop corrosion, but it can be slowed down. There are many ways to protect metals from corrosion, but the main method is to prevent contact of iron with air. To do this, metal products are painted, varnished or coated with a layer of lubricant. In most cases, this is enough to keep the metal from deteriorating for several tens or even hundreds of years. Another way to protect metals from corrosion is the electrochemical coating of the surface of a metal or alloy with other metals that are resistant to corrosion (nickel plating, chromium plating, zinc plating, silver plating and gold plating). In engineering, special corrosion-resistant alloys are often used. To slow down the corrosion of metal products in an acidic environment, special substances are also used - inhibitors.

Life and work of A.M. Butlerov

Alexander Butlerov was born in 1828 in Butlerovka, a small village near Kazan, where his father's estate was located. Sasha did not remember his mother, she died 11 days after his birth. Raised by his father, an educated man, Sasha wanted to be like him in everything.

At first he went to a boarding school, and then entered the First Kazan Gymnasium, whose teachers were very experienced, well-trained, they knew how to interest students. Sasha easily assimilated the material, since from early childhood he was taught to work systematically. He was especially attracted to the natural sciences.

After graduating from the gymnasium, against the wishes of his father, Sasha entered the natural science department of Kazan University, however, so far only as a student, since he was still a minor. Only the following year, 1845, when the young man turned 17, his name appeared on the list of those accepted for the first year.

In 1846, Alexander fell ill with typhus and miraculously survived, but his father, who had contracted it, died. In autumn, together with my aunt, they moved to Kazan. Gradually, youth took its toll, both health and fun returned to Sasha. Young Butlerov studied with exceptional zeal, but, to his surprise, he noticed that lectures on chemistry give him the greatest pleasure. The lectures of Professor Klaus did not satisfy him, and he began to regularly attend the lectures of Nikolai Nikolaevich Zinin, which were given to students of the Physics and Mathematics Department. Very soon Zinin, watching Alexander during laboratory work, noticed that this fair-haired student was unusually gifted and could become a good researcher.

Butlerov was successful, but more and more often he thought about his future, not knowing what he would eventually choose. Take up biology? But, on the other hand, doesn't the lack of a clear understanding of organic reactions offer endless possibilities for research?

To receive a candidate's degree, Butlerov had to submit a dissertation upon graduation from the university. By this time, Zinin left Kazan for St. Petersburg and he had no choice but to take up the natural sciences. For the candidate's work, Butlerov prepared the article "Daytime butterflies of the Volga-Ural fauna". However, the circumstances were such that Alexander still had to return to chemistry.

After approval by the Council degree Butlerov stayed to work at the university. The only professor of chemistry, Klaus, could not conduct all the classes himself and needed an assistant. Butlerov became them. In the fall of 1850, Butlerov passed the exams for the degree of master of chemistry and immediately began his doctoral dissertation "On essential oils", which he defended at the beginning next year. In parallel with the preparation of the lecture, Butlerov engaged in a detailed study of the history of chemical science. The young scientist worked hard in his office, in the laboratory, and at home.

According to his aunts, their old apartment The ball was uncomfortable, so they rented another, more spacious one from Sofya Timofeevna Aksakova, an energetic and determined woman. She received Butlerov with maternal care, seeing him as a suitable match for her daughter. Despite being constantly busy at the university, Alexander Mikhailovich remained a cheerful and sociable person. He was by no means distinguished by the notorious "professorial absent-mindedness", and his friendly smile and ease of address made him a welcome guest everywhere. Sofya Timofeevna noted with satisfaction that the young scientist was clearly not indifferent to Nadenka. The girl was really good: a high intelligent forehead, large shiny eyes, strict regular features and some special charm. Young people became good friends, and over time they began to increasingly feel the need to be together, sharing their most intimate thoughts. Soon Nadezhda Mikhailovna Glumilina, the niece of the writer S.T. Aksakova became the wife of Alexander Mikhailovich.

Butlerov was known not only as an outstanding chemist, but also as a talented botanist. He conducted various experiments in his greenhouses in Kazan and Butlerovka, wrote articles on the problems of horticulture, floriculture and agriculture. With rare patience and love, he watched the development of delicate camellias, lush roses, brought out new varieties of flowers.

On June 4, 1854, Butlerov received confirmation that he had been awarded the degree of Doctor of Chemistry and Physics. Events unfolded with incredible speed. Immediately after receiving his doctorate, Butlerov was appointed acting professor of chemistry at Kazan University. At the beginning of 1857, he already became a professor, and in the summer of that year he received permission to travel abroad.

Butlerov arrived in Berlin at the end of the summer. He then continued to tour Germany, Switzerland, Italy and France. The ultimate goal of his journey was Paris - the world center of chemical science of that time. He was attracted, first of all, by a meeting with Adolf Würz. Butlerov worked in Wurtz's laboratory for two months. It was here that he began his experimental research, which over the next twenty years was crowned with the discovery of dozens of new substances and reactions. Numerous exemplary syntheses of Butler's ethanol and ethylene, tertiary alcohols, polymerization of ethylene hydrocarbons lie at the origins of a number of industries and, thus, had the most direct stimulating effect on it.

Studying hydrocarbons, Butlerov realized that they represent a very special class. chemical substances. Analyzing their structure and properties, the scientist noticed that there is a strict pattern here. It formed the basis of the theory he created. chemical structure.

His report at the Paris Academy of Sciences aroused general interest and lively debate. Butlerov said: “Perhaps the time has come when our research should become the basis of a new theory of the chemical structure of substances. This theory will differ in accuracy mathematical laws and will make it possible to predict the properties of organic compounds. No one has yet expressed such thoughts.

A few years later, during a second trip abroad, Butlerov presented the theory he had created for discussion. He made the announcement at the 36th Congress of German Naturalists and Physicians in Speyer. The convention took place in September 1861.

He made a presentation before the chemical section. The topic had a more than modest name: "Something about the chemical structure of bodies."

Butlerov spoke simply and clearly. Without going into unnecessary details, he introduced the audience to a new theory of the chemical structure of organic substances: his report aroused unprecedented interest.

The term "chemical structure" was also encountered before Butlerov, but he rethought it and applied it to define a new concept of the order of interatomic bonds in molecules. The theory of chemical structure now serves as the basis for all modern branches of synthetic chemistry without exception.

So, the theory has declared its right to exist. It required further development, and where, if not in Kazan, should this be done, because a new theory was born there, its creator worked there. For Butlerov, rector's duties turned out to be a heavy and unbearable burden. He several times asked to be relieved of this position, but all his requests remained unsatisfied. Worries did not leave him at home. Only in the garden, taking care of his favorite flowers, did he forget the anxieties and troubles of the past day. Often, his son Misha worked with him in the garden; Alexander Mikhailovich asked the boy about the events at school, and told curious details about the flowers.

The year 1863 came - the happiest year in the life of the great scientist. Butlerov was on the right way. For the first time in the history of chemistry, he managed to obtain the simplest tertiary alcohol - tertiary butyl alcohol, or trimethylcarbinol. Shortly thereafter, reports appeared in the literature about the successful synthesis of primary and secondary butyl alcohols.

Scientists have known isobutyl alcohol since 1852, when it was first isolated from natural vegetable oil. Now there was no question of any dispute, since there were four different butyl alcohols, and all of them are isomers.

In 1862 - 1865, Butlerov expressed the main position of the theory of reversible isomerization of tautomerism, the mechanism of which, according to Butlerov, consisted in the splitting of molecules of one structure and the combination of their residues to form molecules of another structure. It was a brilliant idea. The great scientist argued the need for a dynamic approach to chemical processes, that is, consider them as equilibrium.

Success brought confidence to the scientist, but at the same time presented him with a new, more difficult task. It was necessary to apply structural theory to all reactions and compounds organic chemistry, and most importantly, to write a new textbook on organic chemistry, where all phenomena would be considered from the point of view of a new theory of structure.

Butlerov worked on the textbook for almost two years without a break. The book "Introduction to the Complete Study of Organic Chemistry" was published in three editions in 1864-1866. She did not go in any comparison, with any of the then known textbooks. This inspired work was the revelation of Butlerov, a chemist, experimenter and philosopher, who rebuilt all the material accumulated by science according to a new principle, according to the principle of chemical structure.

The book caused a real revolution in chemical science. Already in 1867, work began on its translation and publication in German. Shortly thereafter, publications appeared in almost all major European languages. According to the German researcher Victor Meyer, she became the "guiding star" in the vast majority of research in organic chemistry.

Since Alexander Mikhailovich finished work on the textbook, he increasingly spent time in Butlerovka. Even during school year the family went to the village several times a week. Butlerov felt free from worries here and devoted himself entirely to his favorite hobbies: flowers and collections of insects.

Now Butlerov worked less in the laboratory, but closely followed new discoveries. In the spring of 1868, at the initiative of the famous chemist Mendeleev, Alexander Mikhailovich was invited to St. Petersburg University, where he began to lecture and got the opportunity to organize his own chemical laboratory. Butlerov developed a new methodology for teaching students by offering the now universally accepted laboratory workshop in which students were taught how to work with a variety of chemical equipment.

Simultaneously with his scientific activities, Butlerov is actively involved in public life Petersburg. At that time, the progressive public was particularly concerned about the education of women. Women should have free access to higher education! The Higher Women's Courses were organized at the Medico-Surgical Academy, classes began at the Bestuzhev Women's Courses, where Butlerov lectured on chemistry.

The multilateral scientific activity of Butlerov was recognized by the Academy of Sciences. In 1871 he was elected an extraordinary academician, and three years later - an ordinary academician, which gave him the right to receive an apartment in the Academy building. Nikolai Nikolaevich Zinin also lived there. Close proximity further strengthened a long-standing friendship.

The years passed inexorably. Working with students became too difficult for him, and Butlerov decided to leave the university. He delivered his farewell lecture on April 4, 1880, to the second-year students. They greeted the news of the departure of their beloved professor with deep chagrin. The Academic Council decided to ask Butlerov to stay and elected him for another five years.

The scientist decided to limit his activities at the university only to reading the main course. And yet, several times a week, he appeared in the laboratory and supervised the work.

Throughout his life, Butlerov carried another passion - beekeeping. On his estate, he organized an exemplary apiary, and in the last years of his life, a real school for peasant beekeepers. Butlerov was proud of his book "The Bee, Its Life and the Rules of Intelligent Beekeeping" almost more than his scientific work.

Butlerov believed that a real scientist should also be a popularizer of his science. Parallel to scientific articles he published public pamphlets in which he vividly and colorfully spoke about his discoveries. He completed the last of them six months before his death.

This is a material with the properties of a binder, which is obtained as a result of firing followed by processing of carbonate rocks. Among them: calcareous-magnesian minerals, limestone, chalk. Lime, in its various manifestations, is used in almost all areas of human activity, including the construction industry.

In its pure form, it is a colorless substance that is rather poorly soluble in water. Consists of two main components: CaO and MgO. The following types of lime are known:

• Hydrated has the formula Ca(OH)2. In turn, it is subdivided into hydrated or fluff and lime dough.
• Quicklime - CaO. Depending on the method of processing after firing, lump or ground lime is produced.
• The formula for bleach is Ca(Cl)OCl. This variety is an excellent disinfectant.
• Soda consists of slaked lime and caustic soda (sodium hydroxide) NaOH. It has a specific meaning and is mainly used where neutralization of carbon dioxide is necessary.

In the construction industry and the production of building materials, all modifications of slaked and quicklime are used.

How to slake lime

Slaked lime is available in hardware stores, but you can also prepare it yourself. First you need to figure out what it is slaked lime. This material is obtained by treating lump quicklime with water.

Important! Lime is caustic, do not allow it to come into contact with the skin, in the eyes. Therefore, work with it should be using personal protective equipment: gloves, goggles, a respirator, durable overalls.

For work, it is necessary to prepare a container of sufficient volume, without corrosion. In production, special pits are used. You will need lump quicklime and a mixing device. You can use a convenient wooden stick, even a shovel handle will do. Further:

• The required amount of starting material is placed in the prepared container.
• Pour it with COLD water in a ratio of 1: 1. During the initial interaction with water, lime behaves very violently and becomes very hot. At this point, it is especially necessary to remember the safety rules.
• Quicklime from different manufacturers, made from different raw materials, may differ in properties. Therefore, it is better to fill it with water in several steps to ensure uniform extinguishing.
• In the first half hour, the composition must be constantly mixed. Then the container must be closed and left alone for at least two weeks. Practice shows that the longer the exposure, the better the fluff is obtained.

Cooking fluff is best outdoors, as slaking lime at home, indoors is unhealthy and unsafe. Immediately before use, the consistency of slaked lime may require additional dilution.

The easiest way to determine the readiness of the mixture is by following the trail on the stick. If, when the fluff is mixed, a clear trace of white color remains on it, then the composition is ready. How to dilute lime to the desired density? Just add water and mix thoroughly. After the extinguishing process has passed, the material is no longer so dangerous.

After the preparation of slaked lime, during the first filling with water, unslaked pieces are sure to remain. They can be formed as a result of incomplete firing or, conversely, burnout. So don't throw them out right away. Gotta fill it up again. clean water and use as intended. And after the secondary processing - dispose of.

What is the difference between slaked lime and quicklime

Burnt limestone instantly enters into chemical reaction with water, therefore, as a binder in its pure form, it cannot be used. However, quicklime has found its use in the manufacture of cinder concrete, coloring compositions, silicate bricks, cellular and heavy silicate concrete. It is difficult to do without it in the process of wastewater and flue gas treatment. Quicklime serves as an excellent fertilizer to reduce soil acidity and increase its fertility.

The main difference between slaked lime and quicklime lies in their composition and properties. The quenching procedure converts calcium oxide to hydroxide, completely changing the characteristics of the starting material. As a result, you can get:

• dry calcium hydroxide (fluff);
• lime dough;
• lime milk;
• lime water.

Scope of slaked lime in construction industry and finishing work is wide enough. The preparation of masonry, plaster mortars, lime-based silicate concrete makes them especially plastic and workable. In addition, it is used as a whitewash material, as well as in the production of bleach, in the leather and food industries.

Conditions for the safe storage of slaked lime

Unlike quicklime, slaked building lime can be stored for a very long time without changing its composition and properties. But subject to certain rules.

• The material should be stored at positive outside temperatures.
• If slaked lime is stored in a street pit, then for the winter it must be covered with a layer of sand, 200 mm thick, and 700 mm of soil should be covered on top.
• You can use thermal insulation materials for shelter, if available.

Lime is a material a high degree moisture absorption, therefore, when frozen, it may lose its binding properties and the ability to adhere well to other materials. This is an important reason to ensure normal storage conditions.

First aid for lime burns

If, nevertheless, the precautions for extinguishing did not help and the lime got on the skin, then measures should be taken immediately. In case of burns with quicklime, it is necessary to free the victim from soiled clothes, remove the substance from the affected area with a dry cloth or rag. Wash the area thoroughly large quantity running water. Then treat with 2% solution boric acid and apply a bandage of sterile material with synthomycin ointment or Vishnevsky balm. And immediately seek help from a medical institution.

Lime hydrate (fluff, slaked lime), the formula of which is Ca (OH) 2, does not require special conditions storage. The material may be kept outdoors. Only a canopy is needed to protect it from rain.

To completely extinguish fifty-six kilograms of lime into powder, about forty liters of water should be used, which is about sixty-nine percent of the volume of lime taken. In the event that less liquid is taken, the process will be incomplete.

If the slaked lime is produced in a confined space and cannot be removed, the process will be complete with less liquid. However, the amount of water should be close to the theoretically required one.

In contact with H2O, the "boiler" (what lime is made of) begins to absorb it. In the process, the raw material cracks, crumbling gradually into the smallest powder. In this case, the formation of heat in large quantities is noted.

The purer the lime, the more completely and faster it crumbles during the slaking process. The result is a fluff powder that is softer and more voluminous. Hydrated lime has a volume three to three and a half times greater than the feedstock. This increase occurs with a fairly large force. This factor is used, for example, when splitting stones. However, it should be said that such a strong increase becomes possible due to the loosening of the substance, that is, the total pore volume becomes larger.

Slaked lime is produced, as a rule, in the factory. The most common method is when a pile formed from pieces of a "boiler" on a plank platform or a rammed platform is poured with water, sprinkled with a layer of sand. Sand is needed to retain water vapor.

Another, less economically advantageous and therefore less commonly used method of obtaining is the method of immersion in water. At the same time, pieces of "boiling water" are put into baskets (iron or woven from willow twigs) and lowered into H2O. Keep the raw material until the water starts to turn white. It should be noted that this method is very labor intensive.

The most perfect is the method of converting the feedstock into powder by exposing it to hot steam. For extinguishing by this method, an iron boiler is used, which is strong enough and with a tightly closed neck. The container is equipped with a pressure gauge and the required amount of raw materials is poured into the boiler, taking into account the increase in volume as a result. Then water is poured in the required amount and, hermetically closing the container, they begin to rotate it. So, the process of scattering is accelerated. Under the influence of high pressure, the temperature in the boiler rises to one hundred degrees. Extinguishing as a result is carried out completely and quickly.

Slaked lime is poorly soluble in water. When mixing sand and lime paste, a solution is obtained, which is widely used in finishing, in particular,

Lime for the soil is an important component of high fertility. About 10 million hectares of arable land in Ukraine have hyperacidity, while for the growth, development and maturation of most crops, slightly acidic or neutral environment. An effective way to increase the productivity of soils with high acidity is liming.

General information and main characteristics

Lime is a binder that is obtained as a result of roasting and further processing of chalk, limestone and other lime-magnesian rocks. The term in Greek means "inextinguishable".

The material consists of a mixture of calcium oxide CaO and magnesium oxide MgO. Lime is used in ferrous metallurgy, construction, pulp and paper industry, chemical industry and agriculture.

It is recognized as an environmentally friendly, safe material, well tolerated by allergy sufferers. But when the substance is extinguished, there is a possibility of getting burns, harmful effects emitted vapors on the mucous membranes of the respiratory system and eyes. When working with the material, it is important to observe safety precautions.

Varieties

There are types of lime:

• quicklime (formula CaO);
• slaked lime (formula Ca (OH) 2);
• soda lime (obtained by mixing slaked lime Ca (OH) 2 and NaOH);
• bleach (formula Ca(Cl)OCl).

Quicklime (“kipelka”) is distinguished by its snow-white color. The substance seethes when it reacts with water, liberating a large amount of heat. It is more often used in the construction industry, metallurgy, sugar production. In the food industry, it is known as food additive E529.

Quicklime has found its application in "self-heating" dishes. A container with a small amount of calcium oxide is placed between the two walls of the glass, after piercing the water tank, a reaction occurs during which heat is released.

Slaked lime (hydrated, “fluff”) is a white powder that is poorly soluble in water. The scope of application is extensive: the construction industry, the production of lime fertilizers, the neutralization of soils with high acidity, water softening, the dental industry, horticulture, the textile industry and others. In the food industry, it is known as a food additive E526.

Soda lime has the appearance of a white porous mass, serves to absorb carbon dioxide and water (excess moisture from the air). It is used in diving equipment, gas masks, in artificial lung ventilation devices, in laboratory equipment.

A bleach solution is more commonly known as bleach. Scope of application: disinfection and bleaching.

Features of the use of lime

For the temperate zone, there is a need for liming acidic soils due to their physical and chemical composition. Without lime, erosion develops, soil depletion occurs and crop yields decrease.

Signs of acidification:

• whitish shade of soil;
• poor growth of alfalfa, clover, winter wheat;
• pronounced podzolic horizon (about 10 cm);
• development of weeds - pikulnik, sorrel, creeping buttercup, white-bearded.

The effect of the use is to neutralize the excess level of soil acidity. Calcium content - pledge effective growth plants. It activates fertility by increasing the availability of nutrients for cultivated crops. Interacting with iron and aluminum, lime serves as a catalyst for the decomposition of organic matter, the release of nitrogen and the activity of microorganisms in the root area.

Application in agriculture helps to provide plants with microelements, improve soil structure. Any time of the year is suitable for application, it is better before winter. The optimal frequency of application is annually.

Crops are sensitive to the level of acidity: fodder and sugar beet, alfalfa, peas, cabbage, wheat, barley, sunflower, legumes and others. Yields on acidic soils can decrease by 15-20%.

Application rates:

• for sandy soil type or light loam - 250-400 g / sq.m.;
• for medium or heavy loam - 350-600 g / sq.m.

When lime is introduced into the soil, the yield of winter wheat increases up to 5.5 centners / ha, potatoes up to 20 centners / ha, perennial grasses up to 10 centners / ha, sugar beet up to 50 centners / ha. The use of lime fertilizers increases the content of vitamins in hay, grain, silage, starch in potatoes, sugar in root crops. Feeding animals with the received feed reduces the incidence rate of young animals, increases growth.

Lime differs from other fertilizers in its low price. The effect of its application persists for 5-20 years and depends on the composition of the soil and the applied dose.

Release form and price of lime in Ukraine

Hydrated lime is produced in the form of powder, lime paste, lime milk:

• Hydrated lime (fluff) - fine powder of light color.
• Lime dough is a pasty plastic mass, consisting of hydrated lime and water.
• Lime milk - water suspension of milky color.

Estimated price in Ukraine is 900-2600 UAH / t, depending on the packaging and volume.

Transport and storage

Hydrated lime for agriculture is transported by road and rail transport. The fertilizer is packaged in paper bags, and in bulk, special containers are used. It is advisable to use a covered body or wagon. When transported in the open air, lime is subject to additional protection from the effects of precipitation.

According to the hazard class, the material is classified as a group of low-hazard substances. Storage is organized in rooms with ventilation and protection from moisture.

Manufacturers

Ukrspecizvest LLC, PJSC Dniprozot, PrJSC Industry, etc.

DEFINITION

Slaked lime(calcium hydroxide) under normal conditions is a powder white color, which decompose without melting when heated (Fig. 1).

Poorly soluble in water (forming a dilute alkaline solution). Shows basic properties, reacts with acids. Absorbs carbon dioxide from the air.

Rice. 1. Slaked lime. Appearance.

A solution of slaked lime in water is called lime water.

Chemical formula of slaked lime

The chemical formula of slaked lime is Ca(OH) 2 . It shows that this molecule contains one calcium atom (Ar = 40 a.m.u.), two hydrogen atoms (Ar = 1 a.m.u.) and two oxygen atoms (Ar = 16 a.u. m.). According to the chemical formula, you can calculate the molecular weight of slaked lime:

Mr(Ca(OH) 2) = Ar(Ca) + 2×Ar(H) + 2×Ar(O);

Mr(Ca(OH) 2) = 40 + 2x1 + 2x16 = 40 + 2 + 32 = 74

Graphic (structural) formula of slaked lime

Structural (graphic) formula of slaked lime is more visual. It shows how the atoms are interconnected within the molecule (Fig. 2).

Rice. 2. Graphic formula of slaked lime.

Ionic formula

Hydrated lime is a diacid base that is capable of dissociating into ions in aqueous solution according to the following equation:

Ca (OH) 2 ↔ Ca 2+ + 2OH -

Examples of problem solving

Exercise	Determine molecular formula compound containing 49.4% potassium, 20.2% sulfur, 30.4% oxygen, if relative molecular mass of this compound is 3.95 times the relative atomic mass of calcium.
Decision	The mass fraction of the element X in the molecule of the HX composition is calculated by the following formula: ω (X) = n × Ar (X) / M (HX) × 100% Let us denote the number of moles of elements that make up the compound as "x" (potassium), "y" (sulfur) and "z" (oxygen). Then, the molar ratio will look like this (the values ​​​​of relative atomic masses taken from the Periodic Table of D.I. Mendeleev will be rounded to whole numbers): x:y:z = ω(K)/Ar(K) : ω(S)/Ar(S) : ω(O)/Ar(O); x:y:z= 49.4/39: 20.2/32: 30.4/16; x:y:z= 1.3: 0.63:1.9 = 2: 1: 3 Means the simplest formula compounds of potassium, sulfur and oxygen will have the form K 2 SO 3 and a molar mass of 158 g / mol. Find the true molar mass of this compound: M substance = Ar(Ca) × 3.95 = 40 × 3.95 = 158 g/mol M substance / M(K 2 SO 3) = 158 / 158 = 1 So the formula for the compound of potassium, sulfur and oxygen has the form K 2 SO 3.
Answer	K2SO3

Exercise	Determine the molecular formula of calcium nitrate, in which the mass ratios of calcium, nitrogen and oxygen are 10:7:24. The relative molecular weight of calcium nitrate is 164.
Decision	In order to find out in what relationship the chemical elements are in the composition of a molecule, it is necessary to find their amount of substance. It is known that to find the amount of a substance, the formula should be used: Let's find the molar masses of calcium, nitrogen and oxygen (the values ​​of the relative atomic masses taken from the Periodic Table of D.I. Mendeleev will be rounded up to whole numbers). It is known that M = Mr, which means M(Ca)= 40 g/mol, Ar(N)=14 g/mol, and M(O)=32 g/mol. Then, the amount of substance of these elements is equal to: n (Ca) = m (Ca) / M (Ca); n (Ca) = 10 / 40 = 0.25 mol n(N) = m(N) / M(N); n(N) = 7 / 14 = 0.5 mol n(O) = m(O) / M(O); n(O) = 24/16 = 1.5 mol Find the molar ratio: n(Ca) :n(N):n(O) = 0.25: 0.5: 1.5= 1: 2: 6, those. the simplest formula for the compound of calcium, nitrogen and oxygen has the form CaN 2 O 6 and a molar mass of 164 g / mol To find the true formula of an organic compound, we find the ratio of the obtained molar masses: M substance / M(CaN 2 O 6) = 164 / 164 = 1 This means that the formula for the compound of calcium, nitrogen and oxygen has the form CaN 2 O 6 or Ca (NO 3) 2. It's calcium nitrate.
Answer	Ca(NO 3) 2