What is carbon dioxide used for? Carbon dioxide (carbon dioxide)
Structural formula
True, empirical, or gross formula: CO2
Chemical composition of carbon dioxide
Molecular weight: 44.009
Carbon dioxide (carbon dioxide, carbon dioxide, carbon monoxide (IV), carbonic anhydride) is a colorless gas (under normal conditions), odorless, with a chemical formula CO2. Density under normal conditions 1.98 kg/m³ (heavier than air). At atmospheric pressure, carbon dioxide does not exist in a liquid state, passing directly from a solid to a gaseous state. Solid carbon dioxide is called dry ice. At elevated pressure and normal temperatures, carbon dioxide turns into a liquid, which is used for its storage. The concentration of carbon dioxide in the Earth's atmosphere is on average 0.04%. Carbon dioxide easily transmits ultraviolet rays and rays of the visible part of the spectrum, which come to Earth from the Sun and heat it. At the same time, it absorbs infrared rays emitted by the Earth and is one of the greenhouse gases, as a result of which it takes part in the process of global warming. A constant increase in the level of this gas in the atmosphere has been observed since the beginning of the industrial era.
Carbon monoxide (IV) - carbon dioxide, an odorless and colorless gas, heavier than air, crystallizes with strong cooling in the form of a white snow-like mass - "dry ice". At atmospheric pressure, it does not melt, but evaporates, the sublimation temperature is −78 °C. Carbon dioxide is formed during rotting and burning organic matter. Contained in the air and mineral springs, released during the respiration of animals and plants. Let's dissolve in water (1 volume of carbon dioxide in one volume of water at 15 °C).
By chemical properties carbon dioxide is an acidic oxide. When dissolved in water, it forms carbonic acid. Reacts with alkalis to form carbonates and bicarbonates. It enters into reactions of electrophilic substitution (for example, with phenol) and nucleophilic addition (for example, with organomagnesium compounds). Carbon monoxide(IV) does not support combustion. Only some active metals burn in it. Interacts with oxides of active metals. When dissolved in water, it forms carbonic acid. Reacts with alkalis to form carbonates and bicarbonates.
The human body releases approximately 1 kg (2.3 lb) of carbon dioxide per day. This carbon dioxide is transported from the tissues, where it is formed as one of the end products of metabolism, through the venous system and is then excreted in the exhaled air through the lungs. Thus, the content of carbon dioxide in the blood is high in the venous system, and decreases in the capillary network of the lungs, and low in the arterial blood. The content of carbon dioxide in a blood sample is often expressed in terms of partial pressure, that is, the pressure that carbon dioxide contained in a blood sample in a given amount would have if only carbon dioxide occupied the entire volume of the blood sample. Carbon dioxide ( CO2) is transported in the blood in three different ways (the exact ratio of each of these three modes of transport depends on whether the blood is arterial or venous).
- Most of the carbon dioxide (from 70% to 80%) is converted by the enzyme carbonic anhydrase of erythrocytes into bicarbonate ions.
- About 5% - 10% of carbon dioxide is dissolved in blood plasma.
- About 5% - 10% of carbon dioxide is associated with hemoglobin in the form of carbamin compounds (carbohemoglobin).
Hemoglobin, the main oxygen-transporting protein in red blood cells, is capable of transporting both oxygen and carbon dioxide. However, carbon dioxide binds to hemoglobin at a different site than oxygen. It binds to the N-terminal ends of the globin chains and not to the heme. However, due to allosteric effects, which lead to a change in the configuration of the hemoglobin molecule upon binding, the binding of carbon dioxide reduces the ability of oxygen to bind to it, at a given partial pressure of oxygen, and vice versa - the binding of oxygen to hemoglobin reduces the ability of carbon dioxide to bind to it, at a given partial pressure of carbon dioxide. In addition, the ability of hemoglobin to preferentially bind to oxygen or carbon dioxide also depends on the pH of the medium. These features are very important for the successful capture and transport of oxygen from the lungs to the tissues and its successful release in the tissues, as well as for the successful capture and transport of carbon dioxide from the tissues to the lungs and its release there. Carbon dioxide is one of the most important mediators of blood flow autoregulation. It is a powerful vasodilator. Accordingly, if the level of carbon dioxide in the tissue or in the blood rises (for example, due to intensive metabolism - caused, say, by exercise, inflammation, tissue damage, or due to obstruction of blood flow, tissue ischemia), then the capillaries expand, which leads to an increase in blood flow and respectively, to an increase in the delivery of oxygen to the tissues and the transport of accumulated carbon dioxide from the tissues. In addition, carbon dioxide in certain concentrations (increased, but not yet reaching toxic values) has a positive inotropic and chronotropic effect on the myocardium and increases its sensitivity to adrenaline, which leads to an increase in the strength and frequency of heart contractions, the magnitude of cardiac output and, as a result, , stroke and minute blood volume. It also contributes to the correction of tissue hypoxia and hypercapnia ( advanced level carbon dioxide). Bicarbonate ions are very important for regulating blood pH and maintaining normal acid-base balance. The respiratory rate affects the amount of carbon dioxide in the blood. Weak or slow breathing causes respiratory acidosis, while rapid and excessively deep breathing leads to hyperventilation and the development of respiratory alkalosis. In addition, carbon dioxide is also important in the regulation of respiration. Although our bodies require oxygen for metabolism, low oxygen levels in the blood or tissues usually do not stimulate respiration (or rather, the stimulatory effect of oxygen deficiency on respiration is too weak and “turns on” late, at very low blood oxygen levels, in which a person often is already losing consciousness). Normally, respiration is stimulated by an increase in the level of carbon dioxide in the blood. The respiratory center is much more sensitive to an increase in carbon dioxide than to a lack of oxygen. As a consequence, breathing highly rarefied air (with a low partial pressure of oxygen) or a gas mixture containing no oxygen at all (for example, 100% nitrogen or 100% nitrous oxide) can quickly lead to loss of consciousness without causing a feeling of lack of air (because the level of carbon dioxide does not rise in the blood, because nothing prevents its exhalation). This is especially dangerous for pilots of military aircraft flying at high altitudes (if an enemy missile hits the cockpit and depressurizes the cockpit, the pilots can quickly lose consciousness). This feature of the breathing regulation system is also the reason why, in airplanes, flight attendants instruct passengers in the event of a depressurization of the aircraft cabin to first put on an oxygen mask themselves before trying to help someone else - by doing this, the helper risks quickly losing consciousness himself, and even without feeling until the last moment any discomfort and the need for oxygen. The human respiratory center tries to maintain a partial pressure of carbon dioxide in the arterial blood no higher than 40 mm Hg. With conscious hyperventilation, the content of carbon dioxide in arterial blood can decrease to 10-20 mm Hg, while the oxygen content in the blood will practically not change or increase slightly, and the need to take another breath will decrease as a result of a decrease in the stimulating effect of carbon dioxide on the activity of the respiratory center. This is the reason why after a period of conscious hyperventilation it is easier to hold the breath for a long time than without prior hyperventilation. Such conscious hyperventilation followed by breath-holding can result in loss of consciousness before the person feels the need to breathe. In a safe environment, such a loss of consciousness does not threaten anything special (having lost consciousness, a person will lose control over himself, stop holding his breath and take a breath, breathing, and with it the supply of oxygen to the brain will be restored, and then consciousness will be restored). However, in other situations, such as before diving, it can be dangerous (loss of consciousness and the need to take a breath will come at a depth, and in the absence of conscious control, water will enter the airways, which can lead to drowning). That is why hyperventilation before diving is dangerous and not recommended.
In industrial quantities, carbon dioxide is emitted from flue gases, or as a by-product of chemical processes, for example, during the decomposition of natural carbonates (limestone, dolomite) or in the production of alcohol (alcoholic fermentation). The mixture of gases obtained is washed with a solution of potassium carbonate, which absorb carbon dioxide, turning into hydrocarbonate. A solution of bicarbonate, when heated or under reduced pressure, decomposes, releasing carbon dioxide. In modern installations for the production of carbon dioxide, instead of bicarbonate, an aqueous solution of monoethanolamine is more often used, which, under certain conditions, is able to absorb CO2 contained in the flue gas, and when heated, give it away; thus separating the finished product from other substances. Carbon dioxide is also produced in air separation plants as a by-product of obtaining pure oxygen, nitrogen and argon. AT laboratory conditions small quantities are obtained by reacting carbonates and bicarbonates with acids, such as marble, chalk or soda, with hydrochloric acid, using, for example, a Kipp apparatus. Using the reaction of sulfuric acid with chalk or marble results in the formation of insoluble calcium sulfate, which interferes with the reaction and is removed by a significant excess of acid. Beverages can be prepared by reacting baking soda with citric acid or acidic lemon juice. It was in this form that the first carbonated drinks appeared. Pharmacists were engaged in their manufacture and sale.
AT Food Industry carbonic acid is used as a preservative and baking powder, it is indicated on the packaging with the code E290. Liquid carbon dioxide is widely used in fire extinguishing systems and fire extinguishers. Automatic carbon dioxide fire extinguishing systems are distinguished by starting systems, which are pneumatic, mechanical or electric. A device for supplying carbon dioxide to an aquarium may include a gas tank. The simplest and most common method for obtaining carbon dioxide is based on the design for the manufacture of an alcoholic mash drink. During fermentation, the carbon dioxide released may well provide nutrition for aquarium plants. Carbon dioxide is used to carbonate lemonade and sparkling water. Carbon dioxide is also used as a protective medium in wire welding, but at high temperatures it dissociates with the release of oxygen. The released oxygen oxidizes the metal. In this regard, it is necessary to introduce deoxidizers, such as manganese and silicon, into the welding wire. Another consequence of the influence of oxygen, also associated with oxidation, is a sharp decrease in surface tension, which leads, among other things, to more intense metal spatter than when welding in an inert atmosphere. Carbon dioxide in cartridges is used in pneumatic weapons (in gas-cylinder pneumatics) and as a source of energy for engines in aircraft modeling. Storing carbon dioxide in a steel cylinder in a liquefied state is more profitable than in the form of a gas. Carbon dioxide has a relatively low critical temperature+31°С. About 30 kg of liquefied carbon dioxide is poured into a standard 40-liter cylinder, and at room temperature there will be a liquid phase in the cylinder, and the pressure will be approximately 6 MPa (60 kgf / cm²). If the temperature is above +31°C, then carbon dioxide will go into a supercritical state with a pressure above 7.36 MPa. The standard operating pressure for a typical 40 liter cylinder is 15 MPa (150 kgf/cm²), but it must safely withstand 1.5 times the pressure, i.e. 22.5 MPa, so working with such cylinders can be considered quite safe. Solid carbon dioxide - "dry ice" - is used as a refrigerant in laboratory research, in retail trade, in equipment repair (for example: cooling one of the mating parts during tight fitting), etc. Carbon dioxide is used to liquefy carbon dioxide and produce dry ice. installation.
Measurement of the partial pressure of carbon dioxide is required in technological processes, in medical applications - the analysis of respiratory mixtures during artificial ventilation of the lungs and in closed life support systems. Concentration analysis CO2 in the atmosphere is used for environmental and scientific research, to study the greenhouse effect. Carbon dioxide is recorded using gas analyzers based on the principle of infrared spectroscopy and other gas measuring systems. A medical gas analyzer for recording the content of carbon dioxide in exhaled air is called a capnograph. For measuring low concentrations CO2(as well as CO) in process gases or in atmospheric air, a gas chromatographic method with a methanator and registration on a flame ionization detector can be used.
Annual fluctuations in the concentration of atmospheric carbon dioxide on the planet are determined mainly by the vegetation of the middle (40-70 °) latitudes of the Northern Hemisphere. Vegetation in the tropics practically does not depend on the season, the dry belt of deserts 20-30 ° (both hemispheres) makes a small contribution to the carbon dioxide cycle, and the land strips most covered with vegetation are located on Earth asymmetrically (in the Southern Hemisphere in the middle latitudes there is an ocean). Therefore, from March to September, due to photosynthesis, the content CO2 drops in the atmosphere, and rises from October to February. Both wood oxidation (heterotrophic respiration of plants, rotting, decomposition of humus, forest fires) and the burning of fossil fuels (coal, oil, gas), which increase noticeably in the winter season, contribute to winter growth. A large amount of carbon dioxide is dissolved in the ocean. Carbon dioxide makes up a significant portion of some planets' atmospheres. solar system: Venus, Mars.
Carbon dioxide is non-toxic, but according to the effect of its elevated concentrations in the air on air-breathing living organisms, it is classified as an asphyxiant gas (English) Russian. Slight increases in concentrations up to 2-4% in rooms lead to the development of drowsiness and weakness in people. Dangerous concentrations are considered levels of about 7-10%, at which suffocation develops, manifesting itself in headache, dizziness, hearing loss and loss of consciousness (symptoms similar to those of altitude sickness), depending on the concentration, over a period of several minutes up to one hour. When air with high concentrations of gas is inhaled, death occurs very quickly from suffocation. Although, in fact, even a concentration of 5-7% CO2 is not lethal, even at a concentration of 0.1% (such a carbon dioxide content is observed in the air of megacities), people begin to feel weak, drowsy. This shows that even at high oxygen levels high concentration CO2 has a strong effect on well-being. Inhalation of air with a high concentration of this gas does not lead to long-term health disorders, and after the victim is removed from the polluted atmosphere, full recovery of health quickly occurs.
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Carbon monoxide (IV) does not support combustion. Only some active metals burn in it:
2 M g + C O 2 → 2 M g O + C (\displaystyle (\mathsf (2Mg+CO_(2)\rightarrow 2MgO+C)))Interaction with active metal oxide:
C a O + C O 2 → C a C O 3 (\displaystyle (\mathsf (CaO+CO_(2)\rightarrow CaCO_(3))))When dissolved in water, it forms carbonic acid:
C O 2 + H 2 O ⇄ H 2 C O 3 (\displaystyle (\mathsf (CO_(2)+H_(2)O\rightleftarrows H_(2)CO_(3))))Reacts with alkalis to form carbonates and bicarbonates:
C a (O H) 2 + C O 2 → C a C O 3 ↓ + H 2 O (\displaystyle (\mathsf (Ca(OH)_(2)+CO_(2)\rightarrow CaCO_(3)\downarrow +H_( 2)O))) (qualitative reaction for carbon dioxide) K O H + C O 2 → K H C O 3 (\displaystyle (\mathsf (KOH+CO_(2)\rightarrow KHCO_(3))))Biological
The human body releases approximately 1 kg (2.3 lb) of carbon dioxide per day.
This carbon dioxide is transported from the tissues, where it is formed as one of the end products of metabolism, through the venous system and is then excreted in the exhaled air through the lungs. Thus, the content of carbon dioxide in the blood is high in the venous system, and decreases in the capillary network of the lungs, and low in the arterial blood. The content of carbon dioxide in a blood sample is often expressed in terms of partial pressure, that is, the pressure that carbon dioxide contained in a blood sample in a given amount would have if only carbon dioxide occupied the entire volume of the blood sample.
Carbon dioxide (CO 2 ) is transported in the blood in three different ways (the exact ratio of each of these three modes of transport depends on whether the blood is arterial or venous).
Hemoglobin, the main oxygen-transporting protein in red blood cells, is capable of transporting both oxygen and carbon dioxide. However, carbon dioxide binds to hemoglobin at a different site than oxygen. It binds to the N-terminal ends of the globin chains, not to the heme. However, due to allosteric effects, which lead to a change in the configuration of the hemoglobin molecule upon binding, the binding of carbon dioxide reduces the ability of oxygen to bind to it, at a given partial pressure of oxygen, and vice versa - the binding of oxygen to hemoglobin reduces the ability of carbon dioxide to bind to it, at a given partial pressure of carbon dioxide. In addition, the ability of hemoglobin to preferentially bind to oxygen or carbon dioxide also depends on the pH of the medium. These features are very important for the successful capture and transport of oxygen from the lungs to the tissues and its successful release in the tissues, as well as for the successful capture and transport of carbon dioxide from the tissues to the lungs and its release there.
Carbon dioxide is one of the most important mediators of blood flow autoregulation. It is a powerful vasodilator. Accordingly, if the level of carbon dioxide in the tissue or in the blood rises (for example, due to intensive metabolism - caused, say, by exercise, inflammation, tissue damage, or due to obstruction of blood flow, tissue ischemia), then the capillaries expand, which leads to an increase in blood flow and respectively, to an increase in the delivery of oxygen to the tissues and the transport of accumulated carbon dioxide from the tissues. In addition, carbon dioxide in certain concentrations (increased, but not yet reaching toxic values) has a positive inotropic and chronotropic effect on the myocardium and increases its sensitivity to adrenaline, which leads to an increase in the strength and frequency of heart contractions, the magnitude of cardiac output and, as a result, , stroke and minute blood volume. It also contributes to the correction of tissue hypoxia and hypercapnia (elevated levels of carbon dioxide).
Bicarbonate ions are very important for regulating blood pH and maintaining normal acid-base balance. The respiratory rate affects the amount of carbon dioxide in the blood. Weak or slow breathing causes respiratory acidosis, while rapid and excessively deep breathing leads to hyperventilation and the development of respiratory alkalosis.
In addition, carbon dioxide is also important in the regulation of respiration. Although our bodies require oxygen for metabolism, low oxygen levels in the blood or tissues usually do not stimulate respiration (or rather, the stimulatory effect of oxygen deficiency on respiration is too weak and “turns on” late, at very low blood oxygen levels, in which a person often is already losing consciousness). Normally, respiration is stimulated by an increase in the level of carbon dioxide in the blood. The respiratory center is much more sensitive to an increase in carbon dioxide than to a lack of oxygen. As a consequence, breathing highly rarefied air (with a low partial pressure of oxygen) or a gas mixture containing no oxygen at all (for example, 100% nitrogen or 100% nitrous oxide) can quickly lead to loss of consciousness without causing a feeling of lack of air (because the level of carbon dioxide does not rise in the blood, because nothing prevents its exhalation). This is especially dangerous for pilots of military aircraft flying at high altitudes (in the event of an emergency depressurization of the cockpit, pilots can quickly lose consciousness). This feature of the breathing regulation system is also the reason why, in airplanes, flight attendants instruct passengers in the event of a depressurization of the aircraft cabin to first put on an oxygen mask themselves before trying to help someone else - by doing this, the helper risks quickly losing consciousness himself, and even without feeling any discomfort and need for oxygen until the last moment.
The human respiratory center tries to maintain a partial pressure of carbon dioxide in the arterial blood no higher than 40 mmHg. With conscious hyperventilation, the content of carbon dioxide in arterial blood can decrease to 10-20 mm Hg, while the oxygen content in the blood will practically not change or increase slightly, and the need to take another breath will decrease as a result of a decrease in the stimulating effect of carbon dioxide on the activity of the respiratory center. This is the reason why after a period of conscious hyperventilation it is easier to hold the breath for a long time than without prior hyperventilation. Such conscious hyperventilation followed by breath-holding can result in loss of consciousness before the person feels the need to breathe. In a safe environment, such a loss of consciousness does not threaten anything special (having lost consciousness, a person will lose control over himself, stop holding his breath and take a breath, breathing, and with it the supply of oxygen to the brain will be restored, and then consciousness will be restored). However, in other situations, such as before diving, it can be dangerous (loss of consciousness and the need to take a breath will come at a depth, and in the absence of conscious control, water will enter the airways, which can lead to drowning). That is why hyperventilation before diving is dangerous and not recommended.
Receipt
In industrial quantities, carbon dioxide is emitted from flue gases, or as a by-product of chemical processes, for example, during the decomposition of natural carbonates (limestone, dolomite) or in the production of alcohol (alcoholic fermentation). The mixture of gases obtained is washed with a solution of potassium carbonate, which absorb carbon dioxide, turning into hydrocarbonate. A solution of bicarbonate, when heated or under reduced pressure, decomposes, releasing carbon dioxide. In modern installations for the production of carbon dioxide, instead of bicarbonate, an aqueous solution of monoethanolamine is more often used, which, under certain conditions, is able to absorb CO₂ contained in the flue gas, and give it away when heated; thus separating the finished product from other substances.
Carbon dioxide is also produced in air separation plants as a by-product of obtaining pure oxygen, nitrogen and argon.
Under laboratory conditions, small amounts are obtained by reacting carbonates and bicarbonates with acids, such as marble, chalk or soda with hydrochloric acid, using, for example, a Kipp apparatus. Using the reaction of sulfuric acid with chalk or marble results in the formation of slightly soluble calcium sulfate, which interferes with the reaction and is removed by a significant excess of acid.
For the preparation of drinks, the reaction of baking soda with citric acid or with sour lemon juice can be used. It was in this form that the first carbonated drinks appeared. Pharmacists were engaged in their manufacture and sale.
Application
In the food industry, carbon dioxide is used as a preservative and baking powder, indicated on the packaging with the code E290.
Liquid carbon dioxide is widely used in fire extinguishing systems and fire extinguishers. Automatic carbon dioxide fire extinguishing installations differ in their starting systems, which are pneumatic, mechanical, or electric.
A device for supplying carbon dioxide to an aquarium may include a gas tank. The simplest and most common method for producing carbon dioxide is based on the design for making the alcoholic drink mash. During fermentation, the carbon dioxide released may well provide top dressing for aquarium plants.
Carbon dioxide is used to carbonate lemonade and sparkling water. Carbon dioxide is also used as a protective medium in wire welding, but at high temperatures it decomposes with the release of oxygen. The released oxygen oxidizes the metal. In this regard, it is necessary to introduce deoxidizers into the welding wire, such as manganese and silicon. Another consequence of the influence of oxygen, also associated with oxidation, is a sharp decrease in surface tension, which leads, among other things, to more intense metal spatter than when welding in an inert atmosphere.
Storing carbon dioxide in a steel cylinder in a liquefied state is more profitable than in the form of a gas. Carbon dioxide has a relatively low critical temperature of +31°C. About 30 kg of liquefied carbon dioxide is poured into a standard 40-liter cylinder, and at room temperature there will be a liquid phase in the cylinder, and the pressure will be approximately 6 MPa (60 kgf / cm²). If the temperature is above +31°C, then carbon dioxide will go into a supercritical state with a pressure above 7.36 MPa. The standard operating pressure for a typical 40 liter cylinder is 15 MPa (150 kgf/cm²), but it must safely withstand 1.5 times the pressure, i.e. 22.5 MPa, so working with such cylinders can be considered quite safe.
Solid carbon dioxide - "dry ice" - is used as a refrigerant in laboratory research, in retail trade, in equipment repair (for example: cooling one of the mating parts during tight fitting), etc. Carbon dioxide is used to liquefy carbon dioxide and produce dry ice. installation .
Registration Methods
Measurement of the partial pressure of carbon dioxide is required in technological processes, in medical applications - the analysis of respiratory mixtures during artificial ventilation of the lungs and in closed life support systems. The analysis of the concentration of CO 2 in the atmosphere is used for environmental and scientific research, to study the greenhouse effect. Carbon dioxide is recorded using gas analyzers based on the principle of infrared spectroscopy and other gas measuring systems. A medical gas analyzer for recording the content of carbon dioxide in exhaled air is called a capnograph. To measure low concentrations of CO 2 (as well as ) in process gases or in atmospheric air, a gas chromatographic method with a methanator and registration on a flame ionization detector can be used.
carbon dioxide in nature
Annual fluctuations in the concentration of atmospheric carbon dioxide on the planet are determined mainly by the vegetation of the middle (40-70 °) latitudes of the Northern Hemisphere.
A large amount of carbon dioxide is dissolved in the ocean.
Carbon dioxide makes up a significant part of the atmospheres of some planets in the solar system: Venus, Mars.
Toxicity
Carbon dioxide is non-toxic, but due to the effect of its elevated concentrations in the air on air-breathing living organisms, it is classified as an asphyxiant gas. (English) Russian. Slight increases in concentration up to 2-4% indoors lead to the development of drowsiness and weakness in people. Dangerous concentrations are considered levels of about 7-10%, at which suffocation develops, manifesting itself in headache, dizziness, hearing loss and loss of consciousness (symptoms similar to those of altitude sickness), depending on the concentration, over a period of several minutes up to one hour. When air with high concentrations of the gas is inhaled, death occurs very quickly by asphyxiation.
Although, in fact, even a concentration of 5-7% CO 2 is not lethal, already at a concentration of 0.1% (such a carbon dioxide content is observed in the air of megacities), people begin to feel weak, drowsy. This shows that even at high oxygen levels, a high concentration of CO 2 has a strong effect on well-being.
Inhalation of air with an increased concentration of this gas does not lead to long-term health problems, and after the victim is removed from the polluted atmosphere, full recovery of health quickly occurs.
(IV), carbon dioxide or carbon dioxide. It is also called carbonic anhydride. It is a colorless, odorless gas with a slightly sour taste. Carbon dioxide is heavier than air and does not dissolve well in water. At temperatures below -78 degrees Celsius, it crystallizes and becomes like snow.
From a gaseous state, this substance passes into a solid state, since it cannot exist in a liquid state under atmospheric pressure conditions. The density of carbon dioxide under normal conditions is 1.97 kg / m3 - 1.5 times higher. Carbon dioxide in solid form is called "dry ice". In a liquid state, in which it can be stored for a long time, it passes with increasing pressure. Let's take a closer look at this substance and its chemical structure.
Carbon dioxide, whose formula is CO2, consists of carbon and oxygen, and it is obtained as a result of the combustion or decay of organic matter. Carbon monoxide is found in the air and underground mineral springs. Humans and animals also release carbon dioxide when they exhale air. Plants without lighting release it, and during photosynthesis intensively absorb it. Thanks to the process of cell metabolism of all living beings, carbon monoxide is one of the main components of the environment.
This gas is not toxic, but if it accumulates in high concentration, suffocation (hypercapnia) may begin, and with its deficiency, the opposite state develops - hypocapnia. Carbon dioxide transmits and reflects infrared. It is which directly affects global warming. This is due to the fact that the level of its content in the atmosphere is constantly growing, which leads to the greenhouse effect.
Carbon dioxide is obtained industrially from smoke or furnace gases, or by the decomposition of dolomite and limestone carbonates. The mixture of these gases is thoroughly washed with a special solution consisting of potassium carbonate. Further, it passes into bicarbonate and decomposes when heated, as a result of which carbon dioxide is released. Carbon dioxide (H2CO3) is formed from carbon dioxide dissolved in water, but in modern conditions get it and other, more progressive methods. After the carbon dioxide is cleaned, it is compressed, cooled and pumped into cylinders.
In industry, this substance is widely and universally used. Food workers use it as a leavening agent (for example, for making dough) or as a preservative (E290). With the help of carbon dioxide, various tonic drinks and sodas are produced, which are so loved not only by children, but also by adults. Carbon dioxide is used in the manufacture of baking soda, beer, sugar, sparkling wines.
Carbon dioxide is also used in the production of effective fire extinguishers. With the help of carbon dioxide, an active environment is created, which is necessary at a high temperature of the welding arc, carbon dioxide decomposes into oxygen and carbon monoxide. Oxygen interacts with liquid metal and oxidizes it. Carbon dioxide in canisters is used in air rifles and pistols.
Aeromodellers use this substance as fuel for their models. With the help of carbon dioxide, you can significantly increase the yield of crops grown in a greenhouse. It is also widely used in industry in which food is preserved much better. It is used as a refrigerant in refrigerators, freezers, electric generators and other thermal power plants.
Other names: carbon dioxide, carbon dioxide, carbon monoxide (IV), carbonic anhydride.
Carbon dioxide is an inorganic compound with the chemical formula CO 2 ; colorless and odorless gas.Physical Properties
Chemical properties and preparation methods
cleaning
Purification of CO 2 stored in steel cylinders. Sales CO 2 in steel cylinders may contain the following impurities: water vapor, O 2 , N 2, less often traces of H 2 S and SO 2. In most cases, commercial CO 2 is of sufficient purity to carry out chemical reactions. Only for higher requirements (for example, in physical research) commercial CO 2 should be subjected to additional purification. To do this, the gas is passed through a saturated solution of CuSO 4 , then through a solution of KHCO 3 and finally through a fractionator, which is part of an industrial plant for producing pure H 2 S . For CO 2 fractionation, four vertical washers, eight U-tubes for deep cooling and two freeze traps are used. Before the last freezer there is also a branch to the mercury manometer. CO 2 passes through the first four U-tubes for deep cooling (kept at the specified temperature) and freezes at 8. When 8 is full, open the valve 9, unsolder at point 10 and create a high vacuum in this part of the apparatus. After that, the remaining four 11-shaped tubes are cooled to -78 ° C (dry ice + 4-acetone), liquid air cooling is removed from 5, the first gas stream is pumped out, and then immersed in a vessel for condensation 11 into liquid air. The middle fraction is collected in 11, and the remainder in 8. The fraction of 11 is sublimated twice more and the gas purity is controlled by determining the vapor pressure at various temperatures. The gas is stored in 25-liter glass flasks, which are degassed by many hours of heating in high vacuum at 350 °C.Fig.1. Installation for the production of hydrogen sulfide.
Dry ice
"Dry ice" - solid carbon dioxide, under normal conditions (atmospheric pressure and room temperature) passing into a vapor state, bypassing the liquid phase. By appearance resembles ice (hence the name).The sublimation temperature at normal pressure is -78.5˚ C. Technical "dry ice" has a density of about 1560 kg / m 3, absorbs about 590 kJ / kg (140 kcal / kg) of heat during sublimation. Produced in carbon dioxide plants.
List of used literature
- Volkov, A.I., Zharsky, I.M. Big chemical reference book / A.I. Volkov, I.M. Zharsky. - Mn.: modern school, 2005. - 608 with ISBN 985-6751-04-7.
- Hoffman W., Rüdorf W., Haas A., Schenk P. W., Huber F., Schmeiser M., Baudler M., Becher H.-J., Dönges E., Schmidbaur H., Erlich P., Seifert H. I Guide to inorganic synthesis: In 6 volumes. T.3. Per. With. German / Ed. G. Brouwer. - M.: Mir, 1985. - 392 p., ill. [With. 682]
The article describes a food additive (gas for saturating drinks, a gaseous environment for packaging and storage) carbon dioxide (E290, carbon dioxide), its use, effects on the body, harm and benefits, composition, consumer reviews
Other additive names: carbon dioxide, carbonic acid anhydride, carbon dioxide, carbonic acid, E290, E-290, E-290Functions performed
beverage saturation gas, packaging and storage gas
Legality of use
Ukraine EU Russia
Carbon dioxide, E290 - what is it?
Carbon dioxide E290 is used in the production of non-alcoholic carbonated drinks Carbon dioxide, also called carbon dioxide, is known as additive E290 in food production. Chemical formula additives E290 - CO 2 . Carbon dioxide under normal conditions is an odorless, colorless gas. Carbon dioxide is readily soluble in water (1 liter of CO 2 in one liter of water at 15 °C) and forms a weak acid.
Carbon dioxide is formed as a result of combustion and biological decomposition (rotting) of various organic substances, in the process of vital activity of living organisms (during decay and decomposition of soil humus, during forest fires, as a result of burning oil products, gas and coal, in the process of respiration of plants, animals and The human body, in which carbon dioxide plays an important role, releases it in an amount approximately equal to 2.3 kg per day.
Carbon dioxide is one of the substances that are very common in nature. Carbon dioxide is present in colossal amounts in the atmosphere and in mineral springs, a significant amount of it is dissolved in the water of the seas and oceans. In the atmosphere of our planet, the concentration of carbon dioxide is approximately equal to 0.04%. The density of carbon dioxide is one and a half times the density of air. This substance is one of the so-called greenhouse gases, and its accumulation in the atmosphere is one of the reasons for the acceleration of global warming. Carbon dioxide is also part of the atmosphere of several planets in our solar system, such as Mars and Venus, and makes up a significant part of it.
In industrial quantities, carbon dioxide is obtained from flue gases or during the decomposition of mineral carbonates (dolomite and limestone), as well as a by-product of alcoholic fermentation. The resulting mixture of gases is subjected to separation, purification and the final product is obtained - pure carbon dioxide. There is also a way to obtain E290 in the production of pure oxygen, argon and nitrogen in air separation plants.
Carbon dioxide, E290 - effect on the body, harm or benefit?
Carbon dioxide is non-toxic and not hazardous to health. It must be remembered that carbon dioxide accelerates absorption into the gastric mucosa various substances, and can cause rapid intoxication when drinking alcoholic beverages containing it. Drinks carbonated with carbon dioxide are actually a dilute solution of weak carbonic acid, therefore, the active use of drinks containing the E290 additive is contraindicated for people who have medical problems with the stomach and gastrointestinal tract (gastritis, ulcers, etc.).
Food additive E290, carbon dioxide - food application
In the food industry, E290 is used as a beverage saturation gas, preservative, antioxidant, acidity regulator and protective gas. Carbon dioxide is widely used in the production of non-alcoholic and alcoholic carbonated drinks. Carbonic acid, which is formed when CO 2 is dissolved in water, exhibits antimicrobial and disinfecting properties.
In the confectionery and bakery industry, the E290 additive is used as a leavening agent, giving volume to confectionery and bakery products. Carbon dioxide is also widely used in winemaking, where it acts as a fermentation regulator. Carbon dioxide is used as a protective gas in the storage of various foods.
