Carbon dioxide is called Carbon dioxide liquid (CO2, carbon dioxide, carbon dioxide)

Carbon dioxide is, under normal conditions, a colorless gas with no aromatic characteristics but a slightly sour taste. Under atmospheric pressure, the compound does not exist in a liquid state, but changes from solid to gaseous. Carbon dioxide is called dry ice in the solid phase. Other names for the substance are carbon dioxide, carbon dioxide, carbon monoxide, carbonic anhydride.

The compound is found in mineral springs, air, and is released during the respiration of plants and animals. In living nature, the substance plays an important role, taking part in the metabolic processes of living cells. Carbon dioxide is produced through oxidative reactions in mammals and is released into the atmosphere through respiration. The main source of carbon for plants is atmospheric carbon dioxide.

Carbon dioxide is produced on an industrial scale from flue gases by absorption of monoethanolamine or potassium carbonate. In addition, the compound is obtained in special air separation plants, as a by-product during the extraction of argon, oxygen, and nitrogen.

Applications of carbon dioxide

Due to its properties, carbon dioxide began to be used in the food industry back in the 19th century. One of the brewers discovered an accumulation of gas under the lid of a beer barrel. He decided to try it, and therefore enriched water and beer with this chemical compound. Afterwards, new drinks were served to the guests, who liked the sparkling water. This is how the use of carbon dioxide in the beverage industry began. Subsequently, the chemical properties and composition of the compound were thoroughly studied.

Carbon dioxide, known as a food additive under the number E290, is used as a leavening agent for dough during baking of confectionery products. Carbon dioxide is actively used during the production of soft drinks. Its addition has a positive effect on the refreshing qualities and properties of drinks. In winemaking, the fermentation process is controlled by the addition of carbon dioxide. Some wines are specially enriched with this compound. For better storage of juices, carbon dioxide is also used in low concentrations. In addition, the substance is used as a protective gas during transportation and storage of food products.

Due to its properties, carbon dioxide is used in fire extinguisher cylinders, during wire welding, in air guns, and as an energy source for engines in model aircraft. In solid form, the compound is used to preserve cold in freezers.

The additive number E290 is approved in almost all countries for use in food production.

Effect of carbon dioxide on the human body

Carbon dioxide is found in many living cells of the body and the atmosphere. In this regard, the E290 additive can be considered relatively harmless.

But remember that carbon dioxide helps to enhance the absorption of various substances into the gastric mucosa. This explains the rapid intoxication resulting from the consumption of alcoholic carbonated drinks.

Carbon dioxide is harmful due to side effects such as bloating and belching when drinking carbonated drinks. There is another opinion regarding this dietary supplement, which is as follows: the harm of carbon dioxide is that highly carbonated drinks can leach calcium from the bones.

Physical properties

Chemical properties and methods of preparation

Cleaning

Purification of CO 2 stored in steel cylinders. Commercial 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 allow chemical reactions to occur. Only under higher requirements (for example, during physical research) does commercial CO 2 need to be subjected to additional purification. To do this, the gas is passed through a saturated CuSO 4 solution, then through a KHCO 3 solution and finally through a fractionator, which is part of an industrial plant for the production of pure H 2 S. CO 2 fractionation uses four vertical washers, eight U-tubes for deep cooling and two freeze traps. In front of the last freezer there is also a branch to a mercury manometer. CO 2 passes through the first four U-shaped tubes for deep cooling (maintained at the specified temperature) and is frozen into 8. When 8 is filled, open tap 9, unsolder it at point 10 and create a high vacuum in this part of the equipment. After this, cool the remaining four 11-shaped tubes to -78 °C (dry ice + 4-acetone), remove liquid air cooling from 5, pump out the first gas stream, and then immerse it 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 purity of the gas is monitored by determining the vapor pressure at different temperatures. The gas is stored in 25-liter glass flasks, which are degassed by heating for many hours in a high vacuum at 350 °C.

Fig.1. Installation for producing hydrogen sulfide.

Dry ice

“Dry ice” is solid carbon dioxide, which under normal conditions (atmospheric pressure and room temperature) transforms into a vapor state, bypassing the liquid phase. In appearance it 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, and during sublimation it absorbs about 590 kJ/kg (140 kcal/kg) of heat. 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., Schmeisser M., Baudler M., Becher H.-J., Dönges E., Schmidbaur H., Ehrlich 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]

Carbon dioxide

Carbon monoxide (carbon dioxide, carbon dioxide, carbon dioxide, carbonic anhydride, carbon dioxide ) — CO2, a colorless gas, odorless, with a slightly sour taste.
The concentration of carbon dioxide in the Earth's atmosphere averages 0.038%.
It is not suitable for supporting life. However, it is this that plants “feed” on, turning it into organic substances. In addition, it is a kind of “blanket” for the Earth. If this gas suddenly disappeared from the atmosphere, the Earth would become much cooler and rain would virtually disappear.

"Blanket of the Earth"

Carbon dioxide (carbon dioxide, carbon dioxide, CO 2 ) is formed by combining two elements: carbon and oxygen. It is formed during the combustion of coal or hydrocarbon compounds, during the fermentation of liquids, and also as a product of the respiration of people and animals. It is also found in small quantities in the atmosphere, from where it is assimilated by plants, which, in turn, produce oxygen.
Carbon dioxide is colorless and heavier than air. Freezes at −78.5°C to form snow consisting of carbon dioxide. In aqueous solution it forms carbonic acid, but it is not stable enough to be easily isolated.
Carbon dioxide is the Earth's blanket. It easily transmits ultraviolet rays that heat our planet and reflects infrared rays emitted from its surface into outer space. And if carbon dioxide suddenly disappears from the atmosphere, this will primarily affect the climate. It will become much cooler on Earth, and rain will fall very rarely. It’s not hard to guess where this will ultimately lead.
True, such a catastrophe does not yet threaten us. Quite the contrary. The combustion of organic substances: oil, coal, natural gas, wood - gradually increases the carbon dioxide content in the atmosphere. This means that over time we must expect significant warming and humidification of the earth’s climate. By the way, old-timers believe that it is already noticeably warmer than it was in the days of their youth...
Carbon dioxide is released low temperature liquid, high pressure liquid and gaseous. It is obtained from waste gases from ammonia and alcohol production, as well as from special fuel combustion and other industries. Carbon dioxide gas- colorless and odorless gas at a temperature of 20°C and a pressure of 101.3 kPa (760 mm Hg), density - 1.839 kg/m 3. Liquid carbon dioxide- just a colorless, odorless liquid.
Carbon dioxide non-toxic and non-explosive. At concentrations of more than 5% (92 g/m3), carbon dioxide has a harmful effect on human health - it is heavier than air and can accumulate in poorly ventilated areas near the floor. This reduces the volume fraction of oxygen in the air, which can cause oxygen deficiency and suffocation.

Producing carbon dioxide

In industry, carbon dioxide is obtained from furnace gases, from decomposition products of natural carbonates (limestone, dolomite). The mixture of gases is washed with a solution of potassium carbonate, which absorbs carbon dioxide, turning into bicarbonate. When heated, the bicarbonate solution decomposes, releasing carbon dioxide. During industrial production, gas is pumped into cylinders.
In laboratory conditions, small quantities are obtained by reacting carbonates and bicarbonates with acids, for example, marble with hydrochloric acid.

Application

In the food industry carbon dioxide is used as a preservative and is indicated on the packaging under the code E290
Liquid carbon dioxide(liquid food carbon dioxide) - liquefied carbon dioxide stored under high pressure (~ 65-70 Atm). Colorless liquid. When liquid carbon dioxide is released from a cylinder into the atmosphere, part of it evaporates, and the other part forms dry ice flakes.
Cylinders with liquid carbon dioxide widely used as fire extinguishers and for the production of carbonated water and lemonade.
Carbon dioxide It is used as a protective medium when welding with wire, but at high temperatures it dissociates and releases oxygen. The released oxygen oxidizes the metal. In this regard, it is necessary to introduce deoxidizing agents 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 spattering than when welding in argon or helium.
Carbon dioxide in cans used in air guns and as a power source for engines in aircraft modeling.
Solid carbon dioxide - dry ice- used in glaciers. Liquid carbon dioxide is used as a refrigerant and working fluid in thermal power plants (refrigerators, freezers, solar power generators, etc.).

"Dry ice" and other beneficial properties of carbon dioxide

Carbon dioxide is used quite widely in everyday practice. For example, sparkling water with added aromatic essences is a wonderful refreshing drink. In the food industry, carbon dioxide is also used as a preservative - it is indicated on the packaging under the code E290 , and also as a dough leavening agent.
Carbon dioxide fire extinguishers are used in fires. Biochemists have found that fertilizing... the air with carbon dioxide is a very effective means of increasing the yield of various crops. Perhaps this fertilizer has a single, but significant drawback: it can only be used in greenhouses. At plants that produce carbon dioxide, liquefied gas is packaged in steel cylinders and sent to consumers. If you open the valve, snow comes out with a hiss. What kind of miracle?
Everything is explained simply. The work expended on compressing the gas is significantly less than that required to expand it. And in order to somehow compensate for the resulting deficit, carbon dioxide is sharply cooled, turning into “dry ice”. It is widely used to preserve food and has significant advantages over ordinary ice: firstly, its “cooling capacity” is twice as high per unit weight; secondly, it evaporates without a trace.
Carbon dioxide is used as an active medium in wire welding, since at arc temperature, carbon dioxide decomposes into carbon monoxide CO and oxygen, which, in turn, interacts with the liquid metal, oxidizing it.
Carbon dioxide in cans is used in air guns and as a source of energy for engines in aircraft modeling.

Quality indicators of carbon dioxide GOST 8050-85

Indicator name

Structural formula

True, empirical, or gross formula: CO2

Chemical composition of carbon dioxide

Molecular weight: 44.009

Carbon dioxide (carbon dioxide, carbon dioxide, carbon (IV) oxide, carbonic anhydride) is a colorless gas (under normal conditions), odorless, with a chemical formula CO2. Density under normal conditions is 1.98 kg/m³ (heavier than air). At atmospheric pressure, carbon dioxide does not exist in a liquid state, changing 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 liquid, which is used for its storage. The concentration of carbon dioxide in the Earth's atmosphere averages 0.04%. Carbon dioxide easily transmits ultraviolet rays and rays of the visible part of the spectrum, which come to the 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, upon strong cooling it crystallizes 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 when organic matter rots and burns. Contained in the air and mineral springs, released during the respiration of animals and plants. Soluble in water (1 volume of carbon dioxide in one volume of water at 15 ° C).

According to its chemical properties, carbon dioxide is classified as an acidic oxide. When dissolved in water, it forms carbonic acid. Reacts with alkalis to form carbonates and bicarbonates. It undergoes electrophilic substitution reactions (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 produces 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 is low in the arterial blood. The carbon dioxide content of a blood sample is often expressed in terms of partial pressure, that is, the pressure that a given amount of carbon dioxide contained in a blood sample would have if it alone occupied the entire volume of the blood sample. Carbon dioxide ( CO2) is transported in the blood in three different ways (the exact proportion of each of these three transport methods depends on whether the blood is arterial or venous).

Most of the carbon dioxide (70% to 80%) is converted by the enzyme carbonic anhydrase in red blood cells into bicarbonate ions.
About 5% - 10% of carbon dioxide is dissolved in blood plasma.
About 5% - 10% of carbon dioxide is bound to hemoglobin in the form of carbamine compounds (carbohemoglobin).

Hemoglobin, the main oxygen-transporting protein of 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 globin chains rather than to 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 with oxygen or carbon dioxide also depends on the pH of the environment. These features are very important for the successful uptake and transport of oxygen from the lungs into the tissues and its successful release into the tissues, as well as for the successful uptake and transport of carbon dioxide from the tissues into the lungs and its release there. Carbon dioxide is one of the most important mediators of autoregulation of blood flow. It is a powerful vasodilator. Accordingly, if the level of carbon dioxide in tissue or blood increases (for example, due to intense metabolism - caused by, say, exercise, inflammation, tissue damage, or due to obstruction of blood flow, tissue ischemia), then the capillaries dilate, which leads to increased blood flow and accordingly, to increase 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, cardiac output and, as a consequence, , stroke and minute blood volume. This also helps to correct tissue hypoxia and hypercapnia (increased carbon dioxide levels). Bicarbonate ions are very important for regulating blood pH and maintaining normal acid-base balance. Respiration rate affects the carbon dioxide content 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 regulating respiration. Although our body requires oxygen for metabolism, low oxygen levels in the blood or tissues usually do not stimulate breathing (or rather, the stimulating effect of low oxygen on breathing is too weak and “turns on” late, at very low levels of oxygen in the blood, at which a person often is already losing consciousness). Normally, breathing is stimulated by an increase in the level of carbon dioxide in the blood. The respiratory center is much more sensitive to increased levels of carbon dioxide than to a lack of oxygen. As a consequence, breathing very thin 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 increase 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 the cockpit depressurizes, the pilots can quickly lose consciousness). This feature of the breathing regulation system is also the reason why flight attendants on airplanes instruct passengers in the event of depressurization of the aircraft cabin, first of all, to put on an oxygen mask themselves, before trying to help anyone else - by doing this, the helper risks quickly losing consciousness himself, and even without feeling any discomfort or need for oxygen until the last moment. The human respiratory center tries to maintain the partial pressure of carbon dioxide in arterial blood no higher than 40 mmHg. With conscious hyperventilation, the content of carbon dioxide in arterial blood can decrease to 10-20 mmHg, while the oxygen content in the blood will remain virtually unchanged 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 your breath for a long time than without previous hyperventilation. This deliberate hyperventilation followed by breath holding can lead to loss of consciousness before the person feels the need to take a breath. 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 oxygen supply to the brain will be restored, and then consciousness will be restored). However, in other situations, such as before diving, this can be dangerous (loss of consciousness and the need to take a breath will occur at depth, and without conscious control, water will enter the airways, which can lead to drowning). This is why hyperventilation before diving is dangerous and not recommended.

In industrial quantities, carbon dioxide is released from flue gases, or as a by-product of chemical processes, for example, during the decomposition of natural carbonates (limestone, dolomite) or during the production of alcohol (alcoholic fermentation). The mixture of the resulting gases is washed with a solution of potassium carbonate, which absorbs carbon dioxide, turning into bicarbonate. A solution of bicarbonate decomposes when heated or under reduced pressure, 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, can absorb CO2 contained in the flue gas, and release it when heated; This separates the finished product from other substances. Carbon dioxide is also produced in air separation plants as a by-product of the production of pure oxygen, nitrogen and argon. In the laboratory, 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 slightly soluble calcium sulfate, which interferes with the reaction, and which is removed by a significant excess of acid. To prepare drinks, the reaction of baking soda with citric acid or sour lemon juice can be used. It was in this form that the first carbonated drinks appeared. Pharmacists were engaged in their production and sale.

In the food industry, carbon dioxide is used as a preservative and leavening agent and is indicated on the packaging with code E290. Liquid carbon dioxide is widely used in fire extinguishing systems and fire extinguishers. Automatic carbon dioxide fire extinguishing systems differ in their starting systems, which can be pneumatic, mechanical or electrical. The device for supplying carbon dioxide to the aquarium may include a gas reservoir. The simplest and most common method of producing carbon dioxide is based on the design for making the alcoholic drink mash. 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 and releases oxygen. The released oxygen oxidizes the metal. In this regard, it is necessary to introduce deoxidizing agents 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 spattering than when welding in an inert environment. Carbon dioxide in cans is used in air guns (in gas-cylinder pneumatics) and as an energy source for engines in aircraft modeling. Storing carbon dioxide in a steel cylinder in a liquefied state is more profitable than in the form of 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 regular 40-liter cylinder is 15 MPa (150 kgf/cm²), but it must safely withstand pressure 1.5 times higher, that is, 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, during equipment repair (for example: cooling one of the mating parts during a press-fit), etc. Carbon dioxide is used to liquefy carbon dioxide and produce dry ice. installations.

Measuring the partial pressure of carbon dioxide is required in technological processes, in medical applications - analysis of respiratory mixtures during artificial ventilation 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 carbon dioxide content in exhaled air is called a capnograph. For measuring low concentrations CO2(as well as CO) in process gases or in atmospheric air, you can use the gas chromatographic method with a methanator and registration with a flame ionization detector.

Annual fluctuations in the concentration of atmospheric carbon dioxide on the planet are determined mainly by the vegetation of the middle latitudes (40-70°) of the Northern Hemisphere. Vegetation in the tropics is practically independent of the season, the dry desert belt of 20-30° (in both hemispheres) makes a small contribution to the carbon dioxide cycle, and the strips of land most covered with vegetation are located asymmetrically on Earth (in the Southern Hemisphere there is an ocean in the middle latitudes). Therefore, from March to September, due to photosynthesis, the content CO2 in the atmosphere it decreases, and from October to February it increases. Contributions to winter growth come from both the oxidation of wood (heterotrophic respiration of plants, rotting, decomposition of humus, forest fires) and the combustion of fossil fuels (coal, oil, gas), which increases noticeably in the winter season. 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.

Carbon dioxide is non-toxic, but due to the effect of its increased concentrations in the air on air-breathing living organisms, it is classified as asphyxiating gases (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 to be levels around 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, already at a concentration of 0.1% (this level of carbon dioxide is observed in the air of megacities) people begin to feel weak and drowsy. This shows that even at high oxygen levels, high CO2 concentrations have a significant impact on well-being. Inhalation of air with an increased concentration of this gas does not lead to long-term health problems, and after removing the victim from the polluted atmosphere, complete restoration of health quickly occurs.

Carbon monoxide (carbon dioxide, carbon dioxide, carbon dioxide, carbonic anhydride) - CO 2, a colorless gas (under normal conditions), odorless, with a slightly sour taste.

The concentration of carbon dioxide in the Earth's atmosphere averages 0.0395%.

Carbon dioxide also has physiological significance in animal organisms, for example, it is involved in the regulation of vascular tone (see Arterioles).

Receipt

Carbon dioxide is also produced in air separation plants as a by-product of producing pure oxygen, nitrogen and argon.

In the laboratory, small quantities are prepared by reacting carbonates and bicarbonates with acids, such as marble, chalk, or soda with hydrochloric acid. 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 which is removed by a significant excess of acid.

To prepare drinks, the reaction of baking soda with citric acid or sour lemon juice can be used. It was in this form that the first carbonated drinks appeared. Pharmacists were engaged in their production and sale.

Application

In the food industry, carbon dioxide is used as a preservative and leavening agent and is indicated on the packaging with the code E290.

Liquid carbon dioxide is widely used in fire extinguishing systems, in fire extinguishers and for the production of carbonated water and lemonade.

Carbon dioxide is used as a protective medium in wire welding, but at high temperatures it dissociates and releases oxygen. The released oxygen oxidizes the metal. In this regard, it is necessary to introduce deoxidizing agents 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 spattering than when welding in argon or helium.

When carbon dioxide is used in the gas phase, it is stored under pressure, like a liquefied gas, in the liquid phase. Storing carbon dioxide in a cylinder in a liquefied state is much more profitable than in the form of gas. Carbon dioxide has a relatively low critical temperature of 31°C. When 30 kg of liquefied carbon dioxide is poured into a 40-liter cylinder with a normal pressure of 100 kgf/cm², then at a temperature of 31°C there will be only a liquid phase in the cylinder with a pressure of 100 kgf/cm². If the temperature is higher, you should reduce the filling of the cylinder or use cylinders with a higher operating pressure. If the carbon dioxide is cooled, then at a temperature of 21°C with normal filling, a gas phase will appear in the cylinder.

Solid carbon dioxide - “dry ice” - is used as a refrigerant in laboratory research, in retail, etc.

Registration Methods

Measuring the partial pressure of carbon dioxide is required in technological processes, in medical applications - analysis of respiratory mixtures during artificial ventilation and in closed life support systems. Analysis of CO 2 concentration 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 carbon dioxide content in exhaled air is called a capnograph.

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 latitudes (40-70°) 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 a heavy, colorless and odorless gas compared to air. The impact of its increased concentrations on living organisms classifies it as an asphyxiating gas. (English) Russian . Slight increases in concentration up to 2-4% in unventilated areas lead to the development of drowsiness and weakness. Dangerous concentrations are considered levels of 7-10%, at which suffocation develops, manifesting itself in headache, dizziness, hearing loss and loss of consciousness for a period of time from several minutes to one hour. Poisoning with this gas does not lead to long-term consequences and after its completion the body is completely restored.

Notes

Literature

Vukalovich M.P., Altunin V.V., Thermophysical properties of carbon dioxide, Atomizdat, Moscow, 1965. 456 p.
Tezikov A.D., Production and use of dry ice, Gostorgizdat, Moscow, 1960. 86 p.
Grodnik M.G., Velichansky A.Ya., Design and operation of coal-bed plants, ″Food Industry″, Moscow, 1966. 275 p.
Talyanker Yu.E., Features of storing liquefied gas cylinders, Magazine "Welding Production", No. 11, 1972, Moscow.