Carbon dioxide is often used as a shielding medium for GMAW welding of carbon steels. If this gas is used for other metals, it can provoke the oxidation of welds and worsen the metallurgical properties of the metal. With carbon steels, carbon dioxide interacts in reverse. He attaches beneficial features weld and does not contribute to its deformation.

What is the strength of carbon dioxide for welding?

Using pure carbon dioxide as a shielding medium, you should not count on an incredibly beautiful weld, but in combination with other gases, for example, with argon, you can count on improving the stability of the welding arc, obtaining optimal metal flow in the weld pool, and increasing the strength of welds.

To understand why carbon dioxide is so important for welding, it is worth first answering other questions:

• How is it possible to weld with this gas if it promotes oxidation?
• What makes it so special?

9 facts and benefits of carbon dioxide

Here are some of the main reasons why carbon dioxide is used as a shielding gas for arc welding of carbon steels. 9 facts

improved penetration

As a shielding gas, carbon dioxide provides better penetration and deeper penetration. Thus, the presence in the shielding mixture carbon dioxide improves physicochemical characteristics welded metal in the area of ​​the side wall and root of the weld.

Cost minimization

One of the biggest advantages, which greatly increases the value of carbon dioxide for welding among other shielding gases, is its low cost. By using carbon dioxide instead of oxygen, oxidation in the weld metal can be avoided. Being heavier than oxygen, CO2 provides best performance shielding. But there is one remark. Pure carbon dioxide for welding is cheaper than argon and helium, but in comparison with them, when using it, the quality of the welds becomes worse, there may be welding spatter. Therefore, most often it is used in combination with other gases, thus allowing to increase the productivity of welding work and reduce their cost.

Effective in combination with other gases

As we said, pure carbon dioxide when welding does not give very high results for most metals. But if it is mixed with other gases, a significant improvement in the quality properties of the weld and the parameters of the welding arc can be achieved. For example, in combination with inert gases (the same argon, the ratio of 75% Ar + 25% CO 2 or 82% Ar + 18% CO 2 (according to the standard)), the problem of spatter and arc instability is eliminated.

If a mixture of carbon dioxide (up to 20%), oxygen (up to 5%) and argon is used during welding of carbon and alloy steels with a consumable electrode, then the porosity of the weld can be prevented, the properties of the welding arc can be optimized, and the formation of welds can be improved. Mixtures containing these components are associated as universal. Using them, you can perform welding with different regimes: pulsed and cyclic with a short arc, jet, large-drop and rotary metal transfer. Such mixtures help to weld carbon and low alloy steels of different thicknesses.

Carbon dioxide can be in ternary mixtures (Ar + CO 2 + O 2) or only in combination with pure oxygen (from 2 - 5% to 20% is added). AT last case the double mixture helps to reduce metal losses during spraying by 30-40%, since the transfer of electrode metal becomes small droplets due to surface tension.

It should be noted that binary gas mixtures(Ar + CO 2) are used in the technique of both conventional and pulse-jet metal transfer for most well-known grades of carbon steels, stainless steel.

Weld Undercut Prevention

As you know, carbon dioxide is a denser gas, it reduces the sound vibrations during welding. Thus, the use of carbon dioxide can prevent serious welding defects, which include undercutting the weld.

Security

Carbon dioxide is a non-toxic and non-explosive gas. If you do not comply elementary rules safety, exceeding the permissible concentration of CO 2 more than 92 g / m 3 (5%) in enclosed spaces, containers provokes oxygen deficiency, suffocation.

Good ventilation in the workplace is important step to make your work safer.

Rust protection

Carbon dioxide as a protective medium in welding is the least sensitive to possible rust on the edges (in reasonable limits, of course) and prevents its occurrence in the weld. On the one hand, the use of CO 2 protects the molten metal and the welding arc from the influence ambient atmosphere, on the other hand, this gas decomposes at a high temperature of the arc into carbon monoxide and oxygen, showing an oxidizing effect on the melted metal. To bind oxygen and remove it from the weld pool, an increased amount of deoxidizers, such as silicon and manganese, is important. Carbon dioxide with normal moisture content, when properly combined with other gases, helps prevent welding defects such as porosity, lack of fusion, lack of fusion in the weld metal.

Simplicity and versatility

• Ability to work in different spatial positions in automatic and semi-automatic welding modes.
• No need for devices for supplying and withdrawing flux.

The use of CO 2 is most effective when welding thin carbon steel sheets. This gas is often used in body repair cars, trucks. Here the advantages of having a CO 2 protective environment come to light particularly clearly.

Improving the strength of the weld

In the welding process, the appropriate composition of gases and the appropriate consumables are the primary tools and factors influencing obtaining the required toughness of the metal in the weld. Carbon dioxide in combination with other gases increases the toughness of the welded joint.

Surface tension reduction

Surface tension is another problem for carbon steels. Because of this, melt penetration is worse for them. The weld metal in the molten state acquires a high surface tension, which cannot be reduced when using such inert gases as helium, argon, etc. In this case, carbon dioxide is the only shielding gas capable of reducing the intensity of surface tension, providing better penetration. Thus, the advantages described above make carbon dioxide for welding carbon steels a very important tool for a good weld, especially if we are talking about powder electrodes.

Obsolete - effervescent waters, colloquial - soda.

This is a soft drink made from ordinary flavored or mineral water saturated with carbon dioxide.

Kinds. According to the level of carbon dioxide saturation, there are three types of carbonated water:

Slightly carbonated, at a carbon dioxide saturation level of 0.2-0.3%,

Medium carbonated - 0.3-0.4%,

Highly carbonated - above 0.4%.

Production. Gasification is carried out in two ways.

1. Mechanical - saturation of the liquid with carbon dioxide, mineral and fruit waters, sparkling or sparkling waters and wines. Drinks are carbonated in special devices - saturators, siphons, acratophores, pressurized metal tanks, before which they cool and remove air from the water. Drinks saturate up to 5-10 g / l. During the saturation of water with carbon dioxide, disinfection does not occur.

2. Chemical - the drink is carbonated with carbon dioxide during fermentation: acratophoric and bottled champagne, beer, cider, sparkling wines, bread kvass, or when drinking soda and acid interact - seltzer water (aka soda water).

Alternative gases to carbon dioxide. Carbonated water is produced and sold, it is saturated with either oxygen or a mixture of nitrous oxide and carbon dioxide.

Story. Carbonated natural water known since ancient times. It was used for medicinal purposes. Hippocrates devoted a whole chapter of his work to this water and ordered the sick not only to drink it, but also to bathe in it. Since the 18th century mineral water from sources are bottled and transported around the world. But she was expensive and ran out of steam quickly.

English chemist Joseph Priestley was the first to create carbonated water in 1767.

In 1770, the Swede Tobern Bergman designed an apparatus capable of saturating water with bubbles of carbon dioxide under pressure using a pump, and called it a saturator (saturo - saturate).

The industrial production of carbonated water was first started by Jacob Schwepp. In 1783, he improved the saturator and built a plant for the production of sparkling water.

Properties of carbon dioxide in carbonated water.

Carbon dioxide is highly soluble in water, just like other gases that enter into water with water. chemical interaction: sulfur dioxide, hydrogen sulfide, ammonia and others. Other gases are less soluble in water. Carbon dioxide serves as a preservative and is indicated on the packaging with the code E290.

Impact on health. In foundries, according to the Intersectoral Rules for Labor Protection in the Foundry, devices should be provided that provide workers with salted sparkling water, which includes 0.5% sodium chloride at the rate of 4-5 liters per person per shift.

Too much sugary soda water increases the likelihood of obesity, as well as diabetes. Many countries around the world have introduced a ban on the sale of carbonated drinks on school grounds.

Wow! .. Here, yes! .. Be healthy! ..

Carbon is an incredible element. Arrange carbon atoms in one direction, and they become soft, more pliable than graphite.

Reset the location, and presto! Atoms form a diamond, one of the hardest materials in the world.

Carbon is also a key ingredient for much of life on Earth; the pigment that made the first drawings; and the basis for technological marvels such as graphene, which is a material stronger than steel and more flexible than rubber. [Cm. Periodic Table of the Elements].

Carbon occurs naturally as carbon-12, which makes up nearly 99% of the carbon in the universe; carbon-13, which is about 1%; and carbon-14, which is a negligible amount of total carbon, and this is very important in dating organic objects.

Carbon is unique in its properties because it forms a number of components higher than the total addition of all other elements when combined with each other.

The physical and chemical properties of carbon depend on the crystal structure of the element.

• Atomic number (number of protons in the nucleus): 6
• atomic symbol(on the periodic table elements): with
• Atomic mass (average weight atom): 12.0107
• Density: 2.2670 grams per cubic centimeter
• Phases at room temperature: Solid
• Melting point: 6.422 degrees Fahrenheit (3.550 degrees C)
• Boiling point: 6.872 F (3.800 s) (sublimation)
• Number of isotopes: 15 total; two stable isotopes, in which atoms of one element are located with different amount neutrons.
• The most common isotopes: carbon-12 (6 protons, 6 neutrons and 6 electrons) and carbon-13 (6 protons, 7 neutrons and 6 electrons)
• Vanderwaals radius 0.091 nm
• Ionic radius 0.26 nm (-4) ; 0.015 nm (+4)
• Isotopes 3
• Electronic shells [He] with 2S 2 2P 2
• First ionization energy 1086.1 kJ.mol -1
• Second ionization energy 2351.9 kJ.mol -1
• Third ionization energy 4618.8 kJ.mol -1

Carbon: from stars to life

As the sixth most abundant element in the universe, carbon is formed inside stars in a reaction called the triple alpha process, according to the Center for Astrophysics.

In the old stars that burned most of its hydrogen, the remaining helium is preserved. Each helium nucleus has two protons and two neutrons. At very high temperatures— more than 100,000,000 Kelv. (179.999.540.6 F) - Helium nuclei begin to fuse, first as pairs into unstable 4-proton beryllium nuclei, and eventually, as a sufficient number of beryllium nuclei appear, into beryllium and helium. Final result: atoms with six protons and six neutrons - carbon.

Carbon is a pattern maker. It can bond with itself to form long elastic chains called polymers. It can also bond with four other atoms due to its arrangement of electrons. Atoms are arranged like a nucleus surrounded by an electron cloud, with electrons moving around at different distances from the nucleus. According to the University of California Davis, chemists understand these distances as shells and determine the properties of atoms by what is in each shell.

Carbon has two electron shells, the first of which contains two electrons, and the second contains four of the possible eight spaces. When atoms are bonded, they share electrons in their outer shell. Carbon has four empty spaces in its outer shell, which allows it to bond with four other atoms. (It can also bond stably to fewer atoms by forming double and triple bonds).

In other words, carbon has options. And he uses them: about 10 million carbon compounds have been discovered, and scientists believe that carbon is cornerstone for 95 percent of known compounds. Incredible Ability carbon bonding with many other elements is the main reason that it is critical to almost all life.

Carbon in organisms

The discovery of carbon is history. The element was known prehistoric people in the form of charcoal. According to World Association coal, carbon as coal is still the world's main source of fuel, providing about 30 percent of the world's energy. Coal is also a key ingredient in steelmaking, and graphite, another form of carbon, is a common industrial lubricant.

Carbon-14 is radioactive isotope carbon used by archaeologists for modern organisms and remains. Carbon-14 occurs naturally in the atmosphere. According to Colorado State University, plants take it in through respiration, in which they convert sugars made during photosynthesis into energy that they use to grow and sustain other processes. Living organisms incorporate carbon-14 into their bodies by eating plants or other plant-eating animals. According to the University of Arizona, carbon-14 has a half-life of 5,730 years, meaning that after that time, half of the carbon-14 in the sample has decayed.

Because organisms stop taking in carbon-14 when they die, scientists can use the half-life of carbon-14 as a kind of clock to measure how much time has passed since an organism died. This method works on once-living organisms, including objects made of wood or other plant material.

Carbon gets its name from the Latin word carbo, which means coal.

• Diamonds and graphite are among the hardest and softest natural materials known, respectively. The only difference between them is their crystal structure.
• According to the Encyclopedia of the Earth, carbon makes up 0.032 percent of the Earth's lithosphere (crust and outer mantle). A rough estimate of the weight of the lithosphere by La Salla University geologist David Smith is 300,000,000,000,000,000,000,000 (or 3*10^23) pounds, making the approximate weight of carbon in the lithosphere 10,560,000,000,000,000,000,000,000 (or 1.056*10 ^22) lbs.
• Carbon dioxide (a carbon atom plus two oxygen atoms) is about 0.04 percent earth's atmosphere, according to National Administration Oceanic and Atmospheric Research (NOAA) — an increase from pre-industrial times due to the burning of fossil fuels.
• Carbon monoxide (a carbon atom plus one oxygen atom) is the smell of the gas produced when fossil fuels are burned. Carbon monoxide kills by binding to hemoglobin, oxygen-containing compound in blood. Carbon dioxide binds to hemoglobin 210 times stronger than oxygen, binds to hemoglobin, effectively displacing oxygen.
• Diamond, the brightest version of carbon, forms under great pressure deep in earth's crust. Most large diamond from precious stone that was ever found was the Cullinan diamond, which was discovered in 1905. The rough diamond was 3,106.75 carats. Most big Stone, cut from a 530.2 carat diamond, is one of the Royal Jewels of the United Kingdom and is known as Great Star Africa.
• According to a 2009 study in the journal Archaeological Science, the tattoos of Ötzi the Iceman, 5,300-year-old corpses found in the Alps, were made of carbon. Small incisions were made in the skin and charcoal was rubbed in, possibly as part of an acupuncture treatment.

New carbon molecules

Carbon molecules are a long-studied element, but that doesn't mean it can't be found anymore. In fact, the same element that our prehistoric ancestors burned like charcoal could hold the key to the next generation of technological materials.

In 1985, Rick Smalley and Robert Curl of Rice University in Texas and their colleagues discovered new form carbon. By vaporizing graphite with lasers, scientists have created a mysterious new molecule out of pure carbon, according to the American Chemical Society. This molecule turned out to be a sphere of a ball, consisting of 60 carbon atoms. The new carbon molecule is now better known as the "buckyball". The researchers who discovered it won Nobel Prize in chemistry in 1996. Buckyballs have been found to inhibit the spread of HIV, according to a study published in 2009 in the Journal of Chemical Information and Modeling; medical researchers are working to attach drugs, molecules to molecules, to buckyballs to deliver drugs directly to infection or tumor sites in the body; this includes Columbia University research.

Since then, other new pure molecules carbon - fullerenes, including elliptical and carbon nanotubes with amazing conducting properties. Carbon chemistry is still hot enough. Researchers in Japan and the US are figuring out how to bond carbon atoms together using palladium atoms to make complex new carbon molecules.

Graphene

talking plain language, graphene, is a thin layer of pure carbon; it is a single, densely packed layer of carbon atoms that are held together in a hexagonal hexagonal lattice. Under more complex conditions, it is an allotrope of carbon in the structure of a plane of SP2 atoms with a bond length of 0.142 nm in the molecule. Graphene layers stacked on top of each other form graphite, with an interplanar spacing of 0.335 nm.

This is the thinnest connection known to man, one atom thick, lightweight material is known (about 0.77 milligram per square meter), the strongest compound found (100 to 300 times stronger than steel and with a stiffness strength of 150,000,000 ps), the best conductor of heat, at room temperature (in (4.84±0.44) × 10^3 k (5.30±0.48) × 10^3 W m-1 K s−1). Other known properties graphene its unique light absorption levels in πα ≈ 2.3% white light, and its potential suitability for use in spin transport.

With that in mind, you might be surprised to know that carbon is the second most abundant material in the human body and the fourth most abundant element in the universe (by mass), after hydrogen, helium and oxygen. This makes carbon chemical basis for every known form of life on earth, so graphene could very well be an environmentally friendly, sustainable solution for an almost limitless number of applications. Since the discovery (or, more precisely, mechanical production) of graphene, advances within various scientific disciplines exploded, with huge advances, especially in electronics and biotechnology.

A carbon nanotube (CNT) is a tiny, straw-like structure made up of carbon atoms. These tubes are extremely useful in a wide range electronic, magnetic and mechanical technologies. The diameters of these tubes are so small that they are measured in nanometers. A nanometer is one billionth of a meter, about 10,000 times smaller than a human hair.

Carbon nanotubes are at least 100 times stronger than steel, but only one-sixth as heavy, so they can add strength to almost any material. They are also better than copper at conducting electricity and heat.

Nanotechnology is being used to turn sea water into drinking water. In a new study, scientists at the Lawrence Livermore National Laboratory (LLNL) have developed a carbon nanotube process that can remove salt from sea ​​water much more efficient than traditional technologies.

In the study of nanotubes, scientists mimicked the way biological membranes: essentially a matrix with pores within the membrane. They used especially small nanotubes - more than 50,000 times thinner than a human hair. These tiny nanotubes provide a very high flow of water, but so narrow that only one water molecule can pass through the tube. And most importantly, the salt ions are too large to fit into the tube.

The researchers believe that the new discovery has important consequences for the next generation of both water treatment processes and high flow membrane technologies.

Whether we walk, run, think and even dream - absolutely energy is needed for any actions and processes. When we just lie down, the body continues to expend energy. Even in sleep, energy consumption does not stop for a second: the heart beats, the respiratory muscles contract, the excretory system works and impulses run through the nerves. This continuous exchange of matter and energy is one of the main differences between living organisms and inanimate nature.

Most efficient way getting the cherished calories - oxidative processes with the participation of oxygen. It is in order to provide the body with an endless oxidation of the organic substances contained in it that the process of respiration takes place. Breathing usually means continuous inhalation and exhalation. that make lungs. However, this is external breathing, the first stage of the most complicated process.

Once in the blood, oxygen in the hemoglobin protein moves through circulatory system and delivered to every cell in the body. Where capillaries cannot approach the cell directly, intercellular fluid plays the role of an intermediary. Only in the cell, namely in its part called mitochondria, oxidation processes take place, as a result of which the energy we need is released.

Where does the material for oxidation come from? Food - fats, proteins and carbohydrates - is the fuel that slowly but surely burns in the oxygen "furnace" of our body.

As with any production, there is no waste here. The waste products of respiration are carbon dioxide and water. that leave the body different ways: carbon dioxide follows the same path as oxygen, but in reverse order (cell - blood - lungs), water is removed through the lungs (with water vapor), kidneys (with urine), skin (with sweat) and intestines.

What forces in the lungs cause oxygen to rush into the blood and carbon dioxide to leave it?

Any gas in the mixture (in this case such a mixture will be the air we breathe) has own strength called partial pressure. The same force is possessed by gases dissolved in liquid medium(in our example, the liquid is blood), only here this force is called tension. Both forces are measured in millimeters of mercury. The whole "scene" of the exchange is played out in the pulmonary vesicles - the alveoli, which, like bunches of grapes, hang at the ends of the smallest bronchi. The wall of the alveolus is formed by a layer of alveolar cells, a layer of capillary cells and a layer connective tissue between them and serves as a boundary between air environment lungs and blood capillaries. It is very thin - the total thickness of all three layers is only 1 micron - and is a very small barrier to gases.

If a partial pressure gas in a gas mixture is greater than the voltage of the same gas in a liquid, the gas tends to penetrate into the liquid and dissolve in it, and vice versa, if the pressure of the gas in the liquid is greater than its partial pressure in the gas mixture, the gas leaves the liquid. For example, in nature in this way atmospheric oxygen gets into water bodies - rivers and lakes, and carbon dioxide - from water bodies into the atmosphere.

How does gas exchange take place in the lungs? At sea level, the air we breathe in has a partial pressure of oxygen of about 100 mmHg. Art., and its tension in the venous blood -40 mm Hg. Art. Naturally, oxygen “presses” in a gas more than it “strains” in a liquid, and this force forces it to flow into the blood until the pressure and tension of oxygen are balanced. Blood flows through the capillaries of the lungs in 0.5 s, and half of this time is enough for blood to turn from venous to arterial. In a healthy state of a person, arterial blood is saturated with oxygen by 95-97%.

For carbon dioxide, the picture is reversed. Its partial pressure in the alveoli is 40 mm Hg. Art., and blood pressure - 46 mm Hg. Art., so carbon dioxide is “pushed” out of the blood until equilibrium occurs. It may seem somewhat strange that, despite the smaller difference between voltage and pressure, carbon dioxide leaves the blood 20 times faster than oxygen enters it. This happens because solubility of carbon dioxide 25 times more than oxygen. However, arterial blood always contains a small amount of carbon dioxide along with oxygen.

Breathing is controlled to some extent by consciousness. We can force ourselves to breathe more or less often, or even hold our breath. However, no matter how long we try to hold our breath, there comes a point when it becomes impossible. The signal for the next breath is not lack of oxygen, which might seem logical, but excess carbon dioxide. It is accumulated in the blood carbon dioxide is a physiological stimulant of respiration. After the discovery of the role of carbon dioxide, they began to add it to the gas mixtures of scuba divers in order to stimulate the work of the respiratory center. The same principle is used in anesthesia.

AT normal conditions at rest, a person performs about 15 respiratory cycles, that is, inhalation-exhalation occurs every 4-5 seconds. If you artificially lower the content of carbon dioxide in the blood by hyperventilation, performing six to eight frequent deep breaths and exhalations, then after the last exhalation comes interesting state- for a while the need to breathe disappears. The desire to take a breath appears after about 0.5 minutes instead of the usual 4-5 seconds. This is because during hyperventilation, carbon dioxide is actively removed from the body and its tension in the arterial blood drops significantly. Now it will take more time to excite the respiratory center until the carbon dioxide content reaches right level. What is fraught with hyperventilation for divers, you will learn later.

An example of hypoxia, often leading to death, is poisoning carbon monoxide . Its content is especially high in automobile exhausts. The insidiousness of this gas is that it is colorless and odorless. The only sign of incipient poisoning is an irresistible desire to sleep. Carbon monoxide, like oxygen, combines with hemoglobin, but this bond is 300 times stronger. The longer a person breathes carbon monoxide, the less oxygen remains in his blood. The only thing that can save a person in case of severe poisoning is an urgent blood transfusion, since in this case red blood cells free of carbon monoxide and capable of carrying oxygen will enter the body.

Carbon monoxide poisoning is an extreme case of hypoxia. In general, a person, like other living beings, has a variety of adaptations to deal with a lack of oxygen - increased respiration, increased production of red blood cells and accelerated hemoglobin synthesis. If the oxygen content changes with environment, then only in the direction of decrease, but the body has nothing to protect itself from an excess of oxygen.

Surprisingly, when breathing pure oxygen, poisoning of the body occurs, and then death from asphyxia, that is, suffocation. If the oxygen content in the inhaled air is excessively high, blood hemoglobin is 100% saturated with oxygen, and oxygen molecules that do not have enough space in red blood cells dissolve in the blood and go to “free swimming”. As red blood cells give up oxygen to the cells, its "free-floating" molecules take up the vacated space. Passing through the capillaries, erythrocytes do not have time to take the bulk of carbon dioxide, since 75% of it is transferred to the lungs by erythrocytes and only 25% is dissolved in blood plasma. Then the molecules of carbon dioxide are not the lot, because they can "saddle" the erythrocytes only while they float through the capillaries, since gas exchange occurs exclusively in these vessels. So instead of venous blood, blood full of oxygen flows through the veins, and carbon dioxide remains in the cells and provokes an attack of suffocation.

In the lungs, the blood is again saturated with oxygen in excess of the norm, and history repeats itself. Very quickly, the amount of carbon dioxide in the cells and tissues becomes so noticeable that the face turns red, shortness of breath, headache and convulsions appear (twitching in the muscles of the lips, eyelids, face and fingers and toes), and eventually the person loses consciousness, and " homeless” oxygen continues to put things in order. Its molecules are extremely active and waste oxidative forces right and left. First of all, they destroy cell membranes, which consist mainly of easily oxidized lipid (fat-like) molecules. Several hundred oxidized lipid molecules can start a chain reaction of self-destruction of the entire cell. Decaying molecules are no longer just unable to perform their functions - they are very toxic. destruction of lung cells and blood vessels suffer from heart, liver, brain and spinal cord. In an atmosphere of pure oxygen a person can survive no more than a day.

IT IS INTERESTING

Venous blood is a dark cherry color, and in the tropics it acquires a scarlet hue. This is because in a warm and humid climate, a person needs less energy to maintain vital processes and normal body temperature. Consequently, the body consumes less oxygen, so oxygen-rich blood returns to the veins. The most oxygen-consuming organs are the heart muscle and the brain. There are 2.5-3 thousand capillaries per 1 mm 2 of these organs, while only 0.3-1 thousand capillaries per 1 mm 2 of skeletal muscle.

About 15% of all oxygen that enters the body at rest is consumed by the heart.

When you inhale, the contractions of the heart increase, and when you exhale, they slow down.

The total area of ​​the alveoli in an adult is about 50 times the surface of the body.

Soda, volcano, Venus, refrigerator - what do they have in common? Carbon dioxide. We have collected for you the most interesting information about one of the most important chemical compounds on Earth.

What is carbon dioxide

Carbon dioxide is known mainly for its gaseous state, i.e. as carbon dioxide with simple chemical formula CO2. In this form, it exists under normal conditions - at atmospheric pressure and "normal" temperatures. But at high blood pressure, over 5 850 kPa (such, for example, the pressure on sea ​​depth about 600 m), this gas turns into a liquid. And with strong cooling (minus 78.5 ° C), it crystallizes and becomes the so-called dry ice, which is widely used in trade for storing frozen foods in refrigerators.

Liquid carbon dioxide and dry ice are produced and used in human activities, but these forms are unstable and break down easily.

But gaseous carbon dioxide is ubiquitous: it is released during the respiration of animals and plants and is an important part of chemical composition atmosphere and ocean.

Properties of carbon dioxide

Carbon dioxide CO2 is colorless and odorless. AT normal conditions it has no taste either. However, when inhaling high concentrations of carbon dioxide, a sour taste can be felt in the mouth, caused by the fact that carbon dioxide dissolves on mucous membranes and in saliva, forming weak solution carbonic acid.

By the way, it is the ability of carbon dioxide to dissolve in water that is used to make sparkling waters. Bubbles of lemonade - the same carbon dioxide. The first apparatus for saturating water with CO2 was invented as early as 1770, and already in 1783 the enterprising Swiss Jacob Schwepp began the industrial production of soda ( trademark Schweppes still exists).

Carbon dioxide is 1.5 times heavier than air, so it tends to “settle” in its lower layers if the room is poorly ventilated. The “dog cave” effect is known, where CO2 is released directly from the ground and accumulates at a height of about half a meter. An adult, getting into such a cave, at the height of his height does not feel an excess of carbon dioxide, but dogs find themselves right in a thick layer of carbon dioxide and are poisoned.

CO2 does not support combustion, so it is used in fire extinguishers and fire suppression systems. The trick with extinguishing a burning candle with the contents of an allegedly empty glass (but in fact with carbon dioxide) is based precisely on this property of carbon dioxide.

Carbon dioxide in nature: natural sources

Carbon dioxide is produced in nature from various sources:

• Breathing of animals and plants.
  Every schoolchild knows that plants absorb carbon dioxide CO2 from the air and use it in photosynthesis. Some housewives try with abundance indoor plants atone for shortcomings. However, plants not only absorb but also release carbon dioxide in the absence of light as part of the respiration process. Therefore, the jungle in a poorly ventilated bedroom is not very good idea: CO2 levels will rise even more at night.
• Volcanic activity.
  Carbon dioxide is part of volcanic gases. In areas with high volcanic activity CO2 can be emitted directly from the ground - from cracks and fissures called mofets. The concentration of carbon dioxide in mofet valleys is so high that many small animals die when they get there.
• decomposition of organic matter.
  Carbon dioxide is formed during combustion and decay of organic matter. Volumetric natural emissions of carbon dioxide accompany forest fires.

Carbon dioxide is "stored" in nature in the form of carbon compounds in minerals: coal, oil, peat, limestone. Huge reserves of CO2 are found in dissolved form in the world's oceans.

The release of carbon dioxide from an open reservoir can lead to a limnological catastrophe, as happened, for example, in 1984 and 1986. in lakes Manun and Nyos in Cameroon. Both lakes were formed on the site of volcanic craters - now they are extinct, but in the depths, volcanic magma still emits carbon dioxide, which rises to the waters of the lakes and dissolves in them. As a result of a number of climatic and geological processes, the concentration of carbon dioxide in the waters exceeded the critical value. A huge amount of carbon dioxide was released into the atmosphere, which, like an avalanche, descended along the mountain slopes. About 1,800 people became victims of limnological disasters on the Cameroonian lakes.

Artificial sources of carbon dioxide

The main anthropogenic sources of carbon dioxide are:

• industrial emissions associated with combustion processes;
• automobile transport.

Despite the fact that the share of environmentally friendly transport in the world is growing, the vast majority of the world's population will not soon be able (or willing) to switch to new cars.

Active deforestation for industrial purposes also leads to an increase in the concentration of carbon dioxide CO2 in the air.

CO2 is one of the end products of metabolism (the breakdown of glucose and fats). It is secreted in the tissues and carried by hemoglobin to the lungs, through which it is exhaled. In the air exhaled by a person, there is about 4.5% carbon dioxide (45,000 ppm) - 60-110 times more than in the inhaled air.

Carbon dioxide plays big role in the regulation of blood supply and respiration. An increase in CO2 levels in the blood causes the capillaries to dilate, allowing large quantity blood, which delivers oxygen to the tissues and removes carbon dioxide.

Respiratory system is also stimulated by an increase in carbon dioxide, and not by a lack of oxygen, as it might seem. In fact, the lack of oxygen is not felt by the body for a long time, and it is quite possible that in rarefied air a person will lose consciousness before he feels a lack of air. The stimulating property of CO2 is used in artificial respiration devices: there, carbon dioxide is mixed with oxygen to "start" the respiratory system.

Carbon dioxide and us: why is CO2 dangerous?

Carbon dioxide is needed human body just like oxygen. But just like with oxygen, an excess of carbon dioxide harms our well-being.

A high concentration of CO2 in the air leads to intoxication of the body and causes a state of hypercapnia. In hypercapnia, a person experiences difficulty breathing, nausea, headache, and may even pass out. If the carbon dioxide content does not decrease, then the turn comes - oxygen starvation. The fact is that both carbon dioxide and oxygen move around the body on the same "transport" - hemoglobin. Normally, they "travel" together, attaching to different places on the hemoglobin molecule. However increased concentration carbon dioxide in the blood reduces the ability of oxygen to bind to hemoglobin. The amount of oxygen in the blood decreases and hypoxia occurs.

Such unhealthy consequences for the body occur when inhaling air with a CO2 content of more than 5,000 ppm (this can be the air in mines, for example). To be fair, in ordinary life we practically do not encounter such air. However, even a much lower concentration of carbon dioxide is not good for health.

According to the findings of some, already 1,000 ppm CO2 causes fatigue and headache in half of the subjects. Many people begin to feel closeness and discomfort even earlier. At further increase carbon dioxide concentrations up to 1,500 - 2,500 ppm are critical, the brain is "lazy" to take the initiative, process information and make decisions.

And if the level of 5,000 ppm is almost impossible in Everyday life, then 1,000 and even 2,500 ppm can easily be part of reality modern man. Ours showed that in rarely ventilated school classes CO2 levels stay above 1,500 ppm most of the time, and sometimes jump above 2,000 ppm. There is every reason to believe that the situation is similar in many offices and even apartments.

Physiologists consider 800 ppm as a safe level of carbon dioxide for human well-being.

Another study found a link between CO2 levels and oxidative stress: the higher the level of carbon dioxide, the more we suffer from, which destroys the cells of our body.

Carbon dioxide in the earth's atmosphere

In the atmosphere of our planet, there is only about 0.04% CO2 (this is approximately 400 ppm), and more recently it was even less: carbon dioxide crossed the mark of 400 ppm only in the fall of 2016. Scientists attribute the rise in CO2 levels in the atmosphere to industrialization: in mid-eighteenth century, before industrial revolution, it was only about 270 ppm.