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.
Carbon dioxide is known mainly in its gaseous state, i.e. as carbon dioxide with the simple chemical formula CO2. In this form, it exists under normal conditions - at atmospheric pressure and “ordinary” temperatures. But at increased pressure, above 5,850 kPa (such as, for example, the pressure at a sea depth of about 600 m), this gas turns into liquid. And when strongly cooled (minus 78.5°C), it crystallizes and becomes 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 easily disintegrate.
But carbon dioxide gas is ubiquitous: it is released during the respiration of animals and plants and is an important part of the chemical composition of the atmosphere and ocean.
Carbon dioxide CO2 is colorless and odorless. Under normal conditions it has no taste. However, if you inhale high concentrations of carbon dioxide, you may experience a sour taste in your mouth, caused by the carbon dioxide dissolving on mucous membranes and in saliva, forming a weak solution of carbonic acid.
By the way, it is the ability of carbon dioxide to dissolve in water that is used to make carbonated water. Lemonade bubbles are the same carbon dioxide. The first apparatus for saturating water with CO2 was invented back in 1770, and already in 1783, the enterprising Swiss Jacob Schweppes began industrial production of soda (the Schweppes brand 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, entering such a cave, at the height of his growth does not feel the excess of carbon dioxide, but dogs find themselves directly in a thick layer of carbon dioxide and are poisoned.
CO2 does not support combustion, which is why it is used in fire extinguishers and fire suppression systems. The trick of extinguishing a burning candle with the contents of a supposedly empty glass (but in fact carbon dioxide) is based precisely on this property of carbon dioxide.
Carbon dioxide is formed in nature from various sources:
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 disaster, as happened, for example, in 1984 and 1986. in lakes Manoun and Nyos in Cameroon. Both lakes were formed on the site of volcanic craters - now they are extinct, but in the depths the volcanic magma still releases 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 waters exceeded a critical value. A huge amount of carbon dioxide was released into the atmosphere, which went down the mountain slopes like an avalanche. About 1,800 people became victims of limnological disasters on Cameroonian lakes.
The main anthropogenic sources of carbon dioxide are:
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 have the opportunity (or desire) 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 transported by hemoglobin to the lungs, through which it is exhaled. The air exhaled by humans contains about 4.5% carbon dioxide (45,000 ppm) - 60-110 times more than in the air inhaled.
Carbon dioxide plays a large role in regulating blood flow and respiration. An increase in CO2 levels in the blood causes the capillaries to dilate, allowing more blood to pass through, which delivers oxygen to the tissues and removes carbon dioxide.
The respiratory system is also stimulated by an increase in carbon dioxide, and not by a lack of oxygen, as it might seem. In reality, 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 the lack of air. The stimulating property of CO2 is used in artificial respiration devices: where carbon dioxide is mixed with oxygen to “start” the respiratory system.
Carbon dioxide is necessary for the 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. With hypercapnia, a person experiences difficulty breathing, nausea, headache, and may even lose consciousness. If the carbon dioxide content does not decrease, then oxygen starvation occurs. The fact is that both carbon dioxide and oxygen move throughout the body on the same “transport” - hemoglobin. Normally, they “travel” together, attaching to different places on the hemoglobin molecule. However, increased concentrations of carbon dioxide in the blood reduce 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 never encounter such air. However, a much lower concentration of carbon dioxide does not have the best effect on health.
According to some findings, even 1,000 ppm CO2 causes fatigue and headaches in half of the subjects. Many people begin to feel stuffiness and discomfort even earlier. With a further increase in carbon dioxide concentration to 1,500 – 2,500 ppm critically, the brain is “lazy” to take the initiative, process information and make decisions.
And if a level of 5,000 ppm is almost impossible in everyday life, then 1,000 and even 2,500 ppm can easily be part of the reality of modern man. Ours showed that in rarely ventilated school classrooms, CO2 levels remain above 1,500 ppm much 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 to be a safe level of carbon dioxide for human well-being.
Another study found a link between CO2 levels and oxidative stress: the higher the carbon dioxide level, the more we suffer from oxidative stress, which damages our body's cells.
There is only about 0.04% CO2 in the atmosphere of our planet (this is approximately 400 ppm), and more recently it was even less: carbon dioxide crossed the 400 ppm mark only in the fall of 2016. Scientists attribute the rise in CO2 levels in the atmosphere to industrialization: in the mid-18th century, on the eve of the Industrial Revolution, it was only about 270 ppm.
Carbon dioxide (carbon dioxide, carbon dioxide, CO 2) is formed by the interaction of two elements - oxygen and carbon. Carbon dioxide is produced by the combustion of hydrocarbon compounds or coal, as a result of fermentation of liquids, and also as a product of animal and human respiration. It is found in the atmosphere in small quantities. Plants absorb carbon dioxide from the atmosphere and convert it into organic compounds. When this gas disappears from the atmosphere, there will be virtually no rain on Earth and it will become noticeably cooler.
Carbon dioxide is heavier than air. It freezes at -78 °C. When carbon dioxide freezes, it forms snow. In solution, carbon dioxide forms carbonic acid. Due to certain properties, carbon dioxide is sometimes called the “blanket” of the Earth. It easily passes ultraviolet rays. Infrared rays are emitted from the surface of carbon dioxide into outer space.
Carbon dioxide is released in liquid form at low temperature, liquid form at high pressure, and gaseous form. The gaseous form of carbon dioxide is obtained from waste gases during the production of alcohols, ammonia, and also as a result of fuel combustion. Carbon dioxide gas is a non-toxic and non-explosive gas, odorless and colorless. In liquid form, carbon dioxide is a colorless and odorless liquid. When the content is more than 5%, carbon dioxide accumulates in the floor area in poorly ventilated areas. A decrease in the volume fraction of oxygen in the air can lead to oxygen deficiency and suffocation. Embryologists have found that human and animal cells need about 7% carbon dioxide, and only 2% oxygen. Carbon dioxide is a nervous system tranquilizer and an excellent anesthetic. The gas in the human body is involved in the synthesis of amino acids and has a vasodilating effect. Lack of carbon dioxide in the blood leads to spasm of blood vessels and smooth muscles of all organs, to increased secretion in the nasal passages, bronchi and to the development of polyps and adenoids, to thickening of membranes due to cholesterol deposition.
There are several ways to produce carbon dioxide. In industry, carbon dioxide is obtained from dolomite, limestone - products of the decomposition of natural carbonates, as well as from furnace gases. The gas mixture is washed with a solution of potassium carbonate. The mixture absorbs carbon dioxide and turns into bicarbonate. The bicarbonate solution is heated and it decomposes, releasing carbon dioxide. In the industrial production method, carbon dioxide is pumped into cylinders.
In laboratories, the production of carbon dioxide is based on the interaction of bicarbonates and carbonates with acids.
In everyday practice, carbon dioxide is used quite often. In the food industry, carbon dioxide is used as a leavening agent for dough and also as a preservative. It is indicated on the product packaging under the code E290. The properties of carbon dioxide are also used in the production of sparkling water.
Biochemists have found that to increase the yield of various crops, it is very effective to fertilize the air with carbon dioxide. However, this method of fertilization can only be used in greenhouses. In agriculture, gas is used to create artificial rain. When neutralizing an alkaline environment, carbon dioxide replaces potent mineral acids. In vegetable storage facilities, carbon dioxide is used to create a gaseous environment.
In the perfume industry, carbon dioxide is used in the manufacture of perfumes. In medicine, carbon dioxide is used for antiseptic effects during open operations.
When cooled, carbon dioxide turns into “dry ice.” Liquefied carbon dioxide is packaged in cylinders and sent to consumers. Carbon dioxide in the form of “dry ice” is used to preserve food. When heated, such ice evaporates without leaving a residue.
Carbon dioxide is used as an active medium in wire welding. When welding, carbon dioxide decomposes into oxygen and carbon monoxide. Oxygen interacts with the liquid metal and oxidizes it.
In aircraft modeling, carbon dioxide is used as an energy source for engines. Carbon dioxide canisters are used in air guns.
Carbon dioxide is a colorless gas with a barely perceptible odor, non-toxic, heavier than air. Carbon dioxide is widely distributed in nature. It dissolves in water, forming carbonic acid H 2 CO 3, giving it a sour taste. The air contains about 0.03% carbon dioxide. The density is 1.524 times greater than the density of air and is equal to 0.001976 g/cm 3 (at zero temperature and pressure 101.3 kPa). Ionization potential 14.3V. Chemical formula - CO 2.
In welding production the term is used "carbon dioxide" cm. . In the “Rules for the Design and Safe Operation of Pressure Vessels” the term "carbon dioxide", and in - term "carbon dioxide".
There are many ways to produce carbon dioxide, the main ones are discussed in the article.
The density of carbon dioxide depends on pressure, temperature and the state of aggregation in which it is found. At atmospheric pressure and a temperature of -78.5°C, carbon dioxide, bypassing the liquid state, turns into a white snow-like mass "dry ice".
Under a pressure of 528 kPa and at a temperature of -56.6 ° C, carbon dioxide can be in all three states (the so-called triple point).
Carbon dioxide is thermally stable and dissociates into carbon monoxide only at temperatures above 2000°C.
Carbon dioxide is first gas to be described as a discrete substance. In the seventeenth century, a Flemish chemist Jan Baptist van Helmont (Jan Baptist van Helmont) noticed that after burning coal in a closed vessel, the mass of ash was much less than the mass of the burned coal. He explained this by saying that coal was transformed into an invisible mass, which he called “gas.”
The properties of carbon dioxide were studied much later in 1750. Scottish physicist Joseph Black (Joseph Black).
He discovered that limestone (calcium carbonate CaCO 3), when heated or reacted with acids, releases a gas, which he called “bound air.” It turned out that “bound air” is denser than air and does not support combustion.
CaCO 3 + 2HCl = CO 2 + CaCl 2 + H 2 O
By passing “bound air” i.e. carbon dioxide CO 2 through an aqueous solution of lime Ca(OH) 2 calcium carbonate CaCO 3 is deposited to the bottom. Joseph Black used this experiment to prove that carbon dioxide is released through animal respiration.
CaO + H 2 O = Ca(OH) 2
Ca(OH) 2 + CO 2 = CaCO 3 + H 2 O
Liquid carbon dioxide is a colorless, odorless liquid whose density varies greatly with temperature. It exists at room temperature only at pressures above 5.85 MPa. The density of liquid carbon dioxide is 0.771 g/cm 3 (20°C). At temperatures below +11°C it is heavier than water, and above +11°C it is lighter.
The specific gravity of liquid carbon dioxide varies significantly with temperature, therefore, the amount of carbon dioxide is determined and sold by weight. The solubility of water in liquid carbon dioxide in the temperature range 5.8-22.9°C is no more than 0.05%.
Liquid carbon dioxide turns into gas when heat is supplied to it. Under normal conditions (20°C and 101.3 kPa) When 1 kg of liquid carbon dioxide evaporates, 509 liters of carbon dioxide are formed. When gas is withdrawn too quickly, the pressure in the cylinder decreases and the heat supply is insufficient, the carbon dioxide cools, the rate of its evaporation decreases and when it reaches the “triple point” it turns into dry ice, which clogs the hole in the reduction gear, and further gas extraction stops. When heated, dry ice directly turns into carbon dioxide, bypassing the liquid state. To evaporate dry ice, it is necessary to supply significantly more heat than to evaporate liquid carbon dioxide - therefore, if dry ice has formed in the cylinder, it evaporates slowly.
Liquid carbon dioxide was first produced in 1823. Humphry Davy(Humphry Davy) and Michael Faraday(Michael Faraday).
Solid carbon dioxide "dry ice" resembles snow and ice in appearance. The carbon dioxide content obtained from dry ice briquettes is high - 99.93-99.99%. Moisture content is in the range of 0.06-0.13%. Dry ice, being in the open air, evaporates rapidly, so containers are used for its storage and transportation. Carbon dioxide is produced from dry ice in special evaporators. Solid carbon dioxide (dry ice), supplied in accordance with GOST 12162.
Carbon dioxide is most often used:
The density of carbon dioxide is quite high, which allows the arc reaction space to be protected from contact with air gases and prevents nitriding at relatively low carbon dioxide consumption in the jet. Carbon dioxide is, during the welding process, it interacts with the weld metal and has an oxidizing and also carburizing effect on the metal of the weld pool.
Previously obstacles to the use of carbon dioxide as a protective medium were in the seams. The pores were caused by boiling of the solidifying metal of the weld pool from the release of carbon monoxide (CO) due to its insufficient deoxidation.
At high temperatures, carbon dioxide dissociates to form highly active free, monoatomic oxygen:
Oxidation of the weld metal released free from carbon dioxide during welding is neutralized by the content of an additional amount of alloying elements with a high affinity for oxygen, most often silicon and manganese (in excess of the amount required for alloying the weld metal) or fluxes introduced into the welding zone (welding).
Both carbon dioxide and carbon monoxide are practically insoluble in solid and molten metal. The free active oxidizes the elements present in the weld pool depending on their oxygen affinity and concentration according to the equation:
Me + O = MeO
where Me is a metal (manganese, aluminum, etc.).
In addition, carbon dioxide itself reacts with these elements.
As a result of these reactions, when welding in carbon dioxide, significant burnout of aluminum, titanium and zirconium is observed, and less intense burnout of silicon, manganese, chromium, vanadium, etc.
The oxidation of impurities occurs especially vigorously at . This is due to the fact that when welding with a consumable electrode, the interaction of the molten metal with the gas occurs when a drop remains at the end of the electrode and in the weld pool, and when welding with a non-consumable electrode, it occurs only in the pool. As is known, the interaction of gas with metal in the arc gap occurs much more intensely due to the high temperature and larger contact surface of the metal with the gas.
Due to the chemical activity of carbon dioxide in relation to tungsten, welding in this gas is carried out only with a consumable electrode.
Carbon dioxide is non-toxic and non-explosive. At concentrations of more than 5% (92 g/m3), carbon dioxide has a harmful effect on human health, since 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. Premises where welding is carried out using carbon dioxide must be equipped with general supply and exhaust ventilation. The maximum permissible concentration of carbon dioxide in the air of the working area is 9.2 g/m 3 (0.5%).
Carbon dioxide is supplied by. To obtain high-quality seams, gaseous and liquefied carbon dioxide of the highest and first grades is used.
Carbon dioxide is transported and stored in steel cylinders or large-capacity tanks in a liquid state, followed by gasification at the plant, with a centralized supply to welding stations through ramps. A standard one with a water capacity of 40 liters is filled with 25 kg of liquid carbon dioxide, which at normal pressure occupies 67.5% of the volume of the cylinder and produces 12.5 m 3 of carbon dioxide upon evaporation. Air accumulates in the upper part of the cylinder along with carbon dioxide gas. Water, which is heavier than liquid carbon dioxide, collects at the bottom of the cylinder.
To reduce the humidity of carbon dioxide, it is recommended to install the cylinder with the valve down and, after settling for 10...15 minutes, carefully open the valve and release moisture from the cylinder. Before welding, it is necessary to release a small amount of gas from a normally installed cylinder to remove any air trapped in the cylinder. Some of the moisture is retained in carbon dioxide in the form of water vapor, worsening the welding of the seam.
When gas is released from the cylinder, due to the throttling effect and heat absorption during the evaporation of liquid carbon dioxide, the gas cools significantly. With intensive gas extraction, the reducer may become clogged with frozen moisture contained in carbon dioxide, as well as dry ice. To avoid this, when extracting carbon dioxide, a gas heater is installed in front of the reducer. The final removal of moisture after the gearbox is carried out with a special desiccant filled with glass wool and calcium chloride, silica, copper sulfate or other moisture absorbers
The carbon dioxide cylinder is painted black, with the words “CARBON ACID” written in yellow letters..
You already know that when you exhale, carbon dioxide comes out of your lungs. But what do you know about this substance? Probably a little. Today I will answer all your questions regarding carbon dioxide.
Definition
This substance under normal conditions is a colorless gas. In many sources it can be called differently: and carbon monoxide(IV), and carbonic anhydride, and carbon dioxide, and carbon dioxide.
Properties
Carbon dioxide (formula CO 2) is a colorless gas, has an acidic odor and taste, and is soluble in water. If it is cooled properly, it forms a snow-like mass called dry ice (photo below), which sublimates at a temperature of -78 o C.
Is one of the products of rotting or burning of any organic matter. It dissolves in water only at a temperature of 15 o C and only if the water:carbon dioxide ratio is 1:1. The density of carbon dioxide may vary, but under standard conditions it is equal to 1.976 kg/m3. This is if it is in gaseous form, and in other states (liquid/gaseous) the density values will also be different. This substance is acid oxide, its addition to water produces carbonic acid. If you combine carbon dioxide with any alkali, the subsequent reaction results in the formation of carbonates and bicarbonates. This oxide cannot support combustion, with some exceptions. These are reactive metals, and in this type of reaction they take oxygen away from it.
Receipt
Carbon dioxide and some other gases are released in large quantities when alcohol is produced or natural carbonates decompose. Then the resulting gases are washed with dissolved potassium carbonate. This is followed by their absorption of carbon dioxide, the product of this reaction is bicarbonate, upon heating the solution of which the desired oxide is obtained.
But now it is successfully replaced by ethanolamine dissolved in water, which absorbs carbon monoxide contained in the flue gas and releases it when heated. This gas is also a byproduct of those reactions that produce pure nitrogen, oxygen and argon. In the laboratory, some carbon dioxide is produced when carbonates and bicarbonates react with acids. It is also formed when they react baking soda and lemon juice or the same sodium bicarbonate and vinegar (photo).
Application
The food industry cannot do without the use of carbon dioxide, where it is known as a preservative and leavening agent, code E290. Any fire extinguisher contains it in liquid form.
Also, tetravalent carbon oxide, which is released during the fermentation process, serves as a good feed for aquarium plants. It is also found in the well-known soda, which many people often buy at the grocery store. Wire welding occurs in a carbon dioxide environment, but if the temperature of this process is very high, then it is accompanied by the dissociation of carbon dioxide, which releases oxygen, which oxidizes the metal. Then welding cannot be done without deoxidizing agents (manganese or silicon). Carbon dioxide is used to inflate bicycle wheels; it is also present in the cans of air guns (this type is called a gas cylinder). Also, this oxide in a solid state, called dry ice, is needed as a refrigerant in trade, scientific research and when repairing some equipment.
This is how beneficial carbon dioxide is for humans. And not only in industry, it also plays an important biological role: without it, gas exchange, regulation of vascular tone, photosynthesis and many other natural processes cannot occur. But its excess or shortage in the air for some time can negatively affect the physical condition of all living organisms.
