Carbon monoxide

As a result of incomplete combustion of carbon or products containing it, carbon monoxide (CO) or carbon monoxide is formed. Other names of this poisonous substance, which does not have color or smell (it is caused not by carbon monoxide, but by impurities of organic substances), is carbon monoxide (II) or carbon monoxide. Its density at 0 ° C is 0.00125 g / cm3. At a temperature of minus 192 ° С passes from gaseous to liquid state, and at minus 205 ° С - solid. Autoignition temperature is plus 609 ° C. Oxide is slightly soluble in water (0.0026 g in 100 ml), but is soluble in chloroform, acetic acid, ethyl acetate, ethanol, ammonium hydroxide, benzene. Has a molar mass of 28.0101 g / mol.

In addition to the monoxide, other carbon oxides are also known. The most common of these is carbon dioxide or carbon dioxide (CO2), which results from the complete combustion of carbon (free or bound). It is a colorless gas with a slightly acidic taste but no odor. It dissolves well in water, resulting in the formation of acidic carbon monoxide CO (OH) 2 or carbonic acid H2CO3. Tricarbon dioxide (C3O2) is a toxic gas without color, but with a sharp suffocating odor. Under normal conditions, it easily polymerizes, resulting in products that are not soluble in water and painted in red, yellow or purple. There are also other carbon oxides that are less well known and have a linear or cyclic structure. Formulas in this series vary from C2O2 to C32O8. In addition, there is such a polymer substance as graphite oxide, its molecules consist of elements C and O, and the number of both atoms can vary.

Carbon monoxide is obtained as a result of partial oxidation of carbon (under conditions of shortage) to obtain carbon dioxide of oxygen. For example, when a kiln or an internal combustion engine is operating in an enclosed space. In the presence of oxygen, carbon monoxide burns with a blue flame to form carbon dioxide: 2CO + O2 → 2CO2. Coke (or coal) gas, which was widely used until the 60s of the previous century for indoor lighting, cooking and heating, included up to 10% of carbon monoxide in its composition. Since a large amount of heat is released during the combustion of CO, this gas was a valuable component of the fuel. Some processes in modern technologies (for example, smelting of pig iron) are still accompanied by the formation of such a by-product, such as carbon monoxide. Worldwide, the largest source of naturally occurring carbon monoxide is photochemical reactions occurring in the troposphere and generating about 5 • 1012 kg per year. Other natural sources of carbon monoxide are volcanoes, forest fires and other combustion processes.

From the chemical point of view, carbon monoxide is characterized by reducing properties and propensity to join reactions. But these two trends only manifest themselves at elevated temperatures, at which carbon monoxide can be combined with certain metals, chlorine, oxygen and sulfur. In metallurgy, the ability of this substance to heat many oxides to metals is used when heated. When interacting with chlorine, a gas phosgene is formed: CO + Cl2 ↔ COCl2. It is poisonous, used in organic synthesis, can be gradually decomposed with water by the reaction equation: COCl2 + 2H2O → H2CO3 + 2HCl.

Carbon monoxide can be directly attached at elevated temperature and under pressure to certain metals to form metal carbonyls that are complex compounds: Ni (CO) 4, Mo (CO) 6, Fe (CO) 5, and others. Carbon monoxide (II) can react with ammonia on the catalyst (thorium oxide ThO2) at 500 ° C to form hydrogen cyanide: CO + NH3 → HCN + H2O.

Carbon monoxide is a toxic substance for humans and animals. The poisoning properties of carbon monoxide are due to its ability to irreversibly interact with hemoglobin of the blood, as a result of which it loses the ability to transfer oxygen to the cells and tissues of the body. That is, hypoxia of the heme type occurs. Otherwise, it is called (due to a decrease in the oxygen capacity of the blood) blood. Carbon monoxide (II) also takes part in the reactions, disturbing biochemical equilibrium in the tissues of the body. Light poisoning is accompanied by headache, thudding in the temples, dizziness, chest pains, as well as dry cough, lacrimation, nausea, vomiting, visual and auditory hallucinations, reddening of the skin and mucous membranes, tachycardia, increased pressure. At moderate severity, drowsiness occurs and (with consciousness saved) motor paralysis. Severe poisoning is characterized by symptoms such as dilated pupils, loss of consciousness, convulsions, coma, respiratory failure, involuntary feces and urine, blue skin and mucous membranes. Death comes because of cardiac arrest and breathing.