As a result of incomplete combustion of carbon or products containing it, carbon monoxide (CO) or carbon monoxide is formed. Other names for this toxic substance, which does not have color or smell (it is caused not by carbon monoxide, but by impurities of organic substances), are carbon monoxide (II) or carbon monoxide. Its density at 0 ° C is 0.00125 g / cm³. At a temperature of minus 192 ° it passes from a gaseous state to a liquid state, and at minus 205 ° it is solid. Auto-ignition temperature plus 609 ° C. The oxide is slightly soluble in water (0.0026 g in 100 ml), but it is soluble in chloroform, acetic acid, ethyl acetate, ethanol, ammonium hydroxide, benzene. Has a molar mass of 28.0101 g / mol.
In addition to 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 sour taste, but odorless. It is well soluble in water, resulting in the formation of acidic carbon hydroxide CO (OH) 2 or carbonic acid H2CO3. Tri-carbon dioxide (C3O2) is a colorless poisonous gas with a pungent, suffocating odor. Under normal conditions, it polymerizes easily, resulting in the formation of products that do not dissolve in water and are colored red, yellow or purple. There are also other carbon oxides that are less known and have a linear or cyclic structure. The formulas in this series vary from C2O2 to C32O8. In addition, there is such a polymeric substance as graphite oxide, its molecules are composed of elements C and O, and the number of both atoms can vary.
Carbon monoxide is obtained by partial oxidation of carbon (in conditions of shortage) to produce carbon dioxide oxygen. For example, when operating a furnace or internal combustion engine in a confined 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. Since a large amount of heat is released during the combustion of CO, such a gas was a valuable component of the fuel. Some processes in modern technologies (for example, iron smelting) are still accompanied by the formation of such a by-product as carbon monoxide. Worldwide, the largest source of carbon monoxide of natural origin 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 a chemical point of view, carbon monoxide is characterized by reducing properties and a tendency to addition reactions. But both of these tendencies appear only at elevated temperatures, at which carbon monoxide can combine with some metals, chlorine, oxygen, and sulfur. In metallurgy, the ability of this substance to reduce many oxides to metals is used when heated. When interacting with chlorine, a phosgene gas is formed: CO + Cl2 ↔ COCl2. It is poisonous, is used in organic synthesis, and can gradually decompose with water according to the reaction equation: COCl2 + 2H2O → H2CO3 + 2HCl.
Carbon monoxide can be directly attached at elevated temperatures and under pressure to some metals to form metal carbonyls, which are complex compounds: Ni (CO) 4, Mo (CO) 6, Fe (CO) 5, and others. Carbon monoxide (II) can interact with ammonia on a catalyst (thorium oxide ThO2) at 500 ° with the formation of hydrogen cyanide: CO + NH3 → HCN + H2O.
Carbon monoxide is a toxic substance for humans and animals. The poisonous properties of carbon monoxide are due to its ability to irreversibly interact with blood hemoglobin, as a result of which it loses its ability to transfer oxygen to the cells and tissues of the body. That is, hypoxia of the hemic type occurs. Otherwise, it is called (due to a decrease in the oxygen capacity of the blood) blood. Also, carbon monoxide (II) takes part in the reactions, violating the biochemical balance in the tissues of the body. Mild poisoning is accompanied by headache, temple knocking, dizziness, chest pain, as well as dry cough, lacrimation, nausea, vomiting, visual and auditory hallucinations, redness of the skin and mucous membranes, tachycardia, increased pressure. With moderate severity, drowsiness and (with preserved consciousness) motor paralysis occurs. Severe poisoning is characterized by symptoms such as dilated pupils, loss of consciousness, cramps, coma, respiratory failure, involuntary discharge of feces and urine, and blue skin of the face and mucous membranes. Death occurs due to cardiac arrest and breathing.