Mass of a chlorine atom. See what “chlorine” is in other dictionaries. Effect on the body
DEFINITION
Chlorine is in the third period of the VII group of the main (A) subgroup of the Periodic table.
Belongs to elements of the p-family. Non-metal. The nonmetallic elements included in this group are collectively called halogens. Designation - Cl. Serial number - 17. Relative atomic mass - 35.453 amu.
Electronic structure of the chlorine atom
The chlorine atom consists of a positively charged nucleus (+17), consisting of 17 protons and 18 neutrons, around which 17 electrons move in 3 orbits.
Fig.1. Schematic structure of the chlorine atom.
The distribution of electrons among orbitals is as follows:
17Cl) 2) 8) 7 ;
1s 2 2s 2 2p 6 3s 2 3p 5 .
The outer energy level of the chlorine atom contains seven electrons, all of which are considered valence electrons. The energy diagram of the ground state takes the following form:
The presence of one unpaired electron indicates that chlorine is capable of exhibiting the +1 oxidation state. Several excited states are also possible due to the presence of vacant 3 d-orbitals. First, electrons 3 are vaporized p-sublevel and occupy free d-orbitals, and then electrons 3 s-sublevel:
This explains the presence of chlorine in three more oxidation states: +3, +5 and +7.
Examples of problem solving
EXAMPLE 1
| Exercise | Given two elements with nuclear charges Z=17 and Z=18. The simple substance formed by the first element is a poisonous gas with a pungent odor, and the second is a non-toxic, odorless, non-respiratory gas. Write the electronic formulas for the atoms of both elements. Which one produces a poisonous gas? |
| Solution | The electronic formulas of the given elements will be written as follows: 17 Z 1 s 2 2s 2 2p 6 3s 2 3p 5 ; 18 Z 1 s 2 2s 2 2p 6 3s 2 3p 6 . The charge on the nucleus of an atom of a chemical element is equal to its atomic number in the Periodic Table. Therefore, it is chlorine and argon. Two chlorine atoms form a molecule of a simple substance - Cl 2, which is a poisonous gas with a pungent odor |
| Answer | Chlorine and argon. |
In the west of Flanders lies a tiny town. Nevertheless, its name is known throughout the world and will long remain in the memory of mankind as a symbol of one of the greatest crimes against humanity. This town is Ypres. Crecy - Ypres - Hiroshima - milestones on the path of turning the war into a gigantic machine of destruction.
At the beginning of 1915, the so-called Ypres salient was formed on the western front line. Allied Anglo-French forces northeast of Ypres penetrated the territory occupied by the German army. The German command decided to launch a counterattack and level the front line. On the morning of April 22, when the wind was blowing smoothly, the Germans began unusual preparations for the offensive - they carried out the first gas attack in the history of war. On the Ypres sector of the front, 6,000 chlorine cylinders were opened simultaneously. Within five minutes, a huge, weighing 180 tons, poisonous yellow-green cloud formed, which slowly moved towards the enemy trenches.
Nobody expected this. The French and British troops were preparing for an attack, for artillery shelling, the soldiers dug in securely, but in front of the destructive chlorine cloud they were completely unarmed. The deadly gas penetrated into all cracks and into all shelters. The results of the first chemical attack (and the first violation of the 1907 Hague Convention on the Non-Use of Chemical Substances!) were stunning - chlorine struck about 15 thousand people, and about 5 thousand died. And all this - in order to level the 6 km long front line! Two months later, the Germans launched a chlorine attack on the eastern front. And two years later, Ypres increased its notoriety. During a difficult battle on July 12, 1917, a toxic substance, later called mustard gas, was used for the first time in the area of this city. Mustard gas is a chlorine derivative, dichlorodiethyl sulfide.
We recall these episodes of history associated with one small town and one chemical element in order to show how dangerous element No. 17 can be in the hands of militant madmen. This is the darkest chapter in the history of chlorine. But it would be completely wrong to see chlorine only as a toxic substance and a raw material for the production of other toxic substances...
The history of elemental chlorine is relatively short, dating back to 1774. The history of chlorine compounds is as old as the world. Suffice it to remember that sodium chloride is table salt. And, apparently, even in prehistoric times, the ability of salt to preserve meat and fish was noticed.
The most ancient archaeological finds - evidence of the use of salt by humans - date back to approximately 3-4 millennium BC. But the oldest description of rock salt mining is found in the writings of the Greek historian Herodotus (5th century BC). Herodotus describes the mining of rock salt in Libya. In the oasis of Sinach in the center of the Libyan Desert there was the famous temple of the god Ammon-Ra. That is why Libya was called “Ammonia”, and the first name for rock salt was “sal ammoniacum”. Later, starting around the 13th century. AD, this name was assigned to ammonium chloride.
Pliny the Elder's Natural History describes a method for separating gold from base metals by calcination with salt and clay. And one of the first descriptions of the purification of sodium chloride is found in the works of the great Arab physician and alchemist Jabir ibn Hayyan (in European spelling - Geber).
It is very likely that alchemists also encountered elemental chlorine, since in the countries of the East already in the 9th century, and in Europe in the 13th century. “Aqua regia” was known - a mixture of hydrochloric and nitric acids. In the book of the Dutchman Van Helmont, Hortus Medicinae, published in 1668, it is said that when ammonium chloride and nitric acid are heated together, a certain gas is obtained. Judging by the description, this gas is very similar to chlorine.
Details chlorine was first described by the Swedish chemist Scheele in his treatise on pyrolusite. While heating the mineral pyrolusite with hydrochloric acid, Scheele noticed an odor characteristic of aqua regia, collected and examined the yellow-green gas that gave rise to this odor, and studied its interaction with certain substances. Scheele was the first to discover the effect of chlorine on gold and cinnabar (in the latter case, sublimate is formed) and the bleaching properties of chlorine.
Scheele did not consider the newly discovered gas to be a simple substance and called it “dephlogisticated hydrochloric acid.” In modern language, Scheele, and after him other scientists of that time, believed that the new gas was the oxide of hydrochloric acid.
Somewhat later, Bertholet and Lavoisier proposed to consider this gas an oxide of a certain new element “murium”. For three and a half decades, chemists tried unsuccessfully to isolate the unknown muria.
At first, Davy was also a supporter of “murium oxide,” who in 1807 decomposed table salt with an electric current into the alkali metal sodium and yellow-green gas. However, three years later, after many fruitless attempts to obtain muria, Davy came to the conclusion that the gas discovered by Scheele was a simple substance, an element, and called it chloric gas or chlorine (from the Greek - yellow-green). And three years later, Gay-Lussac gave the new element a shorter name - chlorine. True, back in 1811, the German chemist Schweiger proposed another name for chlorine - “halogen” (literally translated as salt), but this name did not catch on at first, and later became common for a whole group of elements, which includes chlorine.
“Personal card” of chlorine
To the question, what is chlorine, you can give at least a dozen answers. Firstly, it is halogen; secondly, one of the most powerful oxidizing agents; thirdly, an extremely poisonous gas; fourthly, the most important product of the main chemical industry; fifthly, raw materials for the production of plastics and pesticides, rubber and artificial fiber, dyes and medicines; sixthly, the substance with which titanium and silicon, glycerin and fluoroplastic are obtained; seventh, a means for purifying drinking water and bleaching fabrics...
This list could be continued.
Under normal conditions, elemental chlorine is a rather heavy yellow-green gas with a sharp, characteristic odor. The atomic weight of chlorine is 35.453 and the molecular weight is 70.906 because the chlorine molecule is diatomic. One liter of chlorine gas under normal conditions (temperature 0 ° C and pressure 760 mm Hg) weighs 3.214 g. When cooled to a temperature of - 34.05 ° C, chlorine condenses into a yellow liquid (density 1.56 g / cm 3), and at a temperature of - 101.6°C it hardens. At elevated pressure, chlorine can be converted into liquid at higher temperatures up to +144°C. Chlorine is highly soluble in dichloroethane and some other chlorinated organic solvents.
Element number 17 is very active - it combines directly with almost all elements of the periodic table. Therefore, in nature it is found only in the form of compounds. The most common minerals containing chlorine are halite NaCl, sylvinite KCl NaCl, bischofite MgCl 2 -6H 2 O, carnallite KCl-MgCl 2 -6H 2 O, kainite KCl-MgSO 4 -3H 2 O. This is primarily their “fault” (or "merit") that the chlorine content in the earth's crust is 0.20% by weight. Some relatively rare chlorine-containing minerals, such as horn silver AgCl, are very important for non-ferrous metallurgy.
In terms of electrical conductivity, liquid chlorine ranks among the strongest insulators: it conducts current almost a billion times worse than distilled water, and 1022 times worse than silver.
The speed of sound in chlorine is approximately one and a half times less than in air.
And finally - about chlorine isotopes.
Ten isotopes of this element are now known, but only two are found in nature - chlorine-35 and chlorine-37. The first is about three times larger than the second.
The remaining eight isotopes are obtained artificially. The shortest-lived of them, 32 Cl, has a half-life of 0.306 seconds, and the longest-lived, 36 Cl, has a half-life of 310 thousand years.
ELEMENTARY CALCULATION. When producing chlorine by electrolysis of a solution of table salt, hydrogen and sodium hydroxide are simultaneously obtained: 2NaCl + 2H 2 O = H 2 + Cl 2 + 2NaOH. Of course, hydrogen is a very important chemical product, but there are cheaper and more convenient ways to produce this substance, for example the conversion of natural gas... But caustic soda is produced almost exclusively by electrolysis of solutions of table salt - other methods account for less than 10%. Since the production of chlorine and NaOH is completely interrelated (as follows from the reaction equation, the production of one gram molecule - 71 g of chlorine - is invariably accompanied by the production of two gram molecules - 80 g of electrolytic alkali), knowing the productivity of the workshop (or plant, or state) for alkali , you can easily calculate how much chlorine it produces. Each ton of NaOH is “accompanied” by 890 kg of chlorine.
WELL AND LUBRICANT! Concentrated sulfuric acid is practically the only liquid that does not react with chlorine. Therefore, to compress and pump chlorine, factories use pumps in which sulfuric acid acts as a working fluid and at the same time as a lubricant.
NAME OF FRIEDRICH WELLER. Investigating the interaction of organic substances with chlorine, a French chemist of the 19th century. Jean Dumas made an amazing discovery: chlorine is able to replace hydrogen in the molecules of organic compounds. For example, when acetic acid is chlorinated, first one hydrogen of the methyl group is replaced by chlorine, then another, and a third. But the most striking thing was that the chemical properties of chloroacetic acids differed little from acetic acid itself. The class of reactions discovered by Dumas was completely inexplicable by the electrochemical hypothesis and the theory of Berzelius radicals that were dominant at that time. Berzelius and his students and followers vigorously disputed the correctness of Dumas's work. A mocking letter from the famous German chemist Friedrich Wöhler appeared in the German magazine “Annalen der Chemie und Pharmacie” under the pseudonym S. S. H. Windier (in German “Schwindler” means “liar”, “deceiver”). It reported that the author managed to replace all the carbon, hydrogen and oxygen atoms in fiber (C 6 H 10 O 5) with chlorine, and the properties of the fiber did not change. And now in London they make warm belly pads from cotton wool consisting of pure chlorine.
CHLORINE AND WATER. Chlorine is noticeably soluble in water. At 20°C, 2.3 volumes of chlorine dissolve in one volume of water. Aqueous solutions of chlorine (chlorine water) are yellow. But over time, especially when stored in light, they gradually discolor. This is explained by the fact that dissolved chlorine partially interacts with water, hydrochloric and hypochlorous acids are formed: Cl 2 + H 2 O → HCl + HOCl. The latter is unstable and gradually decomposes into HCl and oxygen. Therefore, a solution of chlorine in water gradually turns into a solution of hydrochloric acid.
But at low temperatures, chlorine and iodine form a crystalline hydrate of unusual composition - Cl 2 * 5 3 / 4 H 2 O. These greenish-yellow crystals (stable only at temperatures below 10 ° C) can be obtained by passing chlorine through ice water. The unusual formula is explained by the structure of the crystalline hydrate, which is determined primarily by the structure of ice. In the crystal lattice of ice, H2O molecules can be arranged in such a way that regularly spaced voids appear between them. A cubic unit cell contains 46 water molecules, between which there are eight microscopic voids. It is in these voids that chlorine molecules settle. The exact formula of chlorine crystalline hydrate should therefore be written as follows: 8Cl 2 * 46H 2 O.
CHLORINE POISONING. The presence of about 0.0001% chlorine in the air irritates the mucous membranes. Constant exposure to such an atmosphere can lead to bronchial disease, sharply impairs appetite, and gives a greenish tint to the skin. If the chlorine content in the air is 0.1%, then acute poisoning can occur, the first sign of which is severe coughing attacks. In case of chlorine poisoning, absolute rest is necessary; It is useful to inhale oxygen or ammonia (sniffing ammonia), or vapors of alcohol with ether. According to existing sanitary standards, the chlorine content in the air of industrial premises should not exceed 0.001 mg/l, i.e. 0.00003%.
NOT ONLY POISON. “Everyone knows that wolves are greedy.” That chlorine is poisonous too. However, in small doses, poisonous chlorine can sometimes serve as an antidote. Thus, victims of hydrogen sulfide are given unstable bleach to smell. By interacting, the two poisons are mutually neutralized.
CHLORINE ANALYSIS. To determine the chlorine content, an air sample is passed through absorbers with an acidified solution of potassium iodide. (Chlorine displaces chlorine, the amount of the latter is easily determined by filtering with a solution of Na 2 S 2 O 3.) To determine trace amounts of chlorine in the air, a colorimetric method is often used, based on a sharp change in the color of some compounds (benzidine, orthotoluidine, methyl orange) when oxidized with chlorine . For example, a colorless acidified solution of benzidine becomes yellow, and a neutral solution becomes blue. The color intensity is proportional to the amount of chlorine.
The physical properties of chlorine are considered: the density of chlorine, its thermal conductivity, specific heat and dynamic viscosity at various temperatures. The physical properties of Cl 2 are presented in the form of tables for the liquid, solid and gaseous states of this halogen.
Basic physical properties of chlorine
Chlorine is included in group VII of the third period of the periodic table of elements at number 17. It belongs to the subgroup of halogens, has relative atomic and molecular masses of 35.453 and 70.906, respectively. At temperatures above -30°C, chlorine is a greenish-yellow gas with a characteristic strong, irritating odor. It liquefies easily under normal pressure (1.013 10 5 Pa), when cooled to -34 ° C, and forms a transparent amber liquid that solidifies at a temperature of -101 ° C.
Due to its high chemical activity, free chlorine does not occur in nature, but exists only in the form of compounds. It is found mainly in the mineral halite (), and is also part of such minerals as sylvite (KCl), carnallite (KCl MgCl 2 6H 2 O) and sylvinite (KCl NaCl). The chlorine content in the earth's crust approaches 0.02% of the total number of atoms of the earth's crust, where it is found in the form of two isotopes 35 Cl and 37 Cl in a percentage ratio of 75.77% 35 Cl and 24.23% 37 Cl.
| Property | Meaning |
|---|---|
| Melting point, °C | -100,5 |
| Boiling point, °C | -30,04 |
| Critical temperature, °C | 144 |
| Critical pressure, Pa | 77.1 10 5 |
| Critical density, kg/m 3 | 573 |
| Gas density (at 0°C and 1.013 10 5 Pa), kg/m 3 | 3,214 |
| Saturated steam density (at 0°C and 3.664 10 5 Pa), kg/m 3 | 12,08 |
| Density of liquid chlorine (at 0°C and 3.664 10 5 Pa), kg/m 3 | 1468 |
| Density of liquid chlorine (at 15.6°C and 6.08 10 5 Pa), kg/m 3 | 1422 |
| Density of solid chlorine (at -102°C), kg/m 3 | 1900 |
| Relative density of gas in air (at 0°C and 1.013 10 5 Pa) | 2,482 |
| Relative density of saturated steam in air (at 0°C and 3.664 10 5 Pa) | 9,337 |
| Relative density of liquid chlorine at 0°C (relative to water at 4°C) | 1,468 |
| Specific volume of gas (at 0°C and 1.013 10 5 Pa), m 3 /kg | 0,3116 |
| Specific volume of saturated steam (at 0°C and 3.664 10 5 Pa), m 3 /kg | 0,0828 |
| Specific volume of liquid chlorine (at 0°C and 3.664 10 5 Pa), m 3 /kg | 0,00068 |
| Chlorine vapor pressure at 0°C, Pa | 3.664 10 5 |
| Dynamic viscosity of gas at 20°C, 10 -3 Pa s | 0,013 |
| Dynamic viscosity of liquid chlorine at 20°C, 10 -3 Pa s | 0,345 |
| Heat of fusion of solid chlorine (at melting point), kJ/kg | 90,3 |
| Heat of vaporization (at boiling point), kJ/kg | 288 |
| Heat of sublimation (at melting point), kJ/mol | 29,16 |
| Molar heat capacity C p of gas (at -73…5727°C), J/(mol K) | 31,7…40,6 |
| Molar heat capacity C p of liquid chlorine (at -101…-34°C), J/(mol K) | 67,1…65,7 |
| Gas thermal conductivity coefficient at 0°C, W/(m K) | 0,008 |
| Thermal conductivity coefficient of liquid chlorine at 30°C, W/(m K) | 0,62 |
| Gas enthalpy, kJ/kg | 1,377 |
| Enthalpy of saturated steam, kJ/kg | 1,306 |
| Enthalpy of liquid chlorine, kJ/kg | 0,879 |
| Refractive index at 14°C | 1,367 |
| Specific electrical conductivity at -70°С, S/m | 10 -18 |
| Electron affinity, kJ/mol | 357 |
| Ionization energy, kJ/mol | 1260 |
Chlorine Density
Under normal conditions, chlorine is a heavy gas with a density approximately 2.5 times higher. Density of gaseous and liquid chlorine under normal conditions (at 0°C) is equal to 3.214 and 1468 kg/m3, respectively. When liquid or gaseous chlorine is heated, its density decreases due to an increase in volume due to thermal expansion.
Density of chlorine gas
The table shows the density of chlorine in the gaseous state at various temperatures (ranging from -30 to 140°C) and normal atmospheric pressure (1.013·10 5 Pa). The density of chlorine changes with temperature - it decreases when heated. For example, at 20°C the density of chlorine is 2.985 kg/m3, and when the temperature of this gas increases to 100°C, the density value decreases to a value of 2.328 kg/m 3.
| t, °С | ρ, kg/m 3 | t, °С | ρ, kg/m 3 |
|---|---|---|---|
| -30 | 3,722 | 60 | 2,616 |
| -20 | 3,502 | 70 | 2,538 |
| -10 | 3,347 | 80 | 2,464 |
| 0 | 3,214 | 90 | 2,394 |
| 10 | 3,095 | 100 | 2,328 |
| 20 | 2,985 | 110 | 2,266 |
| 30 | 2,884 | 120 | 2,207 |
| 40 | 2,789 | 130 | 2,15 |
| 50 | 2,7 | 140 | 2,097 |
As pressure increases, the density of chlorine increases. The tables below show the density of chlorine gas in the temperature range from -40 to 140°C and pressure from 26.6·10 5 to 213·10 5 Pa. With increasing pressure, the density of chlorine in the gaseous state increases proportionally. For example, an increase in chlorine pressure from 53.2·10 5 to 106.4·10 5 Pa at a temperature of 10°C leads to a twofold increase in the density of this gas.
| ↓ t, °С | P, kPa → | 26,6 | 53,2 | 79,8 | 101,3 |
|---|---|---|---|---|
| -40 | 0,9819 | 1,996 | — | — |
| -30 | 0,9402 | 1,896 | 2,885 | 3,722 |
| -20 | 0,9024 | 1,815 | 2,743 | 3,502 |
| -10 | 0,8678 | 1,743 | 2,629 | 3,347 |
| 0 | 0,8358 | 1,678 | 2,528 | 3,214 |
| 10 | 0,8061 | 1,618 | 2,435 | 3,095 |
| 20 | 0,7783 | 1,563 | 2,35 | 2,985 |
| 30 | 0,7524 | 1,509 | 2,271 | 2,884 |
| 40 | 0,7282 | 1,46 | 2,197 | 2,789 |
| 50 | 0,7055 | 1,415 | 2,127 | 2,7 |
| 60 | 0,6842 | 1,371 | 2,062 | 2,616 |
| 70 | 0,6641 | 1,331 | 2 | 2,538 |
| 80 | 0,6451 | 1,292 | 1,942 | 2,464 |
| 90 | 0,6272 | 1,256 | 1,888 | 2,394 |
| 100 | 0,6103 | 1,222 | 1,836 | 2,328 |
| 110 | 0,5943 | 1,19 | 1,787 | 2,266 |
| 120 | 0,579 | 1,159 | 1,741 | 2,207 |
| 130 | 0,5646 | 1,13 | 1,697 | 2,15 |
| 140 | 0,5508 | 1,102 | 1,655 | 2,097 |
| ↓ t, °С | P, kPa → | 133 | 160 | 186 | 213 |
|---|---|---|---|---|
| -20 | 4,695 | 5,768 | — | — |
| -10 | 4,446 | 5,389 | 6,366 | 7,389 |
| 0 | 4,255 | 5,138 | 6,036 | 6,954 |
| 10 | 4,092 | 4,933 | 5,783 | 6,645 |
| 20 | 3,945 | 4,751 | 5,565 | 6,385 |
| 30 | 3,809 | 4,585 | 5,367 | 6,154 |
| 40 | 3,682 | 4,431 | 5,184 | 5,942 |
| 50 | 3,563 | 4,287 | 5,014 | 5,745 |
| 60 | 3,452 | 4,151 | 4,855 | 5,561 |
| 70 | 3,347 | 4,025 | 4,705 | 5,388 |
| 80 | 3,248 | 3,905 | 4,564 | 5,225 |
| 90 | 3,156 | 3,793 | 4,432 | 5,073 |
| 100 | 3,068 | 3,687 | 4,307 | 4,929 |
| 110 | 2,985 | 3,587 | 4,189 | 4,793 |
| 120 | 2,907 | 3,492 | 4,078 | 4,665 |
| 130 | 2,832 | 3,397 | 3,972 | 4,543 |
| 140 | 2,761 | 3,319 | 3,87 | 4,426 |
Density of liquid chlorine
Liquid chlorine can exist in a relatively narrow temperature range, the boundaries of which lie from minus 100.5 to plus 144 ° C (that is, from the melting point to the critical temperature). Above a temperature of 144°C, chlorine will not turn into a liquid state under any pressure. The density of liquid chlorine in this temperature range varies from 1717 to 573 kg/m3.
| t, °С | ρ, kg/m 3 | t, °С | ρ, kg/m 3 |
|---|---|---|---|
| -100 | 1717 | 30 | 1377 |
| -90 | 1694 | 40 | 1344 |
| -80 | 1673 | 50 | 1310 |
| -70 | 1646 | 60 | 1275 |
| -60 | 1622 | 70 | 1240 |
| -50 | 1598 | 80 | 1199 |
| -40 | 1574 | 90 | 1156 |
| -30 | 1550 | 100 | 1109 |
| -20 | 1524 | 110 | 1059 |
| -10 | 1496 | 120 | 998 |
| 0 | 1468 | 130 | 920 |
| 10 | 1438 | 140 | 750 |
| 20 | 1408 | 144 | 573 |
Specific heat capacity of chlorine
The specific heat capacity of chlorine gas C p in kJ/(kg K) in the temperature range from 0 to 1200°C and normal atmospheric pressure can be calculated using the formula:
where T is the absolute temperature of chlorine in degrees Kelvin.
It should be noted that under normal conditions the specific heat capacity of chlorine is 471 J/(kg K) and increases when heated. The increase in heat capacity at temperatures above 500°C becomes insignificant, and at high temperatures the specific heat of chlorine remains virtually unchanged.
The table shows the results of calculating the specific heat of chlorine using the above formula (the calculation error is about 1%).
| t, °С | C p , J/(kg K) | t, °С | C p , J/(kg K) |
|---|---|---|---|
| 0 | 471 | 250 | 506 |
| 10 | 474 | 300 | 508 |
| 20 | 477 | 350 | 510 |
| 30 | 480 | 400 | 511 |
| 40 | 482 | 450 | 512 |
| 50 | 485 | 500 | 513 |
| 60 | 487 | 550 | 514 |
| 70 | 488 | 600 | 514 |
| 80 | 490 | 650 | 515 |
| 90 | 492 | 700 | 515 |
| 100 | 493 | 750 | 515 |
| 110 | 494 | 800 | 516 |
| 120 | 496 | 850 | 516 |
| 130 | 497 | 900 | 516 |
| 140 | 498 | 950 | 516 |
| 150 | 499 | 1000 | 517 |
| 200 | 503 | 1100 | 517 |
At temperatures close to absolute zero, chlorine is in a solid state and has a low specific heat capacity (19 J/(kg K)). As the temperature of solid Cl 2 increases, its heat capacity increases and reaches a value of 720 J/(kg K) at minus 143°C.
Liquid chlorine has a specific heat capacity of 918...949 J/(kg K) in the range from 0 to -90 degrees Celsius. According to the table, it can be seen that the specific heat capacity of liquid chlorine is higher than that of gaseous chlorine and decreases with increasing temperature.
Thermal conductivity of chlorine
The table shows the values of the thermal conductivity coefficients of chlorine gas at normal atmospheric pressure in the temperature range from -70 to 400°C.
The thermal conductivity coefficient of chlorine under normal conditions is 0.0079 W/(m deg), which is 3 times less than at the same temperature and pressure. Heating chlorine leads to an increase in its thermal conductivity. Thus, at a temperature of 100°C, the value of this physical property of chlorine increases to 0.0114 W/(m deg).
| t, °С | λ, W/(m deg) | t, °С | λ, W/(m deg) |
|---|---|---|---|
| -70 | 0,0054 | 50 | 0,0096 |
| -60 | 0,0058 | 60 | 0,01 |
| -50 | 0,0062 | 70 | 0,0104 |
| -40 | 0,0065 | 80 | 0,0107 |
| -30 | 0,0068 | 90 | 0,0111 |
| -20 | 0,0072 | 100 | 0,0114 |
| -10 | 0,0076 | 150 | 0,0133 |
| 0 | 0,0079 | 200 | 0,0149 |
| 10 | 0,0082 | 250 | 0,0165 |
| 20 | 0,0086 | 300 | 0,018 |
| 30 | 0,009 | 350 | 0,0195 |
| 40 | 0,0093 | 400 | 0,0207 |
Chlorine viscosity
The coefficient of dynamic viscosity of gaseous chlorine in the temperature range 20...500°C can be approximately calculated using the formula:
where η T is the coefficient of dynamic viscosity of chlorine at a given temperature T, K;
η T 0 - coefficient of dynamic viscosity of chlorine at temperature T 0 = 273 K (at normal conditions);
C is the Sutherland constant (for chlorine C = 351).
Under normal conditions, the dynamic viscosity of chlorine is 0.0123·10 -3 Pa·s. When heated, the physical property of chlorine, such as viscosity, takes on higher values.
Liquid chlorine has a viscosity an order of magnitude higher than gaseous chlorine. For example, at a temperature of 20°C, the dynamic viscosity of liquid chlorine has a value of 0.345·10 -3 Pa·s and decreases with increasing temperature.
Sources:
- Barkov S. A. Halogens and the manganese subgroup. Elements of group VII of the periodic table of D. I. Mendeleev. A manual for students. M.: Education, 1976 - 112 p.
- Tables of physical quantities. Directory. Ed. acad. I. K. Kikoina. M.: Atomizdat, 1976 - 1008 p.
- Yakimenko L. M., Pasmanik M. I. Handbook on the production of chlorine, caustic soda and basic chlorine products. Ed. 2nd, per. and others. M.: Chemistry, 1976 - 440 p.
In nature, chlorine occurs in a gaseous state and only in the form of compounds with other gases. In conditions close to normal, it is a poisonous, caustic gas of a greenish color. Has more weight than air. Has a sweet smell. A chlorine molecule contains two atoms. In a calm state it does not burn, but at high temperatures it interacts with hydrogen, after which an explosion is possible. As a result, phosgene gas is released. Very poisonous. Thus, even at low concentrations in the air (0.001 mg per 1 dm 3) it can cause death. chlorine states that it is heavier than air, therefore, it will always be located near the floor in the form of a yellowish-green haze.
Historical facts
For the first time in practice, this substance was obtained by K. Scheeley in 1774 by combining hydrochloric acid and pyrolusite. However, only in 1810 P. Davy was able to characterize chlorine and establish that it is a separate chemical element.
It is worth noting that in 1772 he was able to obtain hydrogen chloride, a compound of chlorine and hydrogen, but the chemist was unable to separate these two elements.
Chemical characteristics of chlorine
Chlorine is a chemical element of the main subgroup of group VII of the periodic table. It is in the third period and has atomic number 17 (17 protons in the atomic nucleus). Chemically active non-metal. Denoted by the letters Cl.
It is a typical representative of gases that have no color, but have a pungent, pungent odor. Typically toxic. All halogens are well diluted in water. When exposed to humid air, they begin to smoke.
The external electronic configuration of the Cl atom is 3s2Зр5. Therefore, in compounds, a chemical element exhibits oxidation levels of -1, +1, +3, +4, +5, +6 and +7. The covalent radius of the atom is 0.96 Å, the ionic radius of Cl- is 1.83 Å, the atomic electron affinity is 3.65 eV, the ionization level is 12.87 eV.
As stated above, chlorine is a fairly active non-metal, which makes it possible to create compounds with almost any metals (in some cases using heat or moisture, displacing bromine) and non-metals. In powder form, it reacts with metals only when exposed to high temperatures.
The maximum combustion temperature is 2250 °C. With oxygen it can form oxides, hypochlorites, chlorites and chlorates. All compounds containing oxygen become explosive when interacting with oxidizing substances. It is worth noting that they can explode arbitrarily, while chlorates explode only when exposed to any initiators.
Characteristics of chlorine by position in the periodic system:
Simple substance;
. element of the seventeenth group of the periodic table;
. third period of the third row;
. seventh group of the main subgroup;
. atomic number 17;
. denoted by the symbol Cl;
. reactive non-metal;
. is in the halogen group;
. in conditions close to normal, it is a poisonous gas of a yellowish-green color with a pungent odor;
. a chlorine molecule has 2 atoms (formula Cl 2).
Physical properties of chlorine:
Boiling point: -34.04 °C;
. melting point: -101.5 °C;
. density in the gaseous state - 3.214 g/l;
. density of liquid chlorine (during the boiling period) - 1.537 g/cm3;
. density of solid chlorine - 1.9 g/cm 3 ;
. specific volume - 1.745 x 10 -3 l/g.
Chlorine: characteristics of temperature changes
In the gaseous state it tends to liquefy easily. At a pressure of 8 atmospheres and a temperature of 20 ° C, it looks like a greenish-yellow liquid. Has very high corrosive properties. As practice shows, this chemical element can maintain a liquid state up to a critical temperature (143 ° C), subject to increased pressure.
If it is cooled to a temperature of -32 ° C, it will change to liquid regardless of atmospheric pressure. With a further decrease in temperature, crystallization occurs (at -101 ° C).
Chlorine in nature
The earth's crust contains only 0.017% chlorine. The bulk is found in volcanic gases. As stated above, the substance has great chemical activity, as a result of which it is found in nature in compounds with other elements. However, many minerals contain chlorine. The characteristics of the element allow the formation of about a hundred different minerals. As a rule, these are metal chlorides.
Also, a large amount of it is found in the World Ocean - almost 2%. This is due to the fact that chlorides dissolve very actively and are carried by rivers and seas. The reverse process is also possible. The chlorine is washed back onto the shore, and then the wind carries it around the surrounding area. That is why its greatest concentration is observed in coastal zones. In the arid regions of the planet, the gas we are considering is formed through the evaporation of water, as a result of which salt marshes appear. About 100 million tons of this substance are mined annually in the world. Which, however, is not surprising, because there are many deposits containing chlorine. Its characteristics, however, largely depend on its geographical location.
Methods for producing chlorine
Today there are a number of methods for producing chlorine, of which the most common are the following:
1. Diaphragm. It is the simplest and least expensive. The brine solution in diaphragm electrolysis enters the anode space. Then it flows through the steel cathode grid into the diaphragm. It contains a small amount of polymer fibers. An important feature of this device is counterflow. It is directed from the anode space to the cathode space, which makes it possible to obtain chlorine and alkalis separately.
2. Membrane. The most energy efficient, but difficult to implement in an organization. Similar to diaphragm. The difference is that the anode and cathode spaces are completely separated by a membrane. Therefore, the output is two separate streams.
It is worth noting that the characteristics of the chemical element (chlorine) obtained by these methods will be different. The membrane method is considered to be more “clean”.
3. Mercury method with a liquid cathode. Compared to other technologies, this option allows you to obtain the purest chlorine.
The basic diagram of the installation consists of an electrolyzer and an interconnected pump and amalgam decomposer. The mercury pumped along with a solution of table salt serves as the cathode, and carbon or graphite electrodes serve as the anode. The operating principle of the installation is as follows: chlorine is released from the electrolyte, which is removed from the electrolyzer along with the anolyte. Impurities and residual chlorine are removed from the latter, re-saturated with halite and returned to electrolysis.
Industrial safety requirements and unprofitable production led to the replacement of the liquid cathode with a solid one.
Use of chlorine for industrial purposes
The properties of chlorine allow it to be actively used in industry. With the help of this chemical element, various (vinyl chloride, chlorine rubber, etc.) medicines and disinfectants are obtained. But the largest niche occupied in the industry is the production of hydrochloric acid and lime.
Methods for purifying drinking water are widely used. Today they are trying to move away from this method, replacing it with ozonation, since the substance we are considering negatively affects the human body, and chlorinated water destroys pipelines. This is due to the fact that in the free state Cl has a detrimental effect on pipes made from polyolefins. However, most countries prefer the chlorination method.
Chlorine is also used in metallurgy. With its help, a number of rare metals (niobium, tantalum, titanium) are obtained. In the chemical industry, various organochlorine compounds are actively used to control weeds and for other agricultural purposes; the element is also used as a bleach.
Due to its chemical structure, chlorine destroys most organic and inorganic dyes. This is achieved by completely bleaching them. This result is possible only in the presence of water, because the process of discoloration occurs due to which is formed after the breakdown of chlorine: Cl 2 + H 2 O → HCl + HClO → 2HCl + O. This method found application a couple of centuries ago and is still popular today.
The use of this substance for the production of organochlorine insecticides is very popular. These agricultural products kill harmful organisms while leaving the plants intact. A significant portion of all chlorine produced on the planet is used for agricultural needs.
It is also used in the production of plastic compounds and rubber. They are used to make wire insulation, office supplies, equipment, housings for household appliances, etc. There is an opinion that rubbers obtained in this way are harmful to humans, but this has not been confirmed by science.
It is worth noting that chlorine (the characteristics of the substance were described in detail by us earlier) and its derivatives, such as mustard gas and phosgene, are also used for military purposes to produce chemical warfare agents.
Chlorine as a bright representative of non-metals
Nonmetals are simple substances that include gases and liquids. In most cases, they conduct electricity worse than metals and have significant differences in physical and mechanical characteristics. With the help of a high level of ionization they are able to form covalent chemical compounds. Below we will give a description of a non-metal using chlorine as an example.
As mentioned above, this chemical element is a gas. Under normal conditions, it completely lacks properties similar to those of metals. Without outside help, it cannot interact with oxygen, nitrogen, carbon, etc. It exhibits its oxidizing properties in connections with simple substances and some complex ones. It is a halogen, which is clearly reflected in its chemical properties. In combination with other representatives of halogens (bromine, astatine, iodine), it displaces them. In the gaseous state, chlorine (its characteristics are direct confirmation of this) is highly soluble. Is an excellent disinfectant. It kills only living organisms, which makes it indispensable in agriculture and medicine.
Use as a poisonous substance
The characteristics of the chlorine atom make it possible to use it as a poisonous agent. Gas was first used by Germany on April 22, 1915, during the First World War, as a result of which about 15 thousand people died. At the moment it is not applicable.
Let us give a brief description of the chemical element as an asphyxiant. Affects the human body through suffocation. First it irritates the upper respiratory tract and the mucous membrane of the eyes. A severe cough begins with attacks of suffocation. Further, penetrating into the lungs, the gas corrodes the lung tissue, which leads to edema. Important! Chlorine is a fast-acting substance.
Depending on the concentration in the air, symptoms vary. At low levels, a person experiences redness of the mucous membrane of the eyes and mild shortness of breath. A content of 1.5-2 g/m 3 in the atmosphere causes heaviness and sharp sensations in the chest, sharp pain in the upper respiratory tract. The condition may also be accompanied by severe lacrimation. After 10-15 minutes of being in a room with such a concentration of chlorine, severe lung burns and death occur. At denser concentrations, death is possible within a minute from paralysis of the upper respiratory tract.
Chlorine in the life of organisms and plants
Chlorine is found in almost all living organisms. The peculiarity is that it is not present in pure form, but in the form of compounds.
In animal and human organisms, chlorine ions maintain osmotic equality. This is due to the fact that they have the most suitable radius for penetration into membrane cells. Along with potassium ions, Cl regulates the water-salt balance. In the intestine, chlorine ions create a favorable environment for the action of proteolytic enzymes of gastric juice. Chlorine channels are found in many cells in our body. Through them, intercellular exchange of fluids occurs and the pH of the cell is maintained. About 85% of the total volume of this element in the body resides in the intercellular space. It is eliminated from the body through the urethra. Produced by the female body during breastfeeding.
At this stage of development, it is difficult to say unequivocally which diseases are provoked by chlorine and its compounds. This is due to the lack of research in this area.
Chlorine ions are also present in plant cells. He actively takes part in energy metabolism. Without this element, the process of photosynthesis is impossible. With its help, the roots actively absorb the necessary substances. But a high concentration of chlorine in plants can have a detrimental effect (slowing down the process of photosynthesis, stopping development and growth).
However, there are representatives of the flora who were able to “make friends” or at least get along with this element. The characteristics of a non-metal (chlorine) contain such an item as the ability of a substance to oxidize soils. In the process of evolution, the above-mentioned plants, called halophytes, occupied empty salt marshes, which were empty due to an overabundance of this element. They absorb chlorine ions, and then get rid of them with the help of leaf fall.
Transportation and storage of chlorine
There are several ways to move and store chlorine. The characteristics of the element require special high-pressure cylinders. Such containers have an identification marking - a vertical green line. Cylinders must be thoroughly washed monthly. When chlorine is stored for a long time, a very explosive precipitate is formed - nitrogen trichloride. Failure to comply with all safety rules may result in spontaneous ignition and explosion.
Chlorine study
Future chemists should know the characteristics of chlorine. According to the plan, 9th graders can even conduct laboratory experiments with this substance based on basic knowledge of the discipline. Naturally, the teacher is obliged to provide safety instructions.
The work procedure is as follows: you need to take a flask with chlorine and pour small metal shavings into it. In flight, the shavings will flare up with bright light sparks and at the same time light white SbCl 3 smoke will form. When tin foil is immersed in a vessel with chlorine, it will also spontaneously ignite, and fiery snowflakes will slowly fall to the bottom of the flask. During this reaction, a smoky liquid is formed - SnCl 4. When iron filings are placed in a vessel, red “drops” will form and red FeCl 3 smoke will appear.
Along with practical work, theory is repeated. In particular, such a question as the characteristics of chlorine by position in the periodic table (described at the beginning of the article).
As a result of experiments, it turns out that the element actively reacts to organic compounds. If you place cotton wool, previously soaked in turpentine, in a jar of chlorine, it will instantly ignite and soot will suddenly fall out of the flask. Sodium smolders spectacularly with a yellowish flame, and salt crystals appear on the walls of the chemical container. It will be interesting for students to know that, while still a young chemist, N. N. Semenov (later a Nobel Prize winner), after conducting such an experiment, collected salt from the walls of the flask and, sprinkling it on bread, ate it. Chemistry turned out to be right and did not let the scientist down. As a result of the experiment carried out by the chemist, ordinary table salt actually turned out!
In the west of Flanders lies a tiny town. Nevertheless, its name is known throughout the world and will long remain in the memory of mankind as a symbol of one of the greatest crimes against humanity. This town is Ypres. Crecy (at the Battle of Crecy in 1346, English troops used firearms for the first time in Europe.) - Ypres - Hiroshima - milestones on the path of turning war into a gigantic machine of destruction.
At the beginning of 1915, the so-called Ypres salient was formed on the western front line. Allied Anglo-French forces northeast of Ypres had penetrated into territory held by the German army. The German command decided to launch a counterattack and level the front line. On the morning of April 22, when the wind was blowing smoothly from the northeast, the Germans began unusual preparations for the offensive - they carried out the first gas attack in the history of war. On the Ypres sector of the front, 6,000 chlorine cylinders were opened simultaneously. Within five minutes, a huge, weighing 180 tons, poisonous yellow-green cloud formed, which slowly moved towards the enemy trenches.
Nobody expected this. The French and British troops were preparing for an attack, for artillery shelling, the soldiers dug in securely, but in front of the destructive chlorine cloud they were completely unarmed. The deadly gas penetrated into all cracks and into all shelters. The results of the first chemical attack (and the first violation of the 1907 Hague Convention on the Non-Use of Toxic Substances!) were stunning - chlorine affected about 15 thousand people, with about 5 thousand dying. And all this - in order to level the 6 km long front line! Two months later, the Germans launched a chlorine attack on the eastern front. And two years later, Ypres increased its notoriety. During a difficult battle on July 12, 1917, a toxic substance, later called mustard gas, was used for the first time in the area of this city. Mustard gas is a chlorine derivative, dichlorodiethyl sulfide.
We recall these episodes of history associated with one small town and one chemical element in order to show how dangerous element No. 17 can be in the hands of militant madmen. This is the darkest chapter in the history of chlorine.
But it would be completely wrong to see chlorine only as a toxic substance and a raw material for the production of other toxic substances...
History of chlorine
The history of elemental chlorine is relatively short, dating back to 1774. The history of chlorine compounds is as old as the world. Suffice it to remember that sodium chloride is table salt. And, apparently, even in prehistoric times, the ability of salt to preserve meat and fish was noticed.
The most ancient archaeological finds - evidence of the use of salt by humans - date back to approximately 3...4 millennium BC. And the most ancient description of the extraction of rock salt is found in the writings of the Greek historian Herodotus (5th century BC). Herodotus describes the mining of rock salt in Libya. In the oasis of Sinach in the center of the Libyan Desert there was the famous temple of the god Ammon-Ra. That is why Libya was called “Ammonia”, and the first name for rock salt was “sal ammoniacum”. Later, starting around the 13th century. AD, this name was assigned to ammonium chloride.
Pliny the Elder's Natural History describes a method for separating gold from base metals by calcination with salt and clay. And one of the first descriptions of the purification of sodium chloride is found in the works of the great Arab physician and alchemist Jabir ibn Hayyan (in European spelling - Geber).
It is very likely that alchemists also encountered elemental chlorine, since in the countries of the East already in the 9th century, and in Europe in the 13th century. “Aqua regia” was known - a mixture of hydrochloric and nitric acids. In the book of the Dutchman Van Helmont, Hortus Medicinae, published in 1668, it is said that when ammonium chloride and nitric acid are heated together, a certain gas is obtained. Judging by the description, this gas is very similar to chlorine.
Chlorine was first described in detail by the Swedish chemist Scheele in his treatise on pyrolusite. While heating the mineral pyrolusite with hydrochloric acid, Scheele noticed an odor characteristic of aqua regia, collected and examined the yellow-green gas that gave rise to this odor, and studied its interaction with certain substances. Scheele was the first to discover the effect of chlorine on gold and cinnabar (in the latter case, sublimate is formed) and the bleaching properties of chlorine.
Scheele did not consider the newly discovered gas to be a simple substance and called it “dephlogisticated hydrochloric acid.” In modern language, Scheele, and after him other scientists of that time, believed that the new gas was the oxide of hydrochloric acid.
Somewhat later, Bertholet and Lavoisier proposed to consider this gas an oxide of a certain new element “murium”. For three and a half decades, chemists tried unsuccessfully to isolate the unknown muria.
At first, Davy was also a supporter of “murium oxide,” who in 1807 decomposed table salt with an electric current into the alkali metal sodium and yellow-green gas. However, three years later, after many fruitless attempts to obtain muria, Davy came to the conclusion that the gas discovered by Scheele was a simple substance, an element, and called it chloric gas or chlorine (from the Greek χλωροζ - yellow-green). And three years later, Gay-Lussac gave the new element a shorter name - chlorine. True, back in 1811, the German chemist Schweiger proposed another name for chlorine - “halogen” (literally translated as salt), but this name did not catch on at first, and later became common for a whole group of elements, which includes chlorine.
“Personal card” of chlorine
To the question, what is chlorine, you can give at least a dozen answers. Firstly, it is halogen; secondly, one of the most powerful oxidizing agents; thirdly, an extremely poisonous gas; fourthly, the most important product of the main chemical industry; fifthly, raw materials for the production of plastics and pesticides, rubber and artificial fiber, dyes and medicines; sixthly, the substance with which titanium and silicon, glycerin and fluoroplastic are obtained; seventh, a means for purifying drinking water and bleaching fabrics...
This list could be continued.
Under normal conditions, elemental chlorine is a rather heavy yellow-green gas with a strong, characteristic odor. The atomic weight of chlorine is 35.453, and the molecular weight is 70.906, because the chlorine molecule is diatomic. One liter of chlorine gas under normal conditions (temperature 0 ° C and pressure 760 mm Hg) weighs 3.214 g. When cooled to a temperature of –34.05 ° C, chlorine condenses into a yellow liquid (density 1.56 g / cm 3), and It hardens at a temperature of – 101.6°C. At elevated pressures, chlorine can be liquefied and at higher temperatures up to +144°C. Chlorine is highly soluble in dichloroethane and some other chlorinated organic solvents.
Element number 17 is very active - it directly combines with almost all elements of the periodic table. Therefore, in nature it is found only in the form of compounds. The most common minerals containing chlorine are halite NaCl, sylvinite KCl NaCl, bischofite MgCl 2 6H 2 O, carnallite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 3H 2 O. This is primarily their “fault” " (or "merit") that the chlorine content in the earth's crust is 0.20% by weight. Some relatively rare chlorine-containing minerals, for example horn silver AgCl, are very important for non-ferrous metallurgy.
In terms of electrical conductivity, liquid chlorine ranks among the strongest insulators: it conducts current almost a billion times worse than distilled water, and 10 22 times worse than silver.
The speed of sound in chlorine is approximately one and a half times less than in air.
And finally, about chlorine isotopes.
Nine isotopes of this element are now known, but only two are found in nature - chlorine-35 and chlorine-37. The first is about three times larger than the second.
The remaining seven isotopes are obtained artificially. The shortest-lived of them, 32 Cl, has a half-life of 0.306 seconds, and the longest-lived, 36 Cl, has a half-life of 310 thousand years.
How is chlorine produced?
The first thing you notice when you enter a chlorine plant is the numerous power lines. Chlorine production consumes a lot of electricity - it is needed to decompose natural chlorine compounds.
Naturally, the main chlorine raw material is rock salt. If a chlorine plant is located near a river, then salt is delivered not by rail, but by barge - it’s more economical. Salt is an inexpensive product, but a lot of it is consumed: to get a ton of chlorine, you need about 1.7...1.8 tons of salt.
Salt arrives at warehouses. Three to six months' supplies of raw materials are stored here - chlorine production, as a rule, is large-scale.
The salt is crushed and dissolved in warm water. This brine is pumped through a pipeline to the purification shop, where in huge tanks the height of a three-story building, the brine is cleaned of impurities of calcium and magnesium salts and clarified (allowed to settle). A pure concentrated solution of sodium chloride is pumped to the main chlorine production workshop - the electrolysis workshop.
In an aqueous solution, table salt molecules are converted into Na + and Cl – ions. The Cl ion differs from the chlorine atom only in that it has one extra electron. This means that in order to obtain elemental chlorine, it is necessary to remove this extra electron. This happens in an electrolyzer on a positively charged electrode (anode). It’s as if electrons are “sucked” from it: 2Cl – → Cl 2 + 2 ē . The anodes are made of graphite, because any metal (except platinum and its analogues), taking away excess electrons from chlorine ions, quickly corrodes and breaks down.
There are two types of technological design for the production of chlorine: diaphragm and mercury. In the first case, the cathode is a perforated iron sheet, and the cathode and anode spaces of the electrolyzer are separated by an asbestos diaphragm. At the iron cathode, hydrogen ions are discharged and an aqueous solution of sodium hydroxide is formed. If mercury is used as a cathode, then sodium ions are discharged on it and a sodium amalgam is formed, which is then decomposed by water. Hydrogen and caustic soda are obtained. In this case, a separating diaphragm is not needed, and the alkali is more concentrated than in diaphragm electrolysers.
So, the production of chlorine is simultaneously the production of caustic soda and hydrogen.
Hydrogen is removed through metal pipes, and chlorine through glass or ceramic pipes. Freshly prepared chlorine is saturated with water vapor and is therefore especially aggressive. Subsequently, it is first cooled with cold water in high towers, lined with ceramic tiles on the inside and filled with ceramic packing (the so-called Raschig rings), and then dried with concentrated sulfuric acid. It is the only chlorine desiccant and one of the few liquids with which chlorine does not react.
Dry chlorine is no longer so aggressive; it does not destroy, for example, steel equipment.
Chlorine is usually transported in liquid form in railway tanks or cylinders under pressure up to 10 atm.
In Russia, chlorine production was first organized back in 1880 at the Bondyuzhsky plant. Chlorine was then obtained in principle in the same way as Scheele obtained it in his time - by reacting hydrochloric acid with pyrolusite. All the chlorine produced was used to produce bleach. In 1900, at the Donsoda plant, for the first time in Russia, an electrolytic chlorine production shop was put into operation. The capacity of this workshop was only 6 thousand tons per year. In 1917, all chlorine factories in Russia produced 12 thousand tons of chlorine. And in 1965, the USSR produced about 1 million tons of chlorine...
One of many
All the variety of practical applications of chlorine can be expressed without much of a stretch in one phrase: chlorine is necessary for the production of chlorine products, i.e. substances containing “bound” chlorine. But when talking about these same chlorine products, you can’t get away with one phrase. They are very different - both in properties and in purpose.
The limited space of our article does not allow us to talk about all chlorine compounds, but without talking about at least some substances that require chlorine to be produced, our “portrait” of element No. 17 would be incomplete and unconvincing.
Take, for example, organochlorine insecticides - substances that kill harmful insects, but are safe for plants. A significant portion of the chlorine produced is consumed to obtain plant protection products.
One of the most important insecticides is hexachlorocyclohexane (often called hexachlorane). This substance was first synthesized back in 1825 by Faraday, but it found practical application only more than 100 years later - in the 30s of our century.
Hexachlorane is now produced by chlorinating benzene. Like hydrogen, benzene reacts very slowly with chlorine in the dark (and in the absence of catalysts), but in bright light the chlorination reaction of benzene (C 6 H 6 + 3 Cl 2 → C 6 H 6 Cl 6) proceeds quite quickly.
Hexachlorane, like many other insecticides, is used in the form of dusts with fillers (talc, kaolin), or in the form of suspensions and emulsions, or, finally, in the form of aerosols. Hexachlorane is especially effective in treating seeds and in controlling pests of vegetable and fruit crops. The consumption of hexachlorane is only 1...3 kg per hectare, the economic effect of its use is 10...15 times greater than the costs. Unfortunately, hexachlorane is not harmless to humans...
Polyvinyl chloride
If you ask any schoolchild to list the plastics known to him, he will be one of the first to name polyvinyl chloride (otherwise known as vinyl plastic). From a chemist’s point of view, PVC (as polyvinyl chloride is often referred to in the literature) is a polymer in the molecule of which hydrogen and chlorine atoms are “strung” onto a chain of carbon atoms:
There may be several thousand links in this chain.
And from a consumer point of view, PVC is insulation for wires and raincoats, linoleum and gramophone records, protective varnishes and packaging materials, chemical equipment and foam plastics, toys and instrument parts.
Polyvinyl chloride is formed by the polymerization of vinyl chloride, which is most often obtained by treating acetylene with hydrogen chloride: HC ≡ CH + HCl → CH 2 = CHCl. There is another way to produce vinyl chloride - thermal cracking of dichloroethane.
CH 2 Cl – CH 2 Cl → CH 2 = CHCl + HCl. The combination of these two methods is of interest when HCl, released during cracking of dichloroethane, is used in the production of vinyl chloride using the acetylene method.
Vinyl chloride is a colorless gas with a pleasant, somewhat intoxicating ethereal odor; it polymerizes easily. To obtain the polymer, liquid vinyl chloride is pumped under pressure into warm water, where it is crushed into tiny droplets. To prevent them from merging, a little gelatin or polyvinyl alcohol is added to the water, and in order for the polymerization reaction to begin to develop, a polymerization initiator, benzoyl peroxide, is also added there. After a few hours, the droplets harden and a suspension of the polymer in water is formed. The polymer powder is separated using a filter or centrifuge.
Polymerization usually occurs at temperatures from 40 to 60°C, and the lower the polymerization temperature, the longer the resulting polymer molecules...
We only talked about two substances that require element No. 17 to obtain. Just two out of many hundreds. There are many similar examples that can be given. And they all say that chlorine is not only a poisonous and dangerous gas, but a very important, very useful element.
Elementary calculation
When producing chlorine by electrolysis of a solution of table salt, hydrogen and sodium hydroxide are simultaneously obtained: 2NACl + 2H 2 O = H 2 + Cl 2 + 2NaOH. Of course, hydrogen is a very important chemical product, but there are cheaper and more convenient ways to produce this substance, for example the conversion of natural gas... But caustic soda is produced almost exclusively by electrolysis of solutions of table salt - other methods account for less than 10%. Since the production of chlorine and NaOH is completely interrelated (as follows from the reaction equation, the production of one gram molecule - 71 g of chlorine - is invariably accompanied by the production of two gram molecules - 80 g of electrolytic alkali), knowing the productivity of the workshop (or plant, or state) for alkali , you can easily calculate how much chlorine it produces. Each ton of NaOH is “accompanied” by 890 kg of chlorine.
Well, lube!
Concentrated sulfuric acid is practically the only liquid that does not react with chlorine. Therefore, to compress and pump chlorine, factories use pumps in which sulfuric acid acts as a working fluid and at the same time as a lubricant.
Pseudonym of Friedrich Wöhler
Investigating the interaction of organic substances with chlorine, a French chemist of the 19th century. Jean Dumas made an amazing discovery: chlorine is able to replace hydrogen in the molecules of organic compounds. For example, when acetic acid is chlorinated, first one hydrogen of the methyl group is replaced by chlorine, then another, a third... But the most striking thing was that the chemical properties of chloroacetic acids differed little from acetic acid itself. The class of reactions discovered by Dumas was completely inexplicable by the electrochemical hypothesis and the Berzelius theory of radicals that were dominant at that time (in the words of the French chemist Laurent, the discovery of chloroacetic acid was like a meteor that destroyed the entire old school). Berzelius and his students and followers vigorously disputed the correctness of Dumas's work. A mocking letter from the famous German chemist Friedrich Wöhler under the pseudonym S.S.N. appeared in the German magazine Annalen der Chemie und Pharmacie. Windier (in German “Schwindler” means “liar”, “deceiver”). It reported that the author managed to replace all carbon atoms in fiber (C 6 H 10 O 5). hydrogen and oxygen into chlorine, and the properties of the fiber did not change. And now in London they make warm belly pads from cotton wool consisting... of pure chlorine.
Chlorine and water
Chlorine is noticeably soluble in water. At 20°C, 2.3 volumes of chlorine dissolve in one volume of water. Aqueous solutions of chlorine (chlorine water) are yellow. But over time, especially when stored in light, they gradually discolor. This is explained by the fact that dissolved chlorine partially interacts with water, hydrochloric and hypochlorous acids are formed: Cl 2 + H 2 O → HCl + HOCl. The latter is unstable and gradually decomposes into HCl and oxygen. Therefore, a solution of chlorine in water gradually turns into a solution of hydrochloric acid.
But at low temperatures, chlorine and water form a crystal hydrate of unusual composition - Cl 2 5 3 / 4 H 2 O. These greenish-yellow crystals (stable only at temperatures below 10 ° C) can be obtained by passing chlorine through ice water. The unusual formula is explained by the structure of the crystalline hydrate, which is determined primarily by the structure of ice. In the crystal lattice of ice, H2O molecules can be arranged in such a way that regularly spaced voids appear between them. A cubic unit cell contains 46 water molecules, between which there are eight microscopic voids. It is in these voids that chlorine molecules settle. The exact formula of chlorine crystalline hydrate should therefore be written as follows: 8Cl 2 46H 2 O.
Chlorine poisoning
The presence of about 0.0001% chlorine in the air irritates the mucous membranes. Constant exposure to such an atmosphere can lead to bronchial disease, sharply impairs appetite, and gives a greenish tint to the skin. If the chlorine content in the air is 0.1°/o, then acute poisoning can occur, the first sign of which is severe coughing attacks. In case of chlorine poisoning, absolute rest is necessary; It is useful to inhale oxygen, or ammonia (sniffing ammonia), or alcohol vapor with ether. According to existing sanitary standards, the chlorine content in the air of industrial premises should not exceed 0.001 mg/l, i.e. 0.00003%.
Not only poison
“Everyone knows that wolves are greedy.” That chlorine is poisonous too. However, in small doses, poisonous chlorine can sometimes serve as an antidote. Thus, victims of hydrogen sulfide are given unstable bleach to smell. By interacting, the two poisons are mutually neutralized.
Chlorine test
To determine the chlorine content, an air sample is passed through absorbers with an acidified solution of potassium iodide. (Chlorine displaces iodine, the amount of the latter is easily determined by titration using a solution of Na 2 S 2 O 3). To determine trace amounts of chlorine in the air, a colorimetric method is often used, based on a sharp change in the color of certain compounds (benzidine, orthotoluidine, methyl orange) when oxidized with chlorine. For example, a colorless acidified solution of benzidine becomes yellow, and a neutral solution becomes blue. The color intensity is proportional to the amount of chlorine.
