gaseous iodine. Iodine. Atomic and molecular weight of iodine

5. The thyroid gland needs iodine to produce the hormones thyroxine and triiodothyronine. Lack of iodine leads to swelling of the thyroid gland. Iodine deficiency is considered the main cause of mental retardation. Symptoms with an excess of iodine are similar to those that occur with a deficiency of this element. Iodine is more toxic for people with selenium deficiency.

6. Iodine forms diatomic molecules with the chemical formula I2.

7. Iodine is actively used in medicine. Some people have a chemical sensitivity to iodine. When applied to the skin of iodine, a rash can form. In rare cases, the use of iodine can lead to anaphylactic (allergic) shock.

8. A natural source of iodine in the human diet is seafood, kelp (seaweed), growing in iodine-rich sea waters. Potassium iodine is often added to table salt. This is how iodized salt known to many culinary specialists is obtained.

9. The atomic number of iodine is 53. This means that each iodine atom contains 53 protons.

The Encyclopedia Britannica tells how iodine was discovered by mankind. In 1811, the French chemist Bernard Courtois, heating seaweed ash in sulfuric acid, saw a purple vapor. Condensed, this vapor became a black crystalline substance, which was called "substance X". In 1813, the British chemist Sir Humphry Davy, while on his way to Italy, passing through Paris, suggested that "substance X" was a chemical element similar to chlorine and suggested calling it iodine (English "iodine" - "iodine") for purple the color of its gaseous form.

Iodine is never found in nature in a free state and is not concentrated in quantities sufficient to form an independent mineral. Iodine is contained in, but in small quantities as the I- ion in the salt of hydroiodic acid (iodide). The iodine content is approximately 50 milligrams per metric ton (1,000 kilograms) of sea water. It is also found in seaweed, oysters and cod liver. The human body contains iodine as part of the hormone thyroxine produced by the thyroid gland.


The only natural isotope of iodine is stable iodine-127. The radioactive isotope iodine-131 with a half-life of eight days is actively used. It is used in medicine to check the functions of the thyroid gland, to treat goiter and thyroid cancer. And also for the localization of tumors of the brain and liver.


What iodine-rich seafood do you know? Do you think seafood is not only healthy, but also delicious? It is believed that nori seaweed, which is used in the preparation of sushi, contains too much iodine, and therefore is harmful to humans. How does this information influence your attitude to the now fashionable Japanese cuisine and does it influence at all?

DEFINITION

Iodine is located in the fifth period of the VII group of the main (A) subgroup of the Periodic Table.

Relates to elements p-families. Non-metal. Designation - I. Ordinal number - 53. Relative atomic mass - 126.905 a.m.u.

The electronic structure of the iodine atom

The iodine atom consists of a positively charged nucleus (+53), inside which there are 53 protons and 74 neutrons, and 53 electrons move around in five orbits.

Fig.1. Schematic structure of the iodine atom.

The distribution of electrons in orbitals is as follows:

53Te) 2) 8) 18) 18) 7 ;

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 5 .

The outer energy level of the iodine atom contains 7 electrons, which are valence. The energy diagram of the ground state takes the following form:

The valence electrons of an iodine atom can be characterized by a set of four quantum numbers: n(chief quantum), l(orbital), m l(magnetic) and s(spin):

Examples of problem solving

EXAMPLE 1

When iodine is mentioned, most of us think of a small vial and a cotton swab. This is how our mothers treated scratches and abrasions in childhood. And today you can find such iodine, the price in a pharmacy for it is cheap.

Many adults know that iodine is a very important trace element. It affects the functioning of the thyroid gland and is involved in the metabolic process. Iodine-containing drugs will have a price an order of magnitude higher than a vial for treating wounds. What is iodine made from? And why is the price so different?

What is iodine?

Iodine is a mineral that is found in inorganic compounds: water, soil, after rain it can be found in the air. It is also present in many plant and animal foods. So, it is well known that there is a lot of iodine in kelp, as well as other seafood: fish, shellfish, crustaceans.

Iodine is also found in common foods that are well known to us: eggs, beef, milk, butter, ordinary cabbage, other vegetables, and cereals. The problem is that they don't have enough of it. So, for example, cod liver (it is believed that it has a lot of iodine) contains 800 micrograms of the mineral, and in order to satisfy the daily requirement, you need to eat 180 g of this product daily.

When deciding what is better - brilliant green or iodine, we do not think about how important iodine is in a person's daily life.

An adult needs 150 micrograms of iodine per day, and pregnant women need 200 micrograms. The norm for infants is 50 micrograms, and for a student - 120 micrograms.

Another problem associated with the delivery of this substance to the human body will be its destruction during the preparation process. So, during cooking, about 50% of this useful substance is lost. A pack in a month will contain only 50% of the declared amount.

Growing plants on soils that are poor in the mineral will significantly reduce its amount in the respective food products.

Here, the solution to the problem can be called a medical price in a pharmacy for them, but often far from publicly available.

Medical uses of iodine

Why is this mineral, found in very small amounts in the human body, so important to us?

It is only about 25 milligrams, but it plays a very important role in metabolic processes. So, about 15 mg of iodine is in the thyroid gland and is part of the hormones triiodothyronine and thyroxine formed by it. These hormones are responsible for many functions:

• have a stimulating effect on the growth and development of the body as a whole;
• regulate energy and heat exchange;
• participate in the oxidation of carbohydrates, fats and proteins;
• accelerate the process of cholesterol breakdown;
• without them, the regulation of cardiac activity is not complete;
• they interfere with the process of blood clotting and the formation of blood clots;
• they are very important for the development of the central nervous system.

The remaining 10 mg were located in the reproductive organs of the ovaries (in women) and the prostate gland (in men), kidneys, liver, hair and nails.

The lack of this substance in the body of a child can cause a delay in his physical and mental development, and its excess will lead to poisoning called "iodism", possibly to disruption of the thyroid gland, a formidable disease called "hyperthyroidism".

For different purposes, the pharmacological industry produces different drugs. Today, medicines containing easily digestible iodine are expensive. And this is due not only to the technological process of manufacturing the drug, but also to the fact that the extraction of iodine itself is technologically complex and financially costly.

Many people are interested in the simple question of which is better - brilliant green or iodine when treating fresh wounds? It should be remembered here that iodine will not only prevent the development of the fungus and destroy the infection, Zelenka also copes well with this. It will promote faster healing of the wound - and in this case, iodine is more preferable.

Industrial use of the mineral

Iodine is important not only for ensuring the normal life cycle of a person, it is used in many industries, it is needed for the production of a large number of products.

So, with the participation of this substance, X-ray images are taken, photographs are taken, added to bearing oil, glasses for headlights and lamps with special effects are produced with its participation, it is needed to obtain high-purity metals.

Today, a new direction is developing in the production of incandescent lamps, where iodine plays an important role. Its use will significantly extend the life of conventional incandescent lamps with a tungsten filament.

According to statistics, 99% of known iodine reserves are located in Japan and Chile, they are the main suppliers of it to the world market. Thus, Chilean companies produce over 720 tons of iodine per year.

The production capacities of Russia allow producing up to 200 tons of raw mineral per year, which is 6 times less than the country's needs.

Extraction of iodine from seaweed

The question of the need for industrial extraction of this substance arose in the 18th century. Even then, it was noticed that marine plants have an increased content of this important mineral. The first industrial production was the extraction of iodine from seaweed. In Russia, such a plant was built in Yekaterinburg (1915), it produced a mineral from phylloflora (Black Sea algae).

Today, the extraction of this raw mineral from algae is the most common method for obtaining iodine on an industrial scale. Production is built near the sea, during the process they are extracted from the ashes of a dried sea plant. The largest enterprises extract up to 300 tons of crystalline mineral per year.

Sea kelp is classified as the main source of industrial production of iodine. It contains 0.8-0.16% iodine (in dry matter).

Isolation of the mineral from saltpeter waste

Isolation of iodine from mother brines of saltpeter production is one of the cheapest industrial methods. Here, to the question of what iodine is made of, the answer will be simple - from waste.

It was found that during the production or sodium) in the remains up to 4 g of iodate and sodium iodide for every 1 kg of brine (this is 0.4%). The method has been used for more than 200 years all over the world, its main advantage is its cheapness.

Obtaining iodine from brines

Another answer to the question of what iodine is made of will be the extraction of the mineral from natural inorganic raw materials - natural brines.

The fact is that when drilling oil wells in the associated waters, a significant amount of iodine was found, sometimes more than 100 micrograms per 1 liter, but mostly not more than 40. Potylitsyn A.L. (Russian chemist) discovered this feature of deep waters in 1882, however, extracting the mineral from brines was expensive and uneconomical.

Industrial extraction began only in Soviet times after the coal method of iodine accumulation was invented (1930). Coal is able to accumulate up to 40 g of iodine per 1 kg per month. Now it is one of the main methods of raw crystal mining in Russia.

Ionite mining

This technique is very widely used in Japan. The method is new and has been widely used only in recent decades. Here, high-molecular ion-exchange resins are used to extract the raw material.

However, in Russia it is not used, since it does not make it possible to extract all the iodine from the raw materials and leaves a significant amount of it in the waste.

Innovative methods of V. Ganyaeva

Recently, Professor V. Ganyaev developed a unique technology for extracting iodine from mineral water. In the summer of 2016, a special installation was created, and today it is being successfully tested.

According to scientists, the new technology is not only environmentally cleaner, but also more economically advantageous; chloride compounds and sulfuric acid brines are not used here. When using it, the amount of extracted raw mineral will be 24 g per 1 liter of concentrate.

So to the question of what iodine is made of, you can also answer that in Russia - from mineral water. Although scientists believe that this technology will make it possible to use brines associated with oil production much more efficiently.

How is medical iodine produced?

Today, a well-known antiseptic, alcoholic 5% iodine, is being used less and less. It was replaced by drugs where iodine is used in conjunction with starch.

If we consider the question of whether there is a difference in the production of technical and medical iodine, then we should pay attention to the following.

1. In the production of raw material on an industrial scale, it is produced in the form of a crystalline mineral with a certain content of pure iodine (according to the periodic table).
2. Medical iodine becomes such after the combination of raw crystals with other substances: water, alcohols, ethers.

Hence the conclusion: initially, iodine crystals are not divided into medical and technical ones - they receive this status in the process of further processing.

The price of iodine preparations in pharmacies does not depend on the main component, but on those additional components that will be included in the medicine. In the well-known antiseptic vial, there is only iodine and ethyl alcohol, while, for example, drugs for the treatment of hyperthyroidism will be 2 orders of magnitude more expensive. They contain many other components.

Medical 5% iodine solution

Iodine is a very popular remedy for disinfecting various skin injuries (abrasions, scratches, cuts, etc.). Another common use of it is iodine mesh, I'm sure many have experienced this themselves in childhood. Do you know what iodine is made of? Why are some of its solutions brown and others purple?

Iodine under normal conditions is black-gray crystals with a purple metallic sheen. In medicine, we most often use a 5% solution of iodine in alcohol.

An alcoholic solution of iodine is brown, a solution of iodine in non-polar organic solvents is purple, and iodine vapor is also purple.

How iodine is obtained

Iodine is extremely rare in nature as a mineral, most often it is found in the form of iodides in sea water, in living organisms. Reserves of natural iodides are estimated at 15 million tons, 99% of the reserves are in Chile and Japan.

There are several ways to get iodine:

The raw material for the industrial production of iodine in Russia is oil drilling water, while in foreign countries that do not have oil deposits, seaweed is used, as well as mother solutions of Chilean (sodium) nitrate, lye from potash and saltpeter industries, which greatly increases the cost of producing iodine from such raw materials.

The use of iodine

One of the most important uses of iodine is in medicine. A 5% alcohol solution of iodine is used to disinfect the skin around various wounds.

With a large number of intramuscular injections, an iodine mesh is made in their place for the patient. This is necessary in order to quickly dissolve the "bumps" formed at the sites of intramuscular injections.

An example of an iodine grid

In x-ray and tomographic studies, iodine-containing contrast agents are widely used.

With iodine deficiency in the body, its 5% alcohol solution is not used orally!

In forensics, iodine vapor is used to detect fingerprints on paper surfaces, such as banknotes.

Iodine is used as a component of the positive electrode (oxidizing agent) in lithium-iodine batteries for automobiles.

Halogen lamps use iodine as a component of the bulb gas filler to deposit the evaporated filament tungsten back onto the bulb.
The danger of iodine

Iodine is poisonous! The lethal dose of iodine is 3 g. It causes damage to the kidneys and the cardiovascular system.

When iodine vapor is inhaled, a headache, cough, runny nose, and there may be pulmonary edema appear.

When it comes into contact with the mucous membrane of the eyes, lacrimation, eye pain and redness appear.

When ingested, general weakness, headache, fever, vomiting, diarrhea, brown coating on the tongue, pain in the heart and increased heart rate appear. A day later, blood appears in the urine. After 2 days, renal failure and myocarditis appear. Without treatment, death occurs.

Initially, iodine crystals are not divided into medical and technical ones - they receive this status in the process of further processing.

iodine(lat. Iodum), I, a chemical element of the VII group of the periodic system of Mendeleev, refers to halogens (the obsolete name Iodine and the symbol J are also found in the literature); atomic number 53, atomic mass 126.9045; crystals of black-gray color with a metallic luster. Natural iodine consists of one stable isotope with a mass number of 127. Iodine was discovered in 1811 by the French chemist B. Courtois. Heating the mother brine of seaweed ash with concentrated sulfuric acid, he observed the release of a violet vapor (hence the name Iodine - from the Greek. iodes, ioeides - similar in color to violet, purple), which condensed in the form of dark shiny lamellar crystals. In 1813-1814, the French chemist J. L. Gay-Lussac and the English chemist G. Davy proved the elemental nature of Iodine.

Distribution of iodine in nature. The average content of iodine in the earth's crust is 4·10 -5% by weight. In the mantle and magmas and in the rocks formed from them (granites, basalts, and others), iodine compounds are scattered; the deep minerals of Iodine are unknown. The history of Iodine in the earth's crust is closely connected with living matter and biogenic migration. In the biosphere, processes of its concentration are observed, especially by marine organisms (algae, sponges, and others). Eight hypergene minerals of iodine are known to form in the biosphere, but they are very rare. The main reservoir of iodine for the biosphere is the World Ocean (1 liter contains on average 5·10 -5 g of iodine). From the ocean, iodine compounds, dissolved in drops of sea water, enter the atmosphere and are carried by winds to the continents. (Locations remote from the ocean or fenced off from sea winds by mountains are depleted in iodine) Iodine is easily adsorbed by organic matter in soils and sea silts. With the compaction of these silts and the formation of sedimentary rocks, desorption occurs, part of the iodine compounds pass into groundwater. This is how iodine-bromine waters used for the extraction of iodine are formed, which are especially characteristic of areas of oil deposits (in some places 1 liter of these waters contains over 100 mg of iodine).

Physical properties of iodine. The density of Iodine is 4.94 g/cm 3 , t pl 113.5°C, bp t 184.35°C. The molecule of liquid and gaseous iodine consists of two atoms (I 2). A noticeable dissociation of I 2 = 2I is observed above 700 °C, as well as under the action of light. Already at ordinary temperatures, iodine evaporates, forming a sharp-smelling purple vapor. With weak heating, iodine sublimates, settling in the form of shiny thin plates; this process serves to purify iodine in laboratories and in industry. Iodine is poorly soluble in water (0.33 g / l at 25 ° C), well - in carbon disulfide and organic solvents (benzene, alcohol and others), as well as in aqueous solutions of iodides.

Chemical properties of iodine. The configuration of the outer electrons of the Iodine atom is 5s 2 5p 5 . In accordance with this, Iodine exhibits variable valency (oxidation state) in compounds: -1 (in HI, KI), +1 (in HIO, KIO), +3 (in ICl 3), +5 (in HIO 3, KIO 3 ) and +7 (in HIO 4 , KIO 4). Chemically, iodine is quite active, although to a lesser extent than chlorine and bromine. With metals, iodine interacts vigorously with light heating, forming iodides (Hg + I 2 = HgI 2). Iodine reacts with hydrogen only when heated and not completely, forming hydrogen iodide. Iodine does not combine directly with carbon, nitrogen, and oxygen. Elemental iodine is an oxidizing agent less powerful than chlorine and bromine. Hydrogen sulfide H 2 S, sodium thiosulfate Na 2 S 2 O 3 and other reducing agents reduce it to I - (I 2 + H 2 S \u003d S + 2HI). Chlorine and other strong oxidizing agents in aqueous solutions convert it to IO 3 - (5Cl 2 + I 2 + 6H 2 O \u003d 2HIO 3 H + 10HCl). When dissolved in water, iodine partially reacts with it (I 2 + H 2 O = HI + HIO); in hot aqueous solutions of alkalis, iodide and iodate are formed (3I 2 + 6NaOH = 5NaI + NaIO 3 + 3H 2 O). Adsorbed on starch, iodine turns it dark blue; it is used in iodometry and qualitative analysis for the detection of iodine.

Vapors of iodine are poisonous and irritate mucous membranes. Iodine has a cauterizing and disinfecting effect on the skin. Spots from Iodine are washed off with solutions of soda or sodium thiosulfate.

Getting Iodine. The raw material for the industrial production of iodine is oil drilling water; seaweed, as well as mother solutions of Chilean (sodium) nitrate, containing up to 0.4% iodine in the form of sodium iodate. To extract iodine from oil waters (usually containing 20-40 mg / l iodine in the form of iodides), they are first treated with chlorine (2 NaI + Cl 2 = 2NaCl + I 2) or nitrous acid (2NaI + 2NaNO 2 + 2H 2 SO 4 \u003d 2Na 2 SO 4 + 2NO + I 2 + 2H 2 O). The liberated iodine is either adsorbed by active carbon or blown out with air. Iodine adsorbed by coal is treated with caustic alkali or sodium sulfite (I 2 + Na 2 SO 3 + H 2 O = Na 2 SO 4 + 2HI). Free iodine is isolated from the reaction products by the action of chlorine or sulfuric acid and an oxidizing agent, for example, potassium dichromate (K 2 Cr 2 O 7 + 7H 2 SO 4 + 6NaI \u003d K 2 SO 4 + 3Na 2 SO 4 + Cr 2 (SO 4) S + 3I 2). When blown out with air, Iodine is absorbed with a mixture of sulfur oxide (IV) with water vapor (2H 2 O + SO 2 + I 2 = H 2 SO 4 + 2HI) and then Iodine is displaced by chlorine (2HI + Cl 2 = 2HCl + I 2). Crude crystalline iodine is purified by sublimation.

The use of iodine. Iodine and its compounds are mainly used in medicine and analytical chemistry, as well as in organic synthesis and photography.

Iodine in the body. Iodine is an essential trace element for animals and humans. In soils and plants of the taiga-forest non-chernozem, dry steppe, desert and mountain biogeochemical zones, iodine is contained in insufficient quantities or is not balanced with some other microelements (Co, Mn, Cu); this is associated with the spread of endemic goiter in these areas. The average content of iodine in soils is about 3·10 -4%, in plants about 2·10 -5%. There is little iodine in surface drinking waters (from 10 -7 to 10 -9%). In coastal areas, the amount of iodine in 1 m 3 of air can reach 50 micrograms, in continental and mountainous areas it is 1 or even 0.2 micrograms.

The absorption of iodine by plants depends on the content of its compounds in soils and on the type of plants. Some organisms (the so-called iodine concentrators), for example, algae - fucus, kelp, phyllophora, accumulate up to 1% iodine, some sponges - up to 8.5% (in the skeletal substance of spongin). Algae that concentrate iodine are used for its industrial production. Iodine enters the animal body with food, water, air. The main source of iodine is plant foods and feed. Absorption of iodine occurs in the anterior sections of the small intestine. The human body accumulates from 20 to 50 mg of iodine, including about 10-25 mg in the muscles, and 6-15 mg in the thyroid gland. Using radioactive iodine (131 I and 125 I), it was shown that in the thyroid gland, iodine accumulates in the mitochondria of epithelial cells and is part of the diiodine and monoiodothyrosines formed in them, which are condensed into the hormone tetraiodothyronine (thyroxine). Iodine is excreted from the body mainly through the kidneys (up to 70-80%), mammary, salivary and sweat glands, partly with bile.

In various biogeochemical provinces, the content of iodine in the daily ration varies (from 20 to 240 micrograms for humans, from 20 to 400 micrograms for sheep). An animal's need for iodine depends on its physiological state, season, temperature, adaptation of the organism to the content of iodine in the environment. The daily requirement for iodine in humans and animals is about 3 μg per 1 kg of body weight (increases during pregnancy, increased growth, cooling). The introduction of iodine into the body increases the basic metabolism, enhances oxidative processes, tones the muscles, stimulates sexual function.

In connection with a greater or lesser deficiency of iodine in food and water, iodized table salt is used, which usually contains 10-25 g of potassium iodide per 1 ton of salt. Application of fertilizers containing iodine can double and triple its content in crops.

Iodine in medicine. Preparations containing iodine have antibacterial and antifungal properties, they also have an anti-inflammatory and distracting effect; they are used externally for the disinfection of wounds, preparation of the surgical field. When taken orally, iodine preparations affect the metabolism, enhance the function of the thyroid gland. Small doses of iodine (microiodine) inhibit the function of the thyroid gland, acting on the formation of thyroid-stimulating hormone in the anterior lobes of the pituitary gland. Since iodine affects protein and fat (lipid) metabolism, it has found application in the treatment of atherosclerosis, as it lowers blood cholesterol; also increases the fibrinolytic activity of the blood. For diagnostic purposes, radiopaque substances containing iodine are used.

With prolonged use of iodine preparations and with increased sensitivity to them, iodism may occur - runny nose, urticaria, Quincke's edema, salivation and lacrimation, acne (iododerma), etc. Iodine preparations should not be taken with pulmonary tuberculosis, pregnancy, kidney diseases, chronic pyoderma, hemorrhagic diathesis, urticaria.

Iodine is radioactive. Artificially radioactive isotopes of iodine - 125 I, 131 I, 132 I and others are widely used in biology and especially in medicine to determine the functional state of the thyroid gland and treat a number of its diseases. The use of radioactive iodine in diagnostics is associated with the ability of iodine to selectively accumulate in the thyroid gland; use for medicinal purposes is based on the ability of β-radiation of iodine radioisotopes to destroy the secretory cells of the gland. When the environment is contaminated with nuclear fission products, radioactive isotopes of iodine are quickly included in the biological cycle, eventually getting into milk and, consequently, into the human body. Especially dangerous is their penetration into the body of children, whose thyroid gland is 10 times smaller than that of adults, and also has greater radiosensitivity. In order to reduce the deposition of radioactive isotopes of iodine in the thyroid gland, it is recommended to use stable iodine preparations (100-200 mg per dose). Radioactive iodine is rapidly and completely absorbed in the gastrointestinal tract and deposited selectively in the thyroid gland. Its absorption depends on the functional state of the gland. Relatively high concentrations of iodine radioisotopes are also found in the salivary and mammary glands and in the mucosa of the gastrointestinal tract. Radioactive iodine not absorbed by the thyroid gland is almost completely and relatively quickly excreted in the urine.