Swell sentence parsing. Parsing a Simple Sentence
IOD, iodine (Latin Iodum), I, chemical element VII group of short form (17th group of long form) periodic system, refers to halogens; atomic number 53, atomic mass 126.90447. One stable isotope 127 I occurs in nature. Radioactive isotopes with mass numbers of 108-144 are artificially obtained.
Historical reference. Iodine was first isolated in 1811 by the French chemist B. Courtois, acting with concentrated H 2 SO 4 on the ash of seaweed. The Latin name for the element comes from the Greek ιώδης - purple and is associated with the color of iodine vapor.
Distribution in nature. Iodine content in earth crust is 4 · 10 -5% by weight. In nature, iodine is mainly found in seawater and seaweed, as well as in oil drilling waters; is a part of minerals - natural iodides and iodates, for example, Ca (IO 3) 2 lautarite.
Properties... The configuration of the outer electron shell of the iodine atom is 5s 2 5p 5. In compounds, iodine exhibits oxidation states -1, +1, +3, +5, +7; Pauling electronegativity 2.66; atomic radius 140 pm; the radius of the ions I is 206 pm, I 5+ 109 pm. In gaseous, liquid and solid states, iodine exists in the form of diatomic molecules I 2. A noticeable dissociation (about 3%) of I 2 molecules into atoms begins at temperatures above 800 ° C, as well as under the influence of light. I 2 molecules are diamagnetic.
Iodine is a black crystalline substance with a violet metallic luster; the crystal lattice is rhombic; melting point 113.7 ° C, boiling point 184.3 ° C, density of solid iodine 4940 kg / m 3. Iodine is poorly soluble in water (0.33 g / dm 3 at 25 ° C); the solubility of iodine in water increases with increasing temperature, as well as with the addition of potassium iodide KI due to the formation of the complex KI 3. Iodine is readily soluble in many organic solvents (benzene, hexane, alcohols, carbon tetrachloride, etc.). Solid iodine readily sublimes with the formation of violet vapors with a pungent specific odor.
Iodine is the least reactive halogen. Iodine does not directly interact with noble gases, oxygen, sulfur, nitrogen, carbon. When heated, iodine reacts with metals (metal iodides are formed, for example aluminum iodide AlI 3), phosphorus (phosphorus iodide ΡΙ 3), hydrogen (hydrogen iodide HI), and other halogens (interhalogen compounds). Iodine is a less powerful oxidizing agent than chlorine and bromine. Reducing properties are more characteristic of iodine. So, chlorine oxidizes iodine to iodic acid HIO 3: I 2 + 5Сl 2 + 6H 2 O \u003d \u003d 2НIO 3 + 10HCl.
For iodine, a number of oxygen-containing acids are known, corresponding to various oxidation states of iodine: iodic HIO (oxidation state of iodine +1; salts - hypoiodites, for example potassium hypoiodite KIO), iodic HIO 3 (+5; iodates, for example potassium iodate KIO 3), periodic, or metaiodate, HIO 4 and orthoperiodic, or orthoiodic, H 5 IO 6 (+7; salts are metaperiodates, for example potassium metaperiodate KIO 4; orthoperiodates, for example potassium dihydro-orthoperiodate Κ 3 Η 2 ΙO 6; general name for acid salts containing iodine in oxidation state +7, - periodates). Oxygen-containing acids and their salts have oxidizing properties. HIO, weak acid; HIO and hypoioditis exist only in aqueous solutions. HIO solutions are prepared by the interaction of iodine with water, hypoiodite solutions - by the interaction of iodine with alkali solutions. HIO 3 is a colorless crystalline substance with a melting point of 110 ° C, readily soluble in water; when heated to 300 ° C, it splits off water with the formation of acidic oxide I 2 O 5. HIO 3 is obtained by oxidation of iodine with fuming nitric acid: 3I 2 + 10HNO 3 \u003d 6HIO 3 + 10NO + 2H 2 O. Iodates are water-soluble crystalline substances; obtained by the interaction of iodine with hot alkali solutions. When heated above 400 ° C, iodates decompose, for example: 4KIO 3 \u003d KI + 3KIO 4. H 5 IO 6 - colorless crystalline substance, mp 128 ° C. Heating H 5 IO 6 to 100 ° C in vacuum leads to the formation of HIO 4 (Η 5 ΙO 6 \u003d HIO 4 + 2H 2 O), which at more high temperature decomposes: 2HIO 4 \u003d 2HIO 3 + O 2. In aqueous solutions H 5 IO 6 exhibits the properties of a weak polybasic acid. Get H 5 IO 6 exchange reaction, for example Ba 3 (H 2 IO 6) 2 + 3H 2 SO 4 \u003d 2H 5 IO 6 + 3BaSO 4, followed by evaporation of the filtrate. Periods - crystalline substances, resistant to heat, soluble in water; are obtained by electrochemical oxidation of iodates.
Dissolution of iodine in water is a complex chemical process that includes not only dissolution, but also disproportionation (I 2 + H 2 O \u003d HI + HIO) and decomposition of HIO (3HIO \u003d 2HI + HIO 3). The disproportionation rate of HIO is high, especially in alkaline ones (3I 2 + 6NaOH \u003d NaIO 3 + 5NaI + 3H 2 O). Since the equilibrium constant of the reaction I 2 + H 2 O \u003d HI + HIO is small (K \u003d 2 ∙ 10 - 13), iodine is present in an aqueous solution in the form of I 2, and iodine water does not decompose when stored in the dark and has a neutral reaction.
Biological role. Iodine is a trace element. The daily human need for iodine is about 0.2 mg. The main physiological significance of iodine is determined by its participation in the function of the thyroid gland. The iodine entering it participates in the biosynthesis of thyroid hormones. A lack of iodine intake leads to the development of endemic goiter, an excess of iodine in the body is noted in some liver diseases.
Receiving... In industry, iodine is isolated from drilling waters and seaweed ash. To extract iodine, drilling waters containing iodides are treated with acidification with chlorine; the released iodine is blown out with water vapor. To purify iodine, sulfur dioxide SO 2 (I 2 + SO 2 + 2H 2 O \u003d 2HI + H 2 SO 4) is passed through the reaction mixture and the resulting HI is oxidized to I 2 (for example, with chlorine: 2HI + Cl 2 \u003d 2HCl + I 2 ). Iodates formed during the combustion of algae are reduced with sulfur dioxide (2NaIO 3 + 5SO 2 + 4H 2 O \u003d 2NaHSO 4 + 3H 2 SO 4 + I 2); the released iodine is purified by sublimation. In the laboratory, iodine is obtained by oxidation of iodides in an acidic medium (for example, using manganese dioxide: 2KI + MnO 2 + 2H 2 SO 4 \u003d I 2 + MnSO 4 + 2H 2 O + K 2 SO 4); the iodine formed is extracted or separated by steam distillation.
World iodine production 15-16 thousand tons / year (2004).
Application... Iodine and its compounds are used in medicine; iodine preparations capable of releasing elemental iodine have antibacterial, antifungal and anti-inflammatory properties. Iodine is used in transport chemical reactions to obtain high-purity Ti, Zr and other metals, as well as silicon; for filling iodine incandescent lamps, which are characterized by high luminous efficacy, small size and long service life. Radioactive isotopes 125 I (T 1/2 59.4 days), 131 I (T 1/2 8.04 days), 132 Ι (T 1/2 2.28 h) are used in biology and medicine to determine the functional state of the thyroid gland and treatment of its diseases.
Iodine is toxic, its vapors irritate mucous membranes and cause dermatitis.
Lit .: Greenwood N.N., Earnshaw A. Chemistry of the elements. 2nd ed. Oxf .; Boston, 1997; Drozdov A.A., Mazo G.N., Zlomanov V.P., Spiridonov F.M. Inorganic chemistry. M., 2004.Vol. 2.
Iodine is a well-known chemical element. But most people are only familiar with its alcoholic solution, which is used in medicine. Recently, they also often talk about its lack in the body in case of thyroid disease. Few are aware of physical and chemical properties iodine. And this is a rather peculiar element that is widespread in nature and is important for human life.
Even in everyday life, you can use the chemical properties of iodine, for example, to determine the presence of starch in foods. In addition, many popular methods of using this trace element for the treatment of many diseases have been advertised recently. Therefore, everyone needs to know what properties he has.
General characteristics of iodine
It is a fairly active nonmetal trace element. In the periodic table, it is in the group of halogens, along with chlorine, bromine and fluorine. Iodine is designated by the symbol I and has a serial number 53. This trace element received its name in the 19th century because of the purple color of the vapor. After all, in Greek iodine is translated as "violet, purple."
This is how iodine was discovered. Chemist Bernard Courtois, who works in a plant for the production of saltpeter, discovered this substance by accident. The cat turned the test tube with sulfuric acid, and it got on the ash of algae, from which saltpeter was then obtained. At the same time, a purple gas was released. This interested Bernard Courtois, and he began to study a new element. So at the beginning of the 19th century it became known about iodine. In the middle of the 20th century, chemists began to call this element "iodine", although the old designation is still more common.
Chemical properties of iodine
Equations showing activity chemical reactions of this item don't say anything an ordinary person... Only those who understand chemistry understand that they are used to describe its chemical properties. It is the most active element of all non-metals. Iodine can react with many other substances to form acids, liquid and volatile compounds. Although among halogens, it is the least active.
Briefly, the chemical properties of iodine can be considered on the example of its reactions. Iodine reacts with different metals even with slight heating, and iodides are formed. The best known are potassium and sodium iodides. It reacts with hydrogen only partially, and does not combine with some other elements at all. It is incompatible with nitrogen, oxygen, ammonia or essential oils. But the most famous chemical property of iodine is its reaction with starch. When added to substances containing starch, they turn blue.
Physical properties
Of all trace minerals, iodine is considered the most controversial. Most people are unaware of its features. The physical and chemical properties of iodine are briefly studied in school. Basically, this element is distributed in the form of an isotope with a mass of 127. It is the heaviest of all halogens. There is also radioactive iodine 125, which is produced by the decay of uranium. In medicine, artificial isotopes of this element with a mass of 131 and 133 are often used.
Of all halogens, iodine is the only one that is natural state solid. It can be represented by dark purple or black crystals or plates with a metallic sheen. They have a faint characteristic odor, conduct electricity well and are a bit like graphite. In this state, this trace element is poorly soluble in water, but very easily turns into a gaseous state. It can turn into purple vapor even at room temperature. These physicochemical properties of iodine are used to obtain it. Heating a microelement under pressure and then cooling it is purified from impurities. Dissolve iodine in alcohol, glycerin, benzene, chloroform or carbon disulfide, obtaining brown or purple liquids.
Sources of iodine
Despite the importance of this trace element for the life of many organisms, iodine is quite difficult to detect. In the earth's crust, it contains less than the rarest elements. But it is still believed that iodine is widespread in nature, since it is present in small quantities almost everywhere. It is mainly concentrated in sea water, algae, soil, and some plant and animal organisms.
The chemical properties of iodine explain the fact that it does not occur in pure form, only in the form of compounds. Most often it is extracted from seaweed ash or from sodium nitrate production waste. So iodine is mined in Chile and Japan, which are leaders in the extraction of this element. In addition, it can be obtained from the waters of some salt lakes or oil waters.
Iodine enters the human body from food. It is present in soils and plants. But in our country, soils poor in iodine are common. Therefore, iodine-containing fertilizers are most often used. For the prevention of diseases associated with a lack of iodine, the element is added to salt and some common foods.
Its role in the life of the body
Iodine is one of those trace elements that are involved in many biological processes. It is present in small amounts in many plants. But in living organisms, it is very important. Iodine is used in the production of thyroid hormones in the thyroid gland. They regulate the body's vital processes. With a lack of iodine in a person, the thyroid gland increases, various pathologies arise. They are characterized by decreased performance, weakness, headaches, decreased memory and mood.
Application in medicine
The most common 5% alcohol solution of iodine. It is used to disinfect the skin around lesions. But this is a rather aggressive antiseptic, therefore, lately, milder solutions of iodine with starch have been used, for example, Betadin, Yoks or Iodinol. The warming properties of iodine are often used to eliminate muscle pain or joint pathologies, and an iodine grid is made after injections.
Industrial applications
This trace element is also of great importance in industry. The special chemical properties of iodine make it possible to use it in various industries. For example, in forensic science, it is used to detect fingerprints on paper surfaces. Iodine is widely used as a light source in halogen lamps. It is used in photography, film industry, and metal processing. And recently, this microelement began to be used in liquid crystal displays, when creating glasses with dimming, as well as in the field of laser thermonuclear fusion.
Danger to humans
Despite the importance of iodine in vital processes, in large quantities it is toxic to humans. Only 3 g of this substance leads to serious damage to the kidneys and the cardiovascular system. At first, a person feels weakness, a headache, he has diarrhea, his heart rate increases. If you inhale iodine vapors, irritation of the mucous membranes, eye burns, and pulmonary edema occurs. If left untreated, iodine poisoning is fatal.
Iodine or iodine is familiar to everyone. Having cut our finger, we reach for a bottle of iodine, more precisely, with its alcohol solution ...
Nevertheless, this element is highly unique and each of us, regardless of education and profession, has to rediscover it for ourselves more than once. The history of this element is also peculiar.
First acquaintance with iodine
Iodine was discovered in 1811 by the French chemist-technologist Bernard Courtois (1777-1838), the son of the famous saltpeter. During the years of the French Revolution, he had already helped his father "to extract from the bowels of the earth the main element of the weapon for the defeat of tyrants", and later took up saltpeter on his own.
At that time, saltpeter was obtained in the so-called saltpeter, or piles. These were heaps of plant and animal waste mixed with construction waste, limestone, marl. The ammonia formed during rotting was oxidized by microorganisms first to nitrous HN02, and then to nitric HNO 3 acid, which reacted with calcium carbonate, converting it into nitrate Ca (N0 3) 2. It was removed from the mixture with hot water, and then potash was added. There was a reaction of Ca (N0 3) a + K 2 CO 3 → 2KN0 3 + CaCO ↓.
The potassium nitrate solution was decanted from the precipitate and evaporated. The obtained crystals of potassium nitrate were purified by additional recrystallization.
Courtois was not a simple artisan. After working for three years in a pharmacy, he received permission to listen to lectures in chemistry and study in the laboratory of the Ecole Polytechnique in Paris at the famous Furcroix. He applied his knowledge to the study of seaweed ash, from which soda was then extracted. Courtois noticed that the copper boiler, in which the ash solutions were evaporated, collapsed too quickly. In the mother liquor, after evaporation and precipitation of crystalline sodium and potassium sulfates, their sulfides and, apparently, something else remained. By adding concentrated sulfuric acid to the solution, Courtois discovered the evolution of violet vapors. It is possible that something similar was observed by colleagues and contemporaries of Courtois, but it was he who was the first to move from observations to research, from research to conclusions.
These are the conclusions (citing an article written by Courtois): “The mother liquor solution obtained from algae contains a fairly large amount of an unusual and curious substance. It is easy to distinguish it. To do this, it is enough to add sulfuric acid to the mother liquor and heat it in a retort connected to a receiver. The new substance ... precipitates as a black powder that turns into a gorgeous purple vapor when heated. These vapors condense in the form of lustrous crystalline plates having a luster similar to the luster of crystalline lead sulfide ... The amazing color of the vapors of the new substance allows it to be distinguished from all hitherto known substances, and it has other remarkable properties, which gives its discovery the greatest interest. " ...
In 1813, the first scientific publication about this substance appeared; chemists from different countries began to study it, including such luminaries of science as Joseph Gay-Lussac and Humphrey Davy. A year later, these scientists established the elementary nature of the substance discovered by Courtois, and Gay-Lussac called the new element iodine - from the Greek - dark blue, purple.
Second acquaintance: properties are common and unusual.
Iodine is a chemical element of group VIIthe periodic system. Atomic number - 53. Atomic mass - 126.9044. Halogen. Of the naturally occurring halogens, it is the heaviest, unless, of course, you count the radioactive short-lived astatine. Almost all natural iodine consists of atoms of a single isotope with a mass number of 127. Radioactive iodine - 125 is formed as a result of spontaneous fission of uranium. Of the artificial isotopes of iodine, the most important are iodine - 131 and iodine - 133; they are used in medicine. 
The elemental iodine molecule, like other halogens, consists of two atoms. Iodine, the only halogen species, is solid under normal conditions. Beautiful dark blue crystals of iodine are most similar to graphite. Distinct crystalline structure, the ability to conduct electric current - all these "metallic" properties are characteristic of pure iodine.
But, unlike graphite and most metals, iodine very easily turns into a gaseous state. It is even easier to convert iodine to vapor than to liquid.
To melt iodine, a fairly low temperature is needed: + 113.5 ° C, but, in addition, it is necessary that the partial pressure of iodine vapor over the melting crystals is at least one atmosphere. In other words, iodine can be melted in a narrow-necked flask, but not in an open laboratory dish. In this case, iodine vapors do not accumulate, and when heated, iodine will sublime - it will pass into a gaseous state, bypassing a liquid one, which usually happens when this substance is heated. By the way, the boiling point of iodine is not much higher than the melting point, it is only 184.35 ° C.
But not only by the simplicity of conversion to a gaseous state iodine is released among other elements... For example, its interaction with water is very peculiar.
Elemental iodine does not dissolve in water very well: at 25 ° C only 0.3395 g / l. Nevertheless, you can get a much more concentrated aqueous solution of element No. 53 using the same simple trick that doctors use when they need to keep iodine tincture longer (3 or 5% solution of iodine in alcohol): so that iodine tincture does not fizzle out , a little potassium iodide KI is added to it. This same substance helps to obtain iodine-rich aqueous solutions: iodine is mixed with a not too dilute solution of iodine ralium.
KI molecules are capable of attaching elemental iodine molecules. If one molecule enters into the reaction on each side, a red-brown potassium triiodide is formed. Potassium iodide can also attach a larger number of iodine molecules, as a result, compounds of various compositions are obtained up to K19. These substances are called polyiodides. Polyiodides are unstable, and their solution always contains elementary iodine, and in a much higher concentration than that which can be obtained by direct dissolution of iodine.
In many organic solvents - carbon disulfide, kerosene, alcohol, benzene, ether, chloroform - iodine dissolves easily. The color of non-aqueous solutions of iodine is not constant. For example, its solution in carbon disulfide is violet, and in alcohol it is brown. How can this be explained?
Obviously, purple solutions contain iodine in the form of 12 molecules. If a solution of a different color is obtained, it is logical to assume the existence of iodine compounds with a solvent in it. However, not all chemists share this view. Some of them believe that the differences in the color of iodine solutions are explained by the existence of various kinds of forces connecting the molecules of the solvent and the solute.
Violet iodine solutions conduct electricity, since in solution molecules 12 partially dissociate into 1+ and I- ions. This assumption does not contradict the ideas about the possible valencies of iodine. Its main valences are: 1 "(such compounds are called iodides), 5+ (iodates) and 7+ (periodates). But iodine compounds are also known, in which it exhibits valencies 1+ and 3+, playing the role of a monovalent or trivalent metal There is a compound of iodine with oxygen, in which element 53 is octavalent, - J4.
But most often iodine, as befits a halogen (there are seven electrons on the outer shell of an atom), exhibits a valence of 1 “. Like other halogens, it is quite active - it reacts directly with most metals (even noble silver is resistant to the action of iodine only at temperatures up to 50 ° C), but is inferior to chlorine and bromine, not to mention fluorine. Some elements - carbon, nitrogen, oxygen, sulfur, selenium - do not directly react with iodine.
third acquaintance:
It turns out that there is less iodine on Earth than lutetium
Iodine is a rather rare element. Its clarke (content in the earth's crust in weight percent) is only 4-10 ~ 5%. It is less than the most difficult to obtain elements of the lanthanide family - thulium and lutetium.
Iodine has one feature that makes it akin to "rare earths" - extreme absent-mindedness in nature. Not the most common element, iodine is present literally everywhere. Even in super-pure, seemingly, crystals of rock crystal, micro-impurities of iodine are found. In transparent calcites, the content of element No. 53 reaches 5-10 ~ 6%. Iodine is present in soil, in sea and river water, in plant cells and in animals. But minerals rich in iodine are very few. The most famous of them is Ca (IO 5) 2 lautarite. But there are no industrial deposits of lautarite on Earth.
To obtain iodine, it is necessary to concentrate natural solutions containing this element, for example, the water of salt lakes or associated oil waters, or to process natural iodine concentrators - seaweed. A ton of dried seaweed (kelp) contains up to 5 kg of iodine, while a ton of seawater contains only 20-30 mg.
Like most vital elements, iodine is circulating in nature. Since many iodine compounds are readily soluble in water, iodine is leached from igneous rocks and carried to seas and oceans. Seawater evaporates and raises masses of elemental iodine into the air. Precisely elementary: compounds of element No. 53 in the presence of carbon dioxide are easily oxidized by oxygen up to 12.
The winds that carry air masses from the ocean to the mainland also carry iodine, which, together with atmospheric precipitation, falls on the ground, gets into the soil, groundwater, and living organisms. The latter concentrate iodine, but, dying, return it to the soil, from where it is again washed out by natural waters, enters the ocean, evaporates, and everything starts anew. This is just a general scheme, in which all the particulars and chemical transformations are omitted, which are inevitable at different stages of this eternal rotation.
And the iodine cycle has been studied very well, and this is not surprising: the role of trace amounts of this element in the life of plants, animals, humans is too great ...
Iodine fourth acquaintance: biological functions of iodine
They are not limited to iodine tincture. We will not talk in detail about the role of iodine in plant life - it is one of the most important trace elements, we will limit ourselves to its role in human life.
Back in 1854, the Frenchman Chaten, an excellent chemical analyst, discovered that the prevalence of goiter is directly dependent on the iodine content in the air, soil, food consumed by people. Colleagues contested the findings of Chaten; moreover, the French Academy of Sciences recognized them as harmful. As for the origin of the disease, then it was believed that 42 reasons could cause it - the lack of iodine did not appear on this list.
Almost half a century passed before the authority of the German scientists Baumann and Oswald forced the French scientists to admit their mistake. The experiments of Baumann and Oswald showed that the thyroid gland contains an astonishing amount of iodine and produces iodine-containing hormones. Lack of iodine initially leads to only a slight increase in the thyroid gland, but as it progresses, this disease - endemic goiter - affects many body systems. As a result, metabolism is disturbed, growth slows down. In some cases, endemic goiter can lead to deafness, to cretinism ... This disease is more common in mountainous regions and in places far from the sea.
The widespread occurrence of the disease can be judged even by the works of painting. One of the best female portraits of Rubens "Straw Hat". The beautiful woman depicted in the portrait has a noticeable swelling of the neck (the doctor would immediately say: the thyroid gland is enlarged). Andromeda in Perseus and Andromeda has the same symptoms. Signs of iodine deficiency are also seen in some people depicted in portraits and paintings by Rembrandt, Durer, Van Dyck ...
In our country, most of whose regions are far from the sea, the fight against endemic goiter is carried out constantly - primarily by means of prevention. The simplest and most reliable remedy is the addition of microdoses of iodides to table salt.
It is interesting to note that the history of the therapeutic use of iodine goes back centuries. The healing properties of substances containing iodine were known 3 thousand years before this element was discovered. Chinese Code 1567 BC e. recommends seaweeds for the treatment of goiter ...
The antiseptic properties of iodine in surgery were first used by the French physician Bouapé. Oddly enough, the simplest dosage forms of iodine - aqueous and alcoholic solutions - did not find use in surgery for a very long time, although back in 1865-1866. the great Russian surgeon NI Pirogov used iodine tincture in the treatment of wounds.
The priority of preparation of the operating field with the help of iodine tincture is erroneously attributed to the German physician Grossich. Meanwhile, back in 1904, four years before Grossich, Russian military doctor N.P. Filonchikov, in his article "Aqueous solutions of iodine as an antiseptic liquid in surgery" drew the attention of surgeons to the enormous advantages of aqueous and alcoholic solutions of iodine precisely in preparation for the operation ...
Needless to say, these simple drugs have not lost their significance to this day. Interestingly, sometimes iodine tincture is prescribed as an internal one: a few drops per cup of milk. This can be beneficial in atherosclerosis, but it must be remembered that iodine is useful only in small doses, and in large doses it is toxic.
Iodine fifth acquaintance - purely utilitarian
Not only doctors are interested in iodine. Geologists and botanists, chemists and metallurgists need it.
Like other halogens, iodine forms numerous organoiodine compounds, which are included in the composition of some dyes.
Iodine compounds are used in photography and the film industry for the preparation of special photographic emulsions and photographic plates.
Iodine is used as a catalyst in the production of synthetic rubbers.
Obtaining ultrapure materials - silicon, titanium, hafnium, zirconium - is also not complete without this element. The iodide method for producing pure metals is used quite often.
iodine preparations are used as dry lubricants for rubbing surfaces made of steel and titanium.
Powerful iodine incandescent lamps are being manufactured. The glass bulb of such a lamp is filled not with an inert gas, but with the vapor of the hearth, which themselves emit light at high temperatures.
Iodine and its compounds are used in laboratory practice for analysis and in chemotronic devices, the action of which is based on the redox reactions of iodine ...
A lot of work of geologists, chemists and technologists is spent on the search for iodine raw materials and the development of methods for the extraction of iodine. Until the 60s of the last century, algae were the only source of inventive production of iodine. In 1868, iodine began to be obtained from wastes of saltpeter production, which contain iodate and sodium iodide. Free raw materials and an easy way to obtain iodine from saltpeter mother liquors ensured widespread use of Chilean iodine. The first world war the supply of Chilean nitrate and iodine ceased, and soon the lack of iodine began to affect the general state of the pharmaceutical industry in Europe. The search began for cost-effective methods of producing iodine. In our country, already during the years of Soviet power, iodine began to be obtained from the underground and oil waters of the Kuban, where it was discovered by the Russian chemist A. L. Potylitsin back in 1882. Later, similar waters were discovered in Turkmenistan and Azerbaijan.
But the content of iodine in groundwater and associated waters of oil production is very small. This was the main difficulty in creating economically viable industrial methods for producing iodine. It was necessary to find a "chemical bait" that would form a fairly strong compound with iodine and concentrate it. Initially, such a "bait" was starch, then copper and silver salts, which bound iodine into insoluble compounds. We tried kerosene - iodine dissolves well in it. But all these methods proved to be expensive and sometimes flammable.
In 1930, the Soviet engineer V.P. Denisovich developed the Coal method for extracting iodine from oil waters, and this method was for a long time the basis of Soviet iodine production. A kilogram of coal per month accumulated up to 40 g of iodine ...
Other methods have been tried. Already in recent decades, it was found that iodine is selectively sorbed by high molecular weight ion-exchange resins. In the iodine industry of the world, the ion exchange method is still used to a limited extent. There have been attempts to apply it in our country, but the low iodine content and insufficient selectivity of ion exchangers for iodine have not yet allowed this, of course, a promising method to radically transform the iodine industry.
Geotechnological methods of iodine extraction are also promising. They will make it possible to extract iodine from the associated waters of oil and gas fields without pumping these waters to the surface. Special reagents introduced through the well will concentrate the iodine underground, and not a weak solution will go to the surface, but a concentrate. Then, obviously, the production of iodine and its consumption by industry will sharply increase - the complex of properties inherent in this element is very attractive to it.
JOD AND MAN. The human body not only does not need large amounts of iodine, but with surprising constancy maintains a constant concentration (10 ~ 5-10 ~ 6%) of iodine in the blood, the so-called iodine mirror of blood. Of the total amount of iodine in the body, which is about 25 mg, more than half is in the thyroid gland. Almost all the iodine contained in this gland is a part of various derivatives of tyrosine - the thyroid hormone, and only a small part of it, about 1%, is in the form of inorganic iodine I1-.
Large doses of elemental iodine are dangerous: a dose of 2-3 g is lethal. At the same time, much larger doses are allowed in the form of iodide.
If a significant amount of inorganic iodine salts is introduced into the body with food, its concentration in the blood will increase 1000 times, but after 24 hours the iodine mirror of the blood will return to normal. The level of the iodine mirror strictly obeys the laws of internal exchange and practically does not depend on the experimental conditions.
In medical practice, organoiodine compounds are used for X-ray diagnostics. The rather heavy nuclei of iodine atoms scatter X-rays. With the introduction of such a diagnostic agent into the body, extremely clear X-ray images of individual areas of tissues and organs are obtained.
UNDER AND COSMIC RAYS. Academician V. I. Vernadsky believed that cosmic rays play an important role in the formation of iodine in the earth's crust, which cause nuclear reactions in the earth's crust, that is, the transformation of some elements into others. Due to these transformations, very small amounts of new atoms, including iodine atoms, can be formed in rocks.
IODE _ LUBRICANT. Only 0.6% iodine added to hydrocarbon oils greatly reduces the friction work in stainless steel and titanium bearings. This makes it possible to increase the load on the rubbing parts by more than 50 times.
IODINE AND GLASS. Iodine is used to make special polaroid glass. Crystals of iodine salts are introduced into glass (or plastic), which are distributed in a strictly regular way. The vibrations of the light beam cannot pass through them in all directions. It turns out a kind of filter, called a polaroid, which removes the oncoming blinding stream of light. This glass is used in cars. By combining several polaroids or by rotating polaroid glasses, extremely colorful effects can be achieved - a phenomenon used in cinema and theater.
DO YOU KNOW THAT:
- the iodine content in human blood depends on the season: from September to January, the concentration of iodine in the blood decreases, from February a new rise begins, and in May-June the iodine mirror reaches its highest level. These fluctuations have a relatively small amplitude, and their causes are still a mystery;
- eggs, milk, fish contain a lot of iodine from food products; there is a lot of iodine in seaweed, which is marketed in the form of canned food, dragees and other products;
- the first iodine plant in Russia was built in 1915 in Yekaterinoslav (now Dnepropetrovsk); received iodine from the ashes of the Black Sea algae phyllophora; during the years of the First World War, 200 kg of iodine were produced at this plant;
- if a storm cloud "Sow" with silver iodide or lead iodide, then instead of hail, a finely dispersed snow croup is formed in the cloud: the cloud sown with such salts is shed by rain and does not harm crops.
Iodine (Latin iodum), i, chemical element vii of the group of Mendeleev's periodic table, refers to halogens (in the literature there is also the symbol j); atomic number 53, atomic weight 126.9045; crystals of black-gray color with a metallic sheen. Natural I. consists of one stable isotope with a mass number of 127. I. 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 violet vapor (hence the name I. - from the Greek i o des, ioeid e s - similar in color to a violet, violet), 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 elementary nature of I.
Distribution in nature. The average content of I. 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), I. compounds are dispersed; deep-seated minerals are unknown. The history of I. in the earth's crust is closely related to living matter and biogenic migration. The processes of its concentration are observed in the biosphere, especially by marine organisms (algae, sponges, etc.). There are 8 known hypergene minerals of I., which are formed in the biosphere, but they are very rare. The main reservoir of I. for the biosphere is the World Ocean (in 1 l contains on average 5? 10 -5 r AND.). From the ocean, I. compounds, dissolved in drops of seawater, enter the atmosphere and are carried by winds to the continents. (Areas remote from the ocean or fenced off from sea winds by mountains are depleted in I.) I. is easily adsorbed organic matter soils and sea silts. When these silts are compacted and sedimentary rocks are formed, desorption occurs, and some of the mineral compounds pass into underground waters. This is how the iodine-bromine waters used for the extraction of I. are formed, which are especially characteristic of the regions of oil fields (in some places 1 l of these waters contains over 100 mg AND.).
Physical and chemical properties ... Density I. 4.94 r/ cm3 , tpl 113.5 ° C, tbale 184.35 ° C. The molecule of liquid and gaseous I. consists of two atoms (i 2). Noticeable dissociation
observed above 700 ° C, as well as under the action of light. Already at ordinary temperatures, I. evaporates, forming a sharp-smelling purple vapor. When heated weakly, I. sublimes, settling in the form of shiny thin plates; this process serves for cleaning I. in laboratories and in industry. I. poorly soluble in water (0.33 r/ l at 25 ° C), well - in carbon disulfide and organic solvents (benzene, alcohol, etc.), as well as in aqueous solutions of iodides.
External electron configuration atomI. 5 2 s 5 5 p. In accordance with this, I. manifests in compounds a variable valence (oxidation state): - 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, I. is quite active, although to a lesser extent than chlorine and bromine... Iodine interacts with metals vigorously upon gentle heating, forming iodides (hg + i 2 \u003d hgi 2). I. reacts with hydrogen only on heating and not completely, forming hydrogen iodide. I. does not combine directly with carbon, nitrogen, and oxygen. Elemental I. is an oxidizing agent that is 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 oxidants in aqueous solutions convert it to io 3 - (5cl 2 + i 2 + 6h 2 o \u003d 2hio 3 + 10hcl).
I. vapors are poisonous and irritate the mucous membranes. It has a cauterizing and disinfecting effect on I.'s skin. Stains from I. are washed off with solutions of soda or sodium thiosulfate.
Receiving and using. The raw material for industrial production of oil in the USSR is oil drilling water; abroad - seaweed, as well as mother liquors of Chilean (sodium) nitrate, containing up to 0.4% I. in the form of sodium iodate. For extraction of I. from oil waters (usually containing 20-40 mg/ l I. in the form of iodils), they are first acted upon by chlorine (2nai + cl 2 \u003d 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 released I. is either adsorbed with active carbon or blown out with air. I. adsorbed by coal are treated with caustic alkali or sodium sulfite (i 2 + na 2 so 3 + h 2 o \u003d na 2 so 4 + 2hi). From the reaction products, free I. is isolated 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) 3 + 3i 2). When blown out with air, I. is absorbed with a mixture of sulfur dioxide and water vapor (2h 2 o + so 2 + i 2 \u003d \u003d h 2 so 4 + 2hi) and then displaced I. with chlorine (2hi + cl 2 \u003d 2hcl + i 2). Raw crystalline I. is purified by sublimation.
I. and its compounds are used mainly in medicine and analytical chemistry, as well as in organic synthesis and photography. In industry, the use of I. is still insignificant in volume, but very promising. Thus, the production of high-purity metals is based on the thermal decomposition of iodides.
Lit .: Ksenzenko V.I., Stasinevich D.S., Technology of bromine and iodine, M., 1960; Pozin M.E., Technology of mineral salts, 3rd ed., L., 1970, ch. 8; Rolsten R.F., Iodide metals and metal iodides, trans. from English., M., 1968.
D. S. Stasinevich.
Iodine in the body. I. - necessary for animals and humans trace element... In the soils and plants of the taiga-forest nonchernozem, dry steppe, desert, and mountain biogeochemical zones, I. is found in insufficient quantities or is not balanced with certain other microelements (Co, mn, cu); associated with this is the spread of endemic goiter in these zones. The average I. content in soils is about 3? 10 -4%, in plants about 2? 10 -5%. In surface drinking waters, I. is small (from 10 -7 to 10 -9%). In the coastal regions, the number of I. in 1 m3 air can reach 50 mcg, in continental and mountainous - is 1 or even 0.2 mcg.
The absorption of I. by plants depends on the content of its compounds in the soil and on the type of plants. Some organisms (the so-called concentrators of I.), for example, seaweed - fucus, kelp, phyllophora, accumulate up to 1% I., some sponges - up to 8.5% (in the skeletal substance of spongin). Algae, which concentrate I., are used for its industrial production. I. enters the animal organism with food, water, and air. The main source of I. is vegetable products and feed. Absorption And. Occurs in the anterior sections of the small intestine. The human body accumulates from 20 to 50 mg I., including in muscles about 10-25 mg, in the thyroid gland is normal 6-15 mg... With the help of radioactive I. (131 i and 125 i), it was shown that in the thyroid gland I. accumulates in the mitochondria of epithelial cells and is part of the diiodo- and monoiodotyrosines formed in them, which are condensed into the hormone tetraiodothyronine ( thyroxine). I. is excreted from the body mainly through the kidneys (up to 70-80%), milk, salivary, and sweat glands, partly with bile.
In different biogeochemical provinces I. content in the daily diet varies (for a person from 20 to 240 mcg, for sheep from 20 to 400 mcg). An animal's need for I. depends on its physiological state, season, temperature, and adaptation of the organism to I.'s content in the environment. The daily I. need for humans and animals is about 3 mcgby 1 kg mass (increases during pregnancy, increased growth, cooling). Introduction into the body of I. increases the basal metabolism, enhances oxidative processes, tones up muscles, and stimulates sexual function.
Due to the greater or lesser lack of I. in food and water, iodination of table salt is used, which usually contains 10-25 r potassium iodide per 1 t salt. The use of fertilizers containing I. can double and triple its content in agricultural production. cultures.
Lit .: Gutbertson D.P., Trace elements, in the book: New in the physiology of domestic animals, trans. from English, vol. 1, M.-L., 1958; Turakulov Ya. Kh., Biochemistry and pathochemistry of the thyroid gland, Tash., 1963; Berzin T., Biochemistry of hormones, trans. from it., M., 1964; Rapoport S.M., Medical biochemistry, trans. from it., M., 1966.
V. V. Kovalsky.
Iodine in medicine. Preparations containing I. have antibacterial and antifungal properties; it also has an anti-inflammatory and distracting effect; they are used externally for disinfecting wounds, preparing the operating field. When taken internally, I. preparations have an effect on metabolism and enhance the function of the thyroid gland. Small doses of I. (microiodine) inhibit the function of the thyroid gland, acting on the formation of thyroid-stimulating hormone in the anterior pituitary gland. Since I. influences protein and fat (lipid) metabolism, it has found application in the treatment of atherosclerosis, since it lowers blood cholesterol; also increases the fibrinolytic activity of the blood.
For diagnostic purposes, radiopaque substances containing I.
With prolonged use of I. preparations and with increased sensitivity to them, iodism may appear - runny nose, urticaria, Quincke's edema, salivation and lacrimation, acne-like rash (iododerma), etc. I. preparations should not be taken for pulmonary tuberculosis, pregnancy, and kidney diseases , chronic pyoderma, hemorrhagic diathesis, urticaria.
Radioactive iodine. Artificially radioactive isotopes of I. - 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 to treat a number of its diseases. The use of radioactive I. in diagnostics is associated with I.'s ability to selectively accumulate in the thyroid gland; use for medicinal purposes is based on the ability of b-radiation of radioisotopes I. to destroy secretory cells of the gland. With contamination environment By the products of nuclear fission, radioactive isotopes of I. are quickly included in the biological cycle, eventually entering milk and, consequently, the human body. Particularly 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 I. in the thyroid gland, it is recommended to use preparations of stable I. (100-200 mg appointment). Radioactive I. is rapidly and completely absorbed in the gastrointestinal tract and is selectively deposited in the thyroid gland. Its absorption depends on the functional state of the gland. Relatively high concentrations of I. radioisotopes are also found in the salivary and mammary glands and in the mucous membrane of the gastrointestinal tract. Radioactive I. which is not absorbed by the thyroid gland is excreted almost completely and relatively quickly in the urine.
Iodine (I 2 ) is in the 7th group of the periodic table of D.I. Mendeleev in the subgroup of halogens. At the outer level, the iodine atom has 1 unpaired electron, one electron is missing until the end of the shell of the inert gas. Due to the large radius of the atom, iodine exhibits reducing properties, regardless of the fact that it is in the halogen subgroup. The outer electron is far from the nucleus, so it is easier to give it to iodine than to attach it to itself. Therefore, iodine acts as a reducing agent.
Physical properties of iodine.
Iodine represents crystals of brilliant gray-black color.
Chemical properties of iodine.
Iodine does not react with most non-metals, and reacts with metals only when heated and very slowly. For example, all other halogen react with iron to give the trivalent salt FeHal 3 , and iodine - only 2-valence:
Fe + I 2 = FeI 2,
With hydrogen, the reaction proceeds as follows:
H 2 + I 2 = 2 HI,
The reaction is reversible and endothermic.
Getting iodine.
Iodine is obtained in the laboratory by the reaction:
MnO 2 + 4HI \u003d MnI 2 + I 2 + 2H 2 O.
