Strontium- alkaline earth metal. It is a substance of a silvery-white color (see photo), very soft and plastic, easily cut even with an ordinary knife. Possesses high activity, burns in the presence of air, enters into chemical interactions with water. Under natural conditions, it is not found in its pure form. It is mainly found in the composition of fossil minerals, usually in combination with calcium.

It was first found in Scotland at the end of the 18th century in a village with the name Stronshian, which gave the name to the found mineral - strontianite. But only 30 years after the discovery, the English scientist H. Davy was able to isolate it in its pure form.

The element's compounds are used in metallurgical production, medicine, and the food industry. Very interesting is its property, when burning, to emit fires of a red hue, which were adopted by pyrotechnics at the beginning of the 20th century.

The action of strontium and its biological role

Many associate the action of a macroelement with high toxicity and radioactivity. But such an opinion is rather erroneous, because. the natural element practically does not possess these qualities and is even present in the tissues of biological organisms, performing an important biological role and some functions as a satellite of calcium. Due to the properties of the substance, it is used for medical purposes.

The main accumulation of strontium in the human body falls on bone tissue. This is due to the fact that the element is similar to calcium in chemical action, and calcium, in turn, is the main component of the "construction" of the skeleton. But the muscles contain only 1% of the total mass of the element in the body.

Also, strontium is present in the deposits of gall and urinary stones, again in the presence of calcium.

By the way, about the harmfulness of strontium - only radioactive isotopes have a devastating effect on health, which in their chemical properties practically do not differ from the natural element. Perhaps this is the reason for this confusion.

Daily rate

The daily norm of a macronutrient is approximately 1 mg. This amount is quite easily replenished with food and drinking water. In total, approximately 320 mg of strontium is distributed in the body.

But it should be borne in mind that our body is able to absorb only 10% of the incoming element, and we get up to 5 mg per day.

Strontium deficiency

The lack of a macronutrient can only theoretically cause some pathologies, but so far this has been shown only in animal experiments. So far, scientists have not identified the negative impact of strontium deficiency on the human body.

At the moment, only some dependences of the assimilation of this macronutrient under the influence of other substances in the body have been identified. For example, this process is facilitated by certain amino acids, the intake of vitamins D and lactose. And drugs based on barium or sodium sulfates, as well as products with a high content of dietary coarse fibers, have an opposite effect.

There is another unpleasant feature - when calcium deficiency occurs, the body begins to accumulate radioactive strontium even from the air (often polluted by industrial enterprises).

Why is strontium dangerous for humans and what is its harm?

Strontium, after all, is capable of exerting a harmful radioactive effect. The element itself does little harm, and a critical dose has not yet been established. But its isotopes can cause diseases and various disorders. Like natural strontium, it accumulates in the skeleton itself, but its action causes damage to the bone marrow and destruction of the very structure of the bones. It can affect the cells of the brain and liver, and thus cause the occurrence of neoplasms and tumors.

But one of the most terrible consequences of exposure to the isotope is radiation sickness. The consequences of the Chernobyl disaster are still being felt in our country, and the accumulated reserves of radioactive strontium make themselves felt in the soil, water and the atmosphere itself. You can also get a large dose by working at enterprises using the element - there is the highest level of diseases of bone sarcoma and leukemia.

But natural strontium can also cause unpleasant consequences. Due to a rather rare set of circumstances such as an inadequate diet, a lack of calcium, vitamin D, and an imbalance in the body of elements such as selenium and molybdenum, specific diseases develop - strontium rickets and uric disease. The latter got its name from the area where local residents suffered from them back in the 19th century. They became disabled due to the curvature of the structure of the skeleton, bones and joints. Moreover, for the most part, those people who grew up in these places from childhood suffered. Only in the 20th century did they find out that the waters of the local river contained an increased amount of the element. And during the period of growth, it is the musculoskeletal system that is most affected.

Contact with strontium oxide on the mucous membranes of the mouth or eyes can cause burns and deep damage. And inhaling it with air can contribute to the development of pathological diseases in the lungs - fibrosis, bronchitis, and heart failure is also possible.

As treatment, drugs based on calcium, magnesium, sodium sulfate or barium are usually used. It is also possible to use complexing agents that bind and remove radioactive toxins from cells.

Getting into the soil, the toxic isotope of strontium is thus able to accumulate in plant fibers, and then in animal organisms. Thus, the human body slowly but surely accumulates toxins by consuming poisoned foods. Heat treatment of products can save the situation a little, which contributes to a fairly significant reduction in the content of harmful toxin in them.

This radionuclide is very difficult to remove from the body, because it may take him almost half a year to get rid of at least half of the accumulated stock.

What food contains?

Indications for treatment with drugs based on this element

There are still indications for the appointment of a macroelement, despite its possible toxicity. And even a radioactive isotope is used for medical purposes. Its radiation in allowed doses can have a therapeutic effect on erosions, tumors on the skin and mucous membranes. With deeper foci, this method is already used.

Also, its compounds serve as drugs for the treatment of epilepsy, nephritis and correction of deformity in childhood by orthopedists. To some extent, it can serve as an antihelminthic agent.

STRONTIUM (Strontium, Sr) - a chemical element of the periodic system of D. I. Mendeleev, a subgroup of alkaline earth metals. In the human body, S. competes with calcium (see) for inclusion in the crystal lattice of bone oxyapatite (see). 90 Sr, one of the most long-lived radioactive fission products of uranium (see), accumulating in the atmosphere and biosphere during nuclear weapons tests (see), poses a great danger to humanity. S.'s radioactive isotopes are used in medicine for radiation therapy (see), as a radioactive label in diagnostic radiopharmaceuticals (see) in medical biol. research, as well as in atomic electric batteries. S. compounds are used in flaw detectors, in sensitive instruments, and in devices for combating static electricity. In addition, S. is used in radio electronics, pyrotechnics, in the metallurgical and chemical industries, and in the manufacture of ceramic products. S.'s connections are not poisonous. When working with metallic S., one should be guided by the rules for handling alkali metals (see) and alkaline earth metals (see).

S. was discovered as part of a mineral later named SrC03 strontianite in 1787 near the Scottish city of Strontiana.

The serial number of strontium is 38, the atomic weight (mass) is 87.62. The content of S. in the earth's crust averages 4-10 2 wt. %, in sea water - 0.013% (13 mg / l). The minerals strontianite and celestite SrSO 4 are of industrial importance.

The human body contains approx. 0.32 g of strontium, mainly in bone tissue, in the blood, the concentration of S. is normally 0.035 mg / l, in the urine - 0.039 mg / l.

S. is a soft silvery-white metal, t°pl 770°, t°kip 1383°.

According to chem. S.'s properties are similar to calcium and barium (see), in connections valence of strontium 4-2, is chemically active, is oxidized under normal conditions by water with formation of Sr(OH) 2, and also by oxygen and other oxidizing agents.

S. enters the human body hl. arr. with plant foods, as well as with milk. It is absorbed in the small intestine and quickly exchanges with S. contained in the bones. S.'s removal from an organism is strengthened by complexes, amino acids, polyphosphates. The increased content of calcium and fluorine (see) in water interferes with S.'s cumulation in bones. With an increase in the concentration of calcium in the diet by 5 times, S.'s accumulation in the body is halved. Excessive S.'s intake with food and water due to its increased content in the soil of some geochemical. provinces (eg, in some districts of Eastern Siberia) causes an endemic disease - ur disease (see Kashin - Beck disease).

In bones, blood and other biol. S.'s substrates define hl. arr. spectral methods (see Spectroscopy).

radioactive strontium

Natural S. consists of four stable isotopes with mass numbers 84, 86, 87, and 88, of which the latter is the most common (82.56%). Eighteen radioactive isotopes of sulfur are known (with mass numbers 78–83, 85, 89–99) and four isomers of isotopes with mass numbers 79, 83, 85, and 87 (see Isomerism).

In medicine, 90Sr is used for radiation therapy in ophthalmology and dermatology, as well as in radiobiological experiments as a source of β-radiation. 85Sr is produced either by irradiating a strontium target enriched in the 84Sr isotope with neutrons in a nuclear reactor by the reaction 84Sr (11.7) 85Sr, or produced at a cyclotron by irradiating natural rubidium targets with protons or deuterons, for example, by the reaction 85Rb (p, n) 85Sr. The radionuclide 85Sr decays with electron capture, emitting gamma radiation with an energy E gamma equal to 0.513 MeV (99.28%) and 0.868 MeV (< 0,1%).

87mSr can also be obtained by irradiating a strontium target in a reactor by the reaction 86Sr (n, gamma) 87mSr, but the yield of the desired isotope is low, in addition, 85Sr and 89Sr isotopes are formed simultaneously with 87mSr. Therefore, usually 87niSr is obtained using an isotope generator (see Radioactive Isotope Generators) based on the parent isotope of yttrium-87 - 87Y (T1 / 2 = 3.3 days). 87mSr decays with an isomeric transition, emitting gamma radiation with an Egamma energy of 0.388 MeV, and partly with electron capture (0.6%).

89Sr is contained in fission products together with 90Sr; therefore, 89Sr is obtained by irradiating natural sulfur in a reactor. In this case, an 85Sr impurity is also inevitably formed. The 89Sr isotope decays with the emission of P-radiation with an energy of 1.463 MeV (approx. 100%). The spectrum also contains a very weak line of gamma radiation with an energy E gamma equal to 0.95 MeV (0.01%).

90Sr is obtained by isolation from a mixture of uranium fission products (see). This isotope decays with the emission of beta radiation with an energy of E beta equal to 0.546 Meu (100%), without accompanying gamma radiation. The decay of 90Sr leads to the formation of a daughter radionuclide 90Y, which decays (T1 / 2 = 64 hours) with the emission of p-radiation, consisting of two components with Ep equal to 2.27 MeV (99%) and 0.513 MeV (0 .02%). The decay of 90Y also emits very weak gamma radiation with an energy of 1.75 MeV (0.02%).

Radioactive isotopes 89Sr and 90Sr, which are present in the waste of the nuclear industry and are formed during nuclear weapons testing, can enter the human body with food, water, and air when the environment is polluted. Quantification of S.'s migration in the biosphere is usually carried out in comparison with calcium. In most cases, when 90Sr moves from the previous link in the chain to the next, the concentration of 90Sr decreases per 1 g of calcium (the so-called discrimination coefficient), in adults in the body-diet link, this coefficient is 0.25.

Like soluble compounds of other alkaline earth elements, soluble compounds of S. are well absorbed from went. - kish. a path (10-60%), absorption of poorly soluble connections S. (eg, SrTi03) makes less than 1%. The degree of absorption of S.'s radionuclides in the intestine depends on age. With an increase in the calcium content in the diet, S.'s accumulation in the body decreases. Milk promotes increase in S.'s absorption and calcium in intestines. It is believed that this is due to the presence of lactose and lysine in milk.

When inhaled, soluble S. compounds are quickly eliminated from the lungs, while poorly soluble SrTi03 is exchanged in the lungs extremely slowly. Penetration of radionuclide S. through the intact skin makes apprx. one%. Through damaged skin (cut wound, burns, etc.)? as well as from subcutaneous tissue and muscle tissue, S. is absorbed almost completely.

S. is an osteotropic element. Regardless of the route and rhythm of entry into the body, soluble 90Sr compounds selectively accumulate in the bones. Less than 1% of 90Sr is retained in soft tissues.

With intravenous administration, S. is very quickly eliminated from the bloodstream. Soon after administration, the concentration of S. in the bones becomes 100 times or more higher than in soft tissues. Nek-ry distinctions in accumulation 90Sr in separate bodies and fabrics are noted. A relatively higher concentration of 90Sr in experimental animals is found in the kidneys, salivary and thyroid glands, and the lowest - in the skin, bone marrow and adrenal glands. The concentration of 90Sr in the renal cortex is always higher than in the medulla. S. initially lingers on the bone surfaces (periosteum, endosteum), and then is distributed relatively evenly throughout the entire volume of the bone. Nevertheless, the distribution of 90Sr in different parts of the same bone and in different bones turns out to be uneven. During the first time after injection, the concentration of 90Sr in the epiphysis and metaphysis of the bone of experimental animals is approximately 2 times higher than in the diaphysis. From the epiphysis and metaphysis, 90Sr is excreted faster than from the diaphysis: in 2 months. the concentration of 90Sr in the epiphysis and metaphysis of the bone decreases by 4 times, and in the diaphysis almost does not change. Initially 90Sr concentrates in those sites in which there is an active formation of a bone. Abundant blood and lymph circulation in the epimetaphyseal areas of the bone contributes to a more intense deposition of 90Sr in them compared to the diaphysis of the tubular bone. The amount of 90Sr deposition in the bones of animals is not constant. A sharp decrease in 90Sr fixation in bones with age was found in all animal species. Deposition of 90Sr in the skeleton significantly depends on gender, pregnancy, lactation, and the state of the neuroendocrine system. A higher deposition of 90Sr in the skeleton was noted in male rats. In the skeleton of pregnant females, 90Sr accumulates less (up to 25%) than in control animals. Lactation has a significant effect on the accumulation of 90Sr in the skeleton of females. With the introduction of 90Sr 24 hours after birth, 90Sr is retained in the skeleton of rats 1.5-2 times less than in non-lactating females.

The penetration of 90Sr into the tissues of the embryo and fetus depends on the stage of their development, the state of the placenta, and the duration of circulation of the isotope in the mother's blood. Penetration of 90Sr into the fetus is the greater, the longer the gestational age at the time of administration of the radionuclide.

To reduce the damaging effect of strontium radionuclides, it is necessary to limit their accumulation in the body. For this purpose, when the skin is contaminated, it is necessary to quickly decontaminate its open areas (Protection-7 preparation, Era or Astra washing powders, NEDE paste). In case of oral intake of strontium radionuclides, antidotes should be used to bind or absorb the radionuclide. Such antidotes include activated barium sulfate (adso-bar), polysurmin, alginic acid preparations, etc. For example, the drug adsobar, when taken immediately after radionuclides enter the stomach, reduces their absorption by 10-30 times. Adsorbents and antidotes should be prescribed immediately after detection of damage by strontium radionuclides, since delay in this case leads to a sharp decrease in their positive effect. At the same time, it is recommended to prescribe emetics (apomorphine) or to produce abundant gastric lavage, use saline laxatives, cleansing enemas. In case of damage by dust-like preparations, abundant washing of the nose and oral cavity, expectorants (thermopsis with soda), ammonium chloride, injections of calcium preparations, diuretics are necessary. In later periods after the lesion, to reduce the deposition of S.'s radionuclides in the bones, it is recommended to use the so-called. stable strontium (S. lactate or S. gluconate). Large doses of oral calcium or intravenous MofyT replace stable strontium preparations if these are not available. In connection with the good reabsorption of strontium radionuclides in the renal tubules, the use of diuretics is also indicated.

Nek-swarm decrease in accumulation of S.'s radionuclides in an organism can be reached by creation of competitive relations between them and stable isotope S. or calcium, and also creation of deficiency of these elements when S.'s radionuclide was already fixed in a skeleton. However, effective means of decorporation of radioactive strontium from the body have not yet been found.

The minimum significant activity that does not require registration or permission from the State Sanitary Inspection for 85mSr, 85Sr, 89Sr and 90Sr is 3.5*10 -8 , 10 -10 , 2.8*10 -11 and 1.2*10, respectively -12 curies/l.

Bibliography: Borisov V.P. and others. Emergency care for acute radiation exposure, M., 1976; Buldakov L. A. and Moskalev Yu. I. Problems of distribution and experimental estimation of admissible levels of Cs137, Sr90 and Ru106, M., 1968, bibliogr.; Voinar A. I. The biological role of trace elements in the body of animals and humans, p. 46, M., 1960; Ilyin JI. A. and Ivannikov A. T. Radioactive substances and wounds, M., 1979; To and with and in fi-on B. S. and T about r ben to about V. P. Life of a bone tissue, M., 1979; JI e in and V. I N. Obtaining radioactive preparations, M., 1972; Metabolism of strontium, ed. J. M. A. Lenihena and others, trans. from English, M., 1971; Poluektov N. S. and others. Analytical chemistry of strontium, M., 1978; P em and G. Course of inorganic chemistry, trans. from German, vol. 1, M., 1972; Protection of the patient in radionuclide investigations, Oxford, 1969, bibliogr.; Table of isotopes, ed. by C. M. Lederer a. V. S. Shirley, N. Y. a. o., 1978.

A. V. Babkov, Yu. I. Moskalev (rad.).

Natural strontium consists of four stable isotopes 88Sr (82.56%), 86Sr (9.86%), 87Sr (7.02%) and 84Sr (0.56%). The abundance of strontium isotopes varies due to the formation of 87 Sr due to the decay of natural 87 Rb. For this reason, the exact isotopic composition of strontium in a rock or mineral that contains rubidium depends on the age and Rb/Sr ratio of that rock or mineral.

Radioactive isotopes with mass numbers from 80 to 97 are artificially obtained, including 90 Sr (T 1/2 = 29.12 years), which is formed during the fission of uranium. The oxidation state is +2, very rarely +1.

The history of the discovery of the element.

Strontium got its name from the mineral strontianite, found in 1787 in a lead mine near Strontian (Scotland). In 1790, the English chemist Crawford Ader (1748–1795) showed that strontianite contained a new, as yet unknown "earth". This feature of strontianite was also established by the German chemist Martin Heinrich Klaproth (Klaproth Martin Heinrich) (1743–1817). The English chemist T. Hop (Hope T.) in 1791 proved that strontianite contains a new element. He clearly distinguished the compounds of barium, strontium and calcium, using, among other methods, the characteristic color of the flame: yellow-green for barium, bright red for strontium, and orange-red for calcium.

Independently of Western scientists, St. Petersburg academician Tobiash (Toviy Egorovich) Lovitz (1757–1804) in 1792, studying the mineral barite, came to the conclusion that, in addition to barium oxide, it also contained "strontium earth" as an impurity. He managed to extract more than 100 g of new "earth" from heavy spar and studied its properties. The results of this work were published in 1795. Lovitz wrote then: “I was pleasantly surprised when I read ... the excellent article by Mr. and middle nitrate salts in all points perfectly coincide with the properties of my same salts ... I had only to check ... the remarkable property of strontium earth - to color the alcohol flame in carmine red, and, indeed, my salt ... possessed to the full extent of this property.

Strontium was first isolated in free form by the English chemist and physicist Humphrey Davy in 1808. Strontium metal was obtained by electrolysis of its moistened hydroxide. The strontium released at the cathode combined with mercury, forming an amalgam. Decomposing the amalgam by heating, Davy isolated the pure metal.

The prevalence of strontium in nature and its industrial production. The content of strontium in the earth's crust is 0.0384%. It is the fifteenth most abundant and immediately follows barium, slightly behind fluorine. Strontium does not occur in free form. It forms about 40 minerals. The most important of them is celestine SrSO 4 . Strontianite SrCO 3 is also mined. Strontium is present as an isomorphic impurity in various magnesium, calcium, and barium minerals.

Strontium is also found in natural waters. In sea water, its concentration is 0.1 mg/l. This means that the waters of the World Ocean contain billions of tons of strontium. Mineral waters containing strontium are considered promising raw materials for isolating this element. In the ocean, part of strontium is concentrated in ferromanganese nodules (4900 tons per year). Strontium is also accumulated by the simplest marine organisms - radiolarians, whose skeleton is built from SrSO 4 .

A thorough assessment of the world's industrial resources of strontium has not been carried out, but they are believed to exceed 1 billion tons.

The largest deposits of celestine are in Mexico, Spain and Turkey. In Russia, there are similar deposits in Khakassia, Perm and Tula regions. However, the demand for strontium in our country is met mainly through imports, as well as processing of apatite concentrate, where strontium carbonate is 2.4%. Experts believe that the extraction of strontium in the recently discovered Kishertskoye deposit (Perm region) may affect the situation on the world market for this product. The price of Permian strontium may turn out to be about 1.5 times lower than the price of American strontium, which now costs about $1,200 per ton.

Characterization of a simple substance and industrial production of metallic strontium.

Strontium metal has a silvery-white color. In its unrefined state, it has a pale yellow color. This is a relatively soft metal, easily cut with a knife. At room temperature, strontium has a cubic face-centered lattice (a -Sr); at temperatures above 231 ° C it turns into a hexagonal modification (b -Sr); at 623° C it transforms into a cubic body-centered modification (g-Sr). Strontium belongs to light metals, the density of its a-form is 2.63 g/cm3 (20°C). The melting point of strontium is 768°C, the boiling point is 1390°C.

Being an alkaline earth metal, strontium actively reacts with non-metals. At room temperature, metallic strontium is covered with a film of oxide and peroxide. It ignites when heated in air. Strontium easily forms nitride, hydride and carbide. At elevated temperatures, strontium reacts with carbon dioxide:

5Sr + 2CO 2 = SrC 2 + 4SrO

Strontium metal reacts with water and acids, releasing hydrogen from them:

Sr + 2H 3 O + = Sr 2+ + H 2 + 2H 2 O

The reaction does not proceed in cases where sparingly soluble salts are formed.

Strontium dissolves in liquid ammonia with the formation of dark blue solutions, from which, upon evaporation, a brilliant copper-colored ammonia Sr(NH 3) 6 can be obtained, gradually decomposing to the amide Sr(NH 2) 2.

To obtain metallic strontium from natural raw materials, the celestite concentrate is first reduced by heating with coal to strontium sulfide. Strontium sulfide is then treated with hydrochloric acid, and the resulting strontium chloride is dehydrated. The strontianite concentrate is decomposed by firing at 1200°C, and then the resulting strontium oxide is dissolved in water or acids. Often, strontianite is immediately dissolved in nitric or hydrochloric acid.

Strontium metal is obtained by electrolysis of a mixture of molten strontium chloride (85%) and potassium or ammonium chloride (15%) on a nickel or iron cathode at 800 ° C. The strontium obtained by this method usually contains 0.3–0.4% potassium.

High-temperature reduction of strontium oxide with aluminum is also used:

4SrO + 2Al = 3Sr + SrO Al 2 O 3

Silicon or ferrosilicon is also used for metallothermic reduction of strontium oxide. The process is carried out at 1000°C in a vacuum in a steel tube. Strontium chloride is reduced by metallic magnesium in a hydrogen atmosphere.

The largest producers of strontium are Mexico, Spain, Turkey and the UK.

Despite the rather high content in the earth's crust, metallic strontium has not yet found wide application. Like other alkaline earth metals, it is able to purify ferrous metal from harmful gases and impurities. This property gives strontium the prospect of application in metallurgy. In addition, strontium is an alloying addition to magnesium, aluminum, lead, nickel and copper alloys.

Strontium metal absorbs many gases and is therefore used as a getter in electrovacuum technology.

Strontium compounds.

The predominant oxidation state (+2) for strontium is primarily due to its electronic configuration. It forms numerous binary compounds and salts. Chloride, bromide, iodide, acetate and some other salts of strontium are readily soluble in water. Most strontium salts are sparingly soluble; among them sulfate, fluoride, carbonate, oxalate. Sparingly soluble salts of strontium are easily obtained by exchange reactions in an aqueous solution.

Many strontium compounds have an unusual structure. For example, isolated strontium halide molecules are noticeably curved. The bond angle is ~120° for SrF 2 and ~115° for SrCl 2 . This phenomenon can be explained by sd- (rather than sp-) hybridization.

Strontium oxide SrO is obtained by calcining the carbonate or dehydrating the hydroxide at a red heat temperature. The lattice energy and melting point of this compound (2665°C) are very high.

When strontium oxide is calcined in an oxygen environment at high pressure, peroxide SrO 2 is formed. A yellow superoxide Sr(O 2) 2 was also obtained. When interacting with water, strontium oxide forms hydroxide Sr(OH) 2 .

Strontium oxide– a component of oxide cathodes (electron emitters in electrovacuum devices). It is part of the glass kinescopes of color TVs (absorbs X-rays), high-temperature superconductors, pyrotechnic mixtures. It is used as a starting material for the production of strontium metal.

In 1920, the American Hill first used matte glaze, which included oxides of strontium, calcium and zinc, but this fact went unnoticed, and the new glaze did not compete with traditional lead glazes. Only during the Second World War, when lead became especially scarce, they remembered Hill's discovery. This caused an avalanche of research: dozens of recipes for strontium glazes appeared in different countries. Strontium glazes are not only less harmful than lead glazes, but also more affordable (strontium carbonate is 3.5 times cheaper than red lead). At the same time, they have all the positive qualities of lead glazes. Moreover, products coated with such glazes acquire additional hardness, heat resistance, and chemical resistance.

Based on oxides of silicon and strontium, enamels are also prepared - opaque glazes. Additives of titanium and zinc oxides make them opaque. Porcelain items, especially vases, are often decorated with crackle glazes. Such a vase seems to be covered with a grid of painted cracks. The basis of the crackle technology is the different coefficients of thermal expansion of glaze and porcelain. Glazed porcelain is fired at a temperature of 1280–1300°C, then the temperature is reduced to 150–220°C, and the product, which has not yet completely cooled down, is immersed in a solution of coloring salts (for example, cobalt salts, if you want to get a black grid). These salts fill the resulting cracks. After that, the product is dried and heated again to 800–850 ° C - the salts melt in the cracks and seal them.

Strontium hydroxide Sr(OH)2 is considered a moderately strong base. It is not very soluble in water, so it can be precipitated by the action of a concentrated alkali solution:

SrCl 2 + 2KOH(conc) = Sr(OH) 2 Ї + 2KCl

When crystalline strontium hydroxide is treated with hydrogen peroxide, SrO 2 8H 2 O is formed.

Strontium hydroxide can be used to isolate sugar from molasses, but the cheaper calcium hydroxide is usually used.

Strontium carbonate SrCO 3 is slightly soluble in water (2 10 -3 g per 100 g at 25 ° C). In the presence of excess carbon dioxide in solution, it is converted into bicarbonate Sr(HCO 3) 2 .

When heated, strontium carbonate decomposes into strontium oxide and carbon dioxide. It reacts with acids to release carbon dioxide and form the corresponding salts:

SrCO 2 + 3HNO 3 \u003d Sr (NO 3) 2 + CO 2 + H 2 O

The main areas of strontium carbonate in the modern world are the production of kinescopes for color televisions and computers, ceramic ferrite magnets, ceramic glazes, toothpaste, anti-corrosion and phosphorescent paints, high-tech ceramics, and pyrotechnics. The most capacious areas of consumption are the first two. At the same time, the demand for strontium carbonate in the production of television glass is increasing with the growing popularity of larger television screens. It is possible that developments in flat-panel TV technology will reduce the demand for strontium carbonate for television displays, but industry experts believe that flat-panel TVs will not become significant competitors in the next 10 years.

Europe consumes the lion's share of strontium carbonate for the production of ferrite strontium magnets, which are used in the automotive industry, where they are used for magnetic shutters in car doors and brake systems. In the USA and Japan, strontium carbonate is used primarily in the production of television glass.

For many years, the world's largest producers of strontium carbonate were Mexico and Germany, the production capacity of which is now 103 thousand and 95 thousand tons per year, respectively. In Germany, imported celestine is used as a raw material, while Mexican factories work on local raw materials. Recently, the annual capacity for the production of strontium carbonate has expanded in China (up to about 140 thousand tons). Chinese strontium carbonate is actively sold in Asia and Europe.

Strontium nitrate Sr(NO 3) 2 is highly soluble in water (70.5 g per 100 g at 20 ° C). It is obtained by reacting metallic strontium, oxide, hydroxide or carbonate of strontium with nitric acid.

Strontium nitrate is a component of pyrotechnic compositions for signal, lighting and incendiary rockets. It colors the flame carmine red. Although other compounds of strontium give the flame the same color, it is nitrate that is preferred in pyrotechnics: it not only colors the flame, but also serves as an oxidizing agent. Decomposing in a flame, it releases free oxygen. In this case, strontium nitrite is first formed, which then turns into oxides of strontium and nitrogen.

In Russia, strontium compounds were widely used in pyrotechnic compositions. During the time of Peter the Great (1672-1725), they were used to obtain "amusing lights" that were arranged during various celebrations and festivities. Academician A.E. Fersman called strontium "the metal of red lights."

Strontium sulfate SrSO 4 is slightly soluble in water (0.0113 g in 100 g at 0 ° C). When heated above 1580 ° C, it decomposes. It will be obtained by precipitation from solutions of strontium salts with sodium sulfate.

Strontium sulfate is used as a filler in the manufacture of paints and rubber and as a weighting agent in drilling fluids.

Strontium chromate SrCrO 4 precipitates as yellow crystals when solutions of chromic acid and barium hydroxide are mixed.

Strontium dichromate, formed by the action of acids on chromate, is highly soluble in water. To convert strontium chromate to dichromate, a weak acid such as acetic acid is sufficient:

2SrCrO 4 + 2CH 3 COOH = 2Sr 2+ + Cr 2 O 7 2– + 2CH 3 COO – + H 2 O

In this way it can be separated from the less soluble barium chromate, which can only be converted to dichromate by the action of strong acids.

Strontium chromate has high light resistance, it is very resistant to high temperatures (up to 1000 ° C), it has good passivating properties with respect to steel, magnesium and aluminum. Strontium chromate is used as a yellow pigment in the production of varnishes and art paints. It is called "strontium yellow". It is included in primers based on water-soluble resins and especially primers based on synthetic resins for light metals and alloys (aviation primers).

strontium titanate SrTiO 3 does not dissolve in water, but goes into solution under the action of hot concentrated sulfuric acid. It is obtained by sintering strontium and titanium oxides at 1200–1300°C or coprecipitated sparingly soluble compounds of strontium and titanium above 1000°C. Strontium titanate is used as a ferroelectric, it is part of piezoceramics. In microwave technology, it serves as a material for dielectric antennas, phase shifters and other devices. Strontium titanate films are used in the manufacture of nonlinear capacitors and infrared radiation sensors. With their help, layered structures are created dielectric - semiconductor - dielectric - metal, which are used in photodetectors, storage devices and other devices.

Strontium hexaferrite SrO·6Fe 2 O 3 is obtained by sintering a mixture of iron (III) oxide and strontium oxide. This compound is used as a magnetic material.

Strontium fluoride SrF 2 is slightly soluble in water (just over 0.1 g in 1 liter of solution at room temperature). It does not react with dilute acids, but goes into solution under the action of hot hydrochloric acid. A mineral containing strontium fluoride, yarlite NaF 3SrF 2 3AlF 3 , was found in the cryolite mines of Greenland.

Strontium fluoride is used as an optical and nuclear material, a component of special glasses and phosphors.

Strontium chloride SrCl 2 is highly soluble in water (34.6% by weight at 20°C). From aqueous solutions below 60.34 ° C, SrCl 2 6H 2 O hexahydrate crystallizes, spreading in air. At higher temperatures, it first loses 4 water molecules, then another one, and at 250 ° C it is completely dehydrated. Unlike calcium chloride hexahydrate, strontium chloride hexahydrate is slightly soluble in ethanol (3.64% by weight at 6°C), which is used for their separation.

Strontium chloride is used in pyrotechnic compositions. It is also used in refrigeration, medicine, and cosmetics.

Strontium bromide SrBr 2 is hygroscopic. In a saturated aqueous solution, its mass fraction is 50.6% at 20 ° C. Below 88.62 ° C, SrBr 2 6H 2 O hexahydrate crystallizes from aqueous solutions, above this temperature SrBr 3 H 2 O monohydrate. Hydrates are completely dehydrated at 345°C.

Strontium bromide is produced by the reaction of strontium with bromine or strontium oxide (or carbonate) with hydrobromic acid. It is used as an optical material.

strontium iodide SrI 2 is highly soluble in water (64.0% by mass at 20°C), worse in ethanol (4.3% by mass at 39°C). Below 83.9 ° C, SrI 2 6H 2 O hexahydrate crystallizes from aqueous solutions, above this temperature - SrI 2 2H 2 O dihydrate.

Strontium iodide serves as the luminescent material in scintillation counters.

Strontium sulfide SrS is obtained by heating strontium with sulfur or by reducing strontium sulfate with coal, hydrogen, and other reducing agents. Its colorless crystals are decomposed by water. Strontium sulfide is used as a component of phosphors, phosphorescent compositions, hair removers in the leather industry.

Strontium carboxylates can be obtained by reacting strontium hydroxide with the corresponding carboxylic acids. Strontium salts of fatty acids ("strontium soaps") are used to make special greases.

Strontium compounds. Extremely active compounds of composition SrR 2 (R = Me, Et, Ph, PhCH 2 etc.) can be obtained using HgR 2 (often only at low temperature).

Bis(cyclopentadienyl)strontium is the product of a direct reaction of the metal with or with cyclopentadiene itself

The biological role of strontium.

Strontium is an integral part of microorganisms, plants and animals. In marine radiolarians, the skeleton consists of strontium sulfate - celestine. Seaweed contains 26-140 mg of strontium per 100 g of dry matter, land plants - about 2.6, marine animals - 2-50, land animals - about 1.4, bacteria - 0.27-30. The accumulation of strontium by various organisms depends not only on their type and characteristics, but also on the ratio of the content of strontium and other elements, mainly calcium and phosphorus, in the environment.

Animals receive strontium with water and food. Some substances, such as algae polysaccharides, interfere with the absorption of strontium. Strontium accumulates in bone tissue, the ashes of which contain about 0.02% strontium (in other tissues - about 0.0005%).

Salts and compounds of strontium are low-toxic substances, however, with an excess of strontium, bone tissue, liver and brain are affected. Being close to calcium in chemical properties, strontium sharply differs from it in its biological action. Excessive content of this element in soils, waters and foodstuffs causes "ur disease" in humans and animals (named after the river Urov in Eastern Transbaikalia) - damage and deformity of the joints, growth retardation and other disorders.

The radioactive isotopes of strontium are especially dangerous.

As a result of nuclear tests and accidents at nuclear power plants, a large amount of radioactive strontium-90 entered the environment, the half-life of which is 29.12 years. Until the testing of atomic and hydrogen weapons in three environments was not banned, the number of victims of radioactive strontium grew from year to year.

Within a year after the completion of atmospheric nuclear explosions, as a result of self-purification of the atmosphere, most of the radioactive products, including strontium-90, fell out of the atmosphere onto the earth's surface. Pollution of the natural environment due to the removal of radioactive products of nuclear explosions from the stratosphere, carried out at the planet's test sites in 1954–1980, now plays a secondary role, the contribution of this process to atmospheric air pollution with 90 Sr is two orders of magnitude less than from the wind lifting of dust from contaminated soil. during nuclear tests and as a result of radiation accidents.

Strontium-90, along with cesium-137, are the main polluting radionuclides in Russia. The radiation situation is significantly affected by the presence of contaminated zones that appeared as a result of accidents at the Chernobyl nuclear power plant in 1986 and at the Mayak plant in the Chelyabinsk region in 1957 (“Kyshtym accident”), as well as in the vicinity of some nuclear fuel cycle enterprises.

Now the average concentrations of 90 Sr in the air outside the territories contaminated as a result of the Chernobyl and Kyshtym accidents have reached the levels observed before the accident at the Chernobyl nuclear power plant. The hydrological systems associated with the areas contaminated during these accidents are significantly affected by the washout of strontium-90 from the soil surface.

Getting into the soil, strontium, together with soluble calcium compounds, enters the plants. More than others accumulate 90 Sr legumes, roots and tubers, less - cereals, including cereals, and flax. Significantly less 90 Sr is accumulated in seeds and fruits than in other organs (for example, 90 Sr is 10 times more in wheat leaves and stems than in grain).

From plants, strontium-90 can pass directly or through animals into the human body. In men, strontium-90 accumulates to a greater extent than in women. In the first months of a child's life, the deposition of strontium-90 is an order of magnitude higher than in an adult, it enters the body with milk and accumulates in rapidly growing bone tissue.

Radioactive strontium is concentrated in the skeleton and thus exposes the body to long-term radioactive effects. The biological effect of 90 Sr is related to the nature of its distribution in the body and depends on the dose of b-irradiation created by it and its daughter radioisotope 90 Y. leukemia and bone cancer. The complete decay of strontium-90, which has entered the environment, will occur only after a few hundred years.

The use of strontium-90.

The radioisotope of strontium is used in the production of atomic electric batteries. The principle of operation of such batteries is based on the ability of strontium-90 to emit electrons with high energy, which is then converted into electrical energy. Elements of radioactive strontium, combined into a miniature battery (the size of a matchbox), are able to operate without recharging without fail for 15–25 years; such batteries are indispensable for space rockets and artificial satellites of the Earth. And Swiss watchmakers successfully use tiny strontium batteries to power electric watches.

Domestic scientists have created an isotope generator of electrical energy to power automatic weather stations based on strontium-90. The warranty period of such a generator is 10 years, during which it is able to supply electric current to devices that need it. All its maintenance consists only in preventive examinations - once every two years. The first samples of the generator were installed in Transbaikalia and in the upper reaches of the taiga river Kruchina.

A nuclear lighthouse operates in Tallinn. Its main feature is radioisotope thermoelectric generators, in which, as a result of the decay of strontium-90, thermal energy is generated, which is then converted into light.

Devices that use radioactive strontium are used to measure thickness. This is necessary for the control and management of the production process of paper, fabrics, thin metal tapes, plastic films, paint coatings. The strontium isotope is used in devices for measuring density, viscosity and other characteristics of a substance, in flaw detectors, dosimeters, and signaling devices. At engineering enterprises, you can often find so-called b-relays, they control the supply of workpieces for processing, check the serviceability of the tool, and the correct position of the part.

During the production of materials that are insulators (paper, fabrics, artificial fibers, plastics, etc.), static electricity is generated due to friction. To avoid this, ionizing strontium sources are used.

Elena Savinkina

DEFINITION

Strontium is the thirty-eighth element of the Periodic Table. Designation - Sr from the Latin "strontium". Located in the fifth period, IIA group. Refers to metals. The core charge is 38.

Strontium occurs in nature mainly as sulfates and carbonates, forming the minerals celestite SrSO 4 and strontianite SrCO 3 . The content of strontium in the earth's crust is 0.04% (mass.).

Metallic strontium in the form of a simple substance is a soft silvery-white (Fig. 1) metal with malleability and plasticity (it is easily cut with a knife). Reactive: oxidizes rapidly in air, interacts quite vigorously with water, and combines directly with many elements.

Rice. 1. Strontium. Appearance.

Atomic and molecular weight of strontium

DEFINITION

Relative molecular weight of a substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element (A r)- how many times the average mass of atoms of a chemical element is greater than 1/12 of the mass of a carbon atom.

Since strontium exists in the free state in the form of monatomic Sr molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 87.62.

Allotropy and allotropic modifications of strontium

Strontium exists in the form of three crystalline modifications, each of which is stable in a certain temperature range. So, up to 215 o C, α-strontium is stable (face-centered cubic lattice), above 605 o C - g - strontium (body-centered cubic lattice), and in the temperature range 215 - 605 o C - b-strontium (hexagonal lattice).

Isotopes of strontium

It is known that in nature rubidium can be in the form of the only stable isotope 90 Sr. The mass number is 90, the atomic nucleus contains thirty-eight protons and fifty-two neutrons. Radioactive.

Strontium ions

At the outer energy level of the strontium atom, there are two electrons that are valence:

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

As a result of chemical interaction, strontium gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Sr 0 -2e → Sr 2+ .

Molecule and atom of strontium

In the free state, strontium exists in the form of monatomic Sr molecules. Here are some properties that characterize the atom and molecule of strontium:

Strontium alloys

Strontium has found wide application in metallurgy as an alloying component of copper-based alloys.

Examples of problem solving

EXAMPLE 1

Exercise	Determine which of the two indicated bases will be stronger: strontium (II) hydroxide (Sr (OH) 2) or cadmium hydroxide (Cd (OH) 2)?
Decision	Before answering the question of the problem, it is necessary to give a concept of what is meant by the force of foundation. Foundation strength- this is a characteristic of this class of inorganic compounds, demonstrating the strength of the bond of protons, which were “torn off” from the solvent molecule during the chemical reaction. Strontium and cadmium are located in the same period, as well as in the same group of the Periodic Table of D.I. Mendeleev (II), only in different subgroups. Strontium is an element of the main, and cadmium is a secondary subgroup. With the same number of electron shells, the radius of a cadmium atom is smaller than that of strontium, which makes it difficult for an electron to recoil from an atom. In addition, the electronegativity of cadmium is higher than that of strontium, so cadmium will "with great pleasure" accept the electrons of another atom, rather than give up its own; therefore, strontium (II) hydroxide (Sr (OH) 2) is a stronger base.
Answer	Strontium (II) hydroxide (Sr (OH) 2)