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 SrF2 and ~115° for SrCl2. 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 medium at high pressure, peroxide SrO2 is formed. A yellow superoxide Sr(O2)2 was also obtained. When interacting with water, strontium oxide forms hydroxide Sr(OH)2.
Strontium oxide is 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 triggered an avalanche of research: different countries dozens of recipes for strontium glazes appeared. 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 positive traits 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 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 need 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:
SrCl2 + 2KOH(conc) = Sr(OH) 2Ї + 2KCl
When crystalline strontium hydroxide is treated with hydrogen peroxide, SrO2 8H2O is formed.
Strontium hydroxide can be used to isolate sugar from molasses, but the cheaper calcium hydroxide is usually used.
Strontium carbonate SrCO3 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(HCO3)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:
SrCO2 + 3HNO3 = Sr(NO3)2 + CO2 + H2O
The main spheres of strontium carbonate in modern world- production of kinescopes for color televisions and computers, ceramic ferrite magnets, ceramic glazes, toothpaste, anti-corrosion and phosphorescent paints, high-tech ceramics, in 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 television screens more than large sizes. 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. IN Lately annual capacity for the production of strontium carbonate expanded in China (up to about 140 thousand tons). Chinese strontium carbonate is actively sold in Asia and Europe.
Strontium nitrate Sr(NO3)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 SrSO4 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 SrCrO4 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:
2SrCrO4 + 2CH3COOH = 2Sr2+ + Cr2O72- + 2CH3COO- + H2O
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 SrTiO3 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 co-precipitated 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 sensors infrared radiation. With their help, layered structures of dielectric - semiconductor - dielectric - metal are created, which are used in photodetectors, memory devices and other devices.
Strontium hexaferrite SrO 6Fe2O3 is obtained by sintering a mixture of iron (III) oxide and strontium oxide. This compound is used as a magnetic material.
Strontium fluoride SrF2 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 water. of hydrochloric acid. A mineral containing strontium fluoride, yarlite NaF 3SrF2 3AlF3, 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 SrCl2 is highly soluble in water (34.6% by weight at 20°C). From aqueous solutions below 60.34°C, SrCl2 6H2O hexahydrate crystallizes, deliquescent 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 SrBr2 is hygroscopic. In a saturated aqueous solution, its mass fraction is 50.6% at 20 ° C. Below 88.62 ° C, SrBr2 6H2O hexahydrate crystallizes from aqueous solutions, above this temperature - SrBr3 H2O monohydrate. Hydrates are completely dehydrated at 345°C.
Strontium bromide is obtained by the reaction of strontium with bromine or strontium oxide (or carbonate) with hydrobromic acid. It is used as an optical material.
Strontium iodide SrI2 is highly soluble in water (64.0% by weight at 20°C), worse - in ethanol (4.3% by weight at 39°C). Below 83.9°C, SrI2 6H2O hexahydrate crystallizes from aqueous solutions; above this temperature, SrI2 2H2O dihydrate crystallizes.
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 SrR2 (R = Me, Et, Ph, PhCH2, etc.) can be obtained using HgR2 (often only at low temperature).
Bis(cyclopentadienyl)strontium is the product of a direct reaction of the metal with or with cyclopentadiene itself.
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. Professor Klaproth on strontium earth, about which there had been a very unclear idea before ... and nitrate medium 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 a carmine red color, 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, Türkiye and the UK.
Despite the relatively large content in the earth's crust, wide application metallic strontium has not yet been found. 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 need 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 obtained 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. Close to calcium chemical properties, strontium differs sharply from it in its biological action. Excessive content of this element in soils, waters and foodstuffs causes "Urov disease" in humans and animals (named after the Urov River in Eastern Transbaikalia) - joint damage and deformity, 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 in environment received a large number of radioactive strontium-90, which has a half-life of 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 the self-purification of the atmosphere, most of the radioactive products, including strontium-90, fell out of the atmosphere onto the surface of the earth. Pollution of the natural environment due to the removal from the stratosphere of radioactive products of nuclear explosions carried out at the planet's test sites in 1954–1980 now plays a secondary role, the contribution of this process to pollution atmospheric air 90 Sr is two orders of magnitude less than from wind-driven dust rise from soil contaminated 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 Chernobyl nuclear power plant in 1986 and at the Mayak Production Association in Chelyabinsk region in 1957 (“Kyshtym accident”), as well as in the vicinity of some enterprises of the nuclear fuel cycle.
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 for 15–25 years, such batteries are indispensable for space rockets and artificial satellites 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 shock 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
Literature:
Taube P.R., Rudenko E.I. From hydrogen to... nobelium? M., graduate School, 1961
Popular library of chemical elements. M., Nauka, 1977
Greenwood N.N., Earnshaw A. Chemistry of the Elements, Oxford: Butterworth, 1997
Strontium hydroxide- inorganic base (alkali), consisting of one ion strontium and two hydroxide ions, having chemical formula Sr(OH) 2 .
Physical properties
Colorless hygroscopic tetragonal crystals system. Slightly soluble in water (0.41 g/100 ml at 0°C). Solubility increases in the presence NH4Cl.
Forms crystalline hydrates Sr(OH) 2 H 2 O and Sr(OH) 2 8H 2 O.
Receipt
- In the laboratory: cooling effect on soluble strontium salts sodium hydroxide :
- In industry: reaction SrO with water:
Chemical properties
- How does a strong base react with acids and acidic oxides with the formation of relevant salts.
- When heated above 700 °C, it decomposes:
- When exposed to crystalline Sr(OH) 2 concentrated H 2 O 2 forms strontium peroxide SrO 2 8H 2 O.
Application
Strontium hydroxide is used mainly for refining beet sugar and also as a stabilizer for the production of plastics. Can be used as a source of strontium ions when the presence of chloride ions is undesirable. Intermediate product to obtain strontium carbonate.
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Literature
- Chemical Encyclopedia / Ed.: Knunyants I.L. etc. - M .: Soviet Encyclopedia, 1995. - V. 4 (Half-Three). - 639 p. - ISBN 5-82270-092-4.
An excerpt characterizing strontium hydroxide
- Oh, what a horror! - said, come back from the yard, cold and frightened Sonya. - I think all of Moscow will burn, a terrible glow! Natasha, look now, you can see it from the window from here, ”she said to her sister, apparently wanting to entertain her with something. But Natasha looked at her, as if not understanding what she was being asked, and again stared with her eyes at the corner of the stove. Natasha has been in this state of tetanus since this morning, from the very time that Sonya, to the surprise and annoyance of the countess, for no reason at all, found it necessary to announce to Natasha about the wound of Prince Andrei and about his presence with them on the train. The countess was angry with Sonya, as she rarely got angry. Sonya cried and asked for forgiveness, and now, as if trying to make amends for her guilt, she did not stop caring for her sister.“Look, Natasha, how terribly it burns,” said Sonya.
- What is on fire? Natasha asked. – Oh, yes, Moscow.
And as if in order not to offend Sonya by her refusal and to get rid of her, she moved her head to the window, looked so that she obviously could not see anything, and again sat down in her former position.
- Didn't you see it?
“No, really, I saw it,” she said in a pleading voice.
Both the countess and Sonya understood that Moscow, the fire of Moscow, whatever it was, of course, could not matter to Natasha.
The count again went behind the partition and lay down. The countess went up to Natasha, touched her head with her upturned hand, as she did when her daughter was sick, then touched her forehead with her lips, as if to find out if there was a fever, and kissed her.
- You are cold. You're all trembling. You should go to bed,” she said.
- Lie down? Yes, okay, I'll go to bed. I'm going to bed now, - said Natasha.
Since Natasha was told this morning that Prince Andrei was seriously wounded and was traveling with them, she only in the first minute asked a lot about where? How? is he dangerously injured? and can she see him? But after she was told that she was not allowed to see him, that he was seriously injured, but that his life was not in danger, she obviously did not believe what she was told, but convinced that no matter how much she said, she would be answer the same thing, stopped asking and talking. All the way, with big eyes, which the countess knew so well and whose expression the countess was so afraid of, Natasha sat motionless in the corner of the carriage and was now sitting in the same way on the bench on which she sat down. She was thinking about something, something she was deciding or had already decided in her mind now - the countess knew this, but what it was, she did not know, and this frightened and tormented her.
- Natasha, undress, my dear, lie down on my bed. (Only the countess alone was made a bed on the bed; m me Schoss and both young ladies had to sleep on the floor in the hay.)