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rubidiumstrontiumyttrium
Ca

Sr

Ba
Appearance
silvery white metallic
General properties
Name, symbol, number strontium, Sr, 38
Element category alkaline earth metal
Group, period, block 25, s
Standard atomic weight 87.62g·mol−1
Electron configuration [Kr] 5s2
Electrons per shell 2, 8, 18, 8, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 2.64 g·cm−3
Liquid density at m.p. 2.375 g·cm−3
Melting point 1050 K, 777 °C, 1431 °F
Boiling point 1655 K, 1382 °C, 2520 °F
Heat of fusion 7.43 kJ·mol−1
Heat of vaporization 136.9 kJ·mol−1
Specific heat capacity (25 °C) 26.4 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 796 882 990 1139 1345 1646
Atomic properties
Oxidation states 2, 1[1] (strongly basic oxide)
Electronegativity 0.95 (Pauling scale)
Ionization energies 1st: 549.5 kJ·mol−1
2nd: 1064.2 kJ·mol−1
3rd: 4138 kJ·mol−1
Atomic radius 215 pm
Covalent radius 195±10 pm
Van der Waals radius 249 pm
Miscellanea
Crystal structure cubic face-centered
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 132 nΩ·m
Thermal conductivity (300 K) 35.4 W·m−1·K−1
Thermal expansion (25 °C) 22.5 µm·m−1·K−1
Shear modulus 6.1 GPa
Poisson ratio 0.28
Mohs hardness 1.5
CAS registry number 7440-24-6
Most stable isotopes
Main article: Isotopes of strontium
iso NA half-life DM DE (MeV) DP
82Sr syn 25.36 d ε - 82Rb
83Sr syn 1.35 d ε - 83Rb
β+ 1.23 83Rb
γ 0.76, 0.36 -
84Sr 0.56% 84Sr is stable with 46 neutrons
85Sr syn 64.84 d ε - 85Rb
γ 0.514D -
86Sr 9.86% 86Sr is stable with 48 neutrons
87Sr 7.0% 87Sr is stable with 49 neutrons
88Sr 82.58% 88Sr is stable with 50 neutrons
89Sr syn 50.52 d ε 1.49 89Rb
β 0.909D 89Y
90Sr trace 28.90 y β 0.546 90Y

Strontium (pronounced /ˈstrɒnʃiəm/ STRON-shee-əm, /ˈstrɒntiəm/ STRON-tee-əm, or /ˈstrɒnʃəm/ STRON-shəm) is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite. The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years. Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered.

Contents

Characteristics

Dendritic oxidized strontium

Due to its extreme reactivity with oxygen and water, this element occurs naturally only in compounds with other elements, as in the minerals strontianite and celestite.

Strontium is a grey/silvery metal that is softer than calcium and even more reactive in water, with which strontium reacts on contact to produce strontium hydroxide and hydrogen gas. It burns in air to produce both strontium oxide and strontium nitride, but since it does not react with nitrogen below 380°C it will only form the oxide spontaneously at room temperature. It should be kept under a liquid hydrocarbon such as mineral oil or kerosene to prevent oxidation; freshly exposed strontium metal rapidly turns a yellowish color with the formation of the oxide. Finely powdered strontium metal will ignite spontaneously in air at room temperature. Volatile strontium salts impart a crimson color to flames, and these salts are used in pyrotechnics and in the production of flares. Natural strontium is a mixture of four radiostable isotopes.

Compounds

Isotopes

Strontium has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb, which has a half-life of 4.88 × 1010 years. Thus, there are two sources of 87Sr in any material: that formed in stars along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium, it readily substitutes for Ca in minerals.

Sixteen unstable isotopes are known to exist. Of greatest importance are 90Sr with a half-life of 28.78 years and 89Sr with a half-life of 50.5 days.

  • 90Sr is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc, where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. 90Sr confined inside a concave silver plaque is also used for the medical treatment of a resected pterygium.
  • 89Sr is a short-lived artificial radioisotope which is used in the treatment of bone cancer. In circumstances where cancer patients have widespread and painful bony metastases (secondaries), the administration of 89Sr results in the delivery of radioactive emissions (beta particles in this case) directly to the area of bony problem (where calcium turnover is greatest). The 89Sr is manufactured as the chloride salt (which is soluble), and when dissolved in normal saline can be injected intravenously. Typically, cancer patients will be treated with a dose of 150 MBq. The patient needs to take precautions following this because their urine becomes contaminated with radioactivity, so they need to sit to urinate and double flush the toilet. The beta particles travel about 3.5mm in bone (energy 0.583 MeV) and 6.5mm in tissue, so there is no requirement to isolate patients who have been treated except to say they should not have any one (especially young children) sitting in their laps for 10–40 days[citation needed]. The variation in time results from the variable clearing time for 89Sr which depends on renal function and the number of bony metastases. With a lot of bony metastases, the entire 89Sr dose can be taken up into bone and so the entire radioactivity is retained to decay over a 50.5 day half-life. However, where there are few bony metastases, the large proportion of 89Sr not taken up by the bone will be filtered by the kidney, so that the effective half-life (a combination of the physical and biological half-life) will be much shorter.

History

Strontium is named after the Scottish village of Strontian, having been discovered in the ores taken from the lead mines.[2] In 1790, Adair Crawford, a physician engaged in the preparation of barium, recognised that the Strontian ores exhibited different properties to those normally seen with other "heavy spars" sources. This allowed him to conclude "... it is probable indeed, that the scotch mineral is a new species of earth which has not hitherto been sufficiently examined". The new mineral was named strontites in 1793 by Thomas Charles Hope, a professor of medicine at the University of Glasgow.[3] He confirmed the earlier work of Crawford and recounted: " ... Considering it a peculiar earth I thought it necessary to give it an name. I have called it Strontites, from the place it was found; a mode of derivation in my opinion, fully as proper as any quality it may possess, which is the present fashion". The element was eventually isolated by Sir Humphry Davy in 1808 by the electrolysis of a mixture containing strontium chloride and mercuric oxide, and announced by him in a lecture to the Royal Society on 30 June 1808. In keeping with the naming of the other alkaline earths, he changed the name to strontium.[4][5][6]

Occurrence

Strontium output in 2005

According to the British Geological Survey, China was the top producer of strontium in 2007, with over two-thirds world share, followed by Spain, Mexico, Turkey, Argentina and Iran.[7]

Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development.[8] The metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride:

Sr2+ + 2 e → Sr
2 Cl → Cl2 (g) + 2 e

Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. The largest commercially exploited deposits are found in England.

Applications

As a pure metal strontium is used in strontium 90%-aluminium 10% alloys of an eutectic composition for the modification of aluminium-silicon casting alloys.[9] Strontium is 2% by weight of AJ62 alloy, a durable, creep-resistant magnesium alloy used in car and motorcycle engines by BMW.

CRT computer monitor front panel made from strontium and barium oxide containing glass

The primary use for strontium compounds is in glass for colour television cathode ray tubes to prevent X-ray emission.[10][11] All parts of the CRT tube have to absorb X-rays. In the neck and the funnel of the tube lead glass is used for this purpose, but this type of glass shows a browning effect due to the interaction of the X-rays with the glass. Therefore the front panel has to use a different glass mixture, in which strontium and barium are the X-ray absorbing materials. The average values for the class mixture determined for a recycling studie in 2005 is 8.5% strontium oxide and 10% barium oxide.[12]

Scientific (low quantity) use :

  • Strontium is used in studies of neurotransmitter release in neurons. Like calcium, strontium facilitates synaptic vesicle fusion with the synaptic membrane. But unlike calcium, strontium causes asynchronous vesicle fusion. Therefore, replacing calcium in the culture medium with strontium allows scientists to measure the effects of a single vesicle fusion event, e.g., the size of the postsynaptic response elicited by the neurotransmitter content of a single vesicle.[13][14]

Uses of radioactive strontium isotopes :

  • 89Sr is the active ingredient in Metastron, a radiopharmaceutical used for bone pain secondary to metastatic bone cancer. The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis. This localization focuses the radiation exposure on the cancerous lesion.
  • 90Sr has been used as a power source for radioisotope thermoelectric generators (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the form of 90Sr used in RTGs, which is strontium fluoride).[15] However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu, another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste.
  • 90Sr is also used in cancer therapy. Its beta emission and long half-life is ideal for superficial radiotherapy.

Strontium isotopes are measured for various reasons :

  • Since Strontium is so similar to calcium, it is incorporated in the bone. All four stable isotopes are incorporated, in roughly similar proportions as they are found in nature (please see below). However the actual distribution of the isotopes tends to vary greatly from one geographical location to another. Thus analyzing the bone of an individual can help determine the region it came from. This approach helps to identify the ancient migration patterns as well as the origin of commingled human remains in battlefield burial sites. Strontium thus helps forensic scientists too.
  • 87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments. Dasch (1969) showed that surface sediments of Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses.[16] A good example of a fluvial-marine system to which Sr isotope provenance studies have been successfully employed is the River Nile-Mediterranean system,[17] Due to the differing ages of the rocks that constitute the majority of the Blue and White Nile catchment areas of the changing provenance of sediment reaching the River Nile delta and East Mediterranean Sea can be discerned through Sr isotopic studies. Such changes are climatically controlled in the Late Quaternary.
  • More recently, 87Sr/86Sr ratios have also been used to determine the source of ancient archaeological materials such as timbers and corn in Chaco Canyon, New Mexico.[18][19]
  • 87Sr/86Sr ratios in teeth may also be used to track animal migrations [20][21] or in criminal forensics.

Effect on the human body

The human body absorbs strontium as if it were calcium. Due to the elements being sufficiently similar chemically, the stable forms of strontium might not pose a significant health threat—in fact, the levels found naturally may actually be beneficial (see below) -- but the radioactive 90Sr can lead to various bone disorders and diseases, including bone cancer. The strontium unit is used in measuring radioactivity from absorbed 90Sr.

A recent in-vitro study conducted the NY College of Dental Sciences using strontium on osteoblasts showed marked improvement on bone-building osteoblasts.[22]

The drug strontium ranelate, made by combining strontium with ranelic acid, was found to aid bone growth, increase bone density, and lessen vertebral, peripheral and hip fractures.[23][24] Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass. Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It needs to be prescribed by a doctor, delivered by a pharmacist, and requires strict medical supervision. Currently (early 2007), it is not available in Canada or the United States.

There is a long history of medical research regarding strontium's benefits, beginning in the 1950s. Studies indicate a lack of undesirable side-effects.[25][26][27][28][29][30][31] Several other salts of strontium such as strontium citrate or strontium carbonate are often presented as natural therapies and sold at a dose that is several hundred times higher than the usual strontium intake. Such compounds are sold in the United States under the Dietary Supplements Health and Education Act of 1994. Their long-term safety and efficacy have never been evaluated on humans using large-scale medical trials.[citation needed]

References

  1. ^ P. Colarusso et al. (1996). "High-Resolution Infrared Emission Spectrum of Strontium Monofluoride". J. Molecular Spectroscopy 175: 158. http://bernath.uwaterloo.ca/media/149.pdf. 
  2. ^ Murray, W. H. (1977). The Companion Guide to the West Highlands of Scotland. London: Collins. 
  3. ^ Murray, T. (1993). "Elemementary Scots: The Discovery of Strontium". Scottish Medical Journal 38: 188-189. 
  4. ^ "Strontian gets set for anniversary". Lochaber News. 19th June 2008. http://www.lochaber-news.co.uk/news/fullstory.php/aid/2644/Strontian_gets_set_for_anniversary.html. 
  5. ^ Weeks, Mary Elvira (1932). "The discovery of the elements: X. The alkaline earth metals and magnesium and cadmium". Journal of Chemical Education 9: 1046 – 1057. 
  6. ^ Partington, J.R. (1942). "The early history of strontium". Annals of Science 5: 157. doi:10.1080/00033794200201411. 
  7. ^ British Geological Survey (2009). World mineral production 2003–07. Keyworth, Nottingham: British Geological Survey. ISBN 978-0-85272-639-6. http://www.bgs.ac.uk/mineralsuk/downloads/wmp_2003_2007.pdf. Retrieved April 6, 2009. 
  8. ^ Ober, Joyce A.. "Mineral Comodity Summaries 2008: Strontium" (PDF). United States Geological Survey. http://minerals.usgs.gov/minerals/pubs/commodity/strontium/mcs-2008-stron.pdf. Retrieved 2008-10-14. 
  9. ^ "Aluminium – Silicon Alloys : Strontium Master Alloys for Fast Al-Si Alloy Modification from Metallurg Aluminium". AZo Journal of Materials Online. http://www.azom.com/Details.asp?ArticleID=3353. Retrieved 2008-10-14. 
  10. ^ "Cathode Ray Tube Glass-To-Glass Recycling" (PDF). ICF Incorporated, USEP Agency. http://yosemite.epa.gov/ee/epa/riafile.nsf/vwAN/S99-23.pdf. Retrieved 2008-10-14. 
  11. ^ Ober, Joyce A.; Polyak, Désirée E.. "Mineral Yearbook 2007: Strontium" (PDF). United States Geological Survey. http://minerals.usgs.gov/minerals/pubs/commodity/strontium/myb1-2007-stron.pdf. Retrieved 2008-10-14. 
  12. ^ Méar, F.; Yot, P.; Cambon, M.; Ribes, M. (2006). "The characterization of waste cathode-ray tube glass.". Waste management 26 (12): 1468–76. doi:10.1016/j.wasman.2005.11.017. ISSN 0956-053X. PMID 16427267. 
  13. ^ Miledi, R. (1966). "Strontium as a Substitute for Calcium in the Process of Transmitter Release at the Neuromuscular Junction". Nature 212: 1233. doi:10.1038/2121233a0. 
  14. ^ Hagler D.J., Jr, Goda Y. (2001). "Properties of synchronous and asynchronous release during pulse train depression in cultured hippocampal neurons". J. Neurophysiol. 85: 2324. 
  15. ^ "What are the fuels for radioisotope thermoelectric generators?". http://www.qrg.northwestern.edu/projects/vss/docs/Power/3-what-are-the-fuels-for-rtgs.html. 
  16. ^ Dasch, J. (1969). "Strontium isotopes in weathering profiles, deep-sea sediments, and sedimentary rocks". Geochimica et Cosmochimica Acta 33 (12): 1521–1552. doi:10.1016/0016-7037(69)90153-7. 
  17. ^ Chester, R.; Cliff, R.A.; Eijsink, L.M.; Herut, B. (1999). "The characterisation of Saharan dusts and Nile particulate matter in surface sediments from the Levantine basin using Sr isotopes". Marine Geology 155 (3–4): 319–330. doi:10.1016/S0025-3227(98)00130-3. 
  18. ^ Benson, L., Cordell, L., Vincent, K., Taylor, H., Stein, J., Farmer, G., and Kiyoto, F. (2003). "Ancient maize from Chacoan great houses: where was it grown?". Proceedings of the National Academy of Sciences 100 (22): 13111–13115. doi:10.1073pnas.2135068100 (inactive 2009-09-13). 
  19. ^ English NB, Betancourt JL, Dean JS, Quade J. (2001). "Strontium isotopes reveal distant sources of architectural timber in Chaco Canyon, New Mexico". Proc Natl Acad Sci USA 98 (21): 11891–6. doi:10.1073/pnas.211305498. ISSN 0027-8424. PMID 11572943. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=11572943. 
  20. ^ Barnett-Johnson, Rachel (2007). "Identifying the contribution of wild and hatchery Chinook salmon (Oncorhynchus tshawytscha) to the ocean fishery using otolith microstructure as natural tags". Canadian Journal of Fisheries and Aquatic Sciences 64 (12): 1683–1692. doi:10.1139/F07-129. 
  21. ^ Porder, S., Paytan, A., and E.A. Hadly (2003). "Mapping the origin of faunal assemblages using strontium isotopes". Paleobiology 29 (2): 197–204. doi:10.1666/0094-8373(2003)029<0197:MTOOFA>2.0.CO;2. 
  22. ^ "The Effects of Strontium Citrate on Osteoblast Proliferation and Differentiation". http://iadr.confex.com/iadr/2007orleans/techprogram/abstract_89231.htm. Retrieved 2009-07-07. 
  23. ^ Meunier P. J., Roux C., Seeman E. et al. (Jan 2004). "effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis.". New England Journal of Medicine 350 (5): 459–468. doi:10.1056/NEJMoa022436. ISSN 0028-4793. PMID 14749454. 
  24. ^ Reginster JY, Seeman E, De Vernejoul MC et al. (May 2005). "Strontium ranelate reduces the risk of nonvertebral fractures in postmenopausal women with osteoporosis: treatment of peripheral osteoporosis (TROPOS) study" (Free full text). J Clin Metab. 90 (5): 2816–2822. doi:10.1210/jc.2004-1774. ISSN 0021-972X. PMID 15728210. http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=15728210. 
  25. ^ Mashiba T, et al, Suppressed bone turnover by biphosphonates increases microdamage accumulation and reduces some biomechanical properties in dog rib, J Bone Miner Res, 15; 4:613-20, 2000
  26. ^ McCaslin FE, et al, The effect of strontium in the treatment of osteoporosis, Proc Staff Meetings Mayo Clinic, 341; 13:329-34,1959
  27. ^ Losee FL, et al, A study of the mineral environment of caries-resistant Navy recruits, Caries Res, 3:223-31, 1969
  28. ^ Meunier PJ, et al, The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis, N Engl J Med, 350; 5:459--68,2004
  29. ^ Marie PJ, et al, An uncoupling agent containing strontium prevents bone loss by depressing bone resorption and maintaining bone formation in estrogen-deficient rats, J Bone Miner Res, 8; 5:607-15, 1993
  30. ^ Reginster JY, et al, Prevention of early postmenopausal bone loss by strontium ranelate: the randomized, two-year, double-masked, dose-ranging, placebo-controlled PREVOS Trial, Osteoporosis Int, 13; 12:925-31, 2002
  31. ^ Marie PJ, et al, Mechanisms of action and therapeutic potential of strontium in bone, Calcif Tissue Int, 69; 3:121-9, 2001

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1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

STRONTIUM [[[Symbol]] Sr, atomic weight 87.62 (0 = 16)], a metallic chemical element belonging to the alkaline earth group. It is found in small quantities very widely distributed in various rocks and soils, and in mineral waters; its chief sources are the minerals strontianite, celestine and barytocelestine. The metal was detected in the mineral strontianite, found at Strontian in Argyllshire, by Cruikshank in 1787, and by Crawford in 17 9 0; and the discovery was confirmed by Hope in 1792 and by Klaproth in 1793. The metal was isolated in 1807 by Sir H. Davy by electrolysing the moist hydroxide or chloride, and has been obtained by A. Guntz and Roederer (Comptes rendus, 1906, 142, p. 400) by heating the hydride in a vacuum to 1000. By electrolysing an aqueous solution of the chloride with a mercury cathode, a liquid and a solid amalgam, SrHgn, are obtained; the latter on heating gives a mixture of Sr 2 Hg 5 and SrHg 5, and on distillation an amalgam passes over, and not the metal. It is a silver-white ductile metal (of specific gravity 2.54) which melts at 8000. It oxidizes rapidly when exposed to air, and burns when heated in air, oxygen, chlorine, bromine or sulphur vapour. With dry ammonia at 60° the metal forms strontium ammonium, which slowly decomposes in a vacuum at 20° giving Sr(NH 3) 2; with carbon monoxide it gives Sr(CO) 2; with oxygen it forms the monoxide and peroxide, and with nitric oxide it gives the hyponitrite (Roederer, Bull. soc. chim., 1906 [iii.], 35, P. 715).

The hydride, SrH 2, was obtained by Guntz on heating strontium amalgam in a current of hydrogen. It is a white solid, which readily decomposes water in the cold and behaves as a strong reducing agent. It dissociates when heated to a high temperature and is not affected by oxygen. The monoxide or strontia, Sr(); is formed by strongly heating the nitrate, or commercially by heating the sulphide or carbonate in superheated steam (at about 500-600° C.). It is a white amorphous powder which resembles lime in its general character. By heating the amorphous form in the electric furnace H. Moissan succeeded in obtaining a crystalline variety. The amorphous form readily slakes with water, and the aqueous solution yields a crystalline hydrated hydroxide approximating in composition to Sr(OH) 2.8H 2 O or Sr(OH) 2.9H 2 O, which on standing in vacuo loses some of its water of crystallization, leaving the monohydrated hydroxide, Sr(OH) 2 H 2 O. The ordinary hydrated variety forms quadratic crystals and behaves as a strong base. It is used in the extraction of sugar from molasses, since it combines with the sugar to form a soluble saccharate, which is removed and then decomposed by carbon dioxide. A hydrated dioxide, approximating in composition to SrO 2.8H 2 O, is formed as a crystalline precipitate when hydrogen peroxide is added to an aqueous solution of strontium hydroxide.

Strontium fluoride, SrF 2, is obtained by the action of hydrofluoric acid on the carbonate, or by the addition of potassium fluoride to strontium chloride solution. It may be obtained crystalline by fusing the anhydrous chloride with a large excess of potassium hydrogen fluoride or by heating the amorphous variety to redness with an excess of an alkaline chloride. Strontium chloride, SrC1 2.6H 2 O, is obtained by dissolving the carbonate in hydrochloric acid, or by fusing the carbonate with calcium chloride and extracting the melt with water. It crystallizes in small colourless needles and is easily soluble in water; the concentrated aqueous solution dissolves bromine and iodine readily. By concentrating the aqueous solution between 90-130° C., or by passing hydrochloric acid gas into a saturated aqueous solution, a second hydrated form of composition, SrC1 2.2H 2 O, is obtained. The anhydrous chloride is formed by heating strontium or its monoxide in chlorine, or by heating the hydrated chloride in a current of hydrochloric acid gas. It is a white solid, which combines with gaseous ammonia to form SrC1 2.8NH 3, and when heated in superheated steam it decomposes with evolution of hydrochloric acid.

Strontium sulphide, SrS, is formed when the carbonate is heated to redness in a stream of sulphuretted hydrogen. It phosphoresces very slightly when pure. Strontium sulphate, SrSO 4, found in the mineral kingdom as celestine, is formed when sulphuric acid or a soluble sulphate is added to a solution of a strontium salt. It is a colourless, amorphous solid, which is almost insoluble in water, its solubility diminishing with increasing temperature; it is appreciably soluble in concentrated sulphuric acid. When boiled with alkaline carbonates it is converted into strontium carbonate.

Strontium nitride, Sr 3 N 2, is formed when strontium amalgam is heated to redness in a stream of nitrogen or by igniting the oxide with magnesium (H. R. Ellis, Chem. News, 1909, 99, p. 4). It is readily decomposed by water, with liberation of ammonia. Strontium nitrate, Sr(N03)2, is obtained by dissolving the carbonate in dilute nitric acid. It crystallizes from water (in which it is very soluble) in monoclinic prisms which approximate in composition to Sr(N03)2.4H20 or Sr(N03)2.5H20. When heated it fuses in its own water of crystallization and becomes anhydrous at 110° C. It is used in pyrotechny for the manufacture of red-fire. A strontium boride, SrB6, was obtained as a black crystalline powder by H. Moissan and P. Williams (Comptes rendus, 1897, 12 3, p. 6 33) by reducing the borate with aluminium in the electric furnace.

Strontium carbide, SrC2, is obtained by heating strontium carbonate with carbon in the electric furnace. It resembles calcium carbide, decomposing rapidly with water, giving acetylene. Strontium carbonate, SrCO 3, found in the mineral kingdom as strontianite, is formed when a solution of a carbonate is added to one of a strontium salt. It is an amorphous solid, insoluble in water, but its solubility is increased in the presence of ammonium nitrate. It loses carbon dioxide when heated to high temperature.

Strontium salts may be recognized by the characteristic crimson colour they impart to the flame of the Bunsen burner and by the precipitation of the insoluble sulphate. On the preparation of pure strontium salts, see Adrian and Bougarel, Journ. pharm. chem., 18 9 2 (5), p. 345; and S. P. L. Soerenoen, Zeit. anorg. chem., 1895, II, p. 305. Recent determinations of the atomic weight of strontium are due to T. W. Richards (Zeit. anorg. Chem-., 1905, 47, p. 1 45), who, by estimating the ratios of strontium bromide and chloride to silver, obtained the values 87.663 and 87.661.


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Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also strontium

German

Chemical Element: Sr (atomic number 38)

Noun

Strontium n

  1. strontium

Simple English

File:Sr,
Granules of tungsten in a glass tube.
Simple English Wiktionary has the word meaning for:

Strontium is a chemical element. It has the chemical symbol Sr. It has the atomic number 38. It is a metal. The colour of the metal is silver-white or yellow-silver. The metal is soft. In chemistry it is placed in a group of metal elements named the alkaline earth metals. Strontium has a high chemical reactivity. The metal turns yellow when exposed to air.

It is found naturally in the minerals celestite and strontianite. The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.

File:Stronzianite
A piece of strontianite.

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