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38. StrontiumName: Strontium
Strontium does not occur as the free element. Strontium is softer than calcium and decomposes water more vigorously. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish colour with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart an excellent crimson colour to flames, and these salts are used in pyrotechnics. Strontium-90 (90Sr) has a half-life of 28 years. It is a product of nuclear fallout and presents a major health problem. Strontium titanate is an interesting optical material as it has an extremely high refractive index and an optical dispersion greater than that of diamond. It has been used as a gemstone, but it is very soft. Adair Crawford recognized the mineral strontianite, named after the Scottish town of Strontian, as differing from other barium minerals in 1790. However, Klaproth and Hope discovered strontium itself in 1798 and metallic strontium was first isolated by Sir Humphry Davy in 1808 using electrolysis. In its pure form strontium is extremely reactive with air and spontaneously combusts. It is therefore considered to be a fire hazard. The human body absorbs strontium as if it were calcium. The stable forms of strontium do not pose a significant health threat, but the radioactive strontium-90 can lead to various bone disorders and diseases, including bone cancer. The strontium unit is used in measuring radioactivity from absorbed strontium-90. Quick links
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