Three allotropic forms of the metal exist, with transition points at 235 and 540C. Properties Strontium is softer than calcium and decomposes in water more vigorously. It does not absorb nitrogen below 380C. It should be kept under kerosene to prevent oxidation. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish color with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart a beautiful crimson color to flames, and these salts are used in pyrotechnics and in the production of flares.
Natural strontium is a mixture of four stable isotopes.
Of greatest importance is 90Sr with a half-life of 29 years. It is a product of nuclear fallout and presents a health problem. Uses The major use for strontium at present is in producing glass for color television picture tubes. It has also found use in producing ferrite magnets and in refining zinc. Strontium titanate is an interesting optical material as it has an extremely high refractive index and an optical dispersion greater than that of diamond.