metallic element, symbol Sr, one of the ALKALINE EARTH METALS, (q.v.) in group 2 (or IIa) of the periodic table (see PERIODIC LAW,); at.no. 38, at.wt. 87.62. Strontium melts at about 769° C (about 1416° F), boils at about 1384° C (about 2523° F), and has a sp.gr. of 2.6.

Metallic strontium was first isolated by the British chemist Sir Humphry Davy in 1808; the oxide had been known as early as 1790. Strontium has a silvery color when freshly cut. It is malleable and ductile, oxidizes readily upon exposure to air, and reacts with water to produce strontium hydroxide and hydrogen gas. Like the other alkaline earth metals, it is prepared by electrolysis of fused strontium chloride.

Strontium is never found in the elemental state, occurring chiefly as strontianite, SrCO3, and celestite, SrSO4. Strontium ranks about 15th among the elements in natural abundance in the earth’s crust and is widely distributed in small quantities. The greatest amounts are mined in Mexico, England, and Scotland. Because it emits a brilliant red color when burned in air, strontium is used in the manufacture of fireworks and railroad flares. Strontia (strontium oxide), SrO, is used in recovering sugar from beet-sugar molasses. A radioactive isotope of the element, strontium-85, is used in the detection of bone cancer. For strontium-90, see RADIOACTIVE FALLOUT,.