Strontium

Strontium (Sr. 87.5) is a metallic element which, in all its chemical properties, is closely allied to the metals barium and calcium, between which it forms, as it were, a chemical mean. It was first prepared in 1808 by Sir Humphrey Davy by the electrolysis of the fused chloride, though the probable existence of the metal had been pointed out 15 years before. The metal has a yellow colour, is malleable, and possesses a specific gravity of 2.5. It oxidises on exposure, and readily burns, while if thrown on to water it decomposes it with liberation of hydrogen. It occurs naturally chiefly in the form of sulphate (celestine, SrS0₄) or carbonate (strontianite, Sr00₃) It forms two oxjdes of formulae SrO and Sr0₂, its salts corresponding to the former of these. The hydroxide, Sr(OH}₂ is only slightly soluble in cold, but more readily in hot water, the solution possessing an alkaline reaction. The chloride and nitrate are both soluble salts, the latter being very largely employed in pyrotechny, as, it, in common with other salts of strontium, imparts a magnificent crimson colour to flames. The sulphate is only very slightly soluble in cold water and less soluble in hot, and may thus be precipitated from strontium salts by the addition of a solution of gypsum and boiling. The metal is readily recognised in its compounds by the flame coloration and by its very characteristic spectrum.