Strontium (sym. Sr, dyad, atomic weight, —sp. gr. 2.542) is a ductile and malleable metal, somewhat harder than lead, and of a pale yellow colour. When heated in the air it burns with a crimson flame, and becomes converted into its oxide, strontia, . It is unaffected by the action of dry air, but it decomposes water at an ordinary temperature, hydrogen being explosively developed; and it burns in chlorine gas, and in the vapour of iodine, bromine, and sulphur. It dissolves in dilute nitric acid, but the strong acid has scarcely any effect on it. This metal does not occur in the native state, but exists as a carbonate in the mineral Strontianite (so called from its being first found in 1790 near Strontian, a village of Ardnamurchan parish, Argyllshire, 24 miles SW. of Fort-William), and as a sulphate in the mineral known as Celestine. It is obtained by the voltaic decomposition of the chloride of strontium. This metal bears to barium the same close relation that sodium bears to potassium; and the compounds of strontium resemble those of barium not only in their composition but in their properties. The oxide of strontium, commonly known as Strontia, is obtained in the same way as the corresponding oxide of barium, which it resembles in almost all respects, except that it is inert when taken into the system, while baryta is poisonous. When a small quantity of water is poured upon it it slakes, giving out heat.
The salts of strontia resemble those of baryta in their general characters, and in their being precipitated from their solutions by sulphuric acid and the soluble sulphates; but they differ from them in not being thrown down by silico-fluoric acid or hyposulphite of soda, and in their communicating to the flame of the spirit-lamp and to burning substances generally a brilliant purple-red colour. The salts of strontia occur only in the mineral kingdom, and are never found as normal ingredients of organic bodies. Carbonate of Strontia, , occurs native both in a massive and crystalline form, and may be obtained artificially as a white powder by precipitating a soluble salt of strontia with carbonate of soda. Sulphate of Strontia occurs native in Celestine, a mineral which is found in beautiful rhombic prisms in Sicily. Nitrate of Strontia, , separates from a hot concentrated solution in large colourless transparent anhydrous octahedral crystals, which dissolve freely in water. By the addition of nitric acid it is precipitated from its aqueous solution. This salt is insoluble in alcohol, but when finely powdered and mixed with it it communicates to the alcoholic flame a beautiful red or crimson colour. In consequence of this property it is employed by the makers of fireworks, especially for Bengal lights (see PYROTECHNY); but the mixture made for this purpose is highly dangerous, and has caused bad accidents by igniting spontaneously. The most important of the haloid salts of strontia is the Chloride, , which may be obtained in crystals containing six equivalents of water. The water is expelled at a moderate heat, leaving the chloride anhydrous. The chloride is the only salt from which the metal has hitherto been obtained.
Strontia was discovered as an independent substance almost simultaneously by Hope and Klaproth in 1793. In 1807 Davy obtained barium and strontium from their oxides, but not in a pure state; and it was not till 1855 that Bunsen and Matthiessen succeeded in procuring perfectly pure specimens of the metal.