Strontium, one of the three metals of the alkaline earths, barium and calcium being the other two. It was first obtained from the native carbonate of strontium by Sir Humphry Davy in 1808, in a manner similar to that for barium. The pure metal may be more readily obtained from the fused chloride by electrolysis according to the method of Matthiessen. A small porcelain crucible, having a porous cell in the middle, is filled with anhydrous chloride of strontium mixed with a little sal ammoniac. The negative electrode, consisting of a thin iron wire wound round a thicker one, and all but about 1/16 of an inch covered with a piece of tobacco-pipe stem, is placed in the porous cell. The positive electrode, in the form of an iron cylinder, is placed in the crucible round the porous cell. The heat is so regulated that a crust shall form in the cell, under which the metal collects during the passage of the galvanic current. The pure metal has a pale yellow color and a specific gravity of 2.54. Its symbol is Sr; its atomic weight, 87.6. When heated in the air it burns with a crimson flame, emitting sparks, and decomposes water with evolution of hydrogen gas. It is about as hard as gold, very ductile, and may be hammered into very thin plates.

With oxygen it forms two anhydrous oxides: strontium monoxide, SrO, and strontium dioxide, Sr02, each of which unites with water to form a hydrate. The oxide, called strontia, has the same relation to the metal that lime has to calcium; and, like lime, one of its most important compounds is the carbonate, or stron-tianite, which was discovered in 1787 at Stron-tian in Argyleshire, Scotland, whence the name. The mineral was then regarded as a carbonate of barium, but Crawfurd's supposition that it contained a peculiar earth was confirmed by Hope in 1792, and by Klaproth in 1793. - Principal Salts. The chloride (SrCl2), the iodide (Srl2), and the bromide (SrBr2) are all easily soluble in water and decomposable by heat. The nitrate (Sr2N03) is extensively used in producing the crimson lights of fireworks. A mixture of 40 parts of strontium nitrate with from 5 to 10 parts of potassic chlorate, 12 of sulphur, and 4 of antimonious sulphide, deflagrates with a magnificent crimson color. Its preparation is dangerous, in consequence of its liability to ignite spontaneously.

Nitrate of strontia may be prepared by treating the nativo carbonate with dilute nitric acid, but it is more usual to employ the native sulphate, which is reduced to a Sulphide by heating it with charcoal, and then subjected to the action of dilute nitric acid. It crystallizes from hot, concentrated solutions in anhydrous octahedrons, which are insoluble in alcohol, but soluble in half their weight of boiling water and in five parts of cold water. From the cold solution it may be obtained in monoclinic crystals, having four molecules of water. Sulphate of strontium (SrSO4) is found native as the mineral celes-tine, so named from its occasional delicate blue color, although it occurs white, gray, yellow, and red. It may also bo prepared by the action of sulphuric acid on strontianite, or of a soluble strontia salt, as the nitrate, on another metallic sulphate. Its crystals are modifications of the right rhombic prism, being iso-morphous with the sulphates of barium and calcium. The mineral is usually associated with limestone, or sandstone of the Silurian, Devonian, and other formations. It is also found in beds of gypsum, rock salt, and clay, and sometimes in trap rocks, and with volcanic sulphur. Splendid crystals are found at Gir-genti, Sicily, associated with sulphur and gypsum.

It is found at Bex in Switzerland, at Dornburg in Saxe-Weimar, in Tyrol, in rock salt at Ischl in Austria, and in trap rocks near Tantallan in East Lothian, Scotland. Beautiful bluish crystals occur in Trenton limestone about Lake Huron, particularly on Strontian island, and at Kingston, Canada. Fine specimens have been found at Schoharie and at Lockport, N. Y. A blue, fibrous celestine is found near Frankstown, Huntingdon co., Pa.; on Drummond island, Lake Erie, it occurs mixed with barium.