STRONTIUM, a metallic chemical element intermediate in its character between barium and calcium, with which it forms a natural " triad." Though widely diffused as a frequent companion of calcium (including oceanic), it occurs nowhere in abundance. Its most important mineral forms are the sulphate, SrSO4, known as Ccelestine (from the sky-blue colour of certain varieties), and the carbonate, discovery was confirmed by Klaproth.

Regarding metallic strontium, see CHEMISTRY, vol. v. pp. 525-6. For the making of strontium preparations strontianite, of course, is the handier raw material, being readily convertible into (for instance) nitrate by treatment with dilute nitric acid. From the nitrate the oxide, SrO, is obtained by prolonged calcination at ultimately a bright red heat, as a greyish.whibe absolutely infusible and non-volatile mass, which acts violently on water with formation of the hydrate, Sr(011)2, which latter readily takes up 8H20 of water to form crystals soluble in fifty parts of cold and far less of boiling water. An impure oxide is obtainable directly from strontianite by strong ignition with charcoal; and from such crude oxide pure crystals of the hydrate are easily produced by obvious operations.

In the working up of ccelestine the first step is to reduce it to sulphide, SrS, by means of charcoal at a red heat. The sulphide when boiled with water is decomposed thus : - 2SrS +211,0 = Sr0H2O+SrSII2S.

Hydrate. Sulph-hydrate.

Both products dissolve in the hot water; from the solution the S of the Sr112S2 is easily eliminated, by treatment with oxide of copper or oxide of zinc, as insoluble metallic sulphide; the filtrate on cooling gives crystals of pure hydrate. From it any strontia salt of i course is easily made by means of the respective acid ; in many cases the salt wished for can be obtained similarly from the sulphide.

Nitrate of strontia from hot solutions crystallizes in anhydrous octahedra, Sr.N206, soluble in about part of boiling and in 5 parts of cold water. From colder solutions hydrated crystals, SrN206+ 41120, separate out. The anhydrous salt is used largely by pyrotechnists for the making of "red fire."

The hydroxide some years ago promised to play an important part in the sugar industry as a precipitant for the cane-sugar known to be present largely in uncrystallizable molasses (see Strom:), but the process so far has failed to take root in industry.