Element Strontium, Sr, Alkaline Earth Metal

Strontium has the combining weight 87.6, and occurs in nature chiefly as sulphate and carbonate. Metallic strontium can be fairly readily obtained by the electrolysis of the fused chloride; it can also be obtained by preparing strontium amalgam by the action of sodium amalgam on a concentrated solution of strontium chloride, and distilling off the mercury. It is a yellowish, rather tough metal which energetically reacts with water even at room temperature.

Strontium forms only the divalent ion Sr^••, whose solutions are colourless, and whose heat of formation is 501 kj.

A very rare mineral, which before that could be found only in a couple of collections, named after the village of Strontian, Lochaber, Scotland. Mineralogists erroneously took it for fluorite or aerated barite (BaSO₄), a mineral consisting of barium sulphate; some of them considered it as barium carbonate (BaCO₃), also known as witherite named after William Withering, who in 1784 recognized it to be chemically distinct from barites.

The earliest chemical work on this mineral was by Crawford in 1790, and by Cruickshank in 1787. They concluded that it contained a new earth. Thomas Hope began to work on the mineral from Strontian in 1791 and in a series of experiments he showed that it contained a "hitherto unknown kind of earth". He called the mineral strontianite and the new earth strontia after the locality of the mine.

Martin Heinrich Klaproth described a series of parallel experiments made with strontianite and witherite. In 1794 he prepared Strontium oxide and Strontium hydroxide.

Johann Tobias (Toviy Yevseevich) Lowitz in 1795 reported that he had prepared 4-5 oz. of strontium chloride from heavy spar from Siberia. He became suspicious that a new earth was contained in it. However it was late: strontianite had already been discovered in 1794. Nevertheless, Lowitz may be credited for detecting strontianite in heavy spar. He investigated in details salts of barium, strontium and calcium, distinguished them, and offered a separation method for chlorides of three metals based on their solubility in spirits.

Metallic strontium was isolated electrolytically in 1808 by Sir Humphry Davy.

Strontium crustal abundance is 0.0384% and is considered to be the 15^th most abundant element following barium and yielding slightly to fluorine. Native Strontium is not found. Strontium is a constituent part of 40 minerals, the most important of which is celestite (celestine) (SrSO₄), which has the same structure as barite and forms very similar crystals forming isomorphous inclusions in various magnesium, calcium and barium minerals.

Strontium occurs also in natural waters. Its concentration in seawater is 0.1 mg/l, which means that oceans contain billions of tons of Strontium. Mineral waters are considered as a perspective source for its extraction. Some of ocean strontium concentrates in ferromanganese nodules (annually 4900 tons). Strontium is accumulated within radiolarians, the marine protozoa the skeletons of which consist almost entirely of SrSO₄.

Strontium concentration in soils is 0.035 mass % as a whole. Many of plants, especially legumes, are good strontium accumulators.

The exact calculation of world strontium deposits has not been done; the evaluations show approximately 10⁹ tons.

The largest known celestine deposits are located in Mexico, Spain and Turkey as well as in Khakassia, Perm and Tula regions of Russia the obtaining of which may occupy an important place on the world market.