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L. STRONTIUM,

Strontium is the metallic base of the earth strontia, or strontites, and may be obtained from the carbonate by the same process as is employed for obtaining calcium. It may be produced, likewise, by passing the vapour of potassium over strontites heated to redness. The metal obtained is heavy, white like silver, and fusible with difficulty. When exposed to the air, or thrown into water, it is quickly oxidated, and converted into strontites, which is a protoxide of the metal.

Its combining weight has been calculated by Berzelius at 43.85, by Dr Thomson at 52.07.

Like lime, it combines with oxygen in two proportions. The protoxide is the earth strontites, which occurs in a few rare minerals, of which one is the green carbonate found in the lead-mine of Strontian, in Scotland. The oxide is nearly, if not altogether, infusible, and is acrid in taste, and strongly alkaline. It has a great affinity for water, though it is little soluble in that liquid. When exposed to the air, it attracts water, with which it combines in a definite ratio, swelling and crumbling into powder, like lime under the same circumstances, and evolving much heat. This substance is therefore altogether similar in its characters to lime, and the metallic bases of both must be regarded as in the same class of bodies.

LI. BARIUM.

Barium is derived from the protoxide barytes. It has as yet been obtained only in minute quantity, by the powerful action of galvanism. It is a dark-gray substance, less bright than cast-iron. It fuses at a heat below redness, and produces a vapour which acts strongly upon glass. It has a strong affinity for oxygen, attracting it from the air, and from water. When heated, it burns with a deep red light. Its density has not been determined. Its combining weight, as calculated by Berzelius, is 68.66.

Like calcium and strontium, it combines in two proportions with oxygen. The protoxide occurs in a few minerals chiefly found in lead-mines. It is a grayish-white powder, of specific gravity about 4. It has a caustic alkaline taste, converts vegetable blues to green, and neutralizes the strongest acids. It is insoluble in alcohol, and fuses only at a very high temperature. It has a strong affinity for water, but it is less soluble in that liquid than soda and potassa. If exposed to the air, it immediately attracts moisture, swells out with evolution of heat, and crumbling into powder, in the manner of quicklime and barytes, after which it gradually attracts carbonic acid, and loses its acid properties, in the same manner as quicklime and strontites, under the same conditions. If, in place of this slow absorption of water, the liquid be added in quantity, the barytes in like manner combines with it, and swells and crumbles down, with the evolution of so great a heat as to become luminous. In either case it combines with water in the proportion of 1 equivalent, and forms a hydrate. This hydrate is a white substance, fusible at a red heat, and capable of sustaining the highest temperature of a forge without parting with its water. It has the caustic and alkaline properties of the anhydrous protoxide. These characters indicate, beyond all question, the close relation between calcium, strontium, barium, and their compounds.

LII. LITHIUM.

This metal is derived from the alkaline earth, which is an oxide of the metal, found in mica, and some rare minerals. Davy, by means of a voltaic battery, extracted from this alkali, the metallic basis, which he termed lithium. It is a white-coloured metal, resembling sodium and potassium, but possessing so powerful an affinity for oxygen, and attracting it with such rapidity, that it has scarcely admitted of examination in its separate state. Its combining weight was calculated by Berzelius at 6.44; by Arfwedson at 10.247. It is probable that neither is correct, and that the combining weight of lithium approaches nearer to that of the alkalies, which it resembles in all its other characters.

Its only known compound with oxygen is lithia. This substance has been hitherto derived from a few minerals, as petalite, spodumene, the tourmaline, and some varieties of mica ; and it has been found in the mineral waters of Carlstadt in Bohemia. It is best prepared from petalite and spodumene, in which two minerals it exists combined with silica and alumina. It has a white colour, and a taste acrid and caustic in a high degree. It forms with water a hydrate, like soda and potassa. At a red heat it melts, forming a transparent liquid. When exposed to the air it attracts carbonic acid, and is converted into a carbonate. Its solubility in water is less than that of soda and potassa, and when exposed to the air, it does not like the latter become deliquescent. It is scarcely soluble in alcohol, and if that substance is added to an aqueous solution, the lithia, after an interval of some hours, is precipitated. When heated in a platinum crucible, it acts with force upon the metal.

LIII. SODIUM.

Sodium, the metallic basis of the alkali, soda, was obtained by Davy only a few days after his memorable discovery of the composition of potassa. It was obtained by the action of a powerful voltaic battery on hydrate of soda, by means similar to those employed for obtaining the same class of metals. But the metal may now be obtained in any quantity by heat and chemical affinities alone, by mixing the carbonate, but better and more safely, the hydrate, with charcoal and iron-filings, and exposing the mixture to a powerful heat.

The metal is of a bright silver-white colour, and is lighter than water, having at 59° F. a specific gravity of 0.972. At the temperature of 32°, it is malleable and soft, and it becomes gradually softer by the increase of heat, and at 184° it fuses, becoming entirely liquid. At a red heat, and in the absence of atmospheric air, it rises in vapour unchanged. It is oxidated when exposed to the air at common temperatures, but very slowly if the air be dry. When heated, however, in the air, it is rapidly oxidated, and when the heat is increased, it takes fire and burns with a bright yellow flame. When thrown into water, it is in like manner rapidly oxidated, hydrogen gas being evolved. It rolls about upon the surface with a hissing noise ; but if fixed to a spot, by rendering the water viscid, it takes fire; and when a few drops only of water are thrown upon it, it evolves so much heat as to be kindled.

Its combining weight has been estimated at 23.31. It combines with oxygen in at least two proportions, with chlorine, sulphur, and other bodies.

The protoxide forms the alkali soda. This substance

K

exists in vast abundance in the mineral kingdom, in animals, in marine plants, and in many vegetable tribes which grow on land. It may be obtained either in the anhydrous state or as a hydrate. In the former state it is a gray-coloured substance, exceedingly difficult of fusion. When it combines with an equivalent of water, it becomes white in colour, and more fusible than before. It possesses all the characters termed alkaline, in the first degree.

Chloride of sodium, forming the well-known substance common salt, is produced by the combustion of sodium in chlorine, in which the metal takes fire spontaneously, burning with bright sparks. It is produced, likewise, by heating sodium in hydrochloric acid gas, or by passing a current of chlorine gas over it heated to redness, or by dissolving soda in hydrochloric acid. But it is from sea-water that it is obtained in the largest quantity, by simple evaporation. It exists, likewise, in many saline springs ; and is found in vast beds, chiefly in the new red sandstone formation, but occasionally, also, in the older deposites. It is of a white colour, and has a grateful saline taste. It fuses at a red heat without decomposition, and becomes a transparent mass on cooling. Its solubility in water is little affected by differences of temperature. It deliquesces slightly in a moist atmosphere, but suffers no change when the air is dry.

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