Lithium, the metallic base of lithia, does not exist native, but can be obtained from various minerals, as lepidolite, triphylline, etc, and derives its name from λίθζ a stone, as it was supposed to exist only in the mineral kingdom. It is the lightest solid body known, floats on water and on naphtha, and has a density of 0.5936, it has a very small atomic or equivalent weight, only seven on the hydrogen scale. Its oxide (LO), which is a powerful base, forms crystallizable salts with the acids. The urate of lithia is much more soluble than that of potash or soda. Lithiae Carbonas. Carbonate of Lithia.

Prop. & Comp. Carbonate of lithia occurs in a white powder or in minute crystalline grains. It has an alkaline reaction, and is soluble in 100 parts of cold water; its solubility is increased by the presence of carbonic acid in the liquid; not soluble in alcohol. When treated with hydrochloric acid it dissolves with effervescence; the solution when evaporated to dryness leaves a residue of chloride of lithium. If this be dissolved in water, and a solution of phosphate of soda added, a precipitate of phosphate of lithia is formed (3 LO, Po5). The composition of carbonate of lithia is (LO, CO,).

Ten grains neutralized with sulphuric acid, and afterwards heated to redness, should leave 14.86 grains of dry sulphate of lithia; this when re-dissolved in distilled water yields no precipitate with oxalate of ammonia or solution of lime, showing the absence of lime or magnesia.

Therapeutics. From the small amount of lithia sufficient to form a salt with uric acid, and the much greater solubility of the salt, it follows that unless other circumstances interfere with their administration, the lithia salts must be valuable remedies when it is desirable to keep uric acid in solution during its transit through the urinary organs or prevent its deposition in the structures of the body. The carbonate of lithia acts as a diuretic, and in the same dose has a more powerful influence in rendering the urine alkaline than the corresponding salt of soda or potash. It may be given with great advantage in certain states of the system in which urate of soda is liable to be deposited in the tissues, as in gout, etc.

Dose. Of the carbonate, 3 gr. to 6 gr. The carbonate may be given in aerated water; free dilution aids its diuretic action.