Preparation

For an account of the sources whence lithia is obtained, and of its characteristic sensible and chemical properties, the reader is referred to the U.S. Dispensatory (12th ed., p. 516). The carbonate may be obtained from a mineral denominated lepidolile, which contains 3.6 per cent. of the alkali, by igniting the mineral with twice its weight of lime, forming a paste with water, treating this with dilute sulphuric acid, which forms a sulphate of lithia in solution, concentrating the solution, precipitating various earths and metallic oxides by carbonate of soda, again concentrating, and adding to the solution a very concentrated solution of carbonate of soda, which now precipitates carbonate of lithia, in consequence of the relatively slight solubility of that salt. The carbonate thus obtained is purified by dissolving it in very dilute muriatic acid, and precipitating with carbonate of ammonia. The carbonate of lithia may be obtained also from other minerals, especially amblygonite, which contains 11 per cent. of the alkali. it has been found in numerous mineral waters, as those of Carlsbad, Pyrmont, Aix-la-Chapelle, Vichy, etc.; and the alkali has been detected, by means of the spectrum analysis, in the water of the ocean.

Properties

Carbonate of lithia is in the form of a white powder, of a mild alkaline taste, and alkaline reaction. Compared with the other alkaline carbonates, it is distinguished by its comparatively slight solubility in water, of which 150 parts are required to dissolve one part of salt. It is, however, more soluble in carbonic acid water. Alcohol will not dissolve it. Except the phosphate, which is nearly insoluble, the other salts of lithia are freely soluble in water. The carbonate of lithia is a neutral salt, consisting of one eq. of lithia (lithium 1 eq. = 7, and oxygen 1 eq. = 8), and one of carbonic acid. its symbol is LO,C02, and combining number 37. it imparts a carmine-red colour to the flame of alcohol, and is distinguished from the salts of strontia, which has the same effect on burning alcohol, by dissolving with effervescence in dilute sulphuric acid. The following test at once of its quality and purity is given in the British Pharmacopoeia. Ten grains neutralized with sulphuric acid, and ignited, leave 14.86 grains of dry sulphate, which, when dissolved in water, gives no precipitate with oxalate of ammonia or lime-water.

Medical Properties and Uses

The special advantages of carbonate of lithia over the more common alkaline carbonates, which it resembles in its alkaline properties, are its low combining number, which enables it to neutralize a relatively larger quantity of acid than any other alkali, and the circumstance that lithia forms with uric acid a very soluble salt; so that the carbonate may be used to prevent the deposition of the insoluble urates, or assist in their solution when deposited. Other advantages are, according to Dr. Garrod, the decided diuretic powers of the carbonate of lithia in dilute solution, and the great facility with which it renders the urine alkaline; in both of which properties it exceeds the other alkaline carbonates. So early as 1843, attention was called by Mr. Alexander Ure, of London, to the extraordinary solvent power of lithia over uric acid; and the injection of a solution into the bladder was suggested, with the view of dissolving the uric acid calculi. it was afterwards employed by Dr. Garrod, of London, as an internal remedy in gout, in reference both to its great antacid powers, and to its influence in preventing the formation and deposition of the insoluble urates. There is, perhaps, no remedy from which equal efficiency may be expected in the removal of the deposits of urate of soda in the joints and ligamentous tissues in gouty patients, and in preventing the deposition of uric acid or insoluble urates in the kidneys, bladder, and urinary passages. The dose of the carbonate of lithia is from three to six grains, which may be taken in powder with sugar and mucilage, in watery solution when very copious dilution is indicated, or still more advantageously dissolved in carbonic acid water.