ing from a centre, and rendering the liquid solid. It is deliquescent, and its taste is intensely bitter and nauseous. When heated, it first fuses, then dries into a white mass, and at length takes fire and burns with a bright yellow flame. It is insoluble in alcohol. It has the property of rapidly dissolving the chloride of silver, when newly precipitated.

Sulphate of Soda.

(a) This salt forms regular octahedral crystals, of a prismatic or cuneiform figure; the two terminating pyramids of which are truncated near their basis.

(b) It has a more bitter taste than the preceding sulphate, and dissolves more easily in the mouth.

(c) It melts and swells upon a heated iron, in consequence of the loss of its water of crystallization, and a white powder is left, amounting to only about 36 parts from 100 of the original salt, or 43.2 according to Bucholz.

(d) By exposure to the atmosphere, it effloresces, and loses weight, and with so much quickness, that it is difficult to ascertain precisely its water of crystallization. Berzelius states it at 56 per cent, which agrees with my experience.

(e) It is very soluble in water, three parts of which, at 60° of temperature, dissolve one of the salt; and boiling water dissolves its own weight.

() Its composition is inferred from the quantity of sulphates of barytes, obtained by decomposing the solution of a known weight of this salt by any barytic salt. Bucholz, from 1000 grains of the crystallized salt ( = 432 deprived of water) obtained 693 of sulphate of barytes; and Berzelius, from 5 parts of the dry salt, precipitated 8.16 of sulphate of barytes. His experiment, to have corresponded with that of Bucholz, should have given 8.12. Assuming the acid in sulphate of barytes to be 33.5 per cent., 100 parts of dry sulphate of soda (giving 161.3 of the barytic sulphate) must consist of

Mr. Dalton's numbers are 54.8 acid + 45.2 base; Dr. Wollaston's 56 + 44; Dr. Ure's 55.55 + 44.45; and those of Berzelius 55.76 +44.24. The proportion of 56 to 44 is most consistent with the notion that this salt is constituted of 1 atom of acid + 1 of base; for 40: 32:: 56: 44. Hence its equivalent number is 72; and, adding 10 atoms of water (90), we obtain 162 for the equivalent of the crystallized salt, which must be composed of

Bisulphate of soda may be formed by adding sulphuric acid to a hot solution of sulphate of soda. Large rhomboidal crystals are formed, which are soluble in twice their weight of water at 60°; effloresce by exposure to the air; and when heated lose their excess of acid.

Seleniates of soda.-Selenic acid unites with soda in three different proportions, each of which constitutes a distinct salt, but they have no particularly interesting properties.

Hydro-cyanate of soda, like all the other salts of this class, is alkaline, and is decomposed by mere exposure to the atmosphere.

Ferro-cyanate of soda is of a yellow colour, and forms four sided prisms, terminated by dihedral summits, which effloresce in the air, and lose 374 per cent. of their weight. At 55° Fahr. they dissolve in 4 times their weight of water, but require much less boiling water, from which they separate on cooling. They are soluble in alcohol.

SECTION III.

Lithium.

THE discovery of lithia, the source of this new metal, which dates only from the commencement of 1818, is due to the

skill and sagacity of M. Arfvredson, a pupil of Berzelius. In the analysis of a mineral called Petalite (first distinguished as a new species by M. D'Andrada, who found it in the mine of Uto, in Sweden), about 3 per cent. of an alkali was obtained, which M. Arfvredson at first supposed to be soda. On more accurate examination, however, the new substance displayed properties entirely distinct from those of either soda or potassa, especially in possessing the power of neutralizing a much greater quantity of the dif ferent acids than either of those alkalis; in which respect it even surpassed magnesia. To distinguish it from the two other fixed alkalis, both of vegetable origin, it received the name of lithion, (from Ados, lapideus ;) and this term, to suit the analogy of the other alkalis, was afterwards converted into lithia or lithina.

The proportion of lithia in petalite has since been found to be 5 per cent.: and from some very pure pieces of that mineral, Vauquelin has extracted even 7 per cent. M. Arfvredson has discovered it, to the amount of 8 per cent. in triphane or spodumene, a mineral which is not so scarce as petalite; and, to the extent of 4 per cent. in crystallized lepido lite. The simplest process for obtaining it consists in fusing the mineral, finely pulverized, with three times its weight of carbonate of potassa; dissolving the fused mass in muriatic acid; evaporating to dryness; and digesting in alcohol, which takes up scarcely any thing but a compound of the new earth with muriatic acid. By evaporating a second time to dryness, and again dissolving in alcohol, the muriate of lithia is obtained pure. This muriate may be decomposed by digestion with carbonate of silver; and the solution of the carbonate, being decomposed by lime or by barytes, yields a solution of pure lithia, which may be evaporated to dryness out of contact with the air, from which it rapidly imbibes carbonic acid.

M. Arfvredson decomposed petalite by the following method. He strongly calcined, for an hour and a half, the finely powdered mineral with four times its weight of pure carbonate of barytes; digested the product with an excess of muriatic acid, which, leaving the silica undissolved, took up the baryta, alumina, &c.; precipitated the baryta by sulphuric acid, and

the alumina by carbonate of ammonia; and then, evaporating to dryness the residuary liquor, and raising the heat so as to expel the ammoniacal salts, a saline residue was left, which was dissolved by water, with the exception of a small quantity of sulphate of lime. It was a neutral salt, consisting of the new substance in combination with sulphuric acid. The sulphate was decomposed by acetate of barytes, and the acetate of lithia, thus obtained, was converted by calcination into carbonate of lithia.* For carbonate of barytes, Vauquelin and Gmelint advantageously substituted the nitrate.

Pure lithia is very soluble in water, and, like the other alkalis, has an acrid, caustic taste. Like them also, it changes vegetable blue colours to green. When heated in contact with platinum, it fuses, and then acts on the metal. That it agrees with the other alkalis in containing a metallic base, has been proved by Sir H. Davy, who applied the power of a galvanic battery to a portion of the carbonate, fused in a platinum capsule. On rendering the platinum positive, and bringing a negative wire to the surface of the fused carbonate, the alkali was decomposed with bright scintillations: but the reduced metal burned again so rapidly, that it was only observed to be of a white colour and very similar to sodium. Gmelin was not more successful in attempting to obtain the base of lithia separate, for, as fast as it was formed, it was again converted into an oxide. From analogy, this base has received the name of lithium. The proportion, in which this metal unites with oxygen, has, of course, not been determined by direct experiment; but it has been deduced by Vauquelin, from an analysis of the sulphate of lithia, and the application of the law, that the proportion between the oxygen of sulphuric acid and that of the bases which it saturates is as 3 to 1, to be as follows:

deduces the composition of lithia to be 58.05 metal + 41.95 oxygen; and if this be correct, and lithia be constituted of an atom of each of its ingredients, lithium will be represented by 11, and lithia by that number + 8 = 19.

Chloride of lithium may be obtained by evaporating the muriate of lithia to dryness, and fusing the residue. It is white and semi-transparent, extremely deliquescent, soluble in alcohol, is decomposed when strongly heated in the open air, when it parts with chlorine, absorbs oxygen, and becomes highly alkaline. It is very difficultly crystallizable, and tinges the flame of alcohol red. In all these respects, it presents striking differences from potassa and soda.

With sulphur, lithia affords a very soluble yellow compound, which is decomposed by acids, with the same phenomena as the alkaline sulphurets, and, from the abundance of the precipitate, appears to contain a large proportion of sulphur.

Sulphate of lithia crystallizes in small prisms of a shining white colour. It is more fusible and soluble than sulphate of potassa, and has a saline, not a bitter, taste. It is constituted of

Bi-sulphate of lithia is produced by adding an excess of sulphuric acid to the neutral sulphate. It is more fusible and less soluble in water than the sulphate.

Nitrate of lithia is very soluble, and by evaporation crystallizes sometimes in regular rhomboids, sometimes in needles. It is extremely fusible; and at the instant when it has cooled, it attracts moisture from the air, and becomes fluid. The muriate is not crystallizable, but a crust appears on the surface of its solution during evaporation.

Carbonate of lithia is efflorescent in the air, and is sparingly soluble, requiring about 100 times its weight of cold water. It consists of 54.46 acid + 45.54 base. The watery solution effervesces with acids; changes vegetable blue colours to green; decomposes solutions of alumine and magnesia, and of