The crystals contain about 60 per cent. of water. This salt is usually obtained for pharmaceutical purposes by saturating the impure phosphoric acid, obtained from calcined bones by sulphuric acid, (See Phosphorus) with carbonate of soda: the liquor is filtered, evaporated, and set aside to crystallize. It was introduced into pharmacy by Dr. Pearson; it is the sal perlatum of some old writers.

When heated, phosphate of soda fuses and boils up, and having lost its water of crystallization, it runs into a clear glass, which becomes opaque on cooling. If a globule be heated before the blow-pipe it assumes the dodecaedral figure as it cools.

597. Treated with sulphuric acid, phosphate of soda is only partly decomposed, a bi-phosphate of Soda being formed, which is more soluble than, and not so easily crystallizable as the phosphate.

598. Ammonio-phosphate of Soda exists in human urine, whence it was procured by the early chemists under the names of microcosmic and fusible salt. When exposed to heat the ammonia is expelled, and a biphospate of soda remains: it appears to consist of two proportionals of phosphoric acid = 56; one of soda = 32, and one of ammonia = 17. -FOURCROY, Annales de Chimie, vii. 183.

599. Carbonate of Soda is chiefly obtained by the combustion of marine plants, the ashes of which afford, by lixiviation, the impure alcali called soda. Two kinds of rough soda occur in the market; barilla, and kelp; besides which, some native carbonate of soda is also imported. Barilla is the semifused ash of the salsola soda, which is largely cultivated upon the Mediterranean shore of Spain, in the vicinity of Alicant. Kelp consists of the ashes of sea weeds, which are collected upon many of the rocky coasts of Britain, and burned in kilns, or merely in excavations made in the ground and surrounded by stones. It seldom contains more than 5 per cent. of carbonated alcali, and about 24 tons of sea weed are required to produce one ton of kelp. The best produce is from the hardest fuci, such as the serratus, digitatus, nodosus, and vesiculosus. (MAC CULLOCH'S Western Islands, Vol. i., p. 122.) The rough alcali is contaminated by common salt, and other impurities, from which it may be separated by solution in a small portion of water, filtrating the solution, and evaporating it at a low heat: the common salt may be skimmed off as its crystals form upon the surface.

600. The primitive crystalline form of carbonate of soda is an octoëdron, with a rhombic base; the solid angles of the summit are always wanting, being replaced by planes parallel to the base, and thus presenting a solid with 10 surfaces. It is soluble in twice its weight of water at 60°. Its taste is strongly alcaline, and it greens vegetable blues.

It consists of

32 soda

22 carbonic acid.

54

Its crystals contain seven proportionals of water = 63, which may be expelled by heat. They effloresce by exposure to air. This salt is the Soda-Subcarbonas of the Pharmacopeia.

In the analysis of barilla and kelp, to ascertain the relative proportion of soda, it may be useful to know that 100 parts of dilute nitric

1

acid, specific gravity 1.36, will saturate 50 parts of dry carbonate of soda, which are equivalent to about 29 of pure soda.

601. Bi-carbonate of Soda is formed by passing carbonic acid through the solution of the subcarbonate. By evaporation a crystalline mass is obtained. This salt consists of

32 soda

44 carbonic acid

76

1

The bi-carbonate of soda has a very slightly alcaline taste, and it is much less soluble in water than the sub-carbonate.

602. This salt, as well as the bi-carbonate of potassa, may be obtained by treating their respective carbonates with carbonate of ammonia; pure ammonia is evolved and bi-carbonates are formed.-See London Pharmacopaia.

In the manufacture of this bi-carbonate for the purpose of commerce, 160 lbs. of carbonate may be dissolved in 13 gallons of water, and carbonic acid thrown into the solution in a proper apparatus. The bi-carbonate falls as it forms to the amount of about 50 lbs., and being separated from the solution may be conveniently dried by pressure in an hydraulic press, and subsequent exposure to heat not exceeding 100°. A fresh portion of carbonate is dissolved in the mother liquor, and the operation repeated as before.

603. A mixture of the carbonates of soda occurs native in great abundance in Africa, in the province of Gahena, near Fezzan. The natives call it Trona. It has been analyzed by Mr. R. Phillips, who considers it as a compound intermediate between the carbonate and bicarbonate, composed of 3 proportionals of acid and 2 of base, or 1 soda +11 acid; hence he terms it a sesqui-carbonate of Soda. Quar'erly Journal, vii., p. 298.

A very productive soda-lake also exists in South America in Maraaybo, one of the provinces of Venezuela. Quarterly Journal, i. p. 188.

604. Subborate of Soda-Borax. This salt, which has been very long known, is imported from India in an impure state, under the name Tincal, which, when purified, is called Borax. It crystallizes in irregular hexaedral prisms, slightly efflorescent. Its taste is alcaline and styptic. It is soluble in 20 parts of water at 60°, and in six parts of boiling water. When heated it loses water of crystallization, and becomes a porous friable mass, called calcined borax. It consists, according to Bergman, of

34 acid

17 soda

49 water

100

Sulphuric acid decomposes this salt, producing sulphate of soda and boracic acid. (Chap. IV. § vi.) It has a place in the Pharmacopria, and is sometimes used as a flux.

605. The salts of sodium are soluble in water. They are not preThe crystals cont ly obtained for pha phoric acid, obt Phosphorus) with and set aside to Pearson; it is t When heater

its water of c

opaque on cou sumes the do 597. Tre

decompose ble than, a 598. A.

was procu fusible sa phospate phospho

-Fors

599.

rine

call

and

B

..

eral, called petalite, M. Ar fwedson of an alcaline substance, which was at finding that it required for its Deutrali- of acid than soda, he was led to doubt and the further prosecution of his inquiit possessed peculiar properties spodumene, also affords the same substance, educed from its lapideous original, has been detected in a few other minerals.

The

de of obtaining lithia from the above substaneral to a fine powder, and fuse it with about half Assolve the fused mass in muriatic acid, filter, ress; digest the dry mass in alcohol; the only ble in that liquid, is the muriate of lithia, which second solution and evaporation is obtained pure. d by digesting carbonate of silver in its aqueous acarbonate of lithia is formed, decomposible by the other alcaline carbonates.

is submitted to the action of the Voltaic pile, it is e same phænomena as potassa and soda; a brilliant combustible metallic substance is separated, which , the term lithia being applied to its oxide. es of this metal have not hitherto been investigated, the difficulty of procuring any quantity of its oxide. a is very soluble in water, and its solution tastes acrid ixed alcalis. It acts powerfully on vegetable blues, en to green. It is very sparingly soluble in alcohol. ments upon the composition of lithia are yet wanting. from the composition of the sulphate, as analyzed by would appear to contain about 55.2 lithium + 44.8 oxy

wade of Lithium, obtained by evaporating the muriate to fusing it, is a white semitransparent substance. It evipiers from the chlorides of potassium and sodium, in being ex*quescent; in being soluble in alcohol; in being decompos

lithia

2+44.8=100:: 8 (atom oxygen): 17.8 (the atom lithia which agrees with sion of the sulphate.

when strongly heated in the open air, when it loses chlorine, absorbs zen, and becomes highly alcaline; in being very difficultly crystalCable; and in tinging the flame of alcohol of a red colour.

11. Iodide of Lithium. -The action of iodine, of hydriodic acid, and of iodic acid, on lithia has not been examined.

612. Nitrate of Lithia is a very soluble deliquescent salt, fusible and decomposed by heat; its taste is cooling; it crystallizes in rhomboids. 613. Sulphuret of Lithium. -The action of sulphur on lithium and lithia appears analogous to its action on potassium and potassa, but the compounds have not been precisely examined.

614. Sulphate of Lithia crystallizes in small rectangular prisms, perfectly white, and possessed of much lustre. Their taste is saline, and their solubility intermediate between that of sulphate of potassa and sulphate of soda. The crystals contain no water, and fuse at a heat below redness. Their solution occasions no change in solution of platinum, nor in tartaric acid. They consist of

615. Phosphate of Lithia has been examined by Dr. Gmelin: it may be obtained by adding phosphoric acid to sulphate of lithia; no precipitate is at first formed, but on adding excess of ammonia, an insoluble phosphate of lithia falls. This property enables us to separate lithia from potassa and soda. The phosphate of lithia may be decomposed by dissolving it in acetic acid and adding acetate of lead: acetate of lithia remains in solution.

616. Carbonate of Lithia. - When a strong solution of carbonate of potassa is added to sulphate of lithia, a white precipitate of carbonate of lithia is formed. It requires about 100 parts of water at 60° for its solution. It is fusible, alcaline, effervesces with acids, and absorbs carbonic acid from the air. Lithia and its carbonate, when heated upon platinum, act upon that metal.

617. If we assume from Vauquelin's corrected analysis of the sulphate, that lithia contains 45 per cent. of oxygen and 55 of lithium, and that it is a protoxide, then 45:55::8: 9.77. So that the number 9.8 might be assumed as the representative number of lithium ; and oxide of lithium, or lithia, would contain

N. B. It is probable that 10 is the number for lithium instead of

9.8, for 10 is a multiple of 0.125 (the atom hydrogen) which is not the

SECTION IV. Calcium.

618. WHEN lime is electrized negatively in contact with mercury, an amalgam is obtained, which, by distillation, affords a white metal. It has been called calcium, and when exposed to air, and gently heated, it burns and produces the oxide of calcium, or lime.

Lime appears to consist of 20 parts of this metallic base united to 8 parts of oxygen, so that its representative number will be = 28.

619. The combinations of lime are very abundant natural products, and of these the native carbonate which, more or less pure, constitutes the different kinds of marble, chalk, and limestone, and which is also the leading hardening principle of shell, coral, &c., may be considered as the most important.

Lime may be obtained in a state of considerable purity by exposing powdered white marble to a white heat, which expels the carbonic acid. To obtain absolutely pure lime, white marble may be dissolved in dilute muriatic acid, a little ammonia added to the solution, and filtered: carbonate of ammonia is then added, and the precipitate dried, washed, and exposed to a white heat. Its colour is light grey; it is acrid and caustic and converts vegetable blues to green; its specific gravity is 2.3; it is very difficult of fusion, but remarkably promotes the fusion of most other earthy bodies, and is therefore used in several metallurgic processes as a cheap and powerful flux. When quite pure it can only be fused in very minute particles by the oxygen blow-pipe, or by the Voltaic flame. It is an essential ingredient in mortar and other cements used in building. Exposed to air it becomes white by the absorption of water and a little carbonic acid.

620. When a small quantity of water is poured upon lime, there is a great rise of temperature resulting from the solidification of a portion of the water, and a white powder is obtained, called slacked lime, which is a hydrate, and which appears to consist of one proportional of water = 9+ one proportional of lime = 28 = 37 hydrate.

Lime may be obtained in a crystalline form by placing lime water under the receiver of an air-pump, containing another vessel of sulphuric acid. The water is thus slowly evaporated, and imperfect six-sided crystals of hydrate of lime are formed.-GAY-LUSSAC, Annales de Chimit et Phys., i. 334.

At the temperature of 60°, 750 parts of water are required for the solution of one part of lime.

621. Lime-water is limpid and colourless; its taste is nauseous, acrid, and alcaline, and it converts vegetable blues to green. It is usually prepared by pouring warm water upon powdered lime, and allowing the mixture to cool in a close vessel: the clear part is then decanted from the remaining undissolved portion of lime. When lime-water 15 exposed to the air, a pellicle of carbonate of lime forms upon its surface, which, if broken, is succeeded by others, until the whole of the lime is thus separated in the form of an insoluble carbonate. Limewater is used in medicine as an antacid.

622. When oxygen is passed over heated lime, it is absorbed, and a portion of peroxide of calcium is formed. A hydrated peroxide of cal