LIME.

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plniric, phosphoric, nitric, and various organic acids (as oxalic, malic,citric, tartaric, and kinic): calcium occurs in combination with chlorine.In animals lime is found principally as carbonate and phosphate.

Preparation.- —For use in the arts lime is usually obtained by burningthe carbonate with coals, coak, or other fuel, in a kind of wind furnacecalled a kiln (vide Loudon’s Encycl. of Agricult. 3d ed. p. 625; andGray’s Operative Chemist.) In the Dublin, Edinburgh, and UnitedStates Pharmacopoeias , the officinal lime is the lime of commerce: but asthis contains various impurities, the London Pharmacopoeia directs limeto be prepared by exposing chalk to a very strong fire during an hour,by which the carbonic acid is expelled. White Carrara marble yieldsthe purest lime.

Properties. —Lime (commonly termed quicklime) when pure is a white,or greyish white solid, having a sp. gr. of 2'3. It has an acrid, alkalinetaste, and reacts powerfully on vegetable colours as an alkali. It is diffi-cult of fusion: but by the oxy-hydrogen flame it may be both fused andvolatilized. Exposed to the air it attracts water and carbonic acid. Ifa small portion of water be thrown on lime, part of it combines with thelime, and thereby causes the evolution of a considerable degree of heat, bywhich another portion of the water is vaporized. The lime swells up,cracks, and subsequently falls to powder: in this state it is called slackedlime (calx extinct a), or the hydrate of lime. By heat the water may beagain expelled.

Lime dissolves in water, forming lime-ioater or aqua calcis. It is pre-pared by first slacking lime and then adding more water: the proportionsemployed by the London College are half a pound of lime to three gallonsof water. The solution should be kept in stopped glass vessels with theundissolved lime, and when used the clear liquor poured off. The solu-bility of lime in water is very remarkable; cold water dissolving morethan hot. According to Mr. Phillips,

A pint of Water at 32° dissolves 13'25 grains of lime.

Ditto . . 60°. . . 11'6 ditto.

Ditto . . 212°. . . 6-7 ditto.

So that water at 32° dissolves nearly twice as much lime as water at 212°.Lime water is colourless and transparent, but by exposure to the airbecomes covered with a film of carbonate of lime, which precipitating tothe bottom of the vessel is succeeded by another. Its taste is unplea-sant and alkaline, and it has an alkaline reaction on vegetable colours.When a cold saturated solution of lime is heated, small crystals ofhydrate of lime are deposited: the same are also produced by evaporat-ing lime water in the exhausted receiver of the air-pump.

Characteristics. —Lime water is recognized by its action on turme-ric paper and on the infusion of red cabbage ; by the milkiness producedin it on the addition of carbonic acid or a soluble carbonate, and by thewhite precipitate on the addition of a solution of oxalic acid or an oxalate.Sulphuric acid affords no precipitate with lime water. Solutions of thecalcareous salts are known by the following characters:—The hydro-sulphurets, ferrocyanides, and, if the solution be dilute, the sulphates,occasion neither a precipitate nor a change of colour: the soluble car-bonates, phosphates, and oxalates, produce white precipitates. Thecalcareous salts (especially chloride of calcium) give an orange tinge tothe flame of alcohol.