Calx. Lond. Lime

"Take of chalk, a pound; bruise it into small pieces, and burn it in a strong fire for an hour."

Syn. Chaux vive (F.), Kalk (G.), Brand ochoslacht kalk (Sived.), Calce (I.), Calviva (S. Port.).

Lime for pharmaceutical purposes is required to be more completely burned than is usually the case with that which is obtained from the kilns; and perhaps it is with this view that the above preparation has been ordered by the London College. It may, however, be observed, that chalk does not afford lime in a state of absolute purity; as it frequently contains silex, alumina, magnesia, and marine shells; and a portion of phosphate of lime, which is not decomposed by the fire. To obtain perfectly pure lime, dissolve white marble in diluted hydrochloric acid, and to the filtered solution add solution of ammonia as long as any precipitate falls: then filter, and decompose the chloride by a solution of pure carbonate of potassa: wash the precipitate, and expose it to violent heat in a platina crucible, till it cease to lose weight. The result is pure lime, fifty six parts of which should be furnished for every 100 parts of pure white marble used.

Qualities.-Well-prepared lime is of a white colour, moderately hard, slightly sonorous, and brittle. Its specific gravity is 2.3. It is inodorous; has a hot, pungent, bitter taste; on animal matter it operates as a most powerful caustic; it changes the vegetable blues to green, and is infusible. Water poured on it is absorbed with a hissing noise, much heat is evolved, and the lime swells, falls to pieces, and is then said to be slaked; in which state having combined with a portion of the water, it is converted to a hydrate, which parts with its water at a red heat. By exposure to the air it attracts carbonic acid, and again returns to the state of a carbonate or limestone. It is an oxide of calcium1, in the proportions of 71.42 of calcium, and 28.58 of oxygen in 100 parts; or 1 equiv. of calcium =20.5 + 1 of oxygen = 8: but slaked lime, or the hydrate, consists of 75.68 of lime, and 24.32 of water2; or one equivalent of lime=28.5 + 1 of water = 9 =37.5.

Use. - Lime in this state is chiefly employed for pharmaceutical purposes, and for forming the solution.

Officinal preparations. - Liquor Calcis, L. E. D. Potassa cum Calce, L. Calcii Chloridum, L. Lig. Calcii Chloridi, L. E. D. Liquor Ammoniae, L.

Liquor Calcis. Lond. Lime-water

"Take of lime, half a pound; boiling distilled water, twelve pints. Add a little water to the lime, and when slaked add the remainder of the water, and shake them together; cover the vessel directly, and set it apart for three hours; then preserve the solution upon the undissolved lime in well-stopped glass bottles, and pour off the clear fluid when it is wanted for use."

Solutio Calcis, sive Aqua Calcis, Edin. Solution of Lime, or Lime-water.

"Take of lime, fresh burnt, half a pound. Put it into an earthen vessel, and sprinkle upon it four ounces of water, keeping the vessel covered until the lime become hot and fall into powder; then pour on it twelve pounds of water, and mix the lime with the water by agitation. After the lime shall have subsided, repeat the agitation; and let this be done about ten times, the vessel being kept shut, that the free access of the air may be prevented. Finally, let the water be filtered through paper, interposing glass rods between the paper and the funnel, that the water may pass through as quickly as possible. It is to be preserved in very well-stopped bottles."

Aqua Calcis, Dub. Lime-water.

"Take of fresh-burnt lime and boiling water, each one part. Put the lime into an earthen vessel, and sprinkle the water upon it, keeping the vessel shut until it become hot and fall into powder; then pour upon it thirty parts of cold water. The vessel being again shut, let the mixture be frequently shaken for twenty-four hours : and then, after the lime has subsided, pour off the limpid fluid, and preserve it in well-stopped bottles."

1 This metal has the colour and appearance of silver, is solid, four times heavier than water, absorbs oxygen, and burns brilliantly in the open air, and by being oxidised is converted into quick lime. Phil. Trans. 1808.

2 Phillips's Trans, of Pharm. p. 71.

Syn. Eau de Chaux (F.), Kalkwasser (G.), Kalkwater (Dutch), Aqua di Calce(I.).

Of these formulae, that of the London College is to be preferred; as by keeping the solution upon the lime it is always in a completely saturated state, and the supernatant fluid is generally sufficiently clear to allow it to be decanted off without filtration. It is, however, advisable, in making the solution, first to slake the lime with a small portion of water, before the whole quantity be added; as by this it is prevented from running into a paste, which confines the action of the water. The direction of the Dublin College to use the water for slaking the lime in a boiling state is superfluous. Cold water acts more powerfully on lime than hot water. From Mr. Phillips's experiments, it appears that one pint of water at 212° dissolves 6.7 grains of lime; the same quantity of water at 60° dissolves 11.6 grains; and at 32° the quantity dissolved is increased to 13.25 grains.1 By heating cold, saturated lime-water, a crystalline deposition of hydrate of lime was thrown down.

Qualities. - Lime-water is inodorous; has a strong, styptic, acrid taste; is limpid and colourless; and changes to green the vegetable blue and red colours. It unites with oil, forming an imperfect soap. When exposed to the air, it attracts carbonic acid, which, combining with part of the lime held in solution, forms on its surface a pellicle of carbonate of lime, which thickens, cracks, and sinks to the bottom of the vessel, leaving its place to be supplied by another pellicle; and thus, by successive formations, the whole of the lime is abstracted from the water. Hence the necessity of preserving the solution in well-closed bottles; and when it is filtered, in small bottles containing such a quantity only as can be used at once. It is decomposed by the acids and sulphur, the alkaline carbonates, phosphates, borates, tartrates, and citrates; the infusions of orange peel, columba, cinchona, rhubarb, and senna, which are consequently incompatible in formulae with it.

Medical properties and uses. - Lime-water is tonic, antacid, anthelmintic, and externally detergent. It proves very useful in dyspepsia attended with much acidity, by neutralising the acid, and dissolving the sorded mucus with which the stomach is often loaded in this disease; it has also been found efficacious in diarrhoea, diabetes, and leucorrhoea. It destroys intestinal worms, and dissolves the mucus which forms their nidus;

1 Translation of the Pharmacopaeia, p. 72.

and, for the same reason, proves serviceable in slimy bowels. Its internal use, however, should be occasionally suspended for a few days, as its long-continued action on the stomach is apt to prove hurtful. Externally it is applied as a lotion to foul and cancerous ulcers, tinea capitis, and scabies, but with little advantage.

The dose is from f ij. to O ss., alone or diluted with milk.

Officinal Preparations. - Oleum Lini cum Calce, E. D. Aqua Calcis Oomposita, D.