Calx Pharm. Lond. Calx viva Pharm. Edinb. Quicklime: an acrimonious, friable substance; dissolving, very readily, in the nitrous, marine, and vegetable acids; uniting with the vitriolic acid into an indissoluble and nearly insipid concrete; producing heat on the affusion of water, partly dissolving in the water, and impregnating it with a strong taste.

Quicklime is prepared, about London, chiefly from chalk; in other parts of the kingdom, from different sorts of stones called, from their use, limestones; by calcining them, in kilns made for this purpose, with a strong fire. All the native mineral earths and stones, that dissolve in acids, and all the sea shells that have been tried, are reduced by fire into quicklime; and suffer, in the calcination, a great diminution of their weight. If the lime be exposed long to the at-mosphere, it falls by degrees into powder, in-creases in weight, loses of its acrimony, and at last becomes similar in quality to what the earth was before calcination: it retains its acrimony much longer in a moist than a dry state.

The earths and stones, from which quicklime is produced, contain a large quantity of air, which in calcination is expelled: hence strong quicklime raises no effervescence, or emits no air-bubbles (which the crude earths do in great abundance) during its dissolution in acids. A theory, which now begins to prevail, considers the proper calcareous matter as a substance, which is in its pure state quicklime; which, by the simple Coalition of air*(a) with it, loses its acrimony, solubility in water, and other distin-guishing characters; and which, on the bare separation of this incorporated air, proves quicklime again(b). Thus much appears demon-strated, that either the qualities of the calcareous matter are affected by the air itself imbibed or expelled, or that both (in all the experiments hitherto known) are equally affected by some other cause: in either case, the discovery is valuable in regard to practical utility; the calcareous earths and stones becoming quicklime by all those means by which air is expelled from them, whether calcination by fire, or solution in acids and precipitation with substances void of air; and quicklime losing its qualities by all those means by which air is introduced, whether direct ex-posure to the atmosphere, or commixture with certain other bodies from which it instantane-ously absorbs the aereal matter.

Quicklime is employed for increasing the activity of alkaline salts: if water, strongly impregnated with the lime, be gradually added to a solution of fixt alkali, the calcareous matter separates and subsides, satiated with air, and no longer acrid or dissoluble in water; the alkali at the same time losing its air, so as to make no effervescence with acids, and proving in this state much more acrid than at first. Quicklime is sometimes used also in external applications as a depilatory; and has been sometimes made into an unguent with honey for rheumatic and other obstinate fixt pains of the joints or limbs; this unguent is greatly commended by Fuller, who observes that it is almost caustic.

* (a) Not atmospherical air, but the species of air termed fixed or fixable.

(b) See Dr. Black's Experiments on Magnefia, in the Edinburgh essays physical and literary, vol. ii. art. 8. and Dr. Macbride's experimental essays.

Solutions of the calcareous matter in water are given internally with safety, and in many cases with advantage. For this purpose, a gallon and a half of water is poured by degrees upon half a pound of fresh burnt quicklime, the vessel shaken when the ebullition ceases, and then set by till the undissolved lime has settled; after which, the liquor is poured off, and passed through a filter. In the last Edinburgh dispensatory, half a pound of lime is directed to be sprinkled with four ounces of water in a close vessel, and when it is fallen to powder, twelve pounds more of water are to be added, and the whole agitated about ten times, keeping the vessel still close; and the liquor then filtered. Only a small portion of the lime is dissolved by the water, and the remainder gives a strong impregnation to large quantities of fresh water, though not so strong as to the first; great part remaining at last undissolved: this residuum, calcined again, becomes quicklime as before: and by repetitions of this pro-cess nearly the whole may be dissolved.

The solution has a strong, styptic kind of tafte. It changes the juices of blue flowers to a green colour; precipitates metallic bodies dissolved in acids; tinges silver of a coppery hue; and turns red wine to a dark colour: by these properties, the strength of its impregnation with the calcareous matter may be in some measure estimated. The specific gravity of the liquor is increased by the lime, in a much greater ratio than the small quantity taken up can effect by the apposition of its own weight(a); on account, perhaps, of the water being deprived of its air. In vessels quite filled with the lime-water, and exactly closed, it may be kept unchanged for many months: in open vessels, the calcareous matter soon separates from the aqueous fluid, and concretes upon the surface into a crust, insipid and indissoluble as the earth in its natural state, and again convertible into quicklime by a repetition of the calcination. As most kinds of liquids, and many other bodies, are impregnated, more or less, with the sub-stance which lime greedily imbibes, and which renders it indissoluble; lime-water suffers a reparation of part of its lime in most mixtures, and probably also in the act of its dissolving bodies: hence, when this liquor is employed as a menstruum, it is advisable to add some quicklime in substance, in order to continue the impregnation of the water with the lime.

Aqua calcis Ph. Lond.

Aqua calcis Ph. Ed.

Lime-water dissolves, by the assistance of heat, mineral sulphur, vegetable oils and resins, and animal fats: it extracts, in the cold, the virtues of sundry resinous and oily vegetables, and dissolves thick phlegm or mucous matters, and the curd of milk; with which last it forms a white liquid, nearly similar in its appearance to milk in its natural state. It has lately been found to dissolve also the human calculus, particularly the lime-water prepared from calcined oyster-shells, which proves a more active men-struum for this concrete (and possibly for other substances also) than that made from the stone limes; the dissolving power of the oyster-shell lime-water seeming, from Dr. Whytt's experiments, to be more than double to that of the stone lime-waters(a). Taken internally, in considerable quantity, it impregnates the urine in some degree with its lithontriptic power, and in sundry calculous cases has happily given relief.

(a) Whytt, Edinb. ess. & obs. phys. & lit. vol. i art. xiii. p. 383.

Lime-water, drank to the quantity of a quarter of a pint three or four times a day, has been found serviceable in scrophulous complaints, fluxes, seminal weaknesses, and other disorders proceeding from an impurity of the fluids, or laxity and debility of the solids. It generally promotes urine; oftentimes the cuti-cular discharge; and where the stomach is op-pressed with viscid phlegm, expectoration. It for the moil part binds the belly, and some-times occasions a troublesome costiveness, unless this effect be occasionally provided against by the interposition of proper laxatives. It answers belt in cold, sluggish, phlegmatic, and corpulent habits, and is to be used more cautiously in hot bilious dispositions, and where the patient is greatly emaciated, or the appetite weak, and at the time of any critical or periodical evacuation.

It is customary to impregnate lime-water with different materials, partly for rendering it more acceptable to the palate and stomach, and partly for improving its medicinal efficacy against cutaneous defedations. These infusions are taken in the same quantities as the simple lime-water, by themselves, or with the addition of milk.

(a) Edinb. medical essays, vol. v. art. 69. See on this subject his Treatise on the virtues of lime-water.