combination of muriatic acid and oxygen, oxymuriatic acid.

It arises in the form of gas or vapour of a yellowish-green colour, and of a pungent and disagreeable smell. It is readily absorbed by water, constituting a liquor not acid, but astringent, to the taste, yet approaching more nearly than any known fluid to the character of a universal solvent, few substances being exempt from its action, and gold, which resists so many menstrua, yielding immediately to this. It kills animals which respire it, but supports combustion even better than common air in many cases, and sets fire to various combustibles, and even metals, when plunged into it in a dry and divided

state.

It rapidly destroys vegetable colours without turning the blues to red. This property it retains in the liquid state, and combined with the alkalies or lime. It is accordingly become an instrument of the utmost value, under judicious management, to bleachers, who are able by its aid to accelerate at will that long process of oxygenation, by which the joint powers of light, air, and water, slowly and imperceptibly extracted from the fibre of linen and cotton their original dusky tinge. With the alkalies, metals, &c. it forms salts of singular properties.

Chlorine unites with oxygen in three proportions, forming, 1. Oxide of chlorine, or euchlorine.

2. Chloric acid. 3. Perchloric, or oxychloric acid.

There are also other acids derived from the mineral kingdom: as the arsenic, tungstic, molybdic, &c. which are only metals oxidized, and their properties as acids not important.

4thly, The boracic (formerly called sedative salt, from its supposed medicinal power, and which, with soda, constitutes the well-known salt borax) is perhaps more properly entitled to the name of a mineral acid. It is obtained only from borax, which is imported from the East Indies, and of the origin of which we have very little account. The method by which it is extracted is such, that it has no other form than crystals, which are composed of very fine small flakes adhering slightly together; they feel smooth and slippery, and are remarkably light. From some experiments we might conclude that some part of the salt is volatile, and some fixed; but in reality none sublimes, but what is carried off with the particles of water. If to the crystals we apply heat, the first effect is an exhalation of a little water with a quantity of salt, which sublimes in crystals of thin plates much finer and thinner than before; what remains endures any degree of heat without being volatilized. When red-hot it melts into a mass like glass; it has the same sort of transparency, and preserves it when cool: it may be again dissolved by pouring cold

water upon it, and may be afterwards crystallized. The sublimed particles returned and subjected to the same operation, put on the same vitreous appearance.

Boracic acid has but little attraction for water (i. e. for more than it always contains). It dissolves but in small quantities in cold, and not much in hot water; it crystallizes again when cool in little transparent whitish icicles. Its properties as an acid are very weak; it has no taste at first, but afterwards gives a sensation of bitterness. Its effects are still weaker upon the vegetable tinctures than even the vegetable acids: sometimes it does not affect them, and when it does, I apprehend it is from some other acid it contains. Tried upon tincture of roses and violets, it had no effect. Litmus (which is more delicate, being a preparation of one of the mosses used in dying, and which is purplish) it changed into a sensible red.

Boracic acid effervesces with a boiling hot alkaline solution, but not with metals or absorbent earths, though it may be united with them. It has a weak attraction for inflammable substances, particularly spirit of wine, the flame of which it tinges green; hence it has been thought to contain some copper, but we have no proof of this.

Lastly, the fluoric, extracted from the fluor or beautiful Derbyshire spar (which is a fluat of

lime). This acid possesses the singular property of dissolving silicious earth, and in consequence corrodes glass with such ease that it soon penetrates through a thick bottle. Hence it is applied to the elegant ornamental art of etching on glass, in the following manner.---A wax ground being laid, and the design traced with a needle, the acid (kept in a leaden bottle) is poured on in a thin stratum, and remains a few hours, more or less, as strength of impression is required. Being then washed off, and the ground cleared away by heating, &c. the design is found as well executed as on copper. It is smooth and transparent: when opake strokes are required, the piece, after preparation, is placed over the vapour arising from a mixture of pounded fluor and sulphuric acid.

The carbonic acid, formerly called fixed or fixable air, may be said to belong either to the vegetable or mineral class, since it exists in vast abundance, combined with chalk, marble, and limestone, from which it may be expelled either by heat or the stronger acids, and is also the invariable and copious product of the vinous fermentation. When set free by an acid, a strong effervescence takes place, and it is separated in the form of an invisible

It is extracted or expelled from the substance with which it is connected (lime in this case), as all the weaker acids are, by pouring on it sulphuric acid, which by a stronger attraction expels the fluoric acid, and seizes the lime.

elastic fluid, which being absorbed by water, gives it a brisk acidulous taste, and is an ingredient in many, or rather most, of the spa waters. Carbonic acid gas is about twice as heavy as common air. Hence it may be received in open vessels, unconfined by water, may be poured into others like that fluid, and will with equal certainty extinguish flame, and suffocate animals immersed in it.

The base of this acid is carbon, and from its acid character it is to be inferred that the carbon is combined with oxygen. Burning charcoal affords much more than its own weight of it. The test for its presence is clear lime-water, from which it throws down the lime in the form of a white curd, which is chalk, or carbonat of lime. It is in this manner that stalactites are formed. When water holding lime in solution oozes in drops through the roof of a grotto or cavern, where there is carbonic acid gas, it is immediately seized by the gas, which uniting with the lime forms a solid ring on the surface of the drop where it is attached to the stone roof. Another drop succeeding, another ring is produced upon the former. Thus in process of time a slender tube is formed, generally full of water, with a drop suspended from the end. The tube, however, gradually fills up, and the water then proceeding over the external surface, deposits its lime more quickly in the state of a car