still is at work. To meet both these cases ingenuity has contrived another kind of still, of which we shall hereafter give a representation. The present is an old fashioned and common still. a is the body, and b the head. The spirit or volatile product, as it rises from the material subjected to heat in a, is carried up to b, whence it is transmitted into a pipe coiled spirally in the tub, d, and called the worm, and terminating and coming out of a hole in d, at c. The tub is filled with cold water, and the volatile product in its passage through the spiral tube is condensed and flows out at c, as a fluid, into whatever is placed to receive it. As we intend shortly to enter fully into the principles and practice of distillation, we shall now say no more on the subject.

APYROUS, refractory. Bodies which resist the action of heat, or are unaltered by it, have been called Apyrous; but the term réfractory is at present most generally used,

AQUA-FORTIS, strong water, nitric acid in a weak and impure state. It is called single and double, as it is weak or strong, and when much concentrated is distinguished by the name-spirit of nitre.

AQUA MARINE, beryl. A precious stone.

AQUA REGIA, or Regis, nitromuriatic acid. A mixture of these two acids, formerly so called from its great solving powers.

AQUA VITE, low wines, ardent spirit of the first distillation. A general name for all strong drink, the

words signifying "the water of life."

AQUEOUS, watery.

AQUILA ALBA, aquila mitigata, mercurius dulcis, calomel, mild muriate of mercury. A combination of muriatic acid and mercury, employed as a medicine.

ARBOR DIANE. An amalgamation of mercury and silver, made by mixing a solution of chloride of silver in ammonia with running mercury.

ARCANUM DUPLICATUM, vitriolated tartar. A salt very early known, to which a variety of names have been given; now generally called sulphate of potash.

ARCANUM TARTARI, secret fiolated earth of tartar, essential salt of wine, regenerated tartar, diuretic salt, digestive salt of Silvius; now acetate of potash.

ARCHIL, lichen rocella, archilla, orseille. Properly speaking, archil is the name of a purplish-red dye, rocella between stones, so as to prepared by grinding the lichen bruise but not pound it, and then with lime. In a few days it bemoistening it with urine mixed comes of a purplish-red, and is then called archil, and at length of

a blue colour, and then it is called lacmus or litmus. It is a costly dye, and is seldom used by itself, as it

is very fugitive, except with marble, to which it is said to impart a durable and beautiful violet co

lour. Litmus is employed in chemistry to make a test paper, and is then improperly called tincture of turnsole. The plant from which the archil is made is a whitish lichen, and grows at the Canary and Cape de Verd Islands, and in the south of France.

ARDENT SPIRIT, alcohol, spirit of wine.

AREOMETER. An instrument for measuring the specific gravity of fluids.

ARGAL, argol, bitartrate of potash, crude tartar. A substance deposited on the inside of wine casks.

ARGENTATE OF AMMONIA, fulmiminating silver.

CHEMISTRY AS A SCIENCE.

Art. XVI.

TIN. COPPER.

BOTH these metals are so generally in use, that their appearance, and most of their properties, must be well known to our readers; we shall, therefore, only advert to such facts as they are most probably not so well acquainted with. The ores of tin have been found and worked chiefly in England, in Germany, and in South America; and they occur only in that description of mountains which geologists call primitive, from supposing them to be the most ancient parts of the world. In England, the ores of this metal are found chiefly in Cornwall, and from that part of the country our whole supply is obtained, and some sent abroad. After the ore is extracted from the mines, it is cleansed by the hand as much as possible; it is then reduced to powder in a stamping-mill. This consists of a large cistern, or other contrivance, such as large shelves Jaid on a slant, and stampers or heavy beams, armed at the ends with iron, and which are moved upwards and downwards by a water-wheel. A stream of water passes through the cistern or over the shelves; and as the ore is bruised by the stampers the water washes away all the lighter parts, and leaves the metallic part of the ore free from earthy substances. Great attention, however, is necessary in performing this part of the operation, and also in placing the vessels into which the water flows, so that the heaviest substance is left behind. When the tin ore has been thus pulverized and cleansed, it is roasted in a reverberatory furnace to drive off the sulphur, a part of which, however, is acidified, and unites with the copper and the iron to generally contained in the ore. It is then again washed, mixed with one-fifth of its weight of culm, and thrown again into a furnace for about six hours, which reduces the oxide of tin, and the metal collects at the bottom of the furnace. It is afterwards drawn off into a shallow

"

pit, where it is freed from the seoria which cover it, and is then taken out with ladles and poured into moulds. It is again exposed to a gentle heat, and the purest part which melts first is drawn off, and forms grain tin; the remainder contains a small portion of iron, copper, and arsenic, and is called common tin. What is denominated stream tin stones in Cornwall, being found in a state of powder, is melted in a somewhat different way. After being washed it is passed through wire sieves, it is then thrown with charcoal into a blast furnace, in which it is reduced to the metallic state and flows out below. It is afterwards fused in an iron pot, and purified by the addition of pieces of charcoal. When it appears bright like silver, it is judged to be pure, is drawn off into moulds, and forms good grain tin. In this manner the industry and ingenuity of man extracts from the apparent rubbish which he has brought from the bowels of the earth this useful metal.

The means of procuring tin seems to have been known from the most remote antiquity; for we find both Moses and Homer mention it, and both the coins and the weapons of the ancients were made of an alloy of tin and copper. At present it is not employed for either of these purposes. The discoveries of art have so improved the manufacture of iron and steel, that weapons are in Europe now made exclusively from them; and the greater durability of gold and silver, as well as their greater value, which renders a much less quantity of them necessary, have entirely superseded the use of tin as a coin. In its metallic state at present it is principally employed for covering sheet iron to prevent its rusting; to form plumbers' solder, speculum pewter, boilers for dyers, worms for rectifiers' stills, and many other utensils; as also for coating the inside of copper and iron vessels, and other similar purposes. What is usually called tin, however; that substance of which pots, pans, &c. are made, is,

in fact, iron coated with tin; and the process by which this is done is as follows:-The iron is rolled into very thin plates, which are thoroughly cleaned by being rubbed with sand, and by being im mersed for 24 hours in water, acidulated by muriatic acid. They are then heated in an oven to remove the scales that may be attached to them, are afterwards hammered smooth, and are again immersed in an acid solution; they are then dipped one by one in melted tin, which not only adheres to the surface but penetrates the metal completely and gives it a white colour. Tin is further employed as a material of bell-metal, bronze, brass for cannon, and a variety of other well known alloys. Pure metallic tin, of which there are two kinds, called block tintand grain tin, does not, however, differ in colour from the tin which forms. the covering of the iron sheets. We should probably here remark, as it is common to describe a particular kind of sheet tin by the name of block tin, that we do not mean this which consists of iron sheets tinned, but the metal as it is run into blocks. In this state tin is chemically described as a white metal of great brilliancy, emitting a particular smell when rubbed; not very ductile, but very malleable, as it is beat into leaves only one-thousandth part of an inch thick, and might be made thinner if wanted; it is very flexible, and produces a remarkable crackling noise; it is harder than lead and not so hard as gold; it melts at a temperature of 4420, but it requires a violent heat to cause it to evaporate. It forms alloys with most of the metals; and what is singular, when alloyed with lead, the compound is harder and and possesses more tenacity than tin, the hardest of the two. These qualities are greatest when the alloy is composed of three parts of tin and one of lead. Like most of the other metals, tin, combines readily with oxygen, and forms two oxides, one of which, the yel low oxide, is found in commerce

under the name of putty, and is used for polishing glass; the other is used in forming the opaque kind of glass called enamel.

COPPER, like tin, has been long known, and was even more employed than it in the times of the Greeks, and in still more remote antiquity. At present it is chiefly procured in Cornwall and in Anglesea in Britain, in Germany, and in Hungary. The ores from which it is obtained are sulphurets, or contain sulphur, and they are thus treated:- In Cornwall theoret broken into small pieces, is roasted, being frequently stirred, in a fur nace having a long chimney to carry off the sulphur and arsenic; it is then put into a small furnace with a little lime, and fused. Thesimpurities collect on the surface, and are raked off, from time to timeyi into oblong moulds; they form hard masses when cold, and are used as building materials; the copper flows out through a hole in the lower part of the furnace. Fresh quan- ! tities of the ore are put in from time to time, and the process isq kept up for a considerable period.b To free the metal from the arsenic and sulphur with which it is still mixed, it is heated in a furnace, and then suspended in a swellq through which a stream of waters runs. During these processes the t slag collects on the surface of theq metal, but as this contains copper, it is again thrown into the furnace with fresh ore. The copper is kept x at a low red heat for two days, and s is then repeatedly fused and casti into small moulds. Lastly, ittisb put with a small quantity of charo coal into a refining furnace and is again fused, when if it bears, the s hammer, it is fit for sale. When y the fused copper is run into moulds, the purest part of it rises to other top, and may be easily separated from the rest. In Angleseathe ore, after being reduced to a frago ments, is put into a kiln, the fluess of which terminatein a close chanmmit ber, where the sulphur obtained b from the roasting the onesiscdn-a densed. Here the roasting is kepto up for months together. In Hun-ur lux and a to nood

gary the process is nearly similar, but the copper is fused with about one-twelfth of its weight of lead; and the impurities which it separates are removed as they form. ed. To ascertain when the impurities are all removed, the workman takes out a little of the melted metal on the end of a smooth iron rod, and if the metal be pure, it falls off when the rod is dipped in cold water. When the impurities have been removed, the metal is allowed to cool, and when about to become solid, a wet broom is drawn along its surface, which converts a thin layer instantly into the solid form. This is as instantly removed and plunged into water, which gives it a fine red colour. The process is repeated till the whole is formed into thin sheets; and these are the copper sheets used in the arts. Copper is also procured from those waters which contain sulphate of copper. Pieces of iron are put into the water; they unite with the sulphuric acid, and copper is precipitated. When the iron is all dissolved, the matter deposited is raked out and fused. This process is said to have been discovered by a workman accidentally dropping a shovel in such waters, which, after laying there some time, was found covered with copper. Copper is of a peculiar reddish brown colour; it has a styptic and nauseous taste, and when the hands are rubbed over it they acquire a disagreeable smell. It is harder than silver, and is very malleable, very dactile, and possesses great tenacity. At a degree of heat consider ably below ignition, the surface of a piece of polished copper is covered with various stripes of the prismatic rays, the red of each stripe being nearest the most heat ed end of the copper.

This curious effect is probably owing to the oxidation of the metal, the oxide being thickest where the heat is greatest. A greater degree of heat oxidates it rapidly, so that thin powdery scales form on its surface, which may be easily rubbed off; at the same time the flame becomes of a beautiful bluish

green colour. Copper melts at a heat nearly the same as is requisite to melt gold or silver; and then is also of a bluish-green; by a more violent heat it may be made to boil and assume the form of vapour. If allowed to cool slowly, it crystallizes, or ranges itself in a determinate manner. It does not burn till it is exposed to a heat more than sufficient to melt it, but in a stream of oxygen gas it burns with a blue flame. It does not burn, however, so easily as iron; and is not liable, like it, to fly off by collision in fragments which catch fire; it is, if we may so speak, a much safer metal, and is therefore employed instead of iron to make hoops for powder barrels, and for various other purposes, wherever powder is manufactured or used. The poisonous nature of this metal is well known; and great care should be taken, wherever copper vessels are used for culinary purposes, to keep them thoroughly clean, and never to allow any thing to cool in them. Copper rusts, or becomes covered with a green crust, by exposure to the air; but this process goes on slowly, and the crust, which is very thin, protects the remainder of the metal from further corrosion. This crust is an oxide of the metal combined with carbonic acid gas.

The uses of copper are so numerous and familiar, that we shall not enumerate them. We have already mentioned several of the alloys, such as pinchbeck, bronze, and gun metal, of which it forms a part, and therefore we only think it necessary to add, that gun metal is generally formed of about 100 parts of copper and 10 or 12 of tin. Its oxides are employed in enamel painting, and are manufactured' into several colours.

TO OBTAIN LIQUID SULPHU. ROUS ACID.

PASS sulphurous acid gas, ob tained by the ordinary methods, first through a tube filled with pieces of chloride of calcium, (muriate of lime,) and then into a ma