separate set of a few of the most necessary re-agents in their utmost purity, and if only employed when absolutely required, a very moderate quantity will suffice. In the subjoined list we have distinguished by the word pure those substances which require particular pains to be obtained absolutely pure. Mixtures of each of the stronger acids and water in two or three different and known proportions should also be kept. N. B. The letter D implies that the dry substance should be kept, and S, that it should be in solution.

gas.

Muriate of Iron.

saturated with nitrous

Copper, sheet, wire.

Nitrate of Copper. D. and S. Silver, leaf and wire.

Nitrate of Silver.

S.

Fluate of Ammonia. S.

Succinate of Ammonia.

S.

Prussiate of Potash, pure and dry. This

should be kept in the dark.

Prussiate of Lime. S.

Catéchu. Isinglass.

Olive oil.

Linseed-oil, drying.
Oil of Turpentine.
Black flux.

Distilled water, in great plenty.

The most convenient arrangement for a laboratory where space is not wanted, seems to be that of two rooms, and a shed or apartment which can be thrown open to communicate with the air. The first may contain the books of register, of practical reference, together with the more delicate philosophical and chemical instruments, products, and preparations. The second may be provided with the work-bench, hammers, anvil, vice, and other tools, and the different furnaces; and the shed may be devoted to experiments of danger, such as arise from explosions, noxious vapours, and the breaking of vessels. It will be most convenient that these should be upon the ground floor, to secure the advantage of a ready supply of water or fuel, and other articles of heavy consumption. The first of which articles may be largely wa ted, in case of accidental combustion, as well as on common occasions. But it is likewise necessary that the place should be dry, in order that labels may be preserved, and other inconveniences avoided. This is the principal general argument, in favour of a laboratory above the ground floor.

It would carry us too far beyond the limits of our work if we were to give drawings and descriptions of the great variety of vessels, furnaces, and apparatus, which have been contrived for general and particular purposes of chemistry; and many of the culinary and domestic vessels may also be applied in experimental chemistry. We shall therefore confine ourselves to a few of the most simple and useful.

In Plate Laboratory, fig. 1, represents a retort, a, and receiver, b. These vessels are used for distillation. The subject is put into the belly of the retort, a, and exposed to heat, and the volatile products pass over into the receiver, b, which may be kept cool by the application of wet cloths, or by immersion in cold water, or otherwise, if needful. The place of junction is secured either by fitting the necks together by grinding, or by means of a lute, which see farther on. At c, in the receiver, is a neck closed by a stopper. Receivers or retorts, with this additional neck, are said to be tubulated. Fig. 2, is an alembic, of which a is the body, b the head, and c the

neck. Generally speaking, this is not a very useful instrument. In large distillations an alembic or still is used, but the condensation is effected by a spiral pipe, called the worm, which passes through a tub of cold water. In the use of the alembic, fig. 2, the beak is inserted into a receiver. When the volatile product of a body exposed to be dried, or to undergo evaporation by heat, is not required to be preserved, the process is performed in an open vessel.

The application of heat to vessels is made either by naked fire, or by the intervention of some heated substance, which is then called a bath. Chemical baths are made of sand, or of melted lead, or the fusible metal, or of brine, and very frequently of water. The evaporable liquids form a bath which cannot be heated beyond their respective boiling points; and the other baths, the most common of which is that of sand, are chiefly valuable for giving a regular heat without sudden changes.

This last purpose is effected likewise with glass vessels, by coating them with a lute.

A very great number of furnaces have been constructed for chemical and manufacturing purposes, for which we must necessarily refer to the extensive works appropriated to these objects. The operative chemist may have occasion for them of dif ferent sizes and figures. A great deal may be done with the common German stove, and with small furnaces made out of blacklead pots. But, in general, the philosophi cal chemist will be well accommodated with one good furnace, convertible to dif ferent uses; and out of many such we select that of Dr. Black, for its simplicity and efficacy, as described in his lectures.

Plate-iron is by far the best material for the outside of an experimental furnace: but, às its metal communicates heat very fast, this must be cut off by a proper lute lining. The Doctor so far succeeded in this respect, that his furnace, though only two inches thick in the middle, will not scorch paper applied to its outside, when it is melting iron within. He adopted the simplest rectilineal shapes, because workmen find great difficulty in executing curved and uncommon forms; and not one of a score of them will do it with accuracy. Indeed, those highly praised forms seemed to him of very little importance in most cases.

The body, or fire-place, is the only part of this furnace that requires description; the ash pit, with its door and registers and

grate, being constructed as in any other furnace. It will be easily understood by considering the section represented in fig. 3. The base, represented by the dotted line ABC, and the top, KLM, are oval plates of iron, the longer diameter, AC, being to the shorter as three to two nearly. The base and top are equal, so that the sides, KA, ME, are upright, the whole body forming an oval cylinder. DE F, is half of the hole in the bottom, which is occupied by the grate fixed on the top of the ash-pit. GHI is half of the mouth of the furnace, which receives a still, or a sand-pot, for distillation, with a retort. This is a little nearer to the front, K, of the top, than the grate-hole is to the front, A, of the bottom, so that the luting is thicker below than above. Near the back, M, of the furnace is a smaller hole, P, for the vent. The luting at Q and R is so formed that the cavity of the furnace does not greatly differ from a cylinder, except in so far as the vent, PO, does not communicate with it abruptly, but is gradually curved downwards, as represented in the figure, making the middle of the cavity more roomy backwards, by which means it contains a greater quantity of fuel. S is the section of the lating, which forms a sort of an arch, or bridge, contracting the entry of the vent. An iron pipe is set on at P to increase the draught of the chimney. The fuel is put into the furnace by the aperture P, and the sloping form of the cavity causes it to distribute itself pretty uniformly.

When the furnace is used for smelting, the crucible is set on a pedestal standing on the grate, and the fuel is placed round it with great ease, the mouth of the furnace being open. This is then shut up by a stopper made on purpose, or by a flat fire. tile simply laid on it.

When we would distil with a naked fire, the retort has its bulb resting on a ring which hangs on the mouth of the furnace by three hooks, and the neck of the retort lies over the front of the furnace. The space round the retort, at the mouth of the furnace is closed, as much as is necessary, by two or three pieces of tile, shaped so as nearly to fit the bulb of the retort when they are laid on the mouth of the furnace. A quantity of light ashes are now to be laid on these tiles, and heaped up so as to cover the bulb and part of the neck of the retort. Dr. Black found that this produced a very gradual diminution of the heat, as it recedes from the fuel, and is less liable to crack the

retort, by inequality of heat, than any other contrivance. Scarcely any process occurs which this furnace does not answer with great ease.

In using the furnaces most convenient for experimental chemistry, (namely, those made of plate iron) it is necessary that the iron be defended from the heat by lining or lute, as we call it, on the inside; and such lutes are necessary in other occasions in chemistry; as when we have occasion to close the joining of the vessels with one another, or to give a coating to retorts, or even to crucibles, which is sometimes done. The materials employed for these purposes have their general denomination from clay, of which some of the most useful are partly composed, though there are some that do not contain any of it. They may be divided into such as contain animal or vegetable matter, of the glutinous or adhesive kind, and such as are composed only of earthy substances. The first are used for closing the joining of vessels, when the heat we mean to apply is not to be strong, nor the vapours to be produced corrosive. The second serve for the lining of furnaces, or for closing the joinings of vessels, in operations in which the vapours are very corrosive, or in which a strong heat must be employed, which would scorch, or burn and destroy, any animal or vegetable glutinous matter.

The joinings of vessels with one another, which we have the most frequent occasion to close up by means of lutes, are those of retorts with receivers. And we may remark, in the first place, with regard to these, that there are not many operations in which it is necessary to make the joining perfectly close, except when the receiver is provided with an air-pipe. On the contrary, it is dangerous on account of the air which must be allowed to escape in some manner. Therefore we are not anxious to contrive the most close and compact. They are sufficient and better if they be moderately. so, and in some cases, when we think the lute too close we even obviate it by a pinhole. The animal and vegetable lutes, cmployed in this way, are glue and chalk mixed in thin paste, and spread on slips of paper; or gum arabic and chalk, used in the same manner; or flour and water; or a bladder; or linseed meal; or fat lute. M. Lavoisier recommends, for joinings which we desire to be air-tight, but which are not to be exposed to heat, the following: to sixteen ounces of bees-wax add

one and a half or two of turpentine, and keep it for use. When used, soften and make it tough, by warming and working between the fingers; then put it on the joint in little rolls, and make it close; and, lastly, cover it with slips of wet bladder laced with pack-thread. But, if the joint is liable to be warmed, or heated during the operation, you must take fat lute. This is made of raw pipe-clay and linseed oil, beaten together very hard, to the consis tence of a stiff adhesive paste.

Of the second kind of lutes, called the fire-lutes, a great variety have been proposed, and some of them compositions of many ingredients, but none are equal, or superior, to clay and sand; viz. sand 3, or 4, or 5, or 6, to clay 1. These are for luting vessels together, and for coatings. But in lining furnaces, Dr. Black used a double lining; first, a charcoal-lute; secondly, a fire-lute.

He found that a layer of powdered charcoal, beaten up, or kneaded, with as little water as will give its particles adhesion enough to attach itself to the metal sides of the furnace, by means of cautious beating, forms a firm stratum, which is the most imperfect conductor of heat of all that he had tried. When this layer of charcoal is defended from the action of the air by a layer of fire-lute, composed of one part of fine clay, and three or four parts of sand, carefully put on, and consolidated by gently beating it from day to day, till it no longer receives an impression from the mallet; it will last as long as any part of the furnace. Its durability will be greatly improved, without much change in its conducting power, by using, instead of pure water, water made muddy by about one-twentieth of pipe-clay. If finely powdered charcoal be kneaded with one-fifth of pipe-clay, it may be kneaded and formed into any shape, and will be so impervious to heat that a bit of it may be held in the fingers within an inch of where it is red hot. Such a composition is, therefore, very proper for the doors of furnaces, and for stopples for such apertures as must be frequently opened and shut.

Fig. 4, represents an Argand's lamp capable of being adjusted at different heights, by a sliding socket, on a stem or rod. Another similar socket is seen above, into which a ring of wire is inserted for supporting the retort, a, at any required distance above the flame. A third socket may be added, still higher upon the stem, for sup

porting another wire, which will afford the means of steadying an alembic, or any other apparatus, by a string or small flexible wire answering the same purpose. This is a very convenient method of disposing vessels for the lamp heat, upon a small or moderate scale, for distillations, sublimation, evapo-ration, drying, and the like. A small sandbath may be placed, when needful, in the wire above the flame: b is an intermediate. condensing vessel, called a quilled receiver, which conveys the condensed product into a bottle, c. The rod which supports b shows how useful these instruments are in their various applications,

The condensation of vapours after distillation, and the transmission of gases, which may arise along with them to their receptacles, has been very well and scientifically effected by the late Mr. Woulfe, in an apparatus of bottles which is distinguished by his name. The original contrivance will be easily understood by description, and instead of a drawing of that arrangement of vessels, we shall give one of the most simple, safe, and convenient of all the improvements which have since been made in it; namely, that contrived by Dr. Hamilton, and figured at the end of his "Translation of Berthollet on Dying." Suppose the retort and receiver, (fig. 1.) or any other distillatory apparatus, to have a communication from the upper parts of the receiver, a, at c by a tube leading into a bottle having three necks, and partly filled with water, beneath the surface of which the said tube, after passing this, an air-tight cork was plunged. Another of the necks of the bottle is provided with an upright open tube, also passing a cork and plunged in the water in order that air may enter in case of absorption, or the liquid may rise a little in it, in case of pressure from within. The third neck of the bottle affords a communication by means of a tube with another two necked bottle, fitted up in all respects in the same manner as the bottle communicating with e. And in this manner we may conceive a series of three or more bottles, the last of which may communicate with a pneumatic apparatus which is to receive the incondensable gas. This system of bottles and tubes is sometimes fitted together by grinding, and sometimes made secure by lutes; but in most constructions, though the advantages are very considerable, the apparatus is difficult to be put together, and easily deranged or injured.

Fig. 5, represents Dr. Hamilton's appa