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grate, being constructed as in any other retort, by inequality of heat, than any other furnace. It will be easily understood by contrivance. Scarcely any process occurs considering the section represented in fig. S. which this furnace does not answer with

The base, represented by the dotted line great ease. ABC, and the top, KLM, are oval plates In using the furnaces most convenient of iron, the longer diameter, AC, being to for experimental chemistry, (namely, those the shorter as threc to two nearly. The made of plate iron) it is necessary that the base and top are equal, so that the sides, iron be defended from the heat by lining or KA, MC, are upright, the whole body lute, as we call it, on the inside ; and forming an oval cylinder. DEF, is half of such lutes are necessary in other occasions the hole in the bottom, which is occupied in chemistry; as when we have occasion to by the grate fixed on the top of the ash-pit. close the joining of the vessels with one anGHI is half of the month of the furnace, other, or to give a coating to retorts, or even which receives a still, or a sand-pot, for dis- to crucibles, which is sometimes done. The tillation, with a retort. This is a little materials employed for these purposes have Dearer to the front, K, of the top, than the their general denomination from clay, of grate-hole is to the front, A, of the bottom, which some of the most useful are partly so that the luting is thicker below than composed, though there are some that do above. Near the back, M, of the furnace pot contain any of it. They may be divided is a smaller hole, P, for the vent. The into such as contain animal or vegetable luting at Q and R is so formed that the matter, of the glutinous or adhesive kind, cavity of the furnace does not greatly differ and such as are composed only of earthy from a cylinder, except in so far as the substances. The first are used for closing vent, PO, does not communicate with it the joining of vessels, when the heat we abruptly, but is gradually curved down- mean to apply is not to be strong, nor the wards, as represented in the figure, making vapours to be produced corrosive. The the middle of the cavity more roomy back second serve for the lining of furnaces, or wards, by which means it contains a greater for closing the joinings of vessels, in operaquantity of fuel. S is the section of the tions in which the vapours are very corroluting, which forms a sort of an arch, or sive, or in which a strong heat must be embridge, contracting the entry of the vent. ployed, which would scorch, or burn and An iron pipe is set on at P to increase the destroy, any animal or vegetable glutinous draught of the chimney. The fuel is put matter. into the furnace by the aperture P, and the The joinings of vessels with one another, sloping form of the cavity causes it to dism which we have the most frequent occasion tribute itself pretty upiformly.

to close up by means of lutes, are those of When the furnace is used for smelting, retorts with receivers. And we may rethe crucible is set on a pedestal standing mark, in the first place, with regard to on the grate, and the fuel is placed round it these, that there are not many operations in with great ease, the mouth of the furnace which it is necessary to make the joining being open. This is then shut up by a perfectly close, except when the receiver is stopper made on purpose, or by a flat fire provided with an air-pipe. On the contrary, tile simply laid on it.

it is dangerons on account of the air which When we would distil with a naked fire, must be allowed to escape in some manner. the retort has its bulb resting on a ring Therefore we are not anxious to contrive which hangs on the mouth of the furnace by the most close and compact. They are three hooks, and the neck of the retort lies sufficient and better if they be moderately over the front of the furnace. The space so, and in some cases, when we think the round the retort, at the mouth of the fur- Jute too close we even obviate it by a pinnace is closed, as much as is necessary, by hole. The animal and vegetable lutes, emtwo or three pieces of tile, shaped so as ployed in this way, are glue and chalk mixnearly to fit the bulb of the retort when ed in thin paste, and spread on slips of they are laid on the mouth of the furnace. paper; or gum arabic and chalk, used in A quantity of light ashes are now to be laid the same manner; or flour and water; or on these tiles, and heaped up so as to cover a bladder; or linseed meal; or fat lute. the bulb and part of the neck of the retort. M. Lavoisier recommends, for joinings Dr. Black found that this produced a very which we desire to be air-tight, but which gradual diminution of the heat, as it recedes are pot to be exposed to heat, the followfrom the fuel, and is less liable to crack the ing: to sixteen ounces of bees-wax add

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"one and a half or two of thrpentine, and porting another wire, which will afford the keep it for use. When used, soften and means of steadying an alembic, or any other make it tough, by warming and working apparatus, by a string or small flexible wire between the fingers; then put it on the answering the same purpose. This is a joint in little rolls, and make it close; and, very convenient method of disposing vessels lastly, cover it with slips of wet bladder for the lamp heat, upon a small or moderate laced with pack-thread. But, if the joint is scale, for distillations, sublimation, evapoliable to be warmed, or heated during the ration, drying, and the like. A small sand. operation, you must take fat lute. This is bath may be placed, when needful, in the made of raw pipe-clay and linseed oil, wire above the flame: b is an intermediate beaten together very hard, to the consis. condensing vessel, called a quilled receiver, tence of a stiff adhesive paste.

which conveys the condensed product into Of the second kind of lutes, called the a bottle, c. The rod which supports b shows fire-lutes, a great variety have been propos- how useful these instruments are in their ed, and some of them compositions of many various applications. ingredients, but none are equal, or superior, The condensation of vapours after distillato clay and sand; riz, sand 3, or 4, or tion, and the transmission of gases, which 5, or 6, to clay 1. These are for luting may arise along with them to their recepvessels together, and for coatings. But in tacles, has been very well and scientifically Jining furnaces, Dr. Black used a donble effected by the late Mr. Woulfe, in an aplining; first, a charcoal-lute; secondly, a paratus of bottles which is distinguished by fire-lute.

his name. The original contrivance will be He found that a layer of powdered clar- easily understood by description, and in. coal, beaten up, or kneaded, with as little stead of a drawing of that arrangement of water as will give its particles adhesion vessels, we shall give one of the most simenough to attach itself to the metal sides of ple, safe, and convenient of all the improvethe furnace, by means of cautious beating, ments which have since been made in it; forms a firm stratum, which is the most im- namely, that contrived by Dr. Hamilton, perfect conductor of heat of all that he had and figured at the end of his “ Translation tried. When this layer of charcoal is de- of Berthollet on Dying." Suppose the retort fended from the action of the air by a layer and receiver, (fig. 1.) or any other distillaof fire-lute, composed of one part of fine tory apparatus, to have a communication clay, and three or four parts of sand, care from the upper parts of the receiver, a, at fully put on, and consolidated by gently c by a tube leading into a bottle having beating it from day to day, till it no longer three necks, and partly filled with water, receives an impression from the mallet; it beneath the surface of which the said tube, will last as long as any part of the furnace. after passing this, an air-tight cork was Its durability will be greatly improved, plunged. Another of the necks of the bot. without much charge in its conducting tle is provided with an upright open tube, power, by using, instead of pure water, also passing a cork and plunged in the water made muddy by about one-twentieth water in order that air may enter in case of of pipe-clay. If finely powdered charcoal absorption, or the liquid may rise a little in be kneaded with one-fifth of pipe-clay, it it, in case of pressure from within. The may be kneaded and formed into any shape, third neck of the bottle affords a communiand will be so impervious to heat that a bit cation by means of a tube with another of it may be held in the fingers within an two necked bottle, fitted 'up in all respects inch of where it is red hot. Such a com- in the same manner as the bottle communiposition is, therefore, very proper for the cating with e. And in this manner we may doors of furnaces, and for stopples for such conceive a series of three or more bottles, apertures as must be frequently opened the last of which may communicate with a and shut.

pneumatic apparatus which is to receive Fig. 4, represents an Argand's lamp capa. the incondensable gas. This system of botble of being adjusted at different heights, tles and tubes is sometimes fitted together by a sliding socket, on a stem or rod. by grinding, and sometimes made secure Another similar socket is seen above, into by lutes; but in most constructions, though which a ring of wire is inserted for support the advantages are very considerable, the ing the retort, a, at any required distance apparatus is difficult to be put together, and above the flame. A third socket may be easily deranged or injured. added, still higher upon the stem, for sup. Fig. 5, represents Dr. Hamilton's appe

. ratus. A is the retort fitted by grinding vently elastic fluids are received and nya. into a plug or piece, B, represented at b, naged. For such gases as are not absorbed which last is also fitted by grinding into the by water, a wooden tub may be used, havpeck of a globular receiver, C.

ing a shelf therein, at such a depth as to The use of the additional piece, b, is to stand a little below the intended surface of afford a due inclination to the retort by an the water; or, instead of a shelf, a shortobliquity of its perforation or hole, instead legged stool, loaded with lead, may be of allowing it to remain horizontal, as it used, and in that case any tub or vessel would, if fitted to the hole in C, and also may be used. Jars, or vessels of any conto facilitate the grinding in, of a new re- venient figure, being filled with water by tort in the case of breakage. The piece, b, immersion, and turning them bottom up. has a stopper, a, which can be put when wards, may be placed on the shelf, which ever the retort is taken out, whether for should have holes in it for the convenience weighing at, or for any other purpose. The of pouring up any gas, whether from ano. first receiver, C, has a smaller neck oppo- ther jar, bottle, or vessel, or from the neck site to B, which is ground into a corres- or tube of a retort, or other apparatus. ponding neck of D, the second receiver, Jars, &c. thus filled may be conveyed away, which last is tubulated, and bas a tube, either by corking the bottle, or by putting H, open at both ends, ground into its a saucer, or other shallow vessel, beneath vertical neck for the purpose of permitting the mouth of the jar, and taking both out to. absorption and re-acting, by its contents, gether, with water in the sancer. against the force required to protrude any Gases which are absorbed by water are gas through the bended tube, I KL. usually received over mercury, in which Every one of the range of the receiver, E case, on account of the weight, as well as F G, has also two necks, by which they the expence of the fluid, the vessels are are successively fitted to each other, and made smaller, and the trough has a deep each interior deck has a tube of about a cavity sufficient for immersion, but no quarter of an inch fitted into it, wbich, by larger, and a broad shallow part of the its curvate, reaches nearly to the bottom of trough supplies the place of a shelf for the the liquid (usually water) placed in each. jars to stand upon; and there is an actual By this disposition the usual first prodnct shelf at one part only over the end of the of condensation is received in C, and the deep cavity. Fig. 6, represents a trough for purer vapours proceeding to D, are in part mercury, which may be made of wood or condensed by the water placed therein, of stone. The space, V, admits the jar, A, to and are partly urged through the tube, I, be impiersed, and when full it is raised and into contact with the water in E: and what. placed bottom downwards upon the shallow ever may escape condensation in E, will be bottom. G is a retort, containing some urged through the tube, K, into the liquid materials from which gas, being extricated. in F; and in this manner the operation rises beneath A, and displaces the mercury. may proceed through the whole set of yes- X and Y are grooves, into which one or sels, till the gasiform remaining product, if more wooden shelves may be slided, as any, shall pass out then beneath the mouth occasion may require, in which application of one or the other of the three inverted bot. they are first introduced at the wider part, tles, at P, which are filled with water, and T, in the plan, fig. 7. have their mouths immersed below the sur- An apparatus, almost indispensable in exface of the water, in a dish at the end of the periments on the gases, is a gazometer, series. S and s are a pair of pieces of wood which enables the operator to receive and which serve to support one of the globes, and preserve large quantities of gas with the very conveniently afford an adjustment, by aid of only a few pounds of water. These pressing them more or less near together. vessels are made of varions forms, but one This apparatus is drawn upon a scale of of the most simple is shown in fig. 8. It about half an inch to a foot, which is a pro. consists of an outer fixed vessel, d, and an in. per size to be worked by an Argand's ner moveable one, c, both of japanned iron. lamp; if it were made larger, the retort The latter slides easily up and down within would of course require to be supported as the other, and is suspended by cords passusual, by the parts of the furpace, or other. ing pullies, to which are attached the counwise.

terpoises, &c. To avoid the incumbrance The dish and bottles at the extremity of of a great weight of water, the outer vessel, shis apparatus show how the gases or perma- d, is made double, or is composed of two cylinders, the inner of which is closed at the the funnel at b. When gas is to be transtop and at the bottom. Tbe space only ferred into this vessel from the gazometer, of about half an inch is left between the vessel is first completely filled with wathe two cylinders as shown by the dotted ter through the funnel, the cock a being left lines. In this space the vessel, c, may open and c shut. By means of an horizonmove freely up and down. The interval is tal pipe, the aperture a is connected with a filled with water as high as the top of the of the gazometer. The cock b being shut, inner cylinder. The cup or rim on the a and c are opened, and the vessel c of the top of the onter vessel, is to prevent the gazometer, fig. 8, gently pressed downwater from overflowing when the vessel, c, wards with the hand. The gas then descends is forcibly pressed down, in which situation from the gazometer till the air-holder is full, it is placed whenever gas is about to be wbich may be known by the water ceasing collected. The gas enters from the vessel to escape through the cock c. All the in which it is produced; by the communi- cocks are then to be shut, and the vessels cating opening b, and passes along the per- disunited. To apply this gas to any pur. pendicolar pipe marked by dotted lines in pose, an empty bladder may be screwed on the centre, into the cavity of the vessel, c, a ; and water being poured through the which continuies rising till it is full.

funnel b, a corresponding quantity of gas is To transfer the gas, or to apply it to any forced into the bladder. By lengthening purpose, the cock, b, is to be shut, and an the pipe, b, the pressure of a column of empty bladder, or bottle of elastic gum, water may be added ; and the gas being furnished with a stop cock, is to be screwed forced through a, with considerable velocion a. When the vessel, c, is pressed down ty, may be applied to the purpose of a blowby the hand, the gas passes down the cen- pipe, &c. &c. tral pipe, which it bad before ascended, The gazometer already described, is and its escape at b being prevented, it finds fitted only for the reception of gases that its way up a pipe which is fixed on the are confinable by water, because quickouter surface of the vessel, and which is silver would act on the tinning and solder terminated by the cock a. By means of of the vessel, and would not only be an ivory mouth-piece screwed on this cock, spoiled itself, but would destroy the appa. the gas included in the instrument may be ratus. Yet an instrument of this kind, in respired; the nostrils being closed by the which mercury can be employed, is pecufingers. When it is required to transfer the liarly desirable, on account of the great gas into glass jars standing in water, a weight of that fluid ; and two varieties of crooked tube may be employed, one end the mercurial gazometer have therefore been of which is screwed upon the cock, b, while invented. The one of glass, is the conthe other aperture is bronght under the trivance of Mr. Clayfield, and may be seen inverted funnel, fixed into the shelf of the represented in the plate prefixed to Mr. pneumatic trongh.

Davy's researches. In the other, invented Several alterations have been made in by Mr. Pepys the cistern for the mercury the form of this apparatus, but they are is of cast iron. A drawing and representaprincipally such as add merely to its neat- tion of it may be found in the fifth volume ness and beauty, and not to its utility ; and of the Philosophical Magazine ; but as they render it less easy of explanation. The neither of these instruments are essential counterpoises, e e, are now generally con- to the chemical student, and as they are cealed in the framing, and the vessel c is fre- required only in experiments of research, we quently made of glass.

refer to the minute descriptions of their When large quantities of gas are required respective inventors. (as at a public lecture) the gas holder, Very complete sketches of chemical intig. 9, will be found extremely useful. It struments and furnaces may be seen in is macle of tinned iron plate, japanned Henry's chemistry. both within and without. Two shortA fter the general description we have pipes a, and c, terminated by cocks, pro- bere given of the arrangement and apparaceed from its sides, and another, b, passes tus for chemical experiments, we shall conthrough the middle of the top or cover, to clude with a short account of the blow-pipe, which it is soldered, and reaches within It is a tube which terminates in a perfo. half an inch of the bottom

• ration not exceeding the hole which might It will be found convenient also to have be made by a small pin. There is no dif. an air cock with a very wide bore fixed to ficulty, in case of emergency, in making one

ont of a tube of glass, and the common apt to be carried away by the current of blow-pipes sold at the ironmongers for a few flame. These may be secured by making a pence, and in universal use with workmen small hole in the charcoal, kato which the are very good. Others more costly and powder is to be put, and covered with anoelegant, which bave a small space for the ther small piece of charcoal, which partly condensation of the vapour of the breath, protects them from the flame. Some experi. are sold by the makers of chemical appara ments of reduction are made by binding tus. It regaires some address to produce two small pieces of charcoal together, cuta constant stream of air by blowing throngh ting a channel along the piece intended to this pipe ; but the principal artifice con be the undermost, and making a cavity in sists in keeping the tongue to the roof of the the middle of this channel to contain the mouth, and using the breath by the pressure subject matter of examination. With this of the mascles of the face instead of the apparatus the flame is urged throngh the chest. Some workmen in glass coutrive to channel between the two pieces of coal, hold the pipe steady between the teeth, and violently heats the substance in the caand by that means have both hands at li vity, which may be considered as a closed berty for use ; but as this requires uncom- vessel. mon steadiness in the head, the philosophi- A great number of mineral bodies are cal chemist will probably prefer fixing his not fusible by mere flame, urged by compipe to one of his stands. Some blow-pipes mon air through the blow-pipe; though oxybave been made, through which a stream of gen gas subdues most bodies. See Gas vapour from boiling alcohol is urged; but oxygen. these instruments seem to be rather toys Whenever, therefore, the fusion of any than of use to the actual chemical investi- refractory substance is to be attempted, gator. It appears preferable to use bel some other substance must be added which lows, as the enamellers do, where an ex- is more fusible, and capable of dissolving tensive application of this implement is re- the former. These solvents, in the dry way, quired; though in this case the desirable are distingnished by the name of fluxes, requisite of portability is lost sight of.. and, like the solvents used in the humid

The bodies intended to be heated by the way, are mostly salipe. It may easily be blow-pipe must not, in general, exceed the imagined, that the nature of the products size of a pepper-corn, unless bellows and a will greatly vary, according to that of the very large flame be used. The proper sup- flux, which enters into combination with ports are either a piece of smooth, close. them; and accordingly they are varied in grained charcoal, for such bodies as are not experiments, as well as in operations, in the subject to an alteration of their properties, large way. The blow.pipe experiments, from the inflammability of the coal, as though conducted upon the same principles might be contrary to the nature of the in- as those upon a larger scale, differ nevervestigation. This support is therefore most theless from them in two particulars ; namefrequently used; as it is properly adaptedly, that the whole of the phenomena are vifor saline, earthy, and many metallic bo. sible throughout, and that the residues are dies. The other support consists of a spoon, of no value, otherwise than as they serve to somewhat less than a quarter of an inch in indicate facts. For these reasons, every diameter, maile of a metal not subject to flux, without exception, might be used with oxydation; that is to say, pure gold, silver, the blow-pipe, provided it were not of such or platina, or such a mixture of these me a nature as to sink into the charcoal. We tals as might be found to be least deficient may therefore select a certain small numin the requisite degree of hardness, which ber of the most convenient fluxes, and note gold or silver alone does not possess.. Berg. the effects which they respectively produce man advised to add one-tenth of platina to upon the various mineral bodies; and these a given mass of silver. There is, however, will serve as indications to enable the cheno very considerable inconvenience result. mical enquirer to distinguish them again ing from the use of a small spoon, either of with a great degree of accuracy, not to gold or of silver; and platina possesses mention, that he may also derive much adevery quality which can be wished for. vantage, with regard to the more extensive The small metallic spoon must of course be operations be might be disposed to underproperly fixed in a socket of metal, pro- take. A considerable part of this prelimivided with a wooden handle.

nary labour has already been performed by Very small or palverulent substances are Engestrom, Bergman, Mongez, and others;

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