Part I. Chap. VIII. and need not be here repeated, will answer the

purpose; when pure gasses are procured, this apparatus will require no alterations, except that the capacity of the vessels may then be diminished. See Pl. IV. Fig. 5.

The combustion, when once begun, continues for a considerable time, but weakens gradually, in proportion as the quantity of azotic gas remaining from the combustion increases, till at last the azotic gas is in such over proportion that the combustion can no longer be supported, and the flame goes out. This spontaneous extinction must be prevented, because, as the hydrogen gas is pressed upon in its reservoir, by an inch and a half of water, whilst the oxygen gas suffers a pressure only of three lines, a mixture of the two would take place in the balloon, which would at last be forced by the superior pressure into the reservoir of oxygen gas. Wherefore the combustion must be stopped, by shutting the stop-cock of the tube dDd whenever the flame grows very feeble; for which purpose it must be attentively watched.

There is another apparatus for combustion, which, though we cannot with it perform experiments with the same scrupulous exactness as with the preceding instruments, gives very striking results that are extremely proper to be shewn in courses of philosophical chemistry. It consists of a worm EF, Pl. IX. Fig. 5. contained in a metallic cooller ABCD. To the upper part of this worm E, the chimney GH is fixed, which is composed of two tubes, the inner of which is a continuation of the worm, and the outer one is a case of tin-plate, which surrounds it at about an inch distance, and the interval is filled up with sand. At the inferior extremity K of the inner tube, a glass tube is fixed, to which we adopt the Argand lamp LM for burning alkohol, &c.

Things being thus disposed, and the lamp being filled with a determinate quantity of alkohol, it is set on fire; the water which is formed during the combustion rises in the chimney KE, and being condensed in the worm, runs out at its extremity F into the bottle P. The double tube of the chimney, filled with sand in the interstice, is to prevent the tube from cooling in its upper part, and condensing the water; otherwise, it would fall back in the tube, and we should not be able to ascertain its quantity, and besides it might fall in drops upon the wick, and extinguish the flame. The intention of this construction, is to keep the chimney always hot, and the worm always cool, that the water may be preserved in the state of vapour whilst rising, and may be condensed immediately upon getting into the descending part of the apparatus. By this instrument, which was contrived by Mr Meusnier, and which is described by me in the Memoirs of the Academy for 1784, p. 593. we may, with attention to keep the worm always cold, collect nearly seventeen ounces of water from the combustion of sixteen ounces of alkohol.

SECT. VIII.

_Of the Oxydation of Metals._

The term _oxydation_ or _calcination_ is chiefly used to signify the process by which metals exposed to a certain degree of heat are converted into oxyds, by absorbing oxygen from the air. This combination takes place in consequence of oxygen possessing a greater affinity to metals, at a certain temperature, than to caloric, which becomes disengaged in its free state; but, as this disengagement, when made in common air, is slow and progressive, it is scarcely evident to the senses. It is quite otherwise, however, when oxydation takes place in oxygen gas; for, being produced with much greater rapidity, it is generally accompanied with heat and light, so as evidently to show that metallic substances are real combustible bodies.

All the metals have not the same degree of affinity to oxygen. Gold, silver, and platina, for instance, are incapable of taking it away from its combination with caloric, even in the greatest known heat; whereas the other metals absorb it in a larger or smaller quantity, until the affinities of the metal to oxygen, and of the latter to caloric, are in exact equilibrium. Indeed, this state of equilibrium of affinities may be assumed as a general law of nature in all combinations.

In all operations of this nature, the oxydation of metals is accelerated by giving free access to the air; it is sometimes much assisted by joining the action of a bellows, which directs a stream of air over the surface of the metal. This process becomes greatly more rapid if a stream of oxygen gas be used, which is readily done by means of the gazometer formerly described. The metal, in this case, throws out a brilliant flame, and the oxydation is very quickly accomplished; but this method can only be used in very confined experiments, on account of the expence of procuring oxygen gas. In the essay of ores, and in all the common operations of the laboratory, the calcination or oxydation of metals is usually performed in a dish of baked clay, Pl. IV. Fig. 6. commonly called a _roasting test_, placed in a strong furnace. The substances to be oxydated are frequently stirred, on purpose to present fresh surfaces to the air.

Whenever this operation is performed upon a metal which is not volatile, and from which nothing flies off into the surrounding air during the process, the metal acquires additional weight; but the cause of this increased weight during oxydation could never have been discovered by means of experiments performed in free air; and it is only since these operations have been performed in close vessels, and in determinate quantities of air, that any just conjectures have been formed concerning the cause of this phenomenon. The first method for this purpose is due to Dr Priestley, who exposes the metal to be calcined in a porcelain cup N, Pl. IV. Fig. 11. placed upon the stand IK, under a jar A, in the bason BCDE, full of water; the water is made to rise up to GH, by sucking out the air with a syphon, and the focus of a burning glass is made to fall upon the metal. In a few minutes the oxydation takes place, a part of the oxygen contained in the air combines with the metal, and a proportional diminution of the volume of air is produced; what remains is nothing more than azotic gas, still however mixed with a small quantity of oxygen gas. I have given an account of a series of experiments made with this apparatus in my Physical and Chemical Essays, first published in 1773. Mercury may be used instead of water in this experiment, whereby the results are rendered still more conclusive.

Another process for this purpose was invented by Mr Boyle, and of which I gave an account in the Memoirs of the Academy for 1774, p. 351. The metal is introduced into a retort, Pl. III. Fig. 20. the beak of which is hermetically sealed; the metal is then oxydated by means of heat applied with great precaution. The weight of the vessel, and its contained substances, is not at all changed by this process, until the extremity of the neck of the retort is broken; but, when that is done, the external air rushes in with a hissing noise. This operation is attended with danger, unless a part of the air is driven out of the retort, by means of heat, before it is hermetically sealed, as otherwise the retort would be apt to burst by the dilation of the air when placed in the furnace. The quantity of air driven out may be received under a jar in the pneumato-chemical apparatus, by which its quantity, and that of the air remaining in the retort, is ascertained. I have not multiplied my experiments upon oxydation of metals so much as I could have wished; neither have I obtained satisfactory results with any metal except tin. It is much to be wished that some person would undertake a series of experiments upon oxydation of metals in the several gasses; the subject is important, and would fully repay any trouble which this kind of experiment might occasion.

As all the oxyds of mercury are capable of revivifying without addition, and restore the oxygen gas they had before absorbed, this seemed to be the most proper metal for becoming the subject of conclusive experiments upon oxydation. I formerly endeavoured to accomplish the oxydation of mercury in close vessels, by filling a retort, containing a small quantity of mercury, with oxygen gas, and adapting a bladder half full of the same gas to its beak; See Pl. IV. Fig. 12. Afterwards, by heating the mercury in the retort for a very long time, I succeeded in oxydating a very small portion, so as to form a little red oxyd floating upon the surface of the running mercury; but the quantity was so small, that the smallest error committed in the determination of the quantities of oxygen gas before and after the operation must have thrown very great uncertainty upon the results of the experiment. I was, besides, dissatisfied with this process, and not without cause, lest any air might have escaped through the pores of the bladder, more especially as it becomes shrivelled by the heat of the furnace, unless covered over with cloths kept constantly wet.

This experiment is performed with more certainty in the apparatus described in the Memoirs of the Academy for 1775, p. 580. This consists of a retort, A, Pl. IV. Fig. 2. having a crooked glass tube BCDE of ten or twelve lines internal diameter, melted on to its beak, and which is engaged under the bell glass FG, standing with its mouth downwards, in a bason filled with water or mercury. The retort is placed upon the bars of the furnace MMNN, Pl. IV. Fig. 2. or in a sand bath, and by means of this apparatus we may, in the course of several days, oxydate a small quantity of mercury in common air; the red oxyd floats upon the surface, from which it may be collected and revivified, so as to compare the quantity of oxygen gas obtained in revivification with the absorption which took place during oxydation. This kind of experiment can only be performed upon a small scale, so that no very certain conclusions can be drawn from them[61].

The combustion of iron in oxygen gas being a true oxydation of that metal, ought to be mentioned in this place. The apparatus employed by Mr Ingenhousz for this operation is represented in Pl. IV. Fig. 17.; but, having already described it sufficiently in Chap. III. I shall refer the reader to what is said of it in that place. Iron may likewise be oxydated by combustion in vessels filled with oxygen gas, in the way already directed for phosphorus and charcoal. This apparatus is represented Pl. IV. Fig. 3. and described in the fifth chapter of the first part of this work. We learn from Mr Ingenhousz, that all the metals, except gold, silver, and mercury, may be burnt or oxydated in the same manner, by reducing them into very fine wire, or very thin plates cut into narrow slips; these are twisted round with iron-wire, which communicates the property of burning to the other metals.

Mercury is even difficultly oxydated in free air. In chemical laboratories, this process is usually carried on in a matrass A, Pl. IV. Fig. having a very flat body, and a very long neck BC, which vessel is commonly called _Boyle's bell_. A quantity of mercury is introduced sufficient to cover the bottom, and it is placed in a sand-bath, which keeps up a constant heat approaching to that of boiling mercury. By continuing this operation with five or six similar matrasses during several months, and renewing the mercury from time to time, a few ounces of red oxyd are at last obtained. The great slowness and inconvenience of this apparatus arises from the air not being sufficiently renewed; but if, on the other hand, too free a circulation were given to the external air, it would carry off the mercury in solution in the state of vapour, so that in a few days none would remain in the vessel.

As, of all the experiments upon the oxydation of metals, those with mercury are the most conclusive, it were much to be wished that a simple apparatus could be contrived by which this oxydation and its results might be demonstrated in public courses of chemistry. This might, in my opinion, be accomplished by methods similar to those I have already described for the combustion of charcoal and the oils; but, from other pursuits, I have not been able hitherto to resume this kind of experiment.

The oxyd of mercury revives without addition, by being heated to a slightly red heat. In this degree of temperature, oxygen has greater affinity to caloric than to mercury, and forms oxygen gas. This is always mixed with a small portion of azotic gas, which indicates that the mercury absorbs a small portion of this latter gas during oxydation. It almost always contains a little carbonic acid gas, which must undoubtedly be attributed to the foulnesses of the oxyd; these are charred by the heat, and convert a part of the oxygen gas into carbonic acid.

If chemists were reduced to the necessity of procuring all the oxygen gas employed in their experiments from mercury oxydated by heat without addition, or, as it is called, _calcined_ or _precipitated_ per se, the excessive dearness of that preparation would render experiments, even upon a moderate scale, quite impracticable. But mercury may likewise be oxydated by means of nitric acid; and in this way we procure a red oxyd, even more pure than that produced by calcination. I have sometimes prepared this oxyd by dissolving mercury in nitric acid, evaporating to dryness, and calcining the salt, either in a retort, or in capsules formed of pieces of broken matrasses and retorts, in the manner formerly described; but I have never succeeded in making it equally beautiful with what is sold by the druggists, and which is, I believe, brought from Holland. In choosing this, we ought to prefer what is in solid lumps composed of soft adhering scales, as when in powder it is sometimes adulterated with red oxyd of lead.

To obtain oxygen gas from the red oxyd of mercury, I usually employ a porcelain retort, having a long glass tube adapted to its beak, which is engaged under jars in the water pneumato-chemical apparatus, and I place a bottle in the water, at the end of the tube, for receiving the mercury, in proportion as it revives and distils over. As the oxygen gas never appears till the retort becomes red, it seems to prove the principle established by Mr Berthollet, that an obscure heat can never form oxygen gas, and that light is one of its constituent elements. We must reject the first portion of gas which comes over, as being mixed with common air, from what was contained in the retort at the beginning of the experiment; but, even with this precaution, the oxygen gas procured is usually contaminated with a tenth part of azotic gas, and with a very small portion of carbonic acid gas. This latter is readily got rid of, by making the gas pass through a solution of caustic alkali; but we know of no method for separating the azotic gas; its proportions may however be ascertained, by leaving a known quantity of the oxygen gas contaminated with it for a fortnight, in contact with sulphuret of soda or potash, which absorbs the oxygen gas so as to convert the sulphur into sulphuric acid, and leaves the azotic gas remaining pure.

We may likewise procure oxygen gas from black oxyd of manganese or nitrat of potash, by exposing them to a red heat in the apparatus already described for operating upon red oxyd of mercury; only, as it requires such a heat as is at least capable of softening glass, we must employ retorts of stone or of porcelain. But the purest and best oxygen gas is what is disengaged from oxygenated muriat of potash by simple heat. This operation is performed in a glass retort, and the gas obtained is perfectly pure, provided that the first portions, which are mixed with the common air of the vessels, be rejected.

FOOTNOTES:

[61] See an account of this experiment, Part. I. Chap. iii.--A.

CHAP. IX.

_Of Deflagration._

I have already shown, Part I. Chap. IX. that oxygen does not always part with the whole of the caloric it contained in the state of gas when it enters into combination with other bodies. It carries almost the whole of its caloric alongst with it in entering into the combinations which form nitric acid and oxygenated muriatic acid; so that in nitrats, and more especially in oxygenated muriats, the oxygen is, in a certain degree, in the state of oxygen gas, condensed, and reduced to the smallest volume it is capable of occupying.

In these combinations, the caloric exerts a constant action upon the oxygen to bring it back to the state of gas; hence the oxygen adheres but very slightly, and the smallest additional force is capable of setting it free; and, when such force is applied, it often recovers the state of gas instantaneously. This rapid passage from the solid to the aëriform state is called detonation, or fulmination, because it is usually accompanied with noise and explosion. Deflagrations are commonly produced by means of combinations of charcoal either with nitre or oxygenated muriat of potash; sometimes, to assist the inflammation, sulphur is added; and, upon the just proportion of these ingredients, and the proper manipulation of the mixture, depends the art of making gun-powder.

As oxygen is changed, by deflagration with charcoal, into carbonic acid, instead of oxygen gas, carbonic acid gas is disengaged, at least when the mixture has been made in just proportions. In deflagration with nitre, azotic gas is likewise disengaged, because azote is one of the constituent elements of nitric acid.

The sudden and instantaneous disengagement and expansion of these gasses is not, however, sufficient for explaining all the phenomena of deflagration; because, if this were the sole operating power, gun powder would always be so much the stronger in proportion as the quantity of gas disengaged in a given time was the more considerable, which does not always accord with experiment. I have tried some kinds which produced almost double the effect of ordinary gun powder, although they gave out a sixth part less of gas during deflagration. It would appear that the quantity of caloric disengaged at the moment of detonation contributes considerably to the expansive effects produced; for, although caloric penetrates freely through the pores of every body in nature, it can only do so progressively, and in a given time; hence, when the quantity disengaged at once is too large to get through the pores of the surrounding bodies, it must necessarily act in the same way with ordinary elastic fluids, and overturn every thing that opposes its passage. This must, at least in part, take place when gun-powder is set on fire in a cannon; as, although the metal is permeable to caloric, the quantity disengaged at once is too large to find its way through the pores of the metal, it must therefore make an effort to escape on every side; and, as the resistance all around, excepting towards the muzzle, is too great to be overcome, this effort is employed for expelling the bullet.

The caloric produces a second effect, by means of the repulsive force exerted between its particles; it causes the gasses, disengaged at the moment of deflagration, to expand with a degree of force proportioned to the temperature produced.

It is very probable that water is decomposed during the deflagration of gun-powder, and that part of the oxygen furnished to the nascent carbonic acid gas is produced from it. If so, a considerable quantity of hydrogen gas must be disengaged in the instant of deflagration, which expands, and contributes to the force of the explosion. It may readily be conceived how greatly this circumstance must increase the effect of powder, if we consider that a pint of hydrogen gas weighs only one grain and two thirds; hence a very small quantity in weight must occupy a very large space, and it must exert a prodigious expansive force in passing from the liquid to the aëriform state of existence.

In the last place, as a portion of undecomposed water is reduced to vapour during the deflagration of gun-powder, and as water, in the state of gas, occupies seventeen or eighteen hundred times more space than in its liquid state, this circumstance must likewise contribute largely to the explosive force of the powder.

I have already made a considerable series of experiments upon the nature of the elastic fluids disengaged during the deflagration of nitre with charcoal and sulphur; and have made some, likewise, with the oxygenated muriat of potash. This method of investigation leads to tollerably accurate conclusions with respect to the constituent elements of these salts. Some of the principal results of these experiments, and of the consequences drawn from them respecting the analysis of nitric acid, are reported in the collection of memoirs presented to the Academy by foreign philosophers, vol. xi. p. 625. Since then I have procured more convenient instruments, and I intend to repeat these experiments upon a larger scale, by which I shall procure more accurate precision in their results; the following, however, is the process I have hitherto employed. I would very earnestly advise such as intend to repeat some of these experiments, to be very much upon their guard in operating upon any mixture which contains nitre, charcoal, and sulphur, and more especially with those in which oxygenated muriat of potash is mixed with these two materials.

I make use of pistol barrels, about six inches long, and of five or six lines diameter, having the touch-hole spiked up with an iron nail strongly driven in, and broken in the hole, and a little tin-smith's solder run in to prevent any possible issue for the air. These are charged with a mixture of known quantities of nitre and charcoal, or any other mixture capable of deflagration, reduced to an impalpable powder, and formed into a paste with a moderate quantity of water. Every portion of the materials introduced must be rammed down with a rammer nearly of the same caliber with the barrel, four or five lines at the muzzle must be left empty, and about two inches of quick match are added at the end of the charge. The only difficulty in this experiment, especially when sulphur is contained in the mixture, is to discover the proper degree of moistening; for, if the paste be too much wetted, it will not take fire, and if too dry, the deflagration is apt to become too rapid, and even dangerous.

When the experiment is not intended to be rigorously exact, we set fire to the match, and, when it is just about to communicate with the charge, we plunge the pistol below a large bell-glass full of water, in the pneumato chemical apparatus. The deflagration begins, and continues in the water, and gas is disengaged with less or more rapidity, in proportion as the mixture is more or less dry. So long as the deflagration continues, the muzzle of the pistol must be kept somewhat inclined downwards, to prevent the water from getting into its barrel. In this manner I have sometimes collected the gas produced from the deflagration of an ounce and half, or two ounces, of nitre.

In this manner of operating it is impossible to determine the quantity of carbonic acid gas disengaged, because a part of it is absorbed by the water while passing through it; but, when the carbonic acid is absorbed, the azotic gas remains; and, if it be agitated for a few minutes in caustic alkaline solution, we obtain it pure, and can easily determine its volume and weight. We may even, in this way, acquire a tollerably exact knowledge of the quantity of carbonic acid by repeating the experiment a great many times, and varying the proportions of charcoal, till we find the exact quantity requisite to deflagrate the whole nitre employed. Hence, by means of the weight of charcoal employed, we determine the weight of oxygen necessary for saturation, and deduce the quantity of oxygen contained in a given weight of nitre.

I have used another process, by which the results of this experiment are considerably more accurate, which consists in receiving the disengaged gasses in bell-glasses filled with mercury. The mercurial apparatus I employ is large enough to contain jars of from twelve to fifteen pints in capacity, which are not very readily managed when full of mercury, and even require to be filled by a particular method. When the jar is placed in the cistern of mercury, a glass syphon is introduced, connected with a small air-pump, by means of which the air is exhausted, and the mercury rises so as to fill the jar. After this, the gas of the deflagration is made to pass into the jar in the same manner as directed when water is employed.

I must again repeat, that this species of experiment requires to be performed with the greatest possible precautions. I have sometimes seen, when the disengagement of gas proceeded with too great rapidity, jars filled with more than an hundred and fifty pounds of mercury driven off by the force of the explosion, and broken to pieces, while the mercury was scattered about in great quantities.

When the experiment has succeeded, and the gas is collected under the jar, its quantity in general, and the nature and quantities of the several species of gasses of which the mixture is composed, are accurately ascertained by the methods already pointed out in the second chapter of this part of my work. I have been prevented from putting the last hand to the experiments I had begun upon deflagration, from their connection with the objects I am at present engaged in; and I am in hopes they will throw considerable light upon the operations belonging to the manufacture of gun-powder.

CHAP. X.

_Of the Instruments necessary for Operating upon Bodies in very high Temperatures._

SECT. I.

_Of Fusion._

We have already seen, that, by aqueous solution, in which the particles of bodies are separated from each other, neither the solvent nor the body held in solution are at all decomposed; so that, whenever the cause of separation ceases, the particles reunite, and the saline substance recovers precisely the same appearance and properties it possessed before solution. Real solutions are produced by fire, or by introducing and accumulating a great quantity of caloric between the particles of bodies; and this species of solution in caloric is usually called _fusion_.

This operation is commonly performed in vessels called crucibles, which must necessarily be less fusible than the bodies they are intended to contain. Hence, in all ages, chemists have been extremely solicitous to procure crucibles of very refractory materials, or such as are capable of resisting a very high degree of heat. The best are made of very pure clay or of porcelain earth; whereas such as are made of clay mixed with calcareous or silicious earth are very fusible. All the crucibles made in the neighbourhood of Paris are of this kind, and consequently unfit for most chemical experiments. The Hessian crucibles are tolerably good; but the best are made of Limoges earth, which seems absolutely infusible. We have, in France, a great many clays very fit for making crucibles; such, for instance, is the kind used for making melting pots at the glass-manufactory of St Gobin.

Crucibles are made of various forms, according to the operations they are intended to perform. Several of the most common kinds are represented Pl. VII. Fig. 7. 8. 9. and 10. the one represented at Fig. 9. is almost shut at its mouth.

Though fusion may often take place without changing the nature of the fused body, this operation is frequently employed as a chemical means of decomposing and recompounding bodies. In this way all the metals are extracted from their ores; and, by this process, they are revivified, moulded, and alloyed with each other. By this process sand and alkali are combined to form glass, and by it likewise pastes, or coloured stones, enamels, &c. are formed.

The action of violent fire was much more frequently employed by the ancient chemists than it is in modern experiments. Since greater precision has been employed in philosophical researches, the _humid_ has been preferred to the _dry_ method of process, and fusion is seldom had recourse to until all the other means of analysis have failed.

SECT. II.

_Of Furnaces._

These are instruments of most universal use in chemistry; and, as the success of a great number of experiments depends upon their being well or ill constructed, it is of great importance that a laboratory be well provided in this respect. A furnace is a kind of hollow cylindrical tower, sometimes widened above, Pl. XIII. Fig. 1. ABCD, which must have at least two lateral openings; one in its upper part F, which is the door of the fire-place, and one below, G, leading to the ash-hole. Between these the furnace is divided by a horizontal grate, intended for supporting the fewel, the situation of which is marked in the figure by the line HI. Though this be the least complicated of all the chemical furnaces, yet it is applicable to a great number of purposes. By it lead, tin, bismuth, and, in general, every substance which does not require a very strong fire, may be melted in crucibles; it will serve for metallic oxydations, for evaporatory vessels, and for sand-baths, as in Pl. III. Fig. 1. and 2. To render it proper for these purposes, several notches, m m m m, Pl. XIII. Fig. 1. are made in its upper edge, as otherwise any pan which might be placed over the fire would stop the passage of the air, and prevent the fewel from burning. This furnace can only produce a moderate degree of heat, because the quantity of charcoal it is capable of consuming is limited by the quantity of air which is allowed to pass through the opening G of the ash-hole. Its power might be considerably augmented by enlarging this opening, but then the great stream of air which is convenient for some operations might be hurtful in others; wherefore we must have furnaces of different forms, constructed for different purposes, in our laboratories: There ought especially to be several of the kind now described of different sizes.

The reverberatory furnace, Pl. XIII. Fig. 2. is perhaps more necessary. This, like the common furnace, is composed of the ash-hole HIKL, the fire-place KLMN, the laboratory MNOP, and the dome RRSS, with its funnel or chimney TTVV; and to this last several additional tubes may be adapted, according to the nature of the different experiments. The retort A is placed in the division called the laboratory, and supported by two bars of iron which run across the furnace, and its beak comes out at a round hole in the side of the furnace, one half of which is cut in the piece called the laboratory, and the other in the dome. In most of the ready made reverberatory furnaces which are sold by the potters at Paris, the openings both above and below are too small: These do not allow a sufficient volume of air to pass through; hence, as the quantity of charcoal consumed, or, what is much the same thing, the quantity of caloric disengaged, is nearly in proportion to the quantity of air which passes through the furnace, these furnaces do not produce a sufficient effect in a great number of experiments. To remedy this defect, there ought to be two openings GG to the ash-hole; one of these is shut up when only a moderate fire is required; and both are kept open when the strongest power of the furnace is to be exerted. The opening of the dome SS ought likewise to be considerably larger than is usually made.

It is of great importance not to employ retorts of too large size in proportion to the furnace, as a sufficient space ought always to be allowed for the passage of the air between the sides of the furnace and the vessel. The retort A in the figure is too small for the size of the furnace, yet I find it more easy to point out the error than to correct it. The intention of the dome is to oblige the flame and heat to surround and strike back or reverberate upon every part of the retort, whence the furnace gets the name of reverberatory. Without this circumstance the retort would only be heated in its bottom, the vapours raised from the contained substance would condense in the upper part, and a continual cohabitation would take place without any thing passing over into the receiver, but, by means of the dome, the retort is equally heated in every part, and the vapours being forced out, can only condense in the neck of the retort, or in the recipient.

To prevent the bottom of the retort from being either heated or coolled too suddenly, it is sometimes placed in a small sand-bath of baked clay, standing upon the cross bars of the furnace. Likewise, in many operations, the retorts are coated over with lutes, some of which are intended to preserve them from the too sudden influence of heat or of cold, while others are for sustaining the glass, or forming a kind of second retort, which supports the glass one during operations wherein the strength of the fire might soften it. The former is made of brick-clay with a little cow's hair beat up alongst with it, into a paste or mortar, and spread over the glass or stone retorts. The latter is made of pure clay and pounded stone-ware mixed together, and used in the same manner. This dries and hardens by the fire, so as to form a true supplementary retort capable of retaining the materials, if the glass retort below should crack or soften. But, in experiments which are intended for collecting gasses, this lute, being porous, is of no manner of use.

In a great many experiments wherein very violent fire is not required, the reverberatory furnace may be used as a melting one, by leaving out the piece called the laboratory, and placing the dome immediately upon the fire-place, as represented Pl. XIII. Fig. 3. The furnace represented in Fig. 4. is very convenient for fusions; it is composed of the fire-place and ash-hole ABD, without a door, and having a hole E, which receives the muzzle of a pair of bellows strongly luted on, and the dome ABGH, which ought to be rather lower than is represented in the figure. This furnace is not capable of producing a very strong heat, but is sufficient for ordinary operations, and may be readily moved to any part of the laboratory where it is wanted. Though these particular furnaces are very convenient, every laboratory must be provided with a forge furnace, having a good pair of bellows, or, what is more necessary, a powerful melting furnace. I shall describe the one I use, with the principles upon which it is constructed.

The air circulates in a furnace in consequence of being heated in its passage through the burning coals; it dilates, and, becoming lighter than the surrounding air, is forced to rise upwards by the pressure of the lateral columns of air, and is replaced by fresh air from all sides, especially from below. This circulation of air even takes place when coals are burnt in a common chaffing dish; but we can readily conceive, that, in a furnace open on all sides, the mass of air which passes, all other circumstances being equal, cannot be so great as when it is obliged to pass through a furnace in the shape of a hollow tower, like most of the chemical furnaces, and consequently, that the combustion must be more rapid in a furnace of this latter construction. Suppose, for instance, the furnace ABCDEF open above, and filled with burning coals, the force with which the air passes through the coals will be in proportion to the difference between the specific gravity of two columns equal to AC, the one of cold air without, and the other of heated air within the furnace. There must be some heated air above the opening AB, and the superior levity of this ought likewise to be taken into consideration; but, as this portion is continually coolled and carried off by the external air, it cannot produce any great effect.

But, if we add to this furnace a large hollow tube GHAB of the same diameter, which preserves the air which has been heated by the burning coals from being coolled and dispersed by the surrounding air, the difference of specific gravity which causes the circulation will then be between two columns equal to GC. Hence, if GC be three times the length of AC, the circulation will have treble force. This is upon the supposition that the air in GHCD is as much heated as what is contained in ABCD, which is not strictly the case, because the heat must decrease between AB and GH; but, as the air in GHAB is much warmer than the external air, it follows, that the addition of the tube must increase the rapidity of the stream of air, that a larger quantity must pass through the coals, and consequently that a greater degree of combustion must take place.

We must not, however, conclude from these principles, that the length of this tube ought to be indefinitely prolonged; for, since the heat of the air gradually diminishes in passing from AB to GH, even from the contact of the sides of the tube, if the tube were prolonged to a certain degree, we would at last come to a point where the specific gravity of the included air would be equal to the air without; and, in this case, as the cool air would no longer tend to rise upwards, it would become a gravitating mass, resisting the ascension of the air below. Besides, as this air, which has served for combustion, is necessarily mixed with carbonic acid gas, which is considerably heavier than common air, if the tube were made long enough, the air might at last approach so near to the temperature of the external air as even to gravitate downwards; hence we must conclude, that the length of the tube added to a furnace must have some limit beyond which it weakens, instead of strengthening the force of the fire.

From these reflections it follows, that the first foot of tube added to a furnace produces more effect than the sixth, and the sixth more than the tenth; but we have no data to ascertain at what height we ought to stop. This limit of useful addition is so much the farther in proportion as the materials of the tube are weaker conductors of heat, because the air will thereby be so much less coolled; hence baked earth is much to be preferred to plate iron. It would be even of consequence to make the tube double, and to fill the interval with rammed charcoal, which is one of the worst conductors of heat known; by this the refrigeration of the air will be retarded, and the rapidity of the stream of air consequently increased; and, by this means, the tube may be made so much the longer.

As the fire-place is the hottest part of a furnace, and the part where the air is most dilated in its passage, this part ought to be made with a considerable widening or belly. This is the more necessary, as it is intended to contain the charcoal and crucible, as well as for the passage of the air which supports, or rather produces the combustion; hence we only allow the interstices between the coals for the passage of the air.

From these principles my melting furnace is constructed, which I believe is at least equal in power to any hitherto made, though I by no means pretend that it possesses the greatest possible intensity that can be produced in chemical furnaces. The augmentation of the volume of air produced during its passage through a melting furnace not being hitherto ascertained from experiment, we are still unacquainted with the proportions which should exist between the inferior and superior apertures, and the absolute size of which these openings should be made is still less understood; hence data are wanting by which to proceed upon principle, and we can only accomplish the end in view by repeated trials.

This furnace, which, according to the above stated rules, is in form of an eliptical spheroid, is represented Pl. XIII. Fig. 6. ABCD; it is cut off at the two ends by two plains, which pass, perpendicular to the axis, through the foci of the elipse. From this shape it is capable of containing a considerable quantity of charcoal, while it leaves sufficient space in the intervals for the passage of the air. That no obstacle may oppose the free access of external air, it is perfectly open below, after the model of Mr Macquer's melting furnace, and stands upon an iron tripod. The grate is made of flat bars set on edge, and with considerable interstices. To the upper part is added a chimney, or tube, of baked earth, ABFG, about eighteen feet long, and almost half the diameter of the furnace. Though this furnace produces a greater heat than any hitherto employed by chemists, it is still susceptible of being considerably increased in power by the means already mentioned, the principal of which is to render the tube as bad a conductor of heat as possible, by making it double, and filling the interval with rammed charcoal.

When it is required to know if lead contains any mixture of gold or silver, it is heated in a strong fire in capsules of calcined bones, which are called cuppels. The lead is oxydated, becomes vitrified, and sinks into the substance of the cuppel, while the gold or silver, being incapable of oxydation, remain pure. As lead will not oxydate without free access of air, this operation cannot be performed in a crucible placed in the middle of the burning coals of a furnace, because the internal air, being mostly already reduced by the combustion into azotic and carbonic acid gas, is no longer fit for the oxydation of metals. It was therefore necessary to contrive a particular apparatus, in which the metal should be at the same time exposed to the influence of violent heat, and defended from contact with air rendered incombustible by its passage through burning coals. The furnace intended for answering this double purpose is called the cuppelling or essay furnace. It is usually made of a square form, as represented Pl. XIII. Fig. 8. and 10. having an ash-hole AABB, a fire-place BBCC, a laboratory CCDD, and a dome DDEE. The muffle or small oven of baked earth GH, Fig. 9. being placed in the laboratory of the furnace upon cross bars of iron, is adjusted to the opening GG, and luted with clay softened in water. The cuppels are placed in this oven or muffle, and charcoal is conveyed into the furnace through the openings of the dome and fire-place. The external air enters through the openings of the ash-hole for supporting the combustion, and escapes by the superior opening or chimney at EE; and air is admitted through the door of the muffle GG for oxydating the contained metal.

Very little reflection is sufficient to discover the erroneous principles upon which this furnace is constructed. When the opening GG is shut, the oxydation is produced slowly, and with difficulty, for want of air to carry it on; and, when this hole is open, the stream of cold air which is then admitted fixes the metal, and obstructs the process. These inconveniencies may be easily remedied, by constructing the muffle and furnace in such a manner that a stream of fresh external air should always play upon the surface of the metal, and this air should be made to pass through a pipe of clay kept continually red hot by the fire of the furnace. By this means the inside of the muffle will never be coolled, and processes will be finished in a few minutes, which at present require a considerable space of time.

Mr Sage remedies these inconveniencies in a different manner; he places the cuppel containing lead, alloyed with gold or silver, amongst the charcoal of an ordinary furnace, and covered by a small porcelain muffle; when the whole is sufficiently heated, he directs the blast of a common pair of hand-bellows upon the surface of the metal, and completes the cuppellation in this way with great ease and exactness.

SECT. III.

_Of increasing the Action of Fire, by using Oxygen Gas instead of Atmospheric Air._

By means of large burning glasses, such as those of Tchirnausen and Mr de Trudaine, a degree of heat is obtained somewhat greater than has hitherto been produced in chemical furnaces, or even in the ovens of furnaces used for baking hard porcelain. But these instruments are extremely expensive, and do not even produce heat sufficient to melt crude platina; so that their advantages are by no means sufficient to compensate for the difficulty of procuring, and even of using them. Concave mirrors produce somewhat more effect than burning glasses of the same diameter, as is proved by the experiments of Messrs Macquer and Beaumé with the speculum of the Abbé Bouriot; but, as the direction of the reflected rays is necessarily from below upwards, the substance to be operated upon must be placed in the air without any support, which renders most chemical experiments impossible to be performed with this instrument.

For these reasons, I first endeavoured to employ oxygen gas for combustion, by filling large bladders with it, and making it pass through a tube capable of being shut by a stop-cock; and in this way I succeeded in causing it to support the combustion of lighted charcoal. The intensity of the heat produced, even in my first attempt, was so great as readily to melt a small quantity of crude platina. To the success of this attempt is owing the idea of the gazometer, described p. 308. _et seq._ which I substituted instead of the bladders; and, as we can give the oxygen gas any necessary degree of pressure, we can with this instrument keep up a continued stream, and give it even a very considerable force.

The only apparatus necessary for experiments of this kind consists of a small table ABCD, Pl. XII. Fig. 15, with a hole F, through which passes a tube of copper or silver, ending in a very small opening at G, and capable of being opened or shut by the stop-cock H. This tube is continued below the table at l m n o, and is connected with the interior cavity of the gazometer. When we mean to operate, a hole of a few lines deep must be made with a chizel in a piece of charcoal, into which the substance to be treated is laid; the charcoal is set on fire by means of a candle and blow-pipe, after which it is exposed to a rapid stream of oxygen gas from the extremity G of the tube FG.

This manner of operating can only be used with such bodies as can be placed, without inconvenience, in contact with charcoal, such as metals, simple earths, &c. But, for bodies whose elements have affinity to charcoal, and which are consequently decomposed by that substance, such as sulphats, phosphats, and most of the neutral salts, metallic glasses, enamels, &c. we must use a lamp, and make the stream of oxygen gas pass through its flame. For this purpose, we use the elbowed blow-pipe ST, instead of the bent one FG, employed with charcoal. The heat produced in this second manner is by no means so intense as in the former way, and is very difficultly made to melt platina. In this manner of operating with the lamp, the substances are placed in cuppels of calcined bones, or little cups of porcelain, or even in metallic dishes. If these last are sufficiently large, they do not melt, because, metals being good conductors of heat, the caloric spreads rapidly through the whole mass, so that none of its parts are very much heated.

In the Memoirs of the Academy for 1782, p. 476. and for 1783, p. 573. the series of experiments I have made with this apparatus may be seen at large. The following are some of the principal results.

1. Rock cristal, or pure silicious earth, is infusible, but becomes capable of being softened or fused when mixed with other substances.

2. Lime, magnesia, and barytes, are infusible, either when alone, or when combined together; but, especially lime, they assist the fusion of every other body.

3. Argill, or pure base of alum, is completely fusible _per se_ into a very hard opake vitreous substance, which scratches glass like the precious stones.

4. All the compound earths and stones are readily fused into a brownish glass.

5. All the saline substances, even fixed alkali, are volatilized in a few seconds.

6. Gold, silver, and probably platina, are slowly volatilized without any particular phenomenon.

7. All other metallic substances, except mercury, become oxydated, though placed upon charcoal, and burn with different coloured flames, and at last dissipate altogether.

8. The metallic oxyds likewise all burn with flames. This seems to form a distinctive character for these substances, and even leads me to believe, as was suspected by Bergman, that barytes is a metallic oxyd, though we have not hitherto been able to obtain the metal in its pure or reguline state.

9. Some of the precious stones, as rubies, are capable of being softened and soldered together, without injuring their colour, or even diminishing their weights. The hyacinth, tho' almost equally fixed with the ruby, loses its colour very readily. The Saxon and Brasilian topaz, and the Brasilian ruby, lose their colour very quickly, and lose about a fifth of their weight, leaving a white earth, resembling white quartz, or unglazed china. The emerald, chrysolite, and garnet, are almost instantly melted into an opake and coloured glass.

10. The diamond presents a property peculiar to itself; it burns in the same manner with combustible bodies, and is entirely dissipated.

There is yet another manner of employing oxygen gas for considerably increasing the force of fire, by using it to blow a furnace. Mr Achard first conceived this idea; but the process he employed, by which he thought to dephlogisticate, as it is called, atmospheric air, or to deprive it of azotic gas, is absolutely unsatisfactory. I propose to construct a very simple furnace, for this purpose, of very refractory earth, similar to the one represented Pl. XIII. Fig. 4. but smaller in all its dimensions. It is to have two openings, as at E, through one of which the nozle of a pair of bellows is to pass, by which the heat is to be raised as high as possible with common air; after which, the stream of common air from the bellows being suddenly stopt, oxygen gas is to be admitted by a tube, at the other opening, communicating with a gazometer having the pressure of four or five inches of water. I can in this manner unite the oxygen gas from several gazometers, so as to make eight or nine cubical feet of gas pass through the furnace; and in this way I expect to produce a heat greatly more intense than any hitherto known. The upper orifice of the furnace must be carefully made of considerable dimensions, that the caloric produced may have free issue, lest the too sudden expansion of that highly elastic fluid should produce a dangerous explosion.

FINIS.

APPENDIX.

No. I.

TABLE _for Converting Lines, or Twelfth Parts of an Inch, and Fractions of Lines, into Decimal Fractions of the Inch._

Twelfth Parts Decimal Decimal of a Line. Fractions. Lines. Fractions.

1 0.00694 1 0.08333 2 0.01389 2 0.16667 3 0.02083 3 0.25000 4 0.02778 4 0.33333 5 0.03472 5 0.41667 6 0.04167 6 0.50000 7 0.04861 7 0.58333 8 0.05556 8 0.66667 9 0.06250 9 0.75000 10 0.06944 10 0.83333 11 0.07639 11 0.91667 12 0.08333 12 1.00000

No. II.

TABLE _for Converting the Observed Heighths of Water in the Jars of the Pneumato-Chemical Apparatus, expressed in Inches and Decimals, into Corresponding Heighths of Mercury._

Water. Mercury. Water. Mercury.

.1 .00737 4. .29480 .2 .01474 5. .36851 .3 .02201 6. .44221 .4 .02948 7. .51591 .5 .03685 8. .58961 .6 .04422 9. .66332 .7 .05159 10. .73702 .8 .05896 11. .81072 .9 .06633 12. .88442 1. .07370 13. .96812 2. .14740 14. 1.04182 3. .22010 15. 1.11525

No. III.

TABLE _for Converting the Ounce Measures used by Dr Priestly into French and English Cubical Inches._

Ounce French cubical English cubical measures. inches. inches.

1 1.567 1.898 2 3.134 3.796 3 4.701 5.694 4 6.268 7.592 5 7.835 9.490 6 9.402 11.388 7 10.969 13.286 8 12.536 15.184 9 14.103 17.082 10 15.670 18.980 20 31.340 37.960 30 47.010 56.940 40 62.680 75.920 50 78.350 94.900 60 94.020 113.880 70 109.690 132.860 80 125.360 151.840 90 141.030 170.820 100 156.700 189.800 1000 1567.000 1898.000

No. IV. ADDITIONAL.

TABLE _for Reducing the Degrees of Reaumeur's Thermometer into its corresponding Degrees of Fahrenheit's Scale._

R. F. R. F. R. F. R. F.

0 = 32 21 = 79.25 41 = 124.25 61 = 169.25 1 = 34.25 22 = 81.5 42 = 126.5 62 = 171.5 2 = 36.5 23 = 83.75 43 = 128.75 63 = 173.75 3 = 38.75 24 = 86 44 = 131 64 = 176. 4 = 41 25 = 88.25 45 = 133.25 65 = 178.25 5 = 43.25 26 = 90.5 46 = 135.5 66 = 180.5 6 = 45.5 27 = 92.75 47 = 137.75 67 = 182.75 7 = 47.75 28 = 95 48 = 140 68 = 185 8 = 50 29 = 97.25 49 = 142.25 69 = 187.25 9 = 52.25 30 = 99.5 50 = 144.5 70 = 189.5 10 = 54.5 31 = 101.75 51 = 146.75 71 = 191.75 11 = 56.75 32 = 104 52 = 149 72 = 194. 12 = 59 33 = 106.25 53 = 151.25 73 = 196.25 13 = 61.25 34 = 108.5 54 = 153.5 74 = 198.5 14 = 63.5 35 = 110.75 55 = 155.75 75 = 200.75 15 = 65.75 36 = 113 56 = 158 76 = 203 16 = 68 37 = 115.25 57 = 160.25 77 = 205.25 17 = 70.25 38 = 117.5 58 = 162.5 78 = 207.5 18 = 72.5 39 = 119.75 59 = 164.75 79 = 209.75 19 = 74.75 40 = 122 60 = 167 80 = 212 20 = 77

_Note_--Any degree, either higher or lower, than what is contained in the above Table, may be at any time converted, by remembering that one degree of Reaumeur's scale is equal to 2.25° of Fahrenheit; or it may be done without the Table by the following formula, R × 9 / 4 + 32 = F; that is, multiply the degree of Reaumeur by 9, divide the product by 4, to the quotient add 32, and the sum is the degree of Fahrenheit.--E.

No. V. ADDITIONAL.

RULES _for converting French Weights and Measures into correspondent English Denominations[62]._

§ 1. _Weights._

The Paris pound, poids de mark of Charlemagne, contains 9216 Paris grains; it is divided into 16 ounces, each ounce into 8 gros, and each gros into 72 grains. It is equal to 7561 English Troy grains.

The English Troy pound of 12 ounces contains 5760 English Troy grains, and is equal to 7021 Paris grains.

The English averdupois pound of 16 ounces contains 7000 English Troy grains, and is equal to 8538 Paris grains.

To reduce Paris grs. to English Troy } grs. divide by } 1.2189 To reduce English Troy grs. to Paris } grs. multiply by }

To reduce Paris ounces to English } Troy, divide by } To reduce English Troy ounces to } 1.015734 Paris, multiply by }

Or the conversion may be made by means of the following Tables.

I. _To reduce French to English Troy Weight._

The Paris pound = 7561 } The ounce = 472.5625 } English. The gros = 59.0703 } Troy. The grain = .8194 } Grains.

II. _To Reduce English Troy to Paris Weight._

The English Troy pound } = 7021. } of 12 ounces } } The Troy ounce = 585.0830 } The dram of 60 grs. = 73.1353 } Paris The penny weight, or } = 29.2540 } grains. denier, of 24 grs. } } The scruple, of 20 grs. = 24.3784 }

III. _To Reduce English Averdupois to Paris Weight._

The averdupois pound of } } 16 ounces, or 7000 } = 8538. } Paris Troy grains. } } grains. The ounce = 533.6250 }

§ 2. _Long and Cubical Measures._

To reduce Paris feet or inches into } English, multiply by } 1.065977 English feet or inches into Paris, } divide by }

To reduce Paris cubic feet or inches } to English, multiply by } English cubic feet or inches to Paris, } 1.211278 divide by }

Or by means of the following tables:

IV. _To Reduce Paris Long Measure to English._

The Paris royal foot of } } 12 inches } = 12.7977 } English The inch = 1.0659 } The line, or 1/12 of an inch = .0888 } inches. The 1/12 of a line = .0074 }

V. _To Reduce English Long Measure to French._

The English foot = 11.2596 } The inch = .9383 } The 1/8 of an inch = .1173 } Paris inches. The 1/10 = .0938 } The line, or 1/12 = .0782 }

VI. _To Reduce French Cube Measure to English._

The Paris } English { } cube foot = 1.211278 } cubical { 2093.088384 } The cubic } feet, { } inches. inch = .000700 } or { 1.211278 }

VII. _To Reduce English Cube Measure to French._

The English cube foot, } or 1728 cubical inches } = 1427.4864 } French The cubical inch = .8260 } cubical The cube tenth = .0008 } inches.

§ 3. _Measure of Capacity._

The Paris pint contains 58.145[63] English cubical inches, and the English wine pint contains 28.85 cubical inches; or, the Paris pint contains 2.01508 English pints, and the English pint contains .49617 Paris pints; hence,

To reduce the Paris pint to the English, } multiply by } 2.01508. To reduce the English pint to the } Paris, divide by }

No. VI.

TABLE _of the Weights of the different Gasses, at 28 French inches, or 29.84 English inches barometrical pressure, and at 10° (54.5°) of temperature, expressed in English measure and English Troy weight._

Names of the Gasses. Weight of a Weight of a cubical inch. cubical foot. (A) qrs. oz. dr. qrs. Atmospheric air .32112 1 1 15 Azotic gas .30064 1 0 39.5 Oxygen gas .34211 1 1 51 Hydrogen gas .02394 0 0 41.26 Carbonic acid gas .44108 1 4 41 (B) Nitrous gas .37000 1 2 39 Ammoniacal gas .18515 0 5 19.73 Sulphurous acid gas .71580 2 4 38

[Note A: These five were ascertained by Mr Lavoisier himself.--E.]

[Note B: The last three are inserted by Mr Lavoisier upon the authority of Mr Kirwan.--E.]

No. VII.

_Tables_ _of the Specific Gravities of different bodies._

§ 1. _Metallic Substances._

GOLD.

Pure gold of 24 carats melted but not hammered 19.2581 The same hammered 19.3617 Gold of the Parisian standard, 22 carats fine, not hammered(A) 17.4863 The same hammered 17.5894 Gold of the standard of French coin, 21-22/32 carats fine, not hammered 17.4022 The same coined 17.6474 Gold of the French trinket standard, 20 carats fine, not hammered 15.7090 The same hammered 15.7746

[Note A: The same with Sterling.]

SILVER.

Pure or virgin silver, 24 deniers, not hammered 10.4743 The same hammered 10.5107 Silver of the Paris standard, 11 deniers 10 grains fine, not hammered(B) 10.1752 The same hammered 10.3765 Silver, standard of French coin, 10 deniers 21 grains fine, not hammered 10.0476 The same coined 10.4077

[Note B: This is 10 grs. finer than Sterling.]

PLATINA.

Crude platina in grains 15.6017 The same, after being treated with muriatic acid 16.7521 Purified platina, not hammered 19.5000 The same hammered 20.3366 The same drawn into wire 21.0417 The same passed through rollers 22.0690

COPPER AND BRASS.

Copper, not hammered 7.7880 The same wire drawn 8.8785 Brass, not hammered 8.3958 The same wire drawn 8.5441

IRON AND STEEL.

Cast iron 7.2070 Bar iron, either screwed or not 7.7880 Steel neither tempered nor screwed 7.8331 Steel screwed but not tempered 7.8404 Steel tempered and screwed 7.8180 Steel tempered and not screwed 7.8163

TIN.

Pure tin from Cornwall melted and not screwed 7.2914 The same screwed 7.2994 Malacca tin, not screwed 7.2963 The same screwed 7.3065 Molten lead 11.3523 Molten zinc 7.1908 Molten bismuth 9.8227 Molten cobalt 7.8119 Molten arsenic 5.7633 Molten nickel 7.8070 Molten antimony 6.7021 Crude antimony 4.0643 Glass of antimony 4.9464 Molybdena 4.7385 Tungstein 6.0665 Mercury 13.5681

§ 2. _Precious Stones._

White Oriental diamond 3.5212 Rose-coloured Oriental ditto 3.5310 Oriental ruby 4.2833 Spinell ditto 3.7600 Ballas ditto 3.6458 Brasillian ditto 3.5311 Oriental topas 4.0106 Ditto Pistachio ditto 4.0615 Brasillian ditto 3.5365 Saxon topas 3.5640 Ditto white ditto 3.5535 Oriental saphir 3.9941 Ditto white ditto 3.9911 Saphir of Puy 4.0769 Ditto of Brasil 3.1307 Girasol 4.0000 Ceylon jargon 4.4161 Hyacinth 3.6873 Vermillion 4.2299 Bohemian garnet 4.1888 Dodecahedral ditto 4.0627 Syrian ditto 4.0000 Volcanic ditto, with 24 sides 2.4684 Peruvian emerald 2.7755 Crysolite of the jewellers 2.7821 Ditto of Brasil 2.6923 Beryl, or Oriental aqua marine 3.5489 Occidental aqua marine 2.7227

§ 3. _Silicious Stones._

Pure rock cristal of Madagascar 2.6530 Ditto of Brasil 2.6526 Ditto of Europe, or gelatinous 2.6548 Cristallized quartz 2.6546 Amorphous ditto 2.6471 Oriental agate 2.5901 Agate onyx 2.6375 Transparent calcedony 2.6640 Carnelian 2.6137 Sardonyx 2.6025 Prase 2.5805 Onyx pebble 2.6644 Pebble of Rennes 2.6538 White jade 2.9502 Green jade 2.9660 Red jasper 2.6612 Brown ditto 2.6911 Yellow ditto 2.7101 Violet ditto 2.7111 Gray ditto 2.7640 Jasponyx 2.8160 Black prismatic hexahedral schorl 3.3852 Black spary ditto 3.3852 Black amorphous schorl, called antique basaltes 2.9225 Paving stone 2.4158 Grind stone 2.1429 Cutler's stone 2.1113 Fountainbleau stone 2.5616 Scyth stone of Auvergne 2.5638 Ditto of Lorrain 2.5298 Mill stone 2.4835 White flint 2.5941 Blackish ditto 2.5817

§ 4. _Various Stones, &c._

Opake green Italian serpentine, or gabro of the Florentines 2.4295 Coarse Briancon chalk 2.7274 Spanish chalk 2.7902 Foliated lapis ollaris of Dauphiny 2.7687 Ditto ditto from Sweden 2.8531 Muscovy talc 2.7917 Black mica 2.9004 Common schistus or slate 2.6718 New slate 2.8535 White rasor hone 2.8763 Black and white hone 3.1311 Rhombic or Iceland cristal 2.7151 Pyramidal calcareous spar 2.7141 Oriental or white antique alabaster 2.7302 Green Campan marble 2.7417 Red Campan marble 2.7242 White Carara marble 2.7168 White Parian marble 2.8376 Various kinds of calcareous stones } from 1.3864 used in France for building. } to 2.3902 Heavy spar 4.4300 White fluor 3.1555 Red ditto 3.1911 Green ditto 3.1817 Blue ditto 3.1688 Violet ditto 3.1757 Red scintilant zeolite from Edelfors 2.4868 White scintilant zeolite 2.0739 Cristallized zeolite 2.0833 Black pitch stone 2.0499 Yellow pitch stone 2.0860 Red ditto 2.6695 Blackish ditto 2.3191 Red porphyry 2.7651 Ditto of Dauphiny 2.7033 Green serpentine 2.8960 Black ditto of Dauphiny, called variolite 2.9339 Green ditto from Dauphiny 2.9883 Ophites 2.9722 Granitello 3.0626 Red Egyptian granite 2.6541 Beautiful red granite 2.7609 Granite of Girardmas 2.7163 Pumice stone .9145 Lapis obsidianus 2.3480 Pierre de Volvic 2.3205 Touch stone 2.4153 Basaltes from Giants Causeway 2.8642 Ditto prismatic from Auvergne 2.4153 Glass gall 2.8548 Bottle glass 2.7325 Green glass 2.6423 White glass 2.8922 St Gobin cristal 2.4882 Flint glass 3.3293 Borax glass 2.6070 Seves porcelain 2.1457 Limoges ditto 2.3410 China ditto 2.3847 Native sulphur 2.0332 Melted sulphur 1.9907 Hard peat 1.3290 Ambergrease .9263 Yellow transparent amber 1.0780

§ 5. _Liquids._

Distilled water 1.0000 Rain water 1.0000 Filtered water of the Seine 1.00015 Arcueil water 1.00046 Avray water 1.00043 Sea water 1.0263 Water of the Dead Sea 1.2403 Burgundy wine .9915 Bourdeaux ditto .9939 Malmsey Madeira 1.0382 Red beer 1.0338 White ditto 1.0231 Cyder 1.0181 Highly rectified alkohol .8293 Common spirits of wine .8371

Alkohol 15 pts. water 1 part. .8527 14 2 .8674 13 3 .8815 12 4 .8947 11 5 .9075 10 6 .9199 9 7 .9317 8 8 .9427 7 9 .9519 6 10 .9594 5 11 .9674 4 12 .9733 3 13 .9791 2 14 .9852 1 15 .9919

Sulphuric ether .7394 Nitric ether .9088 Muriatic ether .7298 Acetic ether .8664 Sulphuric acid 1.8409 Nitric ditto 1.2715 Muriatic ditto 1.1940 Red acetous ditto 1.0251 White acetous ditto 1.0135 Distilled ditto ditto 1.0095 Acetic ditto 1.0626 Formic ditto .9942 Solution of caustic ammoniac, or volatil alkali fluor .8970 Essential or volatile oil of turpentine .8697 Liquid turpentine .9910 Volatile oil of lavender .8938 Volatile oil of cloves 1.0363 Volatile oil of cinnamon 1.0439 Oil of olives .9153 Oil of sweet almonds .9170 Lintseed oil .9403 Oil of poppy seed .9288 Oil of beech mast .9176 Whale oil .9233 Womans milk 1.0203 Mares milk 1.0346 Ass milk 1.0355 Goats milk 1.0341 Ewe milk 1.0409 Cows milk 1.0324 Cow whey 1.0193 Human urine 1.0106

§ 6. _Resins and Gums_

Common yellow or white rosin 1.0727 Arcanson 1.0857 Galipot(A) 1.0819 Baras(A) 1.0441 Sandarac 1.0920 Mastic 1.0742 Storax 1.1098 Opake copal 1.1398 Transparent ditto 1.0452 Madagascar ditto 1.0600 Chinese ditto 1.0628 Elemi 1.0182 Oriental anime 1.0284 Occidental ditto 1.0426 Labdanum 1.1862 Ditto _in tortis_ 2.4933 Resin of guaiac 1.2289 Ditto of jallap 1.2185 Dragons blood 1.2045 Gum lac 1.1390 Tacamahaca 1.0463 Benzoin 1.0924 Alouchi(B) 1.0604 Caragna(C) 1.1244 Elastic gum .9335 Camphor .9887 Gum ammoniac 1.2071 Sagapenum 1.2008 Ivy gum(D) 1.2948 Gamboge 1.2216 Euphorbium 1.1244 Olibanum 1.1732 Myrrh 1.3600 Bdellium 1.3717 Aleppo Scamony 1.2354 Smyrna ditto 1.2743 Galbanum 1.2120 Assafoetida 1.3275 Sarcocolla 1.2684 Opoponax 1.6226 Cherry tree gum 1.4817 Gum Arabic 1.4523 Tragacanth 1.3161 Basora gum 1.4346 Acajou gum(E) 1.4456 Monbain gum(F) 1.4206 Inspissated juice of liquorice 1.7228 ---- Acacia 1.5153 ---- Areca 1.4573 Terra Japonica 1.3980 Hepatic aloes 1.3586 Socotrine aloes 1.3795 Inspissated juice of St John's wort 1.5263 Opium 1.3366 Indigo .7690 Arnotto .5956 Yellow wax .9648 White ditto .9686 Ouarouchi ditto(G) .8970 Cacao butter .8916 Spermaceti .9433 Beef fat .9232 Veal fat .9342 Mutton fat .9235 Tallow .9419 Hoggs fat .9368 Lard .9478 Butter .9423

[Note A: Resinous juices extracted in France from the Pine. _Vide Bomare's Dict._]

[Note B: Odoriferous gum from the tree which produces the Cortex Winteranus. _Bomare._]

[Note C: Resin of the tree called in Mexico Caragna, or Tree of Madness. _Ibid._]

[Note D: Extracted in Persia and the warm countries from Hedera terrestris.--_Bomare._]

[Note E: From a Brasilian tree of this name.--_Ibid._]

[Note F: From a tree of this name.--_Ibid._]

[Note G: The produce of the Tallow Tree of Guayana. _Vide Bomare's Dict._]

§ 7. _Woods._

Heart of oak 60 years old 1.1700 Cork .2400 Elm trunk .6710 Ash ditto .8450 Beech .8520 Alder .8000 Maple .7550 Walnut .6710 Willow .5850 Linden .6040 Male fir .5500 Female ditto .4980 Poplar .3830 White Spanish ditto .5294 Apple tree .7930 Pear tree .6610 Quince tree .7050 Medlar .9440 Plumb tree .7850 Olive wood .9270 Cherry tree .7150 Filbert tree .6000 French box .9120 Dutch ditto 1.3280 Dutch yew .7880 Spanish ditto .8070 Spanish cypress .6440 American cedar .5608 Pomgranate tree 1.3540 Spanish mulberry tree .8970 Lignum vitae 1.3330 Orange tree .7050

_Note_--The numbers in the above Table, if the Decimal point be carried three figures farther to the right hand, nearly express the absolute weight of an English cube foot of each substance in averdupois ounces. See No. VIII. of the Appendix.--E.

No. VIII. ADDITIONAL.

RULES _for Calculating the Absolute Gravity in English Troy Weight of a Cubic Foot and Inch, English Measure, of any Substance whose Specific Gravity is known[64]._

In 1696, Mr Everard, balance-maker to the Exchequer, weighed before the Commissioners of the House of Commons 2145.6 cubical inches, by the Exchequer standard foot, of distilled water, at the temperature of 55° of Fahrenheit, and found it to weigh 1131 oz. 14 dts. Troy, of the Exchequer standard. The beam turned with 6 grs. when loaded with 30 pounds in each scale. Hence, supposing the pound averdupois to weigh 7000 grs. Troy, a cubic foot of water weighs 62-1/2 pounds averdupois, or 1000 ounces averdupois, wanting 106 grains Troy. And hence, if the specific gravity of water be called 1000, the proportional specific gravities of all other bodies will nearly express the number of averdupois ounces in a cubic foot. Or more accurately, supposing the specific gravity of water expressed by 1. and of all other bodies in proportional numbers, as the cubic foot of water weighs, at the above temperature, exactly 437489.4 grains Troy, and the cubic inch of water 253.175 grains, the absolute weight of a cubical foot or inch of any body in Troy grains may be found by multiplying their specific gravity by either of the above numbers respectively.

By Everard's experiment, and the proportions of the English and French foot, as established by the Royal Society and French Academy of Sciences, the following numbers are ascertained.

Paris grains in a Paris cube foot of water = 645511

English grains in a Paris cube foot of water = 529922

Paris grains in an English cube foot of water = 533247

English grains in an English cube foot of water = 437489.4

English grains in an English cube inch of water = 253.175

By an experiment of Picard with the measure and weight of the Chatelet, the Paris cube foot of water contains of Paris grains = 641326

By one of Du Hamel, made with great care = 641376

By Homberg = 641666

These show some uncertainty in measures or in weights; but the above computation from Everard's experiment may be relied on, because the comparison of the foot of England with that of France was made by the joint labours of the Royal Society of London and the French Academy of Sciences: It agrees likewise very nearly with the weight assigned by Mr Lavoisier, 70 Paris pounds to the cubical foot of water.

No. IX.

TABLES _for Converting Ounces, Drams, and Grains, Troy, into Decimals of the Troy Pound of 12 Ounces, and for Converting Decimals of the Pound Troy into Ounces, &c._

I. _For Grains._

Grains = Pound.

1 .0001736 2 .0003472 3 .0005208 4 .0006944 5 .0008681 6 .0010417 7 .0012153 8 .0013889 9 .0015625 10 .0017361

20 .0034722 30 .0052083 40 .0069444 50 .0086806 60 .0104167 70 .0121528 80 .0138889 90 .0156250

100 .0173611 200 .0374222 300 .0520833 400 .0694444 500 .0868055 600 .1041666 700 .1215277 800 .1388888 900 .1562499 1000 .1736110

2000 .3472220 3000 .5208330 4000 .6944440 5000 .8680550 6000 1.0418660 7000 1.2152770 8000 1.3888880 9000 1.5624990

II. _For Drams._

Drams = Pound.

1 .0104167 2 .0208333 3 .0312500 4 .0416667 5 .0520833 6 .0625000 7 .0729167 8 .0833333

III. _For Ounces._

Ounces = Pounds.

1 .0833333 2 .1666667 3 .2500000 4 .3333333 5 .4166667 6 .5000000 7 .5833333 8 .6666667 9 .7500000 10 .8333333 11 .9166667 12 1.0000000

IV. _Decimals of the Pound into Ounces, &c._

_Tenth parts._

lib. = oz. dr. gr.

0.1 1 1 36 0.2 2 3 12 0.3 3 4 48 0.4 4 6 24 0.5 6 0 0 0.6 7 1 36 0.7 8 3 12 0.8 9 4 48 0.9 10 6 24

_Hundredth parts._

0.01 0 0 57.6 0.02 0 1 55.2 0.03 0 2 52.8 0.04 0 3 50.4 0.05 0 4 48.0 0.06 0 5 45.6 0.07 0 6 43.2 0.08 0 7 40.8 0.09 0 3 38.4

_Thousandths._

0.001 0 0 5.76 0.002 0 0 11.52 0.003 0 0 17.28 0.004 0 0 23.04 0.005 0 0 28.80

lib. = grs.

0.006 34.56 0.007 40.32 0.008 46.08 0.009 51.84

_Ten thousandth parts._

0.0001 0.576 0.0002 1.152 0.0003 1.728 0.0004 2.304 0.0005 2.880 0.0006 3.456 0.0007 4.032 0.0008 4.608 0.0009 5.184

_Hundred thousandth parts._

0.00001 0.052 0.00002 0.115 0.00003 0.173 0.00004 0.230 0.00005 0.288 0.00006 0.346 0.00007 0.403 0.00008 0.461 0.00009 0.518

No. X.

TABLE _of the English Cubical Inches and Decimals corresponding to a determinate Troy Weight of Distilled Water at the Temperature of 55°, calculated from Everard's experiment._

_For Grains._

Grs. Cubical inches.

1 = .0039 2 .0078 3 .0118 4 .0157 5 .0197 6 .0236 7 .0275 8 .0315 9 .0354 10 .0394 20 .0788 30 .1182 40 .1577 50 .1971

_For Drams._

Drams. Cubical inches.

1 = .2365 2 .4731 3 .7094 4 .9463 5 1.1829 6 1.4195 7 1.6561

_For Ounces._

Oz. Cubical inches.

1 = 1.8927 2 3.7855 3 5.6782 4 7.5710 5 9.4631 6 11.3565 7 13.2493 8 15.1420 9 17.0748 10 18.9276 11 20.8204

_For Pounds._

Libs. Cubical inches.

1 = 22.7131 2 45.4263 3 68.1394 4 90.8525 5 113.5657 6 136.2788 7 158.9919 8 181.7051 9 204.4183 10 227.1314 50 1135.6574 100 2271.3148 1000 22713.1488

FOOTNOTES:

[62] For the materials of this Article the Translator is indebted to Professor Robertson.

[63] It is said, _Belidor Archit. Hydrog._ to contain 31 oz. 64 grs. of water, which makes it 58.075 English inches; but, as there is considerable uncertainty in the determinations of the weight of the French cubical measure of water, owing to the uncertainty of the standards made use of, it is better to abide by Mr Everard's measure, which was with the Exchequer standards, and by the proportions of the English and French foot, as established by the French Academy and Royal Society.

[64] The whole of this and the following article was communicated to the Translator by Professor Robinson.--E.

_THE PLATES_

THE END.

End of Project Gutenberg's Elements of Chemistry,, by Antoine Lavoisier