If Lead be boiled for a long time in a lixivium of fixed alkali, part of it will be dissolved.
Sulphur renders this metal refractory and scarce fusible; and the mass they form when united together is friable. Hence it appears that sulphur acts upon Lead much in the same manner as upon Tin; that is, it renders both these metals less fusible, which are naturally the most fusible of any, while it exceedingly facilitates the fusion of Silver, Copper, and Iron, metals which of themselves flow with the greatest difficulty.
Of Quick-Silver.
We treat of Quick-silver in a chapter apart, because this metallic substance cannot be classed with the metals properly so called, and yet has some properties which will not allow us to confound it with the semi-metals. The reason why Quick-silver, by the Chymists commonly called Mercury, is not reputed a metal, is, that it wants one of the essential properties thereof, to wit, malleability. When it is pure and unadulterated with any mixture, it is always fluid, and of course unmalleable. But as, on the other hand, it eminently possesses the opacity, the splendour, and, above all, the gravity of a metal, being next to Gold the heaviest of all bodies, it may be considered as a true metal, differing from the rest no otherwise than by being constantly in fusion; which we may suppose arises from its aptness to flow with such a small degree of heat, that be there ever so little warmth on earth, there is still more than enough to keep Mercury in fusion; which would become solid and malleable if it were possible to apply to it a degree of cold considerable enough for that purpose. These properties will not allow us to confound it with the semi-metals. Add, that we are not yet assured by any undoubted experiment that it can be wholly deprived of its phlogiston, as the imperfect metals may. Indeed we cannot apply the force of fire to it as could be wished: for it is so volatile that it flies off and exhales in vapours, with a much less degree of fire than is necessary to make it red-hot. The vapours of Mercury thus raised by the action of fire, being collected and united in a certain quantity, appear to be no other than true Mercury, retaining every one of its properties; and no experiment hath ever been able to shew the least change thus produced in its nature.
If Mercury be exposed to the greatest heat that it can bear without sublimation, and continued in it for several months, or even a whole year together, it turns to a red powder, which the Chymists call Mercurius Præcipitatus per se. But, to succeed in this operation, it is absolutely necessary that the heat be such as is above-specified; for this metallic substance may remain exposed to a weaker heat for a considerable number of years, without undergoing any sensible alteration.
Some Chymists fancied, that by this operation they had fixed Mercury and changed its nature; but without any reason: for if the Mercury thus seemingly transmuted be exposed to a somewhat stronger degree of fire, it sublimes and exhales in vapours as usual; and those vapours collected are nothing else but running Mercury, which has recovered all its properties without the help of any additament.
Mercury has the property of dissolving all the metals, Iron only excepted. But it is a condition absolutely necessary to the success of such dissolution, that the metalline substances be possessed of their phlogiston; for if they be calcined, Mercury cannot touch them: and hence it follows, that Mercury doth not unite with substances that are purely earthy. Such a combination of a metal with Mercury is called an Amalgam. Trituration alone is sufficient to effect it; however, a proper degree of heat also is of use.
Mercury amalgamated with a metal gives it a consistence more or less soft, and even fluid, according to the greater or smaller proportion of Mercury employed. All amalgams are softened by heat, and hardened by cold.
Mercury is very volatile; vastly more so than the most unfixed metals; moreover, the union it contracts with any metal is not sufficiently intimate to entitle the new compound resulting from that union to all the properties of the two substances united: at least with regard to their degree of fixity and volatility. From all which it follows, that the best and surest method of separating it from metals dissolved by it, is to expose the amalgam to a degree of heat sufficient to make all the Quick-silver rise and evaporate; after which the metal remains in the form of a powder, and being fused recovers its malleability. If it be thought proper to save the Quick-silver, the operation must be performed in close vessels, which will confine and collect the mercurial vapours. This operation is most frequently employed to separate Gold and Silver from the several sorts of earths and sands with which they are mixed in the ore; because these two metals, Gold especially, are of sufficient value to compensate the loss of Mercury, which is inevitable in this process: besides, as they very readily amalgamate with it, this way of separating them from every thing unmetallic is very facile and commodious.
Mercury is dissolved by acids; but with circumstances peculiar to each particular sort of acid.
The vitriolic acid, concentrated and made boiling hot, seizes on it, and presently reduces it to a kind of white powder, which turns yellow by the affusion of water, but does not dissolve in it; it is called Turbith Mineral. However, the vitriolic acid on this occasion unites with a great part of the Mercury, in such a manner that the compound is soluble in water. For if to the water which was used to wash the Turbith a fixed alkali be added, there falls instantly a russet-coloured precipitate, which is no other than Mercury separated from the vitriolic acid by the intervention of the alkali.
This dissolution of Mercury by the vitriolic acid is accompanied with a very remarkable phenomenon; which is, that the acid contracts a strong smell of volatile spirit of sulphur: a notable proof that part of the phlogiston of the Mercury hath united therewith. And yet, if the Mercury be separated by means of a fixed alkali, it does not appear to have suffered any alteration. Turbith mineral is not so volatile as pure Mercury.
The nitrous acid dissolves Mercury with ease. The solution is limpid and transparent, and as it grows cold shoots into crystals, which are a nitrous mercurial salt.
If this solution be evaporated to dryness, the Mercury remains impregnated with a little of the acid, under the form of a red powder, which hath obtained the names of Red Precipitate, and Arcanum Corallinum. This Precipitate, as well as Turbith, is less volatile than pure Mercury.
If this solution of Mercury be mixed with a solution of Copper, made likewise in the nitrous acid, and the mixture evaporated to dryness, there will remain a green powder called Green Precipitate. These precipitates are caustic and corrosive; and are used as such in surgery.
Though Mercury be dissolved more easily and completely by the nitrous acid than by the vitriolic, yet it has a greater affinity with the latter than with the former: for if a vitriolic acid be poured into a solution of Mercury in spirit of nitre, the Mercury will quit the latter acid in which it was dissolved, and join the other which was added. The same thing happens when the marine acid is employed instead of the vitriolic.
Mercury combined with spirit of salt forms a singular body; a metalline salt which shoots into long crystals, pointed like daggers. This salt is volatile, and sublimes easily without decomposition. It is moreover the most violent of all the corrosives hitherto discovered by Chymistry. It is called Corrosive Sublimate, because it must absolutely be sublimed to make the combination perfect. There are several ways of doing this: but the operation will never fail, if the Mercury be rarefied into vapours, and meet with the marine acid in a similar state.
Corrosive Sublimate is dissolved by water, but in very small quantities only. It is decompounded by fixed alkalis, which precipitate the Mercury in a reddish yellow powder, called, on account of its colour, Yellow Precipitate.
If Corrosive Sublimate be mixed with tin, and the compound distilled, a liquor comes over which continually emits abundance of dense fumes, and, from the name of its inventor, is called the Smoking Liquor of Libavius. This liquor is no other than the tin combined with the marine acid of the Corrosive Sublimate, which therefore it hath actually decompounded: whence it follows, that this acid hath a greater affinity with tin than with Mercury.
The marine acid in Corrosive Sublimate is not quite saturated with Mercury; but is capable of taking up a much greater quantity thereof. For if Corrosive Sublimate be mixed with fresh Mercury, and sublimed a second time, another compound will be produced containing much more Mercury, and less acrimonious; for which reason it is named Sweet Sublimate of Mercury, Mercurius dulcis, Aquila alba. This compound may be taken internally, and is purgative or emetic according to the dose administered. It may be rendered still more gentle by repeated sublimations, and then it takes the title of Panacea Mercurialis. No way hath hitherto been found to dissolve Mercury in aqua regis without great difficulty, and even then it is but imperfectly dissolved.
Mercury unites easily and intimately with sulphur. If these two substances be only rubbed together in a gentle heat, or even without any heat, they will contract an union, though but an incomplete one. This combination takes the form of a black powder, which has procured it the name of Æthiops Mineral.
If a more intimate and perfect union be desired, this compound must be exposed to a stronger heat; and then a red ponderous substance will be sublimed, appearing like a mass of shining needles: this is the combination desired, and is called Cinabar. In this form chiefly is Mercury found in the bowels of the earth. Cinabar finely levigated acquires a much brighter red colour, and is known to painters by the name of Vermilion.
Cinabar rises wholly by sublimation, without suffering any decomposition; because the two substances of which it consists, viz. Mercury and Sulphur, are both volatile.
Though Mercury unites and combines very well with sulphur, as hath been said, yet it hath less affinity with that mineral than any other metal, Gold only excepted: whence it follows, that any of the other metals will decompound Cinabar, by uniting with its sulphur, and so setting the Mercury at liberty to appear in its usual form. Mercury thus separated from sulphur is esteemed the purest, and bears the name of Mercury revivified from Cinabar.
Iron is generally used in this operation, preferably to the other metals, because among them all it has the greatest affinity with sulphur, and is the only one that has none with Mercury.
Cinabar may also be decompounded by means of fixed alkalis; the affinity of these salts with sulphur being generally greater than that of any metalline substance whatever.
Of the Semi-Metals.
Of Regulus of Antimony.
Regulus of Antimony is a metallic substance of a pretty bright white colour. It has the splendour, opacity, and gravity of a metal: but it is quite unmalleable, and crumbles to dust, instead of yielding or stretching, under the hammer; on which account it is classed with the Semi-metals.
It begins to flow as soon as it is moderately red; but, like the other Semi-metals, it cannot stand a violent degree of fire; being thereby dissipated into smoke and white vapours, which adhere to such cold bodies as they meet with, and so are collected into a kind of farina called Flowers of Antimony.
If Regulus of Antimony, instead of being exposed to a strong fire, be only heated so moderately that it shall not even melt, it will calcine, lose its phlogiston, and take the form of a greyish powder destitute of all splendour: this powder is called Calx of Antimony.
This calx is not volatile like the Regulus, but will endure a very violent fire; and being exposed thereto will flow, and turn to a glass of the yellowish colour of a hyacinth.
It is to be observed, that the more the Regulus is deprived of its phlogiston by continued calcination, the more refractory is the calx obtained from it. The glass thereof has also so much the less colour, and comes the nearer to common glass.
The calx and the Glass of Antimony will recover their metalline form, like every other Calx and Glass of a metal, if reduced by restoring to them their lost phlogiston. Yet if the calcination be carried too far, their reduction will become much more difficult, and a much smaller quantity of Regulus will be resuscitated.
Regulus of Antimony is capable of dissolving the metals: but its affinities with them are various, and differ according to the following order. It affects Iron the most powerfully, next Copper, then Tin, Lead, and Silver. It promotes the fusion of metals, but makes them all brittle and unmalleable.
It will not amalgamate with Mercury; and though by certain processes, particularly the addition of water and continued trituration, a sort of union between these two substances may be produced, yet it is but apparent and momentary; for, being left to themselves and undisturbed, they quickly disunite and separate[2].
The vitriolic acid, assisted by heat, and even by distillation, dissolves Regulus of Antimony. The nitrous acid likewise attacks it: but the solution can by no art be made clear and limpid: so that the Regulus is only calcined, in a manner, by this acid.
The marine acid dissolves it well enough; but then it must be exceedingly concentrated, and applied in a peculiar manner, and especially by distillation. One of the best methods of procuring a perfect union between the acid of sea-salt and Regulus of Antimony, is to pulverize the latter, mix it with corrosive sublimate, and distil the whole. There rises in the operation a white matter, thick, and scarce fluid, which is no other than the Regulus of Antimony united and combined with the acid of sea-salt. This compound is extremely corrosive, and is called Butter of Antimony.
It is plain that the corrosive sublimate is here decompounded; that the Mercury is revivified, and that the acid which was combined therewith hath quitted it to join the Regulus of Antimony, with which its affinity is greater. This Butter of Antimony by repeated distillations acquires a considerable degree of fluidity and limpidness.
If the acid of nitre be mixed with Butter of Antimony, and the whole distilled, there rises an acid liquor, or a sort of aqua regis, which still retains some of the dissolved Regulus, and is called Bezoardic Spirit of Nitre. After the distillation there remains a white matter, from which fresh spirit of nitre is again abstracted, and which being then washed with water is called Bezoar Mineral. This Bezoar Mineral is neither so volatile nor so caustic as Butter of Antimony; because the nitrous acid hath not the property of volatilizing metallic substances, as the marine acid does, and because it remains much more intimately combined with the reguline part.
If Butter of Antimony be mixed with water, the liquor immediately becomes turbid and milky, and a precipitate falls, which is nothing but the metallic matter partly separated from its acid, which is too much weakened by the addition of water to keep it dissolved. Yet this precipitate still retains a good deal of acid; for which reason it continues to be a violent emetic, and in some degree corrosive. It hath therefore been very improperly called Mercurius Vitæ.
The proper solvent of Regulus of Antimony is aqua regis; by means whereof a clear and limpid solution of this Semi-metal may be obtained.
Regulus of Antimony mixed with nitre, and projected into a red-hot crucible, sets the nitre in a flame, and makes it detonate. As it produces this effect by means of its phlogiston, it must needs at the same time be calcined, and lose its metallic properties, which accordingly happens, and when the nitre is in a triple proportion to the Regulus, the latter is so perfectly calcined as to leave only a white powder, which is fused with great difficulty, and then turns to a faintly coloured glass, not very different from common glass, and which is not reducible to a Regulus by the addition of inflammable matter; at least it yields but a very small quantity thereof. If less nitre be used, the calx is not so white; the glass it produces is more like a metalline glass, and is more easily reduced. The calx of the Regulus thus prepared by nitre is called, on account of the medicinal virtue ascribed to it, Diaphoretic Antimony, or Diaphoretic Mineral.
Nitre always becomes an alkali by deflagration, and in the present case retains part of the calx, which it even renders soluble in water. This calx may be separated from the alkali, if an acid be employed to precipitate it; and then it is called Materia Perlata. This pearly matter is a calx of Antimony, so completely deprived of its phlogiston as to be altogether incapable of reduction to a Regulus.
Regulus of Antimony readily joins and unites with sulphur, forming therewith a compound which has a very faint metallic splendour. This compound appears like a mass of long needles adhering together laterally; and under this form it is usually found in the ore, or at least when only separated by fusion from the stones and earthy matters with which the ore is mixed. It is called Crude Antimony.
Antimony flows with a moderate heat, and becomes even more fluid than other metallic substances. The action of fire dissipates or consumes the sulphur it contains, and its phlogiston also, so as to convert it into a calx and a glass, as it does the Regulus.
Aqua regis, which we observed to be the proper solvent of the Regulus, being poured on Antimony, attacks and dissolves the reguline part, but touches not the sulphur; in consequence whereof it decomposes the Antimony, and separates its sulphur from its Regulus.
There are several other ways of effecting this decomposition, and obtaining the reguline part of Antimony by itself: they consist either in destroying the sulphureous part of the Antimony by combustion, or in melting the Antimony with some substance which has a greater affinity than its reguline part with sulphur. Most metals are very fit for this latter purpose: for though the Regulus has a considerable affinity with sulphur, yet all the metals, except Gold and Mercury, have a greater.
If therefore Iron, Copper, Lead, Silver, or Tin, be melted with Antimony, the metal employed will unite with the sulphur, and separate it from the Regulus.
It must be observed, that, as these metals have some affinity with the Regulus of Antimony, the Regulus will be joined in the operation by some of the metal employed as a Precipitant, (so those substances are called which serve as the means of separating two bodies from each other); and therefore the Regulus procured in this manner will not be absolutely pure: on this account care is taken to distinguish each by adding the name of the metal employed in its precipitation; and thence come these titles, Martial Regulus of Antimony, or only Martial Regulus, Regulus Veneris; and so of the rest.
Antimony is employed with advantage to separate Gold from all the other metals with which it may be alloyed. It has been shewn, that all the metals have a greater affinity than the reguline part of Antimony with sulphur, Gold only excepted; which is incapable of contracting any union therewith: and therefore, if a mass compounded of Gold and several other metals be melted with Antimony, every thing in that mass which is not Gold will unite with the sulphur of the Antimony. This union occasions two separations, to wit, that of the sulphur of the Antimony from its reguline part, and that of the Gold from the metals with which it was adulterated; and from the whole two new compounds arise; namely, a combination of the metals with the sulphur, which being lightest rises to the surface in fusion; and a metalline mass, formed of the Gold and the reguline part of the Antimony united together, which being much the heaviest sinks to the bottom. There is no difficulty in parting the Gold from the Regulus of Antimony with which it is alloyed: for the metalline mass needs only be exposed to a degree of fire capable of dissipating into vapours all the Semi-metal it contains; which being very volatile, the operation is much easier, and more expeditiously finished, than if the metals with which the Gold was debased were to be vitrified on the cupel; without taking into the account, that, if Silver were one of them, recourse must needs be had to the process of quartation after that of the cupel.
If equal parts of nitre and Antimony be mixed together, and the mixture exposed to the action of fire, a violent detonation ensues; the nitre deflagrating consumes the sulphur of the Antimony, and even a part of its phlogiston. After the detonation there remains a greyish matter which contains fixed nitre, vitriolated tartar, and the reguline part of the Antimony in some measure deprived of its phlogiston, and half vitrified by the action of the fire, which is considerably increased by the deflagration. This matter is called Liver of Antimony.
If, instead of equal parts of nitre and Antimony, two parts of the former be used to one of the latter, then the reguline part loses much more of its phlogiston, and remains in the form of a yellowish powder.
Again, if three parts of nitre be taken to one of Antimony, the Regulus is thereby entirely robbed of its phlogiston, and converted to a white calx, which bears the name of Diaphoretic Antimony, or Diaphoretic Mineral. The pearly matter may be precipitated by pouring an acid on the saline substances which here remain after the detonation, in the same manner as we shewed above was to be done with regard to the Regulus.
In the two last operations, where the nitre is in a double or triple proportion to the Antimony, the reguline part is found after the detonation to be converted into a calx, and not into a half-vitrified matter, which we have seen is the effect when equal parts only of nitre and Antimony are used. The reason of this difference is, that in these two cases the reguline part, being wholly, or almost wholly, deprived of its phlogiston, becomes, as was observed, more difficult to fuse, and consequently cannot begin to vitrify in the same degree of heat as that which hath not lost so much of its phlogiston. If, instead of performing the operation with equal parts of nitre and Antimony alone, a portion of some substance which abounds with phlogiston be added, in that case the sulphur only of the Antimony will be consumed, and the Regulus will remain united with its phlogiston and separated from its sulphur.
The Regulus prepared in this manner is absolutely pure, because no metalline substance being employed, none can mix with and adulterate it. It is called Regulus of Antimony per se, or only Regulus of Antimony.
It is true indeed that in this operation much of the reguline part unavoidably loses its phlogiston and is calcined, and consequently a much smaller quantity of Regulus is obtained than when metalline precipitants are employed: but this loss is easily repaired, if it be thought proper, by restoring to the calcined part its lost phlogiston.
Antimony melted with two parts of fixed alkali yields no Regulus, but is entirely dissolved by the salt, and forms with it a mass of a reddish yellow colour.
The reason why no precipitate is produced on this occasion is, that the alkali uniting with the sulphur of the Antimony forms therewith the combination called Liver of Sulphur, which by its nature is qualified to keep the reguline part dissolved. This mass formed by the union of the Antimony with the alkali is soluble in water. If any acid whatever be dropt into this solution, there falls a precipitate of a reddish yellow colour; because the acid unites with the alkali, and forces it to quit the matters with which it was combined. This precipitate is called Golden Sulphur of Antimony.
As in the operation for preparing Regulus of Antimony per se, some of the nitre is, by the inflammable matters added thereto, turned to an alkali, this alkali seizes on part of the Antimony, and therewith forms a compound like that just described. Hence it comes, that if the scoria formed in this process be dissolved in water, and an acid dropped into the solution, a true golden sulphur of Antimony is thereby separated.
This union of Antimony with an alkali may also be brought about by the humid way; that is, by making use of an alkali resolved into a liquor, and boiling the mineral in it. The alkaline liquor, in proportion as it acts upon the Antimony, gradually becomes reddish and turbid. If left to settle and cool when well saturated therewith, it gradually deposites the Antimony it had taken up, which precipitates in the form of a red powder; and this precipitate is the celebrated remedy known by the name of Kermes Mineral. It is plain that the kermes is nearly the same thing with the golden sulphur: yet it differs from it in some respects; and especially in this, that being taken inwardly it operates much more gently than the golden sulphur, which is a violent emetic. Nitre fixed by charcoal, and resolved into a liquor, is the only alkali employed in preparing the kermes.
It was shewn above, that Regulus of Antimony mixed and distilled with corrosive sublimate decompounds it, disengages the Mercury, and joining itself to the marine acid forms therewith a new combination, called Butter of Antimony. If the same operation be performed with crude Antimony instead of its Regulus, the same effects are produced: but then the Antimony itself is also decomposed; that is, the reguline part is separated from the sulphur, which being set free unites with the Mercury, now also at liberty, and these two together form a true cinabar, called Cinabar of Antimony.
Of Bismuth.
Bismuth, known also by the name of Tin-glass, is a semi-metal, having almost the same appearance as Regulus of Antimony; yet it has a more dusky cast, inclining somewhat to red, and even presents some changeable streaks, especially after lying long in the air.
When exposed to the fire it melts long before it is red, and consequently with less heat than Regulus of Antimony, which does not flow, as was shewn above, till it begin to be red-hot. It becomes volatile, like all the other semi-metals, when acted on by a violent fire: being kept in fusion by a proper degree of heat it loses its phlogiston with its metallic form, and turns to a powder or a calx; and that again is converted into glass by the continued action of fire. The calx and glass of Bismuth may be reduced, like any other metallic calx, by restoring their phlogiston.
Bismuth mixes with all the metals in fusion, and even facilitates the fusion of such as do not otherwise flow readily. It whitens them by its union, and destroys their malleability.
It amalgamates with Mercury, if they be rubbed together with the addition of water: yet after some time these two metalline substances desert each other, and the Bismuth appears again in the form of a powder. Hence it is plain, that the union it contracts with Mercury is not perfect; and yet it has the singular property of attenuating Lead, and altering it in such a manner that it afterwards amalgamates with Mercury much more perfectly, so as even to pass with it through shamoy leather without any separation. The Bismuth employed in making this amalgama afterwards separates from it spontaneously, as usual; but the Lead still continues united with the Mercury, and always retains the property thus acquired.
The vitriolic acid does not dissolve Bismuth: its proper solvent is the nitrous acid, which dissolves it with violence, and abundance of fumes.
Bismuth dissolved in the nitrous acid is precipitated not only by alkalis, but even by the bare addition of water. This precipitate is extremely white, and known by the name of Magistery of Bismuth.
The acid of sea-salt and aqua regis likewise act upon Bismuth, but with less violence.
This semi-metal does not sensibly deflagrate with nitre; yet it is quickly deprived of its phlogiston, and turned into a vitrifiable calx, when exposed with it to the action of fire.
It readily unites with sulphur in fusion, and forms therewith a compound which appears to consist of needles adhering laterally to each other.
It may be separated from the sulphur with which is combined, by only exposing it to the fire, without any additament; for the sulphur is either consumed or sublimed, and leaves the Bismuth behind.
Of Zinc.
Zinc to appearance differs but little from Bismuth, and has even been confounded with it by several authors. Nevertheless, besides that it has something of a blueish cast, and is harder than Bismuth, it differs from it essentially in its properties, as will presently be shewn. These two metallic substances scarce resemble each other in any thing, but the qualities common to all semi-metals.
Zinc melts the moment it grows red in the fire, and then also begins to turn to a calx, which, like any other metallic calx, may be reduced by means of the phlogiston: but if the fire be considerably increased, it sublimes, flames, and burns like an oily matter; which is a proof of the great quantity of phlogiston in its composition. At the same time abundance of flowers rise from it in the form of white flakes, flying about in the air like very light bodies; and into this form may the whole substance of the Zinc be converted. Several names have been given to these flowers, such as Pompholyx, Philosophic Wool. They are supposed to be no other than the Zinc itself deprived of its phlogiston; yet no body has hitherto been able to resuscitate them in the form of Zinc, by restoring their phlogiston according to the methods used in the reduction of metals. Though they rise in the air with very great ease while the Zinc is calcining, yet when once formed they are very fixed; for they withstand the utmost violence of fire, and are capable of being vitrified, especially if joined with a fixed alkali. They are soluble in acids.
Zinc unites with all metalline substances, except Bismuth. It has this singular property, that being mixed with Copper, even in a considerable quantity, such as a fourth part, it does not greatly lessen the ductility thereof, and at the same time communicates to it a very beautiful colour not unlike that of Gold: on which account the composition is frequently made, and produces what is called Brass. This metal melts much more easily than Copper alone, because of the Zinc with which it is alloyed. If it be exposed to a great degree of heat, the Zinc which it contains takes fire, and sublimes in white flowers, just as when it is pure.
It is to be observed, that Brass is ductile only while it is cold, and not then, unless the Zinc used in making it was very pure; otherwise the composition will prove but a Tombac or Prince's Metal, having very little malleability.
Zinc is very volatile, and carries off with it any metallic substance with which it is fused, making a kind of sublimate thereof. In the furnaces where they smelt ores containing Zinc, the matter thus sublimed is called Cadmia Fornacum, to distinguish it from the native Cadmia called also Calamine, or Lapis Calaminaris; which, properly speaking, is an ore of Zinc, containing a great deal of that semi-metal, together with some Iron, and a stony substance. The name of Cadmia Fornacum is not appropriated solely to the metallic sublimates procured by means of Zinc, but is given in general to all the metallic sublimates found in smelting houses.
If a violent and sudden heat be applied to Zinc, it sublimes in its metalline form; there not being time for it to burn and be resolved into flowers.
This semi-metal is soluble in all the acids, but especially in spirit of nitre, which attacks and dissolves it with very great violence.
Zinc has a greater affinity than iron or copper with the vitriolic acid; and therefore it decompounds the green and blue vitriols, precipitating those two metals by uniting with the vitriolic acid, with which it forms a metallic salt, or vitriol, called White Vitriol, or Vitriol of Zinc.
Nitre mixed with Zinc, and projected into a red-hot crucible, detonates with violence, and during the detonation there rises a great quantity of white flowers, like those which appear when it is calcined by itself.
Sulphur has no power over Zinc. Even liver of sulphur, which dissolves all other metallic substances, contracts no union with this semi-metal.
Messrs. Hellot and Malouin have bestowed a great deal of pains on this semi-metal. An account of their experiments is to be found in the Memoirs of the Academy of Sciences.
Of Regulus of Arsenic.
Regulus of Arsenic is the most volatile of all the semi-metals. A very moderate heat makes it wholly evaporate, and fly off in fumes; on which account it cannot be brought to fusion, nor can any considerable masses thereof be obtained. It has a metallic colour, somewhat resembling Lead; but it soon loses its splendour when exposed to the air.
It unites readily enough with metallic substances, having the same affinities with them as Regulus of Antimony hath. It makes them brittle, and unmalleable. It hath also the property of rendering them volatile, and greatly facilitates their scorification.
It very easily parts with its phlogiston and its metallic form. When exposed to the fire it rises in a kind of shining crystalline calx, which, on that account, looks more like a saline matter than a metallic calx. To this calx or these flowers are given the names of White Arsenic, Crystalline Arsenic, and most commonly plain Arsenic.
The properties of this substance are very singular, and extremely different from those of any other metallic calx. Hitherto it hath been but little examined; and this led me to make some attempts towards discovering its nature, which may be seen in the Memoirs of the Academy of Sciences.
Arsenic differs from every other metalline calx, first, in being volatile; whereas the calces of all other metallic substances, not excepting those of the most volatile semi-metals, such as Regulus of Antimony and Zinc, are exceeding fixed; and, secondly, in having a saline character, which is not found in any other metalline calx.
The saline character of Arsenic appears, first, from its being soluble in water; secondly, from its corrosive quality, which makes it one of the most violent poisons: a quality from which the other metallic substances are free, when they are not combined with some saline matter. Regulus of Antimony must however be excepted. But then the best Chymists agree that this semi-metal is either nearly of the same nature with Arsenic, or contains a portion thereof in its composition: besides, its noxious qualities never discover themselves so plainly as when it is combined with some acid. Lastly, Arsenic acts just like the vitriolic acid upon nitre; that is, it decompounds that neutral salt, by expelling its acid from its alkaline basis, of which it takes possession, and therewith forms a new saline compound.
This combination is a species of salt that is perfectly neutral. When the operation is performed in a close vessel, the salt shoots into crystals in the form of right-angled quadrangular prisms, terminated at each extremity by pyramids that are also quadrangular and right angled; some of which however, instead of ending in a point, are obtuse as if truncated. The consequence is different when the operation is performed in an open vessel; for then nothing is obtained but an alkaline salt impregnated with Arsenic, which cannot be crystallized.
The cause of this different effect is, that, when the Arsenic is once engaged in the alkaline basis of the nitre, it can never be separated from it by the utmost force of fire, so long as it is kept in a close vessel; whereas, if you expose it to the fire without that precaution, it readily separates from it. This property of arsenic was never before observed by any Chymist, and therefore this our new species of Neutral arsenical salt was absolutely unknown till lately.
This new salt possesses many singular properties, the chief of which are these. First, it cannot be decompounded by the intervention of any acid, even the strongest acid of vitriol; and this, joined to its property of expelling the nitrous acid from its basis, shews that it has a very great affinity with fixed alkalis.
Secondly, this very salt, on which pure acids have no effect, is decompounded with the greatest ease by acids united with metallic substances. The reason of this phenomenon is curious, and furnishes us with an instance of what we advanced concerning double affinities.
If to a resolution of any metallic substance whatever, made by any acid whatever, (except that of Mercury by the marine acid, and that of Gold by aqua regis), a certain quantity of our New Salt dissolved in water be added, the metallic substance is instantaneously separated from the acid in which it was dissolved, and falls to the bottom of the liquor.
All metallic precipitates obtained in this manner are found to be a combination of the metal with Arsenic; whence it necessarily follows that the new Neutral Salt is by this means decompounded, its arsenical part uniting with the metallic substance, and its alkaline basis with the acid in which that substance was dissolved.
The affinities of these several bodies must be considered as operating on this occasion in the following manner: The acids which tend to decompound the Neutral Salt of Arsenic, by virtue of their affinity with its alkaline basis, are not able to accomplish it, because this affinity is powerfully counteracted by that which the Arsenic has with the same alkaline basis, and which is equal or even superior to theirs. But if these acids happen to be united with a substance which naturally has a very great affinity with the arsenical part of the Neutral Salt, then, the two parts of which this Salt consists being drawn different ways by two several affinities tending to separate them from each other, the Salt will undergo a decomposition, which could not have been effected without the help of this second affinity. Now, as metallic substances have a great affinity with Arsenic, it is not surprising that the Neutral Salt of Arsenic, which cannot be decompounded by a pure acid, should nevertheless yield to an acid combined with a metal. The decomposition of this Salt, therefore, and the precipitation which of course it produces in metallic solutions, are brought about by the means of a double affinity; namely, that of the acid with the alkaline basis of the Neutral Salt, and that of the metal with the arsenical part of that salt.
Arsenic has not the same effect on sea-salt as on nitre, and cannot expel its acid: a very singular phenomenon, for which it is hard to assign a reason; for the nitrous acid is known to have a greater affinity than the marine acid with alkalis, and even with the basis of sea-salt itself.
Yet Arsenic may be combined with the basis of sea-salt, and a Neutral Salt thereby obtained, like that which results from the decomposition of nitre by Arsenic: but for that purpose a quadrangular nitre must be first prepared, and Arsenic applied thereto as to common nitre.
The Salt produced by uniting Arsenic with the basis of sea-salt very much resembles the Neutral Salt of Arsenic above treated of as well in the figure of its crystals as in its several properties.
Arsenic presents another singular phenomenon, both with the alkali of nitre and with that of sea-salt; which is, that if it be combined with these salts in a fluid state, it forms with them a saline compound, quite different from the Neutral Salts of Arsenic which result from the decomposition of nitrous salts.
This saline compound, which I call Liver of Arsenic, takes up a much greater quantity of Arsenic than is necessary for the perfect saturation of the alkali. It has the appearance of a glue, which is so much the thicker the more Arsenic it contains. Its smell is disagreeable; it attracts the moisture of the air, and does not crystallize; it is easily decompounded by any acid whatever, which precipitates the Arsenic and unites with the alkali. Lastly, the effects it produces on metallic solutions are different from those of our neutral arsenical salts. But the bounds which I have set myself in this treatise will not allow me to be more particular. Such as have the curiosity to inquire further into the subject may consult my Dissertations on Arsenic, published among the Memoirs of the Academy of Sciences.
Arsenic is easily reduced to a Regulus. It need only be mixed with any matter containing the phlogiston, and by the help of a moderate heat a true Regulus will sublime. This Regulus, as was said, is very volatile, and calcines with the greatest ease; which is the reason why it cannot be obtained but in small quantities, and also why, in order to obtain masses of it, some have thought of adding thereto some metal with which it has a great affinity, such as Copper or Iron; because, by joining with the metal, it is partly fixed and restrained from flying off. But it is plain the Regulus obtained by this means is not pure, as it must partake considerably of the metal employed.
Arsenic readily unites with sulphur, and rises with it in a yellow compound, called Orpiment.
Sulphur cannot be separated from Arsenic but by the intervention of two bodies only; to wit, a fixed alkali and Mercury.
The property which Mercury possesses of separating sulphur from Arsenic is founded on this, that these two metallic substances are incapable of contracting any union; whereas, though most of the other metals and semi-metals have a greater affinity with sulphur than Mercury hath, as was shewn in treating of the decomposition of Cinabar, nevertheless they are all unable to decompound Orpiment; because some of them have as great an affinity with Arsenic as with sulphur; others have no affinity with either; and lastly, sulphur hath as great an affinity with Arsenic as with any of them.
It must be observed that, if fixed alkalis be employed to purify Arsenic in this manner, no more must be used than is necessary to absorb the sulphur or the phlogiston, of which also it is their nature to deprive Arsenic; for otherwise, as it has been shewn that Arsenic readily unites with alkalis, they would absorb a considerable quantity thereof.
Of Oil in general.
Oil is an unctuous body, which burns and consumes with flame and smoke, and is not soluble in water. It consists of the phlogiston united with water by means of an acid. There is, moreover, in its composition a certain proportion of earth, more or less, according to each several sort of Oil.
The inflammability of Oil evidently proves that it contains the phlogiston. That an acid is one of its constituent principles many experiments demonstrate, of which these are the chief: If certain Oils be long triturated with an alkaline salt, and the alkali afterwards dissolved in water, crystals of a true neutral salt will be produced: some metals, and particularly Copper, are corroded and rusted by Oils, just as they are by acids: again, acid crystals are found in some Oils that have been long kept. This acid in Oil serves undoubtedly to unite its phlogiston with its water; because these two substances having no affinity with each other cannot be united without the intervention of such a medium as an acid, which has an affinity with both. As to the existence of water in Oils, it appears plainly when they are decomposed by repeated distillations, especially after mixing them with absorbent earths. Lastly, when an Oil is destroyed by burning, a certain quantity of earth is constantly left behind.
We are very sure that the above-mentioned principles enter into the composition of Oils; for they may be obtained from every one of them: but it is not absolutely certain that they consist of these only, and that they do not contain some other principle which may escape our notice in decomposing them; for hitherto it doth not appear, by any experiment we can depend on, that Oil was ever produced by combining together the principles here specified: yet such redintegrations are the only means we have of satisfying ourselves that we know all the principles which constitute a body.
Oils exposed to the fire in close vessels pass over almost wholly from the containing vessel into any other applied to receive them. There remains, however, a small quantity of black matter, which is extremely fixed, and continues unalterable as long as it hath no communication with the external air, be the force of the fire ever so violent. This matter is no other than part of the phlogiston of the Oil united with its most fixed and grossest earth; and this is what we called Charcoal, or plainly a Coal.
Of Charcoal.
When Oil happens to be united to much earth, as it is in vegetable and animal bodies, it leaves a considerable quantity of Coal or charred matter.
This Coal, exposed to the fire in the open air, burns and wastes, but without blazing like other combustible matters: there appears only a small blueish flame, but not the least smoke. Most commonly it only glows and sparkles, and so gradually falls into ashes, which are nothing but the earth of the body, combined with an alkaline salt in burning. This alkaline salt may be separated from the earth, by lixiviating the ashes with water, which dissolves all the salt, and leaves the earth quite pure.
Charcoal is unalterable and indestructible by any other body but fire; whence it follows, that when it is not actually kindled and ignited, the most powerful agents, such as the acids, though ever so strong and concentrated, have not the least effect on it.
The case is otherwise when it is lighted, that is, when its phlogiston begins to separate from its earth; for then the pure acid of vitriol being joined therewith, contracts an instantaneous union with its phlogiston, and evaporates in a volatile sulphureous spirit. If the vitriolic acid, instead of being applied quite pure, be first clogged with some basis, especially an alkaline one, it quits that basis, enters into a more intimate union with the phlogiston of the burning Coal, and so forms an actual sulphur, with which the alkali now unites and forms a hepar.
The pure acid of sea-salt hath not been observed to act in the least upon Charcoal, especially when it is not on fire. But when this acid is incorporated with an alkaline or metallic basis, and combined according to a peculiar process with burning Charcoal, it in like manner quits its basis, unites with the phlogiston, and therewith forms a phosphorus, of which we have already taken notice.
Nor has the pure nitrous acid any effect on a charred Coal, even when ignited: and so far is it from being able to kindle a cold one, that when poured on a live one, it extinguishes it like water. But when this acid is united with a basis, it quits it rapidly as soon as it touches a burning coal, and rushes violently into an union with the phlogiston thereof. From this union there probably arises, as we said before, a kind of sulphur or phosphorus, which is so inflammable as to be destroyed by the fire the very moment it is generated.
The acids of nitre and vitriol act upon Oils; but very differently, according to the quantity of phlegm they contain. If they be weakened with much water, they have no effect at all upon Oils; if they contain little water, or be dephlegmated to a certain degree, they dissolve them with heat, and with them form compounds of a thick consistence. Acids, thus combined in a considerable proportion with Oils, render them soluble in water.
Of Soap.
Alkalis also have the same property. When an Oil is combined with an acid or an alkali in such a manner, that the compound resulting from their union is soluble in water; such a compound may in general be called a Soap. Soap itself hath the property of rendering fat bodies in some measure soluble in water; on which account it is very useful for scouring or cleansing any thing greasy.
Oily and saline substances, combined together, observe the same general rules as all other combinations; that is, they mutually communicate the properties belonging to each: thus Oils, which naturally are not soluble in water, acquire, by their union with saline matters, the property of dissolving therein; and salts lose, by their conjunction with Oils, part of their natural tendency to incorporate with water; so that, while they serve to constitute soap, they do not, as before, attract the moisture of the air, &c. and, in like manner, as they are not inflammable, they considerably lessen the inflammability of the Oils combined with them.
Acid Soaps are decompounded by alkalis, as alkaline Soaps are by acids, according to the general rules of affinities.
The acids of nitre and vitriol, when highly concentrated, dissolve Oils with such violence as to heat them, make them black, burn them, and even set them on fire. How sea-salt affects Oils is not yet sufficiently ascertained.
All Oils have the property of dissolving sulphur; which is not at all surprising, seeing each of its component principles hath an affinity with Oil.
It is also a property common to all Oils to become more fluid, subtile, light, and limpid, the oftener they are distilled. On the contrary, by being incorporated with saline substances they acquire a greater consistence, and sometimes form compounds that are most solid.
Of the several Sorts of Oils.
Oils are distinguished by the substances from which they are drawn: and as Oils are extracted from minerals, from vegetables, and from animals, there are of course Mineral, Vegetable, and Animal Oils.
Of Mineral Oils.
In the bowels of the earth we find but one sort of Oil, called Petroleum: its smell is strong and not disagreeable, and its colour sometimes more sometimes less yellow. There are certain mineral substances which yield by distillation a great deal of Oil very like Petroleum. This sort of substance is called a Bitumen, and is, indeed, nothing but an Oil rendered consistent and solid by being combined with an acid; as appears from hence, that by uniting Petroleum with the acid of vitriol we can produce an artificial Bitumen very like the native.
Of Vegetable Oils.
Vegetable substances yield a very great quantity and variety of oils: for there is not a plant, or part of a plant, that does not contain one or more sorts thereof, generally peculiar to itself, and different from all others.
By expression only, that is, by bruising and squeezing vegetable substances, particularly certain fruits and seeds, a sort of oil is obtained which has scarce any smell or taste. Oils of this sort are very mild and unctuous; and, because in this respect they resemble animal fat more than the rest do, they are called Fat Oils.
These Oils, being exposed to the air for some time, sooner or latter grow thick, acquire an acrid taste, and a strong disagreeable smell. Some of them congeal with the smallest degree of cold. This sort of Oil is well adapted to dissolve those preparations of Lead called Litharge and Minium, with which they form a thick tenacious substance, that is used for the basis of almost all plasters. They also dissolve Lead in its metalline form; but not so easily as the sorts of calx above-mentioned; probably because its body is not so much opened, nor its parts so divided.
By expression alone we also procure from certain vegetable substances another sort of Oil, which is thin, limpid, volatile, of a pungent taste, and retains the smell of the vegetable that yielded it; on which account it is called an Essential Oil. Of this there are several sorts, differing from one another, like the Fat Oils, according to the subjects from which they are obtained.
We must observe, that it is very difficult, or rather in most cases impossible, to force from the greatest part of vegetables, by expression only, all the essential Oil they contain. For this purpose therefore recourse must be had to fire: a gentle heat, not exceeding that of boiling water, will extract all the essential Oils of vegetables; and this is the most usual and most convenient way of procuring them.
The fat Oils cannot be obtained by the same method: these being much less volatile than the essential Oils, require a much greater degree of heat to raise them; which nevertheless they cannot bear without being much spoiled and entirely changed in their nature, as shall presently be shewn. All Oils, therefore, which rise with the heat of boiling water, and such alone, should be called Essential Oils.
Essential Oils, in a longer or shorter time, according to the nature of each, lose the fragrant smell they had when newly distilled, and acquire another, which is strong, rancid, and much less agreeable: they also lose their tenuity, becoming thick and viscid; and in this state they greatly resemble those substances abounding in Oil which flow from certain trees, and which are called Balsams or Resins, according as they are less or more consistent.
Balsams and Resins are not soluble in water. But there are other Oily compounds which likewise run from trees; and, though not unlike Resins, are however soluble in water. These are called Gums; and their property of dissolving in water arises from their containing more water and more salt than Resins have; or at least their saline parts are less clogged and more disengaged.
Balsams and Resins distilled with the heat of boiling water yield great quantities of a limpid, subtile, odoriferous, and, in one word, essential Oil. In the still there remains a substance thicker and more consistent than the Balsam or Resin was before distillation. The same thing happens to essential Oils which by length of time have acquired a consistence and are grown resinous. If they be re-distilled, they recover their former tenuity, leaving behind them a remainder thicker and more resinous than they themselves were. This second distillation is called the Rectification of an Oil.
It must be observed, that an essential Oil, combined with an acid strong enough to dissolve it, immediately becomes as thick and resinous, in consequence of this union, as if it had been long exposed to the air: which proves the consistence an Oil acquires by long keeping to be owing to this, that its lightest and less acid parts being evaporated, the proportion of its acid to the remainder is so increased, that it produces therein the same change, as an additional acid mixed with the Oil would have wrought before the evaporation.
This also shews us, that Balsams and Resins are only essential Oils combined with a great proportion of acid, and thereby thickened.
If vegetable substances, from which no more essential Oil can be drawn by the heat of boiling water, be exposed to a stronger heat, they yield an additional quantity of Oil; but it is thicker and heavier than the essential Oil. These Oils are black, and have a very disagreeable burnt smell, which hath made them be called Fetid or Empyreumatic Oils. They are moreover very acrid.
It must be observed, that, if a vegetable substance be exposed to a degree of heat greater than that of boiling water, before the fat or the essential Oil is extracted from it, an empyreumatic Oil only will then be obtained; because both the fat and essential Oils, when exposed to the force of fire, are thereby burnt, rendered acrid, acquire a smell of the fire, and, in a word, become truly empyreumatic. There is ground to think, that an empyreumatic Oil is nothing else but an essential or fat Oil burnt and spoiled by the fire, and that no other Oil besides these two exists naturally in vegetables.
Empyreumatic Oils, distilled and rectified several times by a gentle heat, acquire by every distillation a greater degree of tenuity, lightness, and limpidity. By this means also they lose something of their disagreeable odour; so that they gradually come nearer and nearer to the nature of essential Oils: and if the rectifications be often enough repeated, ten or twelve times for instance, they become perfectly like those Oils; except that their smell will never be so agreeable, nor like that of the substances from which they were obtained.
Fat Oils may also be brought by the same means to resemble essential Oils: but neither essential nor empyreumatic Oils are capable of acquiring the properties of fat Oils.
Of Animal Oils.
Distillation procures us considerable quantities of Oil from all the parts of animal bodies, and especially from their fat. This Oil at first is not very fluid, and is extremely fetid: but by many rectifications it gradually acquires a great degree of clearness and tenuity, and at the same time loses much of its disagreeable odour. Animal Oils, thus rendered thin and fluid by a great number of rectifications, have the reputation of being an excellent medicine, and a specific in the epilepsy.
Of Fermentation in general.
By Fermentation is meant an intestine motion, which, arising spontaneously among the insensible parts of a body, produces a new disposition and a different combination of those parts.
To excite a Fermentation in a mixt body, it is necessary, first, that there be in the composition of that mixt a certain proportion of watery, saline, oily, and earthy parts: but this proportion is not yet sufficiently ascertained. Secondly, it is requisite that the body to be fermented be placed in a certain degree of temperate heat: for much cold obstructs fermentation; and too much heat decomposes bodies. Lastly, the concurrence of the air is also necessary to fermentation.
All vegetable and animal substances are susceptible of Fermentation, because all of them contain in a due proportion the principles above specified. However, many of them want the proper quantity of water, and cannot ferment while they remain in such a state of dryness. But it is easy to supply that defect, and so render them very apt to ferment.
With respect to minerals properly so called, (that is, excluding such vegetable and animal substances as may have lain long buried in the earth), they are not subject to any Fermentation; at least, that our senses can perceive.
There are three sorts of Fermentation, distinguished from one another by their several productions. The first produces wines and spirituous liquors; for which reason it is called the Vinous or Spirituous Fermentation: the result of the second is an acid liquor; and therefore it is called the Acetous Fermentation: and the third generates an alkaline salt; which, however, differs from the alkaline salts hitherto treated of, in this respect chiefly, that, instead of being fixed, it is extremely volatile: this last sort takes the name of the Putrid or Putrefactive Fermentation. We shall now consider these three sorts of Fermentation and their effects a little more particularly.
These three sorts of Fermentation may take place successively in the same subject; which proves them to be only three different degrees of fermentation, all proceeding from one and the same cause, rather than three distinct fermentations. These degrees of fermentation always follow the order in which we have here placed them.
Of the Spirituous Fermentation.
The juices of almost all fruits, all saccharine vegetable matters, all farinaceous seeds and grains of every kind, being diluted with a sufficient quantity of water, are proper subjects of Spirituous Fermentation. If such liquors be exposed, in vessels slightly stopped, to a moderate degree of heat, they begin in some time to grow turbid; there arises insensibly a small commotion among their parts, attended with a hissing noise; this by little and little increases, till the grosser parts appear, like little seeds or grains, moving to and fro, agitated among themselves, and thrown up to the surface. At the same time some air bubbles rise, and the liquor acquires a pungent, penetrating smell, occasioned by the very subtile vapours which exhale from it.
These vapours have never yet been collected, in order to examine their nature; and they are known only by their noxious effects. They are so actively pernicious, that if a man comes rashly into a close place, where large quantities of liquors are fermenting, he suddenly drops down and expires, as if he were knocked on the head.
When these several phenomena, begin to go off, it is proper to stop the fermentation, if a very spirituous liquor be required: for if it be suffered to continue longer, the liquor will become acid, and from thence proceed to its last stage, that is, to putrefaction. This is done by stopping the containing vessels very close, and removing them into a cooler place. Then the impurities precipitate, and settling at the bottom leave the liquor clear and transparent: and now the palate discovers that the sweet saccharine taste it had before fermentation is changed to an agreeable pungency, which is not acid.
Liquors thus fermented are in general called Wines: for though in common life that word properly signifies the fermented juice of grapes only, and particular names are given to the fermented juices of other vegetable substances; as that obtained from Apples is called Cyder; that made from malt is called Beer: yet in Chymistry it is of use to have one general term denoting every liquor that has undergone this first degree of fermentation.
By distillation we draw from Wine an inflammable liquor, of a yellowish white colour, light, and of a penetrating, pleasant smell. This liquor is the truly spirituous part of the wine, and the product of fermentation. That which comes off in the first distillation is commonly loaded with much phlegm and some oily parts, from which it may be afterwards freed. In this state it goes by the name of Brandy; but when freed from these heterogeneous matters by repeated distillations, it becomes still clearer, lighter, more fragrant, and much more inflammable, and then is called Spirit of Wine, and Rectified Spirit of Wine, or an Ardent Spirit, if considerably purified. The properties which distinguish an Ardent Spirit from all other substances are its being inflammable; its burning and consuming entirely, without the least appearance of smoke or fuliginosity; its containing no particles reducible to a coal; and its being perfectly miscible with water. Ardent Spirits are lighter and more volatile than any of the principles of the mixts from which they were produced, and consequently more so than the phlegm, the acid, and the oil of which they themselves consist. This arises from a particular disposition of these principles, which are in a singular manner attenuated by fermentation, and thereby rendered more susceptible of expansion and rarefaction.
Ardent spirits are supposed to be the natural solvents of oils and oily matters. But it is very remarkable that they dissolve essential oils only, without touching the fat of animals, or the fat oils obtained from vegetables by expression; yet when these oils have once undergone the action of fire, they become soluble in spirit of wine, and even acquire a new degree of solubility every time they are distilled. It is not so with essential oils, which can never be rendered more soluble in ardent spirits than they are at first; and are so far from acquiring a new degree of solubility every time they are distilled, that on the contrary they even in some measure lose that property by repeated rectifications.
I have taken some pains to find out the causes of these singular effects, and the result of my inquiries is published among the Memoirs of the Academy of Sciences for the year 1745. I therein consider ardent spirits as consisting of an oil, or at least a phlogiston, mixed with a portion of water, in which it is rendered soluble by means of an acid. This being laid down, I shew that the inability of spirit of wine to dissolve some oils must be imputed to its aqueous part, in which oils are not naturally soluble without the intervention of a salt: and that the power which this spirit exerts in dissolving other oils with ease, such as essential oils, must in all probability be owing to this, that in these oils it meets with the necessary saline medium, that is, with an acid, which numberless experiments shew they actually contain.
On the other hand, I there prove, that the acid in essential oils is superabundant, and in some sort foreign to their nature, or that it is but slightly connected with them, and in part deserts them every time they are distilled; which renders them less soluble after every new rectification: whereas, on the contrary, the fat expressed oils in their natural state give not the least sign of acidity, but the action of fire upon them discovers an acid which was not perceivable before. Hence I conjecture, that these oils contain no more acid than is just necessary to constitute them oils; that this acid is intimately blended with their other component parts; that it is so sheathed and entangled by these parts as to be incapable of exerting any of its properties; and that on this account these oils in their natural state are not soluble in spirit of wine: but that the disposition of their parts being gradually changed by the fire, and their acid, being by that means set more and more at liberty, at length recovers its properties, and particularly that of rendering the oily parts soluble in an aqueous menstruum: and hence it follows, that the fat oils become so much the more soluble in spirit of wine the oftener they are exposed to the action of fire.
Spirit of wine doth not dissolve fixed alkalis; or at least it takes up but a very small quantity thereof; and hence ardent spirits may be freed from much of their phlegm by means of these salts thoroughly dried: for as they strongly imbibe moisture, and have even a greater affinity than ardent spirits with water, if a fixed alkali, well exsiccated, be mixed with spirit of wine that is not perfectly dephlegmated, the alkali immediately attracts its superfluous moisture, and is thereby resolved into a liquor, which, on account of its gravity, descends to the bottom of the vessel. The spirit of wine, which swims at top, is by this means as much dephlegmated, and as dry, as if it had been rectified by several distillations. As it takes up some alkaline particles in this operation, it is thereby qualified to dissolve oily matters with the greater facility. When rectified in this manner, it is called Alcoholized Spirit of Wine.
Yet spirit of wine, even when rectified to an alcohol, is not capable of dissolving all oily matters. Those named Gums will by no means enter into any sort of union therewith; but it readily dissolves most of those which are known by the appellation of Resins. When it has dissolved a certain proportion of resinous particles it acquires a greater consistence, and forms what is called a Spirit Varnish, or a Drying Varnish, because it soon dries. This Varnish is subject to be damaged by water. Many sorts thereof are prepared, differing from each other according to the different resins employed, or the proportions in which they are used. Most of these Varnishes are transparent and colourless.