SECTION III.. _of The_ Acid of Sea-Salt.

Of the ACID OF SEA-SALT.

The Acid of Sea-salt is so called because it is in fact obtained from such Sea-salt as is used in our kitchens. It is not certainly known in what this Acid differs from the vitriolic and the nitrous, with regard to its constituent parts. Several of the ablest Chymists, such as Becher and Stahl, are of opinion that the Marine Acid is no other than the Universal Acid united to a particular principle which they call a Mercurial Earth. Concerning this earth we shall have occasion to say more, when we come to treat of metallic substances: but in the mean time it must be owned, that the truth of this opinion is so far from being proved by a sufficient number of experiments, that the very existence of such a mercurial earth is not yet well established; and therefore, that we may not exceed the bounds of our knowledge, we shall content ourselves with delivering here the properties which characterize the Acid in question, and by which it is distinguished from the two others considered above.

When it is combined with absorbent earths, such as lime and chalk, it forms a neutral salt that does not crystallize, and, when dried, attracts the moisture of the air. If the absorbent earth be not fully saturated with the Marine Acid, the salt thereby formed has the properties of a fixed Alkali: and this is what made us say, when we were on the subject of those salts, that they might be imitated by combining an earth with an Acid. The Marine Acid, like the rest, hath not so great an affinity with earths as with fixed Alkalis.

When it is combined with the latter, it forms a neutral salt which shoots into cubical crystals. This salt is inclined to grow moist in the air, and is consequently one of those which water dissolves in equal quantities, at least as to sense, whether it be boiling hot or quite cold.

The affinity of this Acid with Alkalis and absorbent Earths is not so great as that of the vitriolic and nitrous Acids with the same substances: whence it follows, that, when combined therewith, it may be separated from them by either of those Acids.

The Acid of Sea-salt, thus disengaged from the substance which served it for a basis, is called Spirit of Salt. When it contains but little phlegm it is of a lemon colour, and continually emits many white, very dense, and very elastic vapours; on which account it is named the Smoaking Spirit of Salt. Its smell is not disagreeable, nor much unlike that of saffron; but extremely quick and suffocating when it smokes.

The Acid of Sea-salt, like the other two, seems to have a greater affinity with the Phlogiston, than with fixed Alkalis. We are led to this opinion by a very curious operation, which gives ground to think that Sea-salt may be decomposed by the proper application of a substance containing the Phlogiston.

From the Marine Acid combined with a Phlogiston results a kind of Sulphur, differing from the common sort in many respects; but particularly in this property, that it takes fire of itself upon being exposed to the open air. This combination is called English Phosphorus, Phosphorus of Urine, because it is generally prepared from urine; or, only Phosphorus.

This combination of the Marine Acid with a Phlogiston is not easily effected; because it requires a difficult operation in appropriated vessels. For these reasons it does not always succeed; and Phosphorus is so scarce and dear, that hitherto Chymists have not been able to make on it the experiments necessary to discover all its properties. If Phosphorus be suffered to burn away in the air, a small quantity of an acid liquor may be obtained from it, which seems to be spirit of salt, but either altered, or combined with some adventitious matter; for it has several properties that are not to be found in the pure Marine Acid; such as, leaving a fixed fusible substance behind it when exposed to a strong fire, and being easily combined with the Phlogiston so as to reproduce a Phosphorus.

Phosphorus resembles sulphur in several of its properties: it is soluble in oils; it melts with a gentle heat; it is very combustible; it burns without producing soot; and its flame is vivid and bluish.

From what has been said of the union of the Acid of Sea-salt with a fixed Alkali, and of the neutral salt resulting therefrom, it may be concluded that this neutral salt is no other than the common kitchen-salt. But it must be observed, that the fixed Alkali, which is the natural basis of the common salt obtained from sea-water, is of a sort somewhat differing from fixed Alkalis in general, and hath certain properties peculiar to itself. For,

1. The basis of Sea-salt differs from other fixed Alkalis in this, that it crystallizes like a neutral salt.

2. It does not grow moist in the air; on the contrary, when exposed to the air, it loses part of the water that united with it in crystallization, by which means its crystals lose their transparency, become, as it were, mealy, and fall into a fine flour.

3. When combined with the vitriolic Acid to the point of saturation, it forms a neutral salt differing from vitriolated tartar, first, in the figure of its crystals, which are oblong six-sided solids; secondly, in its quantity of water, which in crystallization unites therewith in a much greater proportion than with vitriolated tartar; whence it follows, that this salt dissolves in water more readily than vitriolated tartar; thirdly, in that it flows with a very moderate degree of heat, whereas vitriolated tartar requires a very fierce one.

If the Acid of Sea-salt be separated from its basis by means of the vitriolic Acid, it is easy to see that, when the operation is finished, the salt we have been speaking of must be the result. A famous Chymist, named Glauber, was the first who extracted the Spirit of Salt in this manner, examined the neutral salt resulting from his process, and, finding it to have some singular properties, called it his Sal mirabile, or wonderful Salt: on this account it is still called Glauber's Sal mirabile, or plainly Glauber's Salt.

4. When the basis of Sea-salt is combined with the nitrous Acid to the point of saturation, there results a neutral salt, or a sort of nitre, differing from the common nitre, first, in that it attracts the moisture of the air pretty strongly; and this makes it difficult to crystallize; secondly, in the figure of its crystals, which are parallelopipeds; and this has procured it the name of Quadrangular Nitre.

Common salt, or the neutral salt formed by combining the Marine Acid with this particular sort of fixed Alkali, has a taste well known to every body. The figure of its crystals is exactly cubical. It grows moist in the air, and, when exposed to the fire, it bursts, before it melts, into many little fragments, with a crackling noise; which is called the Decrepitation of Sea-salt.

That neutral salt mentioned above, which is formed by combining the Marine Acid with a common fixed Alkali, and called Sal febrifugum Sylvii, hath also this property.

India furnishes us with a saline substance, known by the name of Borax, which flows very easily, and then takes the form of glass. It is of great use in facilitating the fusion of metallic substances. It possesses some of the properties of fixed Alkalis, which has induced certain Chymists to represent it, through mistake, as a pure fixed Alkali.

By mixing borax with the vitriolic Acid, Mr. Homberg obtained from it a salt, which sublimes in a certain degree of heat, whenever such a mixture is made. This salt has very singular properties; but its nature is not yet thoroughly understood. It dissolves in water with great difficulty; it is not volatile, though it rises by sublimation from the borax. According to Mr. Rouelle's observation, it rises then only by means of the water which carries it up: for, when once made, it abides the fiercest fire, flows and vitrifies just as borax does: provided care be taken to free it previously from moisture by drying it properly. Mr. Homberg called it Sedative Salt, on account of its medical effects. The sedative salt hath the appearance, and some of the properties, of a neutral salt; for it shoots into crystals, and does not change the colour of violets; but it acts the part of an Acid with regard to Alkalis, uniting with them to the point of saturation, and thereby forming a true neutral salt. It also acts, like the Acid of vitriol on all neutral salts; that is, it discharges the Acid of such as have not the vitriolic Acid in their composition.

Since Mr. Homberg's time it hath been discovered, that a sedative salt may be made either with the nitrous or with the marine Acid; and that sublimation is not necessary to extract it from the borax, but that it may be obtained by crystallization only. For this latter discovery we are indebted to Mr. Geoffry, as we are to Mr. Lemery for the former.

Since that time M. Baron d'Henouville, an able Chymist, hath shewn that a sedative salt may be obtained by the means of vegetable Acids; and hath lately demonstrated, in some excellent papers published in the collection of Memoirs written by the correspondents of the Academy of Sciences, that the sedative salt exists actually and perfectly in the borax, and that it is not produced by mixing Acids with that saline substance, as it seems all the Chymists before him imagined. This he proves convincingly from his analysis of borax, (which thereby appears to be nothing else but the sedative salt united with that fixed Alkali which is the basis of Sea-salt) and from his regenerating the same borax by uniting together that Alkali and the sedative salt: a proof the most complete that can possibly be produced in natural philosophy, and equivalent to demonstration itself.

In order to finish what remains to be said upon the several sorts of saline substances, we should now speak of the Acids obtained from vegetables and animals, and also of the volatile Alkalis: but, seeing these saline substances differ from those of which we have already treated, only as they are variously altered by the unions they have contracted with certain principles of vegetables and animals, of which nothing has been yet said, it is proper to defer being particular concerning them, till we have explained those principles.

CHAP. V.

Of LIME.

Any substance whatever, that has been roasted a considerable time in a strong fire without melting, is commonly called a Calx. Stones and metals are the principal subjects that have the property of being converted into Calces. We shall treat of Metalline Calces in a subsequent chapter, and in this confine ourselves to the Calx of Stone, known by the name of Lime.

In treating of earths in general we observed that they may be divided into two principal kinds; one of which actually and properly flows when exposed to the action of fire, and turns to glass; whence it is called a fusible or vitrifiable earth; the other resists the utmost force of fire, and is therefore said to be an unfusible or unvitrifiable earth. The latter is also not uncommonly called calcinable earth; though sundry sorts of unfusible earths are incapable of acquiring by the action of fire all the qualities of calcined earth, or Lime properly so called: such earths are particularly distinguished by the denomination of refractory earths.

As the different sorts of stones are nothing more than compounds of different earths, they have the same properties with the earths of which they are composed, and may, like them, be divided into fusible or vitrifiable, and unfusible or calcinable. The fusible stones are generally denoted by the name of Flints; the calcinable stones, again, are the several sorts of marbles, cretaceous stones, those commonly called free-stones, &c. some of which, as they make the best Lime, are, by way of eminence, called Lime-stones. Sea-shells, also, and stones that abound with fossile shells, are capable of being burnt to Lime.

All these substances, being exposed, for a longer or shorter time, as the nature of each requires, to the violent action of fire, are said to be calcined. By calcination they lose a considerable part of their weight, acquire a white colour, and become friable though ever so solid before; as, for instance, the very hardest marbles. These substances, when thus calcined, take the name of Quick Lime.

Water penetrates Quick Lime, and rushes into it with vast activity. If a lump of newly calcined Lime be thrown into water, it instantly excites almost as great a noise, ebullition, and smoke, as would be produced by a piece of red-hot iron; with such a degree of heat too, that, if the Lime be in due proportion to the water, it will set fire to combustible bodies; as hath unfortunately happened to vessels laden with Quick Lime, on their springing a small leak.

As soon as Quick Lime is put into water, it swells, and falls asunder into an infinite number of minute particles: in a word, it is in a manner dissolved by the water, which forms therewith a sort of white paste called Slacked Lime.

If the quantity of water be considerable enough for the Lime to form with it a white liquor, this liquor is called Lac Calcis; which, being left some time to settle, grows clear and transparent, the Lime which was suspended therein, and occasioned its opacity, subsiding to the bottom of the vessel. Then there forms on the surface of the liquor a crystalline pellicle, somewhat opaque and dark-coloured, which being skimmed off is reproduced from time to time. This matter is called Cremor Calcis.

Slacked Lime gradually grows dry, and takes the form of a solid body, but full of cracks and destitute of firmness. The event is different when you mix it up, while yet a paste, with a certain quantity of uncalcined stony matter, such as sand, for example: then it takes the name of Mortar, and gradually acquires, as it grows drier and older, a hardness equal to that of the best stones. This is a very singular property of Lime, nor is it easy to account for it: but it is a beneficial one; for every body knows the use of Mortar in building.

Quick Lime attracts the moisture of the air, in the same manner as concentrated acids, and dry fixed alkalis; but not in such quantities as to render it fluid: it only falls into extremely small particles, takes the form of a fine powder, and the title of Lime slacked in the air.

Lime once slacked, however dry it may afterwards appear, always retains a large portion of the water it had imbibed; which cannot be separated from it again but by means of a violent calcination. Being so recalcined it returns to be Quick Lime, recovering all its properties.

Besides this great affinity of Quick Lime with water, which discovers a saline character, it has several other saline properties, to be afterwards examined, much resembling those of fixed alkalis. In Chymistry it acts very nearly as those salts do, and may be considered as holding the middle rank between a pure absorbent earth and a fixed alkali: and this hath induced many Chymists to think that Lime contains a true salt, to which all the properties it possesses in common with salts may be attributed.

But as the chymical examination of this subject hath long been neglected, the existence of a saline substance in Lime hath been long doubtful. Mr. du Fay, author of some excellent chymical experiments, was one of the first who obtained a salt from Lime, by lixiviating it with a great deal of water, which he afterwards evaporated. But the quantity of salt he obtained by that means was very small; nor was it of an alkaline nature, as one would think it should have been, considering the properties of Lime. Mr. du Fay did not carry his experiments on this subject any further, probably for want of time; nor did he determine of what nature the salt was.

Mr. Malouin had the curiosity to examine this salt of Lime, and soon found that it was nothing else but what was above called Cremor Calcis. He found, moreover, that, by mixing a fixed alkali with lime-water, a vitriolated tartar was formed; that, by mixing therewith an alkali like the basis of sea-salt, a Glauber's salt was produced; and, lastly, by combining lime with a substance abounding in phlogiston, he obtained a true sulphur. These very ingenious experiments prove to a demonstration, that the vitriolic acid constitutes the salt of Lime: for, as hath been shewn, no other acid is capable of forming such combinations. On the other hand, Mr. Malouin, having forced the vitriolic acid of this salt to combine with a phlogiston, found its basis to be earthy, and analogous to that of the selenites: whence he concluded, that the salt of Lime is a true neutral salt, of the same kind as the selenites. Mr. Malouin tells us he found several other salts in Lime. But as none of them was a fixed alkali, and as all the saline properties of Lime have an affinity with those of that kind of salt, there is great reason to think that all those salts are foreign to Lime, and that their union with it is merely accidental.

I myself have made several experiments in order to get some insight into the saline nature of Lime, and shall here produce the result with all possible conciseness. I took several stones of different kinds, some of which produced by calcination a very strong Lime, and others but a very weak one. These I impregnated with different saline substances, acids, alkalis, and neutrals, and then exposed them all to the same degree of fire, which was a pretty strong one, and long enough continued to have made very good Lime of stones the most difficult to calcine. The consequence was, that, in the first place, those stones which naturally made but a weak Lime were not, by this process, converted into a stronger Lime; and, moreover, that none of these stones, even such as would naturally have produced the most active Lime, had acquired the properties of Lime. These experiments I varied many ways, employing different proportions of saline matters, and almost every possible degree of fire, and constantly observed, after calcination, that all those stones were so much the farther from the nature of Lime, as they had been combined with larger doses of salts. Among those which were impregnated with the greatest proportion of salts, and had suffered the greatest violence of fire, I observed some that had begun to flow, and were in a manner vitrified. Now, as the same subject cannot be, at one and the same time, in the state of glass and of Lime too; as a body cannot approach to one of these states but in proportion as it recedes from the other; and as salts in general dispose those bodies to fusion and vitrification which are in themselves the most averse to either, I concluded from my experiments, that the saline substances I used, had, by acting as fluxes upon the stones, prevented their calcination; that consequently we may suspect there is no saline matter in the composition of Lime, as Lime; and that Lime does not owe its saline and alkaline properties to any salt; or at least that, if it does owe those properties to a salt, such salt must be naturally and originally combined with the matter of the stone in so just a proportion, that it is impossible to increase the quantity thereof without prejudicing the Lime, and depriving it in some measure of its virtue. This theory agrees perfectly with the illustrious Stahl's opinion; for he thinks, as we observed in discoursing of salts in general, that every saline substance is but an earth combined in a certain manner with water. This notion he applies to Lime, and says, that fire only subtilizes and attenuates the earthy matter, and thereby renders it capable of uniting with water in such a manner, that the result of their combination shall be a substance having saline properties; and that Lime accordingly never acquires these properties till it be combined with water.

I have dwelt longer on the Salt of Lime than I shall on any other particular; because the subject, though in itself of great importance, has hitherto been but little attended to, and because the experiments here recited are entirely new.

Lime unites with all acids, and in conjunction with them exhibits various phenomena.

The vitriolic acid poured upon Lime dissolves it with effervescence and heat. From this mixture there exhales a great quantity of vapours, in smell and colour perfectly like those of sea-salt; from which, however, they are found to be very different when collected into a liquor. From this combination of the vitriolic acid with Lime arises a neutral salt, which shoots into crystals, and is of the same kind with the selenetic salt obtained from Lime by Mr. Malouin.

The nitrous acid poured upon Lime dissolves it in like manner with effervescence and heat: but the solution is transparent, and therein differs from the former, which is opaque. From this mixture there arises a neutral salt, which does not crystallize, and has withal the very singular property of being volatile, and rising wholly by distillation in a liquid form. This phenomenon is so much the more remarkable, as Lime, the basis of this salt, is one of the most fixed bodies known in Chymistry.

With the acid of sea-salt Lime forms also a singular sort of salt, which greedily imbibes the moisture of the air. We shall have occasion to take further notice of it in another place.

These experiments made on Lime with acids are likewise quite new. We are indebted for them to Mr. Du Hamel of the Academy of Sciences, whose admirable Memoirs on several subjects shew his extensive knowledge in all parts of Natural Philosophy.

Lime applied to fixed alkalis adds considerably to their caustic quality, and makes them more penetrating and active. An alkaline lixivium in which Lime hath been boiled, being evaporated to dryness, forms a very caustic substance, which flows in the fire much more easily, attracts and retains moisture much more strongly, than fixed alkalis that have not been so treated. An alkali thus acuated by Lime is called the Caustic Stone, or Potential Cautery; because it is employed by surgeons to produce eschars on the skin and cauterize it.

CHAP. VI.

Of Metallic Substances in general.

Metallic Substances are heavy, glittering, opaque, fusible bodies. They consist chiefly of a vitrifiable earth united with the phlogiston.

Several Chymists insist on a third principle in these bodies, and have given it the name of Mercurial Earth; which, according to Becher and Stahl, is the very same that being combined with the vitriolic acid forms and characterizes the acid of sea-salt. The existence of this principle hath not yet been demonstrated by any decisive experiment; but we shall shew that there are pretty strong reasons for admitting it.

We shall begin with mentioning the experiments which prove Metallic Substances to consist of a vitrifiable earth united with the phlogiston. The first is this: if they be calcined in such a manner as to have no communication with any inflammable matter, they will be spoiled of all their properties, and reduced to an earth or calx, that has neither the splendour nor the ductility of a metal, and in a strong fire turns to an actual glass, instead of flowing like a metal.

The second is, that the calx or the glass resulting from a metal thus decomposed, recovers all its metalline properties by being fused in immediate contact with an inflammable substance, capable of restoring the phlogiston of which calcination had deprived it.

On this occasion we must observe, that Chymists have not yet been able, by adding the phlogiston, to give the properties of metals to all sorts of vitrifiable earths indiscriminately; but to such only as originally made a part of some metallic body. For example, a compound cannot be made with the phlogiston and sand that shall have the least resemblance of a metal: and this is what seems to point out the reality of a third principle, as necessary to form the metalline combination. This principle may probably remain united with the vitrifiable earth of a metallic substance, when reduced to a glass; whence it follows, that such vitrified metals require only the addition of a phlogiston to enable them to appear again in their pristine form.

It may be inferred from another experiment, that the calx and the glass of a metal are not its pure vitrifiable earth, properly so called: for by repeated or long-continued calcinations, such a calx or glass may be rendered incapable of ever resuming the metalline form, in whatever manner the phlogiston be afterwards applied to it; so that by this means it is brought into the condition of a pure vitrifiable earth, absolutely free from any mixture. Those Chymists who patronize the Mercurial earth, produce many other proofs of the existence of that principle in Metallic Substances; but they would be misplaced in an elementary treatise like this.

When by adding the phlogiston to a metallic glass we restore it to the form of a metal, we are said to reduce, resuscitate, or revivify that metal.

Metallic Substances are of different kinds, and are divided into Metals and Semi-metals.

Those are called Metals which, besides their metalline splendour and appearance, are also malleable; that is, have the property of stretching under the hammer, and by that means of being wrought into different forms without breaking.

Those which have only the metalline splendour and appearance, without malleability, are called Semi-metals.

Metals are also further subdivided into two sorts; viz. Perfect and Imperfect Metals.

The Perfect Metals are those which suffer no damage or change whatever by the most violent and most lasting action of fire.

The Imperfect Metals are those which by the force of fire, may be deprived of their phlogiston, and consequently of their metalline form.

When but a moderate degree of fire is employed to deprive a Metal of its phlogiston, the metal is said to be calcined; and then it appears in the form of a powdered earth, which is called a Calx: and this metalline calx being exposed to a more violent degree of fire melts and turns to glass.

Metallic Substances have an affinity with acids: but not equally with all; that is, every Metallic Substance is not capable of uniting and joining with every acid.

When an acid unites with a Metallic Substance there commonly arises an ebullition, attended with a kind of hissing noise and fuming exhalations. By degrees, as the union becomes more perfect, the particles of the metal combining with the acid become invisible: this is termed Dissolution; and when a metalline mass thus appears in an acid, the metal is said to be dissolved by that acid. It is proper to observe, that acids act upon Metalline Substances, in one respect, just as they do upon alkalis and absorbent earths: for an acid cannot take up above such a certain proportion thereof as is sufficient to saturate it, to destroy several of its properties, and weaken others. For example, when an acid is combined with a metal to the point of saturation, it loses its taste, does not turn the blue colour of a vegetable red, and its affinity with water is considerably impaired. On the other hand, Metalline Substances, which when pure are incapable of uniting with water, by being joined with an acid acquire the property of dissolving in water. These combinations of Metalline Substances with acids form different sorts of neutral salts; some of which have the property of shooting into crystals, while others have it not: most of them, when thoroughly dried, attract the moisture of the air.

The affinity which Metalline Substances have with acids is less than that which absorbent earths and fixed alkalis have with the same acids; so that all metalline salts may be decompounded by one of these substances, which will unite with the acid, and precipitate the metal.

Metalline Substances thus separated from an acid solvent are called Magisteries and Precipitates of metals. None of these precipitates, except those of the perfect metals, retain the metalline form: most of their phlogiston hath been destroyed by the solution and precipitation, and must be restored before they can recover their properties. In short, they are nearly in the same state with Metalline Substances deprived of their phlogiston by calcination; and accordingly such a precipitate is called a Calx.

A metalline calx prepared in this manner loses a greater or a less portion of its phlogiston, the more or less effectually and thoroughly the Metalline Substance, of which it made a part, was dissolved by the acid.

Metallic Substances have affinities with each other which differ according to their different kinds: but this is not universal; for some of them are incapable of any sort of union with some others.

It must be observed, that Metallic Substances will not unite, except they be both in a similar state; that is, both in a Metalline form, or both in the form of a Glass; for a Metalline Substance retaining its phlogiston cannot contract an union with any metallic glass, even its own.

CHAP. VII.

Of METALS.

There are six Metals, of which two are Perfect and four Imperfect. The perfect Metals are Gold and Silver; the others are Copper, Tin, Lead, and Iron. Some Chymists admit a seventh Metal, to wit, Quick-silver: but as it is not malleable, it has been generally considered as a metallic body of a particular kind. We shall soon have occasion to examine it more minutely.

The ancient Chymists, or rather the Alchymists, who fancied a certain relation or analogy between Metals and the Heavenly Bodies, bestowed on the seven Metals, reckoning Quick-silver one of them, the names of the seven Planets of the Ancients, according to the affinity which they imagined they observed between those several bodies. Thus Gold was called Sol, Silver Luna, Copper Venus, Tin Jupiter, Lead Saturn, Iron Mars, and Quick-silver Mercury. Though these names were assigned for reasons merely chimerical, yet they still keep their ground; so that it is not uncommon to find the Metals called by the names, and denoted by the characters, of the Planets, in the writings even of the best Chymists. Metals are the heaviest bodies known in nature.