Chapter XLII: Section I: Operations performed on Saline Mineral Substances (3)

We shall, in the second place, observe with M. Hellot, that, "before you set your retort in the furnace, it is proper to make an essay of your matter, to see if there be reason to hope for success. For this purpose put about an ounce thereof into a small crucible, and heat it till the vessel be red. The mixture, after having smoked, ought to chop or crack without puffing up, or even rising in the least. From these cracks will issue undulating flames, white and blueish, darting upwards with rapidity. This is the first volatile Phosphorus, which occasions all the danger of the operation. When these first flashes are over, increase the heat of your matter by laying a large live coal upon the crucible. You will then see the second Phosphorus, like a luminous, steady vapour, of a colour inclining to violet, covering the whole surface of the matter: it continues for a very long time, and diffuses a smell of garlic, which is the distinguishing odour of the Phosphorus you are seeking.

"When this luminous vapour is entirely gone, pour the red hot matter out of the crucible upon an iron plate. If you do not find one drop of salt in fusion, but that, on the contrary, the whole falls readily into powder, it is a proof that your matter was sufficiently lixiviated, and that it contains no more fixed Salt, or Sea-salt, if you will, than is requisite. If you find on the plate a drop of salt coagulated, it shews that there is too much left in, and that there is danger of your miscarrying in the operation; because the redundant salt would corrode, and eat through the retort. In this case your matter must be washed again, and then sufficiently dried."

Our third observation shall be concerning the furnace proper to be employed in this operation. This furnace must be so constructed, that, within a narrow compass it may give a heat at least equal to that of a glass-house furnace, or rather greater, especially during the last seven or eight hours of the operation. M. Hellot in his Memoir gives an exact description of such a furnace.

"As certain accidents may happen in the course of the operation, some precautions are to be taken against them. For instance, if the ballon should break while the Phosphorus is distilling, and any of it should fall on combustible bodies, it would set them on fire, and probably burn the laboratory, because it is not to be extinguished without the greatest difficulty. The furnace must therefore be erected under some vault, or upon a bed of brick-work raised under some chimney that draws well: nor must any furniture or utensil of wood be left near it. If a little flaming Phosphorus should fall on a man's legs or hands, in less than three minutes it would burn its way to the very bone. In such a case nothing but urine will stop its progress.

"If the retort crack while the Phosphorus is distilling, there is an unsuccessful end of your operation. It is easy to perceive this by the stink of garlic which you will smell about the furnace; and moreover, the flame that issues through the apertures of the reverberatory will be of a beautiful violet colour. The Acid of Sea-salt always gives this colour to the flame of such matters as are burnt along with it. But if the retort break before the Phosphorus hath made its appearance, its contents may be saved by throwing a number of cold bricks into the fire-place, and upon them a little water to quench the fire at once." All these useful observations we owe also to M. Hellot.

The Phosphorus here described was first discovered by a citizen of Hamburgh, named Brandt, who worked upon urine in search of the Philosopher's stone. Afterwards two other skilful Chymists, who knew nothing more of the process, than that Phosphorus was obtained from urine, or, in general, from the human body, likewise endeavoured to discover it; and each of them separately did actually make the discovery. These two Chymists were Kunckel and Boyle.

The former perfected the discovery, and found out a method of making it in considerable quantities at a time; which occasioned it to be called _Kunckel's Phosphorus_. The other, who was an English gentleman, had not time to bring his discovery to perfection, and contented himself with lodging a voucher of his having discovered it in the hands of the Secretary of the Royal Society of London, who gave him a certificate thereof.

"Though Brandt," says M. Hellot, "who had before this sold his secret to a Chymist named Krafft, sold it afterwards to several other persons, and even at a very low rate; and though Mr. Boyle published the process for making it; yet it is extremely probable that both of them kept in their own hands the master-key; I mean, _the particular management necessary to make the operation succeed_: for, till Kunckel found it out, no other Chymist ever made any considerable quantity thereof, except Mr. Godfrey Hankwitz, an English Chymist, to whom Mr. Boyle revealed the whole mystery.

"Nevertheless," continues he, "we are very far from alledging that all those who have described this operation meaned to impose upon the world: but we conceive that most of them having observed luminous vapours in the ballon, and some sparks about the juncture of the vessels, were contented with those appearances. And thus it came to pass, that, after Kunckel and Boyle died, Mr. Godfrey Hankwitz was the only Chymist that could supply Europe therewith; on which account it is likewise very well known by the name of _English Phosphorus_."

Almost all the Chymists consider Phosphorus as a substance consisting of the Acid of Sea-salt combined with the Phlogiston, in the same manner as Sulphur consists of the Vitriolic Acid combined with the Phlogiston. This opinion is founded on the following principles.

First, Urine abounds with Sea-salt, and contains also a great deal of Phlogiston; now these are the ingredients of which they conjecture Phosphorus to be composed.

Secondly, Phosphorus has many of the properties of Sulphur; such as being soluble in oils; melting with a gentle heat; being very combustible; burning without any soot; giving a vivid and blueish flame; and lastly, leaving an acid liquor when burnt: sensible proofs that it differs from Sulphur in nothing but the nature of its Acid.

Thirdly, this Acid of Phosphorus, being mixed with a solution of silver in Spirit of Nitre, precipitates the silver, and this precipitate is a true _Luna cornea_, which appears to be more volatile even than the common sort; as M. Hellot tells us, who made the experiment. This fact proves incontestably that the Acid of Phosphorus is of the same nature with that of Sea-salt: for all Chymists know that the property of precipitating silver in a _Luna cornea_ belongs to the Marine Acid only.

Fourthly, M. Stahl observes, that, if Sea-salt be cast on live coals, they instantly burn with great activity; then they emit a very vivid flame, and are much sooner consumed than if none of this salt had touched them; that Sea-salt in substance, which will bear the violence of fire a considerable time when fused in a crucible, without sustaining any sensible diminution, yet evaporates very quickly, and is reduced to white flowers, by the immediate contact of burning coals; and, lastly, that the flame which rises on this occasion is of a blue colour inclining to violet, especially if it be not thrown directly on the coals themselves, but kept in fusion amidst burning coals, in a crucible so placed that the vapour of the Salt may join with the enflamed Phlogiston as it rises from the coals.

These experiments of M. Stahl's prove, that the Phlogiston acts upon the acid of Sea-salt, even while it is combined with its alkaline basis. The flame that appears on this occasion may be considered as an imperfect Phosphorus: and indeed its colour is exactly like that of Phosphorus.

All the facts above related evince, that the Acid of Phosphorus is akin to that of Sea-salt; or rather that it is the very same. But there are other facts which prove that this Acid undergoes some change at least, some peculiar preparation, before it enters into the composition of a true Phosphorus, and that, when extricated therefrom by burning, it is not a pure Acid of Sea-salt, but is still adulterated with a mixture of some other substance, which makes it considerably different from that Acid. For these observations we are obliged to M. Marggraff, of the Academy of Sciences at Berlin, a celebrated Chymist. I shall presently give an account of his principal experiments as succinctly as possible.

M. Marggraff hath also published a process for making Phosphorus, and assures us, that by means thereof we may obtain in less time, with less heat, less trouble, and less expence, a greater quantity of Phosphorus than by any other method. His operation is this:

He takes two pounds of Sal Ammoniac in powder, which he mixes accurately with four pounds of Minium. This mixture he puts into a glass retort, and with a graduated fire draws off a very sharp, volatile, urinous spirit.

We observed in our theoretical Elements, that some metallic substances have the property of decomposing Sal Ammoniac, and separating its volatile Alkali; concerning which phenomenon we there gave our opinion. Minium, which is a calx of lead, is one of those metallic substances. In this experiment it decomposes the Sal Ammoniac, and separates its volatile Alkali; what remains in the retort is a combination of the Minium with the Acid of the Sal Ammoniac, which is well known to be the same with the Marine Acid; and consequently the residue of this operation is a sort of _Plumbum corneum_.

The quantity thereof is four pounds eight ounces. Of this he mixes three pounds with nine or ten pounds of urine, that has stood putrefying for two months, evaporated to the consistence of honey. These he mixes by little and little in an iron pan over the fire, stirring the mixture from time to time. Then he adds half a pound of charcoal-dust, and evaporates the matter, kept continually stirring, till the whole be brought to a black powder. He next distils the mixture in a glass retort with degrees of fire, which he raises towards the end so as to make the retort red-hot, in order to expel all the urinous spirit, superfluous oil, and ammoniacal salt. The distillation being finished, there remains nothing in the retort but a very friable _caput mortuum_.

This remainder he pulverises again, and throws a pinch thereof on live coals, thereby to discover whether or no the matter be rightly prepared, and in order for yielding Phosphorus. If it be so, it presently emits an arsenical odour, and a blue undulating flame, which passes over the surface of the coals like a wave.

Being thus assured of the success of his operation, he puts one half of his matter in three equal parts, into three small earthen German retorts, capable of holding about eighteen ounces of water a-piece. These three retorts, none of which is above three quarters full, he places together in one reverberatory furnace, built much like those we have described, except that it is so constructed as to hold the three retorts disposed in one line. To each retort he lutes a recipient something more than half full of water, ordering the whole in such a manner, that the noses of his retorts almost touch the surface of the water.

He begins the distillation with warming the retorts slowly, for about an hour, by a gentle heat. When that time is elapsed he raises the fire gradually, so that in half an hour more the coals begin to touch the bottoms of the retorts. He continues throwing coals into the furnace by little and little, till they rise half way the heighth of the retorts; and in this he employs another half hour. Lastly, in the next half hour he raises the coals above the bowls of the retorts.

Then the Phosphorus begins to ascend in clouds: on this he instantly increases the heat of the fire as much as possible, filling the furnace quite up with coals, and making the retorts very red. This degree of fire causes the Phosphorus to distil in drops, which fall to the bottom of the water. He keeps up this intense heat for an hour and half, at the end of which the operation is finished; so that it lasts but four hours and an half in all: nay, he further assures us, that an artist well versed in managing the fire, may perform it in four hours only. In the same manner he distils the second moiety of his mixture in three other such retorts.

The advantage he finds in making use of several small retorts, instead of a single large one, is, that the heat penetrates them with more ease, and the operation is performed with less fire, and in less time. He purifies and moulds his Phosphorus much in the same manner as M. Hellot does. From the quantity of ingredients above-mentioned, he obtains two ounces and a half of fine crystalline moulded Phosphorus.

M. Marggraff considering, as a consequence of the experiments above related, that a highly concentrated Acid of Sea-salt contributes greatly towards the formation of Phosphorus, proceeded to try several other experiments, in which he employed that Acid in a state of combination with other bases. He mixed, for instance, an ounce of _Luna cornea_ with an ounce and half of putrefied and inspissated urine, and from the mixture obtained a very beautiful Phosphorus.

In short, the several experiments mentioned having thoroughly persuaded him that the Acid of Sea-salt, provided it were highly concentrated, would combine with the Phlogiston as readily as the Vitriolic Acid does, he resolved to try whether he could not make Phosphorus with matters containing that Acid and the Phlogiston, without making use of any urine.

With this view he made a great number of different trials, wherein he employed Sea-salt in substance, Sal Ammoniac, Plumbum corneum, Luna cornea, fixed Sal Ammoniac, otherwise called _Oil of Lime_. These several substances, all of which contain the Acid of Sea-salt, he mixed with sundry matters abounding in Phlogiston, different vegetable coals, and even animal matters, such as the oil of hartshorn, human blood, _&c._ varying the proportions of these substances many different ways, without ever being able to produce a single atom of Phosphorus: which gave this able Chymist just cause to suspect, that the Marine Acid, while pure and crude, is not capable of combining with the Phlogiston in the manner requisite to form a Phosphorus; that for this purpose it is necessary the Acid would have contracted a previous union with some other matter; and that the Acid found in urine hath probably undergone the necessary change. M. Marggraff is of opinion that the matter, which by its union renders the Marine Acid capable of entering into the composition of Phosphorus, is a sort of exceedingly subtle vitrifiable earth. The experiments he made upon the Acid of Phosphorus, will shew that his notion is not altogether groundless. M. Marggraff having let some urine, evaporated to the consistence of honey, stand quiet in a cool place, obtained from it, by crystallization, a Salt of a singular nature. By distilling this urine afterwards, he satisfied himself that it yielded him much less Phosphorus than urine from which no Salt had been extracted; and as it cannot be entirely deprived of this Salt, he thinks that the small quantity of Phosphorus, which this urine yielded him, came from the Salt that was still left in it.

Further, he distilled this salt separately with lamp-black, and obtained from it a considerable quantity of very fine Phosphorus. He even mixed _Luna cornea_ with this Salt, in order to see whether it would not increase the quantity of his Phosphorus; but without success: whence he concluded, that in this Saline matter resides the true Acid that is fit to enter into the composition of Phosphorus. This opinion is confirmed by several experiments on the Acid of Phosphorus, which he found to have some properties resembling those of this Salt.

The Acid of Phosphorus seems to be more fixed than any other: and therefore if you would separate it, by burning, from the Phlogiston with which it is united, there is no occasion for such an apparatus of vessels as is employed for obtaining the Spirit of Sulphur. For this Acid will remain at the bottom of the vessel in which you burn your Phosphorus: indeed, if it be urged by the force of fire, its most subtile part evaporates, and the remainder appears in the form of a vitrified matter.

This Acid effervesces with fixed and volatile Alkalis, and therewith forms Neutral Salts; but very different from Sea-salt, and from Sal Ammoniac. That which has a fixed Alkali for its basis does not crackle when thrown on burning coals; but swells and vitrifies like Borax. That which has a volatile Alkali for its basis shoots into long pointed crystals; and, being urged by fire in a retort, lets go its volatile alkali, a vitrified matter remaining behind. This Salt is like that above-mentioned, as obtained from urine and yielding Phosphorus.

It appears from the experiments adduced, that the Acid of Phosphorus tends always to vitrification; which proves that it is not pure, and gave M. Marggraff cause to think that it is altered by the admixture of a very subtile vitrifiable earth.

M. Marggraff also obtained Phosphorus from several vegetable substances which we use every day for food. This gives him occasion to conjecture, that the Salt requisite to the formation of Phosphorus exists in vegetables, and passes from thence into the animals that feed upon them.

Lastly, he concludes his dissertation by informing us of a very important truth, _viz._ That the Acid obtained from Phosphorus, by burning it, will serve to form Phosphorus anew; for which purpose it need only be combined with some charred coal, such as lamp-black, and distilled.

From what hath been said on this subject it is plain, that the Chymists have a great many curious and interesting inquiries to make concerning Phosphorus, and particularly concerning its Acid.

I shall conclude this article with an account of certain properties of Phosphorus which I have not yet mentioned.

Phosphorus dissolves by lying exposed to the air. What water cannot effect, says M. Hellot, or at least requires eight or ten years to bring about, the moisture of the air accomplishes in ten or twelve days; whether it be that the Phosphorus takes fire in the air, and the inflammable part evaporating, almost entirely, leaves the Acid of the Phosphorus naked, which, like all other Acids, when exceedingly concentrated, is very greedy of moisture; or else that the moisture of the air, being water divided into infinitely fine particles, is so subtile as to find its way through the pores of the Phosphorus, into which the grosser particles of common water can by no means insinuate themselves.

Phosphorus heated by the vicinity of fire, or by being any way rubbed, soon takes fire and burns fiercely. It is soluble in all Oils and in Ether, giving to those liquors the property of appearing luminous when the bottle containing the solution is opened. Being boiled in water, it likewise communicates thereto this luminous quality. M. Morin, Professor at Chartres, is the author of this observation.

The late Mr. Grosse, a celebrated Chymist of the Academy of Sciences, observed, that Phosphorus being dissolved in essential oils crystallizes therein. These crystals take fire in the air, either when thrown into a dry vessel, or wrapt up in a piece of paper. If they be dipped in Spirit of Wine, and taken out immediately, they do not afterwards take fire in the air: they smoke a little, and for a very short time, but hardly waste at all. Though some of them were left in a spoon for a fortnight, they did not seem to have lost any thing of their bulk: but when the spoon was warmed a little they took fire, just like common Phosphorus that had never been dissolved and crystallized in an essential Oil.

M. Marggraff, having put a dram of Phosphorus, with an ounce of highly concentrated Spirit of Nitre, into a glass retort, observed, that, without the help of fire, the Acid dissolved the Phosphorus; that part of the Acid came over into the recipient which was luted to the retort; that, at the same time, the Phosphorus took fire, burnt furiously, and burst the vessels with explosion. Nothing of this kind happens when any of the other Acids, though concentrated, are applied to Phosphorus.

PROCESS III.

_To decompose Sea-salt by means of the Vitriolic Acid. Glauber's Salt. The Purification and Concentration of Spirit of Salt._

Put the Sea-salt from which you mean to extract the Acid into an unglazed earthen pipkin, and set it amidst live coals. The Salt will decrepitate, grow dry, and fall into a powder. Put this decrepitated Salt into a tubulated glass retort, leaving two thirds thereof empty. Set the retort in a reverberating furnace; apply a receiver like that used in distilling the Smoking Spirit of Nitre, and lute it on in the same manner, or rather more exactly if possible. Then through the hole, in the upper convexity of the retort, pour a quantity of highly concentrated Oil of Vitriol, equal in weight to about a third part of your Salt, and immediately shut the hole very close with a glass stopple, first ground therein with emery so as to fit it exactly.

As soon as the Oil of Vitriol touches the Salt, the retort and receiver will be filled with abundance of white vapours; and soon after, without lighting any fire in the furnace, drops of a yellow liquor will distil from the nose of the retort. Let the distillation proceed in this manner without fire, as long as you perceive any drops come: afterwards kindle a very small fire under the retort, and continue distilling and raising the fire by very slow degrees, and with great caution, to the end of the distillation; which will be finished before you have occasion to make the retort red-hot. Unlute the vessels, and without delay pour the liquor, which is a very smoking Spirit of Salt, out of the receiver into a crystal bottle, like that directed for the smoking Spirit of Nitre.

_OBSERVATIONS._

Sea-Salt, as hath been already said, is a Neutral Salt composed of an Acid, which differs from those of Vitriol and Nitre, combined with a fixed Alkali that has some peculiar properties; but does not vary from the others in its affinities. This Salt therefore, as well as Nitre, must be decomposed by the Vitriolic Acid; which accordingly is the case in the process here described. The Vitriolic Acid unites with the Alkaline basis of the Sea-salt, and separates its Acid; and that with much greater facility than it expels the Nitrous Acid from its Alkaline basis, because the Acid of Sea-salt has not so great an affinity as the Nitrous Acid with Fixed Alkalis.

As a highly concentrated Oil of Vitriol is used on this occasion, and as the Sea-salt is previously dried and decrepitated, the Acid obtained from it by distillation is very free from phlegm, and always smokes, even more violently than the strongest Acid of Nitre. The vapours of this Acid are also much more elastic and more penetrating than those of the Nitrous Acid: on which account this distillation of the smoking Spirit of Salt is one of the most difficult, most laborious, and most dangerous operations in Chymistry.

This process requires a tubulated retort, that the Oil of Vitriol may be mixed with the Sea-salt after the receiver is well luted to the retort, and not before: for, as soon as these two matters come together, the Spirit of Salt rushes out with so much impetuosity, that, if the vessels were not luted at the time, the copious vapours that would issue through the neck of the ballon would so moisten it, as well as the neck of the retort, that it would be impracticable to apply the lute and secure the joint as the operation requires. Moreover, the operator would be exposed to those dangerous fumes, which, on this occasion, rush out, and enter the lungs, with such incredible activity as to threaten instant suffocation.

Having said so much of the elasticity and activity of the fumes of Spirit of Salt, it is needless to insist upon the necessity of giving vent to the vessels from time to time, by opening the little hole of the ballon: indeed the best way to prevent the loss of a great many vapours, on this occasion, is to employ adopters, and cover them with wet canvas, which will cool and condense the vapours they contain.

When the operation is finished, we find a white, saline mass at the bottom of the retort as in a mould. If this mass be dissolved in water, and the solution crystallized, it yields a considerable quantity of Sea-salt that hath not been decomposed, and a Neutral Salt consisting of the Vitriolic Acid united with the Alkaline basis of that part which hath been decomposed. This Neutral Salt, which bears the name of _Glauber_ its inventor, differs from Vitriolated Tartar, or the _Sal de duobus_, which remains after distilling the Nitrous Acid, especially in that it is more fusible, more soluble in water, and hath its crystals differently figured. But as in these two Salts the Acid is the same, the differences that appear between them must be attributed to the peculiar nature of the basis of Sea-salt.

Spirit of Salt drawn by the process above described is tainted with a small mixture of the Vitriolic Acid, carried up by the force of fire before it had time to combine with the Alkali of the Sea-salt; which happens likewise to the Nitrous Acid procured in the same manner. If you desire to have it pure, and absolutely free from the Acid of Vitriol, it must be distilled a second time from Sea-salt, as the Acid of Nitre was before directed to be distilled again from fresh Nitre, in order to purify it from any Vitriolic taint.

Sea-salt, as well as Nitre, may be decomposed by any combination of the Vitriolic Acid with a metallic or earthy substance: but it is proper to observe, that if you distil Spirit of Salt by means of Green Vitriol, the operation will not succeed so well as when Spirit of Nitre is distilled in the same manner: less Spirit is obtained, and a much fiercer fire is required.

The cause of this lies in the property which the Acid of Sea-salt possesses of dissolving Iron, even when deprived of a part of its Phlogiston by having contracted an union with another Acid; so that it is no sooner dislodged from its own basis by the Vitriolic Acid, than it unites with the ferruginous basis of the Vitriol, from which it cannot be separated but by a most violent fire. This is the consequence more especially when calcined Vitriol is made use of: for moisture, as we shall presently see, greatly facilitates the separation of the Marine Acid from those substances with which it is united.

When you do not desire a highly dephlegmated and smoking Spirit of Salt, you may distil with the additament of any earth containing the Vitriolic Acid; as Clay, for instance, or Bole. To this end one part of Sea-salt, slightly dried and reduced to a fine powder, must be accurately mingled with two parts of the earth you intend to employ likewise pulverized; of this mixture make a stiff paste with a proper quantity of rain water, and having formed little balls thereof about the size of a hazel nut, let them dry in the sun; when dry, put them into a stone or coated glass retort, leaving a third part thereof empty; set this vessel in a reverberating furnace, covered with its dome; apply a receiver, which need not be luted on for some time; and heat the vessels very slowly. At first an insipid water will rise, which must be thrown away: afterwards the Spirit of Salt will appear in white clouds. Now lute your vessels, and raise the fire by degrees; which, towards the end must be pushed to the utmost extremity. The operation is known to be finished when no drops fall from the nose of the retort, the receiver cools, and the white vapours that filled it are seen no more.

The Spirit of Salt obtained by the process here delivered does not smoke, and contains much more phlegm than that which is distilled by means of the concentrated Oil of Vitriol; because the earth, though dried in the sun, still retains a great deal of moisture, which commixes with the Acid of the Sea-salt. Consequently it is much easier to collect its vapours; so that this operation is attended with much less trouble than the other. Nevertheless it is adviseable to proceed gently; to apply but little heat at first, and to unstop every now and then the small hole of the receiver: for a quantity of the vapours of Spirit of Salt, even when weakened by the admixture of water, is very apt to burst the vessels.

A much greater degree of fire is necessary to raise the Spirit of Salt by this latter process, than by that in which the pure Vitriolic Acid is employed: for, as fast as the Spirit of Salt is dislodged from its own basis, by the Vitriolic Acid contained in the earth made use of, part of it joins that earth, and cannot be separated from it without the most violent heat.

A Spirit of Salt that shall not smoke may also be obtained by means of the pure Vitriolic Acid. Spirit of Vitriol, or Oil of Vitriol, lowered with a good deal of water, will do the business.

Some Chymists direct a little water to be placed in the receiver, when Spirit of Salt is to be distilled by the intermedium of concentrated Oil of Vitriol, in order to make the acid vapours condense more readily. By this means indeed some of the inconveniencies attending the distillation of smoking Spirit of Salt may be avoided: but, on the other hand, the acid vapours being absolutely suffocated by the water as fast as they come over, the Spirit of Salt obtained by this method will be no less aqueous than that procured by the interposition of earths: so that here is an expence to no manner of purpose. Therefore, when a Spirit of Salt is desired that shall not smoke, it is best to employ an additament of earth; and that so much the rather as the Marine Acid obtained by this means is purer and freer from any Vitriolic taint, for the reasons already assigned.

Part of the Acid of Sea-salt may be separated from its Alkaline basis by the force of fire alone, without the intervention of any other body. With this view the Salt must be put into the retort without being dried. At first an insipid water rises; but it gradually becomes acid, and hath all the properties of Spirit of Salt. When the Salt in the retort is grown perfectly dry, nothing more can be forced over by any degree of heat whatever. If you would obtain more Acid from the same Salt, you must take it out of the retort, where you will find it in a lump, reduce it to powder, and expose it to the air for some time, that it may attract the moisture thereof; or else wet it at once with some rain water, and distil as before. You will again have an insipid water, and a little Spirit of Salt; which will in like manner cease to rise when the Salt in the retort becomes dry. This operation may be repeated as often as shall be thought proper: and perhaps it may be possible to decompose Sea-salt entirely by means thereof, without the interposition of any other body. The Spirit of Salt thus obtained is exceeding weak, in small quantity, and loaded with much water.

This experiment proves, that moisture greatly facilitates the separation of the Acid of Sea-salt from the matters with which it is united: and this is the reason that, in distilling Spirit of Salt with the additament of an earth, the operation requires much less fire at the beginning, while the earth and salt retain a great deal of humidity, than towards the end, when they begin to grow dry.

After the operation there remains in the retort a saline and earthy mass, which contains, 1. Some entire Sea-salt that has suffered no decomposition; 2. A Glauber's Salt which is, as we said before, a Neutral Salt consisting of the Vitriolic Acid united with the Alkaline basis of the Sea-salt, from which it hath expelled its proper Acid; 3. Part of the earth used as an intermedium, still retaining a portion of its original Vitriolic Acid, which happening not to lie near enough to any particles of Sea-salt, could not exert its power in decomposing them, and so remains united with its earthy basis; 4. Another part of the same earth, impregnated with some of the Marine Acid, which combined therewith upon being expelled from its Alkaline basis by the Vitriolic Acid, and which the force of fire was unable to separate from it when the matters were grown perfectly dry. In consequence of what remains in this _caput mortuum_, if the whole mass be triturated, moistened with a little water, and distilled a second time, considerably more Spirit of Salt will be obtained from it: and the same is to be said of all distillations of this sort.

Spirit of Salt obtained by the means of any other additament than concentrated Oil of Vitriol is generally very weak: but it may be dephlegmated and concentrated, if required, much in the same manner as Oil of Vitriol. For this purpose you must put it into a glass cucurbit, set it in a _balneum mariæ_, fit thereto a head and a receiver, and with a moderate degree of heat draw off one third or one half of the liquor. What comes over into the receiver will be the most aqueous part, which being the lightest will rise first, impregnated however with a little acid: in the cucurbit will be left a concentrated Spirit of Salt, or the most acid part, which being the heaviest will not rise with the degree of heat that is capable of carrying up the phlegm. Spirit of Salt thus concentrated, called also _Oil of Salt_, does not smoke: it is of a yellow colour inclining to green, and an agreeable smell, not unlike that of saffron.

PROCESS IV.

_To decompose Sea-salt by means of the Nitrous Acid._ Aqua regis. _Quadrangular Nitre._

Take dried Sea-salt; bruise it to powder; put it into a glass retort, leaving one half of the vessel empty. Pour upon it a third of its weight of good Spirit of Nitre. Place your retort in the sand-bath of a reverberating furnace; put on the dome; lute to the retort a receiver having a small hole in it, and heat the vessels very slowly. There will come over into the receiver some vapours, and an acid liquor. Increase the fire gradually till nothing more rises. Then unlute the vessels, and pour the liquor out of the receiver into a crystal bottle, stopped like others containing Acid Spirits.

_OBSERVATIONS._

The Nitrous Acid hath a greater affinity than the Marine Acid with fixed Alkalis. When therefore Spirit of Nitre and Sea-salt are mixed together, the same consequences, in some measure, will follow, as when the Vitriolic Acid is mixed with that salt; that is, the Nitrous Acid will, like the Vitriolic, decompose it, by dislodging its Acid from its Alkaline basis, and assuming its place. But as the Nitrous Acid is considerably weaker, and much lighter, than the Vitriolic Acid, a good deal of it rises along with the Acid of Sea-salt during the operation. The liquor found in the receiver is therefore a true _Aqua regis_.

If decrepitated Salt, and a right smoking Spirit of Nitre, be employed in this process, the _Aqua regis_ obtained will be very strong; and, during the operation, very elastic vapours will rush out and burst the vessels, if those precautions be not taken which we pointed out as necessary in distilling the Spirit of Nitre, and the smoking Spirit of Salt.

The operation being finished, there is left in the retort a saline mass, containing Sea-salt not decomposed, and a new species of Nitre, which having for its basis the Alkali of Sea-salt, that is, as we have several times observed, an Alkali of a peculiar nature, differs from the common Nitre, 1. In the figure of its crystals; which are solids of four sides, formed like lozenges: 2. In that it crystallizes with more difficulty, retains more water in its crystals, attracts the moisture of the air, and dissolves in water with the same circumstances as Sea-salt.

CHAP. IV.

_Of_ BORAX.

PROCESS.

_To decompose Borax by the means of Acids, and to separate from it the Sedative Salt by sublimation and by crystallization._

Reduce to a fine powder the Borax from which you intend to extract the Sedative Salt. Put this powder into a wide-necked glass retort. Pour upon it an eighth part of its weight of common water, to moisten the powder; and then add concentrated Oil of Vitriol to the weight of somewhat more than a fourth part of the weight of Borax. Set the retort in a reverberatory, make a moderate fire at first, and augment it gradually till the retort become red-hot.

A little phlegm will first come over, and then with the last moisture that the heat expels the Sedative Salt will rise; by which means some of it will be dissolved in this last phlegm, and pass therewith into the receiver; but most of it will adhere in the form of saline flowers to the fore-part of the neck of the retort, just where it is clear of the groove of the furnace. There they collect into a heap, which the succeeding flowers push insensibly forward till they slightly stop the passage. Those which rise after the neck is thus stopped stick to the after-part of it which is hot, vitrify in some measure, and form a circle of fused Salt. In this state the flowers of the Sedative Salt seem to issue out of the circle, as from their basis: they appear like very thin, light, shining scales, and must be brushed off with a feather.

At the bottom of the retort will be left a saline mass: dissolve this in a sufficient quantity of hot water; filter the solution in order to free it from a brown earth which it deposites; set the liquor to evaporate, and crystals of Sedative Salt will form in it.

_OBSERVATIONS._

Though Borax is of great use in many chymical operations, especially in the fusion of metals, as we shall have occasion to see, yet, till of late years, Chymists were quite ignorant of its nature, as they still are of its origin; concerning which we know nothing with certainty, but that it comes rough from the East Indies, and is purified by the Dutch.

M. Homberg was one of the first that attempted to analyse this Salt. He shewed, that on mixing it with the Vitriolic Acid, and distilling the mixture, a salt sublimes in little fine needles. This product of Borax he called by the name of _Sedative Salt_, because he found it had the property of moderating the great tumult and heat of the blood in fevers.

After M. Homberg, other Chymists also exercised themselves on Borax. M. Lemery discovered that the Vitriolic is not the only Acid by means of which the Sedative Salt may be obtained from Borax; but that either of the other two Mineral Acids, the Nitrous or the Marine, may be used in its stead.

M. Geoffroy hath greatly facilitated the means of obtaining the Sedative Salt from Borax; having shewn that it may be extracted by crystallization as well as by sublimation; and that the Sedative Salt so obtained is in no respect inferior to that which was procured before by sublimation only. To him also we are indebted for the discovery, that in the composition of Borax there is an Alkaline Salt of the same nature as the basis of Sea-salt. This he found by observing that he got a Glauber's Salt from a solution of Borax into which he had poured some Vitriolic Acid with a view to obtain its Sedative Salt.

Lastly, M. Baron, whom we mentioned before on occasion of this Salt, hath proved, by a great number of experiments, that a Sedative Salt may be procured from Borax by the help of Vegetable Acids, which was never done by any body before him; that the Sedative Salt is not a combination of an Alkaline matter with the Acid made use of in extracting it, as some of its properties seemed to indicate; but that it exists previously and completely formed in the Borax; that the Acid employed to extract it only helps to disengage it from the Alkali with which it is united; that this Alkali is actually of the same nature as the basis of Sea-salt, because that after extracting the Sedative Salt, which by its union therewith forms the Borax, a Neutral Salt is found, of the same sort with that which would be produced by combining the basis of Sea-salt with the particular Acid made use of; that is, if with the Vitriolic Acid, a Glauber's Salt; if with the Nitrous Acid, a quadrangular Nitre; and if with the Marine Acid, a true Sea-salt; and, lastly, that the Sedative Salt may be re-united to its Alkali, and reproduce a Borax.

Nothing therefore now remains, to give us all the insight we can desire into the nature of Borax, but to know what the Sedative Salt is. M. Baron hath already given us certain negative notices concerning it, by shewing what it is not; that is, that the Acid employed in its extraction doth not enter into its composition. We have great reason to hope, that he will carry his inquiries still further, and clear up all our doubts on this subject.

The Sedative Salt may be extracted from Borax, not only by the means of pure and simple Acids, but also by the same Acids combined with a metallic basis. Thus Vitriols, for instance, may be employed for this purpose with good success. It is easy to see, that the Vitriol must be decomposed on this occasion, and that its Acid cannot unite with the Alkali in which the Sedative Salt is lodged, without quitting its metallic basis, which must of course precipitate.

The Sedative Salt actually sublimes, when a liquid containing it is distilled; but it does not therefore follow, that it is naturally volatile. It rises only by the aid of the water with which it is mixed. The proof of this assertion is, that, when all the humidity of the mixture containing this Salt is dissipated, no more Salt will rise, be the fire ever so violent; and that by adding more water to moisten the dried mass containing it, more Salt will every time be obtained, through many repeated distillations. In the same manner, if some Sedative Salt be moistened, and exposed to a proper degree of heat, a small quantity thereof will rise at first by the help of the water; but as soon as it grows dry it remains exceedingly fixed. This observation we owe to M. Rouelle.

The Sedative Salt hath the appearance and the taste of a Neutral Salt: it does not change the colour of the juice of violets; nor does it easily dissolve in water; for it requires a quart of boiling water to dissolve two ounces of it: yet, with regard to Alkalis, it has the properties of an Acid; it unites with those salts, forms therewith a saline compound which crystallizes, and even expels the Acids that happen to be combined with them; so that it decomposes the same Neutral Salts that are decomposed by the Vitriolic Acid.

The Sedative Salt, when suddenly exposed to the violent heat of a naked fire, loses near half its weight, melts, puts on and retains the appearance of glass; but its nature still remains unchanged. This glass dissolves in water, and shoots anew into crystals of Sedative Salt. This Salt communicates to the Alkaline salt with which it is united, when in the form of Borax, the property of melting with a moderate heat, and forming a kind of glass; and it is this great fusibility that recommends the frequent use of Borax as a flux for assaying ores. It is also employed sometimes as an ingredient in the composition of glass; but, in time, it always communicates thereto the fault which its own glass hath, namely that of tarnishing with the air. The Sedative Salt hath, moreover, the singular property of dissolving in Spirit of Wine, and of giving to its flame, when set on fire, a beautiful green colour. All these observations we owe to Mess. Geoffroy and Baron.

M. Geoffroy prepares the Sedative Salt by crystallization only, in the following manner. "He dissolves four ounces of refined Borax in a sufficient quantity of warm water, and then pours into the solution one ounce and two drams of highly concentrated Oil of Vitriol, which makes a crackling noise as it falls in. When this mixture has stood evaporating for some time, the Sedative Salt begins to make its appearance in little, fine, shining plates floating on the surface of the liquor. The evaporation is then to be stopped, and the plates will by little and little increase in thickness and breadth. They unite together into little tufts, forming with each other sundry different groups. If the vessel be ever so little stirred, the regularity of the crystals will be disturbed; so that it must not be touched till the crystallization appears to be finished. The crystalline clusters, being grown too bulky and too heavy, will then fall of themselves to the bottom of the vessel. This being observed, the saline liquor must be gently decanted from those little crystals, which, as they are not easily dissolved, must be washed clean, by pouring cold water slowly on the sides of the pan, three or four times successively, in order to rinse out all remains of the saline liquor, and then set first to drain, and afterwards to dry in the sun. This Salt, in the form of light flakes of snow, is now soft to the touch, cool in the mouth, slightly bitter, crackling a little between the teeth, and leaving a small impression of acidity on the tongue. It will keep long without giving or calcining, if managed according to the preceding directions; that is, if it be exactly freed from its saline liquor.

"It differs from the Sedative Salt obtained by sublimation in this respect only, that notwithstanding its seeming lightness it is a little heavier than the other. M. Geoffroy supposes the cause of this weight to be, that, as several of the thin plates adhere together in crystallizing, they retain between them some small matter of humidity; or, if you will, that, as they form larger crystals, they present less surface to the air which elevates light bodies: whereas, on the contrary, the other Sedative Salt, being driven up by the force of fire, rises into the head of the cucurbit in a more subtile form, having its particles much more expanded and divided.

"M. Geoffroy, having put his Sedative Salt made by crystallization to all the same trials with that made by sublimation, satisfied himself that there is no other difference between the two. If the Sedative Salt made by crystallizations happens to calcine in the sun; that is, if its lustre tarnishes, and its surface grows mealy, it is a sign that it still contains either a little Borax or some Glauber's Salt: for these two Salts are apt to calcine in this manner, and pure Sedative Salt should not be subject to this inconvenience. In order to purify it, and free it entirely from those Salts, it must be dissolved once more in boiling water. As soon as the water cools, the Sedative Salt reappears in light, shining, crystalline plates, swimming in the liquor. After standing four and twenty hours, the liquor must be decanted, and the salt washed with fresh water; by which means it will be very pure and beautiful."

Glauber's Salt and Borax dissolve in water with vastly more ease than the Sedative Salt, and consequently do not crystallize so readily by much: so that the small portion of those salts which may have been left on the surface of the Sedative Salt, being diffused through a large quantity of water, continues in a state of solution, while the Sedative Salt crystallizes; which being also washed afterwards with fair water, it is impossible that the smallest particle of those other Salts should remain adhering to it; and consequently this must be deemed an excellent way of purifying it.