Chapter LXII: Part III: Of Operations on Animal Substances (2)

The first is, that Bones yielded to boiling water their principles and their Volatile Salts, both sooner and more copiously than flesh did: for in the analysis which Mr. Geoffroy made of several sorts of flesh, though he robbed them in a manner of all their principles by boiling, yet their dried fibres afterwards yielded a considerable quantity of Volatile Salt; whereas the Bones, of which he had made an extract by boiling, afforded him but a very small quantity thereof when analyzed.

The second observation worthy of notice which Mr. Geoffroy made on his analysis of Bones is this; the Salt, which, as was shewn in the analysis of flesh, was resolved by the water wherein he boiled the flesh, and consequently arose when he distilled the extract obtained from that decoction, and crystallized in the form of parallelopipeds, took a quite different turn in the analysis of Bones. None of it appeared in distilling the extract made by decoction, but arose in distilling the boiled Bones, that were exhausted of almost all their other principles by the decoction with water. These differences probably arise from the different contexture of the animal matters in which they are observed.

This analysis of Bones may serve as a pattern for analyzing all the solid parts of animals, such as horns, hoofs, ivory, &c.

PROCESS IV.

_Animal Fat analyzed. Instanced in Mutton-Suet._

Put as much Mutton-Suet as you please into a glass retort, only taking care that the vessel be but half-full; and distil with degrees of fire as usual. A phlegm smelling of the Suet will rise first, and soon grow very acid. After this some drops of Oil will come over, and be followed by a matter like Oil, in appearance, when it comes over; but it will fix in the receiver, and acquire a consistence somewhat softer than Suet. This kind of Butter of Suet will continue to rise to the end of the distillation; and there will be left in the retort a small quantity of charred matter.

_OBSERVATIONS._

Though animal Fat be a substance that hath passed through all the strainers of the body; though it hath undergone all the elaborations necessary to form an animal matter, and become itself part of the animal: it contains, nevertheless, as its analysis shews, principles differing greatly from those of all other animal matters: so that it must be classed, in some sort, by itself.

It consists almost entirely of Oil: but this Oil is in a concrete form, and observes the general rule of all concreted oily matters, which owe their consistence wholly to the Acid that is combined with them. The rule is evidently so general, that it extends even to the animal kingdom, where, in all other instances, Acids seem to be almost annihilated.

All we said above on the subject of Butter must be applied here: for animal Fat, properly so called, and Butter, do not, in my opinion, differ sensibly from each other, with respect to their analysis. And therefore there is great reason to believe, that what is Butter in Chyle, or Milk, becomes Fat when fixed in the animal body. It is a kind of repository, in which nature lays up and confines the Acid that is unnecessary to the animal composition, and which she could not any other way eliminate.

I made choice of Mutton-Suet for an instance of the analysis of Fat; because this Fat, being the firmest of any, must contain a stronger and more perceptible Acid.

When it is thus distilled, the part which remains fixed hath much less consistence than the Suet had before; which arises from its having lost part of its Acid. Repeated distillations will deprive it of a much greater quantity thereof, and so reduce it into an Oil that will always remain clear and fluid.

Not one particle of Volatile Alkali is obtained by distilling Suet: but then the experiment will not succeed as it ought, unless care be taken to free the Suet perfectly from all the membranes, and all the particles of flesh and blood that may be mixed with it; for, if it should be distilled without this precaution, those heterogeneous matters mingled with it would yield a great deal of Volatile Alkali in distillation; which might impose on the Artist, and make him think the Salt came actually from the Suet. Suet that hath been often melted, as the tallow, for instance, of which candles are made, is sufficiently purified: of this I made use in my analysis, and it yielded me no Volatile Alkali; at least I could perceive none.

In conclusion, all that hath been said, on several occasions, touching the properties of concreted oily matters, may be applied to Suet. I shall only observe here, that it is one of those that manifest no Acidity, and consequently that in its natural state it is not soluble in Spirit of Wine, and only becomes soluble in that menstruum by degrees, as its Acid is extricated by repeated distillations: and on this account it ought to be classed with Bees-Wax, and other oily compounds of that kind.

PROCESS V.

_Eggs analyzed. Instanced in Pullet's Eggs._

Put some Hen's Eggs in water, and boil them till they be hard. Then separate the Yelks from the Whites. Cut the Whites into little bits; put them into a glass cucurbit; fit on a head and receiver; distil in a _balneum mariæ_ with degrees of fire, raising it towards the end to the strongest heat which that bath can give; that is, to the heat of boiling water. There will come over an aqueous liquor, or insipid phlegm; the quantity whereof will be very considerable, seeing it will make about nine-tenths of the whole mass of the Whites of the Eggs. Continue your distillation, and keep the water in the bath constantly boiling, till not a drop more of liquor will ascend from the alembic. Then unlute your vessels. In the cucurbit you will find your Whites of Eggs considerably shrunk in their bulk. They will look like little bits of brown glass, and be hard and brittle.

Put this residuum into a glass retort, and distil, as usual, in a reverberating furnace with degrees of heat. There will come over a Volatile Oily Spirit, a yellow Oil, a Volatile Salt in a dry form, and, at last, a black thick Oil. There will be left in the retort a charred matter.

Reduce also into the smallest pieces you can the hard Yelks of the Eggs which you separated from the Whites. Set them in a pan over a gentle fire: stir them with a stick till they turn a little brown, and discharge a substance like melted marrow. Then put them into a new strong canvass bag, and press them between two iron plates well heated; whereby you will obtain a considerable quantity of a yellow Oil.

Let what remains in the bag be distilled in a retort set in a reverberating furnace: it will give you the same principles as you got from the Whites.

_OBSERVATIONS._

Of the two perfectly distinct substances that constitute the Egg, the Yelk contains the embryo of the chick, and is destined to hatch it: the White is to serve for the nourishment of the chick when it is formed.

These two matters, though they contain the very same principles, yet differ considerably from each other; and chiefly in this, that their principles are not in the same proportions.

The White of an Egg contains so much phlegm, that it seems to consist almost totally thereof. All the aqueous liquor, obtained by distilling it in the _balneum mariæ_, is, properly speaking, nothing but pure water; for no Chymical trial can discover in it either an Acid or a Volatile Alkali; or any very perceptible Oily part. And yet it must contain some Oil, because the liquor that rises last is a little bitterish to the taste, and smells somewhat of empyreuma. But the principles from which it derives these properties are in too small quantities to be distinctly perceived.

If, instead of distilling the hard White of an Egg, with a view to draw off the great quantity of water it contains, you leave it some time in an air that is not too dry, the greatest part of its moisture separates spontaneously, and becomes very sensible. In all probability this is the effect of a beginning putrefaction, which attenuates this substance, and breaks its contexture. The liquor thus discharged by the White of an Egg thoroughly dissolves Gum-Resins, and particularly Myrrh. If you desire to dissolve Myrrh in this manner, cut a hard-boiled Egg in halves; take out the Yelk; put the powdered Gum-Resin into the cavity left by the Yelk; join the two halves of the White; fasten them together with a thread, and hang them up in a cellar. In a few days time the Myrrh will be dissolved by the moisture that issues from the White of the Egg, and will drop into the vessel placed underneath to receive it. This liquor is improperly called _Oil of Myrrh per deliquium_.

All the properties of the Whites of Eggs, as well as the principles obtained by analyzing them, are the same with those of the lymphatic part of the blood; so that there is a great resemblance between these two substances.

As to the Yelk, it is plain from its analysis that Oil is the predominant principle thereof. If the Yelk of an Egg be mixed with water, the Oil with which it is replete, and which is by nature very minutely divided, diffuses itself through the whole liquor, and remains suspended therein by means of its viscosity. The liquor at the same time becomes milk-white like an emulsion, and is in fact a true animal emulsion.

In order to obtain the Oil of Eggs by expression with the more ease, care must be taken to chuse Eggs that are seven or eight days old; because they are then a little less viscous. Nevertheless, their viscosity is still so great that they will not easily yield their Oil by expression: and therefore, in order to attenuate and destroy entirely this viscosity, they must be torrefied before they are put to be pressed.

The Oil of Eggs, like all other oily animal matter, seems analagous to the Fat Oils of vegetables. It hath all the properties that characterise those Oils. Its colour is yellow, and it smells and tastes a little of the empyreuma, occasioned by torrefying the Yelks. It is rendered somewhat less disagreeable by being exposed to the dew for thirty or forty nights, if care be taken to stir it often in the mean time.

To conclude: all the principles, both in the Yelk and the White of an Egg, are the same as those found in Blood, Flesh, and all other matters that are perfectly animal.

CHAP. III.

_Of the_ EXCREMENTS _of_ ANIMALS.

PROCESS I.

_Dung analyzed. Instanced in Human Excrement. Mr. Homberg's Phosphorus._

Take any quantity you please of human Excrement, and distil it in a glass alembic set in the _balneum mariæ_. You will obtain an aqueous, clear, insipid liquor; which will nevertheless have a disagreeable odour. Having urged the distillation as far as is possible, with the heat of this bath, unlute your vessels, and you will find at the bottom of the cucurbit a dry matter, making about an eighth part only of what you put into it. Put this residuum into a glass retort, and distil in a reverberating furnace, with degrees of heat. You will obtain a Volatile Spirit, and a Volatile Salt, with a fetid Oil; and a charred matter will be left in the retort.

_OBSERVATIONS._

Mr. Homberg made a great many experiments on the dung of animals; concerning which he composed two Memoirs published in the Academy's collection for 1711. That Chymist tells us, that, in distilling Excrement, he aimed not so much at discovering the principles of which it consists, as he was desirous to satisfy a friend of his, who had earnestly entreated him to try whether he could not extract therefrom a clear Oil, having no bad smell; because he had seen, as he said, Mercury fixed into pure Silver by such an Oil.

Mr. Homberg's labour had the usual fate of all enterprises of this nature. He actually found the art of drawing from Excrement a clear scentless Oil; but, in whatever way he applied it to Mercury, it produced no change in that metallic substance. However, as Mr. Homberg was a man of sagacity, and knew how to improve every hint offered by his experiments, he made several curious discoveries on this occasion; of which we shall give a concise account, after we have made some remarks on the principles obtained from Excrement by the method described in the process.

This substance, consisting of matters subject to putrefaction, hath constantly a fetid smell, like that of all putrid matters; having been for some time confined in a warm, moist place, which we know promotes putrefaction, and even quickly produces it. Yet the analysis thereof proves that it is not putrefied, or at least not entirely so: for all putrefied matters contain a Volatile Alkali perfectly formed and extricated; and, as this principle rises with less heat than that of boiling water, it always comes over first in distillation. Now we have seen that, with the heat of boiling water, it parts with nothing but an insipid phlegm, containing no Volatile Alkali: a sure proof that the fecal matter is not completely putrefied.

There is nothing remarkable in the Volatile Salt and fetid Oil, which rise with a degree of heat greater than that of boiling water. They are common productions, of which we have made frequent mention in several of the preceding analyses; and therefore they need not now detain us from proceeding to give a summary account of Mr. Homberg's chief discoveries.

One of the methods by which Mr. Homberg endeavoured to obtain from Excrement a clear Oil, without any bad smell, was to separate its earthy and gross parts, by filtering it before he distilled it. "For this purpose he diluted Excrement newly discharged with hot water, using a quart of water to an ounce of feces. Then he let the mixture stand to cool, and, the gross parts falling to the bottom, he poured off the water by inclination. This liquor he filtered through brown paper, and evaporated to a pellicle over a gentle fire. There shot in it long crystals of four, five, and six sides, which Mr. Homberg thinks may be called the Essential Salt of Excrement. They resemble Salt-petre, in some measure, and deflagrate in the fire much like it; with this difference, that their flame is red, and they burn slowly; whereas the flame of Salt-petre is white and very vivid: probably, says Mr. Homberg, because there is too much of an oily matter in the one, and less in the other.

"Mr. Homberg distilled this Salt in a glass retort with degrees of fire, and at last with a very violent one. At first there came over an aqueous liquor, sharp and acid, which was followed by a brown fetid oil, smelling very strong of empyreuma. This distillation he attempted four several times; and each time the matter in the retort took fire, just when the Oil began to come off."

The Salt which Mr. Homberg obtained from excrement is very remarkable. We shall have occasion to speak of it in another place, and shall only observe here, that its Nitrous character is by no means ambiguous: its deflagrating on live coals convinced Mr. Homberg of its being a true Nitre. But its constantly taking fire in the retort, as oft as distilled, is a sure proof that it is a Nitrous Salt: for Nitre only hath the property of thus taking fire in close vessels, and making other combustible matters burn along with it.

The process by which Mr. Homberg at last obtained from Excrement a clear oil without any bad smell is curious, and worthy of a place here; on account of the views and occasions of reflection which it may open.

"Mr. Homberg having tried in vain, by distilling Excrement a great many different ways, to obtain from it such an Oil as he wanted, resolved to employ fermentation, the effect whereof is to change the disposition of the principles of mixts. With this view he dried some Excrement in the water-bath, and, having pulverized it, poured thereon six times its weight of phlegm that had been separated from it by distillation, and put the whole into a large glass cucurbit, covered with an inverted vessel that fitted exactly into it, and was close luted. This vessel he set in a _balneum mariæ_ for six weeks, keeping up such a gentle heat as would not burn one's hand; after which he uncovered the cucurbit, and having fitted thereto a head and a receiver, distilled off all the aqueous moisture in the _balneum mariæ_ with a very gentle heat. It had now lost almost all its bad smell, which was changed into a faint one. It came over somewhat turbid, whereas it was very clear when put into the cucurbit. Mr. Homberg found this water to have a cosmetic virtue: He gave some of it to persons whose complexion, neck, and arms, were quite spoiled, being turned brown, dry, rough, and like a goose skin: they washed with it once a day, and, by continuing the use of this water, their skin became very soft and white."

The dry matter, that remained in the bottom of the cucurbit after distillation, had lost about a twentieth part of its weight; that is, of twenty ounces, put at one time into the cucurbit, somewhat less than nineteen ounces remained. Mr. Homberg suspects that it was not so dry when put into the cucurbit as when it was taken out. Perhaps also the species of fermentation which the matter underwent had attenuated and volatilized some part of it; so that it came over with the phlegm in distillation. The turbidness of that phlegm, which was clear and limpid before, seems to countenance this conjecture.

"The dry matter left in the cucurbit after the first distillation, had not the least smell of feces: on the contrary, it had an agreeable aromatic odour; and the vessel in which Mr. Homberg had digested it, being left open in a corner of his laboratory, acquired in time a strong smell of Ambergris. It is surprising, as Mr. Homberg justly observes, that digestion alone should change the abominable smell of Excrement into an odour as agreeable as that of Ambergris.

"This dry matter he powdered coarsely, and put two ounces thereof at once into a glass retort, that would hold about a pound or a pound and half of water. This he distilled in a sand-bath with a very gentle heat. A small quantity of an aqueous liquor came over first, and then an Oil as colourless as spring-water. Mr. Homberg continued the same gentle degree of heat, till the drops began to come off a little reddish; and then he changed the receiver, stopping that which contained the clear Oil very close with a cork. Having carried on the distillation with a fire gradually augmented, there came over a considerable quantity of red Oil; and there remained in the retort a charred matter which burnt very readily."

The clear Oil, without any ill smell, which Mr. Homberg obtained from the fecal matter by this process, was the very thing he was in search of, and which he had been assured would convert Mercury into fine fixed Silver: yet he ingenuously owns, that, whatever way he applied it, he could never produce any change in that metallic substance. We shall now proceed to the other discoveries made by Mr. Homberg on this occasion.

In his attempt to obtain a clear Oil from Excrement, he distilled it with different additaments, and amongst the rest with Vitriol and Alum. He found that the matters left in the retort, when he made use of these Salts, being exposed to the open air, took fire of themselves; that they kindled combustible matters; in a word, that they were a true Phosphorus, of a species different from all then known. Pursuing these first hints, he sought and found the means of preparing this Phosphorus by a way much more expeditious, certain, and easy. His process is this.

"Take four ounces of Feces newly excreted: Mix therewith an equal weight of Roch-Alum coarsely powdered: put the whole into a little iron pan that will hold about a quart of water, and set it over a gentle fire under a chimney. The mixture will melt, and become as liquid as water. Let it boil with a gentle fire, constantly stirring it; breaking it into little crumbs, and scraping off with a spatula whatever sticks to the bottom or sides of the pan, till it be perfectly dry. The pan must from time to time be removed from the fire, that it may not grow red-hot, and the matter must be stirred, even while it is off the fire, to prevent too much of it from sticking to the pan. When the matter is perfectly dried, and in little clots, let it cool, and powder it in a metal mortar. Then put it again into the pan, set it over the fire, and stir it continually. It will again grow a little moist, and adhere together in clots, which must be continually bruised and roasted till they be perfectly dry; after which they must be suffered to cool, and then be pulverized. This powder must be returned a third time to the pan, set on the fire, roasted and perfectly dried: after which it must be reduced to a fine powder, and kept in a paper in a dry place. This is the first or preparatory operation.

"Take two or three drams of this powder. Put it into a little matrass, the belly of which will hold an ounce or an ounce and half of water, and having a neck about six or seven inches long. Order it so that your powder shall take up no more than about a third part of the matrass. Stop the neck of the matrass slightly with paper: then take a crucible four or five inches deep: in the bottom of the crucible put three or four spoonfuls of sand: set the matrass on this sand, and in the middle of the crucible, so as not to touch its sides. Then fill up the crucible with sand, so that the belly of the matrass may be quite buried therein. This done, place your crucible, with the matrass, in the midst of a little earthen furnace, commonly called a _Stove_, about eight or ten inches wide above, and six inches deep from the mouth to the grate. Round the crucible put lighted coals about half way up, and when it hath stood thus half an hour, fill up with coals to the very top of the crucible. Keep up this fire a full half-hour longer, or till you see the inside of the matrass begin to be red. Then increase your fire, by raising your coals above the crucible. Continue this strong heat for a full hour, and then let the fire go out.

"At the beginning of this operation dense fumes will rise out of the matrass, through the stopple of paper. These fumes issue sometimes in such abundance as to push out the stopple; which you must then replace, and slacken the fire. The fumes cease when the inside of the matrass begins to grow red; and then you may increase the fire without any fear of spoiling your operation.

"When the crucible is so cold that it may be safely taken out of the furnace with one's hand, you must gradually draw the matrass out of the sand, that it may cool slowly, and then stop it close with a cork.

"If the matter at the bottom of the matrass appear to be in powder when shaken, it is a sign the operation hath succeeded: but if it be in a cake, and doth not fall into powder on shaking the matrass, it shews that your matter was not sufficiently roasted and dried in the iron pan, during the preparatory operation."

Since Mr. Homberg, Mr. Lemeri the younger hath made a great many experiments on this Phosphorus, which may be seen in the Memoirs of the Academy for 1714 and 1715. In those Memoirs Mr. Lemeri hath shewn, that Excrement is not the only matter capable of producing this Phosphorus with Alum; but that, on the contrary, almost all animal and even vegetable matters are fit for this combination; that though Mr. Homberg mixed Alum in equal quantities only with the fecal matter, it may be used in a much greater proportion, and, in certain cases, will succeed the better; that, according to the nature of the substances to be worked on, the quantity of that Salt may be more or less increased; and that whatever is added, more than the dose requisite for each matter, serves only to lessen the virtue of the Phosphorus, or even destroys it entirely: that the degree of fire applied must be different according to the nature of those matters; and, lastly, that Salts containing exactly the same Acid with that of Alum, or the Acid of those Salts separated from its basis and reduced into Spirit, do not answer in the present operation: which shews, says Mr. Lemeri, that many sulphureous matters may be substituted for Excrement in this operation; but that there are no Salts, or very few if any, that will succeed in the place of Alum. Nevertheless, a Chymist, who lately communicated to the Academy a great number of experiments on this Phosphorus, found that any Salt containing the Vitriolic Acid may be substituted for Alum.

This Phosphorus, made either by Mr. Homberg's or by Mr. Lemeri's method, shines both by day and by night. Besides emitting light, it takes fire soon after it is exposed to the air, and kindles all combustible matters with which it comes in contact; and this without being rubbed or heated.

Mess. Homberg and Lemeri have given the most probable and the most natural explanation of the cause of the accension and other phenomena of this Phosphorus. What they say amounts in short to what follows.

Alum is known to be a Neutral Salt, consisting of the Vitriolic Acid and a calcareous earth. When this Salt is calcined with the fecal matter, or other substances abounding in Oil, the volatile principles of these substances, such as their Phlegm, their Salts, and their Oils, exhale in the same manner as if they were distilled; and there is nothing left in the matrass, when those principles are dissipated, but a charred matter, like that which is found in retorts wherein such mixts have been decomposed by distillation.

This remainder therefore is nothing but a mixture of Alum and charcoal. Now, as the Acid of this Salt, which is the Vitriolic, hath a greater affinity with the phlogiston than with any other substance, it will quit its basis to unite with the phlogiston of the coal, and be converted by that union into a Sulphur. And this is the very case; of which we have certain proofs in the operation for preparing this Phosphorus: for when, after the volatile principles of the oily matter are drawn off, the fire is increased, in order to combine closely together the fixed parts that remain in the matrass, that is, the Alum and the charred matter, we perceive at the mouth of the matrass a small blue sulphureous flame, and a pungent smell of burning Sulphur. Nay, when the operation is finished, we find a real Sulphur sticking in the neck of the matrass; and, while the Phosphorus is burning, it hath plainly a strong sulphureous smell. It is therefore certain that this Phosphorus contains an actual Sulphur; that is, a matter disposed to take fire with the greatest ease. But though Sulphur be very inflammable, it never takes fire of itself, without being either in contact with some matter that is actually ignited, or else being exposed to a considerable degree of heat. Let us then see what may be the cause of its accension, when it is a constituent part of this Phosphorus.

We mentioned just now that the Acid of the Alum quits its basis, in order to form a Sulphur by combining with the Phlogiston of the coal. This basis we know to be an earth capable of being converted into Lime; and that it is actually converted into Quick-lime by the calcination necessary to produce the Phosphorus. We know that new-made Lime hath the property of uniting with water so readily, that it thereby contracts a very great degree of heat. Now when this Phosphorus, which is partly constituted of the basis of the Alum converted into Quick-lime, is exposed to the air, the Lime instantly attracts the moisture of which the air is always full, and by this means, probably, grows so hot as to fire the Sulphur with which it is mixed. Perhaps also the Acid of the Alum is not totally changed into Sulphur; some part thereof may be only half disengaged from its basis, and in that condition be capable of attracting strongly the humidity of the air, of growing very hot likewise by imbibing the moisture, and so of contributing to the accension of the Phosphorus.

There is also room to think that all the Phlogiston of the charred matter is not employed in the production of Sulphur in this Phosphorus, but that some part of it remains in the state of a true coal. The black colour of the unkindled Phosphorus, and the red sparkles it emits while burning, sufficiently prove this. The explanation of the accension of this Phosphorus, as here given by Mess. Homberg and Lemeri, is very ingenious, and in the main just; but yet, in my opinion, the subject deserves a more thorough examination.

PROCESS II.

_Human Urine analyzed._

Put some Human Urine into a glass Alembic; set it in a water-bath, and distil till there remain only about a fortieth part of what you put in; or else evaporate the Urine, in a pan set in the _balneum mariæ_, till it be reduced to the same quantity. With this heat nothing will exhale but an insipid Phlegm, smelling however like Urine. The residuum will, as the evaporation advances, become of a darker and darker russet, and at last acquire an almost black colour. Mingle this residuum with thrice its weight of sand, and distil it in a retort set in a reverberating furnace, with the usual precautions. At first there will come over a little more insipid Phlegm like the former. When the matter is almost dry, a Volatile Spirit will rise. After this Spirit, white vapours will appear on increasing the fire; a yellow oily liquor will come off, trickling down in veins; and together with this liquor a concrete Volatile Salt, which will stick to the sides of the receiver. At last there will come over a deep-coloured fetid Oil. In the retort there will remain a saline earthy residuum, which being lixiviated will yield some Sea-salt.

_OBSERVATIONS._

Urine must be considered as an aqueous liquor replete with all the saline matters which are of no use to the body, either for nourishment or health: it is a lixivium of animal matters, prepared by nature for dissolving and separating from them all the unnecessary Salts. It contains a very large quantity of almost pure phlegm, which evaporates with the heat of a water-bath.

The residue of the Urine, from which this phlegm is separated by the first distillation, though thereby rendered considerably thicker, doth not coagulate, or curdle in the least, like Milk or Blood; which shews that it contains no parts analagous to those of these two nutritious liquors. Yet it contains oily and saline parts, disposed like those of truly animal matters; as appears from the Spirit, the Volatile Salt, and the Oil, obtained from it by distillation; which are, in every respect, perfectly like the same principles yielded by other animal substances. But, if the animal that made the Urine took in with its food any of the Neutral Salts, which cannot be decompounded by digestion; that is, of those chiefly which consist of Acids and Alkalis, the Urine will contain, over and above the other parts of that animal, almost all the Neutral Salt that entered into its body. Accordingly human Urine is replete with a considerable quantity of Sea-salt, because men eat a great deal of it. It is found, after the distillation of the Urine, united with the _caput mortuum_ left in the retort; because, being of a fixed nature, it doth not rise with the volatile principles in distillation.

Besides this Sea-salt, Urine contains another Salt of a singular nature, which crystallizes differently from Sea-salt. In this Salt, according to Mr. Marggraff's experiments mentioned on the subject of Phosphorus, is contained the Acid necessary to produce the Phosphorus of Urine. There is reason to think that this Salt is a Sea-salt, disguised by the fat matters with which it combines during its stay in the animal body.

Mr. Boerhaave calls it the Essential Salt of Urine. If you desire to have it by itself, you must evaporate the Urine, with a gentle heat, to the consistence of fresh cream, filter it, and let it stand quiet in a cool place. Crystals will at length shoot therein, and adhere to the sides of the vessel. These crystals are the Salt you want: they are brown and oily. If you desire to have them purer, you must dissolve them in warm water, filter the solution, and set it by to shoot. This operation repeated several times will render them clear and transparent. Mr. Schlosser, a young and very promising Chymist, is the last who hath made any experiments on this curious Salt of Urine. Those who are desirous of a particular account of its properties may consult his dissertation, printed at Leyden in 1753, as well as Mr. Marggraff's excellent Memoirs, printed among those of the Academy of Berlin.

The chief result of Mr. Schlosser's experiments is, first, that this Salt may be obtained from recent Urine, and even in greater quantities than from putrid Urine, and that too in very little time: seeing it crystallizes in twenty-four hours, after due evaporation.

Secondly, that this Salt is a Neutral Ammoniacal Salt, consisting of a Volatile Alkali, (which can never be extracted from it but in a liquid form, like that which is separated from Urine by the addition of Lime); and of an Acid of a very singular nature, the most remarkable property of which is, its being so fixed as to resist the violence of fire, and turn into a sort of glass rather than exhale in vapours. This is that Acid which, according to Mr. Marggraff's experiments, forms the combination of Phosphorus when united with the Phlogiston. The other properties of this singular Acid are the principal objects of Mr. Marggraff's inquiries.

It follows, in the third place, from Mr. Schlosser's experiments, that this Acid, being combined to the point of saturation with a common Volatile Alkali, forms a true, regenerated Salt of Urine; and that, by this union, the nature of the Volatile Alkali is so changed, that it cannot afterwards appear by itself in a concrete form, but is always fluid, like that which is extricated by the additament of lime.

If Fixed Alkalis be mixed with fresh Urine, they immediately separate from it a Volatile Alkali; and, if the mixture be quickly put into an alembic, and distilled, the first liquor that rises is a Volatile Spirit: or else a Volatile Alkali in a concrete form will rise first, provided the Fixed Alkali made use of be not liquid, and the Urine be dephlegmated.

Herein Urine resembles other animal matters: for Fixed Alkalis produce the same effect on them. This affords us good grounds for believing that all animal matters contain a Neutral Salt of an Ammoniacal nature, which the Fixed Alkali decomposes, as it doth all other Ammoniacal Salts. Quick-lime also extricates from Urine a Volatile Alkali, still more quick and pungent than that which is separated by a Fixed Alkali, and which constantly remains liquid without ever putting on a concrete form: and this is another proof of the existence of the Ammoniacal Salt above-mentioned; for quick-lime hath just the same effect on Sal-Ammoniac, as we shall see in its place. Mr. Schlosser's experiments, compared with those now mentioned, seem to shew that the Urine contains several distinct sorts of Ammoniacal Salts.

Of all the liquors which animals afford, Urine putrefies the most easily, and by putrefaction parts with, or forms, the greatest quantity of Volatile Alkali. If it be distilled when putrefied, there comes over first a Spirit impregnated with much Volatile Alkali; then an aqueous liquor, which Van Helmont assures us is a medicine of wonderful efficacy in dissolving the stone in the bladder. When all this water is come over, and the remaining matter is almost dry, there ascends, on increasing the fire, a yellow Oil, together with a Volatile Salt.

After this there remains in the retort a black charred earthy matter, containing a great deal of Sea-salt. If this matter be calcined in the open air, in order to consume its Phlogiston, and be afterwards lixiviated, all the Sea-salt it contains may by this means be easily separated; nothing but its earth being left behind. This _caput mortuum_ contains also the materials proper for forming Kunckel's Phosphorus; and if, instead of calcining it in the open air, it be urged with a violent fire, in close vessels, it will yield a Phosphorus: but then all the precautions recommended on the subject of Phosphorus must be used; and, in particular, the _caput mortuum_ must be lixiviated before it be distilled, in order to free it from part of the Sea-salt contained therein; because too much of that Salt might defeat the operator, by not only melting itself, but melting also the containing vessel during the operation.

CHAP. IV.

_Of the_ VOLATILE ALKALI.

PROCESS I.

_Volatile Alkalis rectified and depurated._

Mix together the Spirit, the Volatile Salt, the Phlegm, and the Oil, obtained from any substance whatever. Put the whole into a large wide-mouthed glass body, and thereto fit a head with a large beak. Set this alembic in a water-bath, lute on a receiver, and distil with a very gentle heat. There will ascend a Spirit, strongly impregnated with a Volatile Alkali, and a Volatile Salt in a concrete form, which must be kept by itself. Then increase your heat to the degree of boiling water; whereupon there will rise a second Volatile Spirit, somewhat more ponderous than the former, with a light Oil that will swim on its surface, and a little concrete Volatile Salt. Proceed till nothing more will rise with this degree of heat. Keep by itself what came over into the receiver. At the bottom of the cucurbit you will find a thick fetid Oil.

Into such another distilling vessel put the Spirit and Salt that rose first in this distillation, and distil them in the _balneum mariæ_ with a heat still gentler than before. A whiter, purer, Volatile Salt will sublime. Continue the distillation till an aqueous moisture rise, which will begin to dissolve the Salt. At the bottom of the vessel will be left a phlegm, with a little Oil floating on it. Keep your Salt in a bottle well stopped.

_OBSERVATIONS_.

In the analysis of any substance that yields a Volatile Alkali, this Salt is generally found in the receiver, blended with the other principles of the mixt; which, ascending from the retort in the form of liquors and vapours, dissolve the Salt, or at least moisten it, and render it very impure. So that, if you desire to have it without any mixture, recourse must be had to a second distillation, in order to separate it from the heterogeneous matters with which it is confounded.

It is of consequence in this distillation to apply but a very weak degree of heat; because on that depends the success of the operation, insomuch that, the less heat you employ to sublime the Salt, the purer it will be. For, being far more volatile than any of the other principles with which it is mixed, it must evidently rise by itself, if no more heat be applied than is just necessary to elevate it; such a heat being much too weak to raise the Oil and phlegm with which it is blended.

Nevertheless, whatever care be taken to govern the heat, it is not possible to hinder this Volatile Salt from carrying up some portions of the principles mixed with it; those, to wit, with which it is most closely united, and to which it hath by that means communicated a share of its volatility. For this reason it requires a second rectification, which is performed in the same manner as the former. But, seeing it is more volatile and lighter after the first rectification than before, being thereby freed from part of the heterogeneous matters with which it was loaded, a still less degree of heat must be applied in this second rectification.

The Oil with which the Volatile Salt is loaded, when but once distilled, is perceivable only by the yellow colour and weight it communicates thereto; because it is closely united therewith, and in a perfectly saponaceous state. This appears from the facility with which Volatile Salts, even the most oily, dissolve in water, without discovering in the solution any separation of the oily parts, and even without giving it a milky colour. But, in the second rectification, this Oil becomes very perceptible; for it then separates, in a great measure, from the Salt, and remains at the bottom of the cucurbit, floating on the phlegm, which is also separated from the Salt.

The Salt is then whiter, more volatile, and purer; yet it is still far from being brought to the utmost degree of purity, even by this second rectification. It requires a third, a fourth, and even many more rectifications, to purify it perfectly: every rectification separates from it some oily particles: and if you should resolve to go on rectifying till you can separate no more Oil, there is reason to think this Salt would be entirely decomposed; because there is necessarily a certain quantity of Oil in its composition, without which it would not be a Volatile Alkali. You must therefore desist from rectifying it any further, when you find it very white, and very light; and shut it up in bottles hermetically sealed.

It often happens that Volatile Salts, though of a beautiful white after rectification, grow yellow after being kept some time in close bottles. This is occasioned by the Oil they contain disengaging, and discovering itself by degrees. To remedy this inconvenience, Mr. Boerhaave proposes to mingle the Volatile Salt, which you intend to purify, with four times its weight of pulverized chalk, thoroughly dried, and even heated; to put the mixture into a glass alembic, and distil it with a gentle heat. By this means the Salt rises exceeding pure and very white; because the chalk absorbs most of its Oil, and frees it therefrom. He adds, that Volatile Salt thus purified may be kept a long time, and will retain all its whiteness.

If a Volatile Alkali thus purified be combined, to the point of saturation, with an Acid, such as the Marine Acid for instance; the result of this union, as we shall afterwards see, will be a Sal Ammoniac, from which the Volatile Alkali may be separated by the intervention of a Fixed Alkali. A Volatile Alkali that hath passed through all these trials will then be in the highest degree of purity that Chymistry can bring it to, and appears constantly the same, from whatever substance it was originally obtained: which proves that if Volatile Alkalis, extracted from different vegetable and animal substances, seem to differ from each other in some respects, this can arise only from the heterogeneous matters with which they are mixed; but that, at bottom, they are all constituted of one single principle, which is constantly the same, and exactly alike in them all.

It is of the last consequence, on all occasions where a Volatile Alkali is to be distilled in a concrete form, to make use of subliming vessels with very large necks, that it may have room enough to make its way to the receiver with ease; for otherwise it may choak up the passage, and burst the vessels.

PROCESS II.

_Volatile Alkalis combined with Acids. Sundry Ammoniacal Salts. Sal Ammoniac._

On a Volatile Spirit or Salt pour gradually any Acid whatever. An effervescence will arise, and be more or less violent according to the nature of the Acid. Go on adding more Acid in the same manner, till no effervescence be thereby excited, or at least till it be very small. The liquor will now contain a semi-volatile Neutral Salt, called an _Ammoniacal Salt_; which may be obtained in a dry form by crystallizing as usual, or by subliming it in close vessels, after the superfluous moisture hath been drawn off.

_OBSERVATIONS._

Volatile Alkalis have the same properties with Fixed Alkalis, fixity only excepted: so that a Volatile Alkali must produce an effervescence when mixed with Acids, and form therewith Neutral Salts, differing from each other in nothing but the nature of the Acid in their composition.

It must be observed, that, on this occasion, the point of saturation is very difficult to hit; owing probably to the Volatility of the Alkali, which, being much lighter than the Acid, tends always to possess the uppermost part of the mixture, while the Acid sinks to the bottom: whence it comes to pass, that the lower part of the liquor is sometimes over-charged with Acid, while the upper part is still very Alkaline. But it is most eligible that the Alkali should predominate in the mixture; because the excess of this principle easily flies off, while the moisture is evaporating, in order to the crystallization or sublimation of the Ammoniacal Salt; which being only semi-volatile resists the heat longer, and remains perfectly Neutral.

If the Vitriolic Acid be combined with a Volatile Alkali, and the mixture distilled in a retort to draw off the superfluous moisture, a liquor comes over into the receiver, which smells strong of a Sulphureous Acid. Now, as the Acid of Vitriol never becomes sulphureous, but when it is combined with an inflammable matter, this experiment is one of those which demonstrate that Volatile Alkalis contain a very sensible quantity of inflammable matter. This same liquor tastes of an Ammoniacal Salt; which proves that it carries up with it some of the Neutral Salt contained in the mixture. The rest of this Salt, which is called _Glauber's Secret Sal Ammoniac_, or _Vitriolic Sal Ammoniac_, sublimes into the neck of the retort. It is very pungent on the tongue; it crackles a little when thrown on a red hot shovel, and then flies off in vapours.

The Ammoniacal Salt formed by the Acid of Nitre exhibits much the same phenomena; but it requires greater care in drying and subliming it, because it hath the property of detonating all alone, without the addition of any other inflammable matter: and it will infallibly do so, if too strong a fire be applied towards the end of the operation, when it begins to be very dry. This property of detonating by itself it derives from the inflammable matter contained in the Volatile Alkali which serves for its basis: and this is another demonstrative proof of the existence of such an inflammable matter in the Volatile Alkali. This Salt is called _Nitrous Sal Ammoniac_.

With the vegetable Acids, that of Vinegar for instance, is formed an Ammoniacal Salt of a singular nature, and which can scarce be brought to a dry form.

A Volatile Alkali, combined to the point of saturation with the Acid of Sea-salt, forms another Neutral Salt, which takes a concrete form either by sublimation or crystallization. The crystals of this Salt are so very soft and fine, that a parcel of it looks like cotton or wool. This is the Salt properly called _Sal Ammoniac_. It is of great use in Chymistry and in manufactures: but that which is daily consumed in great quantities is not made in the manner above mentioned. It would come extremely dear if we had no other way of procuring it, but by forming it thus with the Acid of Sea-salt and a Volatile Alkali. This Salt, or at least the materials of which it is formed, may be found in the fuliginosities and soots of most animal, and of some vegetable substances. The greatest part of what we use comes from Egypt, where vast quantities thereof are made.

The method of preparing Sal Ammoniac in Egypt was not known among us, till Mess. Lemaire and Granger, two of the Academy's correspondents, gave in several Memoirs in which that business is described with great accuracy, from their own view on the spot. Their Memoirs inform us, that chimney-soot alone, without any additament, is the matter from which they obtain their Sal Ammoniac; that those chimneys under which nothing is burnt but Cow's-dung furnish the best Soot. Six and twenty pounds of that Soot yield usually six pounds of Sal Ammoniac.

"The operation takes up about fifty, or two and fifty hours. The vessels in which they put the soot are ballons of very thin glass, terminating in a neck of fifteen or sixteen lines long, and an inch in diameter: but they are not all of the same size. The least contain twelve pounds of Soot, and the greatest fifty; but they fill them only three quarters full, in order to leave room for the sublimation of the Salt.

"The furnace, in which they place these ballons, consists of four walls, built in a quadrangular form. The two front walls are ten, and the sides nine feet long: but they are all five feet high, and ten inches thick. Within the quadrangle formed by these walls three arches run lengthwise from end to end thereof, at the distance of ten inches asunder. The mouth of this furnace is in the middle of one of its fronts, and of an oval form; two feet four inches high, and sixteen inches wide.

"The ballons lie in the spaces between the arches of the furnace, which serve instead of a grate to support them. Four of them are usually placed in each interval; which makes sixteen for one furnace. They are set at the distance of about half a foot from each other, and secured in their places with brick and earth. But they leave about four inches on the upper part of the ballon uncovered, with a view to promote the sublimation, as they also do six inches of the inferior part, that the heat may the better act on the matters to be sublimed. Things being thus prepared they first make a fire with straw, which they continue for an hour. Afterwards they throw in Cow's-dung made up in square cakes like bricks. (The want of wood in this country is the reason that they generally make use of this fuel). These cakes of dung add to the violence of the fire, which they continue in this manner for nineteen hours; after which they increase it considerably for fifteen hours more; and then they slacken it by little and little.

"When the matter contained in the vessels begins to grow hot, that is, after six or seven hours baking, it emits a very thick and ill-scented smoke, which continues for fifteen hours. Four hours after that, the Sal Ammoniac is observed to rise in white flowers, which adhere to the inside of the neck of the vessel; and those who have the direction of the operation take care, from time to time, to pass an iron rod into the neck of the ballon, in order to preserve a passage through the saline vault, for giving vent to some blueish vapours, which constantly issue out of the vessel during the whole operation."

From this history of the preparation of Sal Ammoniac it appears that Soot, and particularly the Soot of animal matters, either contains abundance of this Salt perfectly formed, and waiting only for sublimation to separate it therefrom, or, at least, that it contains the proper materials for forming it; and that during the operation, which is a kind of distillation of Soot, these materials combine together and sublime.

We shewed, in our analysis of Soot, that this substance yields by distillation a great deal of Volatile Alkali; and this is an ingredient which makes at least one-half of Sal Ammoniac. As to the other principle of this Salt, I mean the Marine Acid, this also must needs exist in Soot: but it is not so easy to conceive how it should come there.