Part 10

As this matter, heated alone and without any addition, is very difficult to reduce into a mass, as by the fire of a burning mirror we can obtain only very small masses, and as the hydrostatical experiments made on small volumes are so defective, that we cannot conclude any thing therefrom, it appears to me that the chemists have been deceived in their estimation of the specific gravity of this mineral. I put some powder of gold in a little quill, which I weighed very exactly; I put in the same quill an equal volume of platina, and it weighed nearly a tenth less; but this gold powder was much too fine in comparison of the platina. M. Tillet, who besides a profound knowledge of metals, possessed the talent of making experiments with the greatest precision, repeated, at my request, this experiment upon the specific weight of the platina, compared to pure gold; for this purpose, he, like me, made use of a quill, and cut gold of 24 carats, reduced as much as possible to the size of the grains of platina, and he found, by eight experiments, that the weight of platina differed from that of pure gold very near a fifteenth? but we both observed that the grains of gold had much sharper angles than the platina: all the angles of the latter were blunt, and even soft, whereas the grains of this gold had sharp and cutting angles, so that they could not adjust themselves, nor heap one on the other as easily as those of platina. The gold powder I had before made use of was such as is found in river sand, whose grains adjust themselves much better one against the other, and I found a about a tenth difference between the specific weight of those and platina; nevertheless, those are not pure gold, more than two or three carats being often wanting, which must diminish the specific weight in the same relation. Thus we have thought we might maintain, from the result of my experiments, that platina in grains, and such as Nature produces it, is, at least, an eleventh, or twelfth, lighter than gold. There is every reason to presume that the error on the density of platina, proceeded from its not having been weighed in its natural state, but only after it had been reduced into a mass; and as this fusion cannot be made but by the addition of other matters, and a very fierce fire, it is no longer pure platina, but a composition in which fusing matters are entered, and from which fire has taken the lightest parts.

Platina, therefore, instead of being of a density almost equal to that of pure gold, as has been asserted, is only a density between that of gold and iron, and only nearer this first metal than the last. For supposing that the cube foot of gold weighed 1326 lb and that of iron 280, that of platina in grains will be found to weigh about 1194 lb. which supposes more than 3/4 of gold to 1/4 of iron in this alloy, if there is no penetration; but as we extract 6/7 by the loadstone, it might be thought, that there is more than 1/4 iron therein: especially as by continuing this experiment, I am persuaded, we should be able, with a strong loadstone to bring away all the platina even to the last grain. Nevertheless, we must not conclude that iron is contained therein in so great a quantity; for when it is mixed by the fusion with gold, the mass which results from this alloy is attractable by the loadstone, although the iron is in no great quantity therein. M. Baume had a piece of this alloy weighing 66 grains, in which was only entered 6 grains, that is, 1/11 of iron, and this button was easily taken up by the loadstone. Hence the platina might possibly contain only 1/11 iron, or 16/11 gold, and yet be attracted entirely by the loadstone; and this perfectly agrees with the specific weight which is 1/12 less than gold.

But what makes me presume, that platina contains more than 1/11 of iron, or 16/11 of gold, is, that the alloy from this proportion is still of the gold colour, and much yellower than the highest coloured platina, and that 1/4 iron, or 3/4 gold is requisite for the alloy to be precisely of the natural colour of platina. I am, therefore, greatly inclined to think that there might possibly be this quantity of 1/4 iron in platina. We were assured by many experiments, that the sand of this pure iron which contained platina, is heavier than the filings of common iron. Thus, this cause, added to the effect of penetration, is sufficient for the reason of this great quantity of iron contained under the small volume indicated by the specific weight of platina.

On the whole, it is very possible that I may be deceived in some of the consequences which I have drawn from my observations on this metallic substance: for I have not been able to make so profound an examination as I could wish; and what I say is only what I have observed, which may perhaps serve as a stimulus to other and better researches.

Chance led me to tell my ideas to Conte de Milly, who declared himself nearly of my opinion. I gave him the preceding remarks to inspect, and two days after he favoured me with the following observations, and which he has permitted me to publish.

"I weighed exactly thirty-six grains of platina; I laid them on a sheet of white paper that I might observe them the better with a magnifying glass: I perceived three different substances; the first had the metallic lustre, and was the most abundant; the second, drawing a little on the black, very nearly resembled a ferruginous metallic matter, which could undergo a considerable degree of fire, such as the scoria of iron, vulgarly called _machefer_: the third less abundant than the two first, i. e. sand, where the yellow, or topaz colour, is the most predominant. Each grain of sand, considered separate, offered to the sight regular chrystals of different colours. I remarked some in an hexagon form, terminating in pyramids like rock chrystal; and this sand seems to be no other than a _detritus_ of chrystal, or quartz of different colours.

"I resolved on separating, as exactly as possible, these different substances, by means of the loadstone, and to put aside the parts most attractable by the loadstone, from those which were less, and both from those which were not so at all; then to examine each substance particularly, and to submit them to different chemical and mechanical heats.

"I separated these parts of the platina which were briskly attracted at the distance of two or three lines; that is to say, without the contact of the loadstone; and for this experiment I made use of a good fictious magnet; I afterwards touched the metal with this magnet, and carried off all that would yield to the magnetical force. Being scarcely any longer attractable, I weighed what remained, and which I shall call No. 4; it was twenty-four grains; No. 1, which was the most sensible to the magnet, weighed four grains; No. 2 weighed the same; and No. 3, five grains

"No. 1, examined by the magnifying glass, presented only a mixture of metallic parts, a white sand bordering on the greyish, flat and round, or black vitriform sand, resembling pounded scoria, in which very rusty parts are perceptible: in short, such as the scoria of iron presents after having been exposed to moisture.

"No. 2 presented nearly the same, excepting that the metallic parts predominated, and that there were very few rusty particles.

"No. 3 was the same, but the metallic parts were more voluminous; they resembled melted metal which had been thrown into water to be granulated; they were flat, and of all sorts of figures, rounded on the corners.

"No. 4, which had not been carried off by the magnet (but some parts of which still afforded marks of sensibility to magnetism, when the magnet was moved under the paper where they were in), was a mixture of sand, metallic parts, and real scoria, friable between the fingers, and which blackened in the same manner as common scoria. The sand seemed to be composed of small rock, topaz, and cornelian chrystals. I broke some on a steel, and the powder was like varnish, reduced into powder; I did the same to the scoria; it broke with the greatest facility, and presented a black powder which blackened the paper like the common.

"The metallic parts of this last (No. 4) appeared more ductile under the hammer than those of No. 1, which made me imagine they contained less iron than the first: from whence it follows, that platina may possibly be no more than a mixture of iron and gold made by Nature, or perhaps by the hands of men.

"I endeavoured to examine, by every possible means, the nature of platina: to assure myself of the presence of iron of platina by chemical means, I took No. 1, which was very attractable by the magnet, and No. 4, which was not; I sprinkled them with fuming spirit of nitre; I immediately observed it with the microscope, but perceived no effervescence: I added distilled water thereon, and it still made no motion, but the metallic parts acquired new brilliancy, like silver: I let this mixture rest for five or six minutes, and having still added water, I threw some drops of alkaline liquor saturated with the colouring matter of Prussian blue, and very fine Prussian blue was afforded me on the first.

"No. 4, treated in the same manner, gave the same result. There are two things very singular to remark in these experiments; first, that it passes current among chemists who have treated on the platina, that aquafortis, or spirit of nitre, has no action on it. Yet, as I have just observed, it dissolves it sufficiently, though without effervescence, to afford Prussian blue, when we add the alkaline liquor phlogisticated and saturated with the colouring matter, which, as is known, participates iron into Prussian blue.

"Secondly, Platina, which is not sensible to the magnet, does not contain less iron, since spirits of nitre dissolves it enough, and without effervescence, to make Prussian blue. Whence it follows, that this substance, which modern chemists, perhaps too greedy of the marvellous, and too willing to give something novel, have considered as a ninth metal, may possibly be only a mixture of gold and iron.

"Without doubt there still require many experiments to determine how this mixture has taken place, if it be the work of Nature or the effects of some volcano, or simply the produce of the Spaniards' labours in the New World to acquire gold in the mines of Peru.

"If we rub platina on white linen it blackens it like common scoria, which made me suspect that it was the parts of iron reduced into scoria which are found in this platina, and give it this colour, and which seem, in this state, only to have undergone the action of a violent fire. Besides, having a second time examined platina with my lens, I perceived therein different globules of liquid mercury, which made me suppose that platina might be the produce of the hands of man, in the following manner:--Platina, as I have been told, is taken out of the oldest mines in Peru, which the Spaniards explored after the conquest of the New World. In those dark times only two methods were known of extracting gold from the sands which contained it; first, by an amalgama with mercury; secondly, by drying it. The golden sand was triturated with quicksilver, and when that was judged to be loaded with the greatest part of the gold, the sand was thrown away, which was named _crasse_, as useless and of no value.

"The other method was adopted with as little judgment; to extract it they began by mineralising auriferous metals by means of sulphur, which has no action on gold, the specific weight being greater than that of other metals: but to facilitate its precipitation iron was added, which loaded itself with the superabundant sulphur, and this method is still followed. The force of fire vitrifies one part of the iron, the other combines itself with a small portion of the gold, or even silver, which mixes with the scoria, from whence it cannot be drawn but by strong fusions, and being well instructed in the suitable intermediums which are made use of. Chemistry, which is now arrived to great perfection, affords, in fact, means to extract the greatest part of this gold and silver: but at the time when the Spaniards explored the mines of Peru, they were, doubtless, ignorant of the art of mining with the greatest profit; besides, they had such great riches at their disposal that they, probably, neglected the means which would have cost them trouble, care, and time; there is much reason therefore to conclude that they contented themselves with a first fusion, and threw away the scoria as useless, as well as the sand which had escaped the quicksilver, and perhaps they made a mere heap of these two mixtures, which they regarded as of no value.

"These scoria contained gold and silver, iron under different states, and that in different proportions unknown to us, but which, perhaps, are those that gave origin to the platina. The globules of quicksilver which I observed, and those of gold which I distinctly saw, with the assistance of a good lens, in the platina I had in my hands, have given birth to the ideas which I have written on the origin of this mineral; but I only give them as hazardous conjectures. To acquire some certainty we must know precisely where the platina mines are situated, and examine if they have been anciently explored, whether it be extracted from a new soil, or if the mines be only rubbish, and to what depth they are found; and, lastly, if they have any appearance of being placed by the hands of man there or not, which alone can verify or destroy the conjectures I have advanced."[D]

[D] Baron Siekengen, minister of the elector Palatine, told M. de Milly, that he had then in his possession two memoirs which had been given to him by M. Kellner, chemist and metallurgist in the service of the Prince of Birckenfeld, at Manheim, and which offered to the court of Spain to return nearly as much gold as they would send him platina.

These observations of Comte de Milly confirm mine in almost every point. Nature is the same, and presents herself always the same to those who know how to observe her: thus we must not be surprized that, without any communication, we observed the same things, and deduced the same consequence therefrom; that platina is not a new metal, different from every other, but a mixture of iron and gold. To reconcile his observations still more with mine, and to enlighten, at the same time, the doubts which remain on the origin and formation of platina, I have thought it necessary to add the following remarks:

1. The Comte de Milly distinguishes three kinds of matters in platina, namely, two, metallic, and the third, non-metallic, of a chrystalline form and substance. He observed, as well as I, that one of the metallic matters is very attractable by the magnet, and the other but little, or not at all. I mentioned these two matters as well as he, but I did not speak of the third, which is not metallic, because there was none, or very little, on the platina on which I made my observations. It is possible that the platina which the Comte made use of was not so pure as mine, which, I observed with the greatest care, and in which I saw only some small transparent globules, like white melted glass, which were united to the particles of platina, or ferruginous sand, and which were carried any where by the magnet. These transparent globules were very few, and in eight ounces of platina which I narrowly inspected with a very strong lens, I never perceived regular crystals. It rather appeared to me that all the transparent particles were globulous, like melted glass, and all attached to metallic parts; nevertheless, as I did not in the least doubt the veracity of the Comte de Milly's observation, who observed chrystalline particles of a regular form, and in a great number, in his platina, I thought I ought not to confine myself solely to the examination of that platina of which I have spoken; and finding some in the king's cabinet, M. Daubenton and I examined it together: this appeared to be much less pure than that we had before made our experiments on; and in it we remarked a great number of small prismatic and transparent crystals, some of a ruby colour, others of a topaz, and others perfectly white, which convinced us of the correctness of the Comte de Milly in his observations; but this only proves that there are some mines of platina much more pure than others, and that in those which are the most so, none of these foreign bodies are found. M. Daubenton also remarked some grains flat at bottom and rough at top, like melted metal cooled on a plain, and I very distinctly saw one of these hemispherical grains, which might indicate that platina is a matter that has been melted by the fire; but it is very singular, that in this matter, if melted by fire, small crystals, topaz, and rubies, are found; and I know not whether we ought not to suspect fraud in those who supplied this platina, who, to increase the quantity, mixed it with these crystalline sands, for I never met with these crystals but in one half pound of platina given me by the Comte de Angilliviers.

2. I, as well as Comte de Milly, found gold sand in platina; it is readily discovered by its colour, and because it is not magnetical; but I own that I never perceived the globules of mercury which he states to have done; yet I do not mean therefore to deny their existence, only that it appears to me that the sand of gold meeting with the globules of mercury, in the same matter, they might be soon amalgamated, and not retain the colour of gold, which I have remarked in all the gold sand that I could find in half a pound of platina; besides, the transparent globules, which I have just spoken of, resemble greatly the globules of live and shining mercury, insomuch that at the first glance it is easy to be deceived in them.

3. There were by no means so many tarnished and rusty parts in my first platina as in that of Comte de Milly's, nor was it properly a rust which covered the surface of those ferruginous particles, but a black substance produced by fire, and perfectly similar to that which covers the surface of burnt iron. But my second platina, that which I had from the royal cabinet, had a mixture of some ferruginous parts, which under the hammer were reduced into a yellow powder, and had all the characters of rust. This platina therefore of the royal cabinet, and that of Comte de Milly, resembling in every respect, it is probable that they proceeded from the same part, and by the same road. I even suspect that both had been sophisticated and mixed nearly one half with foreign crystalline and ferruginous rusty matters, which are not to be met with in the natural platina.

4. The production of Prussian blue by platina appears evidently to prove the presence of iron in those parts even of this mineral which are the least attractable to the magnet, and at the same time confirms what I have advanced on the intimate mixture of iron in its substance. The flowing of platina by spirits of nitre, also proves that although it has no sensible effervescence, this acid attracts the platina in an evident manner; and the authors who have asserted the contrary, have followed their common track, which consists in looking on all actions as null which do not produce an effervescence. These second experiments of the Comte de Milly would appear to me very important, if they succeeded always alike.

5. We must however admit that many essential points of information are wanting to pronounce affirmatively on the origin of platina. We know nothing of the natural history of his mineral, and we cannot too greatly exhort those who are able to examine it on the spot, to make known their observations; and until that is done we must confine ourselves to conjectures, some of which appear only more probable than others. For example, I do not imagine platina to be the work of man. The Mexicans and Peruvians knew how to cast and work gold before the arrival of the Spaniards, and they were not acquainted with iron, which nevertheless they must have employed in a great quantity. The Spaniards themselves did not establish furnaces in this country when they first inhabited it to fuse iron. There is, therefore, every reason to conclude, that they did not make use of the filings of iron for the separation of gold, at least in the beginning of their labours, which does not go above two centuries and a half back; a time much too short for so plentiful a production as platina, which is found in large quantities in many places.

Besides, when gold is mixed with iron, by fusing them together, we may always, by a chemical process, separate them, and extract the gold: whereas, hitherto, chemists have not been able to make this separation in platina, nor determine the quantity of gold contained in this mineral. This seems to prove, that gold is united with it in a more intimate manner than the common alloy, and that iron is also in it, in a different state from that of common iron. Platina, therefore, appears to me to be the production of nature, and I am greatly inclined to think, that it owes its first origin to the fire of volcanos. Burnt iron, intimately united with gold by sublimation, or fusion, may have produced this mineral, which having been at first formed by the action of the fiercest fire, will afterwards have felt the impression of water, and reiterated frictions, which have given it the form of blunt angles. But water alone might have produced platina; for supposing gold and iron divided as much as possible by the humid mode, their molecules, by uniting, will have formed the grains which compose it, and which from the heaviest to the lightest contain gold and iron; the proposition of the chemist who offers to render _nearly_ as much gold as they shall furnish him with platina, seems to indicate, that there is, in fact, only 1/11 of iron to 10/11 of gold in this mineral, or possibly less. But the _nearly_ of this chemist is perhaps a fifth, or fourth, and indeed, if he could realize his promise to a fourth, it would be doing a great deal, and no vain boast.

Being at Dijon the summer of 1773, the Academy of Sciences and Belles Letters, of which I have the honour to be a member, expressed a desire of hearing my observations on platina; and having complied, M. de Morveau resolved to make some experiments on this mineral; for which purpose I gave him a portion of that which I had attracted by the loadstone, and also some which I had found insensible to magnetism, requesting him to expose it to the strongest fire he could possibly make. Some time after, he sent me the following experiments, which he was pleased to subjoin to mine.

"Monsieur the Comte de Buffon, in a journey to Dijon, in the summer of 1773, having caused me to remark in half a drachm of platina, which M. de Baume had sent him in 1768, grains in form of buttons, others flatter, and some black and scaly; and having separated by the loadstone those which are attractable from those which appeared not so, I tried to form Prussian blue with both. I sprinkled the fuming nitrous acid on the non-attractable parts, which weighed 2-1/2 grains. Six hours after I put distilled water on the acid, and sprinkled alkaline liquor, saturated with a colouring matter; however there was not a single atom of blue, the platina had only a little more brightness. I alike sprinkled the fuming acid on the remaining platina, part of which was attractable, the same Prussian alkali precipitated a blue feculency, which covered the bottom of a pretty large bason. The platina, after this operation, shewed like the first. I washed and dried it, and found it had not lost 1/4 of a grain, or 1/138 part; having examined it in this state I perceived a grain of beautiful yellow, which was pure gold.