We have already seen, that of all the Mineral substances which I
subjected to trial it was not the most dense, but the least fusible,
which required the longest time to receive and lose heat. Iron and
emery, which are the most difficult matters to fuse, are, at the same
time, those that heat and cool the slowest. There is nothing except
platina that is accessible to heat, which retains it longer than iron.
This mineral, (which has not long been publicly mentioned) appears,
however, to be more difficult to fuse; the fire of the best furnaces
is not fierce enough to produce that effect, nor even to agglutinate
the small grains, which are all angular, hard, and similar in form to
the thick scale of iron, but of a yellowish colour; and although we
can fuse them without any addition, and reduce them into a mass by a
mirror, platina seems to require more heat than the ore and scales of
iron which we easily fuse in our forge furnaces. In other respects,
the density of platina being much greater than that of iron, the
two quantities of density and non-fusibility unite here to render
this matter the least accessible to the progress of heat. I presume,
therefore, that platina would have been at the head of my table if I
had put it to the experiment; but I was not able to procure a globe
of it of an inch diameter, it being only found in grains[C]; and that
which is in the mass is not pure, it being necessary, in order to fuse
it, to mix it with other matters, which alter its nature. The Comte de
Billarderie d'Angivilliers, who often attended my experiments, led me
to examine this rare metallic substance, not yet sufficiently known.
Chemists who have employed their time in platina, have looked upon it
as a new, perfect, proper, and particular metal, different from all the
rest: they have asserted, that its specific weight was nearly equal to
that of gold; but that it essentially differed in other respects from
gold, having neither ductility nor fusibility. I own I am of a quite
contrary opinion; because a matter which has neither ductility nor
fusibility, cannot rank in the number of metals, whose essential and
common properties are to be ductile and fusible. Neither, after a very
careful examination, did platina appear to me a new metal different
from every other, but rather an alloy of iron and gold formed by
Nature, in which the quantity of gold predominated over the iron; and I
founded this opinion on the following facts:
[C] I have been assured, however, by a person of the first
respectability, that platina is sometimes found in masses, and that
he himself saw a piece that weighed twenty pounds, pure as it was
extracted from the mine.
Of 8 ounces 85 grains of platina, furnished me by Comte d'Angivilliers,
which I presented to a strong loadstone, there remained only 1 ounce,
1 dram, and 98 grains, all the rest was taken away by the loadstone;
therefore, nearly six-sevenths of the whole was attracted by the
loadstone, which is so considerable a quantity, that it is impossible
to suppose that iron is not contained in the intimate substance of
platina, but that it is even there in a very great quantity. I am
convinced it contains much more, for if I had not been weary of these
experiments, which took me up several days, I should have attracted a
great part of the remainder of the 8 ounces by my loadstone, for to the
last it continued to draw some grains one by one, and sometimes two.
There is, therefore, much iron in platina, and it is not simply mixed
with it, as with a foreign matter, but intimately united and making
part of its substance; or, if this is denied, it must be supposed,
that there exists a second matter in Nature which like iron may be
attracted by the loadstone.
All the platina I have had an opportunity of examining, has appeared
to be mixed with two different matters, the one black, and very
attractable by the loadstone; the other in larger grains, of a pale
yellow, and much less magnetic than the first. Between these two
matters, which are the two extremes, are found all the intermediate
links, whether with respect to magnetism, colour, or size of the
grains. The most magnetic, which are at the same time the blackest and
smallest, reduce easily into powder by a very slight friction, and
leave on white paper the same marks as lead. Seven leaves of paper
which were successively made use of to expose the platina to the action
of the loadstone, were blackened over the whole extent occupied by it;
the last left less than the first, in proportion as the grains which
remained were less black and magnetic; the largest grains, which are
yellow, and least magnetic, instead of crumbling into powder like
the small black grains, are very hard, and resist all trituration;
nevertheless, they are susceptible of extension in an agate mortar,
under the reiterated strokes of a pestle of the same matter, and I
flattened and extended many grains to the double or treble extent of
their surface: this part of platina, therefore, has a certain degree
of malleability, and ductility, whereas the black part appears to be
neither malleable nor ductile. The intermediate grains participate of
the qualities of the two extremes: they are brittle and hard, they
break or extend under the strokes of the pestle, and afford a little
powder not so black as the first.
Having collected this black powder and the most magnetic grains that
the loadstone at first attracted, I discovered that the whole was
iron, but in a different state from common iron. The latter reduced
into powder and filings contracts moisture, and rusts very readily;
in proportion as the rust increases, it becomes less magnetic, and
absolutely loses this magnetical quality when entirely and intimately
rusted; whereas this iron powder, or ferruginous sand found in the
platina, is inaccessible to rust, how long soever it may be exposed
to the air and humidity; it is also more infusible and much less
dissoluble than common iron; but is, nevertheless, an iron which
appears to differ only from common iron by a greater purity. This
sand is, in fact, iron divested of all the combustible matter and all
terrene parts which are found in common iron, and even in steel. It
appears endowed and covered with a vitreous varnish which defends it
from all injury. What is very remarkable, this pure iron sand does not
exclusively belong to the platina ore; for I have found it, although
always in small quantities, in many parts where the iron ore has
been dug, and which consumed in my forges. As I submitted to several
trials all the ores I had, before I used them in my experiments, I was
surprised to find in some of them, which were in grains, particles
of iron, somewhat rounded and shining, like the filings of iron,
and perfectly resembling the ferruginous sand of the platina; they
were all as magnetic, all as little fusible, and all as difficult of
solution. Such was the result of the comparison I made on the sand of
platina, and of the sand found in both my iron ores, at the depth of
three feet, in earths where water easily penetrated. I was puzzled
to conceive whence these particles of iron could proceed, how they
had been defended against rust for the ages they were exposed to the
humidity of the earth, and how this very magnetical iron had been
produced in veins of mines, which had not the smallest degree of that
quality. I called experience to my aid, and became at length satisfied
upon these points. I was well convinced that none of our iron ores in
grain were tractable by the loadstone, and well persuaded that all iron
ores, which are magnetical, have acquired that property only by the
action of fire: that the mines of the north, which are so magnetical
as to be sought after by the compass, must owe their origin to fire,
and are formed by the means, or the intermedium of water; from which I
was induced to suppose that this ferruginous and magnetic sand, that
I found in a small quantity in my iron mines, must owe its origin to
fire, and having examined the place I was confirmed in this idea. This
magnetical sand is found in a wood, where, from time immemorial, they
have made, and still continue to make, coal furnaces. It is likewise
more than probable that there were formerly considerable fires here.
Coal and burnt wood produce iron dross, which includes the most fixed
parts of iron that vegetables contain; it is this fixed iron which
forms the sand here spoken of, when the dross is decomposed by the
action of the air, sun, and rain, for then these pure iron particles,
which are not subject to rust, nor to any other kind of alteration,
suffer themselves to be carried away by the water, and penetrate with
it some feet deep into the earth. What I here advance may be verified
by grinding the dross well burnt, and there will be found a small
quantity of this pure iron, which, having resisted the action of the
fire, equally resists that of the solvents, and does not rust at all.
Being satisfied on this head, and having sufficiently compared the
sand and dross taken from the iron ores with that of the platina,
so as to have no doubt of their identity, it was not long before I
was led to conclude, considering the specific gravity of platina,
that if this pure iron sand, (proceeding from the decomposition of
dross) instead of being in an iron mine, was found near to a gold
one, it might, by uniting with that metal, form an alloy which would
be absolutely of the same nature as platina. Gold and iron have a
great affinity; and it is well-known that most iron mines contain a
small quantity of gold; it is also known how to give to gold the tint,
colour, and even the brittleness of iron, by fusing them together.
This iron-coloured gold is used on different golden jewels to vary
the colours; and this gold mixed with iron is more or less grey, and
more or less tempered, according to the quantity of iron which enters
the mixture. I have seen it of a tint absolutely like the colour of
platina; and having enquired of a goldsmith the proportion of gold
and iron therein, he informed me, that in a piece of 24 carats, there
were no more than 18 gold, consequently a fourth part was iron, which
is nearly the proportion found in the natural platina, if we judge of
it by the specific weight; and this gold made with iron is harder and
specifically less weighty than pure gold. All these agreements and
common qualities with platina, have persuaded me, that this pretended
metal is, in fact, only an alloy of gold and iron, and not a particular
substance, a new and perfect metal different from every other, as
chemists have supposed.
It is well known that alloy makes all metals brittle, and that when
there is a penetration, that is, an augmentation in the specific
gravity, the alloy is so much the more tempered as the penetration is
the greater, and the mixture becomes the more intimate, as is perceived
in the alloy called _bell-metal_, although it be composed of two very
ductile metals. Now nothing is more tempered, nor heavier than platina,
which alone ought to make us conclude that it is only an alloy made by
Nature, a mixture of iron and gold, owing in part its specific gravity
to this last, and, perhaps, also, in a great part, to the penetration
of the two matters of which it is composed.
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.
"M. de Fourcy had lately told the world, that the dissolution of gold
was thrown down in a blue precipitate by the Prussian alkali, and
had placed this circumstance in a table of affinity; I was tempted
to repeat this experiment, and sprinkled, in consequence, the
phlogisticated alkaline liquor in the dissolution of gold, but the
colour of this dissolution did not change, which made me suspect that
the dissolution of gold made use of by M. de Fourcy might possibly not
have been so pure.
"At the same time the Comte de Buffon having given me a sufficient
quantity of platina to make further assays, I undertook to separate it
from all foreign bodies by a good front; and I have here subjoined the
processes and their results.