Notwithstanding the assiduity I used in my experiments, and the care
I took to render the relations exact, I own there are still some
imperfections in the foregoing table; but the defects are trivial,
and do not much influence the general results; for example, it will
easily be perceived, that the relation of zinc to lead being 10,000
to 6,051, that of zinc to tin should be less than 6,000, whereas it
is found 6,777 in the table. It is the same with respect of silver
to bismuth, which ought to be less than 6,308, and also with regard
of lead to clay, which ought to be more than 8,000, but in the table
is only 7,878. This difference proceeded from the leaden and bismuth
bullets not being always the same; they melted, as well as those of tin
and antimony, and, therefore, could not fail to produce variations,
the greatest of which are the three I have just remarked. It was not
possible for me to do better; the different bullets of lead, tin,
bismuth, and antimony, which I successively made use of, were made in
the same manner, but the matter of each might be somewhat different,
according to the quantity of the alloy in the lead and tin, for I had
pure tin only for the two first bullets; besides, there remains very
often a small cavity in the melted bullet, and these little causes are
sufficient to produce the little differences which may be remarked in
the table.
On the whole, to draw from these experiments all the profit that can be
expected, the matters which compose their object must be divided into
four classes, viz. 1. Metals. 2. Semi-metals and Metallic Minerals. 3.
Vitreous and Vitrescible Substances. And 4. Calcareous and Calcinable
substances. Afterwards the matters of each class must be compared
between themselves to discover the cause, or causes, or the order which
follows the progress of heat in each, and then with each other, in
order to deduce some general results.
First. The order of the six metals, according to their _density_, is
tin, iron, copper, silver, lead, and gold; whereas the order in which
they receive and lose their heat is tin, lead, silver, gold, copper,
and iron; so that in tin alone it retains its place.
The progress and duration of heat in metals does not then follow the
order of their density, except in tin, which being the least dense,
is also that which soonest loses its heat; but the order of the five
other metals demonstrates that it is in relation to their fusibility
that they all receive and loose heat; for iron is more difficult to
melt than copper, copper more than gold, gold more than silver, silver
more than lead, lead more than tin; and therefore we may conclude that
it is only by chance if the density and fusibility of tin be found
so united as to place it in the last rank. Nevertheless, it would be
advancing too much to pretend that we must attribute all to fusibility,
and nothing to density. Nature never deprives herself of one of her
properties in favour of another in an absolute manner; that is to say,
in a mode that the first has not any influence on the second. Thus,
density may be of some weight in the progress of heat; but we may
safely affirm, that in the six metals it has very little comparatively
with fusibility.
This fact was neither known to chemists nor naturalists; they did not
even imagine that gold which is more than twice as dense as iron,
nevertheless loses its heat near a third sooner. It is the same with
lead, silver, and copper, which are all more dense than iron, and
which, like gold, heat and cool more readily; for though the object of
this, second memoir was only refrigeration, yet the experiments of the
one that preceded it demonstrate, that there is ingress and egress of
heat in bodies, and that those which receive it most quickly also lose
it the soonest.
If we reflect on the real principles of density, and the cause of
fusibility, we shall perceive, that density depends absolutely on the
quantity of matter which Nature places in a given space; that the more
she can make it enter therein, the more density there will be, and
that gold, in this respect, is of all substances, that which contains
the most matter relatively to its volume. It is for this reason that
it has been hitherto thought, that more time is required to heat or
cool gold than other metals; and it is natural enough to suppose, that
containing double or treble the matter in the same volume, double or
treble time would be required to penetrate it with heat; nay this would
be true, if in every substance the constituent parts were of the same
figure and ranged the same. But in the most dense the molecules of
matter are, probably, of a figure sufficiently regular not to leave
very void places between them; in others which are not so dense, and
their figures more irregular, more vacuities are left, and in the
lightest, the molecules being few, and most likely of a very irregular
figure, a thousand times more void is found than plenitude; for it may
be demonstrated by other experiments, that the volume of even the most
dense substance contains more void space than full matter.
Now, the principal cause of fusibility is the facility which the
particles of heat find in separating these molecules of full matter
from each other; let the sum of the vacuities be greater or less, which
causes density or lightness, it is indifferent to the separation of
the molecules which constitute the plenitude; and the greater or less
fusibility depends entirely on the power of coherence which retains
the massive parts united, and opposes itself more or less to their
separation. The dilatation of the total volume is the first degree of
the action of heat; and in different metals it is made in the same
order as the fusion of the mass, which is performed by a greater degree
of heat or fire. Tin, which melts the most readily, is also that which
dilates the quickest; and iron, which is the most difficult of all to
melt, is likewise that whose dilatation is the slowest.
After these general positions, which appear clear, precise, and founded
on experiments that nothing can contradict, it might be imagined that
ductility would follow the order of fusibility, because the greater
or less ductility seems to depend on the greater or less adhesion of
the parts in each metal; nevertheless, ductility seems to have as much
connection with the order of density, as with that of their fusibility.
I would even affirm that it is in a ratio composed of the two others,
but that would be only by estimation, and a presumption which is,
perhaps not founded; for it is not so easy to exactly determine the
different degrees of fusibility, as those of density; and as ductility
participates of both, and varies according to circumstances, we have
not as yet acquired the necessary knowledge to pronounce affirmatively
on this subject, though it is most certainly of sufficient importance
to merit particular researches. The same metal when cold gives very
different results to what it does when hot, although treated in
the same manner. Malleability is the first mark of ductility; but
that gives only an imperfect idea of the point to which ductility
may extend; nor can simple lead, the most malleable metal, be drawn
into such fine threads as gold, or even as iron, which is the least
malleable. Besides we must assist the ductility of metals with the
addition of fire, without which they become brittle: even iron,
although the most robust, is brittle like the rest. Thus the ductility
of one metal, and the extent of continuity which it can support, depend
not only on its density and fusibility, but also on the manner and
space in which it is treated, and of the addition of heat or fire which
is properly given to it.
II. By comparing those substances which we term _semi-metals_ and
_metallic minerals_, which want ductility, we shall perceive, that
the order of their density is emery, zinc, antimony and bismuth, and
that in which they receive and lose heat, is antimony, bismuth, zinc,
and emery; and which does not in any measure follow the order of
their density, but rather that of their fusibility. Emery, which is a
ferruginous mineral, although as dense again as bismuth, retains heat
longer. Zinc, which is lighter than antimony or bismuth, retains heat
longer than either. Antimony and bismuth, receive and keep it nearly
alike. There are, therefore, semi-metals, and metallic minerals, which,
like metals, receive and lose heat nearly in the same relation as their
fusibility, and partake very little of their density.
But by joining the six metals, and the four semi-metals, or metallic
minerals, which I have tried, we shall find the order of the densities
of these ten mineral substances to be emery, zinc, antimony, tin,
iron, copper, bismuth, silver, lead and gold. And that the order in
which these substances heat and cool, is antimony, bismuth, tin,
lead, silver, zinc, gold, copper, emery and iron, in which there are
two things that do not appear to perfectly agree with the order of
fusibility.
First, Antimony, which, according to Newton, should heat and cool
slower than lead, since by his experiments it requires ten degrees of
the same heat to fuse, of which eight are sufficient for lead; whereas
by my experiments antimony is found to heat and cool quicker than
lead. But it should be observed that Newton made use of the regulus of
antimony, and that I employed only melted antimony in experiments. Now
this regulus of antimony, or native antimony, is much more difficult
to fuse than antimony which has already undergone a first fusion,
therefore that does not make an exception to the rule. On the whole, I
do not know what relation native antimony, or regulus of antimony, may
have with the other matters I have heated and cooled; but I presume,
from the experiments of Newton, that it heats and cools slower than
lead.
Secondly, it is pretended, that zinc fuses more easily than silver,
consequently it should be found before silver in the order indicated
by experiments, if this order were in all cases relative to that of
fusibility; and I own that this semi-metal seems, at the first glance,
to make an exception to the law which is followed by all the others;
but it must be observed, that the difference given by my experiments
between zinc and silver is very trifling. The small globe of silver
which I made use of was of the purest silver, without the least mixture
of copper; but I had my doubts whether that of zinc were entirely
free from copper, or some other metal less fusible; and therefore,
after all my experiments, I returned the globe of zinc to M. Rouelle,
a celebrated professor of chemistry, requesting him carefully to
examine it, which having done, after several trials, he found a pretty
considerable quantity of iron, or saffron of steel in it.
I have, therefore, had the satisfaction of seeing that not only my own
supposition was well founded, but also that my experiments have been
made with sufficient precision to evince a mixture. Thus zinc exactly
follows the order of fusibility, like the other metals and semi-metals,
in the progress of heat, and does not make any exception to the rule.
It cannot therefore, in general, be said that the progress of heat in
metals, semi-metals, and metallic minerals, is in the same ratio, or
even nearly to that of their fusibility.
III. The Vitrescible and Vitreous Matters, which I tried, being ranged
according to their density, are, pumice-stone, porcelain, oker, clay,
glass, rock-chrystal, and gres, for I must observe, that although
chrystal is not set down in the table of the weight of each matter but
for six drachms 22 grains, it must be supposed one drachm heavier,
because it was sensibly too small; and it was for this reason that I
excluded it from the general table of relations; nevertheless, as the
general result agrees with the rest, I can present the following as the
order in which these different substances are cooled:
Pumice-stone, oker, porcelain, clay, glass, crystal and gres, is
according to that of their density, for the oker is here before the
porcelain only because, being a fusible matter, it diminished by the
friction it underwent in the experiments, and, besides, their density
differs so little that they may be looked upon as equal.
Thus the law of the progress of heat in vitrescible and vitreous
matters is relative to the order of their density, and has little or no
relation with their fusibility but by the heat required to fuse those
substances being in an almost equal degree, and the particular degree
of their different fusibility being so near each other that an order
of distinct terms cannot be made; thus their almost equal fusibility
making only one term, which is the extreme of this order, we must not
be astonished that the progress of heat here follows the order of
density, and that these different substances, which are all equally
difficult to fuse, heat and cool more or less quick in proportion to
the matter they contain.
It may be objected to me that glass fuses more easily than clay,
porcelain, oker, and pumice-stone, which, nevertheless, heat and cool
in less time than glass; but the objection will fail when we reflect,
that to fuse glass it is requisite to have a very fierce fire, the
heat of which is so remote from the degrees which glass receives in
our experiments on refrigeration, that it cannot have any influence
on them. Besides, by powdering clay, porcelain, and pumice-stone, and
by giving them their analogous fusers, as we give to sand to convert
it into glass, it is more than probable that we should fuse all the
matters in the same degree of fire, and that, consequently we must look
upon it as equal, or almost equal, with their resistance to fusion;
and it is for this reason that the law of the progress of heat in these
matters is found proportionable to the order of their density.
IV. Calcareous matters, ranged according to the order of their density,
are, chalk, soft stone, hard stone, common marble, and white marble,
which is the same as that of their density. The fusibility is not
here of any weight, because it requires at first a very great degree
of fire to calcine them; and although the calcination divides the
parts, we must look upon the effect only as a first degree and not
as a complete fusion. The whole power of the best burning mirrors is
scarcely sufficient to perform it. I have melted and reduced into a
kind of glass some of these calcareous matters; and I am convinced that
these matters may, like all the rest, be reduced ulteriorly into glass,
without employing for this purpose any fusing matter, and only by the
force of a fire superior to that of our furnaces; consequently the
common term of their fusibility is still more remote, and more extreme,
than that of vitreous matters, and it is for this reason that they also
follow more exactly the order of density in the progress of heat.
White gypsum, improperly called alabaster, is a matter which calcines
like all other plasters by a more moderate heat than that which is
necessary for the calcination of calcareous matters, and it follows the
order of density in the progress of heat which it receives or loses,
for although much more dense than chalk, and a little more so than
white calcareous stone, it heats and cools more readily than either of
those matters. This demonstrates that the more or less easy calcination
and fusion produces the same effects relatively to the progress of
heat. Gypsous matters do not require so much fire to calcine as
calcareous, and it is for this reason that, although more dense, they
heat and cool much quicker.
Thus it may be concluded, that, in general, the _progress of heat in
all Mineral Substances is always nearly in a ratio of their greater or
less facility to calcine, or melt_: but that when their calcination, or
their fusion, are _equally difficult_, and _that they require a degree
of extreme heat_, then the _progress of heat is made according to the
order of their density_.
I have deposited in the Royal Cabinet the globes of gold, silver, and
of all the other metallic and mineral substances which served for the
preceding experiments, that if the truth of their results, and the
general consequences which I have deduced, be doubted, there may be an
opportunity of rendering them more authentic.