Title: Discovery of Oxygen, Part 2
Author: Scheele, Carl Wilhelm, 1742-1786
Language: English
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DISCOVERY OF OXYGEN

PART 2

EXPERIMENTS BY

CARL WILHELM SCHEELE

(1777)

Re issue Edition:

Published for THE ALEMBIC CLUB

BY

E. & S. LIVINGSTONE LTD.

16 & 17 TEVIOT PLACE

EDINBURGH

1964

[Illustration]



PREFACE


The portions of Scheele's "Chemical Treatise on Air and Fire" here
reproduced in English are intended to form a companion volume to No. 7
of the Club Reprints, which contains Priestley's account of his
discovery of oxygen. Not only have the claims of Scheele to the
independent discovery of this gas never been disputed, but the valuable
volume of "Letters and Memoranda" of Scheele, edited by Nordenskjöld,
which was published in 1892, places it beyond doubt that Scheele had
obtained oxygen by more than one method at least as early as Priestley's
first isolation of the gas, although his printed account of the
discovery only appeared about two years after Priestley's. The evidence
of this has been found in Scheele's laboratory notes, which are still
preserved in the Royal Academy of Science in Stockholm.

In his "Chemical Treatise" Scheele endeavours, at considerable length,
to prove by experiments his views as to the compound character of heat
and of light. These portions of the work have been entirely omitted from
what is reproduced here. All the places where omissions have been made
are indicated.

Every care has been taken in the endeavour to make the translation a
faithful reproduction of the meaning of the original, whilst literal
accuracy has been aimed at rather than literary elegance.

L. D.



CHEMICAL TREATISE ON AIR AND FIRE.[A]


+1.+ It is the object and chief business of chemistry to skilfully
separate substances into their constituents, to discover their
properties, and to compound them in different ways.

How difficult it is, however, to carry out such operations with the
greatest accuracy, can only be unknown to one who either has never
undertaken this occupation, or at least has not done so with sufficient
attention.


+2.+ Hitherto chemical investigators are not agreed as to how many
elements or fundamental materials compose all substances. In fact this
is one of the most difficult problems; some indeed hold that there
remains no further hope of searching out the elements of substances.
Poor comfort for those who feel their greatest pleasure in the
investigation of natural things! Far is he mistaken, who endeavours to
confine chemistry, this noble science, within such narrow bounds! Others
believe that earth and phlogiston are the things from which all material
nature has derived its origin. The majority seem completely attached to
the peripatetic elements.


+3.+ I must admit that I have bestowed no little trouble upon this
matter in order to obtain a clear conception of it. One may reasonably
be amazed at the numerous ideas and conjectures which authors have
recorded on the subject, especially when they give a decision respecting
the fiery phenomenon; and this very matter was of the greatest
importance to me. I perceived the necessity of a knowledge of fire,
because without this it is not possible to make any experiment; and
without fire and heat it is not possible to make use of the action of
any solvent. I began accordingly to put aside all explanations of fire;
I undertook a multitude of experiments in order to fathom this beautiful
phenomenon as fully as possible. I soon found, however, that one could
not form any true judgment regarding the phenomena which fire presents,
without a knowledge of the air. I saw, after carrying out a series of
experiments, that air really enters into the mixture of fire, and with
it forms a constituent of flame and of sparks. I learned accordingly
that a treatise like this, on fire, could not be drawn up with proper
completeness without taking the air also into consideration.

[Footnote A: Carl Wilhelm Scheele's Chemische Abhandlung von der Luft
und dem Feuer. Upsala and Leipzig, 1777.]


+4.+ Air is that fluid invisible substance which we continually breathe,
which surrounds the whole surface of the earth, is very elastic, and
possesses weight. It is always filled with an astonishing quantity of
all kinds of exhalations, which are so finely subdivided in it that they
are scarcely visible even in the sun's rays. Water vapours always have
the preponderance amongst these foreign particles. The air, however, is
also mixed with another elastic substance resembling air, which differs
from it in numerous properties, and is, with good reason, called aerial
acid by Professor Bergman. It owes its presence to organised bodies,
destroyed by putrefaction or combustion.


+5.+ Nothing has given philosophers more trouble for some years than
just this delicate acid or so called fixed air. Indeed it is not
surprising that the conclusions which one draws from the properties of
this elastic acid are not favourable to all who are prejudiced by
previously conceived opinions. These defenders of the Paracelsian
doctrine believe that the air is in itself unalterable; and, with Hales,
that it really unites with substances thereby losing its elasticity; but
that it regains its original nature as soon as it is driven out of these
by fire or fermentation. But since they see that the air so produced is
endowed with properties quite different from common air, they conclude,
without experimental proofs, that this air has united with foreign
materials, and that it must be purified from these admixed foreign
particles by agitation and filtration with various liquids. I believe
that there would be no hesitation in accepting this opinion, if one
could only demonstrate clearly by experiments that a given quantity of
air is capable of being completely converted into fixed or other kind of
air by the admixture of foreign materials; but since this has not been
done, I hope I do not err if I assume as many kinds of air as experiment
reveals to me. For when I have collected an elastic fluid, and observe
concerning it that its expansive power is increased by heat and
diminished by cold, while it still uniformly retains its elastic
fluidity, but also discover in it properties and behaviour different
from those of common air, then I consider myself justified in believing
that this is a peculiar kind of air. I say that air thus collected must
retain its elasticity even in the greatest cold, because otherwise an
innumerable multitude of varieties of air would have to be assumed,
since it is very probable that all substances can be converted by
excessive heat into a vapour resembling air.


+6.+ Substances which are subjected to putrefaction or to destruction by
means of fire diminish, and at the same time consume, a part of the air;
sometimes it happens that they perceptibly increase the bulk of the air,
and sometimes finally that they neither increase nor diminish a given
quantity of air; phenomena which are certainly remarkable. Conjectures
can here determine nothing with certainty, at least they can only bring
small satisfaction to a chemical philosopher, who must have his proofs
in his hands. Who does not see the necessity of making experiments in
this case, in order to obtain light concerning this secret of nature?


+7. General properties of ordinary air.+

(1.) Fire must burn for a certain time in a given quantity of air. (2.)
If, so far as can be seen, this fire does not produce during combustion
any fluid resembling air, then, after the fire has gone out of itself,
the quantity of air must be diminished between a third and a fourth
part. (3.) It must not unite with common water. (4.) All kinds of
animals must live for a certain time in a confined quantity of air. (5.)
Seeds, as for example peas, in a given quantity of similarly confined
air, must strike roots and attain a certain height with the aid of some
water and of a moderate heat.

Consequently, when I have a fluid resembling air in its external
appearance, and find that it has not the properties mentioned, even when
only one of them is wanting, I feel convinced that it is not ordinary
air.


+8. Air must be composed of elastic fluids of two kinds.+

+First Experiment.+--I dissolved one ounce of alkaline liver of sulphur
in eight ounces of water; I poured 4 ounces of this solution into an
empty bottle capable of holding 24 ounces of water, and closed it most
securely with a cork; I then inverted the bottle and placed the neck in
a small vessel with water; in this position I allowed it to stand for 14
days. During this time the solution had lost a part of its red colour
and had also deposited some sulphur: afterwards I took the bottle and
held it in the same position in a larger vessel with water, so that the
mouth was under and the bottom above the water-level, and withdrew the
cork under the water; immediately water rose with violence into the
bottle. I closed the bottle again, removed it from the water, and
weighed the fluid which it contained. There were 10 ounces. After
subtracting from this the 4 ounces of solution of sulphur there remain 6
ounces, consequently it is apparent from this experiment that of 20
parts of air 6 parts have been lost in 14 days.


+9. Second Experiment.+--(_a._) I repeated the preceding experiment with
the same quantity of liver of sulphur, but with this difference that I
only allowed the bottle to stand a week, tightly closed. I then found
that of 20 parts of air only 4 had been lost. (_b._) On another occasion
I allowed the very same bottle to stand 4 months; the solution still
possessed a somewhat dark yellow colour. But no more air had been lost
than in the first experiment, that is to say 6 parts.


+10. Third Experiment.+--I mixed 2 ounces of caustic ley, which was
prepared from alkali of tartar and unslaked lime and did not precipitate
lime water, with half an ounce of the preceding solution of sulphur
which likewise did not precipitate lime water. This mixture had a yellow
colour. I poured it into the same bottle, and after this had stood 14
days, well closed, I found the mixture entirely without colour and also
without precipitate. I was enabled to conclude that the air in this
bottle had likewise diminished, from the fact that air rushed into the
bottle with a hissing sound after I had made a small hole in the cork.


+11. Fourth Experiment.+--(_a._) I took 4 ounces of a solution of
sulphur in lime water; I poured this solution into a bottle and closed
it tightly. After 14 days the yellow colour had disappeared, and of 20
parts of air 4 parts had been lost. The solution contained no sulphur,
but had allowed a precipitate to fall which was chiefly gypsum. (_b._)
Volatile liver of sulphur likewise diminishes the bulk of air. (_c._)
Sulphur, however, and volatile spirit of sulphur, undergo no alteration
in it.


+12. Fifth Experiment.+--I hung up over burning sulphur, linen rags
which were dipped in a solution of alkali of tartar. After the alkali
was saturated with the volatile acid, I placed the rags in a flask, and
closed the mouth most carefully with a wet bladder. After 3 weeks had
elapsed I found the bladder strongly pressed down; I inverted the flask,
held its mouth in water, and made a hole in the bladder; thereupon water
rose with violence into the flask and filled the fourth part.


+13. Sixth Experiment.+--I collected in a bladder the nitrous air which
arises on the dissolution of the metals in nitrous acid, and after I had
tied the bladder tightly I laid it in a flask and secured the mouth very
carefully with a wet bladder. The nitrous air gradually lost its
elasticity, the bladder collapsed, and became yellow as if corroded by
_aqua fortis_. After 14 days I made a hole in the bladder tied over the
flask, having previously held it, inverted, under water; the water rose
rapidly into the flask, and it remained only 2/3 empty.


+14. Seventh Experiment.+--(_a._) I immersed the mouth of a flask in a
vessel with oil of turpentine. The oil rose in the flask a few lines
every day. After the lapse of 14 days the fourth part of the flask was
filled with it; I allowed it to stand for 3 weeks longer, but the oil
did not rise higher. All those oils which dry in the air, and become
converted into resinous substances, possess this property. Oil of
turpentine, however, and linseed oil rise up sooner if the flask is
previously rinsed out with a concentrated sharp ley. (_b._) I poured 2
ounces of colourless and transparent animal oil of Dippel into a bottle
and closed it very lightly; after the expiry of two months the oil was
thick and black. I then held the bottle, inverted, under water and drew
out the cork; the bottle immediately became 1/4 filed with water.


+15. Eighth Experiment.+--(_a._) I dissolved 2 ounces of vitriol of iron
in 32 ounces of water, and precipitated this solution with a caustic
ley. After the precipitate had settled, I poured away the clear fluid
and put the dark green precipitate of iron so obtained, together with
the remaining water, into the before-mentioned bottle (§ 8), and closed
it tightly. After 14 days (during which time I shook the bottle
frequently), this green calx of iron had acquired the colour of crocus
of iron, and of 40 parts of air 12 had been lost. (_b._) When iron
filings are moistened with some water and preserved for a few weeks in a
well closed bottle, a portion of the air is likewise lost. (_c._) The
solution of iron in vinegar has the same effect upon air. In this case
the vinegar permits the dissolved iron to fall out in the form of a
yellow crocus, and becomes completely deprived of this metal. (_d._) The
solution of copper prepared in closed vessels with spirit of salt
likewise diminishes air. In none of the foregoing kinds of air can
either a candle burn or the smallest spark glow.


+16.+ It is seen from these experiments that phlogiston, the simple
inflammable principle, is present in each of them. It is known that the
air strongly attracts to itself the inflammable part of substances and
deprives them of it: not only this may be seen from the experiments
cited, but it is at the same time evident that on the transference of
the inflammable substance to the air a considerable part of the air is
lost. But that the inflammable substance[B] alone is the cause of this
action, is plain from this, that, according to the 10th paragraph, not
the least trace of sulphur remains over, since, according to my
experiments this colourless ley contains only some vitriolated tartar.
The 11th paragraph likewise shews this. But since sulphur alone, and
also the volatile spirit of sulphur, have no effect upon the air (§ 11.
_c._), it is clear that the decomposition of liver of sulphur takes place
according to the laws of double affinity,--that is to say, that the
alkalies and lime attract the vitriolic acid, and the air attracts the
phlogiston.

[Footnote B: "Das Brennbare."]

It may also be seen from the above experiments, that a given quantity of
air can only unite with, and at the same time saturate, a certain
quantity of the inflammable substance: this is evident from the 9th
paragraph, _letter b_. But whether the phlogiston which was lost by the
substances was still present in the air left behind in the bottle, or
whether the air which was lost had united and fixed itself with the
materials such as liver of sulphur, oils, &c., are questions of
importance.

From the first view, it would necessarily follow that the inflammable
substance possessed the property of depriving the air of part of its
elasticity, and that in consequence of this it becomes more closely
compressed by the external air. In order now to help myself out of these
uncertainties, I formed the opinion that any such air must be
specifically heavier than ordinary air, both on account of its
containing phlogiston and also of its greater condensation. But how
perplexed was I when I saw that a very thin flask which was filled with
this air, and most accurately weighed, not only did not counterpoise an
equal quantity of ordinary air, but was even somewhat lighter. I then
thought that the latter view might be admissible; but in that case it
would necessarily follow also that the lost air could be separated again
from the materials employed. None of the experiments cited seemed to me
capable of shewing this more clearly than that according to the 10th
paragraph, because this residuum, as already mentioned, consists of
vitriolated tartar and alkali. In order therefore to see whether the
lost air had been converted into fixed air, I tried whether the latter
shewed itself when some of the caustic ley was poured into lime water;
but in vain--no precipitation took place. Indeed, I tried in several
ways to obtain the lost air from this alkaline mixture, but as the
results were similar to the foregoing, in order to avoid prolixity I
shall not cite these experiments. Thus much I see from the experiments
mentioned, that the air consists of two fluids, differing from each
other, the one of which does not manifest in the least the property of
attracting phlogiston, while the other, which composes between the third
and the fourth part of the whole mass of the air, is peculiarly disposed
to such attraction. But where this latter kind of air has gone to after
it has united with the inflammable substance, is a question which must
be decided by further experiments, and not by conjectures.

We shall now see how the air behaves towards inflammable substances when
they get into fiery motion. We shall first consider that kind of fire
which does not give out during the combustion any fluid resembling air.


+17. First Experiment.+--I placed 9 grains of phosphorus from urine in a
thin flask, which was capable of holding 30 ounces of water, and closed
its mouth very tightly. I then heated, with a burning candle, the part
of the flask where the phosphorus lay; the phosphorus began to melt, and
immediately afterwards took fire; the flask became filled with a white
cloud, which attached itself to the sides like white flowers; this was
the dry acid of phosphorus. After the flask had become cold again, I
held it, inverted, under water and opened it; scarcely had this been
done when the external air pressed water into the flask; this water
amounted to 9 ounces.


+18. Second Experiment.+--When I placed pieces of phosphorus in the same
flask and allowed it to stand, closed, for 6 weeks, or until it no
longer glowed, I found that 1/3 of the air had been lost.


+19. Third Experiment.+--I placed 3 teaspoonfuls of iron filings in a
bottle capable of holding 2 ounces of water; to this I added an ounce of
water, and gradually mixed with them half an ounce of oil of vitriol. A
violent heating and fermentation took place. When the froth had somewhat
subsided, I fixed into the bottle an accurately fitting cork, through
which I had previously fixed a glass tube A (Fig. 1). I placed this
bottle in a vessel filled with hot water, B B (cold water would greatly
retard the solution). I then approached a burning candle to the orifice
of the tube, whereupon the inflammable air took fire and burned with a
small yellowish-green flame. As soon as this had taken place, I took a
small flask C, which was capable of holding 20 ounces of water, and held
it so deep in the water that the little flame stood in the middle of the
flask. The water at once began to rise gradually into the flask, and
when the level had reached the point D the flame went out. Immediately
afterwards the water began to sink again, and was entirely driven out of
the flask. The space in the flask up to D contained 4 ounces, therefore
the fifth part of the air had been lost. I poured a few ounces of lime
water into the flask in order to see whether any aerial acid had also
been produced during the combustion, but I did not find any. I made the
same experiment with zinc filings, and it proceeded in every way
similarly to that just mentioned. I shall demonstrate the constituents
of this inflammable air further on; for, although it seems to follow
from these experiments that it is only phlogiston, still other
experiments are contrary to this.

We shall now see the behaviour of air towards that kind of fire which
gives off, during the combustion, a fluid resembling air.

[Illustration: _Fig. 1._]

[Illustration: _Fig. 2._]

[Illustration: _Fig. 3._]

[Illustration: _Fig. 4._]

[Illustration: _Fig. 5._]


+20. Fourth Experiment.+--It is well known that the flame of a candle
absorbs air; but as it is very difficult, and, indeed, scarcely
possible, to light a candle in a closed flask, the following experiment
was made in the first place:--I set a burning candle in a dish full
water; I then placed an inverted flask over this candle; at once there
arose from the water large air bubbles, which were caused by the
expansion, by heat, of the air in the flask. When the flame became
somewhat smaller, the water began to rise in the flask; after it had
gone out and the flask had become cold, I found the fourth part filled
with water. This experiment was very undecisive to me, because I was not
assured whether this fourth part of the air had not been driven out by
the heat of the flame; since necessarily in that case the external air
resting upon the water seeks equilibrium again after the flask has
become cold, and presses the same measure of water into the flask as of
air had been previously driven out by the heat. Accordingly, I made the
following experiment:


+21. Fifth Experiment.+--(_a._) I pressed upon the bottom of the dish A
(Fig. 2) a tough mass, of the thickness of two fingers, made of wax,
resin, and turpentine metal together; in the middle I fastened a thick
iron wire which reached to the middle of the flask B; upon the point of
this wire C, I stuck a small wax candle, whose wick I had twisted
together out of three slender threads. I then lighted the candle, and at
the same time placed over it the inverted flask B, which I then pressed
very deep into the mass. As soon as this was done, I filled the dish
with water. After the flame was extinguished and everything had become
quite cold, I opened the flask in the same position under the water,
when 2 ounces of water entered; the flask held 160 ounces of water.
Accordingly, there is wanting here so much air as occupies the space of
2 ounces of water. Has this air been absorbed by the inflammable
substance, or has the heat of the small flame driven it out even before
I could press the flask into the tough mass? The latter seems to have
taken place in this case, as I conclude from the following:--I took a
small flask capable of holding 20 ounces of water; in this I caused a
candle to burn as in the preceding; after everything had become cold, I
opened this flask likewise under water, whereupon similarly nearly 2
ounces entered. Had the former 2 ounces measure of air been absorbed,
then there should have been only 2 drachms measure absorbed in this
experiment.

(_b._) I repeated the preceding experiment with the large flask in
exactly the same way, except that I employed spirit of wine in place of
the candle. I fastened three iron wires, which were of equal length and
reached up to the middle of the flask, into the tough mass which was
firmly pressed on to the bottom of the dish. Upon these wires I laid a
four-cornered plate of metal, and upon this I placed a small vessel into
which spirit of wine was poured. I set fire to this and placed the flask
over it. After cooling, I observed that 3 ounces measure of air had been
driven out by the heat of the flame.

(_c._) Upon the same stand I placed a few small glowing coals, and
allowed then go out in the same way under the flask. I found after
cooling that the heat of the coals had driven out three and a half
ounces measure of air.

The experiments seem to prove that the transference of phlogiston to the
air does not always diminish its bulk, which, however, the experiments
mentioned in §§ 8.16 shew distinctly. But the following will shew that
that portion of the air which unites with the inflammable substance, and
is at the same time absorbed by it, is replaced by the newly formed
aerial acid.


+22. Sixth Experiment.+--After the fire had gone out and everything had
become cold in the experiments mentioned above (§ 21. _a._ _b._ _c._), I
poured into each flask 6 ounces of milk of lime (lime water which has in
it more unslaked lime than the water can dissolve); I then placed my
hand firmly on the mouth of the flask and swung it several times up and
down; then I held the flask inverted under water and drew my hand a
little to one side, so that a small orifice might be made. Water
immediately rose into the flask. Then I shut the mouth again very
tightly with my hand under water, and afterwards shook it several times
up and down. I opened it again under water; this operation I repeated
twice more until no more water would rise into the flask, or until no
more aerial acid was present in it. I then perceived that in each
experiment between 7 and 8 ounces of water rose into the flasks,
consequently the nineteenth part of the air has been lost. This was
indeed something, but since in the combustion of phosphorus (§ 17)
nearly the third part of the air was lost, there must be another reason
besides, why as much is not absorbed in this case also. It is known that
one part of aerial acid mixed with 10 parts of ordinary air extinguishes
fire; and there are here in addition, expanded by the heat of the flame
and surrounding the latter, the watery vapours produced by the
destruction of these oily substances. It is these two elastic fluids,
separating themselves from such a flame, which present no small
hindrance to the fire which would otherwise certainly burn much longer,
especially since there is here no current of air by means of which they
can be driven away from the flame. When the aerial acid is separated
from this air by milk of lime, then a candle can burn in it again,
although only for a very short time.


+23. Seventh Experiment.+--I placed upon the stand (§ 21. _b._) a small
crucible which was filled with sulphur; I set fire to it and placed the
flask over it. After the sulphur was extinguished and everything had
become cold, I found that out of 160 parts of air, 2 parts were driven
out of the flask by the heat of the flame. I next poured 6 ounces of
clear lime water into the flask and dealt with it by shaking, as already
explained, and observed that the sixth part of all the air had been lost
in consequence of the combustion. The lime water was not in the least
precipitated in this case, an indication that sulphur gives out no
aerial acid during its combustion, but another substance somewhat
resembling air; this is the volatile acid of sulphur, which occupies
again the empty space produced by the union of the inflammable substance
with air. It is not, as may be seen, a trifling circumstance that
phlogiston, whether it separates itself from substances and enters into
union with air, with or without a fiery motion, still in every case
diminishes the air so considerably in its external bulk.


+24. Experiments which prove that ordinary air, consisting of two kinds
of elastic fluids, can be compounded again after these have been
separated from each other by means of phlogiston.+

I have already stated in § 16 that I was not able to find again the lost
air. One might indeed object, that the lost air still remains in the
residual air which can no more unite with phlogiston; for, since I have
found that it is lighter than ordinary air, it might be believed that
the phlogiston united with this air makes it lighter, as appears to be
known already from other experiments. But since phlogiston is a
substance, which always presupposes some weight, I much doubt whether
such hypothesis has any foundation....


+25.+ How often must not chemists have distilled the fuming acid of
nitre from oil of vitriol and nitre, when it is impossible that they
should not have observed how this acid went over red in the beginning,
white and colourless in the middle of the distillation, but at the end
red again; and indeed so dark-red that one could not see through the
receiver? It is to be noticed here that if the heat is permitted to
increase too much at the end of the distillation, the whole mixture
enters into such frothing that everything goes over into the receiver;
and, what is of the greatest importance, a kind of air goes over during
this frothing which deserves no small attention. If one takes for such
distillation a very black oil of vitriol, not only does the acid go over
at the beginning of a far darker red than when one takes a white oil of
vitriol, but further, when one introduces a burning candle into the
receiver after about an ounce has gone over, this goes out immediately.
On the other hand, when one places a burning candle in the receiver
filled with blood-red vapours, towards the end of the distillation when,
as has been said, the mixture froths strongly, not only will it continue
to burn, but this will take place with a much brighter light than in
ordinary air. The same thing occurs when one attaches, at the close of
the distillation, a receiver which is filled with an air in which fire
will not burn, for, when this has been attached for half an hour, a
candle will likewise continue to burn in the air.

In this case there now arises in the first place the question: Are the
vapours of the acid of nitre naturally red? I beg leave to raise this
question here because I believe there are people who advance the redness
of this acid as a distinguishing characteristic. The colours of the acid
of nitre are accidental. When a few ounces of fuming acid of nitre are
distilled by a very gentle heat, the yellow separates itself from it and
goes into the receiver, and the residuum in the retort becomes white
and colourless like water. This acid has all the chief properties of
acid of nitre, except that the yellow colour is wanting. This I call the
pure acid of nitre; as soon, however, as it comes into contact with an
inflammable substance, it becomes more or less red. This red acid is
more volatile than the pure, hence heat alone can separate them from one
another; and, for exactly the same reason, the volatile spirit must go
over first in the distillation of Glauber's spirit of nitre. When this
has gone over, the colourless acid follows; but why does the acid make
its appearance again so blood-red at the end of the distillation? Why
has not this redness already been driven over at the beginning? Where
does it now obtain its phlogiston? This is the difficulty.


+26.+ I intimated in the preceding paragraph that the candle went out in
the receiver at the beginning of the distillation. The reason is to be
found in the experiment which I have cited in § 13. In this case the
acid of nitre, passing over in vapours, takes to itself the inflammable
substance, whose presence is indicated by the black colour of the oil of
vitriol; as soon as this has taken place it meets with the air, which
again robs the now phlogisticated acid of its inflammable substance; by
this means a part of the air contained in the receiver becomes lost,
hence the fire introduced into it must go out (§ 15).


+27.+ The acid of nitre can attract phlogiston in varying quantity, when
it likewise receives other properties with each proportion. (_a._) When
it becomes, as it were, saturated with it, a true fire arises, and it is
then completely destroyed. (_b._) When the inflammable principle is
present in smaller quantity, this acid is converted into a kind of air
which will not unite either with the alkalies or with the absorbent
earths, and with water only in very small quantity. When this acid of
nitre, resembling air, meets with the air, the latter takes the
inflammable substance from it again, it loses its elasticity (§ 13), the
vapours acquire redness, and the air undergoes at the same time this no
less remarkable than natural alteration, that it is not only diminished,
but also becomes warm. (_c._) When the acid of nitre receives still
somewhat less phlogiston, it is likewise converted into a kind of air,
which, like the air, is also invisible, but unites with the alkalies and
earths, and along with them can bring forth real intermediate salts.
This phlogisticated acid is, however, so loosely united with these
absorbing substances, that even the simple mixture with the vegetable
acids can drive it out. It is present in this condition in nitre which
has been made red hot, and also in _Nitrum Antimoniatum_. When this acid
of nitre meets the air it also loses its elasticity and is converted
into red vapours. When it is mixed in a certain quantity with water,
this acquires a blue, green, or yellow colour. (_d._) When the pure acid
of nitre receives but very little of the inflammable substance, the
vapours only acquire a red colour, and are wanting in expansive power;
it is, however, more volatile than the pure acid. This acid holds this
small quantity of phlogiston so firmly that even the air, which so
strongly attracts the inflammable substance, is not able to separate
this from it.

       *       *       *       *       *

+29.+ I took a glass retort which was capable of holding 8 ounces of
water, and distilled fuming acid of nitre according to the usual method.
In the beginning the acid went over red, then it became colourless, and
finally all became red again; as soon as I perceived the latter, I took
away the receiver and tied on a bladder, emptied of air, into which I
poured some thick milk of lime (§ 22) in order to prevent the corrosion
of the bladder. I then proceeded with the distillation. The bladder
began to expand gradually. After this I permitted everything to cool,
and tied up the bladder. Lastly I removed it from the neck of the
retort. I filled a bottle, which contained 10 ounces of water, with this
gas (§ 30, _e._), I then placed a small lighted candle in it; scarcely
had this been done when the candle began to burn with a large flame,
whereby it gave out such a bright light that it was sufficient to dazzle
the eyes. I mixed one part of this air with three parts of that kind of
air in which fire would not burn; I had here an air which was like the
ordinary air in every respect. Since this air is necessarily required
for the origination of fire, and makes up about the third part of our
common air, I shall call it after this, for the sake of shortness,
Fire-air; but the other air which is not in the least serviceable for
the fiery phenomenon, and makes up about two-thirds of our air, I shall
designate after this with the name already known, of Vitiated Air.


+30.+ Anyone might ask me in what way I bring air from one vessel into
another. I find it necessary therefore to describe this in the first
place. My arrangements and vessels are the very simplest that one can
possibly have: flasks, retorts, bottles, glasses, and ox bladders are
the things which I employ. The bladders, while they are still fresh, are
rubbed, and blown up very fully, then tightly tied and hung up to dry.
When I wish to use such a bladder and find it blown up just as fully as
at first, I am thereby assured that it is tight.

(_a._) When I wish to collect any kind of air in a bladder, for example
the phlogisticated acid of nitre (§ 13), I take a soft bladder smeared
inside with a few drops of oil, and place in it some filings of a metal,
as iron, zinc, or tin; I then press the air as completely as possible
out of the bladder and tie it very tightly over a small bottle into
which some _aqua fortis_ has been poured; I then partly unfold the
bladder so that a few iron filings may fall into the _aqua fortis_,
according as this dissolves the bladder becomes expanded. When I have
collected enough of the air so produced, I tightly tie up the bladder
with a thread close above the mouth of the bottle, and then detach it
from the bottle. (_b._) If this phlogisticated acid of nitre is mixed
with aerial acid, which is the case when the acid of the nitre is
extracted over sugar, I tie a bladder, softened with some water, to the
extreme end of the neck of the retort A (Fig. 3); in order, however,
that I may properly prevent the escape of the air it is necessary to
scratch the neck of the retort somewhat at this place with a flint.
(Retorts which I employ for investigations of this kind I have blown not
larger than to be capable of holding only from one half to three ounces
of water, but which have at the same time a neck which is about half an
ell long, and that for this reason that the attached bladder may not be
destroyed during the operation by the heat of the furnace or by the hot
vapours.) Into this bladder I pour some milk of lime (§ 22), and press
the air out as fully as possible. This lime will absorb the aerial acid
during the distillation, and leave the phlogisticated acid of nitre
untouched. (_c._) In exactly the same way as is described in _a_ I also
collect aerial acid and the inflammable air of sulphur (of which I shall
speak further on). But if the bladders are moist, or even if only the
air surrounding them is so, both these kinds of air penetrate completely
through the bladders in a few days; if the bladders and air are dry,
however, this does not take place. I obtain inflammable air from the
metals, as iron or zinc, in exactly the same way, except that I place
the bottle in warm sand. This air is still more subtle than the
preceding; it penetrates through the fine pores of the bladder in a few
days, although air and bladder are dry. I frequently experienced this
to my vexation. (_d._) I not infrequently catch air in bladders, without
any bottles. I place in a soft bladder (AA, Fig. 4) the material from
which I intend to collect the air, for example, chalk; above this chalk
I draw the bladder together with twine BB; I then pour above it the acid
diluted with water and press out the air as completely as possible; I
finally tie up the bladder above at CC. I then untie the twine B, when
the acid runs upon the chalk; it immediately drives out the aerial acid,
whereupon the bladder must expand. (_e._) When I require to get an air
out of the bladder into a flask, glass, retort, or bottle, I fill such
apparatus with water and place in it a tightly fitting cork; I then tie
the bladder which contains the air, that is, the opening from C to D
(Fig. 4), very firmly over such bottle; I then invert the bottle so that
the bladder comes below and the bottle above, whereupon I hold the
bottle with the left hand and with the right I withdraw the cork; I hold
this cork firmly between both fingers inside the bladder until the water
has flowed out of the bottle into the bladder, and the air has mounted
out of the bladder into the bottle; I then put in the cork and detach
the bladder from the bottle. When I wish to preserve the air for a long
time I place the neck of the bottle in a vessel with water. (_f._) When
there is aerial acid in the bladder, or another air which can unite with
water, and I wish to unite it with water neatly, I fill a bottle with
cold water, and, after it has been attached to the bladder, I permit
about the fourth part to run into the bladder; I then push the cork,
which, as previously, was firmly held within the bladder, into the
bottle again; I then shake the bottle gently, when the air will dissolve
in the water. Thereupon I make a small opening by means of the cork,
when air passes out of the bladder into the bottle in order to fill up
again the space which has become empty, without any water running into
the bladder; I then push the cork again into the bottle and shake the
water contained in it. I repeat this operation two or three times more,
when the water is saturated with this air. (_g._) When I wish to mix
together two kinds of air in a flask or bottle, I permit in the first
place just as much water, by measure, to run from the bottle filled with
water, into the bladder, as I wish to have of air. I then tie the bottle
over with a bladder filled with another kind of air and permit the
remaining water to run into the bladder, whereupon I immediately replace
the cork in the bottle, as soon as the last of the water has run out.
(_h._) When I wish to have in a bladder an air collected in a bottle, I
reverse the operation. That is to say, I fill the bladder with as much
water as I wish to have in it of air and tie it up at the top; I then
tie this bladder tightly over the top of the bottle and untie the
ligature of the bladder, draw the cork out of the bottle and so permit
the water to run out of the bladder into the bottle. I then tie up the
bladder, which now contains the air out of the bottle, and detach it
from the bottle. (_i._) When I have in a bottle an air mixed with
another kind of air which can be absorbed by water or lime, but wish to
know how much of each kind is present in the bottle, I tie over it a
bladder into which so much milk of lime has been poured that the bottle
can be filled with it; I then withdraw the cork and permit the water or
milk of lime to run into the bottle. I afterwards invert the bottle and
permit the milk of lime to flow again into the bladder; I repeat this
running out and in several times. So much air by measure has been
absorbed as there now remains behind of milk of lime in the bottle.

These are the methods which I employed in my investigations of air. I
admit that they will not particularly please some, because they do not
decide with great exactness. They afforded me satisfaction, however, in
all my investigations; and people will often split a hair where it is
not in the least necessary.


+31. Continuation of the Experiment mentioned in § 29+ ...

Anyone might object and say that the air obtained according to § 29 is
perhaps nothing else than a dry acid of nitre converted into elastic
vapours. But if this opinion had any foundation, this air should not
only be corrosive, but should also produce nitre anew with alkalies.
This, however, does not occur. Nevertheless, this objection would
possess considerable weight were I not able to prove that several
substances produce the same air as the acid of nitre does during
distillation. But proof of this is not wanting.

I have proved in a treatise on manganese, which is to be found in the
Transactions of the Royal Swedish Academy of Sciences for the year 1774,
that this mineral is not soluble in any acid unless an inflammable
substance be added, which communicates the phlogiston to the manganese,
and by this means effects an entrance of the latter into the acids. I
have shown in the same place that vitriolic acid, nevertheless, during a
strong distillation with powdered manganese, unites with it and makes it
soluble in water; and if this manganese is separated again from the
vitriolic acid by means of precipitating agents, there are found in it
the most distinct traces of the inflammable substance.... I had already
observed a few years ago, that if in the calcination of manganese with
oil of vitriol in an open crucible, some coal dust was driven by the
current of air over the surface of this mixture, these fine coals took
fire in the same instant with very great brilliancy. I accordingly made
the following experiments.


+32. First Experiment.+--I mixed so much concentrated oil of vitriol
with finely powdered manganese that it became a stiff magma. I distilled
this mixture from a small retort on the open fire. In place of a
receiver I made use of a bladder, empty of air, and, in order that the
vapours which might pass over should not attack the bladder, I poured
into it some milk of lime (§ 30, letter _b_). As soon as the bottom of
the retort became red hot, an air passed over which gradually expanded
the bladder. This air had all the properties of a pure fire-air.


+33. Second Experiment.+--When I distilled two parts of finely
pulverised manganese with one part of the phosphorous acid of urine in
the same way as is indicated in the preceding paragraph, I likewise
obtained fire-air.


+34. Third Experiment.+--(_a._) I dissolved in _aqua fortis_ the white
magnesia employed in medicine; I evaporated this solution to dryness. I
then placed the salt in a small retort for distillation, as is described
in § 32. Even before the retort was red hot the acid of nitre separated
from the magnesia, and that in blood-red vapours; and at the same moment
the bladder began to expand. The air thus obtained was my fire-air.

It is thus seen constantly that the acid of nitre goes off again
blood-red when separated by means of heat from the metals which had been
dissolved in this menstruum.

(_b._) I distilled mercurial nitre in the foregoing manner until the
acid of nitre had separated from the residual red precipitate. In this
case also I obtained our fire-air.... Whence comes the boiling of nitre,
fused in a crucible and obscurely red-hot? Neither smoke nor vapours are
seen to rise from it, and yet coal dust flying above the open crucible
takes fire, burning brilliantly. Whence comes it that such nitre
maintained in red-hot fusion in a glass retort for half an hour, becomes
moist in open air and deliquesces after cooling, and still does not
show any trace of alkali? (§ 27, letter _c._) What is the reason that
this liquefied nitre permits its volatile acid to escape immediately,
when rubbed or mixed with the vegetable acids?... If the chemists of the
preceding century had thought worthy of a more particular examination,
the elastic fluids resembling air which manifest themselves in so many
operations, how advanced should we now be! They desired to see
everything in corporeal form, and to collect everything as drops in the
receiver. This is now for the first time better inquired into, and the
air has begun to be carefully examined: and who is there who does not
perceive the advantage which the results of such experiments carry with
them?

       *       *       *       *       *

+35. Fourth Experiment.+--I put an ounce of purified nitre into a glass
retort for distillation and made use of a bladder, moistened and emptied
of air, in place of a receiver (Fig. 3). As soon as the nitre began to
glow it also began to boil, and at the same time the bladder was
expanded by the air that passed over. I proceeded with the distillation
until the boiling in the retort ceased, and the nitre was about to force
its way through the softened retort. I obtained in the bladder the pure
fire-air which occupied the space of 50 ounces of water. This is the
cheapest and best method of obtaining fire-air.

       *       *       *       *       *

+38. Fifth Experiment.+--I took a silver solution prepared with acid of
nitre, and precipitated it with alkali of tartar; I washed the
precipitate thus obtained and dried it. I then placed this calx of
silver in a small glass retort on the open fire for reduction, and
fastened an empty bladder to the neck. The bladder was immediately
expanded by the air which passed over. After the end of the distillation
I found the calx of silver half melted together in the retort, with its
metallic lustre; however, as I had effected the precipitation with
alkali of tartar, and this is always united with a quantity of aerial
acid which attaches itself to the calx of silver in the precipitation,
so this acid was necessarily present also in the bladder. This acid was
removed from it by milk of lime (§ 30, letter _i._), and there remained
behind one-half of pure fire-air.


+39. Sixth Experiment.+--I precipitated with alkali of tartar a solution
of gold which was made with _aqua regia_; I reduced in the foregoing
manner the washed and dried calx of gold. I obtained in this case the
same fire-air, except that no aerial acid accompanied it. This is not to
be wondered at, because the saturated solution of gold effervesces with
the alkali, which does not take place with the solution of silver.


+40. Seventh Experiment.+--It is likewise known that the red precipitate
of mercury regains its flowing condition without the addition of an
inflammable substance. Since mercury, however, really loses its
phlogiston as well by means of vitriolic acid as of the acid of nitre,
it must necessarily assume this again as soon as it recovers its
metallic property.

(_a._) I added a solution of alkali of tartar, drop by drop, to a
solution of corrosive sublimate. I washed the brown-red precipitate
obtained, and dried it; then I placed it, for reduction, upon the open
fire in a small retort, which was provided with a bladder empty of air.
As soon as the calx began to glow, the bladder became expanded, and
quicksilver rose into the neck. The fire-air obtained had some aerial
acid mixed with it.

(_b._) Mercury converted into calx by the acid of nitre, or red
precipitate, treated in the same way behaved similarly. In this case I
obtained a pure fire-air, without any aerial acid in it.


+41. Eighth Experiment.+--I have proved, in a treatise on arsenic
communicated to the Royal Swedish Academy of Sciences, that this
poisonous substance is compounded of a peculiar acid and an inflammable
substance. I also shewed in the same treatise how this acid can be
sublimed into ordinary arsenic simply by continued heat; and although I
clearly perceived the reason for this, even at that time, still I was
unwilling to mention it there in order to avoid prolixity. I placed some
of this fixed acid of arsenic in a small retort with a bladder attached,
for distillation. When the acid had gone into fusion, and glowed
brightly, it began to boil; during this ebullition arsenic rose into the
neck and the bladder became expanded; I continued with this heat as long
as the retort would hold out. The air collected was likewise fire-air.
In the same treatise I made mention of a peculiar explosion which took
place in the distillation of zinc with the acid of arsenic. How clear,
how manifest does the explanation of this phenomenon not become when one
is satisfied that in this case fire-air is present in the retort in its
greatest purity, and the zinc is in red hot fusion? What more is
necessary for its ignition?

I have very often regarded with pleasure the brightly glowing sparks
which are produced in a retort by heat alone, during the reduction of
metallic calces, when only a very little coal dust is mixed along with
it.

We shall now see whether this fire-air is not the same air which had
been lost without fire (§§ 8-15), and with fire (§§ 17-23).


+42. First Experiment.+--I filled a bottle which was capable of holding
16 ounces of water with pure fire-air according to the method which is
described in § 30, letter e. I placed the bottle, inverted, in a glass
which was filled with a solution of liver of sulphur. The solution rose
a little into the bottle hour by hour, and after the lapse of 2 days the
bottle was filled with it.


+43. Second Experiment.+--I mixed in a bottle 14 parts of that air from
which the fire-air had been removed by liver of sulphur (§ 8), and which
I have called vitiated air (§ 29), with 4 parts of our fire-air, and
placed the bottle, inverted and open, in a vessel which was also filled
with a solution of liver of sulphur. After 14 days the 4 parts of
fire-air were lost, and the solution had risen into their place.


+44. Third Experiment.+--After I had filled a bottle with our air, I
poured some colourless animal oil into it and closed it tightly. After a
few hours it had already become brown, and by the next day black. It is
no small inconvenience to preserve this oil white in apothecaries'
shops. It is found necessary to pour this oil into small phials, and to
preserve it most carefully from the access of air. When such a
colourless oil is mixed with any acid, the acid, as well as the oil,
becomes black even in an hour, although it has been diluted with water.
Even vinegar has the same effect. There is no other reason, therefore,
why the oil becomes at once black in the air, than that the fire-air
present in the air deprives it of its phlogiston, and thereby develops a
subtle acid, previously united with this phlogiston, which produces the
blackness.


+45. Fourth Experiment.+--(_a._) Into a bottle of 7 ounces, which was
filled with fire-air, I put a piece of phosphorus from urine and closed
it with a cork. I then heated, by means of a burning candle, the place
where the phosphorus lay; the phosphorus took fire with very great
brilliancy. As soon as the flame had gone out, the bottle broke into
fragments.

(_b._) As the bottle in the foregoing experiment was very thin, I
repeated it with a somewhat thicker bottle, and after everything had
become cold I wanted to take the cork out of the bottle under water. It
was not possible for me to do this, however, so tightly did the
external air press the cork into the bottle. Accordingly I forced it
inside the bottle; thereupon water entered the bottle and filled it
almost completely. Since the first bottle was only very thin, the reason
that it was crushed must be ascribed to the external air.

(_c._) When I mixed vitiated air with one third of fire-air, and burned
a piece of phosphorus in the mixture, only 1/3 of it was absorbed.


+46. Fifth Experiment.+--I also repeated the same experiment which is
described in § 19, only with this difference that I took the tube
longer, and filled the flask with my fire-air. It was pleasing to
observe how the water rose gradually into the flask; and how the flame
went out when 7/8 of the flask were full of water.


+47. Sixth Experiment.+--I laid some glowing coals upon the stand (§ 21,
letter _c_), and placed over them a flask which was filled with
fire-air. The coals had not even reached the air in the flask before
they began to burn very brilliantly.

After everything had become cold, I made an aperture under the flask,
whereupon the fourth part became filled with water. But when I removed,
by means of milk of lime, the aerial acid which was present in the
residual air (§ 22) there remained in the flask only the fourth part. In
this air a candle could still burn.


+48. Seventh Experiment.+--I also examined the behaviour of fire-air
with sulphur (§ 23). As soon as the burning sulphur came into contact
with the fire-air contained in the flask, the flame became much larger
and brighter. When this fire had gone out, the water in the dish had
found a way to come through the mass into the flask, which became 3/4
filled with it. As I employed for these last 3 experiments a flask which
was only of 30 ounces measure, I was obliged to arrange the stand (§ 21)
to suit.


+49.+ I have mentioned (§ 16) that I found vitiated air lighter than
ordinary air. Must it not follow from this that the fire-air is heavier
than our air? As a matter of fact, I actually found, when I accurately
weighed as much fire-air as occupied the space of 20 ounces of water,
that this was almost 2 grains heavier than the same bulk of common air.


+50.+ These experiments shew, therefore, that this fire-air is just that
air by means of which fire burns in common air; only it is there mixed
with a kind of air which seems to possess no attraction at all for the
inflammable substance, and this it is which places some hindrance in the
way of the otherwise rapid and violent inflammation. And in fact, if air
consisted of nothing but fire-air, water would surely render small
service in extinguishing outbreaks of fire. Aerial acid mixed with this
fire-air, has the same effect as vitiated air. I mixed one part of
fire-air with 4 parts of aerial acid; in this mixture a candle still
burned moderately well. The heat which lurks in the small interstices of
the inflammable substance cannot possibly make up so much heat as is
felt in fire; and I think I am not mistaken when I conclude from my
experiments that the heat is really brought forth and produced in the
first place from fire-air and the phlogiston of the inflammable
substance....

       *       *       *       *       *


+80.+ I had long wished to have some of the precipitate of mercury _per
se_, in order to see whether it also would yield fire-air during
reduction by means of heat alone. At length I obtained some from my much
esteemed friend Doctor Gahn. This so-called precipitate had the
appearance of small dark-red crystals resembling cinnabar. Now, as I
know that mercury cannot be dissolved in muriatic acid unless it has
lost its phlogiston, which takes place during its solution in acid of
nitre or in vitriolic acid; and as this is also the reason why nitre
must be present in a mixture of calcined vitriol, common salt, and
quicksilver, I therefore poured muriatic acid upon a part of this red
precipitate; the solution was soon formed and was somewhat hot; I
evaporated it to dryness and increased the heat. Everything sublimed,
and a true corrosive sublimate was formed. Hence this precipitate,
produced by heat alone, is a calcined mercury. I then placed the other
part of this precipitate over the fire in a small glass retort to which
I had fastened an empty bladder. As soon as the retort became red hot
the bladder became expanded, and at the same time the reduced mercury
rose into the neck. In this case no red sublimate arose as customarily
takes place with that calx which is prepared by the acid of nitre. The
air obtained was a pure fire-air. This is a remarkable circumstance,
that the fire-air which had previously removed from the mercury its
phlogiston in a slow calcination, gives this same phlogiston up to it
again when the calx is simply made red-hot. Still we have several such
phenomena, where heat similarly alters the attractive forces between
substances.

       *       *       *       *       *


+83. Air is a Dulcified Elastic Acid.+

In the foregoing experiments I have demonstrated the two proximate
constituents of common air, because it was not necessary to know
anything more about it for a clear knowledge of fire. I shall now go
further, and see whether a still deeper decompounding of air is
possible.

+First Experiment.+--I placed a rat in a flask capable of holding 4
quarts of water; I gave it some bread softened in milk and closed the
flask with a wet bladder. It died 31 hours afterwards. I then held the
flask, inverted, under water and made a hole in the bladder, when two
ounces of water rose into it. This small diminution of the air was
probably caused by the heat which the rat took with it, which had
previously driven the air out.


+84. Second Experiment.+--I took a large soft bladder and fastened a
tube into its opening; then I filled it with the air out of my lungs,
and held the tube and bladder with my right hand and closed my nostrils
with the left. I respired the air as long as I could, and was able to
make 24 inspirations (regarding which it is to be observed that at the
last I was obliged to draw the whole bladder full of air into my lungs
at once, while at the beginning only the half of it was necessary). I
then closed the tube with my finger, and tied up the bladder. This air
had properties similar to the preceding in which the rat died. That is
to say, it contained one-thirtieth part of aerial acid, which I
separated from it by milk of lime; and a burning candle at once went out
in it.


+85. Third Experiment.+--I placed a few flies in a bottle into which I
had put some honey smeared upon paper. After a few days they had died.
They likewise had not absorbed any air; milk of lime, however,
diminished this air about one fourth part, and the remainder
extinguished fire.

I then took a bottle of 20 ounces measure and bored a hole in the bottom
of it with the corner of a broken file (Fig. 5, A). Into this bottle I
put a small piece of unslaked lime, and closed the mouth with a cork
through which I had previously fixed a tube B. Round about this cork I
placed a ring of pitch, and placed over it an inverted glass C, into
which I had previously put a large bee and had given it some honey which
was smeared upon paper; but in order that no air could penetrate within
the ring of pitch, I pressed the glass firmly in; I afterwards placed
the bottle in the dish D, into which I poured so much water that it was
half immersed in it; as soon I observed that the bottle was raised by
the water, I put a small weight upon the glass. The water rose a little
into the bottle every day through the opening A; and I also shook the
bottle a little sometimes in order that the skin which formed over the
milk of lime might break. After the lapse of seven days the water had
risen to E, and the bee was dead. Occasionally I put 2 bees into the
glass C, when just as much air was converted into aerial acid in half
the time. Caterpillars and butterflies behaved in exactly the same way.


+86. Fourth Experiment.+--I placed some peas in a small flask, which was
capable of holding 24 ounces of water, and poured so much water upon
them that they were half covered with it; I then closed the flask. The
peas began to strike roots, and grew up. As I found after 14 days that
they would not increase further, I opened the flask, inverted, under
water, and found the air neither increased nor diminished. The fourth
part, however, was absorbed by milk of lime, and the remaining air
extinguished flame. I kept fresh roots, fruits, herbs, flowers, and
leaves, each by itself, in the flask, and after a few days I likewise
observed the fourth part of the air converted into aerial acid. If flies
are placed in such air they die immediately.


+87.+ These are accordingly strange circumstances, that the air is not
noticeably absorbed by animals endowed with lungs, contains in it very
little aerial acid, and yet extinguishes fire. On the other hand insects
and plants alter the air in exactly the same way, but still they convert
the fourth part of it into aerial acid. Accordingly I was curious to
know whether the fire-air was not that which was here converted into
aerial acid, because in these latter experiments just as much of the air
was converted into aerial acid as there was of fire-air present in it.


+88. Fifth Experiment.+--In a bottle of 20 ounces capacity, I mixed one
part of fire-air with 3 parts of the preceding air in which peas would
not any longer grow, and from which the aerial acid was separated. (That
is to say, I filled the bottle with water, and placed 4 peas in it; I
then allowed one fourth of the water to run into the bladder in which
fire-air was contained, and the remainder into another bladder in which
this vitiated air was contained (§ 30, _g._), while I took care that the
peas did not fall into the bladder. I also left so much water behind,
that the peas were half covered with it.) Here also I observed the peas
growing up, and after they would not increase any more I found this air
likewise not absorbed, but almost the fourth part was absorbed by milk
of lime. Hence it is the fire-air which is here converted into aerial
acid. In 3 parts of aerial acid and one part of fire-air peas do not
grow. I mixed vitiated air (§ 20) with fire-air which behaved in just
the same way: that is to say the fire-air was converted into aerial
acid.


+89. Sixth Experiment.+--I mixed, in the same proportions, fire-air and
air vitiated by peas, and filled a bladder with it. Then when I had
completely exhaled the air present in my lungs, I respired this newly
compounded air as many times as possible. I then found that it contained
very little aerial acid in it, and when this was separated from it, it
extinguished fire. I believe that one must ascribe to the blood present
in the pulmonary veins, the effect which animals endowed with lungs have
upon the air. The following experiment gives me cause for this.

It is known that freshly drawn blood, when it stands in the open air,
assumes a fine red on the surface, and that the under portions likewise
become red when they come into contact with the air. Does the air in
this case undergo any alteration? I filled a flask one third part with
freshly drawn ox blood, closed it tightly with a bladder, and shook up
the blood frequently. Eight hours afterwards I neither found aerial acid
in this air, nor that its bulk was diminished; but the flame of a candle
was immediately extinguished in it. I made this experiment in winter
time, from which may be gathered that the effect cannot be ascribed to
any putrefaction, for this blood was found still fresh 6 days
afterwards, and besides, all putrefactions produce aerial acid. I was
now curious to know how fire-air by itself would behave with animals and
plants.


+90. Seventh Experiment.+--(_a._) I put 2 ounces of nitre into a small
glass retort upon glowing coals, and attached a large bladder softened
with water (§ 35), and allowed the nitre to boil until I had received
3/4 of a quart of fire-air in the bladder. I then tied up the bladder
and separated it from the retort; I then placed a tube in its opening,
and after I had completely emptied my lungs, I began to respire air from
this bladder (§ 84). This proceeded very well, and I was able to make 40
inspirations before it became difficult for me; eventually I expelled
the air again from my lungs as completely as possible. It did not seem
to have diminished particularly, and when I filled a bottle with it and
introduced a burning candle, this still burned. I then began to respire
this air anew, and was able to make 16 more inspirations. It now
extinguished the flame, but I found only some traces of aerial acid in
it. (_b._) I was surprised that I was not able the first time to take
away from this air the property of allowing fire to burn in it; I
thought that perhaps the great humidity prevented me from drawing this
air into my lungs so often as was really possible. Accordingly I
repeated the same experiment, only with this difference, that I put a
handful of potashes into the bladder before the fire-air was driven into
it. I then began to draw this air into my lungs, and counted 65
inspirations before I was compelled to desist. But when I lowered a
burning candle into this air, it still burned well, although only for a
few seconds.


+91. Eighth Experiment.+--I closed the hole in the bottle at A (Fig. 5)
with a cork, as also the tube B, and then filled the bottle with
fire-air (§ 30, _e._). Then I had at hand the glass C, in which I had
placed 2 large bees, and had provided some honey for their stay. I
opened the stopped-up tube, placed this glass over it as quickly as
possible, and pressed it into the ring of pitch. I afterwards placed the
whole in the dish D, which I had filled with milk of lime, and withdrew
the cork at A. In this case I observed the milk of lime to rise a little
into the bottle every day, and after 8 days had elapsed the bottle was
almost completely filled with it, and the bees were dead.


+92. Ninth Experiment.+--Plants, however, will not grow noticeably in
pure fire-air. I filled with this air a bottle capable of holding 16
ounces of water, and which contained 4 peas (§ 88). They got roots, but
did not grow up at all; with milk of lime the twelfth part was absorbed.
I then filled this air into another bottle which also contained 4 peas.
After 14 days they had got roots, but also did not grow up, and with
milk of lime likewise only the twelfth part was absorbed. I repeated
this experiment 3 times more with the same air, and it was observed that
the fourth and fifth times the peas had grown upwards a little. There
still remained one-half of the whole air, and in this fire could still
burn. There is no doubt that the whole quantity of fire-air could have
been converted into aerial acid if I had continued the operation longer.
It may also be observed that the peas act more strongly upon the
fire-air when they send out roots than subsequently.


+93.+ Hence it is the fire-air by means of which the circulation of the
blood and of the juices in animals and plants is so fully maintained.
Still it is a peculiar circumstance that blood and the lungs have not
such action upon fire-air as insects and plants have, for the latter
convert it into aerial acid, and the former into vitiated air (§§ 29,
89, 90). It is not so easy to furnish the reason for this, yet I will
risk it. It is known that the acids lose those properties by which they
reveal themselves as acids, by the addition of the inflammable
substance, as sulphur, the elastic acid of nitre, regulus of arsenic,
sugar, and the like, plainly shew. I am inclined to believe that
fire-air consists of a subtle acid substance united with phlogiston, and
it is probable that all acids derive their origin from fire-air. Now, if
this air penetrates into plants, these must attract the phlogiston, and
consequently the acid, which manifests itself as aerial acid, must be
produced. This they again give up. The objection that so great a
quantity of aerial acid is nevertheless obtained in the destruction of
plants, and that, consequently, these must attract the aerial acid, has
no weight, since otherwise the air in my vessels in which the peas were
contained must have become for the most part lost, which, however, did
not take place.... If plants abstract the phlogiston from the air, the
aerial acid must be lighter. But experiment shows me the opposite; I
found it, after careful weighing, somewhat heavier, but this is not
contrary to my opinion; as it is known that all acids retain water
strongly, the aerial acid must possess the same property, and this may
consequently cause the most of the weight. If all this is accurate,
another question then arises: Why do not blood and the lungs likewise
convert fire-air into such an aerial acid? I take the liberty here also
of giving my opinion of this, for how would all these laboriously
executed experiments help me if I had not the hope of coming by means
of them nearer to my ultimate object, the truth? Phlogiston, which makes
most substances with which it unites liquid as well as mobile and
elastic, must have the same effect upon blood. The globules of blood
must attract it from the air through the small pores of the lungs. By
this union they become separated from one another, and are consequently
made more liquid. They then appear bright red (§ 89). They must,
however, give this attracted phlogiston up again during the circulation,
and in consequence, be placed in a condition to absorb the inflammable
substance anew from the air at that place where they are in the most
intimate contact with it, that is, in the lungs. Where this phlogiston
has gone to during the circulation of the blood, I leave to others to
ascertain. The attraction which the blood has for phlogiston cannot be
so strong as that with which plants and insects attract it from the air,
and then the blood cannot convert air into aerial acid; still it becomes
converted into an air which lies midway between fire-air and aerial
acid, that is, a vitiated air; for it unites neither with lime nor with
water after the manner of fire-air and it extinguishes fire, after that
of aerial acid. But that the blood really attracts the inflammable
substance I have additional experiment to prove, since I have removed
phlogiston by help of my lungs from inflammable air, and have converted
this into vitiated air.

I filled a bladder with the air which one obtains from iron filings and
vitriolic acid (§ 30, _c._), and respired it in the manner previously
described (§ 84). I was only able to inhale it 20 times, and after I had
somewhat recovered, I expelled the air once more from my lungs as
completely as possible, and again inhaled this inflammable air: after 10
inhalations I was compelled to desist from it, and observed that it
could no longer be kindled, and also would not unite with lime water.
In one word it was a vitiated air.

I kept a piece of sulphur in continuous ebullition over the fire in a
retort, capable of holding 12 ounces of water, with an empty bladder
attached in place of a receiver, the retort also placed so that the
sulphur which rose into the neck could run back again. After all had
become cold, I found the air neither increased nor diminished: it smelt
slightly hepatic, and extinguished a burning candle. I shall prove
further on that sulphur can unite with more phlogiston; and it seems to
me to follow from this experiment that something inflammable from the
air had deposited itself upon the sulphur, and that the air had thereby
acquired the property of a vitiated air. It is, however, also remarkable
that other bodies which attract the inflammable substance more strongly,
as for example, the fuming acid of nitre, do not abstract it from the
air. It is likewise strange that I was able to inhale the inflammable
air into my lungs only 20 times; and I observe here as something
peculiar that, if I mistake not, I became very warm a quarter of an hour
afterwards. It is also to be observed that fire-air, vitiated by the
lungs, extinguishes fire; why does not the aerial acid attract the
phlogiston again? why not also the vitiated air? Mr. Priestley indeed
has accomplished this, but it did not succeed with me however much I
also wished it. He has converted aerial acid into wholesome air by means
of a mixture of iron filings, sulphur, and some water. When I desired to
repeat this experiment, the aerial acid was always absorbed by the iron
filings. I likewise powdered finely some iron filings which had been
fused together with excess of sulphur, moistened this with water, and
preserved it in a bottle which was filled with aerial acid: but with the
same result. After 2 two days the aerial acid was almost entirely
absorbed. This philosopher also says that he has made vitiated air
wholesome again by agitation with water. I must admit, however, that
with me this likewise failed. I filled a flask one fourth part with
vitiated air, and the remainder with fresh water; I closed the flask
very tightly, and shook it up and down for almost a whole hour. Then
when I collected this air in a bladder, and from this in a bottle, I
found that the candle was extinguished afterwards as it was before. He
mixed with water, by agitation, the inflammable air from metals; this
also would not succeed with me, although I used only little inflammable
air, and much water. He also observed that plants made vitiated air
wholesome again. It follows from my experiments that they vitiate air. I
kept plants, in the dark as well as exposed to sunlight, in a flask
which was filled with vitiated air and carefully secured (which careful
securing must really be attended to). I tested a little of this air
every 2 days, and always found it vitiated.


+94.+ Water has the peculiar property of separating the proximate
constituents of air; of uniting with fire-air; and of entering into no
kind of union with vitiated air. (1.) I filled a large bottle with
boiled water which had been cooled shortly before, and permitted the
tenth part to run out. I then placed the bottle, inverted and open, in a
vessel with water. I observed the quantity of air to diminish a little
every day, and when this diminution ceased, I collected the remaining
air first in a bladder (§ 30, _h._), and from the bladder in a bottle (§
30, _c._), and brought a burning candle into the bottle; it had scarcely
reached the mouth when it went out. (2.) I then took the same kind of
water freed from air, filled a bottle with it, and permitted the tenth
part of it to run into a bladder filled with vitiated air. I next placed
the bottle, inverted, in a vessel with water, and observed the space
which the air occupied in it. I found, 14 days afterwards, that the
water had not absorbed the smallest quantity of it. (3.) I placed a
large bottle, from which the bottom was knocked out, in a deep kettle
with water, so that the water outside reached above the top of the
bottle. I then tied a bladder, empty of air, over the top of the bottle,
and made the water boil up once over the fire. The air which was in that
portion of the water contained under the bottle rose into the bladder;
and after I had tied up the bladder, and detached it front the bottle, I
filled a phial with it, and put a small burning candle into it; it
burned there more brightly than in ordinary air.

This fire-air, dissolved in water, must be as indispensable for aquatic
animals as for those which live upon the earth. They must draw it into
their bodies, and convert it either into aerial acid or into vitiated
air. Into whichever kind it is, however, it must always become separated
from the water again, for as aerial acid it does not remain with the
water in the open air, and vitiated air cannot unite with water at all
(No. 2), the water is then in a condition again to absorb fire-air anew,
and to convey it to the animals. My experiments made with respect to
this matter agree with this entirely. I allowed a few leeches to remain
in a bottle, which was half filled with water and well closed, until
they died. I then examined the air standing over this water. It had no
smell, nor had the water; it appeared to have increased a little and it
extinguished fire. It seems that these creatures live only upon the
phlogiston in fire-air, perhaps also upon the heat. I have preserved
them alive in water, and that the same water, for two years; the bottle
was only tied over with gauze. I have a convenient method to ascertain
whether fire-air is present in water or not. I take, for example, an
ounce of it, and add to it about 4 drops of a solution of vitriol of
iron, and 2 drops of a solution of alkali of tartar which has been
somewhat diluted with water. A dark green precipitate is immediately
formed, which, however becomes yellow in a couple of minutes if the
water contains fire-air; but if the water has been boiled, and has
become cold without access of air, or if it is even a recently distilled
water, the precipitate retains its green colour, and does not become
yellow sooner than an hour afterwards, and not yellow at all if it is
protected from access of air in full bottles. I have already shown (§
15) that the green precipitate of iron owes its colour to phlogiston
which still adheres to the earth, and it follows from this that
fire-air, although not in the elastic condition, is able to attract
phlogiston. The following experiment likewise shewed me that aquatic
animals take fire-air from the water. I placed a leech in a bottle which
was completely filled with water, and was protected from every kind of
air. After two days it was almost dead. I then examined the water in the
manner described above, and found that the earth of iron retained its
green colour. The swelling up of peas in cold water is to be ascribed
mainly to the fire-air present in the water. If a bottle is filled full
of water and a few peas are placed in it, after 24 hours the water
contains aerial acid it is true, but no fire-air. In water boiled and
become cold, peas swell up only a little. I perceive in this the reason
why the waters distilled from plants not only lose their smell, but why
also a mucilaginous substance settles to the bottom, when the bottles
are frequently opened, whereas the same waters, in perfectly full
bottles, retain their smell and clearness unchanged. All plants
communicate to water some mucilaginous material which is carried over
along with it. Fire-air is the chief cause of this corruption; if this
enters the water again, it attracts to itself the inflammable substance
from the subtle oily and mucilaginous matter, and alters the whole of
the water.

       *       *       *       *       *


Transcriber's Note

All bold text has been surrounded by + signs. Italic text is
denoted by underscores.





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