MISCELLANEOUS OBSERVATIONS.
1. As many of the preceding observations relate to the _vinous_ and
_putrefactive_ fermentations, I had the curiosity to endeavour to
ascertain in what manner the air would be affected by the _acetous_
fermentation. For this purpose I inclosed a phial full of small beer in
a jar standing in water; and observed that, during the first two or
three days, there was an increase of the air in the jar, but from that
time it gradually decreased, till at length there appeared to be a
diminution of about one tenth of the whole quantity.
During this time the whole surface of it was gradually covered with a
scum, beautifully corrugated. After this there was an increase of the
air till there was more than the original quantity; but this must have
been fixed air, not incorporated with the rest of the mass; for,
withdrawing the beer, which I found to be sour, after it had stood 18 or
20 days under the jar, and passing the air several times through cold
water, the original quantity was diminished about one ninth. In the
remainder a candle would not burn, and a mouse would have died
presently.
The smell of this air was exceedingly pungent, but different from that
of the putrid effluvium. A mouse lived perfectly well in this air, thus
affected with the acetous fermentation; after it had stood several days
mixed with four times the quantity of fixed air.
2. All the kinds of factitious air on which I have yet made the
experiment are highly noxious, except that which is extracted from
saltpetre, or alum; but in this even a candle burned just as in common
air[10]. In one quantity which I got from saltpetre a candle not only
burned, but the flame was increased, and something was heard like a
hissing, similar to the decrepitation of nitre in an open fire. This
experiment was made when the air was fresh made, and while it probably
contained some particles of nitre, which would have been deposited
afterwards. The air was extracted from these substances by heating them
in a gun-barrel, which was much corroded and soon spoiled by the
experiment. What effect this circumstance may have had upon the air I
have not considered.
November 6, 1772, I had the curiosity to examine the state of a quantity
of this air which had been extracted from saltpetre above a year, and
which at first was perfectly wholesome; when, to my very great surprize,
I found that it was become, in the highest degree, noxious. It made no
effervescence with nitrous air, and a mouse died the moment it was put
into it. I had not, however, washed it in rain-water quite ten minutes
(and perhaps less time would have been sufficient) when I found, upon
trial, that it was restored to its former perfectly wholesome state. It
effervesced with nitrous air as much as the best common air ever does;
and even a candle burned in it very well, which I had never before
observed of any kind of noxious air meliorated by agitation in water.
This series of facts, relating to air extracted from nitre, appear to me
to be very extraordinary and important, and, in able hands, may lead to
considerable discoveries.
3. There are many substances which impregnate common air in a very
remarkable manner, but without making it noxious to animals. Among other
things I tried volatile alkaline salts, and camphor; the latter of which
I melted with a burning-glass, in air inclosed in a phial. The mouse,
which was put into this air, sneezed and coughed very much, especially
after it was taken out; but it presently recovered, and did not appear
to have been sensibly injured.
4. Having made several experiments with a mixture of iron filings and
brimstone, kneaded to a paste with water, I had the curiosity to try
what would be the effect of substituting _brass dust_ in the place of
the iron filings. The result was, that when this mixture had stood about
three weeks, in a given quantity of air, it had turned black, but was
not increased in bulk. The air also was neither sensibly increased nor
decreased, but the nature of it was changed; for it extinguished flame,
it would have killed a mouse presently, and was not restored by fixed
air, which had been mixed with it several days.
5. I have frequently mentioned my having, at one time, exposed equal
quantities of different kinds of air in jars standing in boiled water.
_Common air_ in this experiment was diminished four sevenths, and the
remainder extinguished flame. This experiment demonstrates that water
does not absorb air equally, but that it decomposes it, taking one part,
and leaving the rest. To be quite sure of this fact, I agitated a
quantity of common air in boiled water, and when I had reduced it from
eleven ounce measures to seven, I found that it extinguished a candle,
but a mouse lived in it very well. At another time a candle barely went
out when the air was diminished one third, and at other times I have
found this effect lake place at other very different degrees of
diminution.
This difference I attribute to the differences in the state of the water
with respect to the air contained in it; for sometimes it had stood
longer than at other times before I made use of it. I also used
distilled-water, rain-water, and water out of which the air had been
pumped, promiscuously with rain water. I even doubt, not but that, in a
certain state of the water, there might be no sensible difference in
the bulk of the agitated air, and yet at the end of the process it would
extinguish a candle, air being supplied from the water in the place of
that part of the common air which had been absorbed.
It is certainly a little extraordinary that the very same process should
so far mend putrid air, as to reduce it to the standard of air in which
candles have burned out; and yet that it should so far injure common and
wholesome air as to reduce it to about the same standard: but so the
fact certainly is. If air extinguish flame in consequence of its being
previously saturated with phlogiston, it must, in this case, have been
transferred from the water to the air, and it is by no means
inconsistent with this hypothesis to suppose, that, if the air be over
saturated with phlogiston, the water will imbibe it, till it be reduced
to the same proportion that agitation in water would have communicated
to it.
To a quantity of common air, thus diminished by agitation in water, till
it extinguished a candle, I put a plant, but it did not so far restore
it as that a candle would burn in it again; which to me appeared not a
little extraordinary, as it did not seem to be in a worse state than air
in which candles had burned out, and which had never failed to be
restored by the same means.
I had no better success with a quantity of permanent air which I had
collected from my pump-water. Indeed these experiments were begun before
I was acquainted with that property of nitrous air, which makes it so
accurate a measure of the goodness of other kinds of air; and it might
perhaps be rather too late in the year when I made the experiments.
Having neglected these two jars of air, the plants died and putrefied in
both of them; and then I found the air in them both to be highly
noxious, and to make no effervescence with nitrous air.
I found that a pint of my pump-water contained about one fourth of an
ounce measure of air, one half of which was afterwards absorbed by
standing in fresh pump-water. A candle would not burn in this air, but a
mouse lived in it very well. Upon the whole, it seemed to be in about
the same state as air in which a candle had burned out.
6. I once imagined that, by mere _stagnation_, air might become unfit
for respiration, or at least the burning of candles; but if this be the
case, and the change be produced gradually, it must require a long time
for the purpose. For on the 22d of September 1772, I examined a quantity
of common air, which had been kept in a phial, without agitation, from
May 1771, and found it to be in no respect worse than fresh air, even by
the test of the nitrous air.
7. The crystallization of nitre makes no sensible alteration in the air
in which the process is made. For this purpose I dissolved as much nitre
as a quantity of hot water would contain, and let it cool under a
receiver, standing in water.
8. November 6, 1772, a quantity of inflammable air, which, by long
keeping, had come to extinguish flame, I observed to smell very much
like common air in which a mixture of iron filings and brimstone had
stood. It was not, however, quite so strong, but it was equally noxious.
9. Bismuth and nickel are dissolved in the marine acid with the
application of a considerable degree of heat; but little or no air is
got from either of them; but, what I thought a little remarkable, both
of them smelled very much like Harrowgate water, or liver of sulphur.
This smell I have met with several times in the course of my
experiments, and in processes very different from one another.
FOOTNOTES:
[10] Experiments, of which an account will be given in the second part
of this work, make it probable, that though a candle burned even _more
than well_ in this air, an animal would not have lived in it. At the
time of this first publication, however, I had no idea of this being
possible in nature.
PART II.
_Experiments and Observations made in the Year 1773, and the Beginning
of 1774._
SECTION I.
_Observations on ALKALINE AIR._
After I had made the discovery of the _marine acid air_, which the
vapour of spirit of salt may properly enough be called, and had made
those experiments upon it, of which I have given an account in the
former part of this work, and others which I propose to recite in this
part; it occurred to me, that, by a process similar to that by which
this _acid_ air is expelled from the spirit of salt, an _alkaline_ air
might be expelled from substances containing volatile alkali.
Accordingly I procured some volatile spirit of sal ammoniac, and having
put it into a thin phial, and heated it with the flame of a candle, I
presently found that a great quantity of vapour was discharged from it;
and being received in a vessel of quicksilver, standing in a bason of
quicksilver, it continued in the form of a transparent and permanent
air, not at all condensed by cold; so that I had the same opportunity of
making experiments upon it, as I had before on the acid air, being in
the same favourable circumstances.
With the same ease I also procured this air from _spirit of hartshorn_,
and _sal volatile_ either in a fluid or solid form, i. e. from those
volatile alkaline salts which are produced by the distillation of sal
ammoniac with fixed alkalis. But in this case I soon found that the
alkaline air I procured was not pure; for the fixed air, which entered
into the composition of my materials, was expelled along with it. Also,
uniting again with the alkaline air, in the glass tube through which
they were conveyed, they stopped it up, and were often the means of
bursting my vessels.
While these experiments were new to me, I imagined that I was able to
procure this air with peculiar advantage and in the greatest abundance,
either from the salts in a dry state, when they were just covered with
water, or in a perfectly fluid state; for, upon applying a candle to the
phials in which they were contained, there was a most astonishing
production of air; but having examined it, I found it to be chiefly
fixed air, especially after the first or second produce from the same
materials; and removing my apparatus to a trough of water and using the
water instead of quicksilver, I found that it was not presently absorbed
by it.
This, however, appears to be an easy and elegant method of procuring
fixed air, from a small quantity of materials, though there must be a
mixture of alkaline air along with it; as it is by means of its
combination with this principle only, that it is possible, that so much
fixed air should be retained in any liquid. Water, at least, we know,
cannot be made to contain much more than its own bulk of fixed air.
After this disappointment, I confined myself to the use of that volatile
spirit of sal ammoniac which is procured by a distillation with slaked
lime, which contains no fixed air; and which seems, in a general state,
to contain about as much alkaline air, as an equal quantity of spirit of
salt contains of the acid air.
Wanting, however, to procure this air in greater quantities, and this
method being rather expensive, it occurred to me, that alkaline air
might, probably, be procured, with the most ease and convenience, from
the original materials, mixed in the same proportions that chemists had
found by experience to answer the best for the production of the
volatile spirit of sal ammoniac. Accordingly I mixed one fourth of
pounded sal ammoniac, with three fourths of slaked lime; and filling a
phial with the mixture, I presently found it completely answered my
purpose. The heat of a candle expelled from this mixture a prodigious
quantity of alkaline air; and the same materials (as much as filled an
ounce phial) would serve me a considerable time, without changing;
especially when, instead of a glass phial, I made use of a small iron
tube, which I find much more convenient for the purpose.
As water soon begins to rise in this process, it is necessary, if the
air is intended to be conveyed perfectly _dry_ into the vessel of
quicksilver, to have a small vessel in which this water (which is the
common volatile spirit of sal ammoniac) may be received. This small
vessel must be interposed between the vessel which contains the
materials for the generation of the air, and that in which it is to be
received, as _d_ fig. 8.
This _alkaline_ air being perfectly analogous to the _acid_ air, I was
naturally led to investigate the properties of it in the same manner,
and nearly in the same order. From this analogy I concluded, as I
presently found to be the fact, that this alkaline air would be readily
imbibed by water, and, by its union with it, would form a volatile
spirit of sal ammoniac. And as the water, when admitted to the air in
this manner, confined by quicksilver, has an opportunity of fully
saturating itself with the alkaline vapour, it is made prodigiously
stronger than any volatile spirit of sal ammoniac that I have ever seen;
and I believe stronger than it can be made in the common way.
In order to ascertain what addition, with respect to quantity and
weight, water would acquire by being saturated with alkaline air, I put
1-1/4 grains of rain-water into a small glass tube, closed at one end
with cement, and open at the other, the column of water measuring 7/10
of an inch; and having introduced it through the quicksilver into a
vessel containing alkaline air, observed that it absorbed 7/8 of an
ounce measure of the _air_, and had then gained about half a grain in
weight, and was increased to 8-1/2 tenths of an inch in length. I did
not make a second experiment of this kind, and therefore will not answer
for the exactness of these proportions in future trials. What I did
sufficiently answered my purpose, in a general view of the subject.
When I had, at one time, saturated a quantity of distilled water with
alkaline air, so that a good deal of the air remained unabsorbed on the
surface of the water, I observed that, as I continued to throw up more
air, a considerable proportion of it was imbibed, but not the whole; and
when I had let the apparatus stand a day, much more of the air that lay
on the surface was imbibed. And after the water would imbibe no more of
the _old_ air, it imbibed _new_. This shews that water requires a
considerable time to saturate itself with this kind of air, and that
part of it more readily unites with water than the rest.
The same is also, probably, the case with all the kinds of air with
which water can be impregnated. Mr. Cavendish made this observation with
respect to fixed air, and I repeated the whole process above-mentioned
with acid air, and had precisely the same result. The alkaline water
which I procured in this experiment was, beyond comparison, stronger to
the smell, than any spirit of sal ammoniac that I had seen.
This experiment led me to attempt the making of spirit of sal ammoniac
in a larger quantity, by impregnating distilled water with this alkaline
air. For this purpose I filled a piece of a gun-barrel with the
materials above-mentioned, and luted to the open end of it a small glass
tube, one end of which was bent, and put within the mouth of a glass
vessel, containing a quantity of distilled water upon quicksilver,
standing in a bason of quicksilver, as in fig. 7. In these circumstances
the heat of the fire, applied gradually, expelled the alkaline air,
which, passing through the tube, and the quicksilver, came at last to
the water, which, in time, became fully saturated with it.
By this means I got a very strong alkaline liquor, from which I could
again expel the alkaline air which I had put into it, whenever it
happened to be more convenient to me to get it in that manner. This
process may easily be performed in a still larger way; and by this means
a liquor of the same nature with the volatile spirit of sal ammoniac,
might be made much stronger, and much cheaper, than it is now made.
Having satisfied myself with respect to the relation that alkaline air
bears to water, I was impatient to find what would be the consequence
of mixing this new air with the other kinds with which I was acquainted
before, and especially with _acid_ air; having a notion that these two
airs, being of opposite natures, might compose a _neutral air_, and
perhaps the very same thing with common air. But the moment that these
two kinds of air came into contact, a beautiful white cloud was formed,
and presently filled the whole vessel in which they were contained. At
the same time the quantity of air began to diminish, and, at length,
when the cloud was subsided, there appeared to be formed a solid _while
salt_, which was found to be the common _sal ammoniac_, or the marine
acid united to the volatile alkali.
The first quantity that I produced immediately deliquesced, upon being
exposed to the common air; but if it was exposed in a very dry and warm
place, it almost all evaporated, in a white cloud. I have, however,
since, from the same materials, produced the salt above-mentioned in a
state not subject to deliquesce or evaporate. This difference, I find,
is owing to the proportion of the two kinds of air in the compound. It
is only volatile when there is more than a due proportion of either of
the constituent parts. In these cases the smell of the salts is
extremely pungent, but very different from one another; being manifestly
acid, or alkaline, according to the prevalence of each of these airs
respectively.
_Nitrous air_ admitted to alkaline air likewise occasioned a whitish
cloud, and part of the air was absorbed; but it presently grew clear
again; leaving only a little dimness on the sides of the vessel. This,
however, might be a kind of salt, formed by the union of the two kinds
of air. There was no other salt formed that I could perceive. Water
being admitted to this mixture of nitrous and alkaline air presently
absorbed the latter, and left the former possessed of its peculiar
properties.
_Fixed air_ admitted to alkaline air formed oblong and slender crystals,
which crossed one another, and covered the sides of the vessel in the
form of net-work. These crystals must be the same thing with the
volatile alkalis which chemists get in a solid form, by the distillation
of sal ammoniac with fixed alkaline salts.
_Inflammable air_ admitted to alkaline air exhibited no particular
appearance. Water, as in the former experiment, absorbed the alkaline
air, and left the inflammable air as it was before. It was remarkable,
however, that the water which was admitted to them became whitish, and
that this white cloud settled, in the form of a white powder, to the
bottom of the vessel.
Alkaline air mixed with _common air_, and standing together several
days, first in quicksilver, and then in water (which absorbed the
alkaline air) it did not appear that there was any change produced in
the common air: at least it was as much diminished by nitrous air as
before. The same was the case with a mixture of acid air and common air.
Having mixed air that had been diminished by the fermentation of a
mixture of iron filings and brimstone with alkaline air, the water
absorbed the latter, but left the former, with respect to the test of
nitrous air (and therefore, as I conclude, with respect to all its
properties) the same that it was before.
_Spirit of wine_ imbibes alkaline air as readily as water, and seems to
be as inflammable afterwards as before.
Alkaline air contracts no union with _olive oil_. They were in contact
almost two days, without any diminution of the air. Oil of turpentine,
and essential oil of mint, absorbed a very small quantity of alkaline
air, but were not sensibly changed by it.
_Ether_, however, imbibed alkaline air pretty freely; but it was
afterwards as inflammable as before, and the colour was not changed. It
also evaporated as before, but I did not attend to this last
circumstance very accurately.
_Sulphur_, _nitre_, _common salt_, and _flints_, were put to alkaline
air without imbibing any part of it; but _charcoal_, _spunge_, bits of
_linen cloth_, and other substances of that nature, seemed to condense
this air upon their surfaces; for it began to diminish immediately upon
their being put to it; and when they were taken out the alkaline smell
they had contracted was so pungent as to be almost intolerable,
especially that of the spunge. Perhaps it might be of use to recover
persons from swooning. A bit of spunge, about as big as a hazel nut,
presently imbibed an ounce measure of alkaline air.
A piece of the inspissated juice of _turnsole_ was made very dry and
warm, and yet it imbibed a great quantity of the air; by which it
contracted a most pungent smell, but the colour of it was not changed.
_Alum_ undergoes a very remarkable change by the action of alkaline air.
The outward shape and size remain the same, but the internal structure
is quite changed, becoming opaque, beautifully white, and, to
appearance, in all respects, like alum which had been roasted; and so as
not to be at all affected by a degree of heat that would have reduced it
to that state by roasting. This effect is produced slowly; and if a
piece of alum be taken out of alkaline air before the operation is over,
the inside will be transparent, and the outside, to an equal thickness,
will be a white crust.
I imagine that the alkaline vapour seizes upon the water that enters
into the constitution of crude alum, and which would have been expelled
by heat. Roasted alum also imbibes alkaline air, and, like the raw alum
that has been exposed to it, acquires a taste that is peculiarly
disagreeable.
_Phosphorus_ gave no light in alkaline air, and made no lasting change
in its dimensions. It varied, indeed, a little, being sometimes
increased and sometimes diminished, but after a day and a night, it was
in the same state as at the first. Water absorbed this air just as if
nothing had been put to it.
Having put some _spirit of salt_ to alkaline air, the air was presently
absorbed, and a little of the white salt above-mentioned was formed. A
little remained unabsorbed, and transparent, but upon the admission of
common air to it, it instantly became white.
_Oil of vitriol_, also formed a white salt with alkaline air, and this
did not rise in white fumes.
Acid air, as I have observed in my former papers, extinguishes a candle.
Alkaline air, on the contrary, I was surprized to find, is slightly
inflammable; which, however, seems to confirm the opinion of chemists,
that the volatile alkali contains phlogiston.
I dipped a lighted candle into a tall cylindrical vessel, filled with
alkaline air, when it went out three or four times successively; but at
each time the flame was considerably enlarged, by the addition of
another flame, of a pale yellow colour; and at the last time this light
flame descended from the top of the vessel to the bottom. At another
time, upon presenting a lighted candle to the mouth of the same vessel,
filled with the same kind of air, the yellowish flame ascended two
inches higher than the flame of the candle. The electric spark taken in
alkaline air is red, as it is in common inflammable air.
Though alkaline air be inflammable, it appeared, by the following
experiment, to be heavier than the common inflammable air, as well as to
contract no union with it. Into a vessel containing a quantity of
inflammable air, I put half as much alkaline air, and then about the
same quantity of acid air. These immediately formed a white cloud, but
it did not rise within the space that was occupied by the inflammable
air; so that this latter had kept its place above the alkaline air, and
had not mixed with it.
That alkaline air is lighter than acid air is evident from the
appearances that attend the mixture, which are indeed very beautiful.
When acid air is introduced into a vessel containing alkaline air, the
white cloud which they form appears at the bottom only, and ascends
gradually. But when the alkaline air is put to the acid, the whole
becomes immediately cloudy, quite to the top of the vessel.
In the last place, I shall observe that alkaline air, as well as acid,
dissolves _ice_ as fast as a hot fire can do it. This was tried when
both the kinds of air, and every instrument made use of in the
experiment, had been exposed to a pretty intense frost several hours. In
both cases, also, the water into which the ice was melted dissolved more
ice, to a considerable quantity.
SECTION II.
_Of COMMON AIR diminished and made noxious by various processes._
It will have been observed that, in the first publication of my papers,
I confined myself chiefly to the narration of the new _facts_ which I
had discovered, barely mentioning any _hypotheses_ that occurred to me,
and never seeming to lay much stress upon them. The reason why I was so
much upon my guard in this respect was, left, in consequence of
attaching myself to any hypothesis too soon, the success of my future
inquiries might be obstructed. But subsequent experiments having thrown
great light upon the preceding ones and having confirmed the few
conjectures I then advanced, I may now venture to speak of my hypotheses
with a little less diffidence. Still, however, I shall be ready to
relinquish any notions I may now entertain, if new facts should
hereafter appear not to favour them.
In a great variety of cases I have observed that there is a remarkable
_diminution_ of common, or respirable air, in proportion to which it is
always rendered unfit for respiration, indisposed to effervesce with
nitrous air, and incapable of farther diminution from any other cause.
The circumstances which produce this effect I had then observed to be
the burning of candles, the respiration of animals, the putrefaction of
vegetables or animal substances, the effervescence of iron filings and
brimstone, the calcination of metals, the fumes of charcoal, the
effluvia of paint made of white-lead and oil, and a mixture of nitrous
air.
All these processes, I observed, agree in this one circumstance, and I
believe in no other, that the principle which the chemists call
_phlogiston_ is set loose; and therefore I concluded that the diminution
of the air was, in some way or other, the consequence of the air
becoming overcharged with phlogiston,[11] and that water, and growing
vegetables, tend to restore this air to a state fit for respiration, by
imbibing the superfluous phlogiston. Several experiments which I have
since made tend to confirm this supposition.
Common air, I find, is diminished, and rendered noxious, by _liver of
sulphur_, which the chemists say exhales phlogiston, and nothing else.
The diminution in this case was one fifth of the whole, and afterwards,
as in other similar cases, it made no effervescence with nitrous air.
I found also, after Dr. Hales, that air is diminished by _Homberg's
pyrophorus_.
The same effect is produced by firing _gunpowder_ in air. This I tried
by firing the gunpowder in a receiver half exhausted, by which the air
was rather more injured than it would have been by candles burning in
it.
Air is diminished by a cement made with one half common coarse
turpentine and half bees-wax. This was the result of a very casual
observation. Having, in an air-pump of Mr. Smeaton's construction,
closed that end of the syphon-gage, which is exposed to the outward air,
with this cement (which I knew would make it perfectly air-light)
instead of sealing it hermetically; I observed that, in a course of
time, the quicksilver in that leg kept continually rising, so that the
measures I marked upon it were of no use to me; and when I opened that
end of the tube, and closed it again, the same consequence always took
place. At length, suspecting that this effect must have arisen from the
bit of _cement_ diminishing the air to which it was exposed, I covered
all the inside of a glass tube with it, and one end of it being quite
closed with the cement, I set it perpendicular, with its open end
immersed in a bason of quicksilver; and was presently satisfied that my
conjecture was well founded: for, in a few days, the quicksilver rose so
much within the tube, that the air in the inside appeared to be
diminished about one sixth.
To change this air I filled the tube with quicksilver, and pouring it
out again, I replaced the tube in its former situation; when the air was
diminished again, but not so fast as before. The same lining of cement
diminished the air a third time. How long it will retain this power I
cannot tell. This cement had been made several months before I made
this experiment with it. I must observe, however, that another quantity
of this kind of cement, made with a finer and more liquid turpentine,
had not the power of diminishing air, except in a very small proportion.
Also the common red cement has this property in the same small degree.
Common air, however, which had been confined in a glass vessel lined
with this cement about a month, was so far injured that a candle would
not burn in it. In a longer time it would, I doubt not, have become
thoroughly noxious.
Iron that has been suffered to rust in nitrous air diminishes common air
very fast, as I shall have occasion to mention when I give a
continuation of my experiments on nitrous air.
Lastly, the same effect, I find, is produced by the _electric spark_,
though I had no expectation of this event when I made the experiment.
This experiment, however, and those which I have made in pursuance of
it, has fully confirmed another of my conjectures, which relates to the
_manner_ in which air is diminished by being overcharged with
phlogiston, viz. the phlogiston having a nearer affinity with some of
the constituent parts of the air than the fixed air which enters into
the composition of it, in consequence of which the fixed air is
precipitated.
This I first imagined from perceiving that lime-water became turbid by
burning candles over it, p. 44. This was also the case with lime-water
confined in air in which an animal substance was putrefying, or in which
an animal died, p. 79. and that in which charcoal was burned, p. 81.
But, in all these cases, there was a possibility of the fixed air being
discharged from the candle, the putrefying substance, the lungs of the
animal, or the charcoal. That there is a precipitation of lime when
nitrous air is mixed with common air, I had not then observed, but I
have since found it to be the case.
That there was no precipitation of lime when brimstone was burned, I
observed, p. 45. might be owing to the fixed air and the lime uniting
with the vitriolic acid, and making a salt, which was soluble in water;
which salt I, indeed, discovered by the evaporation of the water.
I also observed, p. 46, 105. that diminished air being rather lighter
than common air is a circumstance in favour of the fixed, or the
heavier part of the common air, having been precipitated.
It was upon this idea, together with others similar to it, that I took
so much pains to mix fixed air with air diminished by respiration or
putrefaction, in order to make it fit for respiration again; and I
thought that I had, in general, succeeded to a considerable degree, p.
99, &c. I will add, also, what I did not mention before, that I once
endeavoured, but without effect, to preserve mice alive in the same
unchanged air, by supplying them with fixed air, when the air in which
they were confined began to be injured by their respiration. Without
effect, also, I confined for some months, a quantity of quick lime in a
given quantity of common air, thinking it might extract the fixed air
from it.
The experiments which I made with electricity were solely intended to
ascertain what has often been attempted, but, as far as I know, had
never been fully accomplished, viz. to change the blue colour of
liquors, tinged with vegetable juices, red.
For this purpose I made use of a glass tube, about one tenth of an inch
diameter in the inside, as in fig. 16. In one end of this I cemented a
piece of wire _b_, on which I put a brass ball. The lower part from _a_
was filled with water tinged blue, or rather purple, with the juice of
turnsole, or archil. This is easily done by an air-pump, the tube being
set in a vessel of the tinged water.
Things being thus prepared, I perceived that, after I had taken the
electric spark, between the wire _b_, and the liquor at _a_, about a
minute, the upper part of it began to look red, and in about two minutes
it was very manifestly so; and the red part, which was about a quarter
of an inch in length, did not readily mix with the rest of the liquor. I
observed also, that if the tube lay inclined while I took the sparks,
the redness extended twice as far on the lower side as on the upper.
The most important, though the least expected observation, however, was
that, in proportion as the liquor became red, it advanced nearer to the
wire, so that the space of air in which the sparks were taken was
diminished; and at length I found that the diminution was about one
fifth of the whole space; after which more electrifying produced no
sensible effect.
To determine whether the cause of the change of colour was in the _air_,
or in the _electric matter_, I expanded the air which had been
diminished in the tube by means of an air-pump, till it expelled all the
liquor, and admitted fresh blue liquor into its place; but after that,
electricity produced no sensible effect, either on the air, or on the
liquor; so that it was evident that the electric matter had decomposed
the air, and had made it deposite something that was of an acid nature.
In order to determine whether the _wire_ had contributed any thing to
this effect, I used wires of different metals, iron, copper, brass, and
silver; but the result was the very same with them all.
It was also the same when, by means of a bent glass tube, I made the
electric spark without any wire at all, in the following manner. Each
leg of the tube, fig. 19. stood in a bason of quicksilver; which, by
means of an air-pump, was made to ascend as high as _a, a_, in each leg,
while the space between _a_ and _b_ in each contained the blue liquor,
and the space between _b_ and _b_ contained common air. Things being
thus disposed, I made the electric spark perform the circuit from one
leg to the other, passing from the liquor in one leg of the tube to the
liquor in the other leg, through the space of air. The effect was, that
the liquor, in both the legs, became red, and the space of air between
them was contracted, as before.
Air thus diminished by electricity makes no effervescence with, and is
no farther diminished by a mixture of nitrous air; so that it must have
been in the highest degree noxious, exactly like air diminished by any
other process.
In order to determine what the _acid_ was, which was deposited by the
air, and which changed the colour of the blue liquor, I exposed a small
quantity of the liquor so changed to the common air, and found that it
recovered its blue colour, exactly as water, tinged with the same blue,
and impregnated with fixed air, will do. But the following experiment
was still more decisive to this purpose. Taking the electric spark upon
_lime-water_, instead of the blue liquor, the lime was precipitated as
the air diminished.
From these experiments it pretty clearly follows, that the electric
matter either is, or contains phlogiston; since it does the very same
thing that phlogiston does. It is also probable, from these experiments,
that the sulphureous smell, which is occasioned by electricity, being
very different from that of fixed air, the phlogiston in the electric
matter itself may contribute to it.
It was now evident that common air diminished by any one of the
processes above-mentioned being the same thing, as I have observed, with
air diminished by any other of them (since it is not liable to be
farther diminished by any other) the loss which it sustains, in all the
cases, is, in part, that of the _fixed air_ which entered into its
constitution. The fixed air thus precipitated from common air by means
of phlogiston unites with lime, if any lime water be ready to receive
it, unless there be some other substance at hand, with which it has a
greater affinity, as the _calces of metals_.
If the whole of the diminution of common air was produced by the
deposition of fixed air, it would be easy to ascertain the quantity of
fixed air that is contained in any given quantity of common air. But it
is evident that the whole of the diminution of common air by phlogiston
is not owing to the precipitation of fixed air, because a mixture of
nitrous air will make a great diminution in all kinds of air that are
fit for respiration, even though they never were common air, and though
nothing was used in the process for generating them that can be supposed
to yield fixed air.
Indeed, it appears, from some of the experiments, that the diminution of
some of these kinds of air by nitrous air is so great, and approaches so
nearly to the quantity of the diminution of common air by the same
process, as to shew that, unless they be very differently affected by
phlogiston, very little is to be allowed to the loss of fixed air in the
diminution of common air by nitrous air.
The kinds of air on which this experiment was made were inflammable air,
nitrous air diminished by iron filings and brimstone, and nitrous air
itself; all of which are produced by the solution of metals in acids;
and also on common air diminished and made noxious, and therefore
deprived of its fixed air by phlogistic processes; and they were
restored to a great degree of purity by agitation in water, out of which
its own air had been carefully boiled.
To five parts of inflammable air, which had been agitated in water till
it was diminished about one half (at which time part of it fired with a
weak explosion) I put one part of nitrous air, which diminished it one
eighth of the whole. This was done in lime-water, without any
precipitation of lime. To compare this with common air, I mixed the same
quantity, viz. five parts of this, and one part of nitrous air: when
considerable crust of lime was formed upon the surface of the lime
water, though the diminution was very little more than in the former
process. It is possible, however, that the common air might have taken
more nitrous air before it was fully saturated, so as to begin to
receive an addition to its bulk.
I agitated in water a quantity of nitrous air phlogisticated with iron
filings and brimstone, and found it to be so far restored, that three
fourths of an ounce measure of nitrous air being put to two ounce
measures of it, made no addition to it.
But the most remarkable of these experiments is that which I made with
_nitrous air_ itself which I had no idea of the possibility of reducing
to a state fit for respiration by any process whatever, at the time of
my former publication on this subject. This air, however, itself,
without any previous phlogistication, is purified by agitation in water
till it is diminished by fresh nitrous air, and to a very considerable
degree.
In a pretty long time I agitated nitrous air in water, supplying it from
time to time with more, as the former quantity diminished, till only one
eighteenth of the whole quantity remained; in which state it was so
wholesome, that a mouse lived in two ounce measures of it more than ten
minutes, without shewing any sign of uneasiness; so that I concluded it
must have been about as good as air in which candles had burned out.
After agitating it again in water, I put one part of fresh nitrous air
to five parts of this air, and it was diminished one ninth part. I then
agitated it a third time, and putting more nitrous air to it, it was
diminished again in the same proportion, and so a fourth time; so that,
by continually repeating the process, it would, I doubt not, have been
all absorbed. These processes were made in lime-water, without forming
any incrustation on the surface of it.
Lastly, I took a quantity of common air, which had been diminished and
made noxious by phlogistic processes; and when it had been agitated in
water, I found that it was diminished by nitrous air, though not so much
as it would have been at the first. After cleansing it a second time, it
was diminished again by the same means; and, after that, a third time;
and thus there can be no doubt but that, in time, the whole quantity
would have disappeared. For I have never found that agitation in water,
deprived of its own air, made any addition to a quantity of noxious air;
though, _a priori_, it might have been imagined that, as a saturation
with phlogiston diminishes air, the extraction of phlogiston would
increase the bulk of it. On the contrary, agitation in water always
diminished noxious air a little; indeed, if water be deprived of all its
own air, it is impossible to agitate any kind of air in it without some
loss. Also, when noxious air has been restored by plants, I never
perceived that it gained any addition to its bulk by that means. There
was no incrustation of the lime-water in the above-mentioned experiment.
It is not a little remarkable, that those kinds of air which never had
been common air, as inflammable air, phlogisticated nitrous air, and
nitrous air itself, when rendered wholesome by agitation in water,
should be more diminished by fresh nitrous air, than common air which
had been made noxious, and restored by the same process; and yet, from
the few trials that I have made, I could not help concluding that this
is the case.
In this course of experiments I was very near deceiving myself, in
consequence of transferring the nitrous air which I made use of in a
bladder, in the manner described, p. 15. fig. 9. so as to conclude that
there was a precipitation of lime in all the above-mentioned cases, and
that even nitrous air itself produced that effect. But after repeated
trials, I found that there was no precipitation of lime, except, in the
first diminution of common air, when the nitrous air was transferred in
a glass vessel.
That the calces of metals contain air, of some kind or other, and that
this air contributes to the additional weight of the calces, above that
of the metals from which they are made, had been observed by Dr. Hales;
and Mr. Hartley had informed me, that when red-lead is boiled in linseed
oil, there is a prodigious discharge of air before they incorporate. I
had likewise found, that no weight is either gained or lost by the
calcination of tin in a close glass vessel; but I purposely deferred
making any more experiments on the subject, till we should have some
weather in which I could make use of a large burning lens, which I had
provided for that and other purposes; but, in the mean time, I was led
to the discovery in a different manner.
Having, by the last-recited experiments, been led to consider the
electric matter as phlogiston, or something containing phlogiston, I was
endeavouring to revivify the calx of lead with it; when I was surprized
to perceive a considerable generation of air. It occurred to me, that
possibly this effect might arise from the _heat_ communicated to the
red-lead by the electric sparks, and therefore I immediately filled a
small phial with the red-lead, and heating it with a candle, I presently
expelled from it a quantity of air about four or five times the bulk of
the lead, the air being received in a vessel of quicksilver. How much
more air it would have yielded, I did not try.
Along with the air, a small quantity of _water_ was likewise thrown out;
and it immediately occurred to me, that this water and air together must
certainly be the cause of the addition of weight in the calx. It still
remained to examine what kind of air this was; but admitting water to
it, I found that it was imbibed by it, exactly like _fixed air_, which I
therefore immediately concluded it must be[12].
After this, I found that Mr. Lavoisier had completely discovered the
same thing, though his apparatus being more complex, and less accurate
than mine, he concluded that more of the air discharged from the calces
of metals was immiscible with water than I found it to be. It appeared
to me that I had never obtained fixed air more pure.
It being now pretty clearly determined, that common air is made to
deposit the fixed air which entered into the constitution of it, by
means of phlogiston, in all the cases of diminished air, it will follow,
that in the precipitation of lime, by breathing into lime-water the
fixed air, which incorporates with lime, comes not from the lungs, but
from the common air, decomposed by the phlogiston exhaled from them, and
discharged, after having been taken in with the aliment, and having
performed its function in the animal system.
Thus my conjecture is more confirmed, that the cause of the death of
animals in confined air is not owing to the want of any _pabulum vitae_,
which the air had been supposed to contain, but to the want of a
discharge of the phlogistic matter, with which the system was loaded;
the air, when once saturated with it, being no sufficient _menstruum_ to
take it up.
The instantaneous death of animals put into air so vitiated, I still
think is owing to some _stimulus_, which, by causing immediate,
universal and violent convulsions, exhausts the whole of the _vis vitae_
at once; because, as I have observed, the manner of their death is the
very same in all the different kinds of noxious air.
To this section on the subject of diminished, and noxious air, or as it
might have been called _phlogisticated air_, I shall subjoin a letter
which I addressed to Sir John Pringle, on the noxious quality of the
effluvia of putrid marshes, and which was read at a meeting of the Royal
Society, December 16, 1773.
This letter which is printed in the Philosophical Transactions, Vol. 74,
p. 90. is immediately followed by another paper, to which I would refer
my reader. It was written by Dr. Price, who has so greatly distinguished
himself, and done such eminent service to his country, and to mankind,
by his calculations relating to the probabilities of human life, and was
suggested by his hearing this letter read at the Royal Society. It
contains a confirmation of my observations on the noxious effects of
stagnant waters by deductions from Mr. Muret's account of the Bills of
Mortality for a parish situated among marshes, in the district of Vaud,
belonging to the Canton of Bern in Switzerland.
To Sir JOHN PRINGLE, Baronet.
DEAR SIR,
Having pursued my experiments on different kinds of air considerably
farther, in several respects, than I had done when I presented the last
account of them to the Royal Society; and being encouraged by the
favourable notice which the Society has been pleased to take of them, I
shall continue my communications on this subject; but, without waiting
for the result of a variety of processes, which I have now going on, or
of other experiments, which I propose to make, I shall, from time to
time, communicate such detached articles, as I shall have given the most
attention to, and with respect to which, I shall have been the most
successful in my inquiries.
Since the publication of my papers, I have read two treatises, written
by Dr. Alexander, of Edinburgh, and am exceedingly pleased with the
spirit of philosophical inquiry, which they discover. They appear to me
to contain many new, curious, and valuable observations; but one of the
_conclusions_, which he draws from his experiments, I am satisfied, from
my own observations, is ill founded, and from the nature of it, must be
dangerous. I mean his maintaining, that there is nothing to be
apprehended from the neighbourhood of putrid marshes.
I was particularly surprised, to meet with such an opinion as this, in a
book inscribed to yourself, who have so clearly explained the great
mischief of such a situation, in your excellent treatise _on the
diseases of the army_. On this account, I have thought it not improper,
to address to you the following observations and experiments, which I
think clearly demonstrate the fallacy of Dr. Alexander's reasoning,
indisputably establish your doctrine, and indeed justify the
apprehensions of all mankind in this case.
I think it probable enough, that putrid matter, as Dr. Alexander has
endeavoured to prove, will preserve other substances from putrefaction;
because, being already saturated with the putrid effluvium, it cannot
readily take any more; but Dr. Alexander was not aware, that air thus
loaded with putrid effluvium is exceedingly noxious when taken into the
lungs. I have lately, however, had an opportunity of fully ascertaining
how very noxious such air is.
Happening to use at Calne, a much larger trough of water, for the
purpose of my experiments, than I had done at Leeds, and not having
fresh water so near at hand as I had there, I neglected to change it,
till it turned black, and became offensive, but by no means to such a
degree, as to deter me from making use of it. In this state of the
water, I observed bubbles of air to rise from it, and especially in one
place, to which some shelves, that I had in it, directed them; and
having set an inverted glass vessel to catch them, in a few days I
collected, a considerable quantity of this air, which issued
spontaneously from the putrid water; and putting nitrous air to it, I
found that no change of colour or diminution ensued, so that it must
have been, in the highest degree, noxious. I repeated the same
experiment several times afterwards, and always with the same result.
After this, I had the curiosity to try how wholesome air would be
affected by this water; when, to my real surprise, I found, that after
only one minute's agitation in it, a candle would not burn in it; and,
after three or four minutes, it was in the same state with the air,
which had issued spontaneously from the same water.
I also found, that common air, confined in a glass vessel, in _contact_
only with this water, and without any agitation, would not admit a
candle to burn in it after two days.
These facts certainly demonstrate, that air which either arises from
stagnant and putrid water, or which has been for some time in contact
with it, must be very unfit for respiration; and yet Dr. Alexander's
opinion is rendered so plausible by his experiments, that it is very
possible that many persons may be rendered secure, and thoughtless of
danger, in a situation in which they must necessarily breathe it. On
this account, I have thought it right to make this communication as
early as I conveniently could; and as Dr. Alexander appears to be an
ingenuous and benevolent man, I doubt not but he will thank me for it.
That air issuing from water, or rather from the soft earth, or mud, at
the bottom of pits containing water, is not always unwholesome, I have
also had an opportunity of ascertaining. Taking a walk, about two years
ago, in the neighbourhood of Wakefield, in Yorkshire, I observed bubbles
of air to arise, in remarkably great plenty, from a small pool of water,
which, upon inquiry, I was informed had been the place, where some
persons had been boring the ground, in order to find coal. These
bubbles of air having excited my curiosity, I presently returned, with a
bason, and other vessels proper for my purpose, and having stirred the
mud with a long stick, I soon got about a pint of this air; and,
examining it, found it to be good, common air; at least a candle burned
in it very well. I had not then discovered the method of ascertaining
the goodness of common air, by a mixture of nitrous air. Previous to the
trial, I had suspected that this air would have been found to be
inflammable.
I shall conclude this letter with observing, that I have found a
remarkable difference in different kinds of water, with respect to their
effect on common air agitated in them, and which I am not yet able to
account for. If I agitate common air in the water of a deep well, near
my house in Calne, which is hard, but clear and sweet, a candle will not
burn in it after three minutes. The same is the case with the
rain-water, which I get from the roof of my house. But in distilled
water, or the water of a spring-well near the house, I must agitate the
air about twenty minutes, before it will be so much injured. It may be
worth while, to make farther experiments with respect to this property
of water.
In consequence of using the rain-water, and the well-water above
mentioned, I was very near concluding, contrary to what I have asserted
in this treatise, that common air suffers a decomposition by great
rarefaction. For when I had collected a considerable quantity of air,
which had been rarefied about four hundred times, by an excellent pump
made for me by Mr. Smeaton, I always found, that if I filled my
receivers with the water above mentioned, though I did it so gradually
as to occasion as little agitation as possible, a candle would not burn
in the air that remained in them. But when I used distilled water, or
fresh spring-water, I undeceived myself.
I think myself honoured by the attention, which, from the first, you
have given to my experiments, and am, with the greatest respect,
Dear Sir,
Your most obliged
Humble Servant,
London, 7 Dec. 1773.
J. PRIESTLEY.
POSTSCRIPT.
I cannot help expressing my surprize, that so clear and intelligible an
account, of Mr. SMEATON'S air-pump, should have been before the public
so long, as ever since the publication of the forty-seventh volume of
the Philosophical Transactions, printed in 1752, and yet that none of
our philosophical instrument-makers should use the construction. The
superiority of this pump, to any that are made upon the common plan, is,
indeed, prodigious. Few of them will rarefy more than 100 times, and, in
a general way, not more than 60 or 70 times; whereas this instrument
must be in a poor state indeed, if it does not rarefy 200 or 300 times;
and when it is in good order, it will go as far as 1000 times, and
sometimes even much farther than that; besides, this instrument is
worked with much more ease, than a common air-pump, and either exhausts
or condenses at pleasure. In short, to a person engaged in philosophical
pursuits, this instrument is an invaluable acquisition. I shall have
occasion to recite some experiments, which I could not have made, and
which, indeed, I should hardly have dared to attempt, if I had not been
possessed of such an air-pump as this. It is much to be wished, that
some person of spirit in the trade would attempt the construction of an
instrument, which would do great credit to himself, as well as be of
eminent service to philosophy.
FOOTNOTES:
[11] On this account, if it was thought convenient to introduce a new
term (or rather make a new application of a term already in use among
chemists) it might not be amiss to call air that has been diminished,
and made noxious by any of the processes above mentioned, or others
similar to them, by the common appellation of _phlogisticated air_; and,
if it was necessary, the particular process by which it was
phlogisticated might be added; as common air phlogisticated by charcoal,
air phlogisticated by the calcination of metals, nitrous air
phlogisticated with the liver of sulphur, &c.
[12] Here it becomes me to ask pardon of that excellent philosopher
Father Beccaria of Turin, for conjecturing that the phlogiston, with
which he revivified metals, did not come from the electric matter
itself, but from what was discharged from other pieces of metal with
which he made the experiment. See History of Electricity, p. 277, &c.
This _revivification of metals_ by electricity completes the proof of
the electric matter being, or containing phlogiston.
SECTION III.
_Of NITROUS AIR._
Since the publication of my former papers I have given more attention to
the subject of nitrous air than to any other species of air; and having
been pretty fortunate in my inquiries, I shall be able to lay before my
reader a more satisfactory account of the curious phenomena occasioned
by it, and also of its nature and constitution, than I could do before,
though much still remains to be investigated concerning it, and many new
objects of inquiry are started.
With a view to discover where the power of nitrous air to diminish
common air lay, I evaporated to dryness a quantity of the solution of
copper in diluted spirit of nitre; and having procured from it a
quantity of a _green precipitate_, I threw the focus of a burning-glass
upon it, when it was put into a vessel of quicksilver, standing inverted
in a bason of quicksilver. In this manner I procured air from it, which
appeared to be, in all respects, nitrous air; so that part of the same
principle which had escaped during the solution, in the form of _air_,
had likewise been retained in it, and had not left it in the evaporation
of the water.
With great difficulty I also procured a small quantity of the same kind
of air from a solution of _iron_ in spirit of nitre, by the same
process.
Having, for a different purpose, fired some paper, which had been dipped
in a solution of copper in diluted spirit of nitre, in nitrous air, I
found there was a considerable addition to the quantity of it; upon
which I fired some of the same kind of paper in quicksilver and
presently observed that air was produced from it in great plenty. This
air, at the first, seemed to have some singular properties, but
afterwards I found that it was nothing more than a mixture of nitrous
air, from the precipitate of the solution, and of inflammable air, from
the paper; but that the former was predominant.
In the mixture of this kind of air with common air, in a trough of water
which had been putrid, but which at that time seemed to have recovered
its former sweetness (for it was not in the least degree offensive to
the smell) a phenomenon sometimes occurred, which for a long time
exceedingly delighted and puzzled me; but which was afterwards the means
of letting me see much farther into the constitution of nitrous air than
I had been able to see before.
When the diminution of the air was nearly completed, the vessel in which
the mixture was made began to be filled with the most beautiful _white
fumes_, exactly resembling the precipitation of some white substance in
a transparent menstruum, or the falling of very fine snow; except that
it was much thicker below than above, as indeed is the case in all
chemical precipitations. This appearance continued two or three minutes.
At other times I went over the same process, as nearly as possible in
the same manner, but without getting this remarkable appearance, and was
several times greatly disappointed and chagrined, when I baulked the
expectations of my friends, to whom I had described, and meant to have
shewn it. This made me give all the attention I possibly could to this
experiment, endeavouring to recollect every circumstance, which, though
unsuspected at the time, might have contributed to produce this new
appearance; and I took a great deal of pains to procure a quantity of
this air from the paper above mentioned for the purpose, which, with a
small burning lens, and an uncertain sun, is not a little troublesome.
But all that I observed for some time was, that I stood the best chance
of succeeding when I _warmed_ the vessel in which the mixture was made,
and _agitated_ the air during the effervescence.
Finding, at length, that, with the same preparation and attentions, I
got the same appearance from a mixture of nitrous and common air in the
same trough of water, I concluded that it could not depend upon any
thing peculiar to the precipitate of the _copper_ contained in the
_paper_ from which the air was procured, as I had at first imagined, but
upon what was common to it, and pure nitrous air.
Afterwards, having, (with a view to observe whether any crystals would
be formed by the union of volatile alkali, and nitrous air, similar to
those formed by it and fixed air, as described by Mr. Smeth in his
_Dissertation on fixed Air_) opened the mouth of a phial which was half
filled with a volatile alkaline liquor, in a jar of nitrous air (in the
manner described p. 11. fig. 4.) I had an appearance which perfectly
explained the preceding. All that part of the phial which was above the
liquor, and which contained common air, was filled with beautiful
_white clouds_, as if some fine white powder had been instantly thrown
into it, and some of these clouds rose within the jar of nitrous air.
This appearance continued about a minute, and then intirely disappeared,
the air becoming transparent.
Withdrawing the phial, and exposing it to the common air, it there also
became turbid, and soon after the transparency returned. Introducing it
again into the nitrous air, the clouds appeared as before. In this
manner the white fumes, and transparency, succeeded each other
alternately, as often as I chose to repeat the experiment, and would no
doubt have continued till the air in the jar had been thoroughly diluted
with common air. These appearances were the same with any substance that
contained _volatile alkali_, fluid or solid.
When, instead of the small phial, I used a large and tall glass jar,
this appearance was truly fine and striking, especially when the water
in the trough was very transparent. For I had only to put the smallest
drop of a volatile alkaline liquor, or the smallest bit of the solid
salt, into the jar, and the moment that the mouth of it was opened in a
jar of nitrous air, the white clouds above mentioned began to be formed
at the mouth, and presently descended to the bottom, so as to fill the
whole, were it ever so large, as with fine snow.
In considering this experiment, I soon perceived that this curious
appearance must have been occasioned by the mixture of the nitrous and
common air, and therefore that the white clouds must be _nitrous
ammoniac_, formed by the acid of the nitrous air, set loose in the
decomposition of it by common air, while the phlogiston, which must be
another constituent part of nitrous air, entering the common air, is the
cause of the diminution it suffers in this process; as it is the cause
of a similar diminution, in a variety of other processes.
I would observe, that it is not peculiar to nitrous air to be a test of
the fitness of air for respiration. Any other process by which air is
diminished and made noxious answers the same purpose. Liver of sulphur
for instance, the calcination of metals, or a mixture of iron filings
and brimstone will do just the same thing; but the application of them
is not so easy, or elegant, and the effect is not so soon perceived. In
fact, it is _phlogiston_ that is the test. If the air be so loaded with
this principle that it can take no more, which is seen by its not being
diminished in any of the processes above mentioned, it is noxious; and
it is wholesome in proportion to the quantity of phlogiston that it is
able to take.
This, I have no doubt, is the true theory of the diminution of common
air by nitrous air, the redness of the appearance being nothing more
than the usual colour of the fumes, of spirit of nitre, which is now
disengaged from the superabundant phlogiston with which it was combined
in the nitrous air, and ready to form another union with any thing that
is at hand, and capable of it.
With the volatile alkali it forms nitrous ammoniac, water imbibes it
like any other acid, even quicksilver is corroded by it; but this action
being slow, the redness in this mixture of nitrous and common air
continues much longer when the process is made in quicksilver, than when
it is made in water, and the diminution, as I have also observed; is by
no means so great.
I was confirmed in this opinion when I put a bit of volatile alkaline
salt into the jar of quicksilver in which I made the mixture of nitrous
and common air. In these circumstances, the vessel being previously
filled with the alkaline fumes, the acid immediately joined them, formed
the white clouds above mentioned, and the diminution proceeded almost
as far as when the process was made in water. That it did not proceed
quite so far, I attribute chiefly to the small quantity of calx formed
by the slight solution of mercury with the acid fumes not being able to
absorb all the fixed air that is precipitated from the common air by the
phlogiston.
In part, also, it may be owing to the small quantify of surface in the
quicksilver in the vessels that I made use of; in consequence of which
the acid fumes could act upon it only in a slow succession, so that part
of them, as well as of the fixed air, had an opportunity of forming
another union with the diminished air.
This, as I have observed before, was so much the case when the process
was made in quicksilver, without any volatile alkali, that when water
was admitted to it, after some time, it was not capable of dissolving
that union, tho' it would not have taken place if the process had been
in water from the first.
In diversifying this experiment, I found that it appeared to very great
advantage when I suspended a piece of volatile salt in the common air,
previous to the admission of nitrous air to it, inclosing it in a bit
of gauze, muslin, or a small net of wire. For, presently after the
redness of the mixture begins to go off, the white cloud, like snow,
begins to descend from the salt, as if a white powder was shaken out of
the bag that contains it. This white cloud presently fills the whole
vessel, and the appearance will last about five minutes.
If the salt be not put to the mixture of these two kinds of air till it
has perfectly recovered its transparency, the effervescence being
completely over, no white cloud will be formed; and, what is rather more
remarkable, there is nothing of this appearance when the salt is put
into the nitrous air itself. The reason of this must be, that the acid
of the nitrous air has a nearer affinity with its phlogiston than with
the volatile alkali; though the phlogiston having a nearer affinity with
something in the common air, the acid being thereby set loose, will
unite with the alkaline vapour, if it be at hand to unite with it.
There is also very little, if any white cloud formed upon holding a
piece of the volatile salt within the mouth of a phial containing
smoking spirit of nitre. Also when I threw the focus of a burning mirror
upon some sal ammoniac in nitrous air, and filled the whole vessel with
white fumes which arose from it, they were soon dispersed, and the air
was neither diminished nor altered.
I was now fully convinced, that the white cloud which I casually
observed, in the first of these experiments, was occasioned by the
volatile alkali emitted from the water, which was in a slight degree
putrid; and that the warming, and agitation of the vessels, had promoted
the emission of the putrid, or alkaline effluvium.
I could not perceive that the diminution of common air by the mixture of
nitrous air was sensibly increased by the presence of the volatile
alkali. It is possible, however, that, by assisting the water to take up
the acid, something less of it may be incorporated with the remaining
diminished air than would otherwise have been; but I did not give much
attention to this circumstance.
When the phial in which I put the alkaline salts contained any kind of
noxious air, the opening of it in nitrous air was not followed by any
thing of the appearance above mentioned. This was the case with
inflammable air. But when, after agitating the inflammable air in water,
I had brought it to a state in which it was diminished a little by the
mixture of nitrous air, the cloudy appearance was in the same
proportion; so that this appearance seems to be equally a test of the
fitness of air for respiration, with the redness which attends the
mixture of it with nitrous air only.
Having generally fastened the small bag which contained the volatile
salt to a piece of brass wire in the preceding experiment, I commonly
found the end of it corroded, and covered with a blue substance. Also
the salt itself, and sometimes the bag was died blue. But finding that
this was not the case when I used an iron wire in the same
circumstances, but that it became _red_, I was satisfied that both the
metals had been dissolved by the volatile alkali. At first I had a
suspicion that the blue might have come from the copper, out of which
the nitrous air had been made. But when the nitrous air was made from
iron, the appearances were, in all respects, the same.
I have observed, in the preceding section, that if nitrous air be mixed
with common air in _lime-water_, the surface of the water, where it is
contiguous to that mixture, will be covered with an incrustation of
lime, shewing that some fixed air had been deposited in the process. It
is remarkable, however, as I there also just mentioned, that this is
the case when nitrous air alone is put to a vessel of lime-water, after
it has been kept in a _bladder_, or only transferred from one vessel to
another by a bladder, in the manner described, p. 15. fig. 9.
As I had used the same bladder for transferring various kinds of air,
and among the rest _fixed air_, I first imagined that this effect might
have been occasioned by a mixture of this fixed air with the nitrous
air, and therefore took a fresh bladder; but still the effect was the
same. To satisfy myself farther, that the bladder had produced this
effect, I put one into a jar of nitrous air, and after it had continued
there a day and a night, I found that the nitrous air in this jar,
though it was transferred in a glass vessel, made lime-water turbid.
Whether there was any thing in the preparation of these bladders that
occasioned their producing this effect, I cannot tell. They were such as
I procure from the apothecaries. The thing seems to deserve farther
examination, as there seems, in this case, to be the peculiar effect of
fixed air from other causes, or else a production of fixed air from
materials that have not been supposed to yield it, at least not in
circumstances similar to these.
As fixed air united to water dissolves iron, I had the curiosity to try
whether fixed air alone would do it; and as nitrous air is of an _acid_
nature, as well as fixed air, I, at the same time, exposed a large
surface of iron to both the kinds; first filling two eight ounce phials
with nails, and then with quicksilver, and after that displacing the
quicksilver in one of the phials by fixed air, and in the other by
nitrous air; then inverting them, and leaving them with their mouths
immersed in basons of quicksilver.
In these circumstances the two phials stood about two months, when no
sensible change at all was produced in the fixed air, or in the iron
which had been exposed to it, but a most remarkable, and most unexpected
change was made in the nitrous air; and in pursuing the experiment, it
was transformed into a species of air, with properties which, at the
time of my first publication on this subject, I should not have
hesitated to pronounce impossible, viz. air in which a candle burns
quite naturally and freely, and which is yet in the highest degree
noxious to animals, insomuch that they die the moment they are put into
it; whereas, in general, animals live with little sensible inconvenience
in air in which candles have burned out. Such, however, is nitrous air,
after it has been long exposed to a large surface of iron.
It is not less extraordinary, that a still longer continuance of nitrous
air in these circumstances (but _how long_ depends upon too many, and
too minute circumstances to be ascertained with exactness) makes it not
only to admit a candle to burn in it, but enables it to burn with an
_enlarged flame_, by another flame (extending every where to an equal
distance from that of the candle, and often plainly distinguishable from
it) adhering to it. Sometimes I have perceived the flame of the candle,
in these circumstances, to be twice as large as it is naturally, and
sometimes not less than five or six times larger; and yet without any
thing like an _explosion_, as in the firing of the weakest inflammable
air.
Nor is the farther progress in the transmutation of nitrous air, in
these circumstances, less remarkable. For when it has been brought to
the state last mentioned, the agitation of it in fresh water almost
instantly takes off that peculiar kind of inflammability, so that it
extinguishes a candle, retaining its noxious quality. It also retains
its power of diminishing common air in a very great degree.
But this noxious quality, like the noxious quality of all other kinds of
air that will bear agitation in water, is taken out of it by this
operation, continued about five minutes; in which process it suffers a
farther and very considerable diminution. It is then itself diminished
by fresh nitrous air, and animals live in it very well, about as well as
in air in which candles have burned out.
Lastly, One quantity of nitrous air, which had been exposed to iron in
quicksilver, from December 18 to January 20, and which happened to stand
in water till January 31 (the iron still continuing in the phial) was
fired with an explosion, exactly like a weak inflammable air. At the
same time another quantity of nitrous air, which had likewise been
exposed to iron, standing in quicksilver, till about the same time, and
had then stood in water only, without iron, only admitted a candle to
burn in it with an enlarged flame, as in the cases above mentioned. But
whether the difference I have mentioned in the circumstances of these
experiments contributed to this difference in the result, I cannot tell.
Nitrous air treated in the manner above mentioned is diminished about
one fourth by standing in quicksilver; and water admitted to it will
absorb about half the remainder; but if water only, and no quicksilver,
be used from the beginning, the nitrous air will be diminished much
faster and farther; so that not more than one fourth, one sixth, or one
tenth of the original quantity will remain. But I do not know that there
is any difference in the constitution of the air which remains in these
two cases.
The water which has imbibed this nitrous air exposed to iron is
remarkably green, also the phial containing it becomes deeply, and, I
believe, indelibly tinged with green; and if the water be put into
another vessel, it presently deposits a considerable quantity of matter,
which when dry appears to be the earth or ochre of iron; from which it
is evident, that the acid of the nitrous air dissolves the iron; while
the phlogiston, being set loose, diminishes nitrous air, as in the
process of the iron filings and brimstone.
Upon this hint, instead of using _iron_, I introduced a pot of _liver of
sulphur_ into a jar of nitrous air, and presently found, that what I had
before done by means of iron in six weeks, or two months, I could do by
liver of sulphur (in consequence, no doubt, of its giving its phlogiston
more freely) in less than twenty-four hours, especially when the process
was kept warm.
It is remarkable, however, that if the process with liver of sulphur be
suffered to proceed, the nitrous air will be diminished much farther.
At one time not more than one twentieth of the original quantity
remained, and how much farther it right have been diminished, I cannot
tell. In this great diminution, it does not admit a candle to burn in it
at all; and I generally found this to be the case whenever the
diminution had proceeded beyond three fourths of the original
quantity[13].
It is something remarkable, that though the diminution of nitrous air by
iron filings and brimstone very much resembles the diminution of it by
iron only, or by liver of sulphur, yet the iron filings and brimstone
never bring it to such a state as that a candle will burn in it; and
also that, after this process, it is never capable of diminishing common
air. But when it is considered that these properties are destroyed by
agitation in water, this difference in the result of processes, in other
respects similar, will appear less extraordinary; and they agree in
this, that long agitation in water makes both these kinds of nitrous air
equally fit for respiration, being equally diminished by fresh nitrous
air. It is possible that there would have been a more exact agreement
in the result of these processes, if they had been made in equal degrees
of _heat_; but the process with iron was made in the usual temperature
of the atmosphere, and that with liver of sulphur generally near a fire.
It may clearly, I think, be inferred from these experiments, that all
the difference between fresh nitrous air, that state of it in which it
is partially inflammable, or wholly so, that in which it again
extinguishes candles, and that in which it finally becomes fit for
respiration, depends upon some difference in the _mode of the
combination_ of its acid with phlogiston, or on the _proportion_ between
these two ingredients in its composition; and it is not improbable but
that, by a little more attention to these experiments, the whole mystery
of this proportion and combination may be explained.
I must not omit to observe that there was something peculiar in the
result of the first experiment which I made with nitrous air exposed to
iron; which was that, without any agitation in water, it was diminished
by fresh nitrous air, and that a candle burned in it quite naturally. To
what this difference was owing I cannot tell. This air, indeed, had been
exposed to the iron a week or two longer than in any of the other
cases, but I do not imagine that this circumstance could have produced
that difference.
When the process is in water with iron, the time in which the diminution
is accomplished is exceedingly various; being sometimes completed in a
few days, whereas at other times it has required a week or a fortnight.
Some kinds of iron also produced this effect much sooner than others,
but on what circumstances this difference depends I do not know. What
are the varieties in the result of this experiment when it is made in
quicksilver I cannot tell, because, on account of its requiring more
time, I have not repeated it so often; but I once found that nitrous air
was not sensibly changed by having been exposed to iron in quicksilver
nine days; whereas in water a very considerable alteration was always
made in much less than half that time.
It may just deserve to be mentioned, that nitrous air extremely rarified
in an air-pump dissolves iron, and is diminished by it as much as when
it is in its native state of condensation.
It is something remarkable, though I never attended to it particularly
before I made these last experiments, and it may tend to throw some
light upon them, that when a candle is extinguished, as it never fails
to be, in nitrous air, the flame seems to be a little enlarged at its
edges, by another bluish flame added to it, just before its extinction.
It is proper to observe in this place, that the electric spark taken in
nitrous air diminishes it to one fourth of its original quantity, which
is about the quantity of its diminution by iron filings and brimstone,
and also by liver of sulphur without heat. The air is also brought by
electricity to the same state as it is by iron filings and brimstone,
not diminishing common air. If the electric spark be taken in it when it
is confined by water tinged with archil, it is presently changed from
blue to red, and that to a very great degree.
When the iron nails or wires, which I have used to diminish nitrous air,
had done their office, I laid them aside, not suspecting that they could
be of any other philosophical use; but after having lain exposed to the
open air almost a fortnight; having, for some other purpose, put some of
them into a vessel containing common air, standing inverted, and
immersed in water, I was surprized to observe that the air in which they
were confined was diminished. The diminution proceeded so fast, that
the process was completed in about twenty-four hours; for in that time
the air was diminished about one fifth, so that it made no effervescence
with nitrous air, and was, therefore, no doubt, highly noxious, like air
diminished by any other process.
This experiment I have repeated a great number of times, with the same
phials, filled with nails or wires that have been suffered to rust in
nitrous air, but their power of diminishing common air grows less and
less continually. How long it will be before it is quite exhausted I
cannot tell. This diminution of air I conclude must arise from the
phlogiston, either of the nitrous air or the iron, being some way
entangled in the rust, in which the wires were encrusted, and afterwards
getting loose from it.
To the experiments upon iron filings and brimstone in nitrous air, I
must add, that when a pot full of this mixture had absorbed as much as
it could of a jar of nitrous air (which is about three fourths of the
whole) I put fresh nitrous air to it, and it continued to absorb, till
three or four jars full of it disappeared; but the absorption was
exceedingly slow at the last. Also when I drew this pot through the
water, and admitted fresh nitrous air to it, it absorbed another jar
full, and then ceased. But when I scraped off the outer surface of this
mixture, which had been so long exposed to the nitrous air, the
remainder absorbed more of the air.
When I took the top of the mixture which I had scraped off and threw
upon it the focus of a burning-glass, the air in which it was confined
was diminished, and became quite noxious; yet when I endeavoured to get
air from this matter in a jar full of quicksilver, I was able to procure
little or nothing.
It is not a little remarkable that nitrous air diminished by iron
filings and brimstone, which is about one fourth, cannot, by agitation
in water, be diminished much farther; whereas pure nitrous air may, by
the same process, be diminished to one twentieth of its whole bulk, and
perhaps much more. This is similar to the effect of the same mixture,
and of phlogiston in other cases, on fixed air; for it so far changes
its constitution, that it is afterwards incapable of mixing with water.
It is similar also to the effect of phlogiston in acid air, which of
itself is almost instantly absorbed by water; but by this addition it is
first converted into inflammable air, which does not readily mix with
water, and which, by long agitation in water, becomes of another
constitution, still less miscible with water.
I shall close this section with a few other observations of a
miscellaneous nature.
Nitrous air is as much diminished both by iron filings, and also by
liver of sulphur, when confined in quicksilver, as when it is exposed to
water.
Distilled water tinged blue with the juice of turnsole becomes red on
being impregnated with nitrous air; but by being exposed a week or a
fortnight to the common atmosphere, in open and shallow vessels, it
recovers its blue colour; though, in that time, the greater part of the
water will be evaporated. This shews that in time nitrous air escapes
from the water with which it is combined, just as fixed air does, though
by no means so readily[14].
Having dissolved silver, copper, and iron in equal quantities of spirit
of nitre diluted with water, the quantities of nitrous air produced from
them were in the following proportion; from iron 8, from copper 6-1/4,
from silver 6. In about the same proportion also it was necessary to
mix water with the spirit of nitre in each case, in order to make it
dissolve these metals with equal rapidity, silver requiring the least
water, and iron the most.
Phosphorus gave no light in nitrous air, and did not take away from its
power of diminishing common air; only when the redness of the mixture
went off, the vessel in which it was made was filled with white fumes,
as if there had been some volatile alkali in it. The phosphorus itself
was unchanged.
There is something remarkable in the effect of nitrous air on _insects_
that are put into it. I observed before that this kind of air is as
noxious as any whatever, a mouse dying the moment it is put into it; but
frogs and snails (and therefore, probably, other animals whose
respiration is not frequent) will bear being exposed to it a
considerable time, though they die at length. A frog put into nitrous
air struggled much for two or three minutes, and moved now and then for
a quarter of an hour, after which it was taken out, but did not recover.
_Wasps_ always died the moment they were put into the nitrous air. I
could never observe that they made the least motion in it, nor could
they be recovered to life afterwards. This was also the case in general
with _spiders_, _flies_, and _butterflies_. Sometimes, however, spiders
would recover after being exposed about a minute to this kind of air.
Considering how fatal nitrous air is to insects, and likewise its great
antiseptic power, I conceived that considerable use might be made of it
in medicine, especially in the form of _clysters_, in which fixed air
had been applied with some success; and in order to try whether the
bowels of an animal would bear the injection of it, I contrived, with
the help of Mr. Hey, to convey a quantity of it up the anus of a dog.
But he gave manifest signs of uneasiness, as long as he retained it,
which was a considerable time, though in a few hours afterwards he was
as lively as ever, and seemed to have suffered nothing from the
operation.
Perhaps if nitrous air was diluted either with common air, or fixed air,
the bowels might bear it better, and still it might be destructive to
_worms_ of all kinds, and be of use to check or correct putrefaction in
the intestinal canal, or other parts of the system. I repeat it once
more that, being no physician, I run no risk by such proposals as these;
and I cannot help flattering myself that, in time, very great medicinal
use will be made of the application of these different kinds of air to
the animal system. Let ingenious physicians attend to this subject, and
endeavour to lay hold of the new _handle_ which is now presented them,
before it be seized by rash empiricks; who, by an indiscriminate and
injudicious application, often ruin the credit of things and processes
which might otherwise make an useful addition to the _materia_ and _ars
medica_.
In the first publication of my papers, having experienced the remarkable
antiseptic power of nitrous air, I proposed an attempt to preserve
anatomical preparations, &c. by means of it; but Mr. Hey, who made the
trial, found that, after some months, various animal substances were
shriveled, and did not preserve their natural forms in this kind of
air.
FOOTNOTES:
[13] The result of several of these experiments I had the pleasure of
trying in the presence of the celebrated Mr. De Luc of Geneva, when he
was upon a visit to Lord Shelburne in Wiltshire.
[14] I have not repeated this experiment with that variation of
circumstances which an attention to Mr. Bewley's observation will
suggest.
SECTION IV.
_Of MARINE ACID AIR._
In my former experiments on this species of air I procured it from
spirit of salt, but I have since hit upon a much less expensive method
of getting it, by having recourse to the process by which the spirit of
salt is itself originally made. For this purpose I fill a small phial
with common salt, pour upon it a small quantity of concentrated oil of
vitriol, and receive the fumes emitted by it in a vessel previously
filled with quicksilver, and standing in a bason of quicksilver, in
which it appears in the form of a perfectly _transparent air_, being
precisely the same thing with that which I had before expelled from the
spirit of salt.
This method of procuring acid air is the more convenient, as a phial,
once prepared in this manner, will suffice, for common experiments, many
weeks; especially if a little more oil of vitriol be occasionally put to
it. It only requires a little more heat at the last than at the first.
Indeed, at the first, the heat of a person's hand will often be
sufficient to make it throw out the vapour. In warm weather it will
even keep smoking many days without the application of any other heat.
On this account, it should be placed where there are no instruments, or
any thing of metal, that can be corroded by this acid vapour. It is from
dear-bought experience that I give this advice. It may easily be
perceived when this phial is throwing out this acid vapour, as it always
appears, in the open air, in the form of a light cloud; owing, I
suppose, to the acid attracting to itself, and uniting with, the
moisture that is in the common atmosphere.
By this process I even made a stronger spirit of salt than can be
procured in any other way. For having a little water in the vessel which
contains the quicksilver, it imbibes the acid vapour, and at length
becomes truly saturated with it. Having, in this manner, impregnated
pure water with acid air, I could afterwards expel the same air from it,
as from common spirit of salt.
I observed before that this acid vapour, or air, has a strong affinity
with _phlogiston_, so that it decomposes many substances which contain
it, and with them forms a permanently inflammable air, no more liable to
be imbibed by water than inflammable air procured by any other process,
being in fact the very same thing; and that, in some cases, it even
dislodges spirit of nitre and oil of vitriol, which in general appear to
be stronger acids than itself. I have since observed that, by giving it
more time, it will extract phlogiston from substances from which I at
first concluded that it was not able to do it, as from dry wood, crusts
of bread not burnt, dry flesh, and what is more extraordinary from
flints. As there was something peculiar to itself in the process or
result of each of these experiments, it may not be improper to mention
them distinctly.
Pieces of dry _cork wood_ being put to the acid air, a small quantity
remained not imbibed by water, and was inflammable.
Very dry pieces of _oak_, being exposed to this air a day and a night,
after imbibing a considerable quantity of it, produced air which was
inflammable indeed, but in the slightest degree imaginable. It seemed to
be very nearly in the state of common air.
A piece of _ivory_ imbibed the acid vapour very slowly. In a day and a
night, however, about half an ounce measure of permanent air was
produced, and it was pretty strongly inflammable. The ivory was not
discoloured, but was rendered superficially soft, and clammy, tasting
very acid.
Pieces of _beef_, roasted, and made quite dry, but not burnt, absorbed
the acid vapour slowly; and when it had continued in this situation all
night, from five ounce measures of the air, half a measure was
permanent, and pretty strongly inflammable. This experiment succeeded a
second time exactly in the same manner; but when I used pieces of white
dry _chicken-flesh_ though I allowed the same time, and in other
respects the process seemed to go on in the same manner, I could not
perceive that any part of the remaining air was inflammable.
Some pieces of a whitish kind of _flint_, being put into a quantity of
acid air, imbibed but a very little of it in a day and a night; but of
2-1/2 ounce measures of it, about half a measure remained unabsorbed by
water, and this was strongly inflammable, taking fire just like an equal
mixture of inflammable and common air. At another time, however, I could
not procure any inflammable air by this means, but to what circumstance
these different results were owing I cannot tell.
That inflammable air is produced from _charcoal_ in acid air I observed
before. I have since found that it may likewise be procured from _pit
coal_, without being charred.
Inflammable air I had also observed to arise from the exposure of spirit
of wine, and various _oily_ substances, to the vapour of spirit of salt.
I have since made others of a similar nature, and as peculiar
circumstances attended some of these experiments, I shall recite them
more at large.
_Essential oil of mint_ absorbed this air pretty fast, and presently
became of a deep brown colour. When it was taken out of this air it was
of the consistence of treacle, and sunk in water, smelling differently
from what it did before; but still the smell of the mint was
predominant. Very little or none of the air was fixed, so as to become
inflammable; but more time would probably have produced this effect.
_Oil of turpentine_ was also much thickened, and became of a deep brown
colour, by being saturated with acid air.
_Ether_ absorbed acid air very fast, and became first of a turbid white,
and then of a yellow and brown colour. In one night a considerable
quantity of permanent air was produced, and it was strongly inflammable.
Having, at one time, fully saturated a quantity of ether with acid air,
I admitted bubbles of common air to it, through the quicksilver, by
which it was confined, and observed that white fumes were made in it, at
the entrance of every bubble, for a considerable time.
At another time, having fully saturated a small quantity of ether with
acid air, and having left the phial in which it was contained nearly
full of the air, and inverted, it was by some accident overturned; when,
instantly, the whole room was filled with a visible fume, like a white
cloud, which had very much the smell of ether, but peculiarly offensive.
Opening the door and window of the room, this light cloud filled a long
passage, and another room. In the mean time the ether was seemingly all
vanished, but some time after the surface of the quicksilver in which
the experiment had been made was covered with a liquor that tasted very
acid; arising, probably, from the moisture in the atmosphere attracted
by the acid vapour with which the ether had been impregnated.
This visible cloud I attribute to the union of the moisture in the
atmosphere with the compound of the acid air and ether. I have since
saturated other quantities of ether with acid air, and found it to be
exceedingly volatile, and inflammable. Its exhalation was also visible,
but not in so great a degree as in the case above mentioned.
_Camphor_ was presently reduced into a fluid state by imbibing acid air,
but there seemed to be something of a whitish sediment in it. After
continuing two days in this situation I admitted water to it;
immediately upon which the camphor resumed its former solid state, and,
to appearance, was the very same substance that it had been before; but
the taste of it was acid, and a very small part of the air was
permanent, and slightly inflammable.
The acid air seemed to make no impression upon a piece of Derbyshire
_spar_, of a very dark colour, and which, therefore, seemed to contain a
good deal of phlogiston.
As the acid air has so near an affinity with phlogiston, I expected that
the fumes of _liver of sulphur_, which chemists agree to be phlogistic,
would have united with it, so as to form inflammable air; but I was
disappointed in that expectation. This substance imbibed half of the
acid air to which it was introduced: one fourth of the remainder, after
standing one day in quicksilver, was imbibed by water, and what was left
extinguished a candle. This experiment, however, seems to prove that
acid air and phlogiston may form a permanent kind of air that is not
inflammable. Perhaps it may be air in such a state as common air loaded
with phlogiston, and from which the fixed air has been precipitated. Or
rather, it may be the same thing with inflammable air, that has lost its
inflammability by long standing in water. It well deserves a farther
examination.
The following experiments are those in which the _stronger acids_ were
made use of, and therefore they may assist us farther to ascertain their
affinities with certain substances, with respect to this marine acid in
the form of air.
I put a quantity of strong concentrated _oil of vitriol_ to acid air,
but it was not at all affected by it in a day and a night. In order to
try whether it would not have more power in a more condensed state, I
compressed it with an additional atmosphere; but upon taking off this
pressure, the air expanded again, and appeared to be not at all
diminished. I also put a quantity of strong _spirit of nitre_ to it
without any sensible effect. We may conclude, therefore, that the
marine acid, in this form of air, is not able to dislodge the other
acids from their union with water.
_Blue vitriol_, which is formed by the union of the vitriolic acid with
copper, turned to a dark green the moment that it was put to the acid
air, which it absorbed, though slowly. Two pieces, as big as small nuts,
absorbed three ounce measures of the air in about half an hour. The
green colour was very superficial; for it was easily wiped or washed
off.
_Green copperas_ turned to a deeper green upon being put into acid air,
which it absorbed slowly. _White copperas_ absorbed this air very fast,
and was dissolved in it.
_Sal ammoniac_, being the union of spirit of salt with volatile alkali,
was no more affected with the acid air than, as I have observed before,
common salt was.
I also introduced to the acid air various other substances, without any
particular expectation; and it may be worth while to give an account of
the results, that the reader may draw from them such conclusions as he
shall think reasonable.
_Borax_ absorbed acid air about as fast as blue vitriol, but without any
thing else that was observable.
Fine white _sugar_ absorbed this air slowly, was thoroughly penetrated
with it, became of a deep brown colour, and acquired a smell that was
peculiarly pungent.
A piece of _quick lime_ being put to about twelve or fourteen ounce
measures of acid air, and continuing in that situation about two days,
there remained one ounce measure of air that was not absorbed by water,
and it was very strongly inflammable, as much so as a mixture of half
inflammable and half common air. Very particular care was taken that no
common air mixed with the acid air in this process. At another time,
from about half the quantity of acid air above mentioned, with much less
quick-lime, and in the space of one day, I got half an ounce measure of
air that was inflammable in a slight degree only. This experiment proves
that some part of the phlogiston which escapes from the fuel, in contact
with which the lime is burned, adheres to it. But I am very far from
thinking that the causticity of quick-lime is at all owing to this
circumstance.
I have made a few more experiments on the mixture of acid air with
_other kinds of air_, and think that it may be worth while to mention
them, though nothing of consequence, at least nothing but negative
conclusions, can be drawn from them.
A quantity of common air saturated with nitrous air was put to a
quantity of acid air, and they continued together all night, without any
sensible effect. The quantity of both remained the same, and water being
admitted to them, it absorbed all the acid air, and left the other just
as before.
A mixture of two thirds of air diminished by iron filings and brimstone,
and one third acid air, were mixed together, and left to stand four
weeks in quicksilver. But when the mixture was examined, water presently
imbibed all the acid air, and the diminished air was found to be just
the same that it was before. I had imagined that the acid air might have
united with the phlogiston with which the diminished air was
overcharged, so as to render it wholsome; and I had read an account of
the stench arising from putrid bodies being corrected by acid fumes.
The remaining experiments, in which the acid air was principally
concerned, are of a miscellaneous nature.
I put a piece of dry _ice_ to a quantity of acid air (as was observed in
the section concerning _alkaline_ air) taking it with a forceps, which,
as well as the air itself, and the quicksilver by which it had been
confined; had been exposed to the open air for an hour, in a pretty
strong frost. The moment it touched the air it was dissolved as fast as
it would have been by being thrown into a hot fire, and the air was
presently imbibed. Putting fresh pieces of ice to that which was
dissolved before, they were also dissolved immediately, and the water
thus procured did not freeze again, though it was exposed a whole night,
in a very intense frost.
Flies and spiders die in acid air, but not so quickly as in nitrous air.
This surprized me very much; as I had imagined that nothing could be
more speedily fatal to all animal life than this pure acid vapour.
As inflammable air, I have observed, fires at one explosion in the
vapour of smoking spirit of nitre, just like an equal mixture of
inflammable and common air, I thought it was possible that the fume
which naturally rises from common spirit of salt might have the same
effect, but it had not. For this purpose I treated the spirit of salt,
as I had before done the smoking spirit of nitre; first filling a phial
with it, then inverting it in a vessel containing a quantity of the same
acid; and having thrown the inflammable air into it, and thereby driven
out all the acid, turning it with its mouth upwards, and immediately
applying a candle to it.
Acid air not being so manageable as most of the other kinds of air, I
had recourse to the following peculiar method, in order to ascertain its
_specific gravity_. Having filled an eight ounce phial with this air,
and corked it up, I weighed it very accurately; and then, taking out the
cork, I blew very strongly into it with a pair of bellows, that the
common air might take place of the acid; and after this I weighed it
again, together with the cork, but I could not perceive the least
difference in the weight. I conclude, however, from this experiment,
that the acid air is heavier than the common air, because the mouth of
the phial and the inside of it were evidently moistened by the water
which the acid vapour had attracted from the air, which moisture must
have added to the weight of the phial.
SECTION V.
_Of INFLAMMABLE AIR._
It will have appeared from my former experiments, that inflammable air
consists chiefly, if not wholly, of the union of an acid vapour with
phlogiston; that as much of the phlogiston as contributes to make air
inflammable is imbibed by the water in which it is agitated; that in
this process it soon becomes fit for respiration, and by the continuance
of it comes at length to extinguish flame. These observations, and
others which I have made upon this kind of air, have been confirmed by
my later experiments, especially those in which I have connected
_electrical experiments_ with those on air.
The electric spark taken in any kind of _oil_ produces inflammable air,
as I was led to observe in the following manner. Having found, as will
be mentioned hereafter, that ether doubles the quantity of any kind of
air to which it is admitted; and being at that time engaged in a course
of experiments to ascertain the effect of the electric matter on all the
different kinds of air, I had the curiosity to try what it would do with
_common air_, thus increased by means of ether. The very first spark, I
observed, increased the quantity of this air very considerably, so that
I had very soon six or eight times as much as I began with; and whereas
water imbibes all the ether that is put to any kind of air, and leaves
it without any visible change, with respect to quantity or quality, this
air, on the contrary, was not imbibed by water. It was also very little
diminished by the mixture of nitrous air. From whence it was evident,
that it had received an addition of some other kind of air, of which it
now principally consisted.
In order to determine whether this effect was produced by the _wire_, or
the _cement_ by which the air was confined (as I thought it possible
that phlogiston might be discharged from them) I made the experiment in
a glass syphon, fig. 19, and by that means I contrived to make the
electric spark pass from quicksilver through the air on which I made the
experiment, and the effect was the same as before. At one time there
happened to be a bubble of common air, without any ether, in one part of
the syphon, and another bubble with ether in another part of it; and it
was very amusing to observe how the same electric sparks diminished the
former of these bubbles, and increased the latter.
It being evident that the _ether_ occasioned the difference that was
observable in these two cases, I next proceeded to take the electric
spark in a quantity of ether only, without any air whatever; and
observed that every spark produced a small bubble; and though, while the
sparks were taken in the ether itself, the generation of air was slow,
yet when so much air was collected, that the sparks were obliged to pass
through it, in order, to come to the ether and the quicksilver on which
it rested, the increase was exceedingly rapid; so that, making the
experiment in small tubes, as fig. 16, the quicksilver soon receded
beyond the striking distance. This air, by passing through water, was
diminished to about one third, and was inflammable.
One quantity of air produced in this manner from ether I suffered to
stand two days in water, and after that I transferred it several times
through the water, from one vessel to another, and still found that it
was very strongly inflammable; so that I have no doubt of its being
genuine inflammable air, like that which is produced from metals by
acids, or by any other chemical process.
Air produced from ether, mixed both with common and nitrous air, was
likewise inflammable; but in the case of the nitrous air, the original
quantity bore a very small proportion to the quantity generated.
Concluding that the inflammable matter in this air came from the ether,
as being of the class of _oils_, I tried other kinds of oil, as _oil of
olives_, _oil of turpentine_, and _essential oil of mint_, taking the
electric spark in them, without any air to begin with, and found that
inflammable air was produced in this manner from them all. The
generation of air from oil of turpentine was the quickest, and from the
oil of olives the slowest in these three cases.
By the same process I got inflammable air from _spirit of wine_, and
about as copiously as from the essential oil of mint. This air continued
in water a whole night, and when it was transferred into another vessel
was strongly inflammable.
In all these cases the inflammable matter might be supposed to arise
from the inflammable substances on which the experiments were made. But
finding that, by the same process I could get inflammable air from the
_volatile spirit of sal ammoniac_, I conclude that the phlogiston was in
part supplied by the electric matter itself. For though, as I have
observed before, the alkaline air which is expelled from the spirit of
sal ammoniac be inflammable, it is so in a very slight degree, and can
only be perceived to be so when there is a considerable quantity of it.
Endeavouring to procure air from a caustic alkaline liquor, accurately
made for me by Mr. Lane, and also from spirit of salt, I found that the
electric spark could not be made visible in either of them; so that they
must be much more perfect conductors of electricity than water, or other
fluid substances. This experiment well deserves to be prosecuted.
I observed before that inflammable air, by standing long in water, and
especially by agitation in water, loses its inflammability; and that in
the latter case, after passing through a state in which it makes some
approach to common air (just admitting a candle to burn in it) it comes
to extinguish a candle. I have since made another observation of this
kind, which well deserves to be recited. It relates to the inflammable
air generated from oak the 27th of July 1771, of which I have made
mention before.
This air I have observed to have been but weakly inflammable some months
after it was generated, and to have been converted into pretty good or
wholesome air by no great degree of agitation in water; but on the 27th
of March 1773, I found the remainder of it to be exceedingly good air. A
candle burned in it perfectly well, and it was diminished by nitrous air
almost as much as common air.
I shall conclude this section with a few miscellaneous observations of
no great importance.
Inflammable air is not changed by being made to pass many times through
a red-hot iron tube. It is also no more diminished or changed by the
fumes of liver of sulphur, or by the electric spark, than I have before
observed it to have been by a mixture of iron filings and brimstone.
When the electric spark was taken in it, it was confined by a quantity
of water tinged blue with the juice of archil, but the colour remained
unchanged.
I put two _wasps_ into inflammable air, and let them remain there a
considerable time, one of them near an hour. They presently ceased to
move, and seemed to be quite dead for about half an hour after they were
taken into the open air; but then they came to life again, and presently
after seemed to be as well as ever they had been.
SECTION VI.
_Of FIXED AIR._
The additions I have made to my observations on _fixed air_ are neither
numerous nor considerable.