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[Illustration: _To face the Title._]
EXPERIMENTS AND OBSERVATIONS ON DIFFERENT KINDS OF AIR.
[Price 5s. unbound.]
Quamobrem, si qua est erga Creatorem humilitas, si qua operum
ejus reverentia et magnificatio, si qua charitas in homines, si
erga necessitates et aerumnas humanas relevandas studium, si
quis amor veritatis in naturalibus, et odium tenebrarum, et
intellectus purificandi desiderium; orandi sunt homines iterum
atque iterum, ut, missis philosophiis istis volaticis et
preposteris, quae theses hypothesibus anterposuerunt, et
experientiam captivam duxerunt, atque de operibus dei
triumpharunt, summisse, et cum veneratione quadam, ad volumen
creaturarum evolvendum accedant; atque in eo moram faciant,
meditentur, et ab opinionibus abluti et mundi, caste et integre
versentur.----In interpretatione ejus eruenda nulli operae
parcant, sed strenue procedant, persistant, immoriantur.
LORD BACON IN INSTAURATIONE MAGNA.
EXPERIMENTS
AND
OBSERVATIONS
ON DIFFERENT KINDS OF
AIR.
By JOSEPH PRIESTLEY, LL.D. F.R.S.
The SECOND EDITION Corrected.
Fert animus Causas tantarum expromere rerum;
Immensumque aperitur opus.
LUCAN
LONDON:
Printed for J. JOHNSON, No. 72, in St. Paul's Church-Yard.
MDCCLXXV.
TO THE RIGHT HONOURABLE
THE EARL OF SHELBURNE,
THIS TREATISE IS
WITH THE GREATEST GRATITUDE
AND RESPECT,
INSCRIBED,
BY HIS LORDSHIP's
MOST OBLIGED,
AND OBEDIENT
HUMBLE SERVANT,
J. PRIESTLEY.
Transcriber's Note: Footnotes have been moved to the end of the chapter.
The errata listed at the end of the book have been corrected in the
text. In the text, there are places where the apothecary symbols for
ounce and dram are used. These are changed to oz. and dr. in the text
file.
THE PREFACE.
One reason for the present publication has been the favourable reception
of those of my _Observations on different kinds of air_, which were
published in the Philosophical Transactions for the year 1772, and the
demand for them by persons who did not chuse, for the sake of those
papers only, to purchase the whole volume in which they were contained.
Another motive was the _additions_ to my observations on this subject,
in consequence of which my papers grew too large for such a publication
as the _Philosophical Transactions_.
Contrary, therefore, to my intention, expressed Philosophical
Transactions, vol. 64. p. 90, but with the approbation of the President,
and of my friends in the society, I have determined to send them no
more papers for the present on this subject, but to make a separate and
immediate publication of all that I have done with respect to it.
Besides, considering the attention which, I am informed, is now given to
this subject by philosophers in all parts of Europe, and the rapid
progress that has already been made, and may be expected to be made in
this branch of knowledge, all unnecessary delays in the publication of
experiments relating to it are peculiarly unjustifiable.
When, for the sake of a little more reputation, men can keep brooding
over a new fact, in the discovery of which they might, possibly, have
very little real merit, till they think they can astonish the world with
a system as complete as it is new, and give mankind a prodigious idea of
their judgment and penetration; they are justly punished for their
ingratitude to the fountain of all knowledge, and for their want of a
genuine love of science and of mankind, in finding their boasted
discoveries anticipated, and the field of honest fame pre-occupied, by
men, who, from a natural ardour of mind, engage in philosophical
pursuits, and with an ingenuous simplicity immediately communicate to
others whatever occurs to them in their inquiries.
As to myself, I find it absolutely impossible to produce a work on this
subject that shall be any thing like _complete_. My first publication I
acknowledged to be very imperfect, and the present, I am as ready to
acknowledge, is still more so. But, paradoxical as it may seem, this
will ever be the case in the progress of natural science, so long as the
works of God are, like himself, infinite and inexhaustible. In
completing one discovery we never fail to get an imperfect knowledge of
others, of which we could have no idea before; so that we cannot solve
one doubt without creating several new ones.
Travelling on this ground resembles Pope's description of travelling
among the Alps, with this difference, that here there is not only
_succession_, but an _increase_ of new objects and new difficulties.
So pleas'd at first the tow'ring Alps we try,
Mount o'er the vales, and seem to tread the sky.
Th' eternal snows appear already past,
And the first clouds and mountains seem the last,
But those attain'd, we tremble to survey
The growing labours of the lengthen'd way.
Th' increasing prospect tires our wand'ring eyes,
Hills peep o'er hills, and Alps on Alps arise.
ESSAY ON CRITICISM.
Newton, as he had very little knowledge of _air_, so he had few doubts
concerning it. Had Dr. Hales, after his various and valuable
investigations, given a list of all his _desiderata_, I am confident
that he would not have thought of one in ten that had occurred to me at
the time of my last publication; and my doubts, queries, and hints for
new experiments are very considerably increased, after a series of
investigations, which have thrown great light upon many things of which
I was not able to give any explanation before.
I would observe farther, that a person who means to serve the cause of
science effectually, must hazard his own reputation so far as to risk
even _mistakes_ in things of less moment. Among a multiplicity of new
objects, and new relations, some will necessarily pass without
sufficient attention; but if a man be not mistaken in the principal
objects of his pursuits, he has no occasion to distress himself about
lesser things.
In the progress of his inquiries he will generally be able to rectify
his own mistakes; or if little and envious souls should take a malignant
pleasure in detecting them for him, and endeavouring to expose him, he
is not worthy of the name of a philosopher, if he has not strength of
mind sufficient to enable him not to be disturbed at it. He who does not
foolishly affect to be above the failings of humanity, will not be
mortified when it is proved that he is but a man.
In this work, as well as in all my other philosophical writings, I have
made it a rule not to conceal the _real views_ with which I have made
experiments; because though, by following a contrary maxim, I might have
acquired a character of greater sagacity, I think that two very good
ends are answered by the method that I have adopted. For it both tends
to make a narrative of a course of experiments more interesting, and
likewise encourages other adventurers in experimental philosophy;
shewing them that, by pursuing even false lights, real and important
truths may be discovered, and that in seeking one thing we often find
another.
In some respects, indeed, this method makes the narrative _longer_, but
it is by making it less tedious; and in other respects I have written
much more concisely than is usual with those who publish accounts of
their experiments. In this treatise the reader will often find the
result of long processes expressed in a few lines, and of many such in a
single paragraph; each of which, if I had, with the usual parade,
described it at large (explaining first the _preparation_, then reciting
the _experiment_ itself, with the _result_ of it, and lastly making
suitable _reflections_) would have made as many sections or chapters,
and have swelled my book to a pompous and respectable size. But I have
the pleasure to think that those philosophers who have but little time
to spare for _reading_, which is always the case with those who _do_
much themselves, will thank me for not keeping them too long from their
own pursuits; and that they will find rather more in the volume, than
the appearance of it promises.
I do not think it at all degrading to the business of experimental
philosophy, to compare it, as I often do, to the diversion of _hunting_,
where it sometimes happens that those who have beat the ground the most,
and are consequently the best acquainted with it, weary themselves
without starting any game; when it may fall in the way of a mere
passenger; so that there is but little room for boasting in the most
successful termination of the chace.
The best founded praise is that which is due to the man, who, from a
supreme veneration for the God of nature, takes pleasure in
contemplating his _works_, and from a love of his fellow-creatures, as
the offspring of the same all-wise and benevolent parent, with a
grateful sense and perfect enjoyment of the means of happiness of which
he is already possessed, seeks, with earnestness, but without murmuring
or impatience, that greater _command of the powers of nature_, which can
only be obtained by a more extensive and more accurate _knowledge_ of
them; and which alone can enable us to avail ourselves of the numerous
advantages with which we are surrounded, and contribute to make our
common situation more secure and happy.
Besides, the man who believes that there is a _governor_ as well as a
_maker_ of the world (and there is certainly equal reason to believe
both) will acknowledge his providence and favour at least as much in a
successful pursuit of _knowledge_, as of _wealth_; which is a sentiment
that entirely cuts off all boasting with respect to ourselves, and all
envy and jealousy with respect to others; and disposes us mutually to
rejoice in every new light that we receive, through whose hands soever
it be conveyed to us.
I shall pass for an enthusiast with some, but I am perfectly easy under
the imputation, because I am happy in those views which subject me to
it; but considering the amazing improvements in natural knowledge which
have been made within the last century, and the many ages, abounding
with men who had no other object but study, in which, however, nothing
of this kind was done, there appears to me to be a very particular
providence in the concurrence of those circumstances which have produced
so great a change; and I cannot help flattering myself that this will be
instrumental in bringing about other changes in the state of the world,
of much more consequence to the improvement and happiness of it.
This rapid progress of knowledge, which, like the progress of a _wave_
of the sea, of _sound_, or of _light_ from the sun, extends itself not
this way or that way only, but _in all directions_, will, I doubt not,
be the means, under God, of extirpating _all_ error and prejudice, and
of putting an end to all undue and usurped authority in the business of
_religion_, as well as of _science_; and all the efforts of the
interested friends of corrupt establishments of all kinds will be
ineffectual for their support in this enlightened age: though, by
retarding their downfal, they may make the final ruin of them more
complete and glorious. It was ill policy in Leo the Xth to patronize
polite literature. He was cherishing an enemy in disguise. And the
English hierarchy (if there be any thing unsound in its constitution)
has equal reason to tremble even at an air-pump, or an electrical
machine.
There certainly never was any period in which _natural knowledge_ made
such a progress as it has done of late years, and especially in this
country; and they who affect to speak with supercilious contempt of the
publications of the present age in general, or of the Royal Society in
particular, are only those who are themselves engaged in the most
trifling of all literary pursuits, who are unacquainted with all real
science, and are ignorant of the progress and present state of it.[1]
It is true that the rich and the great in this country give less
attention to these subjects than, I believe, they were ever known to do,
since the time of Lord Bacon, and much less than men of rank and fortune
in other countries give to them. But with us this loss is made up by
men of leisure, spirit, and ingenuity, in the middle ranks of life,
which is a circumstance that promises better for the continuance of this
progress in useful knowledge than any noble or royal patronage. With us,
politics chiefly engage the attention of those who stand foremost in the
community, which, indeed, arises from the _freedom_ and peculiar
_excellence_ of our constitution, without which even the spirit of men
of letters in general, and of philosophers in particular, who never
directly interfere in matters of government, would languish.
It is rather to be regretted, however, that, in such a number of
nobility and gentry, so very few should have any taste for scientifical
pursuits, because, for many valuable purposes of science, _wealth_ gives
a decisive advantage. If extensive and lasting _fame_ be at all an
object, literary, and especially scientifical pursuits, are preferable
to political ones in a variety of respects. The former are as much more
favourable for the display of the human faculties than the latter, as
the _system of nature_ is superior to any _political system_ upon earth.
If extensive _usefulness_ be the object, science has the same advantage
over politics. The greatest success in the latter seldom extends farther
than one particular country, and one particular age; whereas a
successful pursuit of science makes a man the benefactor of all mankind,
and of every age. How trifling is the fame of any statesman that this
country has ever produced to that of Lord Bacon, of Newton, or of Boyle;
and how much greater are our obligations to such men as these, than to
any other in the whole _Biographia Britannica_; and every country, in
which science has flourished, can furnish instances for similar
observations.
Here my reader will thank me, and the writer will, I hope, forgive me,
if I quote a passage from the postscript of a letter which I happen to
have just received from that excellent, and in my opinion, not too
enthusiastical philosopher, father Beccaria of Turin.
_Mi spiace che il mondo politico ch'e pur tanto passeggero,
rubbi il grande Franklin al mondo della natura, che non sa ne
cambiare, ne mancare._ In English. "I am sorry that the
_political world_, which is so very transitory, should take the
great Franklin from the _world of nature_, which can never
change, or fail."
I own it is with peculiar pleasure that I quote this passage, respecting
this truly great man, at a time when some of the infatuated politicians
of this country are vainly thinking to build their wretched and
destructive projects, on the ruins of his established reputation; a
reputation as extensive as the spread of science itself, and of which it
is saying very little indeed, to pronounce that it will last and
flourish when the names of all his enemies shall be forgotten.
I think it proper, upon this occasion, to inform my friends, and the
public, that I have, for the present, suspended my design of writing
_the history and present state of all the branches of experimental
philosophy_. This has arisen not from any dislike of the undertaking,
but, in truth, because I see no prospect of being reasonably indemnified
for so much labour and expence, notwithstanding the specimens I have
already given of that work (in the _history of electricity_, and of the
_discoveries relating to vision, light, and colours_) have met with a
much more favourable reception from the best judges both at home and
abroad, than I expected. Immortality, if I should have any view to it,
is not the proper price of such works as these.
I propose, however, having given so much attention to the subject of
_air_, to write, at my leisure, the history and present state of
discoveries relating to it; in which case I shall, as a part of it,
reprint this work, with such improvements as shall have occurred to me
at that time; and I give this notice of it, that no person who intends
to purchase it may have reason (being thus apprised of my intention) to
complain of buying the same thing twice. If any person chuse it, he may
save his five or six shillings for the present, and wait five or six
years longer (if I should live so long) for the opportunity of buying
the same thing, probably much enlarged, and at the same time a complete
account of all that has been done by others relating to this subject.
Though for the plain, and I hope satisfactory reason above mentioned, I
shall probably write no other _histories_ of this kind, I shall, as
opportunity serves, endeavour to provide _materials_ for such histories,
by continuing my experiments, keeping my eyes open to such new
appearances as may present themselves, investigating them as far as I
shall be able, and never failing to communicate to the public, by some
channel or other, the result of my observations.
In the publication of this work I have thought that it would be
agreeable to my readers to preserve, in some measure, the order of
history, and therefore I have not thrown together all that I have
observed with respect to each kind of air, but have divided the work
into _two parts_; the former containing what was published before, in
the Philosophical Transactions, with such observations and corrections
as subsequent experience has suggested to me; and I have reserved for
the latter part of the work an account of the experiments which I have
made since that publication, and after a pretty long interruption in my
philosophical pursuits, in the course of the last summer. Besides I am
sensible that in the latter part of this work a different arrangement of
the subjects will be more convenient, for their mutual illustration.
Some persons object to the term _air_, as applied to _acid_, _alkaline_,
and even _nitrous air_; but it is certainly very convenient to have a
common term by which to denote things which have so many common
properties, and those so very striking; all of them agreeing with the
air in which we breathe, and with _fixed air_, in _elasticity_, and
_transparency_, and in being alike affected by heat or cold; so that to
the eye they appear to have no difference at all. With much more reason,
as it appears to me, might a person object to the common term _metal_,
as applied to things so very different from one another as gold,
quicksilver, and lead.
Besides, _acid_ and _alkaline_ air do not differ from _common air_ (in
any respect that can countenance an objection to their having a common
appellation) except in such properties as are common to it with _fixed
air_, though in a different degree; viz. that of being imbibed by water.
But, indeed, all kinds of air, common air itself not excepted, are
capable of being imbibed by water in some degree.
Some may think the terms acid and alkaline _vapour_ more proper than
acid and alkaline _air_. But the term _vapour_ having always been
applied to elastic matters capable of being condensed in the temperature
of the atmosphere, especially the vapour of water, it seems harsh to
apply it to any elastic substance, which at the same time that it is as
transparent as the air we breathe, is no more affected by cold than it
is.
As my former papers were immediately translated into several foreign
languages, I may presume that this treatise, having a better title to
it, will be translated also; and, upon this presumption, I cannot help
expressing a wish, that it may be done by persons who have a competent
knowledge of _subject_, as well as of the _English language_. The
mistakes made by some foreigners, have induced me to give this caution.
_London, Feb._
_1774._
ADVERTISEMENT.
The _weights_ mentioned in the course of this treatise are _Troy_, and
what is called _an ounce measure of air_, is the space occupied by an
ounce weight of water, which is equal to 480 grains, and is, therefore,
almost two _cubic inches_ of water; for one cubic inch weighs 254
grains.
FOOTNOTES:
[1] See Sir John Pringle's _Discourse on the different kinds of air_, p.
29, which, if it became me to do it, I would recommend to the reader, as
containing a just and elegant account of the several discoveries that
have been successively made, relating to the subject of this treatise.
THE CONTENTS.
THE INTRODUCTION.
Section I. _A general view of PRECEDING DISCOVERIES relating to
AIR_ Page 1
Sect. II. _An Account of the APPARATUS with which the following
Experiments were made_ 6
PART I.
_Experiments and Observations made in, and before the Year 1772._ 23
Sect. I. _Of FIXED AIR_ 25
Sect. II. _Of AIR in which a CANDLE, or BRIMSTONE, has burned out_ 43
Sect. III. _Of INFLAMMABLE AIR_ 55
Sect. IV. _Of AIR infected with ANIMAL RESPIRATION, or PUTREFACTION_ 70
Sect. V. _Of AIR in which a mixture of BRIMSTONE and FILINGS of
IRON has stood_ 105
Sect. VI. _Of NITROUS AIR_ 108
Sect. VII. _Of AIR infected with the FUMES of BURNING CHARCOAL_ 129
Sect. VIII. _Of the effect of the CALCINATION of METALS, and of the
EFFLUVIA of PAINT made with WHITE-LEAD and OIL, on AIR_ 133
Sect. IX. _Of MARINE ACID AIR_ 143
Sect. X. _Miscellaneous Observations_ 154
PART II.
_Experiments and Observations made in the Year 1773, and the Beginning of
1774._
Sect. I. _Observations on ALKALINE AIR_ 163
Sect. II. _Of COMMON AIR diminished, and made noxious by various
processes_ 177
Sect. III. _Of NITROUS AIR_ 203
Sect. IV. _Of MARINE ACID AIR_ 229
Sect. V. _Of INFLAMMABLE AIR_ 242
Sect. VI. _Of FIXED AIR_ 248
Sect. VII. MISCELLANEOUS EXPERIMENTS 252
Sect. VIII. _QUERIES, SPECULATIONS, and HINTS_ 258
THE APPENDIX.
Number I. _EXPERIMENTS made by Mr. Hey to prove that there is no
OIL of VITRIOL in water impregnated with FIXED AIR_ 288
Number II. _A Letter from Mr. HEY to Dr. PRIESTLEY, concerning the
effects of fixed Air applied by way of Clyster_ 292
Number III. _Observations on the MEDICINAL USES of FIXED AIR. By
THOMAS PERCIVAL, M. D. Fellow of the ROYAL SOCIETY,
and of the SOCIETY of ANTIQUARIES in LONDON_ 300
Number IV. _Extract of a Letter from WILLIAM FALCONER, M. D. of BATH_ 314
Number V. _Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT
MASSINGHAM, NORFOLK_ 317
Num. VI. _A Letter from Dr. FRANKLIN_ 321
Number VII. _Extract of Letter from Mr. HENRY of MANCHESTER_ 323
THE INTRODUCTION.
SECTION I.
_A general view of PRECEDING DISCOVERIES relating to air._
For the better understanding of the experiments and observations on
different kinds of air contained in this treatise, it will be useful to
those who are not acquainted with the history of this branch of natural
philosophy, to be informed of those facts which had been discovered by
others, before I turned my thoughts to the subject; which suggested, and
by the help of which I was enabled to pursue, my inquiries. Let it be
observed, however, that I do not profess to recite in this place _all_
that had been discovered concerning air, but only those discoveries the
knowledge of which is necessary, in order to understand what I have done
myself; so that any person who is only acquainted with the general
principles of natural philosophy, may be able to read this treatise,
and, with proper attention, to understand every part of it.
That the air which constitutes the atmosphere in which we live has
_weight_, and that it is _elastic_, or consists of a compressible and
dilatable fluid, were some of the earliest discoveries that were made
after the dawning of philosophy in this western part of the world.
That elastic fluids, differing essentially from the air of the
atmosphere, but agreeing with it in the properties of weight,
elasticity, and transparency, might be generated from solid substances,
was discovered by Mr. Boyle, though two remarkable kinds of factitious
air, at least the effects of them, had been known long before to all
miners. One of these is heavier than common air. It lies at the bottom
of pits, extinguishes candles, and kills animals that breathe it, on
which account it had obtained the name of the _choke damp_. The other is
lighter than common air, taking its place near the roofs of
subterraneous places, and because it is liable to take fire, and
explode, like gunpowder, it had been called the _fire damp_. The word
_damp_ signifies _vapour_ or _exhalation_ in the German and Saxon
language.
Though the former of these kinds of air had been known to be noxious,
the latter I believe had not been discovered to be so, having always
been found in its natural state, so much diluted with common air, as to
be breathed with safety. Air of the former kind, besides having been
discovered in various caverns, particularly the _grotta del Cane_ in
Italy, had also been observed on the surface of fermenting liquors, and
had been called _gas_ (which is the same with _geist_, or _spirit_) by
Van Helmont, and other German chymists; but afterwards it obtained the
name of _fixed air_, especially after it had been discovered by Dr.
Black of Edinburgh to exist, in a fixed state, in alkaline salts, chalk,
and other calcareous substances.
This excellent philosopher discovered that it is the presence of the
fixed air in these substances that renders them _mild_, and that when
they are deprived of it, by the force of fire, or any other process,
they are in that state which had been called _caustic_, from their
corroding or burning animal and vegetable substances.
Fixed air had been discovered by Dr. Macbride of Dublin, after an
observation of Sir John Pringle's, which led to it, to be in a
considerable degree antiseptic; and since it is extracted in great
plenty from fermenting vegetables, he had recommended the use of _wort_
(that is an infusion of malt in water) as what would probably give
relief in the sea-scurvy, which is said to be a putrid disease.
Dr. Brownrigg had also discovered that the same species of air is
contained in great quantities in the water of the Pyrmont spring at Spa
in Germany, and in other mineral waters, which have what is called an
_acidulous_ taste, and that their peculiar flavour, briskness, and
medicinal virtues, are derived from this ingredient.
Dr. Hales, without seeming to imagine that there was any material
difference between these kinds of air and common air, observed that
certain substances and operations _generate_ air, and others _absorb_
it; imagining that the diminution of air was simply a taking away from
the common mass, without any alteration in the properties of what
remained. His experiments, however, are so numerous, and various, that
they are justly esteemed to be the solid foundation of all our knowledge
of this subject.
Mr. Cavendish had exactly ascertained the specific gravities of fixed
and inflammable air, shewing the former of them to be 1-1/2 heavier
than common air, and the latter ten times lighter. He also shewed that
water would imbibe more than its own bulk of fixed air.
Lastly, Mr. Lane discovered that water thus impregnated with fixed air
will dissolve a considerable quantity of iron, and thereby become a
strong chalybeate.
These, I would observe, are by no means all the discoveries concerning
air that have been made by the gentlemen whose names I have mentioned,
and still less are they all that have been made by others; but they
comprise all the previous knowledge of this subject that is necessary to
the understanding of this treatise; except a few particulars, which will
be mentioned in the course of the work, and which it is, therefore,
unnecessary to recite in this place.
SECTION II.
_An account of the APPARATUS with which the following experiments were
made._
Rather than describe at large the manner in which every particular
experiment that I shall have occasion to recite was made, which would
both be very tedious, and require an unnecessary multiplicity of
drawings, I think it more adviseable to give, at one view, an account of
all my apparatus and instruments, or at least of every thing that can
require a description, and of all the different operations and processes
in which I employ them.
It will be seen that my apparatus for experiments on air is, in fact,
nothing more than the apparatus of Dr. Hales, Dr. Brownrigg, and Mr.
Cavendish, diversified, and made a little more simple. Yet
notwithstanding the simplicity of this apparatus, and the ease with
which all the operations are conducted, I would not have any person, who
is altogether without experience, to imagine that he shall be able to
select any of the following experiments, and immediately perform it,
without difficulty or blundering. It is known to all persons who are
conversant in experimental philosophy, that there are many little
attentions and precautions necessary to be observed in the conducting of
experiments, which cannot well be described in words, but which it is
needless to describe, since practice will necessarily suggest them;
though, like all other arts in which the hands and fingers are made use
of, it is only _much practice_ that can enable a person to go through
complex experiments, of this or any other kind, with ease and readiness.
For experiments in which air will bear to be confined by water, I first
used an oblong trough made of earthen ware, as _a_ fig. 1. about eight
inches deep, at one end of which I put thin flat stones, _b. b._ about
an inch, or half an inch, under the water, using more or fewer of them
according to the quantity of water in the trough. But I have since found
it more convenient to use a larger wooden trough, of the same general
shape, eleven inches deep, two feet long, and 1-1/2 wide, with a shelf
about an inch lower than the top, instead of the flat stones
above-mentioned. This trough being larger than the former, I have no
occasion to make provision for the water being higher or lower, the bulk
of a jar or two not making so great a difference as did before.
The several kinds of air I usually keep in _cylindrical jars_, as _c_,
_c_, fig. 1, about ten inches long, and 2-1/2 wide, being such as I have
generally used for electrical batteries, but I have likewise vessels of
very different forms and sizes, adapted to particular experiments.
When I want to remove vessels of air from the large trough, I place them
in _pots_ or _dishes_, of various sizes, to hold more or less water,
according to the time that I have occasion to keep the air, as fig. 2.
These I plunge in water, and slide the jars into them; after which they
may be taken out together, and be set wherever it shall be most
convenient. For the purpose of merely removing a jar of air from one
place to another, where it is not to stand longer than a few days, I
make use of common _tea-dishes_, which will hold water enough for that
time, unless the air be in a state of diminution, by means of any
process that is going on in it.
If I want to try whether an animal will live in any kind of air, I first
put the air into a small vessel, just large enough to give it room to
stretch itself; and as I generally make use of _mice_ for this purpose,
I have found it very convenient to use the hollow part of a tall
beer-glass, _d_ fig. 1, which contains between two and three ounce
measures of air. In this vessel a mouse will live twenty minutes, or
half an hour.
For the purpose of these experiments it is most convenient to catch the
mice in small wire traps, out of which it is easy to take them, and
holding them by the back of the neck, to pass them through the water
into the vessel which contains the air. If I expect that the mouse will
live a considerable time, I take care to put into the vessel something
on which it may conveniently sit, out of the reach of the water. If the
air be good, the mouse will soon be perfectly at its ease, having
suffered nothing by its passing through the water. If the air be
supposed to be noxious, it will be proper (if the operator be desirous
of preserving the mice for farther use) to keep hold of their tails,
that they may be withdrawn as soon as they begin to shew signs of
uneasiness; but if the air be thoroughly noxious, and the mouse happens
to get a full inspiration, it will be impossible to do this before it be
absolutely irrecoverable.
In order to _keep_ the mice, I put them into receivers open at the top
and bottom, standing upon plates of tin perforated with many holes, and
covered with other plates of the same kind, held down by sufficient
weights, as fig. 3. These receivers stand upon _a frame of wood_, that
the fresh air may have an opportunity of getting to the bottoms of them,
and circulating through them. In the inside I put a quantity of paper or
tow, which must be changed, and the vessel washed and dried, every two
or three days. This is most conveniently done by having another
receiver, ready cleaned and prepared, into which the mice may be
transferred till the other shall be cleaned.
Mice must be kept in a pretty exact temperature, for either much heat or
much cold kills them presently. The place in which I have generally kept
them is a shelf over the kitchen fire-place where, as it is usual in
Yorkshire, the fire never goes out; so that the heat varies very little,
and I find it to be, at a medium, about 70 degrees of Fahrenheit's
thermometer. When they had been made to pass through the water, as they
necessarily must be in order to a change of air, they require, and will
bear a very considerable degree of heat, to warm and dry them.
I found, to my great surprize, in the course of these experiments, that
mice will live intirely without water; for though I have kept them for
three or four months, and have offered them water several times, they
would never taste it; and yet they continued in perfect health and
vigour. Two or three of them will live very peaceably together in the
same vessel; though I had one instance of a mouse tearing another almost
in pieces, and when there was plenty of provisions for both of them.
In the same manner in which a mouse is put into a vessel of any kind of
air, a _plant_, or any thing else, may be put into it, viz. by passing
it through the water; and if the plant be of a kind that will grow in
water only, there will be no occasion to set it in a pot of earth, which
will otherwise be necessary.
There may appear, at first sight, some difficulty in opening the mouth
of a phial, containing any substance, solid or liquid, to which water
must not be admitted, in a jar of any kind of air, which is an operation
that I have sometimes had recourse to; but this I easily effect by means
of _a cork cut tapering_, and a strong, wire thrust through it, as in
fig. 4, for in this form it will sufficiently fit the mouth of any
phial, and by holding the phial in one hand, and the wire in the other,
and plunging both my hands into the trough of water, I can easily convey
the phial through the water into the jar; which must either be held by
an assistant, or be fastened by strings, with its mouth projecting over
the shelf. When the phial is thus conveyed into the jar, the cork may
easily be removed, and may also be put into it again at pleasure, and
conveyed the same way out again.
When any thing, as a gallipot, &c. is to be supported at a considerable
height within a jar, it is convenient to have such _wire stands_ as are
represented fig. 5. They answer better than any other, because they take
up but little room, and may be easily bended to any shape or height.
If I have occasion to pour air from a vessel with a wide mouth into
another with a very narrow one, I am obliged to make use of a funnel,
fig. 6, but by this means the operation is exceedingly easy; first
filling the vessel into which the air is to be conveyed with water, and
holding the mouth of it, together with the funnel, both under water with
one hand, while the other is employed in pouring the air; which,
ascending through the funnel up into the vessel, makes the water
descend, and takes its place. These funnels are best made of glass,
because the air being visible through them, the quantity of it may be
more easily estimated by the eye. It will be convenient to have several
of these funnels of different sizes.
In order to expel air from solid substances by means of heat, I
sometimes put them into a _gun-barrel_, fig. 7, and filling it up with
dry sand, that has been well burned, so that no air can come from it, I
lute to the open end the stem of a tobacco pipe, or a small glass tube.
Then having put the closed end of the barrel, which contains the
materials, into the fire, the generated air, issuing through the tube,
may be received in a vessel of quicksilver, with its mouth immersed in a
bason of the same, suspended all together in wires, in the manner
described in the figure: or any other fluid substance may be used
instead of quicksilver.
But the most accurate method of procuring air from several substances,
by means of heat, is to put them, if they will bear it, into phials full
of quicksilver, with the mouths immersed in the same, and then throw the
focus of a burning mirror upon them. For this purpose the phials should
be made with their bottoms round, and very thin, that they may not be
liable to break with a pretty sudden application of heat.
If I want to expel air from any liquid, I nearly fill a phial with it,
and having a cork perforated, I put through it, and secure with cement,
a glass tube, bended in the manner represented at _e_ fig. 1. I then put
the phial into a kettle of water, which I set upon the fire and make to
boil. The air expelled by the heat, from the liquor contained in the
phial, issues through the tube, and is received in the bason of
quicksilver, fig. 7. Instead of this suspended bason, I sometimes
content myself with tying a flaccid bladder to the end of the tube, in
both these processes, that it may receive the newly generated air.
In experiments on those kinds of air which are readily imbibed by water,
I always make use of quicksilver, in the manner represented fig. 8, in
which _a_ is the bason of quicksilver, _b_ a glass vessel containing
quicksilver, with its mouth immersed in it, _c_ a phial containing the
ingredients from which the air is to be produced; and _d_ is a small
recipient, or glass vessel designed to receive and intercept any liquor
that may be discharged along with the air, which is to be transmitted
free from any moisture into the vessel _b_. If there be no apprehension
of moisture, I make use of the glass tube only, without any recipient,
in the manner represented _e_ fig. 1. In order to invert the vessel _b_,
I first fill it with quicksilver, and then carefully cover the mouth of
it with a piece of soft leather; after which it may be turned upside
down without any danger of admitting the air, and the leather may be
withdrawn when it is plunged in the quicksilver.
In order to generate air by the solution of metals, or any process of a
similar nature, I put the materials into a phial, prepared in the manner
represented at _e_ fig. 1, and put the end of the glass tube under the
mouth of any vessel into which I want to convey the air. If heat be
necessary I can easily apply to it a candle, or a red hot poker while it
hangs in this position.
When I have occasion to transfer air from a jar standing in the trough
of water to a vessel standing in quicksilver, or in any other situation
whatever, I make use of the contrivance represented fig. 9, which
consists of a bladder, furnished at one end with a small glass tube
bended, and at the other with a cork, perforated so as just to admit the
small end of a funnel. When the common air is carefully pressed out of
this bladder, and the funnel is thrust tightly into the cork, it may be
filled with any kind of air as easily as a glass jar; and then a string
being tied above the cork in which the funnel is inserted, and the
orifice in the other cork closed, by pressing the bladder against it, it
may be carried to any place, and if the tube be carefully wiped, the air
may be conveyed quite free from moisture through a body of quicksilver,
or any thing else. A little practice will make this very useful
manoeuvre perfectly easy and accurate.
In order to impregnate fluids with any kind of air, as water with fixed
air, I fill a phial with the fluid larger or less as I have occasion (as
_a_ fig. 10;) and then inverting it, place it with its mouth downwards,
in a bowl _b_, containing a quantity of the same fluid; and having
filled the bladder, fig. 9, with the air, I throw as much of it as I
think proper into the phial, in the manner described above. To
accelerate the impregnation, I lay my hand on the top of the phial, and
shake it as much as I think proper.
If, without having any air previously generated, I would convey it into
the fluid immediately as it arises from the proper materials, I keep the
same bladder in connection with a phial _c_ fig. 10, containing the same
materials (as chalk, salt of tartar, or pearl ashes in diluted oil of
vitriol, for the generation of fixed air) and taking care, lest, in the
act of effervescence, any of the materials in the phial _c_ should get
into the vessel _a_, to place this phial on a stand lower than that on
which the bason was placed, I press out the newly generated air, and
make it ascend directly into the fluid. For this purpose, and that I may
more conveniently shake the phial _c_, which is necessary in some
processes, especially with chalk and oil of vitriol, I sometimes make
use of a flexible leathern tube _d_, and sometimes only a glass tube.
For if the bladder be of a sufficient length, it will give room for the
agitation of the phial; or if not, it is easy to connect two bladders
together by means of a perforated cork, to which they may both be
fastened.
When I want to try whether any kind of air will admit a candle to burn
in it, I make use of a cylindrical glass vessel, fig. 11. and a bit of
wax candle _a_ fig. 12, fastened to the end of a wire _b_, and turned
up, in such a manner as to be let down into the vessel with the flame
upwards. The vessel should be kept carefully covered till the moment
that the candle is admitted. In this manner I have frequently
extinguished a candle more than twenty times successively, in a vessel
of this kind, though it is impossible to dip the candle into it without
giving the external air an opportunity of mixing with the air in the
inside more or less. The candle _c_, at the other end of the wire is
very convenient for holding under a jar standing in water, in order to
burn as long as the inclosed air can supply it; for the moment that it
is extinguished, it may be drawn through the water before any smoke can
have mixed with the air.
In order to draw air out of a vessel which has its mouth immersed in
water, and thereby to raise the water to whatever height may be
necessary, it is very convenient to make use of a glass _syphon_, fig.
13, putting one of the legs up into the vessel, and drawing the air out
at the other end by the mouth. If the air be of a noxious quality, it
may be necessary to have a syringe fastened to the syphon, the manner of
which needs no explanation. I have not thought it safe to depend upon a
valve at the top of the vessel, which Dr. Hales sometimes made use of.
If, however, a very small hole be made at the top of a glass vessel, it
may be filled to any height by holding it under water, while the air is
issuing out at the hole, which may then be closed with wax or cement.
If the generated air will neither be absorbed by water, nor diminish
common air, it may be convenient to put part of the materials into a
cup, supported by a stand, and the other part into a small glass
vessel, placed on the edge of it, as at _f_, fig. 1. Then having, by
means of a syphon, drawn the air to at convenient height, the small
glass vessel may be easily pushed into the cup, by a wire introduced
through the water; or it may be contrived, in a variety of ways, only to
discharge the contents of the small vessel into the larger. The distance
between the boundary of air and water, before and after the operation,
will shew the quantity of the generated air. The effect of processes
that _diminish_ air may also be tried by the same apparatus.
When I want to admit a particular kind of air to any thing that will not
bear wetting, and yet cannot be conveniently put into a phial, and
especially if it be in the form of a powder, and must be placed upon a
stand (as in those experiments in which the focus of a burning mirror is
to be thrown upon it) I first exhaust a receiver, in which it is
previously placed; and having a glass tube, bended for the purpose, as
in fig. 14, I screw it to the stem of a transfer of the air pump on
which the receiver had been exhausted, and introducing it through the
water into a jar of that kind of air with which I would fill the
receiver, I only turn the cock, and I gain my purpose. In this method,
however, unless the pump be very good, and several contrivances, too
minute to be particularly described, be made use of a good deal of
common air will get into the receiver.
When I want to measure the goodness of any kind of air, I put two
measures of it into a jar standing in water; and when I have marked upon
the glass the exact place of the boundary of air and water, I put to it
one measure of nitrous air; and after waiting a proper time, note the
quantity of its diminution. If I be comparing two kinds of air that are
nearly alike, after mixing them in a large jar, I transfer the mixture
into a long glass tube, by which I can lengthen my scale to what degree
I please.
If the quantity of the air, the goodness of which I want to ascertain,
be exceedingly small, so as to be contained in a part of a glass tube,
out of which water will not run spontaneously, as _a_ fig. 15; I first
measure with a pair of compasses the length of the column of air in the
tube, the remaining part being filled with water, and lay it down upon a
scale; and then, thrusting a wire of a proper thickness, _b_, into the
tube, I contrive, by means of a thin plate of iron, bent to a sharp
angle _c_, to draw it out again, when the whole of this little
apparatus has been introduced through the water into a jar of nitrous
air; and the wire being drawn out, the air from the jar must supply its
place. I then measure the length of this column of nitrous air which I
have got into the tube, and lay it also down upon the scale, so as to
know the exact length of both the columns. After this, holding the tube
under water, with a small wire I force the two separate columns of air
into contact, and when they have been a sufficient time together, I
measure the length of the whole, and compare it with the length of both
the columns taken before. A little experience will teach the operator
how far to thrust the wire into the tube, in order to admit as much air
as he wants and no more.
In order to take the electric spark in a quantity of any kind of air,
which must be very small, to produce a sensible effect upon it, in a
short time, by means of a common machine, I put a piece of wire into the
end of a small tube, and fasten it with hot cement, as in fig. 16; and
having got the air I want into the tube by means of the apparatus fig.
15, I place it inverted in a bason containing either quicksilver, or any
other fluid substance by which I chuse to have the air confined. I then,
by the help of the air pump, drive out as much of the air as I think
convenient, admitting the quicksilver, &c. to it, as at _a_, and
putting a brass ball on the end of the wire, I take the sparks or shocks
upon it, and thereby transmit them through the air to the liquor in the
tube.
To take the electric sparks in any kind of fluid, as oil, &c. I use the
same apparatus described above, and having poured into the tube as much
of the fluid as I conjecture I can make the electric spark pass through,
I fill the rest with quicksilver; and placing it inverted in a bason of
quicksilver, I take the sparks as before.
If air be generated very fast by this process, I use a tube that is
narrow at the top, and grows wider below, as fig. 17, that the
quicksilver may not recede too soon beyond the striking distance.
Sometimes I have used a different apparatus for this purpose,
represented fig. 18. Taking a pretty wide glass tube, hermetically
sealed at the upper-end, and open below, at about an inch, or at what
distance I think convenient from the top, I get two holes made in it,
opposite to each other. Through these I put two wires, and fastening
them with warm cement, I fix them at what distance I please from each
other. Between these wires I take the sparks, and the bubbles of air
rise, as they are formed, to the top of the tube.
PART I.
_Experiments and Observations made in, and before the year 1772._
In writing upon the subject of _different kinds of air_, I find myself
at a loss for proper _terms_, by which to distinguish them, those which
have hitherto obtained being by no means sufficiently characteristic, or
distinct. The only terms in common use are, _fixed air_, _mephitic_, and
_inflammable_. The last, indeed, sufficiently characterizes and
distinguishes that kind of air which takes fire, and explodes on the
approach of flame; but it might have been termed _fixed_ with as much
propriety as that to which Dr. Black and others have given that
denomination, since it is originally part of some solid substance, and
exists in an unelastic state.
All these newly discovered kinds of air may also be called _factitious_;
and if, with others, we use the term _fixable_, it is still obvious to
remark, that it is applicable to them all; since they are all capable of
being imbibed by some substance or other, and consequently of being
_fixed_ in them, after they have been in an elastic state.
The term _mephitic_ is equally applicable to what is called _fixed air_,
to that which is _inflammable_, and to many other kinds; since they are
equally noxious, when breathed by animals. Rather, however, than either
introduce new terms, or change the signification of old ones, I shall
use the term _fixed air_, in the sense in which it is now commonly used,
and distinguish the other kinds by their properties, or some other
periphrasis. I shall be under a necessity, however, of giving names to
those kinds of air, to which no names had been given by others, as
_nitrous_, _acid_, and _alkaline_.
SECTION I.
_Of FIXED AIR._
It was in consequence of living for some time in the neighbourhood of a
public brewery, that I was induced to make experiments on fixed air, of
which there is always a large body, ready formed, upon the surface of
the fermenting liquor, generally about nine inches, or a foot in depth,
within which any kind of substance may be very conveniently placed; and
though, in these circumstances, the fixed air must be continually mixing
with the common air, and is therefore far from being perfectly pure, yet
there is a constant fresh supply from the fermenting liquor, and it is
pure enough for many purposes.
A person, who is quite a stranger to the properties of this kind of air,
would be agreeably amused with extinguishing lighted candles, or chips
of wood in it, as it lies upon the surface of the fermenting liquor; for
the smoke readily unites with this kind of air, probably by means of the
water which it contains; so that very little or none of the smoke will
escape into the open air, which is incumbent upon it. It is remarkable,
that the upper surface of this smoke, floating in the fixed air, is
smooth, and well defined; whereas the lower surface is exceedingly
ragged, several parts hanging down to a considerable distance within the
body of the fixed air, and sometimes in the form of balls, connected to
the upper stratum by slender threads, as if they were suspended. The
smoke is also apt to form itself into broad flakes, parallel to the
surface of the liquor, and at different distances from it, exactly like
clouds. These appearances will sometimes continue above an hour, with
very little variation. When this fixed air is very strong, the smoke of
a small quantity of gunpowder fired in it will be wholly retained by it,
no part escaping into the common air.
Making an agitation in this air, the surface of it, (which still
continues to be exactly defined) is thrown into the form of waves, which
it is very amusing to look upon; and if, by this agitation, any of the
fixed air be thrown over the side of the vessel, the smoke, which is
mixed with it, will fall to the ground, as if it was so much water, the
fixed air being heavier than common air.
The red part of burning wood was extinguished in this air, but I could
not perceive that a red-hot poker was sooner cooled in it.
Fixed air does not instantly mix with common air. Indeed if it did, it
could not be caught upon the surface of the fermenting liquor. A candle
put under a large receiver, and immediately plunged very deep below the
surface of the fixed air, will burn some time. But vessels with the
smallest orifices, hanging with their mouths downwards in the fixed air,
will _in time_ have the common air, which they contain, perfectly mixed
with it. When the fermenting liquor is contained in vessels close
covered up, the fixed air, on removing the cover, readily affects the
common air which is contiguous to it; so that, candles held at a
considerable distance above the surface will instantly go out. I have
been told by the workmen, that this will sometimes be the case, when the
candles are held two feet above the mouth of the vessel.
Fixed air unites with the smoke of rosin, sulphur, and other electrical
substances, as well as with the vapour of water; and yet, by holding the
wire of a charged phial among these fumes, I could not make any
electrical atmosphere, which surprized me a good deal, as there was a
large body of this smoke, and it was so confined, that it could not
escape me.
I also held some oil of vitriol in a glass vessel within the fixed air,
and by plunging a piece of red-hot glass into it, raised a copious and
thick fume. This floated upon the surface of the fixed air like other
fumes, and continued as long.
Considering the near affinity between water and fixed air, I concluded
that if a quantity of water was placed near the yeast of the fermenting
liquor, it could not fail to imbibe that air, and thereby acquire the
principal properties of Pyrmont, and some other medicinal mineral
waters. Accordingly, I found, that when the surface of the water was
considerable, it always acquired the pleasant acidulous taste that
Pyrmont water has. The readiest way of impregnating water with this
virtue, in these circumstances, is to take two vessels, and to keep
pouring the water from one into the other, when they are both of them
held as near the yeast as possible; for by this means a great quantity
of surface is exposed to the air, and the surface is also continually
changing. In this manner, I have sometimes, in the space of two or three
minutes, made a glass of exceedingly pleasant sparkling water, which
could hardly be distinguished from very good Pyrmont, or rather Seltzer
water.
But the _most effectual_ way of impregnating water with fixed air is to
put the vessels which contain the water into glass jars, filled with
the purest fixed air made by the solution of chalk in diluted oil of
vitriol, standing in quicksilver. In this manner I have, in about two
days, made a quantity of water to imbibe more than an equal bulk of
fixed air, so that, according to Dr. Brownrigg's experiments, it must
have been much stronger than the best imported Pyrmont; for though he
made his experiments at the spring-head, he never found that it
contained quite so much as half its bulk of this air. If a sufficient
quantity of quicksilver cannot be procured, _oil_ may be used with
sufficient advantage, for this purpose, as it imbibes the fixed air very
slowly. Fixed air may be kept in vessels standing in water for a long
time, if they be separated by a partition of oil, about half an inch
thick. Pyrmont water made in these circumstances, is little or nothing
inferior to that which has stood in quicksilver.
The _readiest_ method of preparing this water for use is to agitate it
strongly with a large surface exposed to the fixed air. By this means
more than an equal bulk of air may be communicated to a large quantity
of water in the space of a few minutes. But since agitation promotes the
dissipation of fixed air from water, it cannot be made to imbibe so
great a quantity in this method as in the former, where more time is
taken.
Easy directions for impregnating water with fixed air I have published
in a small pamphlet, designed originally for the use of seamen in long
voyages, on the presumption that it might be of use for preventing or
curing the sea scurvy, equally with wort, which was recommended by Dr.
Macbride for this purpose, on no other account than its property of
generating fixed air, by its fermentation in the stomach.
Water thus impregnated with fixed air readily dissolves iron, as Mr.
Lane has discovered; so that if a quantity of iron filings be put to it,
it presently becomes a strong chalybeate, and of the mildest and most
agreeable kind.
I have recommended the use of _chalk_ and oil of vitriol as the
cheapest, and, upon the whole, the best materials for this purpose. But
some persons prefer _pearl ashes_, _pounded marble_, or other calcareous
or _alkaline substances_; and perhaps with reason. My own experience has
not been sufficient to enable me to decide in this case.
Whereas some persons had suspected that a quantity of the oil of vitriol
was rendered volatile by this process, I examined it, by all the
chemical methods that are in use; but could not find that water thus
impregnated contained the least perceivable quantity of that acid.
Mr. Hey, indeed, who assisted me in this examination, found that
distilled water, impregnated with fixed air, did not mix so readily with
soap as the distilled water itself; but this was also the case when the
fixed air had passed through a long glass tube filled with alkaline
salts, which, it may be supposed, would have imbibed any of the oil of
vitriol that might have been contained in that air[2].
Fixed air itself may be said to be of the nature of an acid, though of a
weak and peculiar sort.----Mr. Bergman of Upsal, who honoured me with a
letter upon the subject, calls it the _aerial acid_, and, among other
experiments to prove it to be an acid, he says that it changes the blue
juice of tournesole into red. This Mr. Hey found to be true, and he
moreover discovered that when water tinged blue with the juice of
tournesole, and then red with fixed air, has been exposed to the open
air, it recovers its blue colour again.
The heat of boiling water will expel all the fixed air, if a phial
containing the impregnated water be held in it; but it will often
require above half an hour to do it completely.
Dr. Percival, who is particularly attentive to every improvement in the
medical art, and who has thought so well of this impregnation as to
prescribe it in several cases, informs me that it seems to be much
stronger, and sparkles more, like the true Pyrmont water, after it has
been kept some time. This circumstance, however, shews that, in time,
the fixed air is more easily disengaged from the water; and though, in
this state, it may affect the taste more sensibly, it cannot be of so
much use in the stomach and bowels, as when the air is more firmly
retained by the water.
By the process described in my pamphlet, fixed air may be readily
incorporated with wine, beer, and almost any other liquor whatever; and
when beer, wine, or cyder, is become flat or dead (which is the
consequence of the escape of the fixed air they contained) they may be
revived by this means; but the delicate and agreeable flavour, or
acidulous taste, communicated by fixed air, and which is very manifest
in water, can hardly be perceived in wine, or any liquors which have
much taste of their own.
I should think that there can be no doubt, but that water thus
impregnated with fixed air must have all the medicinal virtues of
genuine Pyrmont or Seltzer water; since these depend upon the fixed air
they contain. If the genuine Pyrmont water derives any advantage from
its being a natural chalybeate, this may also be obtained by providing a
common chalybeate water, and using it in these processes, instead of
common water.
Having succeeded so well with this artificial Pyrmont water, I imagined
that it might be possible to give _ice_ the same virtue, especially as
cold is known to promote the absorption of fixed air by water; but in
this I found myself quite mistaken. I put several pieces of ice into a
quantity of fixed air, confined by quicksilver, but no part of the air
was absorbed in two days and two nights; but upon bringing it into a
place where the ice melted, the air was absorbed as usual.
I then took a quantity of strong artificial Pyrmont water, and putting
it into a thin glass phial, I set it in a pot that was filled with snow
and salt. This mixture instantly freezing the water that was contiguous
to the sides of the glass, the air was discharged plentifully, so that
I catched a considerable quantity, in a bladder tied to the mouth of the
phial.
I also took two quantities of the same Pyrmont water, and placed one of
them where it might freeze, keeping the other in a cold place, but where
it would not freeze. This retained its acidulous taste, though the phial
which contained it was not corked; whereas the other being brought into
the same place, where the ice melted very slowly, had at the same time
the taste of common water only. That quantity of water which had been
frozen by the mixture of snow and salt, was almost as much like snow as
ice, such a quantity of air-bubbles were contained in it, by which it
was prodigiously increased in bulk.
The pressure of the atmosphere assists very considerably in keeping
fixed air confined in water; for in an exhausted receiver, Pyrmont water
will absolutely boil, by the copious discharge of its air. This is also
the reason why beer and ale froth so much _in vacuo_. I do not doubt,
therefore, but that, by the help of a condensing engine, water might be
much more highly impregnated with the virtues of the Pyrmont spring; and
it would not be difficult to contrive a method of doing it.
The manner in which I made several experiments to ascertain the
absorption of fixed air by different fluid substances, was to put the
liquid into a dish, and holding it within the body of the fixed air at
the brewery, to set a glass vessel into it, with its mouth inverted.
This glass being necessarily filled with the fixed air, the liquor would
rise into it when they were both taken into the common air, if the fixed
air was absorbed at all.
Making use of _ether_ in this manner, there was a constant bubbling from
under the glass, occasioned by this fluid easily rising in vapour, so
that I could not, in this method, determine whether it imbibed the air
or not. I concluded however, that they did incorporate, from a very
disagreeable circumstance, which made me desist from making any more
experiments of the kind. For all the beer, over which this experiment
was made, contracted a peculiar taste; the fixed air impregnated with
the ether being, I suppose, again absorbed by the beer. I have also
observed, that water which remained a long time within this air has
sometimes acquired a very disagreeable taste. At one time it was like
tar-water. How this was acquired, I was very desirous of making some
experiments to ascertain, but I was discouraged by the fear of injuring
the fermenting liquor. It could not come from the fixed air only.
Insects and animals which breathe very little are stifled in fixed air,
but are not soon quite killed in it. Butterflies and flies of other
kinds will generally become torpid, and seemingly dead, after being held
a few minutes over the fermenting liquor; but they revive again after
being brought into the fresh air. But there are very great varieties
with respect to the time in which different kinds of flies will either
become torpid in the fixed air, or die in it. A large strong frog was
much swelled, and seemed to be nearly dead, after being held about six
minutes over the fermenting liquor; but it recovered upon being brought
into the common air. A snail treated in the same manner died presently.
Fixed air is presently fatal to vegetable life. At least sprigs of mint
growing in water, and placed over the fermenting liquor, will often
become quite dead in one day, or even in a less space of time; nor do
they recover when they are afterwards brought into the common air. I am
told, however, that some other plants are much more hardy in this
respect.
A red rose, fresh gathered, lost its redness, and became of a purple
colour, after being held over the fermenting liquor about twenty-four
hours; but the tips of each leaf were much more affected than the rest
of it. Another red rose turned perfectly white in this situation; but
various other flowers of different colours were very little affected.
These experiments were not repeated, as I wish they might be done, in
pure fixed air, extracted from chalk by means of oil of vitriol.
For every purpose, in which it was necessary that the fixed air should
be as unmixed as possible, I generally made it by pouring oil of vitriol
upon chalk and water, catching it in a bladder fastened to the neck of
the phial in which they were contained, taking care to press out all the
common air, and also the first, and sometimes the second, produce of
fixed air; and also, by agitation, making it as quickly as I possibly
could. At other times, I made it pass from the phial in which it was
generated through a glass tube, without the intervention of any bladder,
which, as I found by experience, will not long make a sufficient
separation between several kinds of air and common air.
I had once thought that the readiest method of procuring fixed air, and
in sufficient purity, would be by the simple process of burning chalk,
or pounded lime-stone in a gun-barrel, making it pass through the stem
of a tobacco-pipe, or a glass tube carefully luted to the orifice of it.
In this manner I found that air is produced in great plenty; but, upon
examining it, I found, to my very great surprise, that little more than
one half of it was fixed air, capable of being absorbed by water; and
that the rest was inflammable, sometimes very weakly, but sometimes
pretty highly so.
Whence this inflammability proceeds, I am not able to determine, the
lime or chalk not being supposed to contain any other than fixed air. I
conjecture, however, that it must proceed from the iron, and the
separation of it from the calx may be promoted by that small quantity of
oil of vitriol, which I am informed is contained in chalk, if not in
lime-stone also.
But it is an objection to this hypothesis, that the inflammable air
produced in this manner burns blue, and not at all like that which is
produced from iron, or any other metal, by means of an acid. It also has
not the smell of that kind of inflammable air which is produced from
mineral substances. Besides, oil of vitriol without water, will not
dissolve iron; nor can inflammable air be got from it, unless the acid
be considerably diluted; and when I mixed brimstone with the chalk,
neither the quality nor the quantity of the air was changed by it.
Indeed no air, or permanently elastic vapour, can be got from brimstone,
or any oil.
Perhaps this inflammable principle may come from some remains of the
animals, from which it is thought that all calcareous matter proceeds.
In the method in which I generally made the fixed air (and indeed
always, unless the contrary be particularly mentioned, viz. by diluted
oil of vitriol and chalk) I found by experiment that it was as pure as
Mr. Cavendish made it. For after it had patted through a large body of
water in small bubbles, still 1/50 or 1/60 part only was not absorbed by
water. In order to try this as expeditiously as possible, I kept pouring
the air from one glass vessel into another, immersed in a quantity of
cold water, in which manner I found by experience, that almost any
quantity may be reduced as far as possible in a very short time. But the
most expeditious method of making water imbibe any kind of air, is to
confine it in a jar; and agitate it strongly, in the manner described in
my pamphlet on the impregnation of water with fixed air, and represented
fig. 10.
At the same time that I was trying the purity of my fixed air, I had the
curiosity to endeavour to ascertain whether that part of it which is not
miscible in water, be equally diffused through the whole mass; and, for
this purpose, I divided a quantity of about a gallon into three parts,
the first consisting of that which was uppermost, and the last of that
which was the lowest, contiguous to the water; but all these parts were
reduced in about an equal proportion, by passing through the water, so
that the whole mass had been of an uniform composition. This I have also
found to be the case with several kinds of air, which will, not properly
incorporate.
A mouse will live very well, though a candle will not burn in the
residuum of the purest fixed air that I can make; and I once made a very
large quantity for the sole purpose of this experiment. This, therefore,
seems to be one instance of the generation of genuine common air, though
vitiated in some degree. It is also another proof of the residuum of
fixed air being, in part at least, common air, that it becomes turbid,
and is diminished by the mixture of nitrous air, as will be explained
hereafter.
That fixed air only wants some addition to make it permanent, and
immiscible with water if not in all respects, common air, I have been
led to conclude, from several attempts which I once made to mix it with
air in which a quantity of iron filings and brimstone, made into a paste
with water, had stood; for, in several mixtures of this kind, I imagined
that not much more than half of the fixed air could be imbibed by water;
but, not being able to repeat the experiment, I conclude that I either
deceived myself in it, or that I overlooked some circumstance on which
the success of it depended.
These experiments, however, whether they were fallacious or otherwise,
induced me to try whether any alteration would be made in the
constitution of fixed air, by this mixture of iron filings and
brimstone. I therefore put a mixture of this kind into a quantity of as
pure fixed air as I could make, and confined the whole in quicksilver,
lest the water should absorb it before the effects of the mixture could
take place. The consequence was, that the fixed air was diminished, and
the quicksilver rose in the vessel, till about the fifth part was
occupied by it; and, as near as I could judge, the process went on, in
all respects, as if the air in the inside had been common air.
What is most remarkable, in the result of this experiment, is, that the
fixed air, into which this mixture had been put, and which had been in
part diminished by it, was in part also rendered insoluble in water by
this means. I made this experiment four times, with the greatest care,
and observed, that in two of them about one sixth, and in the other two
about one fourteenth, of the original quantity, was such as could not be
absorbed by water, but continued permanently elastic. Lest I should have
made any mistake with respect to the purity of the fixed air, the last
time that I made the experiment, I set part of the fixed air, which I
made use of, in a separate vessel, and found it to be exceedingly pure,
so as to be almost wholly absorbed by water; whereas the other part, to
which I had put the mixture, was far from being so.
In one of these cases, in which fixed air was made immiscible with
water, it appeared to be not very noxious to animals; but in another
case, a mouse died in it pretty soon. This difference probably arose
from my having inadvertently agitated the air in water rather more in
one case than in the other.
As the iron is reduced to a calx by this process, I once concluded, that
it is phlogiston that fixed air wants, to make it common air; and, for
any thing I yet know this may be the case, though I am ignorant of the
method of combining them; and when I calcined a quantity of lead in
fixed air, in the manner which will be described hereafter, it did not
seem to have been less soluble in water than it was before.
FOOTNOTES:
[2] An account of Mr. Hey's experiments will be found in the Appendix to
these papers.