TRANSCRIBER’S NOTE
Italic text is denoted by _underscores_.
Some minor changes to the text are noted at the end of the book.
AN
ESSAY
ON
_COMBUSTION_,
WITH A VIEW TO A
NEW ART
OF
DYING AND PAINTING.
WHEREIN
THE PHLOGISTIC AND ANTIPHLOGISTIC HYPOTHESES
ARE PROVED ERRONEOUS.
BY MRS. FULHAME.
LONDON:
PRINTED FOR THE AUTHOR,
BY J. COOPER, BOW STREET, COVENT GARDEN,
And Sold by J. JOHNSON, No. 72, St. Paul’s Church Yard;
G. G. and J. ROBINSON, Paternoster Row; and
T. CADELL, Jun. and W. DAVIES, Strand.
1794.
[ENTERED AT STATIONERS HALL.]
PREFACE.
The possibility of making cloths of gold, silver, and other metals, by
chymical processes, occurred to me in the year 1780: the project being
mentioned to Doctor Fulhame, and some friends, was deemed improbable.
However, after some time, I had the satisfaction of realizing the idea,
in some degree, by experiment.
Animated by this small success, I have, from time to time, ever since,
prosecuted the subject as far as pecuniary circumstances would permit.
I imagined in the beginning, that a few experiments would determine the
problem; but experience soon convinced me, that a very great number
indeed were necessary, before such an art could be brought to any
tolerable degree of perfection.
A narration of the numerous experiments, which I made with this view,
would far exceed the bounds, I prescribe myself in this essay; I shall
therefore present the reader only with a few, selecting such as I judge
most interesting, and best adapted to illustrate the subject.
Though I was, after some considerable time, able to make small bits of
cloth of gold, and silver, yet I did not think them worthy of public
attention; but by persevering, I at length succeeded in making pieces
of gold cloth, as large as my finances would admit.
Some time after this period, I found the invention was applicable
to painting, and would also contribute to facilitate the study of
geography: for I have applied it to some maps, the rivers of which I
represented in silver, and the cities in gold. The rivers appearing, as
it were, in silver streams, have a most pleasing effect on the sight,
and relieve the eye of that painful search for the course, and origin,
of rivers, the minutest branches of which can be splendidly represented
in this way.
Notwithstanding this further success, I was dubious about the propriety
of publishing this Essay; I therefore shewed some specimens of these
metallic stuffs to persons, whom I thought qualified to judge of them:
some approved of them very much, and were pleased to say, that the
invention would make an era in the arts; others thought it a pretty
conceit; and others were of opinion, that the stuffs had not that
splendour, or burnished appearance, which could entitle them to public
notice.
The latter opinion had much weight with me; for it must be allowed,
that the specimens, which I shewed them, had not that lustre and
polish, necessary for shoulder-knots, lace, spangles, gold muslins,
&c.; that some of them had a reddish cast, bordering on the colour of
copper, some a purple, mixed with gold; and that some of them were
unequal in the die, and seemed stained; which imperfections were owing
to a partial reduction of the metal in the fibres of the silk.
But all these imperfections, except the want of that burnished lustre
so necessary for gold lace, spangles, &c. I knew I could remedy; and
therefore the criticism, as far as it relates to them, had no great
influence with me.
I am in possession of some pieces, one of which is about a yard in
length, which have scarce any of these imperfections.
Moreover, that high polish of burnished gold, so necessary in spangles,
lace, &c., would, in my opinion, be a great imperfection in gold stuffs
designed for whole suits; as a person in such a habit, would look like
a gilded statue.
I saw a piece of gold stuff made for the late King of Spain, which was
of a purple colour, with gold wire shining through it, though rather
obscurely; and it was much admired: I was so struck with its beauty,
that I attempted to imitate it on a small bit of white silk; and
succeeded, having produced a beautiful purple colour, with gold beaming
through it.
Therefore, the want of that burnished appearance is no objection to
this art; for the paler, and cooler, to a certain degree, the colour of
the gold is, the more lovely do these metallic cloths appear.
I made small bits of gold tiffany, which looked exceedingly beautiful;
the fineness of the thread contributing much to that effect; and, in my
opinion, such webs are inimitable by mechanical means.
Beside, though I am not able to make cloths like burnished gold, others
of greater means and abilities may; for we cannot pretend to prescribe
any limits to the perfection, at which chymistry, and the arts, may
arrive.
However, I must acknowledge, that this unfavourable judgement suspended
my intention of publishing this little work, until a celebrated
philosopher happening, some time in October 1793, to see some of the
same pieces, and indeed, some of the worst, viewed the performance in a
very different light.
This illustrious friend of science not only approved of the specimens
shewn him, but offered to have a memoir on the subject presented to the
Royal Society: but different incidents dissuaded me from that mode of
publication, and induced me to adopt the present.
I now no longer hesitated about the propriety of publishing; for,
every thing considered, I judged, that though this art could never
be established, which is by no means my opinion, yet the experiments
themselves, upon which I attempted to found it, as they are new, and
seem to throw some light on the theory of combustion, are not unworthy
the attention of Chymists.
Those who viewed my performance with a favourable eye, were of opinion,
that I should dedicate this Essay to some patron of the arts; or
apply for his Majesty’s Royal letters patent, in order to reimburse
the expence necessarily incurred in this investigation, an expence so
disproportionate to the fortune which supported it, that nothing but a
certain fatality, and the hope of reward, could induce me to persevere.
As to patrons, I have heard of such beings on the record of fame; but
never saw one: on the contrary, it has been my lot to know of many,
whose malignant breath, as far as its deadly influence can extend,
never ceases to blast the unsheltered blossoms of science.—And as for a
patent, had I even the means, I should perhaps never attempt it; for if
we may judge of the future by the past, I can safely affirm, that such
an application would be vain.
Thus circumstanced, I publish this Essay in its present imperfect
state, in order to prevent the furacious attempts of the prowling
plagiary, and the insidious pretender to chymistry, from arrogating to
themselves, and assuming my invention, in plundering silence: for there
are those, who, if they can not by chymical, never fail by stratagem,
and mechanical means, to deprive industry of the fruits, and fame, of
her labours.
But the British empire should not forget, that she owes her power and
greatness to commerce; that she is, as it were, the hive of the arts,
and should not, by the sulphureous vapour of oppression, and neglect,
compel her bees to swarm for protection to foreign climes, but rather
permit them to roam in their native soil, and allow them, in the winter
of life, to sip a little of the honey of their own industry.
The nation, whose evil genius withholds this protection, only sounds
the trumpet of emigration; and must erelong lament her cities deserted,
her fields brown with desolation, and herself the easy prey, and vile
drudge of surrounding greatness.
I first imagined, that the proper title of this performance, should
be, an Essay on the Art of making Cloths of Gold, Silver, and other
Metals, by chymical processes; but reflecting on the imperfect state
of the art, and that my experiments related not only to the reduction,
but also to the calcination of metals, and other combustible bodies, I
determined to entitle it, An Essay on Combustion, with a view to a new
Art of Dying and Painting, which includes every thing the experiments
can extend to.
As to the style, I have endeavoured to relate the experiments in a
plain and simple manner, aiming more at perspicuity, than elegance.
I have adopted the French Nomenclature, as the terms of it are so
framed, as to prevent circumlocution, assist the memory, by pointing
out the combination, and state of the elements existing in each
compound, as far as they are known; advantages to be found in no other
Nomenclature.
However, the English reader must regret, that the French chymists have
not preferred the terms _air_, and _ammonia_, to the less harmonious
sounds, _gas_, and _ammoniac_. I took the liberty of writing the latter
_ammonia_.
I have not related my experiments in the order, in which they were
made, sensible that such a narration would be tedious, and that a short
extract from them would answer every purpose at present intended.
The experiments related I have endeavoured to arrange in such a manner,
as mutually to illustrate each other, by contrasting the successful
with those, that failed, thus pointing out a general principle, which
forms a chain through the whole, connects all the experiments, shows
their points of coincidence, and disagreement, and by this means
furnishes us with _data_, by which, I hope, the art may be improved.
This arrangement also facilitates the perusal, and relieves the mind
of that fatiguing attention, which must necessarily be given to an
indigested mass of insulated experiments, that have no clew to connect
them, but has, on the other hand, its disadvantages; for it throws a
sameness on the work, incompatible with that variety which is often so
agreeable.
My apparatus consisted chiefly of a few glass vessels for the solution
of metals, and the formation of such elastic fluids, as I used. The
cheapest, and the most simple of those described by Dr. Priestley
answered my purpose.
Dr. Nooth’s machine for combining carbonic acid with water, is very
convenient for making small experiments with some kinds of gas; as the
base of that machine serves to contain the materials, from which the
gas is obtained; and the middle glass the cloth previously dipped in
the metallic solution, on which the experiment is to be made.
The cloth may be suspended in this part of the machine, by means of a
thread, and a cork.
As this machine is useful only in experiments on a very small scale, I
sometimes used tall glass cylinders, in which I suspended the subject
of the experiment, by means of a thread, a cork, and a bit of cement.
This cylinder I placed over a vessel containing the materials, which
produced the gas.
It is very convenient to have cylinders of different sizes,
proportioned to the scale, on which the experiments are to be made.
But machinery for confining elastic fluids is not always necessary; as
most of the experiments may be performed in the open air.
It may appear presuming to _some_, that I should engage in pursuits of
this nature, but averse from indolence, and having much leisure, my
mind led me to this mode of amusement, which I found entertaining, and
will, I hope, be thought inoffensive by the liberal, and the learned.
But censure is perhaps inevitable; for some are so ignorant, that they
grow sullen and silent, and are chilled with horror at the sight of any
thing, that bears the semblance of learning, in whatever shape it may
appear; and should the _spectre_ appear in the shape of _woman_, the
pangs, which they suffer, are truly dismal.
There are others, who suffer the same torture in a still higher degree;
but by virtue of an _old inspiring tripod_, on which ignorance,
servility, or chance, has placed them, assume a dictatorship in
science, and fancying their rights and prerogatives invaded, swell with
rage, and are suddenly seized with a violent and irresistible desire
of revenge, manifesting itself by innuendos, nods, whispers, sneers,
grins, grimace, satanic smiles, and witticisms uttered sometimes in
the acute, and sometimes in the nasal obtuse twang, with an affected
hauteur, and contempt of the _spectre_; shrugs, and a variety of other
contortions, attending.
Sometimes the goblin, which thus agitates them, lurks latent, and
nothing is perceived but hollow murmurs, portending storms: sometimes
the lurking fiend darts with sidelong fury at the devoted object,
which, if unarmed, falls a victim to the grisly monster.
But happily for human kind, the _magic tripod_ drags none into its
dizzy vortex, but those who are radically stupid, and malicious, who
are the beasts of prey destined to hunt down unprotected genius, to
stain the page of biography, or to rot unnoted in the grave of oblivion.
Although the surge of deliberate malice be unavoidable, its force is
often spent in froth, and bubbles; for this little bark of mine has
weathered out full many a storm, and stemmed the boisterous tide; and
though the cargo be not rich, the dangers, which may hereafter be
pourtrayed on _votive tablet_, may serve as a beacon to future mariners.
But happen what may, I hope I shall never experience such desertion of
mind, as not to hold the helm with becoming fortitude against the storm
raised by ignorance, petulant arrogance, and privileged dulness.
However, were I not encouraged by the judgement of some friends, and
possessed of specimens, to show the progress made in the art, I should
never perhaps venture to publish this Essay; as I am sensible, it
labours under many imperfections, which inaccuracy of observation, and
the drapery of imagination, must spread over the whole, imperfections
perhaps unavoidable in such a discussion.
Finding, the experiments could not be explained on any theory hitherto
advanced, I was led to form an opinion different from that of M.
Lavoisier, and other great names. Persuaded that we are not to be
deterred from the investigation of truth by any authority however
great, and that every opinion must stand or fall by its own merits,
I venture with diffidence to offer mine to the world, willing to
relinquish it, as soon as a more rational appears.
November 5th, 1794.
CONTENTS.
Introduction 1
Chap. I. Reduction of Metals by Hydrogen Gas 13
---- II. ------------------- Phosphorus 41
---- III. ------------------- Sulphur 69
---- IV. ------------------- Alkaline Sulphure 84
---- V. ------------------- Sulphurated Hydrogen
Gas 99
---- VI. ------------------- Phosphorated Hydrogen
Gas 113
---- VII. ------------------- Charcoal 124
---- VIII. ------------------- Light 142
---- IX. ------------------- Acids 155
---- X. Oxygenation of Combustible Bodies 161
-------------- Azote ibid.
-------------- Hydrogen 164
-------------- Phosphorus 165
-------------- Sulphur 166
-------------- Charcoal ibid.
-------------- Metals 169
-------------- Light 168, 169
---- XI. Conclusion 178
Nomenclature 181
INTRODUCTION.
Though some of the phenomena of combustion were known from the earliest
ages, yet no rational attempt to explain them was made till about the
middle of the 17th century.
Before that period, it was supposed by alchymists and physicians, that
sulphur was the inflammable principle, on which all the phenomena of
combustion depended.
But Beecher perceiving, that sulphur did not exist in several
combustible bodies, asserted it was not the principle of
inflammability; which, he maintained, was a different substance, common
to sulphur and other combustible bodies: this principle he supposed to
be of a dry nature, and called it inflammable Earth.
Stahl refined this hypothesis by supposing the inflammable earth of
Beccher to be pure fire, fixed in combustible bodies, and constituting
an essential part of them.
According to Stahl, a combustible body is a compound, containing fixed
fire, or _phlogiston_; and combustion is the disengagement of this
phlogiston from a fixed to a free state, attended sometimes with heat
and light: when these phenomena cease, the body becomes incombustible;
if this calcined body be now heated with charcoal, or any other
inflammable substance, capable of giving it phlogiston, or fixed fire,
it returns again to the class of inflammable bodies.
This hypothesis is so simple and plausible, that, since the year 1736,
it was received, though differently modified, all over Europe.
The principal objections to it are, that the existence of phlogiston
cannot be demonstrated; and that it does not explain, why bodies become
heavier after oxygenation, and lighter after reduction.
M. Lavoisier discovering, that the increase of weight, which bodies
acquire during combustion, is equal to the weight of the combustible
substance, and that of the vital air employed, denied the existence
of phlogiston, or fixed fire, in combustible bodies; though he grants
the existence of combined _caloric_ in them. He seems then to allow
the existence of phlogiston, but to have changed its name to that of
_caloric_, and denied it the power of producing combustion.
However, after discovering that the increase of weight, which bodies
acquire during combustion, depended on the quantity of the air
absorbed, he was led to the following beautiful hypothesis, equally
simple as that of Stahl; and if ever any hypothesis deserved the name
of theory, surely it is that of M. Lavoisier.
According to M. Lavoisier, “an inflammable body is nothing else but
a body which has the property of decomposing vital air, and taking
the base from caloric and light; that is to say, the oxygene, which
was united to them; and that a body ceases to be combustible when its
affinity for the oxygene is satisfied, or when it is saturated with
that principle; but that it becomes again combustible, when the oxygene
has been taken from it by another body, which has a stronger affinity
with that principle.
“When this decomposition of the air is rapid, and, as it were,
instantaneous, there is an appearance of flame, heat, and light; when,
on the contrary, the decomposition is very slow, and quietly made, the
heat and light are scarcely perceptible[1].”
Thus all the phenomena of oxygenation, which Stahl ascribed to the
disengagement of phlogiston, M. Lavoisier ascribes to the union of
oxygen with combustible bodies.
And, on the other hand, all the phenomena of reduction, which Stahl
attributed to the union of phlogiston to calcined bodies, M. Lavoisier
attributes to the separation of oxygen from the same. Combustion,
then, according to Stahl, is the transition of phlogiston from one
body to another; and, according to M. Lavoisier, ’tis nothing but the
transition of oxygen from one substance to another.
Stahl supposed, that the heat, and light, attending combustion proceed
from the burning body; but M. Lavoisier supposes, that the heat, and
light, proceed principally, and almost entirely, from the vital air.
However, this opinion of M. Lavoisier is far from being established;
for Doctor Crawford has shown, that inflammable air contains a much
greater quantity of heat, than vital air does.
It is evident, then, that the great advantage, which M. Lavoisier’s
hypothesis has over that of Stahl is, that the former seems to account
for the increase and decrease of weight, which bodies suffer during
calcination, and reduction.
Notwithstanding this brilliant discovery, which seems to account, with
such ease, for the increase of weight, that bodies acquire during
combustion, M. Macquer was of opinion, that M. Lavoisier’s hypothesis
was insufficient to explode that of Stahl, and endeavoured to remove
the objection urged against the nonexistence of phlogiston, by
supposing it to be light; and that in every case of combustion, light,
and vital air, mutually precipitate each other: so that, according
to M. Macquer, when a body is oxygenated, vital air unites to it, and
disengages light; and, on the other hand, when an oxygenated substance
is reduced to its inflammable state, light unites to it, and disengages
vital air.
M. Scheele also modified the hypothesis of Stahl, by supposing that
heat, light, and inflammable air, were compounds of empyreal, or vital
air, and phlogiston. Light, he thought, contained more phlogiston than
heat did; and inflammable air more than either: he farther supposed,
that these compounds of vital air and phlogiston were convertible
into one another, by the addition, or subtraction, of phlogiston; and
that, when a metal was reduced by them, they were decomposed; their
phlogiston uniting to the substance reduced.
His idea of calcination is, that metals either attract empyreal air by
means of their phlogiston, and thus form heat, or that they communicate
their phlogiston to the air, and attract heat from the fire; and that,
either way, there is empyreal air in the calces, which makes the
overplus of their weight[2].
The last modification of Stahl’s hypothesis is that of M. Kirwan, who
supposes that inflammable air exists in a fixed, or concrete, state
in all combustible bodies, and is the true phlogiston of the antient
chymists; and, as it can be exhibited in the form of air, its existence
is no longer doubtful.
M. Kirwan supposes, that, when combustible bodies are calcined, or
changed into acids, they combine most commonly with fixed air, formed
during the operation, by the union of their phlogiston to vital air;
and sometimes to other substances, and water, which is either absorbed
_in specie_, or formed by the union of their phlogiston to vital air,
during calcination.
He supposes, that some of these are restored to their combustible
state by the decomposition of their fixed air; some partly by the
decomposition of their fixed air, and partly by its expulsion, and
that of the other foreign bodies, they had absorbed; and lastly, that
some recover their combustibility by the expulsion of water, and
others possibly by its decomposition in high degrees of heat. In all
these reductions he supposes a simultaneous reunion of these bodies to
phlogiston, or the inflammable principle[3].
Though M. Kirwan’s hypothesis seems to account for the increase
of weight, which bodies acquire during combustion, yet he has not
proved the existence of inflammable air, in a concrete state, in all
combustible bodies; nor has he shown, that fixed air is a compound of
inflammable, and vital air; neither has he proved, that fixed air is
the acidifying principle.
All these objections have been made, with great justice, to his
hypothesis, by the antiphlogistians; who also object, that M. Kirwan’s
account of calcination, and reduction, is complex, and repugnant to the
simplicity of nature; “for,” says M. De Fourcroy, “as the author had
admitted three general species of calcination, it was necessary, that
he should, likewise, admit three kinds of reduction[4].”
This criticism is very just; but it will appear, that the
antiphlogistic account of calcination, and reduction, is no less
complex, erroneous, and repugnant to the simplicity of nature: for when
we consider the various sources, whence they derive the oxygen, which
oxygenates bodies; and the long list of metallic reducers, which they
suppose; it must be allowed, that if simplicity be a recommendation,
their hypothesis is destitute of that advantage.
Thus, according to M. Lavoisier, the oxygen, which oxygenates
combustible bodies, is sometimes derived from vital air; sometimes
from atmospheric air; sometimes from acids; sometimes from water; and
sometimes from metallic oxids, &c.
On the other hand, the catalogue of substances, which reduce bodies to
their combustible state, is no less numerous.
“Heat,” says M. De Fourcroy, “separates oxygene from some; one metal
takes it from another; hydrogene, or inflammable gas, takes it from
most metals; and carbone perhaps from all[5].”
To this list, may be added phosphorus, sulphur, and compounds of these
with hydrogen; also light, and the electric fluid, &c., as will appear
in the sequel.
But, I shall endeavour to show, that the hydrogen of water is the only
substance, that restores oxygenated bodies to their combustible state;
and that water is the only source of the oxygen, which oxygenates
combustible bodies.
Want of simplicity is not the only defect in Mr. Lavoisier’s
hypothesis: for he supposes, that the increase of weight, which bodies
acquire during combustion, depends on the absorption of the oxygenous
principle alone.
Thus, when a bit of phosphorus, sulphur, or charcoal, is burnt in vital
air; the increase of weight, which these bodies acquire, he attributes
entirely to oxygen, or the base of vital air.
These combustions he explains, by supposing, that the phosphorus,
sulphur, and charcoal, decompose oxygen gas, by absorbing its base
from caloric, and light, which are set free.
“There is,” says M. Lavoisier, “a total absorption of vital air, or
rather of the oxygene, which forms its base in the combustion of
phosphorus, and the weight of the phosphoric acid obtained, is found to
be rigorously equal to the weight of the phosphorus, added to that of
the vital air employed in its combustion. The same agreement of weights
is observed in the combustion of inflammable gas and vital air, in the
combustion of charcoal[6]”, &c.
His idea of the calcination of metals is the same.
“We do not,” says M. Lavoisier, “affirm that vital air combines with
metals to form metallic calces, because this manner of enunciating
would not be sufficiently accurate: but we say, when a metal is heated
to a certain temperature, and when its particles are separated from
each other to a certain distance by heat, and their attraction to each
other is sufficiently diminished, it becomes capable of decomposing
vital air, from which it seizes the base, namely oxygene, and sets the
other principle, namely caloric, at liberty.
“This explanation of what passes during the calcination is not an
hypothesis, but the result of facts. It is upwards of twelve years,
since the proofs have been laid by one of us, before the eyes of the
academy, and have been verified by a numerous commission. It was then
established, that when the calcination of metals is effected beneath
an inverted glass vessel, or in closed vessels containing known
quantities of air, the air itself is decomposed, and the weight of the
metal becomes augmented by a quantity accurately equal to that of the
air absorbed. It has since been found, that when the operation was
performed in very pure vital air, the whole might be absorbed.”
“No supposition enters into these explanations; the whole is proved by
weight and measure[7].”
Hence it is evident, that M. Lavoisier confounds oxygen with oxygen
gas; and considers the latter as a compound of oxygen, light, and
caloric.
But since the dryest oxygen gas contains a large proportion of water,
as Dr. Priestley and M. Kirwan have shown[8]; and since the whole of
the gas, except the caloric, and light, is absorbed, it necessarily
follows, that the increase of weight, which bodies acquire during
combustion, depends not only on the oxygen, but also on the water,
contained in vital air.
Therefore oxids are compounds of combustible bodies united to oxygen,
and water.
Another great objection to M. Lavoisier’s hypothesis, is, that he
supposes both oxygenation, and reduction, effected by a single affinity.
Thus, according to him, when iron reduces a sulphate of copper, the
iron does nothing more, than separate the oxygen from the copper, by
its superior attraction for that principle.
From this view of combustion, grounded on the most accurate experiments
in chymistry, it is manifest, that the antiphlogistic hypothesis does
not account fully for the increase of weight, which bodies acquire
during combustion; and consequently, that it cannot be admitted as a
just theory.
CHAPTER I.
REDUCTION OF METALS
BY
HYDROGEN GAS.
As Hydrogen, or the base of inflammable air, seems to act an important
part in the following experiments, and is, according to some chymists,
pure phlogiston itself; I have therefore assigned the first chapter in
this essay to hydrogen gas, this being the most simple form, in which
hydrogen has hitherto been obtained.
But I had not the means of procuring this gas free of carbone, and
other impurities, that it dissolves and elevates during its formation;
or of excluding atmospheric air, which circumstances, I am sensible,
must, in some measure, influence the result; as it cannot be supposed,
that these extraneous bodies would remain inactive during the process
of reduction. However, as such exactness is not in the power of every
experimenter, I was under a necessity of using hydrogen gas, with the
disadvantages here mentioned.
Though most of the experiments in this essay were made on a variety of
white and coloured silks, I shall relate only those made on the former,
as it exhibits the changes produced more distinctly, and contains less
foreign matter to modify the result of experiment; and, for brevity’s
sake, I shall use the term _silk_, by which _white silk_ is always
designed.
EXP. 1. GOLD.
I poured a quantity of sulphuric ether on a solution of gold in
nitro-muriatic acid, and, by this means, obtained a solution of gold in
ether, which I separated from the acid.
In this ethereal solution of gold, I dipped a piece of silk, after it
was taken out, and the ether evaporated, it was suspended in a tall
glass cylinder, placed over a vessel, containing a mixture of diluted
sulphuric acid, and iron filings.
The silk thus exposed to a rapid current of hydrogen gas acquired,
after some time, a purple colour, and a large spangle of gold, of an
irregular figure, appeared on the upper end of the silk, and looked
very brilliant.
The silk was kept exposed to the gas about four months, and frequently
observed, but no other remarkable change was perceived, except
that the purple colour became more intense: the experiment was now
discontinued; and on taking out the silk, and examining it in the light
of the sun, I observed many particles of reduced gold; but they were
very small, and by no means so brilliant, as that, which first appeared.
During the experiment, fresh quantities of materials for supplying
hydrogen gas were occasionally added.
From the brilliant spangle of reduced gold observed in this experiment,
I concluded, that there was a sufficient quantity of the metal in the
fibres of the silk, could it be reduced.
This spot of reduced gold was very permanent, and adhered firmly to the
silk.
EXP. 2. GOLD.
In order to determine, whether a solution of gold in ether, or one
in water, were best adapted to the object of these experiments; I
evaporated to dryness a solution of gold in nitro-muriatic acid, and
dissolved the salt in distilled water: in this solution, I immersed a
piece of silk, which, after it was dried in the air, was suspended in
a glass cylinder, like the former piece, and exposed to the action of
hydrogen gas about two months.
The silk after some time assumed a purple colour, and five or six
specks of reduced gold, of the size of pin heads, and one much larger,
were observed. Examining the silk in the sun-beams, I perceived the
whole of it spangled with minute particles of reduced gold.
After many experiments with these two solutions of gold, I was led to
conclude, that the solution in water answered best.
EXP. 3. SILVER.
Having dissolved some pure silver in diluted nitric acid, and
evaporated some of the water by a gentle heat, I placed it in the dark
to crystallize. The crystals were separated from the solution, and
dissolved in distilled water; to one measure of this solution, which
was saturated with the nitrate of silver, ten or twelve measures of
distilled water were added.
In this diluted solution, a piece of silk was dipped; after it was
taken out, it was dried at the fire: the silk dried in this manner,
retained its white colour; whereas, were it dried gradually in the air;
and especially, were the light considerable, its white colour would
be changed to a reddish brown, more or less intense, according to the
quantity of light present.
Some kinds of silk, on being immersed in a solution of nitrate of
silver, have some of their threads immediately coloured brown: but I
often got white silk, which would retain its pure white colour, if
dried at the fire, or in the dark.
The piece of silk dried, as above, was suspended in the middle glass of
Dr. Nooth’s machine; and into the lower glass were introduced a diluted
solution of sulphuric acid, and some small iron nails.
The machine was now placed in a dark closet, to exclude the action of
light; after some time, the silk, thus exposed to hydrogen gas, put
on a light brown colour, which gradually became deeper, until it was
changed to a disagreeable black, with some mixture of brown: then very
small particles of reduced silver began to appear, which increased by
degrees, in number, and brightness.
The experiment was continued four months; after which time, the silk
was taken out of the machine: it had a gray metallic appearance,
intermixed with a considerable tinge of brown.
This experiment was repeated on another piece of silk, every
circumstance being the same, except that a quantity of water was put in
the middle glass of the machine, over which the silk was suspended; the
intention of interposing the water in this experiment was to purify the
gas.
The appearances were much the same, as in the last experiment; except
that the silk became black sooner; and that some spangles of the
silver were larger, and better reduced.
The specks of reduced silver were permanent, and adhered firmly to the
silk.
EXP. 4. LEAD.
In a solution of acetite of lead in distilled water I dipped a piece of
silk, and dried it in the air; it was then suspended over a quantity of
water in Dr. Nooth’s machine, and exposed to hydrogen gas about three
months.
The appearances were much the same as in the last experiment, except
that the silk was not so black: the particles of reduced lead resembled
silver.
Similar experiments were made in this machine on bits of silk imbued
with a solution of nitro-muriate of gold in water; but the appearances
being much the same as those mentioned in the first and second
experiments, it is unnecessary to repeat them here.
It is much easier to imagine, than express my anxiety, to discover
the cause of the brilliant specks of reduced gold and silver, with
which the pieces of silk in these experiments were sometimes spangled;
concluding, that were the cause ascertained, it would be a considerable
step towards accomplishing the object in view.
But many and diversified were the experiments I made before the
circumstance, on which these spangles depended, was perceived.
At length, I found it depended on the presence of moisture; and that
the spangles of reduced metal were owing to small drops of water
carried up by the elastic fluid, and deposited on the silk.
The experiments, which led to this conclusion, shall be related in
their proper places. I shall now proceed to recite the remainder of the
experiments in this essay, conformable to the plan laid down in the
preface, premising an occurrence observed in the course of them.
I sometimes found, that the production of hydrogen gas from a mixture
of acid, water, and iron nails, would unexpectedly stop, which induced
me to add more acid; this not succeeding, I added more water; but
still no gas was formed: the proportions of acid and water were varied
without effect. Thinking the mixture of acid and water unfit for the
purpose, I poured it off, and repeatedly washed and agitated the nails
with more water, which was also poured off; but happening inadvertently
to add some of the mixture of acid and water, which I had before poured
off as unfit for use, I was surprised to find the gas produced with
great rapidity.
Reflecting on the cause of this odd circumstance, I concluded that it
depended on a crust of superoxygenated iron, formed on the surface of
the nails, which defended them from the action of the water and acid,
and that this crust was removed by the agitation and washing, which
enabled the diluted acid to act again on the iron.
EXP. 5. GOLD.
I immersed a bit of silk in a solution of nitro-muriate of gold in
distilled water, and dried it in the air; it was then placed over a
cylindrical glass vessel, containing a mixture of diluted sulphuric
acid and iron nails, for about half an hour; but no reduction of the
metal could be observed.
I dipped another bit of silk in the same solution of gold, and exposed
it, while wet, to the same current of hydrogen gas, and instantly
signs of reduction appeared; for the yellow colour, which the solution
imparts to silk, began to change to a green, and very soon a film of
reduced gold glittered on the surface opposed to the gas: shortly
after, a beautiful blue spot, fringed with orange and purple, was
formed on the middle of the silk. During the experiment, which lasted
about half an hour, the silk was kept constantly wet with distilled
water.
When experiments are made with this preparation of gold, it is
necessary to evaporate the solution to dryness, before the salt be
dissolved in the water; as an excess of acid prevents the reduction in
a great measure. Solutions of gold in these experiments do not admit of
being so largely diluted, as solutions of silver, and other metals do.
EXP. 6. SILVER.
I immersed a piece of silk in a solution of nitrate of silver, and
dried it in a dark place; it was then exposed to a current of hydrogen
gas about twenty minutes; but no reduced silver appeared, the only
change observable was a brown stain.
I immersed another bit of the same silk in the same solution of
silver, and having exposed it, while wet, to a stream of hydrogen gas,
I soon observed evident signs of reduction; the white colour of the
silk was changed to a brown, which became gradually more intense; and
the surface of the silk, opposed to the gas, was coated with reduced
silver: various colours, as blue, purple, red, orange, and yellow,
attended the reduction. These colours often change, and are succeeded
by others in the progress of the reduction. The threads of the silk
look like silver wire, tarnished in some parts, but of great lustre in
others.
The silk was kept wet with distilled water during the experiment. When
the silk happened to be too much wetted, the under surface opposed to
the gas was often covered with scales of a dull blue colour: these,
after the silk dries, may be brushed off, and another coat of reduced
silver, which adheres firmly, but has no considerable brightness, is
left behind.
These experiments on the reduction of gold, and silver, were often
repeated with nearly the same result.
EXP. 7. SILVER.
Thinking some other preparation of silver might answer better than a
nitrate, I precipitated some of the latter with a solution of muriate
of soda, and poured the whole on a filter; the precipitate was well
washed with distilled water, and dissolved in ammonia. In this solution
I immersed a piece of silk, and dried it in the air; and having
exposed it to the action of hydrogen gas, I could perceive no signs of
reduction, except a faint brown colour.
I dipped another bit of silk in the same solution of silver, and in
order to determine if water had the power of promoting the reduction of
the silver in this preparation, as it had in the former experiments, I
exposed the silk, while wet, to the same current of hydrogen gas; and
in a few seconds the metallic lustre was evident on the surface opposed
to the current. After some little time, a blue speck and a faint trace
of yellow appeared, but soon vanished.
This preparation of silver does not stain white silk so much as a
nitrate does; the reduced silver was indeed very brilliant, but soon
grew dull, and disappeared; a brown stain only remaining; so that
it seems rather inferior to nitrate of silver, which also, after
reduction, tarnishes, grows dull, and often disappears; but sometimes
part of it remains permanently reduced.
EXP. 8. PLATINA.
With much difficulty I procured a small quantity of the ore of platina,
and dissolved it in nitro-muriatic acid. The solution was evaporated to
dryness, and the salt was then dissolved in distilled water.
A bit of silk was dipped in part of this solution, and dried in the
air; it was then exposed to a brisk current of hydrogen gas about
twenty minutes, but no signs of reduction appeared.
Another bit of silk was immersed in the solution of platina, and
exposed, while wet, to the same current of hydrogen gas; in five or
six minutes the platina was reduced, exhibiting a livid white metallic
appearance on the surface of the silk opposed to the current. No
colours attended the reduction. This solution imparts a yellowish brown
colour to silk.
After some time, the whole of the metallic lustre disappeared, in
proportion as the silk became dry.
The solution of platina requires more time, and a stronger current of
hydrogen gas for its reduction, than solutions of silver and gold do.
EXP. 9. MERCURY.
I immersed a bit of silk in a solution of oxygenated muriate of mercury
in distilled water, and dried it in the air: it was then exposed to a
stream of hydrogen gas; but underwent no visible change.
I dipped another bit of silk in the same solution of mercury, and
exposed it, while wet, to the same current of gas; the metal was soon
reduced in a beautiful manner, and resembled silver.
The reduction began suddenly, with scarce any appearance of previous
stain; some very faint, but at the same time transparent colours
attended it: the most remarkable of these were a light orange, with a
fringe of blue, and a yellow verging on a faint green. These colours
soon disappeared.
After the silk was turned, I observed, that its texture was, in some
parts, concealed by a thin film, which, as the reduction proceeded,
was perceived to dart along the threads of the silk, gilding them in a
beautiful manner, and exhibiting the texture very distinctly.
After some time, the mercury seemed to disappear, so as to render it
doubtful whether any of it remained in the silk; but shaking it in the
sunbeams, I perceived bright atoms fly off; and rubbing the silk on a
bit of blue paper, I observed shining metallic particles, which seemed
to have lost their affinity of aggregation, for they did not unite.
One remarkable difference between this preparation of mercury and
nitrate of silver, is, that no black or brown stain preceded, attended,
or followed, the reduction of the mercury.
Mr. Scheele reduced a prussiate of mercury, dissolved in water, by
adding iron filings and a small quantity of sulphuric acid to the
solution[9].
EXP. 10. COPPER.
A piece of silk was immersed in a solution of sulphate of copper, then
taken out, and dried, and exposed for a considerable time to a brisk
current of hydrogen gas; but no signs of reduction could be perceived.
Another bit of silk was dipped in the same solution of copper, and
exposed, while wet, to the same rapid current of hydrogen gas; the
appearances were the following.
After a minute, or two, the silk assumed a faint brown colour, and, on
the surface opposed to the gas, a white metallic pellicle appeared,
which vanished in proportion as the silk became dry: wetting the silk
again, I perceived a similar pellicle appear, which also vanished, as
soon as the silk dried. If the silk be kept constantly wet, the brown
colour becomes much more intense, attended with a very slight tinge of
red. The margins of the silk projecting beyond the verge of the glass
cylinder, and therefore not exposed to the current of the gas, retained
the blue colour, which the solution imparts.
In some of these white metallic pellicles there appeared a faint brown
inclining to yellow, which reflected the light, though obscurely.
After the silk dried, nothing remained, but a brown stain.
EXP. 11. LEAD.
A piece of silk was immersed in a solution of acetite of lead in
distilled water; it was then dried, and exposed for some time to a
stream of hydrogen gas; but underwent no perceptible change.
Another bit of silk was dipped in the same solution of lead, and
exposed, while wet, to the same current of hydrogen gas; in a second,
or two, the surface of the silk, opposed to the current, was coated
with reduced lead, which looked like silver.
The reduction was accompanied with a brown stain, but by no means so
intense as that, which attends the reduction of nitrate of silver.
The other side of the silk was opposed to the current of hydrogen gas,
and soon acquired a metallic coat of the same brilliant appearance,
exhibiting the texture of the silk, in a very striking manner.
It is remarkable, that lead exhibits no colour, but a light brown,
during its reduction; whereas gold, silver, and mercury, display a
great variety of colours, especially the two former.
After some time the lead reduced in this manner loses its metallic
splendour considerably; and that in proportion as the silk dries.
EXP. 12. TIN.
I dissolved some crystals of muriate of tin in distilled water; dipped
a bit of silk in the solution; and dried it in the air: it was then
exposed to a stream of hydrogen gas a considerable time; but no change,
or appearance of reduction, could be observed.
Another bit of silk was immersed in the same solution of tin, and
exposed, while wet, to the same current of gas; after some little time,
the reduction commenced, attended with a great variety of beautiful
colours; as red, yellow, orange, green, and blue, variously intermixed.
The reduced tin disappears along with these colours, as the silk dries;
nothing remaining but a feuille-morte colour.
The same solution of tin was also reduced by hydrogen gas, obtained
from tin, and the muriatic acid.
These experiments do not succeed well with muriate of tin containing an
excess of acid.
EXP. 13. ARSENIC.
A muriate of arsenic, which was prepared by digesting white oxid of
arsenic in muriatic acid, and continuing the heat, till most of the
acid evaporated, and left behind a soft mass of the consistence of tar,
was dissolved in distilled water.
In this solution a bit of silk was immersed, and dried in the air: it
was exposed to a brisk stream of hydrogen gas, obtained from zinc, and
muriatic acid; but no reduction took place.
Another bit of silk was dipped in the same solution, and exposed, while
wet, to the same current of hydrogen gas; and instantly, the surface of
the silk, opposed to the gas, was covered with a bright coat of reduced
arsenic, accompanied with a yellow stain. In a short time the metallic
lustre vanished; and nothing remained but the yellow stain.
M. Pelletier restored the acid of arsenic to its metallic state, by
passing hydrogen gas through a solution of that acid, in twice its
weight of water[10].
EXP. 14. BISMUTH.
A bit of silk, which was immersed in a solution of nitrate of bismuth
in distilled water, and exposed dry to hydrogen gas, obtained from
zinc, and muriatic acid, underwent no visible change.
Another bit of silk was dipped in the same solution of bismuth, and
placed over a languid stream of hydrogen gas; the bismuth was soon
restored to its metallic form, on the surface of the silk opposed to
the elastic fluid. The reduction was attended with a reddish brown
stain, intermixed with a tinge of violet.
EXP. 15. ANTIMONY.
A bit of silk was immersed in a solution of tartarite of antimony in
distilled water; and dried in the air. It was then exposed to hydrogen
gas, obtained from zinc, and muriatic acid; but suffered no visible
alteration.
Another bit of silk, which was dipped in the same solution of antimony,
was exposed wet to a weak stream of the gas; and, in a short time, the
metallic lustre appeared, accompanied by a light yellow colour.
EXP. 16. IRON.
A bit of silk, which was immersed in a largely diluted solution of
sulphate of iron, and dried in the air, was exposed to a strong
current of hydrogen gas, obtained from iron nails, and diluted
sulphuric acid; but no visible change was produced on the silk.
Another bit of silk was dipped in the same solution of iron, and placed
wet over the same stream of hydrogen gas; but no reduced iron could be
perceived. The silk was then immersed in a glass of clear water, and
transferred a very minute metallic film to the surface of that fluid.
This experiment was repeated with a rapid current of hydrogen gas,
obtained from zinc, and muriatic acid; and, in about a minute, small
films of reduced iron were visible on the surface of the silk, opposed
to the gas.
The silk was then immerged in water, and transferred to its surface a
large metallic pellicle; parts of which were very brilliant; but other
parts were dull, and much more imperfectly reduced.
EXP. 17. ZINC.
A bit of silk, which was dipped in a muriate of zinc, largely diluted
with water, and dried in the air, was exposed to a rapid current of
hydrogen gas, obtained from zinc, and muriatic acid; but suffered no
visible alteration.
Another piece of silk was immersed in the same solution of zinc, and
exposed, while wet, to the same rapid current of hydrogen gas: in
about half a minute, the metal was reduced in a very evident manner, on
part of the silk. The silk was then dipped in a glass of clear water,
and transferred a bright metallic film to its surface.
As these reductions of iron, and zinc, by hydrogen, are contrary to M.
Lavoisier’s table of the affinities of the oxygenous principle; I began
to suspect, that the films, which were so evident, both on the silk,
and the water, might be abraded, or torn from the zinc, by the muriatic
acid; and elevated, and deposited on the silk by the gas.
In order to remove this doubt, I dipped a bit of the same silk in
distilled water; and exposed it, while wet, to the same current of
hydrogen gas, but nothing metallic could be seen on the silk; nor did
it when immersed in water transfer a film, or the smallest appearance
of a metal, to the surface of that fluid: and, therefore, there can be
no doubt of the reality of these reductions.
Dr. Priestley restored iron, and lead, to their metallic state, by
heating their oxids with a burning glass in hydrogen gas.
These experiments point out an error in M. Bergman’s table of elective
attractions in the humid way; for he assigned the last place in that
table to phlogiston, which he considered as the base of inflammable
air; because he was unacquainted with any metallic reductions effected
by hydrogen in the humid way[11].
Having found, that water promoted, and accelerated, these reductions in
a very remarkable manner; I was curious to know, if alcohol, and ether,
would produce the same effect. With this view, I evaporated a solution
of gold in nitro-muriatic acid to dryness; when the vessel cooled, some
alcohol was poured on to dissolve the salt; and immediately the vessel
containing the salt, became so hot, that it could be scarcely endured
by the hand; and diffused a fragrant smell, like that of ether, which,
no doubt, was a species of that fluid.
EXP. 18. GOLD.
In this solution of gold in alcohol, a bit of silk was dipped, and
exposed to a stream of hydrogen gas, obtained from diluted sulphuric
acid, and iron nails; and kept wet with alcohol: in about two minutes,
the silk began to assume a brown colour, and white metallic films
appeared on some parts of the surface opposed to the gas; some of these
disappeared in a short time; and were succeeded by a few very small
spangles of the proper colour of gold. These also soon vanished; and
nothing remained but a disgreeable brown stain, intermixed with specks
of a dull blue.
I sometimes found, on repeating this experiment, that no yellow films
or spangles appeared; and am persuaded, that their appearance, and
that of the white pellicles also, depends on the presence of water,
contained in the alcohol, or the gas, and deposited on the silk.
EXP. 19. GOLD.
A bit of silk was immersed in a solution of gold in ether, and exposed
to a stream of hydrogen gas, and kept wet with ether. The silk
underwent no alteration for a few minutes; at length, it began to
assume a faint brown colour, but no white, or yellow films appeared.
If this experiment be continued till the silks collects a sufficient
quantity of water from the gas, some films will appear.
EXP. 20. SILVER.
I procured some nitrate of silver, which had been fused in order to
expell as much of its water as possible; and dissolved it in alcohol. I
immersed a bit of silk in this solution, and exposed it to a stream of
hydrogen gas, and kept it wet with alcohol: in a few seconds, the silk
assumed a brown colour, which gradually became more intense: but no
reduced silver appeared for several minutes; at length, a few metallic
films appeared on part of the surface opposed to the gas.
EXP. 21. MERCURY.
A bit of silk was dipped in a solution of oxygenated muriate of
mercury, and dried; it was then exposed to hydrogen gas about ten or
fifteen minutes, and kept constantly wet with alcohol. The silk, during
the first minutes, suffered no perceptible alteration: at length, a few
small films were visible on the side of the silk opposed to the current.
EXP. 22. LEAD.
A bit of silk, which was immersed in a solution of acetite of lead,
and dried, was exposed about fifteen minutes to a stream of the gas;
and kept constantly wet with alcohol; but suffered no visible change;
except that a very minute film was reduced on one of its margins, which
did not project beyond the verge of the glass vessel on which it was
placed.
When we compare these experiments with those, in which water was
used, to wet the silk, ’tis evident, that alcohol, and ether, do not
promote the reduction of metals, as water does; and that the few films,
which appear, when the silk is kept wet with ether or alcohol, depend
entirely on water collected from the gas, or deposited by them on the
silk during their evaporation.
In order to compare the effects of hydrogen gas, obtained from water,
iron nails, and muriatic acid, with that, procured from the same
materials, by means of the sulphuric; I made some experiments on gold,
silver, mercury, and lead, in the same manner, as the preceding; and
the principal difference was, that the colours produced in all the
pieces of silk, except that, which was dipped in acetite of lead,
were much brighter, and more beautiful, than any produced, when the
sulphuric acid was used.
The reduction of the lead was accompanied with its usual brown colour.
On the upper surface of a bit of silk, which was dipped in a solution
of gold, a green colour instantly appeared; and soon changed to a deep
olive, in proportion as the reduction advanced: now examining the
under surface, I saw it coated with a bright film of reduced gold, in
the middle of which a blue spangle, mixed with purple, soon began to
appear: I then moistened the upper surface of the silk with water; and
in a few seconds, it also was coated with reduced gold.
The blue on the other side of the silk became much more intense: the
piece was now turned; and on each colour I let fall a drop of water:
the drop on the blue had a blue film, the drop on the purple, had a
purple film, and the drop on the yellow, a film of reduced gold.
After some time, these drops of water evaporated, and the films came
again in contact with the silk: some parts of which were left bare, as
generally happens, when too much water is applied.
On the under surface of a bit of silk, which was immersed in a solution
of nitrate of silver in water, a coat of reduced metal was formed, with
various colours, as green, blue, orange, and yellow, the beauty and
brightness of which were remarkable.
In some time a muriate of silver is formed in the fibres of the silk,
which on exposure to light becomes of a bluish black colour: but the
whole of the silver does not undergo this change; for part of it
remains in its metallic state. The colours remain a considerable time,
if the silk be removed from the gas before this muriate is formed.
Hence it appears, that hydrogen gas should not be prepared with an
acid, which forms an insoluble compound with the metal to be reduced.
I also found, that hydrogen gas produces different effects not only
according to the difference of the acid, but also according to the
difference of the metal employed to obtain it: for this gas procured
from zinc or tin, and muriatic acid, did not restore gold to its proper
metallic lustre; but formed on the silk, a white metalline coat like
silver.
The experiments related in this chapter indicate the following
conclusions.
1. Hydrogen is capable of reducing the metals in the ordinary
temperature of the atmosphere.
2. Water promotes, and accelerates, these reductions, in a very
remarkable manner.
3. Ether, and alcohol, do not promote these reductions, without the aid
of water.
4. A variety of colours accompanies these reductions, similar to what
appears, during the calcination of metals by heat and air; and depends
on the same cause: viz. the quantity of oxygen combined with the metal.
These colours have not been observed hitherto; nor indeed could they;
as the metals were reduced in close vessels, and in high degrees of
heat.
5. These reductions often disappear.
This is commonly owing to an imperfect, and partial reduction of the
metal: for the acid, and water, remaining in that part of the metallic
solution, not reduced, recalcines these delicate films: sometimes the
disappearance of the metallic lustre depends on the nature of the
metal itself: thus arsenic, lead, silver, &c., suffer some degree of
calcination by water and atmospheric air.
Messrs. Bergman and Keir relate instances, in which silver after being
precipitated in its metallic state, was recalcined, and disappeared.
I first imagined, that water promoted these reductions by minutely
dividing the particles of the metallic salt, and by condensing the
gas, and bringing its hydrogen, and the metallic oxid, within the
sphere of attraction; the hydrogen either uniting to the metallic
earth and reducing it, as the Phlogistians suppose; or uniting with,
and separating the oxygen of the metal, and thus restoring it to the
metallic form, as the Antiphlogistians maintain.
But it is evident from the experiments related, that water does not
promote these reductions solely, by minutely dividing the particles of
the metallic salt: for were this the case; ether, and alcohol, should
promote the reduction of the metallic salts, which they dissolve, since
they divide their particles, as minutely as water can.
Since then metallic solutions in ether, and alcohol, cannot be reduced
by hydrogen gas; it follows that the above supposition concerning the
mode of agency of water does not account for the reduction of metals in
this way.
And indeed were it true that hydrogen condensed by water reduced metals
in the manner above mentioned, it would follow, that the reduction was
effected by a single affinity, which cannot be admitted; 1st. because
the existence of a single affinity in such cases has not been proved;
2dly, because a double affinity always takes place in preference to
a single affinity, which is demonstrated by the following facts,
transcribed from the works of Mr. Kirwan.
“If a solution of silver in the nitrous acid be thrown into a mixed
solution of fixed alkali and common salt, the silver will be
precipitated by the marine acid of the common salt, and not by the free
alkali, contained in the liquor: for a luna cornea is found[12].”
“I repeated the experiment with a solution of lead, and also of mercury
in the nitrous acid, and the result was similar: both lead and marine
salt of mercury were formed[13].”
In these experiments of Messrs. Monnet and Kirwan, ’tis evident that
a double affinity takes place in preference to a single one: for the
nitrous acid of these different nitrates unites with the alkali of the
common salt, while the muriatic acid of the latter seizes the silver,
mercury, and lead, of the nitrates, and forms muriates of silver,
mercury, and lead: the free alkali remaining passive in the mixture.
M. Lavoisier says, “There exists only in nature, as far as we can
observe them, cases of double affinity, often triple, and others
perhaps still more complicated[14].”
Now as water does not promote these reductions merely by dissolving,
and minutely dividing, the particles of the metallic salts, and
condensing the hydrogen gas; and since a double affinity takes place in
preference to a single affinity; it is obvious that the water must be
decomposed in these reductions in the following manner.
The hydrogen of the gas unites to the oxygen of the water, while the
hydrogen of the latter unites in its nascent state to the oxygen of the
metal, reduces it, and forms water.
Thus what could never be effected by a single, is readily performed by
a double affinity.
Hence it follows, that the hydrogen of the gas is oxygenated by the
oxygen of the water, while the metal is, at the same time, restored
to its combustible state. It also follows, that the quantity of water
formed is double that decomposed.