Chapter VII (1)

The unfair rivalry of Philosophers.--Bonaparte the Patron
of Science.--He liberates Dolomieu.--He founds a Prize for
the encouragement of Electric researches.--His letter to the
Minister of the Interior.--Proceedings of the Institute.--The
Prize is conferred on Davy.--The Bakerian Lecture of 1807.--The
Decomposition of the Fixed Alkalies--Potassium--Sodium.--The
Questions to which the discovery gave rise.--Interesting
Extracts from the Manuscript Notes of the Laboratory.--Potash
decomposed by a chemical process.--Letters to Children, and
Pepys.--The true nature of Potash discovered.--Whether Ammonia
contains Oxygen.--Davy's severe Illness.--He recovers and
resumes his labours.--His Fishing Costume.--He decomposes the
Earths.--Important views to which the discovery has led.

It must be confessed that there has too frequently existed amongst philosophers a strange and ungenerous disposition to undervalue the labours of their contemporaries. If a discovery be made, its truth and importance are first questioned; and should these be established, then its originality becomes a subject of dispute.

Truth, although she may have been rarely held fast, has been frequently touched[69] in the dark: it is not extraordinary, therefore, that evidence may be often strained from the writings of philosophers in support of prior claims to late discoveries; but upon a candid review, these loose statements, or obscure hints, will generally be found wholly destitute of the pretensions which an unfair spirit of rivalry has too often laboured to support. Many of such hints, indeed, so far from advancing the progress of truth, had never even attracted notice, until after the discoveries to which they have been supposed to relate.

[69] A most remarkable illustration of this fact occurs in the
history of Locke, who certainly came as near to an important
discovery as any philosopher who ever caught a glimpse of a truth
without seizing it; but his statement did not, in any degree,
hasten the developement of that new branch of science which was
reserved for the genius of Dr. Black to investigate, and who a
century later, by the discovery of fixed air, changed the whole
face of Chemistry. The passage to which I allude is extracted
from the Life by Lord King, and is so curious, that I shall give
it a place in this note. "M. Toinard produced a large bottle of
Muscat: it was clear when he set it on the table; but when he
had drawn out the stopper, a multitude of little bubbles arose,
and swelled the wine above the mouth of the bottle. It comes
from this, that the air, which was included and disseminated
in the liquor, had liberty to expand itself, and so to become
visible, and, being much lighter than the liquor, to mount with
great quickness.--_Quere_, Whether this be air new generated, or
whether the springy particles of air in the fruit, out of which
these fermenting liquors are drawn, have, by the artifice of
Nature, been pressed close together, and there by other particles
fastened and held so; and whether fermentation does not loose
these bands, and give them liberty to expand themselves again?
Take a bottle of fermenting liquor, and tie a bladder on the
mouth.--_Quere_, How much new air will it produce; and whether
this has the quality of common air?"

Another instance equally illustrative of the manner in which
important truths will sometimes elude notice, even after Science
has approached so near as to touch them, is presented in the
history of the Barometer. Toricelli, the pupil of Galileo, while
reflecting upon the phenomenon which had so greatly perplexed
his master, viz. that water could not be raised above thirty-two
feet in the body of a pump, rightly conjectured that the water,
under such circumstances, was not _drawn_, but _pushed up_ into
the barrel, and that it could only be so pushed up by the force
of the atmosphere. It then occurred to him, that if mercury were
used instead of water, being heavier, it would not be pushed
up so high by the weight of the air. So, taking a glass tube
of about three feet in height, made air-tight at one end, he
first filled it completely with quicksilver, and then closing it
with his finger, reversed it in a basin containing that metal;
when he had the gratification of seeing the liquid in the tube
descend, as he had anticipated. Here then was the discovery of
the BAROMETER; but it was reserved for another to find out that
such an instrument had been actually invented. Pascal first made
the remark, that the inference of Toricelli, if true, might
be confirmed by carrying the mercurial tube to a considerable
elevation; when the atmospheric column being diminished, that of
the mercury, which was supposed to be its balance, ought likewise
to be shortened in a corresponding proportion. It followed
then, that a measure of the weight of the atmosphere, in all
circumstances, had been obtained, and consequently that of the
height of any place to which the instrument could be carried. In
this manner was a discovery completed, which had for ages escaped
the greatest philosophers who had made the nearest approaches to
its developement.

Although the importance of Davy's Electro-chemical discoveries could not for a moment be doubted; their claims to originality, it would seem, were not admitted without some question. The works of Ritter and Winterl, amongst many others, were quoted to show that these philosophers had imagined or anticipated the relation between electrical powers and chemical affinities; but Davy very fairly observes, in a paper read before the Royal Society in 1826, that in the obscurity of the language and metaphysics of both those gentlemen, it is difficult to say what may not be found. In the ingenious though wild views of Ritter, there are hints which may more readily be considered as applying to _Electro-magnetism_ than to _Electro-chemistry_; while Winterl's _Miraculous Andronia_ might, with as much propriety, be considered as a type of all the chemical substances that have been since discovered, as his view of the antagonist powers (the acid and base) be regarded as an anticipation of the _Electro-chemical_ theory.

It would be worse than useless to speak of other works, which refer the origin of Electro-chemistry to Germany, Sweden, and France, rather than to Italy and England; and which attribute some of the views first developed by Davy, to philosophers who have not, nor ever could have made any claim of the kind, since their experiments were actually not published until many years after 1806, the date of the Bakerian Lecture.

With regard to the judgment of posterity upon these points, but little apprehension can be entertained. I well remember, in a conversation with Davy, he observed, that "a philosopher might generally discover how his labours would be appreciated in after ages, from the opinion entertained of them by contemporary foreigners, who, being unbiassed by circumstances of personality, will reduce every object to its just proportions and value."

If we acknowledge the truth of such a standard, and submit the posthumous fame of Davy to its measure, where is the philosopher, in our times, whose name is destined to attain a higher eminence in the history of Science? Let the reader only recall to his recollection the bitter animosity which France and England mutually entertained towards each other in the year 1807, and he will be able to form some idea of the astounding impression which the Bakerian Lecture must have produced on the Savans of Paris, when, in despite of national prejudice and national vanity, it was crowned by the Institute of France with the prize of the First Consul! Thus did the Voltaic battery, in the hands of the English chemist, achieve what all the artillery of Britain could never have produced--A SPONTANEOUS AND WILLING HOMAGE TO BRITISH SUPERIORITY!--But let not this observation convey the slightest idea of disrespect, or be supposed to encourage any feeling to the disparagement of the chemists of France; on the contrary, it is even a question not readily answered, to which party the triumph fairly belongs,--to him who won the laurel crown, or to those who so nobly placed it on his brow? They have set an example to future ages, which may as materially advance the progress of science, as the researches which called it forth:--they have shown, to adopt the language of an eloquent writer, that "the Commonwealth of Science is of no party, and of no nation; that it is a pure Republic, and always at peace. Its shades are disturbed neither by domestic malice nor foreign levy; they resound not with the cries of faction or of public animosity. Falsehood is the only enemy their inhabitants denounce; Truth, and her minister Reason, the only leaders they follow."

I shall avail myself of this opportunity to introduce the Report drawn up by M. Biot, and made in the name of a Commission appointed by the Institute to accomplish the intention of Bonaparte, who, when First Consul, founded prizes for important discoveries in Electricity or Galvanism.

It is an opinion very generally received, that despotism is hostile to the progress of Philosophy--that the suspicion natural to tyranny, and the fear that light should expose its deformity, have, under such circumstances, inspired a dread of any thing approaching to freedom of enquiry. The conduct of Napoleon, not only during his Consulate, but even after he had assumed the Purple, is in direct opposition to such an opinion. Now that the excitements of national hostility have subsided, and the asperity of our feelings towards that extraordinary man has been softened by time and prosperity, we are enabled to discern the bright and sunny spots in his character.

Not to mention the immense plans which his genius suggested for the internal improvement of France, the annals of the Institute would furnish innumerable proofs of the zeal with which he encouraged Science, and promoted its interests.

His liberation of Dolomieu from the dungeons of Tarentum was an act not only remarkable for the considerate regard it displayed for Science, but for the spirit and eagerness with which it was effected. The French Government had repeatedly made the most urgent demands for the liberty of one who had reflected so much credit on his country;--the Danes had also directed the interference of their Minister, and the King of Spain had added his solicitations in vain:--no sooner, however, had the astonishing campaign which terminated by the victory of Marengo, completely established the French Republic, than Bonaparte, in making peace with Naples, stipulated for the immediate deliverance of Dolomieu, as the first article of the treaty.

The following letter from Bonaparte, addressed to the Minister of the Interior, and by him transmitted to the Institute, expresses the intentions of the First Consul, in founding prizes for important discoveries in Electricity or Galvanism.

"I intend, Citizen Minister, to found a prize, consisting of a
Medal of three thousand francs, (about one hundred and twenty
pounds sterling,) for the best experiment which shall be made in
the course of each year, on the Galvanic fluid.

"For this purpose, the Memoirs containing the details of the said
experiments shall be sent before the First of _Fructidor_, to the
Class of the Mathematical and Physical Sciences, which in the
complimentary days shall adjudge the prize to the author of that
experiment which has been most useful to the progress of Science.

"I also desire to give, by the way of encouragement, the sum of
sixty thousand francs to the person who, by his experiments and
discoveries, shall, according to the opinion of the Class, advance
the knowledge of Electricity and Galvanism as much as Franklin and
Volta did.[70]

"Foreigners of all nations are admitted to the competition.

"I beg you will make known these dispositions to the President of
the First Class of the National Institute, that it may give to
these ideas such developement as may appear proper; my particular
object being to encourage philosophers, and to direct their
attention to this part of philosophy, which, in my opinion, may
lead to great discoveries.

"(Signed) BONAPARTE."

[70] "À celui qui, par ses expériences et ses découvertes, _fera
à faire à l'Electricité et au Galvanisme un pas comparable à
celui qu'ont fait faire à ces Sciences Franklin et Volta_."

My French correspondent adds, "Ces soixantes mille francs n'ont
pas été adjugés, _le pas n'ayant point été fait_."

Upon the presentation of this letter, a Committee was appointed to consider the means for accomplishing the intentions of the First Consul; and after expatiating upon the extensive agencies of Electricity, their Report concludes in the following manner:--

"To fulfill the intention of the First Consul, and to give to the
competition all the solemnity which the importance of the object,
the nature of the Prize, and the character of the Founder require,
the Commissioners unanimously propose as follows:

"The Class of the Mathematical and Physical Sciences of the
National Institute opens the general competition required by the
First Consul.

"All the learned of Europe, and the Members and Associates of the
Institute, are admitted to the competition.

"The Class does not require that the Memoirs should be immediately
addressed to it. Every year it will crown the author of the best
experiments which shall come to its knowledge, and which shall have
advanced the progress of the science.

"The present report, containing the letter of the First Consul,
shall be printed, and serve as a programme.

"Done at the National Institute, Messidor 11, year 10.

"(Signed) LAPLACE, HALLE, COULOMB,
HAUY. BIOT, Reporter."

It was not until twelve months after the publication of his first Bakerian Lecture, that Davy received the intelligence that the prize of three thousand francs had been awarded him by the Institute of France, for his discoveries announced in the Philosophical Transactions for the year 1807.

Mr. Poole, in a late communication, informs me that he was in London soon after the letter communicating this gratifying intelligence had been received from France; and that Davy, upon showing it to him, observed, "Some people say I ought not to accept this prize; and there have been foolish paragraphs in the papers to that effect; but if the two countries or governments are at war, the men of science are not. That would, indeed, be a civil war of the worst description: we should rather, through the instrumentality of men of science, soften the asperities of national hostility."

After Davy had been elected Secretary to the Royal Society, he appears to have been confined to town during the autumn of 1807, when he wrote the following letter.

TO THOMAS POOLE, ESQ.

August 28th, 1807.

MY DEAR POOLE,

I am obliged to be in the neighbourhood of town during the greater
part of the summer, for the purpose of correcting the press for
the Philosophical Transactions.

I made a rapid journey into Cornwall for the sake of seeing my
family; and it was not in my power, had I received your letter at
Lyme, to have accepted your kind invitation.

If C---- is still with you, will you be kind enough to say to him,
that I wrote nearly a week ago two letters about lectures, and not
knowing where he was, I addressed them to him at different places?
I wish very much he would seriously determine on this point. The
Managers of the Royal Institution are very anxious to engage him;
and I think he might be of material service to the public, and
of benefit to his own mind, to say nothing of the benefit his
purse might also receive. In the present condition of society,
his opinions in matters of taste, literature, and metaphysics,
must have a healthy influence; and unless he soon become an actual
member of the living world, he must expect to be hereafter brought
to judgment 'for hiding his light.'

The times seem to me to be less dangerous, as to the immediate
state of this country, than they were four years ago. The extension
of the French Empire has weakened the disposable force of France.
Bonaparte seems to have abandoned the idea of invasion; and if our
Government is active, we have little to dread from a maritime war,
at least for some time. Sooner or later, our Colonial Empire must
fall in due time, when it has answered its ends.

The wealth of our island must be diminished, but the strength of
mind of the people cannot easily pass away; and our literature,
our science, our arts, and the dignity of our nature, depend little
upon our external relations. When we had fewer colonies than Genoa,
we had Bacons and Shakspeares.

The wealth and prosperity of the country are only the _comeliness_
of the body--the fulness of the flesh and fat;--but the spirit is
independent of them; it requires only muscle, bone, and nerve, for
the true exercise of its functions. We cannot lose our liberty,
because we cannot cease to _think_; and ten millions of people are
not easily annihilated.

I am, my dear Poole, very truly yours,

H. DAVY.

While the Electro-chemical laws, developed in the last chapter, are fresh in the recollection of the reader, I shall proceed to the consideration of his second Bakerian Lecture, which was read in November 1807; and in which he announces the discovery of the metallic bases of the fixed alkalies,--a discovery immediately arising from the application of Voltaic electricity, directed in accordance with those laws;--thus having, as we have seen in the first instance, ascended from particular phenomena to general principles, he now descends from those principles to the discovery of new phenomena: a method of investigation by which he may be said to have applied to his inductions the severest tests of truth, and to have produced a chain of evidence without having a single link deficient.

Since the account given by Newton of his first discoveries in Optics, it may be questioned whether so happy and successful an instance of philosophical induction has ever been afforded as that by which Davy discovered the composition of the fixed alkalies. Had it been true, as was most unjustly insinuated at the time, that the discovery was accidentally effected by the high power of the apparatus placed at his disposal, his claims to our admiration would have assumed a very different character: in such a case, he might be said to have forced open the sanctuary of Nature by direct violence, instead of having discovered and touched the secret spring by which its portals were unclosed. The justice of these remarks will best appear in the examination of his memoir: the highest eulogy that can be conferred on its author will be a faithful and plain history of its contents.

It will be remembered that, in his preceding lecture of 1806, he had described a number of decompositions and chemical changes produced in substances of known composition, by the powers of electricity, and that in all such cases there invariably subsisted an attraction between oxygen and the _positive_ pole, and between inflammable matter and the _negative_ pole of the pile: thus, in the decomposition of water, its oxygen was transferred to the former, and its hydrogen to the latter. Furnished with such data, Davy proceeded to submit a fixed alkali to the most intense action of the Voltaic apparatus, well convinced that, should the electrical energy be adequate to effect its decomposition, the elements would be transferred, according to this general law, to their respective poles.

His first attempts were made on solutions of the alkalies; but, notwithstanding the intensity of the electric action, the water alone underwent decomposition, and oxygen and hydrogen were disengaged with the production of much heat, and violent effervescence. The presence of water thus appearing to prevent the desired decomposition, potash, in a state of igneous fusion, was in various ways submitted to experiment; when it was evident that combustible matter of some kind, burning with a vivid light, was given off at the negative wire. After numerous trials, during the progress of which the difficulties which successively arose were as immediately combated by ingenious manipulation, a small piece of potash sufficiently moistened, by a short exposure to the air, to give its surface a conducting power, was placed on an insulated disc of platina, connected with the negative side of the battery in a state of intense activity, and a platina wire communicating with the positive side, was at the same instant brought into contact within the upper surface of the alkali.--Mark what followed!--A series of phenomena, each of which the reader will readily understand as it is announced,--for it will be in strict accordance with the laws which Davy had previously established:--the potash began to fuse at both its points of electrization: a violent effervescence commenced at the upper, or positive surface; while at the lower, or negative one, instead of any liberation of elastic matter, which would probably have happened had hydrogen been an element of the alkaline body, small globules, resembling quicksilver, appeared, some of which were no sooner formed than they burnt with explosion and bright flame.--What must have been the sensations of Davy at this moment!--He had decomposed potash, and obtained its base in a metallic form.

The gaseous matter developed, during the experiment, at the positive pole of the apparatus, he very shortly identified as oxygen. To collect, however, the metallic matter, in a quantity sufficient for a satisfactory examination, was by no means so easy; for, like the _Alkahest_ imagined by the Alchemist, it acted more or less upon every body to which it was exposed; and such was its attraction for oxygen, that it speedily reverted to the state of alkali by recombining with it.

After various trials, however, it was found that recently distilled naphtha presented a medium in which it might be preserved and examined, since a thin transparent film of this fluid, while it defended the metal from the action of the atmosphere, did not oppose any obstacle to the investigation of its physical properties.

Thus provided, he proceeded to enquire into the nature of the new and singular body, to which he afterwards gave the name of POTASSIUM, and which may be described as follows.

Its external character is that of a white metal, instantly tarnishing by exposure to air; at the temperature of 70° Fah. it exists in small globules, which possess the metallic lustre, opacity, and general appearance of quicksilver; so that when a globule of the latter is placed near one of the former, the eye cannot discover any difference between them: at this temperature, however, the metal is not perfectly fluid; but when gradually heated, it becomes more so,--and at 150°, its fluidity is so perfect that several globules may be easily made to run into one. By reducing its temperature, it becomes, at 50°, a soft and malleable solid, which has the lustre of polished silver, and is soft enough to be moulded like wax. At about the freezing point of water it becomes hard and brittle, and exhibits, when broken, a crystallized structure of perfect whiteness, and of high metallic splendour. It is also a perfect conductor both of electricity and heat. Thus far, then, it fulfills every condition of a metal; but an anomaly of a most startling description has now to be mentioned--the absence of a quality which has been as invariably associated with the idea of a metal, as that of lustre, viz. great specific gravity. Whence a question has arisen, whether, after all, the alkaline base can with propriety be classed under that denomination? Instead of possessing that ponderosity which we should have expected in a body otherwise metallic, it is so light as not only to swim upon the surface of water, but even upon that of naphtha, by far the lightest liquid in nature. Davy, however, very justly argues, that low specific gravity does not offer a sufficient reason for degrading this body from the rank of a metal; for amongst those which constitute the class, there are remarkable differences with respect to this quality; that platina is nearly four times as heavy as tellurium. In the philosophical division of bodies into classes, the analogy between the greater number of properties must always be the foundation of arrangement.[71]

[71] The propriety, and even the necessity, of such a compact
become daily more apparent, as our knowledge of bodies
extends. If we were to degrade a substance from its class, in
consequence of the absence of some one quality which enters
into its more perfect examples, we should soon find ourselves
involved in paradoxes.--What idea, for instance, could we form
of an acid?--Its sourness?--Prussic Acid--Arsenious Acid, are
not sour.--Its tendency to combine with an alkaline or earthy
base?--If so, sugar is an acid, for it combines with lime. I
remember a chemist having been exposed to much ridicule from
speaking of a _sweet_ acid--Why not?

So inseparable however, by long association, are the ideas of ponderosity and metallic splendour, that the evidence even of the senses may fail in disuniting them.[72] This is well illustrated by the following amusing anecdote. Shortly after the discovery of potassium, Dr. George Pearson happened to enter the laboratory in the Royal Institution, and upon being shown the new substance, and interrogated as to its nature, he, without the least hesitation, on seeing its lustre, exclaimed, "Why, it is metallic, to be sure," and then, balancing it on his finger, he added, in the same tone of confidence, "_Bless me, how heavy it is!_"

[72] In the language of Darwin, we should say, that the simple
ideas of weight and lustre, which form the complex idea of a
metal, have become so indissoluble, that they can no longer be
separated by volition. The principle admits of many familiar
illustrations, and is the source of numerous fallacies. When any
one voluntarily recollects a Gothic window, which he had seen
some time before, the whole front of the Cathedral occurs to him
at the same time: in like manner, the taste of a pine-apple,
though we eat it blindfold, recalls the colour and shape of it.
Coleridge has made a good remark upon this subject. He says, "It
is a great law of the imagination, that a likeness in part tends
to become a likeness of the whole." It is thus that we trace
images in the fire, castles in the clouds, and spectres in the
gloom of twilight.

When thrown upon water, potassium instantly decomposes that fluid, and an explosion is produced with a vehement flame: an experiment which is rendered more striking if, for water, ice be substituted; in this latter case, it instantly bums with a bright rose-coloured flame, and a deep hole is made in the ice, which will afterwards be found to contain a solution of potash.

It is scarcely necessary to state, that these phenomena depend upon the very powerful affinity which the metal possesses for oxygen, enabling it even to separate it from its most subtle combinations.[73]

[73] If we are disposed to enter into a more critical examination
of the subject, we shall find that, although the above is a
general expression of the change produced, there are subordinate
actions of a more complicated nature: the metal, in the first
place, decomposes a portion of the water, in order to combine
with its oxygen, and form potash, which in its turn has a
powerful affinity for water; the heat arising from two causes,
decomposition and combination, is sufficiently intense to produce
the inflammation. Water is a bad conductor of heat; the globule
swims exposed to air; a part of which is dissolved by the heated
nascent hydrogen; and this gas, being capable of spontaneous
inflammation, explodes and communicates the effect of combustion
to any of the bases that may be yet uncombined. The manner in
which the potassium runs along the surface of water may be
compared to a drop of water on red-hot iron; in the one case the
hot potassium, in the other the cold water, is enveloped in an
atmosphere of steam.

One of the neatest modes of showing the production of alkali, in the decomposition of water by the basis of potash, consists in dropping a globule of potassium upon moistened paper tinged with turmeric. At the moment that it comes into contact with the water, it burns and moves rapidly upon the paper, as if in search of moisture, leaving behind it a deep reddish-brown trace of its progress, and acting upon the test paper precisely as dry caustic potash.

From these observations, the reader will immediately perceive, that the decomposition of the fixed alkalies has placed in the hands of the experimentalist a new instrument of research, scarcely less energetic, or of less universal application, than the power from which the discovery emanated. Davy observes upon this point, that "it will undoubtedly prove a powerful agent for analysis, and having an affinity for oxygen, stronger than any other known substance, it may possibly supersede the application of electricity to some of the undecompounded bodies." So strong indeed is its affinity for oxygen, that it discovers and decomposes the small quantities of water contained in alcohol and ether; and in the latter case, this decomposition is connected with an instructive result. Potash is insoluble in that fluid: when therefore its base is thrown into it, oxygen is furnished, hydrogen gas disengaged, and the alkali, as it is regenerated, renders the ether white and turbid.

But perhaps the most beautiful illustration of its deoxidizing power is afforded by its action on carbonic acid gas, or fixed air: when heated in contact with that gas, it catches fire, and by uniting with its oxygen, becomes potash, while the liberated carbon is deposited in the form of charcoal.

As I have already exceeded the limits originally prescribed to myself, I shall not enter into the history of Davy's experiments on the other fixed alkali, soda, farther than to state that, when it was submitted to Voltaic action, a bright metal was obtained, similar in its general characters to potassium, but possessing sufficiently distinctive peculiarities as to volatility, fusibility, oxidability, &c. To this body Davy assigned the name of SODIUM.[74]

[74] In his Bakerian Lecture of 1810, he informs us that he
obtains Sodium by heating common salt, which has been previously
ignited, with Potassium--an immediate decomposition takes place,
and two parts of Potassium produce rather more than one of Sodium.

In support of the metallic characters of these alkaline bases, it may be necessary to state that they combine with each other, and form alloys; the properties and habitudes of which are very interesting, and are fully described by their discoverer.

No sooner had these results been made known to the scientific world, than a question arose, both in this country and abroad, as to the real nature of the bodies which had been thus obtained from the fixed alkalies, and which presented an aspect so obviously metallic. At first, it was conjectured by a few, that they might be compounds of the alkali with the platina used in the experiments; but this was at once disproved by Davy having obtained the same results when pieces of copper, silver, gold, plumbago, or even charcoal, had been employed for completing the Voltaic circuit.

The effect which this and his subsequent discoveries produced, in revolutionizing the theory of Chemistry, will form an interesting subject for discussion in a future part of the present work: I shall therefore only remark in passing, that the fact of oxygen, the acknowledged principle of acidity, existing in combination with a metallic base, and imparting to it the properties of an alkali, was no sooner announced, than its truth was strenuously denied. It was an attack upon opinions sanctioned by the general suffrage of the scientific world;--it was, in fact, storming the very citadel of their philosophy: no wonder, then, that the agitator should have been assailed with a full cry for his revolutionary plans.[75] M. Curadau read a paper before the French Institute, in which he endeavoured to prove, _first_, that the conversion of the alkalies into metals was not a deoxidation of those bodies, but a combination of them with new elements;--_secondly_, that the affinity of the alkaline metals for oxygen was merely a chemical illusion, occasioned by some body the presence of which had not been suspected;--_thirdly_, that carbon was one of the elements of the alkaline metals, since it could be separated from them at pleasure, or converted into carbonic acid;--and _fourthly_, that if the specific gravities of the new substances were less than that of water, it was because hydrogen was associated with carbon in the combination.

[75] Many years afterwards, when Davy was travelling on the
Continent, a distinguished person about a foreign court, enquired
who and what he was; never having heard of his scientific
fame. Upon being told that his discoveries had revolutionized
Chemistry, the courtier promptly replied--"I hate all
revolutionists--his presence will not be acceptable here."

It is scarcely necessary to state, that the presence of carbon was readily traced to sources of impurity. The hypothesis which assumed the existence of hydrogen as an element, was not so easily refuted. It was espoused by MM. Gay Lussac, Thénard, and Ritter, on the Continent, and by Mr. Dalton in England. The former derived their inference from the action of potassium upon ammonia, by which they obtained a fusible substance that yielded by heat more hydrogen than the ammonia contained; the latter contended that potassium and sodium are proved to be _hydrurets_, by the very process employed for their production; for, since common potash is a _hydrat_, and oxygen is produced at one surface, and potassium at the other, by Voltaic action, he conceived that the former arose from the decomposition of water, and that the hydrogen must therefore unite with the potash to form potassium. It is a curious fact, that Berthollet, in the very sentence in which he insisted upon the excessive quantity of hydrogen disengaged in his experiment, as a proof that potassium must be a _hydruret_, should have stated that the addition of water to the residuum was necessary for obtaining his result. How could it have happened that he overlooked so obvious a source of hydrogen? Mr. Dalton, as well as Ritter, considered the low specific gravity as favouring the idea of their containing hydrogen; but Davy observes that they are less volatile than antimony, arsenic, and tellurium, and much less so than mercury. Besides, sodium absorbs much more oxygen than potassium, and, on the hypothesis of hydrogenation, must therefore contain more hydrogen; and yet though soda is said to be lighter than potash, in the proportion of thirteen to seventeen nearly, sodium is heavier than potassium, in the proportion of nine to seven at least. On the theory of Davy, this circumstance is what ought to have been expected. Potassium has a much stronger affinity for oxygen than sodium, and must condense it much more; and the resulting higher specific gravity of the combination is a necessary consequence. In this manner did Davy entangle his opponents in their own arguments, and establish, in the most triumphant manner, the truths of his original views.

Thus then was a discovery effected, and at once rendered complete, which all the chemists in Europe had vainly attempted to accomplish. The alkalies had been tortured by every variety of experiment which ingenuity could suggest, or perseverance perform, but all in vain; nor was the pursuit abandoned until indefatigable effort had wrecked the patience and exhausted every resource of the experimentalist. Such was the disheartening, and almost forlorn condition of the philosopher when Davy entered the field:--he created new instruments, new powers, and fresh resources; and Nature, thus interrogated on a different plan, at once revealed her long cherished secret.

In his Bakerian Lecture, Davy observes, that "a historical detail of the progress of the investigation of all the difficulties that occurred, and of the manner in which they were overcome, and of all the manipulations employed, would far exceed the limits assigned to a Lecture." But to the chemist, every circumstance, however minute, connected with a subject of such commanding importance, is pregnant with interest; I therefore considered it my duty to search into the archives of the Institution, in the hope that I should discover some memoranda which might supply additional information. In examining the Laboratory Register, I have so far succeeded as to obtain some rough and imperfect notes, which will, to a certain degree, assist us in analysing the intellectual operations by which his mind ultimately arrived at the grand conclusion.

It appears from this register that Davy commenced his enquiries into the composition of potash on the 16th, and obtained his great result on the 19th of October 1807.[76] His first experiments, however, evidently did not suggest the truth: he does not appear to have suspected the nature of the alkaline base until his last experiment, when the truth flashed upon him in the full blaze of discovery. His first note, dated the 16th, leads us to infer that he acted on a solid piece of potash, under the surface of alcohol, and several other liquids in which the alkali was not soluble; and that he obtained gaseous matter, which he called at the moment '_Alkaligen Gas_,' and which he appears to have examined most closely, without arriving at any conclusion as to its nature. On the following day, he, for the first time, would seem to have developed potassium by electric action on potash under oil of turpentine, for the note records the fact of "_the_ globules giving out gas by water, which gas _burnt in contact with air_;" and then follows a query--"Does _it_" (the matter of the globules) "not form gaseous compounds with ether, alcohol, and the oils?" Here, then, he evidently imagined, that the matter of the globules, which he had never obtained from potash, except when acted upon under oil of turpentine, had formed gaseous compounds with the ether, alcohol, and oils in his previous experiments, and given origin to that which he had termed '_Alkaligen Gas_.'

[76] On the same day he decomposed Soda with somewhat different
phenomena.

He then leaves the consideration of this gas, and attacks the unknown globules, which probably did not present any metallic appearance under the circumstances in which he saw them, for they must have been as minute as grains of sand. I rather think that he commenced his examination by introducing a globule of mercury, and uniting it with a globule of the unknown substance, for his note says, "Action of the substance on Mercury,--forms with it a solid amalgam, which soon loses its _Alkaligen_ in the air." And from the note which succeeds, he evidently considered this _Alkaligen_ (potassium) volatile, as he says "it soon flies off on exposure to the air."

October 19.--It is probable that, in consequence of the property which the unknown substance displayed of amalgamating with mercury, he devised his experiment of the 19th. He took a small glass tube, about the size and shape of a thimble, into which he fused a platinum wire, and passed it through the closed end. He then put a piece of pure potash into this tube, and fused it into a mass about the wire, so as entirely to defend it from the mercury afterwards to be used. When cold, the potash was solid, but containing moisture enough to give it a conducting power; he then filled the rest of the tube with mercury, and inverted it over the trough: the apparatus being thus arranged, eurêka he made the wire and the mercury alternately positive and negative. And now, conceiving that I have sufficiently explained his brief notes, the reader shall receive the result in his own words: for this purpose I have obtained an engraving of the autograph, which is here annexed; but as it may not be very readily deciphered, I shall first give the substance of it in print.--"When potash was introduced into a tube having a platina wire attached to it--so--and fused into the tube so as to be a conductor, _i. e._ so as to contain just water enough, though solid, and inserted over mercury, when the platina was made negative, no gas was formed, and the mercury became oxydated, and a small quantity of the _alkaligen_ was produced round the platina wire, as was evident from its quick inflammation by the action of water. When the mercury was made the negative, gas was developed in great quantities from the positive wire, and none from the negative mercury, and this gas proved to be pure oxygene--A CAPITAL EXPERIMENT, PROVING THE DECOMPOSITION OF POTASH." The Reviewer of the Institution Journal well observes that those who knew Davy will best conceive the enthusiasm with which this hasty record of his success was dashed off, and will instantly recognise [Greek: eurêka] in his "CAPITAL EXPERIMENT."

From this same Register, it appears that, in the preceding month, he was deeply engaged in experiments on '_Antwerp blue_,' which he found to consist of _Prussiate of Iron_ and _Alumina_, "probably in the proportion of two-thirds of the former to one-third of the latter."

On the 6th of October, we learn from the same source, that he performed a beautiful experiment, that of producing the vegetation of the carbon of the wick of a candle, by placing it between the wires of the battery.

On the 12th of the preceding September he addressed a letter to Mr. Gilbert, which is curious, as it shows that very nearly up to the time of the decomposition of the alkalies, his mind had been engaged on very different subjects.

TO DAVIES GIDDY, ESQ.

September 12, 1807.

MY DEAR SIR,

I inclose Mr. Carne's paper, which, when you have read, and Mr.
Carne revised, I will thank you to inclose to me, and that as soon
as possible, for the completion of the volume.

I have been a good deal engaged, since my return, in experiments on
distillation, and I have succeeded in effecting what is considered
of great importance in colonial commerce, namely, the depriving rum
of its empyreumatic part, and converting it into pure spirit.

I mention this in confidence, as it is likely to be connected with
some profitable results; and it may be beneficial in a public point
of view, by lessening the consumption of malt.

I have heard of no scientific news; this, indeed, is little the
season for active exertion.

With best respects to your father, and to Mr. and Mrs. Guillemard,
I am, my dear Sir,

Always very faithfully yours,

H. DAVY.

Few notes have conveyed information of such importance to the scientific world, as that which follows, announcing, at the same time, the decomposition of the fixed alkalies, and the formation of the Geological Society, of which it would thus appear that Davy was one of the founders.

TO WILLIAM HASLEDINE PEPYS, ESQ.

November 13, 1807.

DEAR PEPYS,

If you and Allen had been one person, the Council of the Royal
Society would have voted to you the Copleian Medal;[77] but it is
an indivisible thing, and cannot be given to two.

We are forming a little talking Geological Dinner Club, of which I
hope you will be a member. I shall propose you to-day. Some things
have happened in the Chemical Club, which I think render it a less
desirable meeting than usual, and I do not think you would find any
gratification in being a member of it. Hatchett never comes, and we
sometimes meet only two or three. I hope to see you soon.

I have decomposed and recomposed the fixed alkalies, and discovered
their bases to be two new inflammable substances very like metals;
but one of them lighter than ether, and infinitely combustible. So
that there are two bodies decomposed, and two new elementary bodies
found.

Most sincerely yours,

H. DAVY.

[77] He alludes to a Paper, entitled "On the Quantity of
Carbon in Carbonic Acid, and on the Nature of the Diamond; by
William Allen, Esq. F.R.S. and William Hasledine Pepys, Esq."
Communicated by Humphry Davy, Sec. R.S. M.R.I.A. Read June 16,
1807.

In the year 1808, MM. Gay Lussac and Thénard succeeded in decomposing potash by chemical means; for which purpose it is only necessary to heat iron turnings to whiteness in a curved gun-barrel, and then to bring melted potash slowly in contact with the turnings, air being excluded; when the iron, at that high temperature, will take the oxygen from the alkali, and the potassium may be collected in a cool part of the tube. It may likewise be produced by igniting potash with charcoal, as M. Curaudau showed in the same year.

In the following letter, Davy gives an account of his repeating the experiment of MM. Gay Lussac and Thénard; mixing together, as usual, science and angling.

TO J. G. CHILDREN, ESQ.

London, July 1808.

MY DEAR SIR,

I have this moment received your kind letter, and I have written
to Pepys to propose to him to be with you on Sunday or Monday. I
hope for his answer to-morrow morning, and I will write to you
immediately.

I will procure all the fishing tackle you have proposed, and am
most happy to find you in so determined a spirit for piscatory
adventure.

I have had some letters from France; but nothing new, except an
account of the gun-barrel experiment tolerably minute. I have
tried it since, and procured potassium, but it was lost from
some moisture passing into the aperture of the barrel. All that
is necessary for the process is a gun-barrel bent thus, thus,
B\______/\_/A.---- B represents the part where the touch-hole is
closed; here dry potash is introduced; and the middle, which is to
be strongly ignited, contains the filings; the potash is gradually
fused and made to run down upon the ignited iron; the potassium
collects in A.

If you should be able to procure the apparatus for this experiment,
I should like to assist in repeating it; and could we procure a
large quantity of the basis, we may try its effects, on a great
scale, on the undecompounded acids. I will bring some _dry boracic
acid_. A copper or platina tube, if you have one, will be proper
for trying the experiment in. We may likewise try its action upon
the earths, and upon diamond.

I have metallized Ammonia,[78] without the application of
Electricity. When an amalgam of potassium and mercury is brought
in contact with an ammoniacal salt, the potassium seizes upon the
oxygen, and the hydrogen and nitrogen unite to the quicksilver.

I had an opportunity of giving an account, on Friday, to the
scientific men assembled at Greenwich, of your magnificent
experiments and apparatus.[79] Sir Joseph Banks, Mr. Cavendish,
Wollaston, &c. all expressed a strong wish that the results should
be published. I am most happy you have drawn up the account.

I regard the days I have passed in your society, as some of the
pleasantest of my life. I look forward with a warm hope to our next
meeting. Be pleased to assure your father of my highest respect,
and of my gratitude for his kindness.

I am, my dear Sir,

Very sincerely yours,

H. DAVY.

[78] He here alludes to a train of research, which will be
considered hereafter.

[79] This observation relates to the magnificent battery
constructed by Mr. Children, of which he presented an account to
the Royal Society, in a Paper read in November 1808, entitled,
"An Account of some Experiments, performed with a view to
ascertain the most advantageous Method of constructing a Voltaic
Apparatus, for the purpose of Chemical Research. By John George
Children, Esq. F.R.S." The great battery described in this Paper
consisted of twenty pairs of plates, each plate being four feet
high by two feet wide: the sum of all the surfaces was ninety-two
thousand one hundred and sixty square inches, and the quantity of
liquid necessary for charging it, one hundred and twenty gallons.
At the same time he constructed another battery, which consisted
of two hundred pairs of plates, each being only two inches
square. In the one case, then, he commanded extent of surface,
in the other, extent of number; and by a series of comparative
experiments, he fully established the theory of Davy (page 246),
that the _intensity_ of Electricity increases with the _number_,
and the _quantity_ with the _surface_.

It is impossible to reflect upon the chemical processes by which potassium may be obtained, without feeling surprised that the discovery should not have long before been accomplished. It is evident that the substance must have been repeatedly developed during the operations of chemistry; alkalies had been frequently heated to whiteness in contact both with iron and charcoal, and in some instances the appearance of a highly combustible body, which could have been no other than potassium, had even been observed as a result of the process, and yet no suspicion, as to its real nature, ever crossed the mind of the experimentalist; he satisfied himself with designating such a product, whenever it occurred, by the term _Pyrophorus_.[80] I remember the late Mr. William Gregor informing me that, in the course of his analytical experiments with potash and different metals, he had repeatedly observed a combustion on removing the crucible from the furnace, and exposing its contents, which he could never understand. How admirably do such anecdotes illustrate the remark made in the commencement of the present chapter, that truth may be often touched, but is rarely caught, in the dark!

[80] The Pyrophorus of Homberg, of which a description is to
be found in the _Mémoires de l'Academie_, for 1711, was made
by mixing together any combustible body, as gum, flour, sugar,
charcoal, &c. and alum, and then, after roasting the mixture till
it was reduced to a dry powder, exposing it in a matrass to a red
heat. In this process, the theory of which was first explained by
Davy, the potash of the alum is converted into potassium, which,
by its absorption of oxygen from the atmosphere, generates heat,
and sets fire to the charcoal contained in the powder.

The facility of the combustion of the bases of the alkalies, and the readiness with which they decomposed water, offered Davy the ready means for determining the proportions of their constituent parts: and in comparing all his results, he thinks that it will be a good approximation to the truth, to consider potash as composed of about six parts base and one of oxygen; and soda, as consisting of seven base and two of oxygen.

The discovery of potassium led to that of the true nature of what had been long familiar to chemists by the name of _pure Potash_, but which ought to have been called the _hydrat_, for the _pure_ alkali was not known until after the discovery of Davy. The experiments of MM. Gay Lussac and Thénard have shown this substance to be a _Protoxide_. It is difficult of fusion; it has a grey colour and a vitreous fracture, and dissolves in water with much heat. The _Peroxide_ is procured by the combustion of potassium at a low temperature; it had been observed by Davy in October 1807, but at that time he supposed it to be the oxide containing the smallest proportion of oxygen: it has a yellow colour, and when thrown into water effervesces, and gives out oxygen gas.[81] When heated very strongly upon platina, oxygen is also expelled from it, and there remains the _protoxide_, or pure potash.

[81] The 'Potassa Fusa' of our Pharmacopoeia generally contains a
small proportion of the peroxide, and will therefore effervesce
when thrown into water.

It was a great object with Davy, to show that the product resulting from the combustion of potassium, was a pure oxide free from water; for it is evident that had potassium been a _Hydruret_, its combustion must have produced a _Hydrat_. This he accomplished by a series of experiments which he performed in the laboratory of Mr. Children, and which are published in his Bakerian Lecture of 1800.

Having discovered the presence of oxygen in the fixed alkalies, he was naturally led by analogy to enquire whether ammonia might not also contain it. It was true that the chemical composition of that body had been considered as satisfactorily settled, and that the conversion of it into hydrogen and nitrogen, in the experiments of Scheele, Priestley, and Berthollet, had left nothing farther to be accomplished. All new facts, however, are necessarily accompanied by a new train of analogies; and Davy, in perusing the accounts of the various experiments to which ammonia had been submitted, tells us that he saw no reason for considering the presence of oxygen as impossible; for, supposing hydrogen and nitrogen to exist in combination with oxygen in low proportion, this latter principle might easily disappear in the analytical experiments by heat and electricity, in the form of water deposited upon the vessels employed, or dissolved in the gases produced.

Under this impression, he commenced a series of experiments by which, he says, he soon became satisfied of the existence of oxygen in the volatile alkali. By means of the Voltaic battery, he ignited perfectly dry charcoal in a small quantity of pure ammoniacal gas, and he produced carbonate of ammonia; which could not have happened, had not oxygen been furnished by the volatile alkali to the carbon. In the next place, by an ingenious arrangement of apparatus, he submitted ammonia to a high temperature, and effected its decomposition, when a quantity of water appeared as one of the products. It will be useless to enter into farther details upon this occasion, as we shall presently perceive the subject assumed a different aspect, and led the experimentalist into a new line of enquiry.