THE CHEMICAL LABORATORY OF THE ROYAL INSTITUTION.
The chemical laboratory of the Royal Institution, as the scene of
Davy’s greatest discoveries--discoveries which mark epochs in the
development of natural knowledge--will for ever be hallowed ground
to the philosopher. The votaries of Hermes have raised far more
stately temples: to-day they follow their pursuit in edifices which
in architectural elegance and in equipment are palaces compared with
the subterranean structure which lies behind the Corinthian façade in
Albemarle Street. But to the chemist this spot is what the Ka’ba at
Mecca is to the follower of Mohammed, or what Iona was to Dr. Johnson:
and, if we may venture to adapt the language of the English moralist,
that student has little to be envied whose enthusiasm would not grow
warmer or whose devotion would not gain force within the place made
sacred by the genius and labours of Davy and Faraday.
And yet, were these great men to revisit the scene of their triumphs,
they would hardly recognise it, so completely altered is it by
adaptations and rearrangements rendered necessary by their discoveries.
How it appeared in their own time may be seen from the illustration on
page 91, taken from a water-colour drawing by Miss Harriet Moore, in
the possession of the Managers of the Royal Institution.
[Illustration: CHEMICAL LABORATORY OF THE ROYAL INSTITUTION IN DAVY’S
TIME.]
The first year of the century is memorable for the invention of the
voltaic pile, and for the discovery, by Nicholson and Carlisle, on
April 30th, 1800, of the electrolytic decomposition of water. As Davy
said, “the voltaic battery was an alarm-bell to experimenters in every
part of Europe; and it served no less for demonstrating new properties
in electricity, and for establishing the laws of this science, than as
an instrument of discovery in other branches of knowledge; exhibiting
relations between subjects before apparently without connection, and
serving as a bond of unity between chemical and physical philosophy.”
The capital discovery of Volta was made known in England at the
earliest possible moment through the mediation of Sir Joseph Banks, and
the study of voltaic electricity, its effects and applications, was
immediately afterwards entered upon by many Englishmen of science with
great zeal and ardour. Davy at this time had just completed his work
on Nitrous Oxide; and, powerfully impressed with the significance of
Nicholson and Carlisle’s observation, he at once turned his attention
to the subject, and even before leaving Bristol he had sent a number of
short papers on what was then usually termed the galvanic electricity
to Nicholson’s Journal. He showed that oxygen and hydrogen were
evolved from separate portions of water, though vegetable and even
animal substances intervened; and conceiving that all decomposition
might be polar, he “electrised” different compounds at the different
extremities, and found that sulphur and metallic substances appeared
at the negative pole, and oxygen and nitrogen at the positive pole,
though the bodies furnishing them were separate from each other. The
papers, however, are mainly remarkable for the fact that they served to
establish the intimate connection between the electrical effects and
the chemical changes going on in the pile, and for the conclusion drawn
concerning their mutual dependence. Within a few days after his removal
to the Royal Institution he resumed his inquiries, publishing his
results in a series of notices in the short-lived Journal of the Royal
Institution.
In 1801 he sent his first communication to the Royal Society, on “An
Account of some Galvanic Combinations, formed by the Arrangement of
single metallic Plates and Fluids, analogous to the new Galvanic
Apparatus of Mr. Volta.”
But at this period, and for some time afterwards, Davy was not
altogether free to develop his own ideas, as the work of the
laboratory was controlled by a committee which met, from time to
time, to deliberate and settle upon the researches which were to be
undertaken by their Professor. As we have seen, he was requested, in
the first place, to turn his attention to tanning, and to investigate
the astringent principles employed in the manufacture of leather.
Afterwards, when the Managers determined to form a mineralogical
collection, and to institute an assay office for the improvement of
mineralogy and metallurgy, he was ordered to make analyses of rocks
and minerals. And lastly, in consequence of an arrangement between
the Managers and the Board of Agriculture, effected by Arthur Young,
he was required to take up the subject of Agricultural Chemistry. To
a man of Thomas Young’s temperament the fussy activity of committees,
directed by such people as Bernard and Hippesley, would have been
resented as an irksome, if not intolerable, interference; but Davy
invariably acted as if he considered that their decisions promoted the
true interests of the Institution, and entered with ardour into each
new scheme. There was no irksomeness to him in being called upon to
change the current of his ideas, for he delighted in the opportunity
of exhibiting his versatility; and, confident in his powers, he had
the ambition to touch everything in turn, and to adorn it. That he
should have succeeded so well under such conditions is perhaps the
strongest evidence that could be adduced of the strength and elasticity
of his eager, active mind, and of his astonishing power of rapid,
well-directed work.
We have already dealt with his researches in connection with tanning.
The efforts of the Managers towards the improvement of mineralogy and
metallurgy, in spite of the generous assistance of Mr. Greville, Sir J.
St. Aubin, and Sir A. Hume, and the “activity and intelligence of Mr.
Davy,” proved abortive.
One outcome of Davy’s association with the matter may be seen in his
paper, published by the Royal Society in 1805, on “An Account of
some analytical Experiments on a mineral Production from Devonshire,
consisting principally of Alumine and Water.” The mineral referred to
was discovered by Dr. Wavel in an argillaceous slate near Barnstaple,
and hence was termed _wavellite_. Davy failed to recognise its true
nature, which was first correctly ascertained by Berzelius. A few
weeks later, he sent to the Royal Society a second paper “On a Method
of Analyzing Stones containing fixed Alkali, by Means of the Boracic
Acid.” The method, however, is of comparatively limited application,
and is seldom, if ever, now used in analysis. Determinative chemistry
was never one of Davy’s strong points, and few of his analytical
processes are now employed. Patient manipulation, and minute and
sustained attention to detail, were altogether foreign to his
disposition and habits, although he had the highest appreciation of
these qualities in men like Cavendish and Wollaston.
The lectures on agriculture however, were a great success, and brought
increased fame and no small profit to the lecturer. His association
with the Board of Agriculture developed into a permanent appointment;
for ten successive years he continued to lecture on the subject before
its members, and in 1813 he put together the results of his labours in
his well-known “Elements of Agricultural Chemistry.” In simplicity and
absence of ornament the style of these lectures is in marked contrast
to that which he usually employed at the Royal Institution. Dealing
with men to whom the matter was of paramount importance, he had no need
to stimulate their interest by the arts he employed in the theatre in
Albemarle Street. The very nature of the subject, perhaps, served to
remind him that tropes and metaphors were here as much out of place
as “the brilliant wild flowers in the field of corn--very pretty, but
which did very much hurt the corn.”
It would be impossible in the space at our disposal to attempt to give
a minute analysis of Davy’s work in connection with agriculture. Its
interest now is, for the most part, historical; what is of permanent
importance in the way of fact has long since been woven into the common
web of knowledge. Its greatest value was not in the novelty or the
abundance of its facts, but rather as a closely-reasoned exposition
of the relation of agriculture to science, and of the necessity
for applying the principles and methods of science to the art. The
philosophic breadth of his views, supported, on occasion, by apt
example and striking analogy, might be illustrated by many extracts.
This, for example, is how he speaks of the value of the scientific
method, and of chemistry, to husbandry:--
“Nothing is more wanting in agriculture than experiments, in
which all the circumstances are minutely and scientifically
detailed. This art will advance with rapidity in proportion as
it becomes exact in its methods. As in physical researches all
the causes should be considered; a difference in the results may
be produced, even by the fall of a half an inch of rain more or
less in the course of a season, or a few degrees of temperature,
or even by a slight difference in the subsoil, or in the
inclination of the land.
“Information collected, after views of distinct inquiry,
would necessarily be more accurate, and more capable of being
connected with the general principles of science; and a few
histories of the results of truly philosophical experiments in
agricultural chemistry would be of more value in enlightening and
benefitting the farmer, than the greatest possible accumulation
of imperfect trials conducted merely in the empirical spirit.
It is no unusual occurrence, for persons who argue in favour
of practice and experience, to condemn generally all attempts
to improve agriculture by philosophical inquiries and chemical
methods. That much vague speculation may be found in the works
of those who have lightly taken up agricultural chemistry, it
is impossible to deny. It is not uncommon to find a number of
changes rung upon a string of technical terms, such as oxygen,
hydrogen, carbon, and azote, as if the science depended upon
words rather than upon things. But this is, in fact, an argument
for the necessity of the establishment of just principles of
chemistry on the subject. Whoever reasons upon agriculture, is
obliged to recur to this science. He feels that it is scarcely
possible to advance a step without it; and if he is satisfied
with insufficient views, it is not because he prefers them
to accurate knowledge, but, generally, because they are more
current.... It has been said, and undoubtedly with great truth,
that a philosophical chemist would most probably make a very
unprofitable business of farming; and this certainly would be the
case, if he were a mere philosophical chemist; and unless he had
served his apprenticeship to the practice of the art, as well as
to the theory. But there is reason to believe that he would be a
more successful agriculturist than a person equally uninitiated
in farming, but ignorant of chemistry altogether; his science,
as far as it went, would be useful to him. But chemistry is not
the only kind of knowledge required: it forms a part of the
philosophical basis of agriculture; but it is an important part,
and whenever applied in a proper manner must produce advantages.”
How highly these lectures were appreciated will be evident from the
terms in which they were referred to by Sir John Sinclair in his
address of 1806 to the Board. He says:--
“In the year 1802, when my Lord Carrington was in the chair, the
Board resolved to direct the attention of a celebrated lecturer,
Mr. Davy, to agricultural subjects; and in the following year,
during the presidency of Lord Sheffield, he first delivered
to the members of this Institution, a course of lectures on
the Chemistry of Agriculture. The plan has succeeded to the
extent which might have been expected from the abilities of the
gentleman engaged to carry it into effect. The lectures have
hitherto been exclusively addressed to the members of the Board;
but to such a degree of perfection have they arrived, that it is
well worthy of consideration, whether they ought not to be given
to a larger audience.”
The “degree of perfection” was in no small degree due to the amount
of experimental and observational work which Davy introduced into his
lectures. Mr. Bernard allotted him a considerable piece of ground
on his property at Roehampton for experimental purposes, and the
Duke of Bedford carried out trials for him at Woburn. He studied
from time to time all the operations of practical farming, examined
a great variety of soils, and investigated the nature and action of
manures. He was thus brought into contact with some of the largest
landowners and agriculturists of his time, and was an honoured guest
in the houses of men like Lord Sheffield, Lord Thanet, Mr. Coke of
Holkham, and others.[E] In the practical interest he thus displayed
in the most useful of all the arts he sought to emulate the example
of his illustrious prototype Lavoisier, and his work constitutes the
foundation of every treatise on the subject since the appearance, in
1840, of Liebig’s well-known book.
[E] In the print of the “Woburn Sheep-Shearing,” Davy is
represented as one of a group comprising Mr. Coke, Sir
Joseph Banks, Sir John Sinclair, and Mr. Arthur Young.
Professor Warington, than whom no one is more fitted to express an
opinion, has favoured me with the following critical estimate of the
value of Davy’s work:--
“The lectures profess to be exhaustive and thus present all that
Davy had been able to collect on the subject of the relations of
chemistry to agriculture during a period of at least 10 years.
He appears to have made a careful study of the problems of
agriculture for many years, and to be acquainted with English
practice, and English experiments. There is but little reference
to foreign practice, or foreign opinion, save where the work
done has been purely chemical, as _e.g._ that of Gay Lussac, or
Vauquelin. He approaches his subject in a thoroughly scientific
manner, taking an independent view of each question, bringing all
the knowledge at his disposal to bear upon it, and not hesitating
to come to conclusions different from those usually received.
The _great step_ taken in these lectures is the assertion
that Agriculture must look to Natural Science, and especially
to Chemistry, for the explanation of its problems and the
improvement of its practice. Davy seems to have been the first,
at least in this country, who boldly claimed for ‘Agricultural
Chemistry’ the position of a distinct branch of science. He was
probably the earliest example of a first-class chemist, who
seriously and continuously devoted his best attention to the
subject of agriculture.
“The lectures, looked at from a modern standpoint, are of
unequal value. The method of food-analysis is very poor, and it
is somewhat surprising that the accurate mode of determining
nitrogen employed by Gay Lussac is not made use of in Davy’s
analyses. Nevertheless he manages to ascertain that spring sown
wheat is richer in gluten than autumn sown, and the wheat of hot
countries richer than the wheat of temperate regions, statements
which are quite correct.
“Lecture VI. is decidedly poor. Davy believes that plants feed
on carbonaceous matter by their roots, and this mistaken theory
leads him to assign an undue value to organic substances as
manures. It seems curious nowadays to find the whole subject of
manures treated with hardly any reference to their contents in
nitrogen, phosphoric acid, or potash.
“Lecture IV. is one of his best lectures, full of keen
observation and suggestive experiment.
“The references to his own agricultural experiments are very
numerous; he seems to have made experiments on every subject of
inquiry that came before him. There is however no attempt at an
extended and thorough investigation of any subject, and for want
of this the truth is sometimes missed. Thus in his trials of
various ammonium salts as manures he finds the carbonate to be
effective, the chloride to be of little value, and the sulphate
of no good at all, whereas the last-named salt is now generally
chosen as a manure.
“There are some paragraphs that read like the inspirations of
genius, though it is now of course difficult to tell to what
extent his statements and opinions were warranted by the facts
then known. He gives a wonderfully correct idea of the action of
peas or beans in rotation, even including the statement that they
obtain their nitrogen from the atmosphere.”
Although his time and energy were necessarily largely absorbed by
the demands of the Managers, Davy never lost sight of the subject
of voltaic electricity, and at intervals he was able to resume his
inquiries upon it. What specially impressed him was the power of
the voltaic pile as an analytic agent; and his laboratory journals,
preserved at the Royal Institution, record the results of numerous
trials on the behaviour of compound substances under its influence.
In spite of innumerable distractions and constant interruptions, due
mainly to the precarious position of the Institution, Davy gradually
succeeded in unravelling the fundamental laws of electro-chemistry, and
in thus importing a new order of conceptions, altogether unlooked for
and undreamt of, into science. This really constitutes his greatest
claim as a philosopher to our admiration and gratitude. The isolation
of the metals of the alkalis, and the proof of the compound nature of
the alkaline earths, were unquestionably achievements of the highest
brilliancy, and as such appeal strongly to the popular imagination.
But they were only the necessary and consequential links in a chain
of discovery which, had Davy neglected to make them, would have been
immediately forged by others. It is significant that almost immediately
after the capital discovery of Nicholson and Carlisle, Dr. Henry of
Manchester, the well-known friend and collaborator of Dalton, should
have made the attempt to separate the presumed metallic principle of
potash by the agency of voltaic electricity.
* * * * *
Davy communicated the results of his inquiries made prior to the summer
of 1806 in a paper to the Royal Society, which was made the Bakerian
lecture of the year.[F] It is entitled “On some chemical Agencies of
Electricity,” and is divided in nine sections and an introduction.
In the first section, “On the Changes produced by Electricity in
Water,” he set at rest the disputed question as to the origin of the
acid and alkaline matter which had been observed to form during the
electrolysis of this liquid. By some these substances were supposed to
be _generated_ from pure water by the action of electricity; and M.
Brugnatelli had even attempted to prove the existence of a body _sui
generis_ which he termed the _electric acid_. By a series of convincing
experiments Davy showed that the substances were due to the presence of
saline matter in the water, derived either from faulty purification,
or from the solvent action of the water on the vessels, etc., with
which it was in contact. Cruickshank had found that in some cases the
acid was nitric acid and the alkali ammonia: these substances were
shown by Davy to be due to the presence of dissolved air. When pure
water, contained in vessels on which it exerted no solvent action,
was “electrised” _in vacuo_, not a trace of either acid or alkali was
produced.
[F] This lecture, which is one of the events of each session
of the Royal Society, owes its origin to Mr. Henry Baker,
F.R.S., a learned antiquary and naturalist, who, by his
will of July, 1763, bequeathed the sum of £100 to the
Society, the interest of which was to be applied “for
an oration or discourse to be spoken or read yearly by
someone of the Fellows of that Society, on such part
of Natural History or Experimental Philosophy, at such
time, and in such manner, as the President and Council
of the said Society for the time being, shall please to
order and appoint.” Baker died in 1774, and the bequest
came into operation during the presidency of Sir John
Pringle; and Peter Woulfe--one of the last of the English
alchemists--was appointed to deliver the lecture, which he
did for three successive years.
In the second section, “On the Agencies of Electricity in the
Decomposition of various Compounds,” he begins by pointing out that in
all the experiments recorded in the preceding section--that is, in all
changes in which acid and alkaline matter had been present--the acid
matter collected in the water round the positive pole, and the alkaline
matter round the negative pole. This he shows to be true even of such
sparingly soluble substances as gypsum, the sulphates of strontium and
barium, and fluorspar. By connecting together cups or vessels made of
the substances under investigation by a thread of well-washed asbestos,
as suggested by Wollaston, he found that in all cases the acid element
collected round the positive, and the earthy base round the negative
pole. Basalt from Antrim, a zeolite from the Giant’s Causeway, vitreous
lava from Etna, and even glass, in like manner yielded alkaline matter
to water when subjected to the action of voltaic electricity. Soluble
salts, such as the sulphates of sodium, potassium, and ammonium, the
nitrates of potassium and barium, the succinate, oxalate and benzoate
of ammonium, were similarly decomposed: the acids in a certain time
collected in the tube containing the positive wire, and the alkalis and
earths in that containing the negative wire. When metallic solutions,
such as those of iron, zinc, and tin were employed, metallic crystals
or depositions were formed on the negative wire, and oxide was likewise
deposited round it; and a great excess of acid was soon found in the
opposite cup.
In the next section, “On the Transfer of Certain of the Constituent
Parts of Bodies by the Action of Electricity,” he points out that
the observations of Gautherot and of Hisinger and Berzelius rendered
it probable that the saline elements evolved in decompositions by
electricity were capable of being transferred from one electrified
surface to another, according to their usual order of arrangement, but
that exact observations on this point were wanting. He connected a cup
of gypsum with one of agate by means of asbestos, and filling each
with purified water, he inserted the negative wire of the battery in
the agate cup, and the positive wire in that of the sulphate of lime.
In about four hours he found a strong solution of lime in the agate
cup, and sulphuric acid in that of gypsum. By reversing the order, and
carrying on the process for a similar length of time, the sulphuric
acid appeared in the agate cup, and the solution of lime on the
opposite side. Many trials were made with other saline substances with
analogous results.
The time required for these transmissions (the quantity and intensity
of the electricity, and other circumstances remaining the same) seemed
to be related to the length of the intermediate column of water.
To ascertain whether the contact of the saline solution with a
metallic surface was necessary for the decomposition and transference,
he introduced purified water into two glass tubes; a vessel containing
solution of potassium chloride was connected with each of the tubes by
means of asbestos; on introducing the wires into the tubes alkaline
matter soon appeared in one tube, and acid matter in the other; and in
the course of a few hours moderately strong solutions of potash and of
hydrochloric acid were formed.
Two tubes, one containing distilled water, the other a solution of
potassium sulphate, were each connected by asbestos threads with a
vessel containing a dilute solution of litmus; the saline matter was
negatively electrified; and as it was natural to suppose that the
sulphuric acid in passing through the water to the positive side would
redden the litmus in its course, some slips of litmus paper were placed
above and below the pieces of asbestos, directly in the circuit: it
was found that the acid and alkali passed through the litmus solution
without effecting any change in colour.
“As acid and alkaline substances during the time of their
electrical transfer passed through water containing vegetable
colours without affecting them, or apparently combining with
them, it immediately became an object of inquiry whether they
would not likewise pass through chemical menstrua having stronger
attractions for them; and it seemed reasonable to suppose that
the same power which destroyed elective affinity in the vicinity
of the metallic points would likewise destroy it, or suspend its
operation, throughout the whole of the circuit.”
To test this supposition, solution of potassium sulphate was placed
in contact with the negative wire, and pure water in contact with the
positive wire and a weak solution of ammonia was made the middle link
of the conducting chain, so that no sulphuric acid could pass to
the positive pole in the distilled water without passing through the
solution of ammonia.
In less than five minutes it was found that acid was collecting round
the positive pole, and in half an hour the water was sour to the
taste, and gave a precipitate with barium nitrate. Hydrochloric acid
from common salt, and nitric acid from nitre were transmitted through
concentrated alkaline menstrua under similar circumstances. Strontia
and baryta readily passed, like the other alkaline substances, through
hydrochloric and nitric acids; and _vice versâ_ these acids passed
with facility through aqueous solution of baryta and strontia; but it
was impossible to pass sulphuric acid through baryta or strontia, or
to pass baryta and strontia through sulphuric acid, as precipitates of
insoluble barium and strontium sulphate were formed.
* * * * *
In the next section, “On Some General Observations on these Phenomena,
and on the Mode of Decomposition and Transition,” he summarises the
foregoing results:--
“It will be a general expression of the facts that have been
detailed, relating to the changes and transitions by electricity,
in common philosophical language, to say that hydrogen, the
alkaline substances, the metals, and certain metallic oxides,
are attracted by negatively electrified metallic surfaces,
and repelled by positively electrified metallic surfaces; and
contrariwise, that oxygen and acid substances are attracted
by positively electrified metallic surfaces, and repelled by
negatively electrified metallic surfaces; and these attractive
and repulsive forces are sufficiently energetic to destroy or
suspend the usual operation of elective affinity.
“It is very natural to suppose, that the repellent and attractive
energies are communicated from one _particle to another particle_
of the same kind, so as to establish a conducting chain in the
fluid; and that the locomotion takes place in consequence;
and that this is really the case seems to be shown by many
facts. Thus, in all the instances in which I examined alkaline
solutions through which acids had been transmitted, I always
found acid in them whenever any acid matter remained at the
original source....
“In the cases of the separation of the constituents of water,
and of solutions of neutral salts forming the whole of the
chain, there may possibly be a succession of decompositions,
and recompositions throughout the fluid. And this idea is
strengthened by the experiments on the attempt to pass barytes
through sulphuric acid, and muriatic acid through solution of
sulphate of silver, in which as insoluble compounds are formed
and carried out of the sphere of the electrical action, the power
of transfer is destroyed.”
In the next section, “On the General Principles of the Chemical Changes
produced by Electricity,” he points out that it had been already
shown by Bennet that many bodies brought into contact and afterwards
separated exhibited _opposite_ states of electricity; and that this
observation had been confirmed and extended by Volta, who had supposed
that it also takes place with regard to metals and fluids. In his
paper in the _Philosophical Transactions_ of 1801, the first he
sent to the Royal Society, Davy had shown that when alternations of
single metallic plates and acid and alkaline solutions were employed
in the construction of voltaic combinations, the alkaline solutions
always received the electricity from the metal, and the acid always
transmitted it to the metal.
In the simplest case of electrical action, the alkali which receives
electricity from the metal would necessarily, on being separated from
it, appear positive, whilst the acid under similar circumstances would
be negative; and these bodies, having respectively with regard to the
metals that which may be called a positive and a negative electrical
energy, in their repellent and attractive functions seem to be governed
by laws the same as the common laws of electrical attraction and
repulsion.
The seventh section treats of “The Relations between the Electrical
Energies of Bodies and their Chemical Affinities”:--
“As the chemical attraction between two bodies seems to be
destroyed by giving one of them an electrical state different
from that which it naturally possesses; that is, by bringing it
artificially into a state similar to the other, so it may be
increased by exalting its natural energy. Thus, whilst zinc, one
of the most oxidable of the metals, is incapable of combining
with oxygen when negatively electrified in the circuit, even by
a feeble power; silver, one of the least oxidable, easily unites
to it when positively electrified; and the same thing might
be said of other metals. Amongst the substances that combine
chemically, all those, the electrical energies of which are
well known, exhibit opposite states; thus copper and zinc, gold
and quicksilver, sulphur and the metals, the acid and alkaline
substances, afford opposite instances; and supposing perfect
freedom of motion in their particles or elementary matter,
they ought according to the principles laid down, to attract
each other in consequence of their electrical powers. In the
present state of our knowledge it would be useless to attempt
to speculate on the remote cause of the electrical energy,
or the reason why different bodies, after being brought into
contact should be found differently electrified; its relation to
chemical affinity is however, sufficiently evident. May it not be
identical with it, and an essential property of matter?”
How Davy sought to elaborate a theory of chemical affinity on these
facts will be sufficiently obvious from the following extracts:--
“Supposing two bodies, the particles of which are in different
electrical states, and those states sufficiently exalted to give
them an attractive force superior to the power of aggregation,
a combination would take place which would be more or less
intense according as the energies were more or less perfectly
balanced; and the change of properties would be correspondently
proportional.”
“When two bodies repellent of each other act upon the same
body with different degrees of the same electrical attracting
energy, the combination would be determined by the degree; and
the substance possessing the weakest energy would be repelled;
and this principle would afford an expression of the causes of
elective affinity and the decompositions produced in consequence.”
“Or where the bodies having different degrees of the same energy,
with regard to the third body, had likewise different energies
with regard to each other, there might be such a balance of
attractive and repellent powers as to produce a triple compound;
and by the extension of this reasoning, complicated chemical
union may be easily explained.”
As the combined effect of many particles possessing a feeble electrical
energy may be conceived equal or even superior to the effect of a few
particles possessing a strong electrical energy, the same principle may
explain the influence of mass action, as elucidated by Berthollet.
He conceives also that it may be possible to obtain a _measure_ of
chemical affinity founded upon the energy of the voltaic apparatus
required to destroy the chemical equilibrium. He points out that, as
light and heat are the common consequences of the restoration of the
equilibrium between bodies in a high state of opposite electricities,
so it is perhaps an additional circumstance in favour of his theory
to state that heat and light are likewise the result of all intense
chemical action. And as in certain forms of the voltaic battery
when large quantities of electricity of low intensity act, heat is
produced without light; so in slow combinations there is an increase
of temperature without luminous appearance. The effect of heat in
producing combination may, he assumes, be also explained according to
these ideas. It not only gives more freedom of motion to the particles,
but in a number of cases--_e.g._ tourmaline, sulphur, etc.--it seems to
exalt the electrical energies of bodies.
In the eighth section he seeks to apply these principles to the
mode of action of the voltaic pile, and to explain the nature of
the changes which occur between the plates and the exciting fluid,
and he points out that the theory in some measure reconciles the
hypothetical principles of the action of the pile adopted by its
inventor with the opinions concerning the chemical origin of galvanism
held by the majority of British men of science at that period. At
the same time, Davy argues that the facts are in contradiction to
the assumption that chemical changes are the _primary_ causes of the
phenomena of galvanism. Moreover, in mere cases of chemical change--as
in iron burning in oxygen, the deflagration of nitre with charcoal,
the combination of potash with sulphuric acid, the amalgamation of
zinc,--electricity is never exhibited.
In the concluding section he trusts that many applications of the
general facts and principles thus indicated to the processes of
chemistry, both in art and in nature, may suggest themselves to the
philosophical inquirer. It is not improbable, he thinks, that the
electric decomposition of the neutral salts in different cases may
admit of economical uses. He is induced to hope that the new mode of
analysis may lead to the discovery of the _true_ elements of bodies:--
“For if chemical union be of the nature which I have ventured to
suppose, however strong the natural electrical energies of the
elements of bodies may be, yet there is every probability of a
limit to their strength: whereas the powers of our artificial
instruments seem capable of indefinite increase.”
Phenomena similar to those occurring in the voltaic cell must be
produced in various parts of the interior strata of our globe, and it
is very probable that many mineral formations have been materially
influenced, or even occasioned, by such action. The electrical power
of transference may serve to explain some of the principal and most
mysterious facts in geology.
“Natural electricity has hitherto been little investigated,
except in the case of its evident and powerful concentration in
the atmosphere. Its slow and silent operations in every part
of the surface will probably be found more immediately and
importantly connected with the order and economy of nature; and
investigations on this subject can hardly fail to enlighten our
philosophical systems of the earth, and may possibly place new
powers within our reach.”
The publication of this paper exercised a profound sensation, both
at home and abroad. Berzelius, years afterwards, spoke of it as one
of the most remarkable memoirs that had ever enriched the theory of
chemistry--and the praise is the more significant when it is remembered
that Davy had thereby seemed to have taken possession of a field of
inquiry which the Swedish chemist, who was only a year younger than
Davy, had been among the first to enter. Still more significant was
the action of the French Institute. Bonaparte, when First Consul, had
announced to the Institute his intention of founding a medal “for
the best experiment which should be made in the course of each year
on the galvanic fluid,” and had further expressed his desire to give
the sum of sixty thousand francs “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.” A committee of the Institute, consisting of La Place, Halle,
Coulomb, Hauy and Biot, was appointed to consider the best means of
accomplishing the wishes of the First Consul, and twelve months after
the publication of the Bakerian lecture they awarded its author the
medal. Whether the Institute had the means of awarding the sixty
thousand francs as well is more than doubtful, for it does not appear
that the sum named by Bonaparte ever went beyond the promise of it. All
that the Institute got for themselves was, as Maria Edgeworth said, “a
rating all round in imperial Billingsgate.” The two countries at this
period were at war, and the feeling of animosity was most bitter. Of
course, there were persons who said that patriotism should forbid the
acceptance of the award. Davy’s own view was more sensible and politic.
“Some people,” he said to his friend Poole, “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.”