THE ISOLATION OF THE METALS OF THE ALKALIS.
However devoted Davy might be to scientific investigation, he was no
less mindful of the sacred claims of the long vacation. In the summer
of 1805 he went to the Lake Country, where he met Scott in company with
Wordsworth; and the occasion on which the party “climbed the dark brow
of the mighty Helvellyn,” and which gave rise to Scott’s well-known
poem, is thus referred to by Lockhart:--
“This day they were accompanied by an illustrious philosopher
[Davy], who was also a true poet--and might have been one of the
greatest of poets had he chosen; and I have heard Mr. Wordsworth
say, that it would be difficult to express the feelings with
which he, who so often had climbed Helvellyn alone, found himself
standing on its summit with two such men as Scott and Davy.”
But the greater part of this summer he spent in the north of Ireland,
examining the extraordinary geological features of that district. Lady
Brownrigg, the sister of the Bishop of Raphoe, has given a spirited
little account of her impressions of his appearance and manner at that
period. She was, she says, very young at the time.
“We had been invited (I say _we_, for I was then with the Bishop
of Raphoe) by Dr. Richardson to go to his cottage at Portrush,
‘to meet the famous Mr. Davy.’ We arrived a short time before
dinner. In passing through a room we saw a youth, as he appeared,
who had come in from fishing, and who, with a little note-book,
was seated in a window-seat, having left a bag, rod &c., on the
ground. He was very intent upon this little book, and we passed
through unnoticed. We shook hands with our host and hostess,
and prepared for dinner. I went into the drawing-room, under
some little awe of this great philosopher, annexing to such a
character at least the idea of an elderly grave gentleman, not
perhaps, with so large a wig as Dr. Parr, or so sententious a
manner as Dr. Johnson,--but certainly I never calculated on being
introduced to the identical youth, with a little brown head, like
a boy, that we had seen with his book, and who, when I came into
the drawing-room was in the most animated manner recounting an
adventure on the Causeway which had entertained him and from his
manner of telling it was causing loud laughing in the whole room.”
Davy also spent much of the summer of 1806 in Ireland, and the journal
which he kept during his tour contains many interesting notes of his
impressions of the country and the people. In the course of his journey
he visited Edgeworthstown--“the moral and intellectual paradise of the
author of ‘Castle Rackrent,’” as he calls it. That gifted lady tells
her cousin Sophy Ruxton that as the result her head “was stuffed
full of geological and chemical facts.” “Mr. Davy,” she adds, “is
wonderfully improved since you saw him at Bristol; he has an amazing
fund of knowledge upon all subjects, and a great deal of genius.”
There was much in Davy’s own temperament to make him understand and
appreciate the Irish character; himself a man of quick impulse and
active sympathy, he was profoundly moved by the spectacle of Ireland’s
political degradation. In a letter to his friend Poole, written after
his return to London, he says:--
“I long very much for the intercourse of a week with you: I have
very much to say about Ireland. It is an island which might be
made a new and a great country. It now boasts a fertile soil,
an ingenious and robust peasantry, and a rich aristocracy; but
the bane of the nation is the equality of poverty amongst the
lower orders. All are slaves, without the probability of becoming
free; they are in the state of equality which the _sans culottes_
wished for in France; and until emulation, and riches, and the
love of clothes and neat houses are introduced among them, there
will be no permanent improvement.
“Changes in political institutions can, at first, do little
towards serving them; it must be by altering their habits, by
diffusing manufactories, by destroying _middlemen_, by dividing
farms, and by promoting industry by making the pay proportional
to the work: but I ought not to attempt to say anything on the
subject when my limits are so narrow; I hope soon to converse
with you about it.”
With the exception of a rapid journey into Cornwall, for the sake of
seeing his family, he spent the greater part of the summer and autumn
of 1807 in town. He had been made Secretary of the Royal Society in
succession to Gray, and was obliged to be in or near London in order
to see the _Philosophical Transactions_ through the press. From the
Laboratory Journal it would appear that he was occupied at this time on
a variety of disconnected investigations such as the nature of Antwerp
Blue, and the effect of electricity on flame. In a letter to Davies
Gilbert, dated September 12th, he states that he has been a good deal
engaged in experiments on distillation for revenue purposes.
Towards the end of this month, or during the first week of October, he
resumed his experiments with the voltaic battery, and he was led to
study its action on the alkalis. There is some evidence that he had
attacked the same question at Bristol. In a note-book of that period,
under date August 6th, 1800, is the following sentence: “I cannot
close this notice without feeling grateful to M. Volta, Mr. Nicholson,
and Mr. Carlisle, whose experience has placed such a wonderful and
important instrument of analysis in my power”--evidently a jotting to
be used in one of the short communications to Nicholson’s Journal.
This is immediately followed by “Query: Would not potash, dissolved
in spirits of wine, become a conductor?” And he then gives an account
of some experiments on the action of voltaic electricity on aqueous
solutions of ammonia, caustic potash, and hydrochloric acid, which
apparently led to the same result as that already obtained by Nicholson
and Carlisle in the case of water.
It is difficult to determine whether he had any precise idea in again
attacking the problem, or any expectation of a definite result. In one
of his lectures at the Royal Institution on Electro-Chemical Science,
delivered some time subsequently, he said he had a suspicion at that
time that potash might turn out to be “phosphorus, or sulphur united to
nitrogen”:
“For as the volatile alkali was regarded as composed of an
extremely light inflammable body--hydrogen--united to nitrogen, I
conceived that _phosphorus_ and _sulphur_, much denser bodies,
might produce denser alkaline matter; and as there were no
_known_ combination of these with _nitrogen_, it was probable
that there might be unknown combinations.”
Davy once said that “analogy was the fruitful parent of error”; and
the whole history of science probably furnishes no more extraordinary
instance of perverted analogy, or one more unexpected in its
consequences. In another of his lectures he said of the alchemists that
“even their _failures_ developed some unsought-for object partaking of
the marvellous”--and the statement in this case is even more true of
himself. Each phase in the story of this discovery indeed partakes of
the marvellous. Sometime during the first fortnight in October, 1807,
he obtained his first decisive result; and on the 19th of November he
delivered what is generally regarded as the most memorable of all his
Bakerian lectures, “On some new Phenomena of chemical Changes produced
by Electricity, particularly the Decomposition of the fixed Alkalies,
and the Exhibition of the new substances which constitute their bases;
and on the general Nature of alkaline Bodies.” Few discoveries of
like magnitude have been made and perfected in so short a time, and
few memoirs have been more momentous in result than that which Davy
put together in a few hours, and in which he announced his results
to the world. The whole work was done under conditions of great
mental excitement. His cousin Edmund Davy, who at the time acted as
his assistant, relates that when he saw the minute globules of the
quicksilver-like metal burst through the crust of potash and take fire,
his joy knew no bounds; he actually danced about the room in ecstasy,
and it was some time before he was sufficiently composed to continue
his experiments. The rapidity with which he accumulated results after
this first feeling of delirious delight had passed was extraordinary.
Before the middle of November he had obtained most of the leading
facts. In a letter dated November 13th he tells W. H. Pepys--
“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.”
The stories told by Paris of his habits at this period, and of his
various expedients to gain time--of his rushing off to dinner with
persons of the highest rank with no fewer than five shirts on, and as
many pairs of stockings, because in his haste he could not put on fresh
linen without removing that which was underneath; of his continuing
his chemical labours on his return to the laboratory until three or
four in the morning; and of his then being up before the servants, are
certainly much exaggerated, if not wholly apocryphal. He was, it is
true, not very systematic in the disposal of his time, but he seldom
entered the laboratory before ten or eleven in the morning, and rarely
left it later than four, and he was scarcely ever known to visit it
after he had dressed for dinner. Except when preparing a lecture, he
seldom dined in his rooms at the Institution: his brother tells us that
his invitations to dinner were so numerous that he was, or might have
been, constantly engaged; and after dinner he was much in the habit of
attending evening parties, and devoting the evening to amusement, “so
that to the mere frequenters of such parties he must have appeared a
votary of fashion rather than of science.”
It was characteristic of him, that on the very eve of the announcement
of the discovery which raised him to the summit of his scientific
fame, he could unbend the strung bow and thus write to his youngest
sister:--
“MY DEAR SISTER, ... I looked last week at the pattern of the
gown that my sister put into my hands, and found it so worn and
tattered that nothing can be made of it; I cannot therefore get
your gowns made till you send me another. The best way will be to
give me measure of the waist, shoulders, length &c., in this way,
and there can then be no difficulties: thus waist, 15 inches, or
whatever it may be; between shoulders: length from waist to skirt
or train.
“I do not wish to send gowns you cannot wear, and in this way
they can be well made. By a piece of tape you can easily measure
and then try the length by a carpenter’s rule, and give me the
results for yourself, and for Kitty, and Grace, and I shall
then be able to send your gowns a few days after I receive your
letter....
“I shall write to my mother soon, about John. And now, my dear
sister, having written you as stupid a letter as ever was written
about gowns, I shall end with love to my mother, Kitty, Grace,
and my aunts.
“Your affectionate brother
“H. DAVY.”
The Bakerian lecture in which Davy announces the discovery of the
compound nature of the fixed alkalis opens with a reference to the
concluding remarks of his lecture of the previous year, “that the new
methods of investigation promised to lead to a more intimate knowledge
than had hitherto been obtained concerning the true elements of bodies.
This conjecture, then sanctioned only by strong analogies, I am now
happy to be able to support by some conclusive facts.”
In the first attempts he made to decompose the fixed alkalis he acted
upon concentrated aqueous solutions of potash and soda with the highest
electrical power he could then command at the Royal Institution--viz.
from voltaic batteries containing 24 plates of copper and zinc of 12
inches square, 100 plates of 6 inches, and 150 of 4 inches, charged
with solutions of alum and nitric acid; but although there was high
intensity of action nothing but hydrogen and oxygen was disengaged. He
next tried potash in igneous fusion, and here the results were more
encouraging: there were obvious and striking signs of decomposition:
combustible matter was produced accompanied with flame and a most
intense light. He had observed that although potash when dry is a
non-conductor, it readily conducts when it becomes damp by exposure
to air, and in this state “fuses and decomposes by strong electrical
powers.”
“A small piece of pure potash, which had been exposed for a few
seconds to the atmosphere, so as to give conducting power to the
surface was placed upon an insulated disc of platina, connected
with the negative side of the battery of the power of 250 of 6
and 4, in a state of intense activity;[G] and a platina wire
communicating with the positive side was brought in contact with
the upper surface of the alkali....
“Under these circumstances a vivid action was soon observed
to take place. The potash began to fuse at both its points
of electrization. There was a violent effervescence at the
upper surface; at the lower, or negative surface, there was
no liberation of elastic fluid; but small globules having a
high metallic lustre, and being precisely similar in visible
characters to quicksilver appeared, some of which burnt with
explosion and bright flame, as soon as they were formed, and
others remained, and were merely tarnished, and finally covered
by a white film which formed on their surfaces.”
[G] It is frequently stated that Davy was enabled to isolate
the metals of the alkalis because of the _large_ and
powerful voltaic battery which he had at his disposal in
the Royal Institution. This is not correct. The battery he
employed was of very moderate dimensions, and not by any
means extraordinary in power. It was the success he thus
achieved that caused the large battery, which is probably
referred to, to be constructed, by special subscription, in
1809.
The platina, as such, was, he found, in no way connected with the
result: a substance of the same kind was produced when copper, silver,
gold, plumbago, or even charcoal was employed for completing the
circuit.
“Soda when acted upon in the same manner as potash, exhibited
an analogous result; but the decomposition demanded greater
intensity of action in the batteries, or the alkali was required
to be in much thinner and smaller pieces.”
“The substance produced from potash remained fluid at the
temperature of the atmosphere at the time of its production; that
from soda, which was fluid in the degree of heat of the alkali
during its formation, became solid on cooling, and appeared
having the lustre of silver.”
It would seem from his description of its properties that the potassium
he obtained was most probably alloyed with sodium derived from impure
potash. Potassium is solid up to 143° F.; but, as Davy subsequently
found, an alloy of potassium and sodium is fluid at ordinary
temperatures.
When the potassium was exposed to air its metallic lustre was
immediately destroyed, and it was ultimately wholly reconverted into
potash by absorption of oxygen and moisture.
With the substance from soda the appearance and effects were analogous.
When heated in oxygen to a sufficiently high temperature, both
substances burnt with a brilliant white flame.
On account of their alterability on exposure to air, Davy had
considerable difficulty in preserving and confining them so as to
examine the properties of the new substances. As he says, like the
_alkahests_ imagined by the alchemists, they acted more or less upon
almost every body to which they were exposed.
He eventually found that they might be preserved in naphtha.
The “basis” of potash at 50° F. was a soft and malleable solid with the
lustre of polished silver.
“At about the freezing point of water it becomes harder and
brittle, and when broken in fragments, exhibits a crystallized
texture, which in the microscope seems composed of beautiful
facets of a perfect whiteness and high metallic splendour.”
It may be converted into vapour at a temperature approaching a
red-heat, and may be distilled unchanged; it is a perfect conductor
of electricity and an excellent conductor of heat. Its most marked
difference from the common run of metals was its extraordinarily low
specific gravity. Davy endeavoured to gain an approximation to its
relative weight by comparing the weight of a globule with that of an
equal-sized globule of mercury.
“Taking the mean of 4 experiments, conducted with great care,
its specific gravity at 62° Fahrenheit, is to that of mercury as
10 to 223, which gives a proportion to that of water nearly as 6
to 10; so that it is the lightest fluid body known. In its solid
form it is a little heavier.”
Although no great stress can be laid on numbers so obtained, they serve
to indicate that Davy had not yet obtained the pure metal. The real
ratio of the specific gravities of potassium and mercury is as 10 to
154.
An account is then given of the behaviour of potassium towards oxygen,
oxymuriatic acid gas [chlorine], hydrogen, water, alcohol, ether,
the various mineral acids, phosphorus, sulphur, mercury, a number of
metallic oxides, and the various forms of glass.
The “basis” of soda is described as a white opaque substance of the
lustre and general appearance of silver. It is soft and malleable, and
is a good conductor of heat and electricity. Its specific gravity was
found by flotation in a mixture of oil of sassafras and naphtha to be
0·9348 (the true specific gravity of sodium is 0·974). It was found to
fuse at about 180° F. (the real melting-point of sodium is 197·5°). Its
action on a number of substances--oxygen, hydrogen, water, etc.--is
then described, and its general behaviour contrasted with that of the
“basis” of potash.
Davy then attempted, by synthetical experiments, to determine the
amount of the “metallic bases” in potash and soda respectively, and,
considering the extremely small quantities he had to operate upon, the
results are fairly accurate.
He then enters upon some general observations on the relations of the
“bases” of potash and soda to other bodies.
“Should the bases of potash and soda be called metals? The
greater number of philosophical persons to whom this question
has been put, have answered in the affirmative. They agree with
metals in opacity, lustre, malleability, conducting powers as
to heat and electricity, and in their qualities of chemical
combination.
“Their low specific gravity does not appear a sufficient reason
for making them a new class; for amongst the metals themselves
there are remarkable differences in this respect, ... and in the
philosophical division of the classes of bodies, the analogy
between the greater number of properties must always be the
foundation of arrangement.
“On this idea, in naming the bases of potash and soda, it will
be proper to adopt the termination which, by common consent, has
been applied to other newly discovered metals, and which, though
originally Latin, is now naturalized in our language.
“Potasium [_sic_] and sodium are the names by which I have
ventured to call the new substances; and whatever changes of
theory, with regard to the composition of bodies, may hereafter
take place, these terms can scarcely express an error; for
they may be considered as implying simply the metals produced
from potash and soda. I have consulted with many of the most
eminent scientific persons in this country, upon the methods of
derivation, and the one I have adopted has been the one most
generally approved. It is perhaps more significant than elegant.
But it was not possible to found names upon specific properties
not common to both; and though a name for the basis of soda might
have been borrowed from the Greek, yet an analogous one could not
have been applied to that of potash, for the ancients do not seem
to have distinguished between the two alkalies.”
He thinks there is the greater necessity for avoiding any theoretical
views in terms because the time is yet far distant for a complete
generalisation of chemical facts, and although the antiphlogistic
explanation of the phenomena has been uniformly adopted, the motive for
employing it has been rather a sense of its beauty and precision than a
conviction of its permanency and truth.
“The discovery of the agencies of the gases destroyed the
hypothesis of Stahl. The knowledge of the powers and effects
of the etherial substances may at a future time possibly act
a similar part with regard to the more refined and ingenious
hypothesis of Lavoisier; but in the present state of our
knowledge, it appears the best approximation that has been made
to a perfect logic of chemistry.”
Led by analogy, Davy soon convinced himself that the volatile
alkali--ammonia--also contained oxygen, and in amount not less than 7
or 8 per cent. It is not necessary to go into detail concerning the
experiments on which this erroneous conclusion was founded. Davy was
subsequently made aware of his error; but at the time he seemed anxious
to overturn--as, indeed, he did in the end, but on other grounds--the
Lavoisierian doctrine that oxygen was the principle of acidity, by
showing that it was equally the principle of alkalescence.
In concluding his paper, he mentions that he has begun experiments on
the alkaline earths.
“From analogy alone it is reasonable to expect that the alkaline
earths are compounds of a similar nature to the fixed alkalies,
peculiar highly combustible metallic bases united to oxygen. I
have tried some experiments upon barytes and strontites, and they
go far towards proving that this must be the case.”
“Barytes and strontites have the strongest relations to the
fixed alkalies of any of the earthy bodies; but there is a chain
of resemblances through lime, magnesia, glucina, alumina, and
silex. And by the agencies of batteries sufficiently strong, and
by the application of proper circumstances, there is no small
reason to hope that even these refractory bodies will yield their
elements to the methods of analysis by electrical attraction and
repulsion.”
Although certain of the conjectures with which the paper terminates
have been proved to be erroneous, others have been shown to be sound.
Thus he points out that the metals of the alkalis will undoubtedly
prove powerful agents for analysis:
“Having an affinity for oxygen stronger than any other known
substances they may possibly supersede the application of
electricity to some of the undecompounded bodies.”
Such is a brief summary of the contents of one of the most classical
papers in the _Philosophical Transactions_. Its publication created an
extraordinary sensation, not less profound, and certainly more general
from the very nature of the subject, than that which followed his first
Bakerian lecture. That potash and soda should contain metals--and such
metals!--was undreamt of, and was a shock to the settled convictions
of persons who, like the Aberdonian professor, declared that this “ane
Davy was a vera troublesome person in chemistry.”
But this “troublesome person” had well nigh ceased from troubling
any more. Almost immediately after the delivery of his lecture he
collapsed--struck down by an illness which nearly proved fatal, and
for weeks his life hung on a thread. He had been in a low feverish
condition for some time previously, and a great dread had fallen upon
him that he should die before he had completed his discoveries. It
was in this condition of body and mind that he applied himself to
the task of putting together an account of his results. Four days
after this was given to the world he took to his bed, and he remained
there for nine weeks. Such a blow following hard on such a triumph,
aroused the liveliest sympathy. The doors of the Royal Institution
were beset by anxious inquirers. His physicians, Babington, Frank, and
Baillie, tended him with the greatest assiduity. Mrs. Greenwood, the
housekeeper, and his cousin, Edmund Davy, nursed him night and day. So
great was the popular feeling that, when he was at the worst, written
reports of his condition at various periods of the day had to be posted
in the hall. The strength of the feeling may be gleaned, too, from the
sentences with which Dr. Dibdin began his lecture introductory to the
session of 1808:--
“The Managers of this Institution have requested me to impart
to you that intelligence, which no one who is alive to the best
feelings of human nature can hear without the mixed emotions of
sorrow and delight.
“Mr. Davy, whose frequent and powerful addresses from this place,
supported by his ingenious experiments, have been so long and so
well known to you, has for the last five weeks been struggling
between life and death. The effects of these experiments recently
made in illustration of his late splendid discovery, added to
consequent bodily weakness, brought on a fever so violent as to
threaten the extinction of life. Over him it might emphatically
be said in the language of our immortal Milton, that
‘... Death his dart
Shook, but delayed to strike.’
“If it had pleased Providence to deprive the world of all further
benefit from his original talents and intense application there
has certainly been sufficient already effected by him to entitle
him to be classed among the brightest scientific luminaries of
his country.”
After having given an outline of Davy’s investigations “at the
particular request of the Managers,” Dr. Dibdin proceeds:--
“These may justly be placed amongst the most brilliant and
valuable discoveries which have ever been made in chemistry,
for a great chasm in the chemical system has been filled up; a
blaze of light has been diffused over that part which before was
utterly dark; and new views have been opened, so numerous and
interesting, that the more any man who is versed in chemistry
reflects on them, the more he finds to admire and to heighten his
expectation of future important results.
“Mr. Davy’s name, in consequence of these discoveries, will be
always recorded in the annals of science amongst those of the
most illustrious philosophers of his time. His country with
reason will be proud of him, and it is no small honour to the
Royal Institution that these great discoveries have been made
within its walls; in that laboratory, and by those instruments,
which from the zeal of promoting useful knowledge have, with so
much propriety, been placed at the disposal and for the use of
its most excellent professor of chemistry.”
Dr. Dibdin then informs his auditors that Davy’s illness, severe as it
had been, was now beginning to abate, and that it may be reasonably
hoped that the period of convalescence was not very remote.
His bodily weakness, however, continued for some time, and it was not
until the middle of March that he was able to resume his duties as
lecturer. His mind, as his note-books show, much more quickly recovered
its wonted vigour. Perhaps it was in that condition of melancholy and
debility produced by sickness, which he regarded as favourable to
intellectual exertion, when, as he says, “the mind necessarily becomes
contemplative when the body is no longer active, and the empire of
sensation yields to that of imagination,” that he finished the poem
beginning:--
“Lo! o’er the earth the kindling spirits pour
The flames of life that bounteous Nature gives;
The limpid dew becomes the rosy flower,
The insensate dust awakes, and moves, and lives.”
It is too long to give here, but of all his poetical effusions it is
perhaps the best, as it certainly is the most highly-polished.
One proof of what Davy was to the Royal Institution is seen in the
position to which it was reduced in consequence of his protracted
illness. In the early part of the previous December the Managers made
the following announcement:--
“Mr. Davy, having been confined to his bed this last fortnight by
a severe illness, the Managers are under the painful necessity of
giving notice that the lectures will not commence until the first
week of January next.”
By the interruption of the lectures the income of the Institution
was greatly diminished; it fell from £4,141 in the preceding year to
£1,560. This was the low-water mark of its financial state. How acute
was the condition may be seen from the report of the Visitors in 1808.
Davy, although better, was still in bed, confined there by the want
of a sofa in his room. This was not provided by the Managers until
January 25th, when, as the minutes tell us, they furnished him with one
at a cost of three guineas. One would have thought he might have had
Albemarle Street blocked with sofas if some of those lady-friends who
sent him sonnets, and intrigued for his company at their salons, had
only known of his condition.
The laboratory journals show that on April 19th he was able to resume
his experiments, and that he proceeded to attack the composition
of muriatic [hydrochloric] acid. The note runs, “Indications of the
decomposition of muriatic acid. To use every effort to ensure accuracy
in the results.” He seems to have decomposed muriatic acid gas by means
of charcoal terminals, and also to have acted on a mixture of dry
calcium chloride and mercury.
On June 30th he contributed a paper to the Royal Society on
“Electro-Chemical Researches on the Decomposition of the Earths; with
Observations on the Metals obtained from the alkaline Earths, and on
the Amalgam procured from Ammonia.”
That the earths would turn out to be related to the metals was surmised
by Becher and Stahl. Boyle considered it possible that metals might
be produced from them, and Neumann described unsuccessful experiments
to obtain a metal from quicklime. Bergman imagined that baryta was
a metallic calx, and Baron that alumina contained a metal. The
supposition that the calces were all compounds of metals was, of
course, a part of the antiphlogistic doctrine; but Lavoisier never
hazarded any conjecture as to the nature of potash and soda. It went
almost without saying therefore that when Davy had demonstrated the
real character of the fixed alkalis, the alkaline earths would be found
to have an analogous constitution.
The attempts made by Davy to decompose the alkaline earths by methods
similar to those adopted in the case of potash or soda were not
very successful, and it was only when he had received intimation
from Berzelius that they might be procured in the form of amalgams
by operating in contact with mercury that he obtained any decisive
results. In no case, however, was he able to prepare a pure metal,
and his description of the physical properties of the substances
he actually procured is exceedingly meagre. He seems to have been
satisfied for the moment in demonstrating that--
“The evidence for the composition of the alkaline earths is of
the same kind as that for the composition of the common metallic
oxides; and the principles of their decomposition are precisely
similar, the inflammable matters in all cases separating at the
negative surface in the voltaic circuit, and the oxygen at the
positive surface.”
“These new substances will demand names; and on the same
principles as I have named the bases of the fixed alkalies,
potassium and sodium, I shall venture to denominate the metals
from the alkaline earths barium, strontium, calcium and magnium;
the last of these words is undoubtedly objectionable but
magnesium has been already applied to metallic manganese [by
Bergman] and would consequently have been an equivocal term.”
However, as he states in his “Elements of Chemical Philosophy,” “the
candid criticisms of some philosophical friends” induced him to
subsequently change the name to magnesium.
He next made “Inquiries Relative to the Decomposition of Alumine,
Silex, Zircone, and Glucine,” but although he made a large number of
trials, the results were equivocal.
“Had I been so fortunate,” he says, “as to have obtained more
certain evidences on this subject, and to have procured the
metallic substances I was in search of, I should have proposed
for them the names of silicium, alumium, zirconium, and glucium.”
One of the most interesting sections of the paper relates to the
production of a so-called amalgam from ammonia, first obtained by
Berzelius and Pontin. This curious substance has been the subject of
much investigation, and little doubt is now entertained that it is
merely a mercurial froth, as first stated by Daniell--that is, mercury
distended by ammonia and hydrogen gases. Davy, however, saw in it the
proof of the presence of oxygen in ammonia, and of the existence of
what he called “the compound basis” of ammonia. He says:--
“The more the properties of the amalgam obtained from ammonia
are considered the more extraordinary do they appear. Mercury by
combination with about 1/12000 part of its weight of new matter
is rendered a solid, yet has its specific gravity diminished
from 13·5 to 3, and it retains all its metallic characters;
its colour, lustre, opacity, and conducting powers remaining
unimpaired. It is scarcely possible to conceive that a substance
which forms with mercury so perfect an amalgam, should not be
metallic in its own nature; and on this idea to assist the
discussion concerning it, it may be conveniently termed ammonium.”
Davy’s term “ammonium” is still retained in chemical nomenclature, but
there is at present no evidence for the independent existence of such
an entity; the so-called ammonium amalgam is certainly no proof.
On December 15th, 1808, he delivered his third Bakerian lecture. It was
entitled “An Account of some new analytical Researches on the Nature
of certain Bodies, particularly the Alkalies, Phosphorus, Sulphur,
Carbonaceous Matter, and the Acids hitherto undecompounded, with some
general Observations on Chemical Theory.” Although this is one of
the longest and most laboured of Davy’s papers, it is, perhaps, one
of the least satisfactory. It is a record of many experiments with
few definite results. Few as these were, they yet paved the way for
consequences of the greatest importance. Gay Lussac and Thenard, on the
publication of Davy’s second Bakerian lecture, succeeded in devising a
method by which larger quantities of potassium might be obtained than
by the electrolytic process. It consisted in passing molten potash
over heated metallic iron and condensing the volatilised potassium in
naphtha. On heating potassium in ammonia, they found that hydrogen was
obtained together with potash, whence they concluded that potassium
was a _hydruret of potash_. This experiment was repeated by Davy; he
observed the formation of a substance since known as _potassamide_,
and completely disproved the conjecture of the French chemists. His
experiments on sulphur, phosphorus, and the various forms of carbon
were, however, wholly fallacious, and his conclusions as to the
non-elementary nature of these substances were erroneous, and were
subsequently corrected by him. His work on the decomposition of boracic
acid is, however, accurate, and he has every right to be considered as
an independent discoverer, with Thenard, of the element subsequently
called by him _boron_. At first Davy was inclined “to consider the
boracic basis as metallic in its nature,” and to propose for it the
name of _boracium_. His experiments with “fluoric acid” were vitiated
by the circumstance that he worked with a mixture of hydrofluoric
acid and silicon fluoride. Unwittingly he obtained small quantities
of silicon, although he failed to recognise the individuality of this
substance. Nor were the experiments with muriatic acid more decisive.
Incidentally he obtained the two chlorides of phosphorus, but for a
time their true nature escaped him, although he gives a fairly accurate
description of their main properties.
The paper, although containing an account of much experimental work,
was evidently put together in haste; it would have been better for
his reputation had he delayed its publication. He seems to have been
conscious of its imperfections, and to have sought to strengthen his
conclusions by new experiments which he gives in an appendix. These,
so far from substantiating his views, increased his doubts, and it
is remarkable how he misinterpreted the phenomena he observed. Thus
in one series of experiments he obtained considerable quantities of
the “alcohol of sulphur of Lampadius,” and attempted to ascertain its
nature, but his preconceptions as to the non-elementary nature of
carbon and sulphur prevented him from recognising that it is a sulphide
of carbon.
One explanation of this untoward haste is to be found in the position
in which Davy was placed. He simply _hungered_ for scientific fame,
and his appetite grew by what it fed on. There was at the time
the most intense spirit of rivalry between the English and French
chemists--it was a phase of the national feeling which actuated the
two peoples--and, in spite of his phrases, Davy keenly felt what he
considered an intrusion into his own field of work. His illness had
thrown him back, and the French chemists had stolen a march on him
in the meantime. Moreover, he had Berzelius on his flank. All these
circumstances, whilst they impelled him to activity, were unfavourable
in a man of Davy’s temperament to the incubatory period, “the wambling
in the wame” process, which is often needed before the true aspect and
meaning of things are perceived; and there is no doubt that the fear
of being anticipated urged him to the expression of hypotheses and
surmises which at a later and calmer period he regretted and renounced.
But such was his position in England at this period, that a Bakerian
lecture seemed to be expected from him at each succeeding session of
the Royal Society as a matter of course, and he was always ready to
respond to the expectation, even if he did not invariably satisfy it.
On November 16th, 1809, he read his fourth Bakerian lecture. It
was “On some new Electrochemical Researches on various Objects,
particularly the metallic Bodies, from the Alkalies and Earths, and on
some Combinations of Hydrogene.” He begins by again drawing attention
to the various surmises which had been made respecting the true nature
of potassium and sodium. Although these substances had been isolated,
and in the hands of chemists for upwards of two years, their properties
were so extraordinary when compared with those of the metals in
general, that many philosophers hesitated to consider them as true
metals. Gay Lussac and Thenard, as already mentioned, regarded them as
compounds of potash or soda with hydrogen; Curaudau as combinations of
carbon or carbon and hydrogen with the alkalis; whilst an ingenious
inquirer in this country communicated to Nicholson’s Journal his
belief that they were really composed of oxygen and hydrogen! Davy,
in the light of the fuller knowledge he obtained from Gay Lussac and
Thenard’s paper in the “Mem. d’Arcueil”--a copy of which he owed to
Berthollet--had no difficulty in again proving “that by the operation
of potassium upon ammonia, it is not a _metallic_ body that is
decompounded, but the volatile alkali, and that the hydrogen produced
does not arise from the potassium, as is asserted by the French
chemists, but from the _ammonia_.”
M. Curaudau’s hypothesis is shown to be based upon the accidental
association of naphtha with the metals he employed. In repeating some
experiments of Ritter’s, designed to show that potassium contained
hydrogen, Davy was led to the discovery of _telluretted hydrogen_, the
properties of which he describes in some detail. Tellurium at that time
was regarded as a metal, but Davy points out its strong analogies to
sulphur, with which element, indeed, it is now classed. Incidentally
he throws light upon the nature of the intolerably fetid product known
as “the fuming liquor of Cadet,” obtained by distilling acetate of
potash with arsenious oxide. On account of its extreme inflammability,
it was thought by Davy that this liquid might possibly be a pyrophorus
or volatile alloy of potassium and arsenic.
“From a repetition of the process I find that though potash is
decompounded in this operation yet that the volatile substance
is not an alloy of potassium but contains charcoal and arsenic
probably with hydrogen. The gases not absorbable by water given
off in this operation are peculiar. Their smell is intensely
fetid. They are inflammable, and seem to contain charcoal,
arsenic and hydrogen: whether they are mixtures of various gases,
or a single compound, I am not at present able to decide.”
So far as it goes, this description of the nature of the substance
is correct; it was Bunsen, in 1837, who first demonstrated the real
character of “the fuming liquor of Cadet.”
The paper is noteworthy for the clear distinction which is drawn for
the first time between potash hydrate (potassium hydroxide of modern
nomenclature) and potassium oxide, the product formed by heating the
metal in ordinary oxygen.
There is much in the rest of the paper that is ingenious and
suggestive, and not a few isolated facts that seem to have been lost
sight of, or rediscovered by subsequent observers, such, for example,
as the action of potassium upon metallic iron--an action which has
vitiated the attempts to determine the vapour density of that metal in
iron vessels. It is curious to note with what persistency Davy clings
to the belief that nitrogen will turn out to be a compound substance,
and with what pertinacity he importunes it to give up its components.
At times he thinks he is on the verge of proof. “I hope on Thursday,”
he wrote to his friend Children, “to show you nitrogen as a complete
wreck, torn to pieces in different ways.” But still nitrogen, with
that passive immutability which is characteristic of it, in spite of
every form of torture, remained whole and indissoluble. On this point
he wrote in the Laboratory Journal under date February 15th:--“Were a
description, indeed, to be given of all the experiments I have made,
of all the difficulties I have encountered, of the doubts that have
occurred, and the hypotheses formed----.” But the sentence was not
finished. The attack was renewed and continued throughout the whole of
the spring and summer, until, fairly baffled, Davy confessed himself
beaten, and turned his attention to other matters. The condition of his
laboratory at this time may be gleaned from the following note in the
Journal:--
“Objects much wanted in the laboratory of the Royal Institution:
cleanliness, neatness and regularity.
“The laboratory must be cleaned every morning when operations are
going on before ten o’clock.
“It is the business of W. Payne to do this, and it is the duty of
Mr. E. Davy to see that it is done and to take care of and keep
in order the apparatus.
“There must be in the laboratory pen, ink, paper, and wafers, and
these must not be kept in the slovenly manner in which they are
usually kept. I am now writing with a pen and ink such as was
never used in any other place.”
Then follows a list of articles wanting, “including most of the common
metallic and saline solutions.”
“The laboratory is constantly in a state of dirt and confusion.
“There must be a roller with a coarse towel for washing the hands
and a basin of water and soap, and every week at least a whole
morning must be devoted to the inspection and ordering of the
voltaic battery.”
It would be interesting to know the comments of the persons named in
this note as to the cause of the dirt and confusion which reigned in
the laboratory. Davy was perfectly reckless with apparatus; with him
to think was to act, and he frequently had half a dozen experiments
going on simultaneously, upon disconnected parts of the same inquiry.
Anyone who has had the opportunity of seeing his laboratory notes,
or of glancing over the rough drafts of his memoirs, which have
been preserved by the pious care of Faraday, will appreciate the
significance of the remarks upon his writing materials. His usual
method of erasure was by dipping his finger in the ink-pot; and, if we
may be pardoned the use of the colloquialism, he was simply “Death on
pens!”