UC-NR
THE
IMPOSITION
OF THE
FIXED ALKALIES
AND
ALKALINE EARTHS.
BY
HUMPHRY DAVY,
(1807-1808.)
aiemWc Club IReptfnta,
No, 6,
(gfemfiic Cfufi (Reprtnt0 (Uo. 6.
THE
DECOMPOSITION
OF THE
FIXED ALKALIES
AND
ALKALINE EARTHS.
BY
HUMPHRY DAVY,
(1807-1808).
VERSITY)
OF J?
EDINBURGH :
WILLIAM F. CLAY, 18 TEVIOT PLACE.
LONDON :
SIMPKIN, MARSHALL, HAMILTON, KENT & CO. LTD.
1894.
PREFACE.
THE present reprint contains the Bakerian Lecture
delivered by Davy before the Royal Society in
1807, and also part of a paper communicated by him to
the same Society in the .folio wingjear.
The former is the first published record of the experi-
ments by which Davy proved the compound nature of
the alkalies, and prepared the metals potassium and
sodium. Fuller details as to the properties and re-
actions of the metals were given in subsequent papers.
The second paper above mentioned is, for the most
part, a description of similar experiments carried out
upon the earths and alkaline earths. At first Davy had
some difficulty in getting satisfactory results- with these,
but ultimately he succeeded in preparing moderate
quantities of amalgams of the alkaline-earth metals and
of magnesium. Only that section of the paper which
describes these successful experiments is now reprinted.
H. M.
THE BAKERIAN LECTURE, ON SOME
NEW PHENOMENA OF CHEMICAL
CHANGES PRODUCED BY ELECTRI-
CITY, PARTICULARLY THE DECOM-
POSITION OF THE FIXED ALKALIES,
AND THE EXHIBITION OF THE
NEW SUBSTANCES WHICH CONSTI-
TUTE THEIR BASES ; AND ON THE
GENERAL NATURE OF ALKALINE
BODIES*
Read Nov. 19, 1807.
I. Introduction.
IN the Bakerian Lecture which I had the honour of
presenting to the Royal Society last year, I described
a number of decompositions and chemical changes pro-
duced in substances of known composition by electricity,
and I ventured to conclude from the general principles
on which the phenomena were capable of being explained,
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 course of a laborious ex-
perimental application of the powers of electro-chemical
analysis, to bodies which have appeared simple when
* [From "Philosophical Transactions" for 1808, vol. 98, pp.
1-44.]
6 Davy.
examined by common chemical agents, or which at least
have never been decomposed, it has been my good fortune
to obtain new and singular results.
Such of the series of experiments as are in a tolerably
mature state, and capable of being arranged in a con-
nected order, I shall detail in the following sections,
particularly those which demonstrate the decomposition
and composition of the fixed alkalies, and the production
of the new and extraordinary bodies which constitute
their bases.
In speaking of novel methods of investigation, I shall
not fear to be minute. When the common means of
chemical research have been employed, I shall mention
only results. 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 this Lecture. It is proper to state,
however, that when general facts are mentioned, they are
such only as have been deduced from processes carefully
performed and often repeated.
II. On the Methods used for the Decomposition of the
fixed Alkalies.
The researches I had made on the decomposition of
acids, and of alkaline and earthy neutral compounds,
proved that the powers of electrical decomposition were
proportional to the strength of the opposite electricities
in the circuit, and to the conducting power and degree of
concentration of the materials employed.
In the first attempts, that I made on the decomposition
of the fixed alkalies, I acted upon aqueous solutions of
potash and soda, saturated at common temperatures, by
the highest electrical power I could command, and which
Decomposition of the Fixed Alkalies. 7
was produced by a combination of VOLTAIC batteries
belonging to the Royal Institution, containing 24 plates
of copper and zinc of 12 inches square, 100 plates of 6
inches, and 150 of 4 inches square, charged with solu-
tions of alum and nitrous acid ; but in these cases, though
there was a high intensity of action, the water of the
solutions alone was affected, and hydrogene and oxygene
disengaged with the production of much heat and violent
effervescence.
The presence of water appearing thus to prevent any
decomposition, I used potash in igneous fusion. By
means of a stream of oxygene gas from a gasometer
applied to the flame of a spirit lamp, which was thrown
on a platina spoon containing potash, this alkali was kept
for some minutes in a strong red heat, and in a state of
perfect fluidity. The spoon was preserved in communi-
cation with the positive side of the battery of the power
of 100 of 6 inches, highly charged ; and the connection
from the negative side was made by a platina wire.
By this arrangement some brilliant phenomena were
produced. The potash appeared a conductor in a high
degree, and as long as the communication was preserved,
a most intense light was exhibited at the negative wire,
and a column of flame, which seemed to be owing to the
developement of combustible matter, arose from the point
of contact.
When the order was changed, so that the platina spoon
was made negative, a vivid and constant light appeared
at the opposite point : there was no effect of inflammation
round it ; but aeriform globules, which inflamed in the
atmosphere, rose through the potash.
The platina, as might have been expected, was con-
siderably acted upon ; and in the cases when it had been
negative, in the highest degree.
The alkali was apparently dry in thi^ejcrjeriment ; and it
8 Davy.
seemed probable that the inflammable matter arose from
its decomposition. The residual potash was unaltered ;
it contained indeed a number of dark grey metallic par-
ticles, but these proved to be derived from the platina.
I tried several experiments, on the electrization of
potash rendered fluid by heat, with the hopes of being
able to collect the combustible matter, but without
success ; and I only attained my object, by employing
electricity as the common agent for fusion and decom-
position.
Though potash, perfectly dried by ignition, is a non-
conductor, yet it is rendered a conductor, by a very slight
addition of moisture, which does not perceptibly destroy
its aggregation; and in this state it readily 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 con-
ducting 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 ; and a platina wire, communicating with
the positive side, was brought in contact with the upper
surface of the alkali. The whole apparatus was in the
open atmosphere.
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.
Decomposition of the Fixed Alkalies. 9
These globules, numerous experiments soon shewed to
be the substance I was in search of, and a peculiar
inflammable principle the basis of potash. I found that
the platina was in no way connected with the result,
except as the medium for exhibiting the electrical powers
of decomposition ; and a substance of the same kind was
produced when pieces of copper, silver, gold, plumbago,
or even charcoal were employed for compleating the
circuit.
The phenomenon was independent of the presence of
air ; I found that it took place when the alkali was in the
vacuum of an exhausted receiver.
The substance was likewise produced from potash
fused by means of a lamp, in glass tubes confined by
mercury, and furnished with hermetically inserted platina
wires by which the electrical action was transmitted. But
this operation could not be carried on for any considerable
time ; the glass was rapidly dissolved by the action of the
alkali, and this substance soon penetrated through the
body of the tube.
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. With the battery of 100 of 6 inches in full
activity I obtained good results from pieces of potash
weighing from 40 to 70 grains, and of a thickness which
made the distance of the electrified metallic surfaces
nearly a quarter of an inch ; but with a similar power it
was impossible to produce the effects of decomposition on
pieces of soda of more than 15 or 20 grains in weight,
and that only when the distance between the wires was
about \ or T ^- of an inch.
The substance produced from potash remained fluid at
the temperature of the atmosphere at the time of its pro-
io Davy.
duction ; 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.
When the power of 250 was used, with a very high
charge for the decomposition of soda, the globules often
burnt at the moment of their formation, and sometimes
violently exploded and separated into smaller globules,
which flew with great velocity through the air in a state
of vivid combustion, producing a beautiful effect of con-
tinued jets of fire.
III. Theory of the Decomposition of the fixed Alkalies ;
their Composition, and Production.
As in all decompositions of compound substances
which I had previously examined, at the same time that
combustible baseswere developed at the negative surface in
the electrical circuit, oxygene was produced, and evolved
or carried into combination at the positive surface, it was
reasonable to conclude that this substance was generated
in a similar manner by the electrical action upon the
alkalies ; and a number of experiments made above mer-
cury, with the apparatus for excluding external air, proved
that this was the case.
When solid potash, or soda in its conducting state,
was included in glass tubes furnished with electrified
platina wires, the new substances were generated at the
negative surfaces ; the gas given out at the other surface
proved by the most delicate examination to be pure oxy-
gene ; and unless an excess of water was present, no gas
was evolved from the negative surface.
In the synthetical experiments, a perfect coincidence
likewise will be found.
I mentioned that the metallic lustre of the substance
from potash immediately became destroyed in the atmo-
sphere, and that a white crust formed upon it. This crust
Decomposition of the Fixed Alkalies. n
I soon found to be pure potash, which immediately
deliquesced, and new quantities were formed, which in
their turn attracted moisture from the atmosphere till the
whole globule disappeared, and assumed the form of a
saturated solution of potash.*
When globules were placed in appropriate tubes con-
taining common air or oxygene gas confined by mercury,
an absorption of oxygene took place ; a crust of alkali
instantly formed upon the globule ; but from the want of
moisture for its solution, the process stopped, the interior
being defended from the action of the gas.
With the substance from soda, the appearances and
effects were analogous.
When the substances were strongly heated, confined in
given portions of oxygene, a rapid combustion with a bril-
liant white flame was produced, and the metallic globules
were found converted into a white and solid mass, which
in the case of the substance from potash was found to be
potash, and in the case of that from soda, soda.
Oxygene gas was absorbed in this operation, and
nothing emitted which affected the purity of the residual
air.
The alkalies produced were apparently dry, or at least
contained no more moisture than might well be conceived
to exist in the oxygene gas absorbed ; and their weights
considerably exceeded those of the combustible matters
consumed.
* Water likewise is decomposed in the process. We shall here-
after see that the bases of the fixed alkalies act upon this substance
with greater energy than any other known bodies. The minute
theory of the oxydation of the bases of the alkalies in the free air, is
this : oxygene gas is first attracted by them, and alkali formed.
This alkali speedily absorbs water. This water is again decomposed.
Hence, during the conversion of a globule into alkaline solution,
there is a constant and rapid disengagement of small quantities of
gas.
1 2 Davy.
The processes on which these conclusions are founded
will be fully described hereafter, when the minute details
which are necessary will be explained, and the proportions
of oxygene, and of the respective inflammable substances
which enter into union to form the fixed alkalies, will be
given.
It appears then, that in these facts there is the same
evidence for the decomposition of potash and soda into
oxygene and two peculiar substances, as there is for the
decomposition of sulphuric and phosphoric acids and
the metallic oxides into oxygene and their respective
combustible bases.
In the analytical experiments, no substances capable
of decomposition are present but the alkalies and a minute
portion of moisture ; which seems in no other way essen-
tial to the result, than in rendering them conductors at
the surface : for the new substances are not generated till
the interior, which is dry, begins to be fused ; they explode
when in rising through the fused alkali they come in con-
tact with the heated moistened surface ; they cannot be
produced from crystallized alkalies, which contain much
water; and the effect produced by the electrization of
ignited potash, which contains no sensible quantity of
water, confirms the opinion of their formation independ-
ently of the presence of this substance.
The combustible bases of the fixed alkalies seem to be
repelled as other combustible substances, by positively
electrified surfaces, and attracted by negatively electrified
surfaces, and the oxygene follows the contrary order ; *
or the oxygene being naturally possessed of the negative
energy, and the bases of the positive, do not remain in
combination when either of them is brought into an
electrical state opposite to its natural one. In the syn-
thesis, on the contrary, the natural energies or attractions
* See Bakerian Lecture 1806, page 28 Phil. Trans, for 1807.
Decomposition of the Fixed Alkalies, 13
come in equilibrium with each other ; and when these are
in a low state at common temperatures, a slow combina-
tion is effected ; but when they are exalted by heat, a
rapid union is the result ; and as in other like cases with"
the production of fire. A number of circumstances
relating to the agencies of the bases of the alkalies will
be immediately stated, and will be found to offer con-
firmations of these general conclusions.
IV. On the Properties and Nature of the Basis of
Potash.
After I had detected the bases of the fixed alkalies, I
had considerable difficulty to preserve and confine them
so as to examine their properties, and submit them to
experiments ; for, like the alkahests imagined by the
alchemists, they acted more or less upon almost every
body to which they were exposed.
The fluid substance amongst all those I have tried, on
which I find they have least effect, is recently distilled
naphtha. In this material, when excluded from the air,
they remain for many days without considerably changing,
and their physical properties may be easily examined in
the atmosphere when they are covered by a thin film
of it.
'The basis of potash at 60 FAHRENHEIT, the tempera-
ture in which I first examined it, appeared, as I have
already mentioned, in small globules possessing the
metallic lustre, opacity, and general appearance of mer-
cury ; so that when a globule of mercury was placed near
a globule of the peculiar substance, it was not possible to
detect a difference by the eye.
"At 60 FAHRENHEIT it is however only imperfectly
fluid, for it does not readily run into a globule when its
shape is altered; at 70 it becomes more fluid; and at
100 its fluidity is perfect, so that different globules may
14 Davy.
be easily made to run into one. At 50 FAHRENHEIT it
becomes a soft and malleable solid, which has the lustre
of polished silver ; and 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 per-
fect whiteness and high metallic splendour.
To be converted into vapour, it requires a temperature
approaching that of the red heat ; and when the experi-
ment is conducted under proper circumstances, it is found
unaltered after distillation.
It is a perfect conductor of electricity. When a spark
from the VOLTAIC battery of 100 of 6 inches is taken upon
a large globule in the atmosphere, the light is green, and
combustion takes place at the point of contact only.
When a small globule is used, it is completely dissipated
with explosion accompanied by a most vivid flame, into
alkaline fumes.
It is an excellent conductor of heat.
Resembling the metals in all these sensible properties,
it is however remarkably different from any of them in
specific gravity ; I found that it rose to the surface of
naphtha distilled from petroleum, and of which the specific
gravity was .861 and it did not sink in double distilled
naphtha, the specific gravity of which was about .770, that
of water being considered as i. The small quantities
in which it is produced by the highest electrical
powers, rendered it very difficult to determine this quality
with minute precision. I endeavoured to gain approxi-
mations on the subject by comparing the weights of per-
fectly equal globules of the basis of potash and mercury.
I used the very delicate balance of the Royal Institution,
which when loaded with the quantities I employed, and
of which the mercury never exceeded ten grains, is sensible
at least to the oV(7 of a rain - Taking the mean of 4
Decomposition of the Fixed Alkalies. 15
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, but even in this state
when cooled to 40 FAHRENHEIT, it swims in the double
distilled naphtha.
The chemical relations of the basis of potash are still
more extraordinary than its physical ones.
I have already mentioned its alkalization and combus-
tion in oxygene gas. It combines with oxygene slowly
and without flame at all temperatures that I have tried
below that of its vaporization. But at this temperature
combustion takes place, and the light is of a brilliant
whiteness and the heat intense. When heated slowly in
a quantity of oxygene gas not sufficient for its complete
conversion into potash, and at a temperature inadequate
to its inflammation, 400 FAHRENHEIT, for instance, its
tint changes to that of a red brown, and when the heat is
withdrawn, all the oxygene is found to be absorbed, and
a solid is formed of a greyish colour, which partly con-
sists of potash and partly of the basis of potash in a lower
degree of oxygenation, and which becomes potash by
being exposed to water, or by being again heated in fresh
quantities of air.
The substance consisting of the basis of potash com-
bined with an under proportion of oxygene, may likewise
be formed by fusing dry potash and its basis together
under proper circumstances. The basis rapidly loses its
metallic splendour ; the two substances unite into a com-
pound, of a red brown colour when fluid, and of a dark
grey hue when solid ; and this compound soon absorbs
its full proportion of oxygene when exposed to the air,
and is wholly converted into potash.
And the same body is often formed in the analytical
1 6 Davy.
experiments when the action of the electricity is intense,
and the potash much heated.
The basis of potash when introduced into oxymuriatic
acid gas burns spontaneously with a bright red light,
and a white salt proving to be muriate of potash is
formed.
When a globule is heated in hydrogene at a degree
below its point of vaporization, it seems to dissolve in it,
for the globule diminishes in volume, and the gas explodes
with alkaline fumes and bright light, when suffered to pass
into the air ; but by cooling, this spontaneous detonating
property is destroyed, and the basis is either wholly or
principally deposited.
The action of the basis of potash on water exposed to
the atmosphere is connected with some beautiful pheno-
mena. When it is thrown upon water, or when it is
brought into contact with a drop of water at common
temperatures, it decomposes it with great violence, an
instantaneous explosion is produced with brilliant flame,
and a solution of pure potash is the result.
In experiments of this kind, an appearance often occurs
similar to that produced by the combustion of phos-
phuretted hydrogene ; a white ring of smoke, which
gradually extends as it rises into the air.
When water is made to act upon the basis of potash
out of the contact of air and preserved by means of a
glass tube under naphtha, the decomposition is violent ;
and there is much heat and noise, but no luminous
appearance, and the gas evolved when examined in the
mercurial or water pneumatic apparatus is found to be
pure hydrogene.
When a globule of the basis of potash is placed upon
ice it instantly burns with a bright flame, and a deep hole
is made in the ice, which is found to contain a solution
of potash.
Decomposition of the Fixed Alkalies. \J
The theory of the action of the basis of potash upon
water exposed to the atmosphere, though complicated
changes occur, is far from being obscure. The pheno-
mena seem to depend on the strong attractions of the
basis for oxygene and of the potash formed for water. The
heat, which arises from two causes, decomposition and
combination, is sufficiently intense to produce the inflam-
mation. Water is a bad conductor of heat ; the globule
swims exposed to air ; a part of it, there is the greatest
reason to believe, is dissolved by the heated nascent
hydrogene ; and this substance being capable of spon-
taneous inflammation, explodes, and communicates the
effect of combustion to any of the basis that may be yet
uncombined.
When a globule confined out of the contact of air is
acted upon by water, the theory of decomposition is very
simple, the heat produced is rapidly carried off, so that
there is no ignition ; and a high temperature being re-
quisite for the solution of the basis in hydrogene this
combination probably does not take place, or at least it
can have a momentary existence only.
The production of alkali in the decomposition of water
by the basis of potash is demonstrated in a very simple
and satisfactory manner by dropping a globule of it upon
moistened paper tinged with turmeric. At the moment
that the globule comes in 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,
and acting upon the paper precisely as dry caustic
potash.
So strong is the attraction of the basis of potash for
oxygene, and so great the energy of its. action upon water,
that it discovers and decomposes the small quantities of
water contained in alcohol and ether, even when they are
carefully purified.
1 8 Davy.
In ether this decomposition is connected with an
instructive result. Potash is insoluble in this fluid ; and
when the basis of potash is thrown into it, oxygene is fur-
nished to it, and hydrogene gas disengaged, and the alkali
as it forms renders the ether white and turbid.
In both these inflammable compounds the energy of
its action is proportional to the quantity of water they
contain, and hydrogene and potash are the constant
result.
The basis of potash when thrown into solutions of the
mineral acids, inflames and burns on the surface. When
it is plunged by proper means beneath the surface
enveloped in potash, surrounded by naphtha, it acts upon
the oxygene with the greatest intensity, and all its effects
are such as may be explained from its strong affinity for
this substance. In sulphuric acid a white saline substance
with a yellow coating, which is probably sulphate of
potash surrounded by sulphur, and a gas which has the
smell of sulphureous acid, and which probably is a mix-
ture of that substance with hydrogene gas, are formed.
In nitrous acid, nitrous gas is disengaged, and nitrate of
potash formed.
The basis of potash readily combines with the simple
inflammable solids, and with the metals; with phosphorus
and sulphur, it forms compounds similar to the metallic
phosphurets and sulphurets.
When it is brought in contact with a piece of phos-
phorus, and pressed upon, there is a considerable action :
they become fluid together, burn, and produce phosphate
of potash. When the experiment is made under naphtha,
their combination takes place without the liberation of
any elastic matter, and they form a compound which has
a considerably higher point of fusion than its two con
stituents,and which remains a soft solid in boiling naphtha.
In its appearance it perfectly agrees with a metallic phos-
Decomposition of the Fixed Alkalies. 19
phuret, it is of the colour of lead, and when spread out,
has a lustre similar to polished lead. When exposed to
air at common temperatures, it slowly combines with oxy-
gene, and becomes phosphate of potash. When heated
upon a plate of platina, fumes exhale from it, and it does
not burn till it attains the temperature of the rapid com-
bustion of the basis of potash.
When the basis of potash is brought in contact with
sulphur in fusion, in tubes filled with the vapour of naphtha,
they combine rapidly with the evolution of heat and light,
and a grey substance, in appearance like artificial sul-
phuret of iron, is formed, which if kept in fusion, rapidly
dissolves the glass, and becomes bright brown. When
this experiment is made in a glass tube hermetically
sealed, no gas is liberated if the tube is opened under
mercury ; but when it is made in a tube connected with
a mercurial apparatus, a small quantity of sulphuretted
hydrogene is evolved, so that the phenomena are similar
to those produced by the union of sulphur with the metals
in which sulphuretted hydrogene is likewise disengaged,
except that the ignition is stronger.* When the union is
effected in the atmosphere, a great inflammation takes
* The existence of hydrogene in sulphur, is rendered very probable
by the ingenious researches of M. Berthollet Jun. Annales de Chimie,
Fevrier 1807 page 143. The fact is almost demonstrated by an
experiment which I saw made by W. Clayfield, Esq. at Bristol, in
1799. Copper filings and powdered sulphur, in weight in the pro-
portion of three to one rendered very dry, were heated together in a
retort, connected with a mercurial pneumatic apparatus. At the
moment of combination a quantity of elastic fluid was liberated
amounting to 9 or 10 times the volume of the materials employed,
and which consisted of sulphuretted hydrogene mixed with
sulphureous acid. The first mentioned product, there is every
reason to believe, must be referred to the sulphur, the last probably
to the copper, which it is easy to conceive may have become slightly
and superficially oxidated during the processes of filing and drying
by heat.
2O Davy.
place, and sulphuret of potash is formed. The sul-
phuretted basis likewise gradually becomes oxygenated
by exposure to the air, and is finally converted into
sulphate.
The new substance produces some extraordinary and
beautiful results with mercury. When one part of it is
added to 8 or 10 parts of mercury in volume at 60
FAHRENHEIT, they instantly unite and form a substance
exactly like mercury in colour, but which seems to have
less coherence, for small portions of it appear as flattened
spheres. When a globule is made to touch a globule of
mercury about twice as large, they combine with con-
siderable heat j the compound is fluid at the temperature
of its formation ; but when cool it appears as a solid
metal, similar in colour to silver. If the quantity of the
basis of potash is still farther increased, so as to be about
^th the weight of the mercury, the amalgam increases
in hardness, and becomes brittle. The solid amalgam, in
which the basis is in the smallest proportion, seems to
consist of about i part in weight of basis and 70 parts of
mercury, and is very soft and malleable.
When these compounds are exposed to air, they
rapidly absorb oxygene ; potash which deliquesces is
formed ; and in a few minutes the mercury is found pure
and unaltered.
When a globule of the amalgam is thrown into water,
it rapidly decomposes it with a hissing noise ; potash is
formed, pure hydrogene disengaged, and the mercury
remains free.
The fluid amalgam of mercury and this substance dis-
solves all the metals I have exposed to it ; and in this
state of union, mercury acts on iron and platina.
When the basis of potash is heated with gold, or silver,
or copper, in a close vessel of pure glass, it rapidly acts
upon them ; and when the compounds are thrown into
Decomposition of the Fixed Alkalies. 21
water, this fluid is decomposed, potash formed, and the
metals appear to be separated unaltered.
The basis of potash combines with fusible metal, and
forms an alloy with it, which has a higher point of fusion
than the fusible metal.
The action of the basis of potash upon the inflam-
mable oily compound bodies, confirms the other facts of
the strength of its attraction for oxygene.
On naphtha colourless and recently distilled, as I have
already said, it has very little power of action ; but in
naphtha that has been exposed to the air it soon oxidates,
and alkali is formed, which unites with the naphtha into
a brown soap that collects round the globule.
On the concrete oils (tallow, spermaceti, wax, for in-
stance), when heated, it acts slowly, coaly matter is
deposited, a little gas * is evolved, and a soap is formed ;
but in these cases it is necessary that a large quantity of
the oil be employed. On the fluid fixed oils it produces
the same effects, but more slowly.
* When a globule of the basis of potash is introduced into any of
the fixed oils heated, the first product is pure hydrogene which
arises from the decomposition of the water absorbed by the crust of
potash during the exposure to the atmosphere. The gas evolved,
when the globule is freed from this crust, I have found to be car-
bonated hydrogene requiring more than an equal bulk of oxygene
gas for its complete saturation by explosion. I have made a great
number of experiments, which it would be foreign to the object of
this lecture to give in minute detail, on the agencies of the basis of
potash on the oils. Some anomalies occurred which led to the
inquiry, and the result was perfectly conclusive. Olive oil, oil of
turpentine, and naphtha when decomposed by heat, exhibited as
products different proportions of charcoal, heavy inflammable gas,
empyreumatic oily matter, and water, so that the existence of
oxygene in them was fully proved ; and accurate indications of the
proportions of their elements might be gained by their decomposition
by the basis of potash. Naphtha of all furnished least water and
carbonic acid, and oil of turpentine the most. ^
/ OF THE r >.
(UNIVERSITY)
V <-, . J
22 Davy.
By heat likewise it rapidly decomposes the volatile oils;
alkali is formed, a small quantity of gas is evolved, and
charcoal is deposited.
When the basis of potash is thrown into camphor in
fusion, the camphor soon becomes blackened, no gas is
liberated in the process of decomposition, and a sapon-
aceous compound is formed ; which seems to shew that
camphor contains more oxygene than the volatile oils.
The basis of potash readily reduces metallic oxides
when heated in contact with them. When a small
quantity of the oxide of iron was heated with it, to a
temperature approaching its point of distillation, there
was a vivid action; alkali and grey metallic particles,
which dissolved with effervescence in muriatic acid,
appeared. The oxides of lead and the oxides of tin
were revived still more rapidly ; and when the basis of
potash was in excess, an alloy was formed with the revived
metal.
In consequence of this property, the basis of potash
readily decomposes flint glass and green glass, by a gentle
heat ; alkali is immediately formed by oxygene from the
oxides, which dissolves the glass, and a new surface is
soon exposed to the agent.
At a red heat, even the purest glass is altered by the
basis of potash : the oxygene in the alkali of the glass
seems to be divided between the two bases, the basis of
potash and the alkaline basis in the glass, and oxides, in
the first degree of oxygenation, are the result. When the
basis of potash is heated in tubes made of plate glass
filled with the vapour of naphtha, it first acts upon the
small quantity of the oxides of cobalt and manganese in
the interior surface of the glass, and a portion of alkali
is formed. As the heat approaches to redness, it begins
to rise in vapour, and condenses in the colder parts of the
tube ; but at the point where the heat is strongest, a part
Decomposition of the Fixed Alkalies. 23
of the vapour seems to penetrate the glass, rendering it of
a deep red brown colour ; and by repeatedly distilling and
heating the substance in a close tube of this kind, it finally
loses its metallic form, and a thick brown crust, which
slowly decomposes water, and which combines with oxy-
gene when exposed to air forming alkali, lines the
interior of the tube, and in many parts is found penetrat-
ing through its substance.*
In my first experiments on the distillation of the basis
of potash, I had great difficulty in accounting for these
phenomena ; but the knowledge of the substance it forms
in its first degree of union with oxygene, afforded a satis-
factory explanation.
V. On the Properties and Nature of the Basis of Soda.
The basis of soda, as I have already mentioned, is a
solid at common temperatures. It is white, opaque, and
when examined under a film of naphtha, has the lustre
and general appearance of silver. It is exceedingly mal-
leable, and is much softer than any of the common
metallic substances. When pressed upon by a platina
blade, with a small force, it spreads into thin leaves, and
a globule of the T \yth or T \th of an inch in diameter is
easily spread over a surface of a quarter of an inch,t and
this property does not diminish when it is cooled to 32
FAHRENHEIT.
It conducts electricity and heat in a similar manner to
the basis of potash ; and small globules of it inflame
* This is the obvious explanation in the present state of our
knowledge ; but it is more than probable that the silex of the glass
likewise suffers some change, and probably decomposition. This
subject I hope to be able to resume on another occasion.
f Globules may lie easily made to adhere and form one mass by
strong pressure : so that the property of welding, which belongs to
iron and platina at a white heat only, is possessed by this substance
at common temperatures.
24 Davy.
by the voltaic electrical spark, and burn with bright
explosions.
Its specific gravity is less than that of water. It swims
in oil of sassafras of 1.096, water being i, and sinks in
naphtha of specific gravity .861. This circumstance
enabled me to ascertain the point with precision. I mixed
together oil of sassafras and naphtha, which combine very
perfectly, observing the proportions till I had composed
a fluid, in which it remained at rest above or below ; and
this fluid consisted of nearly twelve parts naphtha, and
five of oil of sassafras, which gives a specific gravity to
that of water, nearly as nine to ten, or more accurately
as .9348 to i.
The basis of soda has a much higher point of fusion
than the basis of potash ; its parts begin to lose their
cohesion at about 120 FAHRENHEIT, and it is a perfect
fluid at about 180, so that it readily fuses under boiling
naphtha.
I have not yet been able to ascertain at what degree
of heat it is volatile ; but it remains fixed in a state of
ignition at the point of fusion of plate glass.
The chemical phenomena produced by the basis of
soda, are analogous to those produced by the basis of
potash ; but with such characteristic differences as might
be well expected.
When the basis of soda is exposed to the atmosphere,
it immediately tarnishes, and by degrees becomes covered
with a white crust, which deliquesces much more slowly
than the substance which forms on the basis of potash.
It proves, on minute examination, to be pure soda.
The basis of soda combines with oxygene slowly, and
without luminous appearance at all common temperatures ;
and when heated, this combination becomes more rapid ;
but no light is emitted till it has acquired a temperature
nearly that of ignition.
Decomposition of the Fixed Alkalies. 25
The flame that it produces in oxygene gas is white, and
it sends forth bright sparks, occasioning a very beautiful
effect ; in common air, it burns with light of the colour of
that produced during the combustion of charcoal, but
much brighter.
The basis of soda when heated in hydrogene, seemed
to have no action upon it. When introduced into
oxymuriatic acid gas, it burnt vividly with numerous
scintillations of a bright red colour. Saline matter was
formed in this combustion, which, as might have been
expected, proved to be muriate of soda.
Its operation upon water offers most satisfactory
evidence of its nature. -When thrown upon this fluid, it
produces a violent effervescence, with a loud hissing
noise ; it combines with the oxygene of the water to form
soda, which is dissolved, and its hydrogene is disengaged.
In this operation there is no luminous appearance ; and
it seems probable that even in the nascent state hydrogene
is incapable of combining with it.*
When the basis of soda is thrown into hot water, the
decomposition is more violent, and in this case a few
scintillations are generally observed at the surface of the
fluid ; but this is owing to small particles of the basis,
which are thrown out of the water sufficiently heated, to
burn in passing through the atmosphere. When, however,
a globule is brought in contact with a small particle of
water, or with moistened paper, the heat produced (there
being no medium to carry it off rapidly) is usually sufficient
for the accension of the basis.
The basis of soda acts upon alcohol and ether precisely
in a similar manner with the basis of potash. The water
that they contain is decomposed ; soda is rapidly formed,
and hydrogene disengaged.
* The more volatile metals only seem capable of uniting with
hydrogene ; a circumstance presenting an analogy.
26 Davy.
The basis of soda, when thrown upon the strong acids,
acts upon them with great energy. When nitrous acid
is employed, a vivid inflammation is produced ; with
muriatic and sulphuric acid, there is much heat generated,
but no light.
When plunged, by proper means, beneath the surface
of the acids, it is rapidly oxygenated ; soda is produced,
and the other educts are similar to those generated by the
action of the basis of potash.
With respect to the fixed and volatile oils and naphtha
in their different states, there is a perfect coincidence
between the effects of the two new substances, except in
the difference of the appearances of the saponaceous
compounds formed : those produced by the oxydation
and combination of the basis of soda being of a darker
colour, and apparently less soluble.
The basis of soda, in its degrees of oxydation, has pre-
cisely similar habits with the basis of potash.
When it is fused with dry soda, in certain quantities,
there is a division of oxygene between the alkali and the
base ; and a deep brown fluid is produced, which becomes
a dark grey solid on cooling, and which attracts oxygene
from the air, or which decomposes water, and becomes soda.
The same body is often formed in the analytical pro-
cesses of decomposition, and it is generated when the
basis of soda is fused in tubes of the purest plate glass.
There is scarcely any difference in the visible 'pheno-
mena of the agencies of the basis of soda, and that of
potash on sulphur, phosphorus, and the metals.
It combines with sulphur in close vessels filled with the
vapour of naphtha with great vividness, with light, heat,
and often with explosion from the vaporization of a
portion of sulphur, and the disengagement of sulphuretted
hydrogene gas. The sulphuretted basis of soda is of a
deep grey colour.
Decomposition of the Fixed Alkalies. 27
The phosphuret has the appearance of lead, and forms
phosphate of soda by exposure to air, or by combustion.
The basis of soda in the quantity of -* v , renders
mercury a fixed solid of the colour of silver, and the
combination is attended with a considerable degree of
heat.
It makes an alloy with tin, without changing its colour,
and it acts upon lead and gold when heated. I have not
examined its habitudes with any other metals, but in its
state of alloy, it is soon converted into soda by exposure
to air, or by the action of water, which it decomposes
with the evolution of hydrogene.
The amalgam of mercury and the basis of soda, seems
to form triple compounds with other metals. I have tried
iron and platina, which I am inclined to believe remain
in combination with the mercury, when it is deprived of
the new substance by exposure to air.
The amalgam of the basis of soda and mercury likewise
combines with sulphur and forms a triple compound of a
dark grey colour.
VI. On the Proportions of the peculiar Bases and Oxygene
in Potash and Soda.
The facility of combustion of the bases of the alkalies,
and the readiness with which they decomposed water,
offered means fully adequate for determining the propor-
tions of their ponderable constituent parts.
I shall mention the general methods of the experiments,
and the results obtained by the different series, which
approach as near to each other ns can be expected
in operations performed on such small quantities of
materials.
For the process in oxygene gas, I employed glass tubes
containing small trays made 'of thin leaves of silver or
28 Davy.
other noble metals, on which the substance to be burnt,
after being accurately weighed or compared with a globule
of mercury, equal in size,* was placed : the tube was
small at one end, curved, and brought to a fine point, but
suffered to remain open ; and the other end was fitted to
a tube communicating with a gazometer, from which the
oxygene gas was introduced, for neither water nor mercury
could be used for filling the apparatus. The oxygene gas
was carried through the tube till it was found that the
whole of the common air was expelled. The degree of
its purity was ascertained by suffering a small quantity to
pass into the mercurial apparatus. The lower orifice was
then hermetically sealed by a spirit lamp, and the upper
part drawn out and finally closed, when the aperture was
so small, as to render the temperature employed incapable
of materially influencing the volume of the gas ; and when
the whole arrangement was made, the combination was
effected by applying heat to the glass in contact with the
metallic tray.
In performing these experiments many difficulties
occurred. When the flame of the lamp was immediately
brought to play upon the glass, the combustion was very
vivid, so as sometimes to break the tube ; and the alkali
generated partly rose in white fumes, which were deposited
upon the glass.
When the temperature was slowly raised, the bases of the
alkalies acted upon the metallic tray and formed alloys,
and in this state it was very difficult to combine them
with their full proportion of oxygene; and glass alone
could not be employed on account of its decomposition
* When the globules were very small, the comparison with mer-
cury, which may be quickly made by means of a micrometer, was
generally employed as the means of ascertaining the weight : for in
this case the globule could be immediately introduced into the tube,
and the weight of mercury ascertained at leisure.
Decomposition of the Fixed Alkalies. 29
by the alkaline bases ; and porcelain is so bad a con-
ductor of heat, that it was not possible to raise it to the
point required for the process, without softening the
glass.
In all cases the globules of the alkaline bases were
carefully freed from naphtha before they were introduced ;
of course a slight crust of alkali was formed before the
combustion, but this could not materially affect the
result ; and when such a precaution was not used, an
explosion generally took place from the vaporization and
decomposition of the film of naphtha surrounding the
globule.
After the combustion, the absorption of gas was ascer-
tained, by opening the lower point of the tube under
water or mercury. In some cases the purity of the
residual air was ascertained, in others the alkali formed
in the tray was weighed.
From several experiments on the synthesis of potash by
combustion, I shall select two, which were made with
every possible attention to accuracy, and under favourable
circumstances, for a mean result.
In the first experiment o. 1 2 grains of the basis were
employed. The combustion was made upon platina, and
was rapid and complete ; and the basis appeared to be
perfectly saturated, as no disengagement of hydrogene
took place when the platina tray was thrown into water.
The oxygene gas absorbed equalled in volume 190 grain
measures of quicksilver ; barometer being at 29.6 inches,
thermometer 62 FAHRENHEIT and this reduced to a
temperature of 60 FAHRENHEIT, and under a pressure
equal to that indicated by 30 inches,* would become
186.67 measures, the weight of which would be about
* In the correction for temperature, the estimations of D ALTON
and GAY LUSSAC are taken, which make gasses expand about
4^5 of the primitive volume for every degree of FAHRENHEIT.
30 Davy.
.0184 grains troy*; but .0184 : .1384 : : 13.29 : 100 ;
and according to this estimation 100 parts of potash will
consist of 86.7 basis, and 13.3 oxygene nearly.
In the second experiment .07 grains of the basis
absorbed at temperature 63 of FAHRENHEIT, and under
pressure equal to 30.1 barometer inches, a quantity of
oxygene equal in volume to 121 grain measures of mer-
cury, and the proper corrections being made as in the
former case, this gas would weigh .01189 grains.
But as .07 + .01 1 89 = .08189 : .07 : : 100 : 85.48 nearly,
and 100 parts of potash will consist of 85.5 of basis and
14.5 of oxygene nearly. And the mean of the two
experiments will be 86.1 of basis to 13.9 of oxygene for
loo parts.
In the most accurate experiment that I made on the
combustion of the basis of soda .08 parts of the basis
absorbed a quantity of oxygene equal to 206 grain
measures of mercury ; the thermometer being at 56
FAHRENHEIT; and the barometer at 29.4; and this
quantity, the corrections being made as before for the
mean temperature and pressure, equals about .02 grains
of oxygene.
And as .08 + .02 = . 10 : .08, : : 100 : 80, and 100 parts
of soda according to this estimation will consist of 80
basis to 20 of oxygene.
In all cases of slow combustion, in which the alkalies
were not carried out of the tray, I found a considerable
increase of weight, but as it was impossible to weigh them
except in the atmosphere, the moisture attracted rendered
* From experiments that I made in 1799, on the specific gravity of
oxygene gas, it would appear that its weight is to that of water as I to
748, and to that of quicksilver as I to 10142. Researches Chem. and
Phil. p. 9 ; and with this estimation, that deducible from the late
accurate researches of Messrs. ALLEN and PEPYS on the Com-
bustion of the Diamond almost precisely agrees- Phil. Trans. 1807,
page 275.
Decomposition of the Fixed Alkalies. 31
the results doubtful ; and the proportions from the weight
of the oxygene absorbed are more to be depended
on. In the experiments in which the processes of
weighing were most speedily performed, and in which no
alkali adhered to the tube, the basis of potash gained
nearly 2 parts for 10, and that of soda between 3 and 4
parts.
The results of the decomposition of water by the bases
of the alkalies were much more readily and perfectly
obtained than those of their combustion.
To check the rapidity of the process, and, in the case
of potash, to prevent any of the basis from being dis-
solved, I employed the amalgams with mercury. I used
a known weight of the bases, and made the amalgams
under naphtha, using about two parts of mercury in
volume to one of basis.
In the first instances I placed the amalgams under
tubes filled with naphtha, and inverted in glasses of
naphtha, and slowly admitted water to the amalgam at
the bottom of the glass ; but this precaution I soon
found unnecessary, for the action of the water was not
so intense but that the hydrogene gas could be wholly
collected.
I shall give an account of the most accurate experi-
ments made on the decomposition of water by the bases
of potash and soda.
In an experiment on the basis of potash conducted
with every attention that I could pay to the minutiae of
the operations, hydrogene gas, equal in volume to 298
grains of mercury, were disengaged by the action of .08
grains of the basis of potash which had been amalgamated
with about 3 grains of mercury. The thermometer at
the end of the process indicated a temperature of 56
FAHRENHEIT, and the barometer an atmospheric pressure
equal to 29.6 inches.
32 Davy.
Now this quantity of hydrogene * would require for its
combustion a volume of oxygene gas about equal to that
occupied by 154.9 grains of mercury, which gives the
weight of oxygene required to saturate the .08 grains of
the basis of potash at the mean temperature and pressure
nearly .0151 grains. And .08 + .0151 =.0951 : .08 : : 100 :
84.1 nearly.
And according to these indications 100 parts of potash
consist of about 84 basis and 16 oxygene.
In an experiment on the decomposition of water by the
basis of soda, the mercury in the barometer standing at
30.4 inches, and in the thermometer at 52 FAHRENHEIT,
the volume of hydrogene gas evolved by the action of
.054 grains of basis equalled that of 326 grains of quick-
silver. Now this at the mean temperature and pressure
would require for its conversion into water, .0172 of oxy-
gene, and . 054 + .0172 = .0712 : .054 :: 100 : 76 nearly;
and according to these indications, TOO parts of soda
consist of nearly 76 basis, and 24 oxygene.
In another experiment made with very great care, .052
of the basis of soda were used; the mercury in the
barometer was at 29.9 inches, and that in the thermo-
meter at 58 FAHRENHEIT. The volume of hydrogene
evolved was equal to that of 302 grains of mercury;
which would demand for its saturation by combustion,
at the mean temperature and pressure .01549 grains of
oxygene; and 100 parts of soda, according to this pro-
portion, would consist nearly of 77 basis, and 23 oxygene.
The experiments which have been just detailed, are
those in which the largest quantities of materials were
employed ; I have compared their results, however, with
the results of several others, in which the decomposition
of water was performed with great care, but in which the
* Researches Chem. and Phil, page 287.
Decomposition of the Fixed Alkalies. 33
proportion of the bases was still more minute : the largest
quantity of oxygene indicated by these experiments was,
for potash 17, and for soda 26 parts in 100, and the
smallest 13, and 19; and comparing all the estimations,
it will probably be a good approximation to the truth, to
consider potash as composed of about 6 parts basis and
i of oxygene ; and soda, as consisting of 7 basis and 2
oxygene.
VII. 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 affirma-
tive. They agree with metals in opacity, lustre, mallea-
bility, 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, platina being nearly four times as heavy as
tellurium ; * and in the philosophical division of the
classes of bodies, the analogy between the greater number
of properties must always be the foundation of arrange-
ment.
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 dis-
* Tellurium is not much more than six times as heavy as the basis
of soda. There is great reason to believe that bodies of a similar
chemical nature to the bases of potash and soda will be found of
intermediate specific gravities between them and the lightest of the
common metals. Of this subject, I shall treat again in the text in
some of the following pages.
C
34 Davy.
covered metals, and which, though originally Latin, is
now naturalized in our language.
Potasium and Sodium are the names by which I have
ventured to call the two 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.
The more caution is necessary in avoiding any theor-
etical expression in the terms, because the new electro-
chemical phenomena that are daily becoming disclosed,
seem distinctly to shew that the mature time for a com-
plete generalization of chemical facts is yet far distant ;
and though, in the explanations of the various results of
experiments that have been detailed, the antiphlogistic
solution of the phenomena has been uniformly adopted,
yet the motive for employing it has been rather a sense
of its beauty and precision, than a conviction of its per-
manency and truth.
The discovery of the agencies of the gasses 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
Decomposition of the Fixed Alkalies. 35
approximation that has been made to a perfect logic of
chemistry.
Whatever future changes may take place in theory,
there seems however every reason to believe that the
metallic bases of the alkalies, and the common metals,
will stand in the same arrangement of substances ; and as
yet we have no good reasons for assuming the compound
nature of this class of bodies.*
The experiments in which it is said that alkalies,
metallic oxides, and earths may be formed from air and
water alone, in processes of vegetation, have been always
made in an inconclusive manner ;t for distilled water, as
* A phlogistic chemical theory might certainly be defended, on
the idea that the metals are compounds of certain unknown bases
with the same matter as that existing in hydrogene ; and the metallic
oxides, alkalies and acids compounds of the same bases with water ;
but in this theory more unknown principles would.be assumed than
in the generally received theory. It would be less elegant and less
distinct. In my first experiments on the distillation of the basis of
potash finding hydrogene generally produced, I was led to compare
the phlogistic hypothesis with the new facts, and I found it fully
adequate to the explanation. More delicate researches however
afterwards proved that in the cases when inflammable gasses
appeared, water, or some body in which hydrogene is admitted to
exist, was present.
f The explanation of VAN HELMONT of his fact of the pro-
duction of earth in the growth of the willow, was completely
overturned by the researches of WOODWARD. Phil. Trans. Vol.
XXI. page 193.
The conclusions which M. BRACONNOT has very lately drawn
from his ingenious experiments, Annales de Chimie, Fevrier 1807,
page 187, are rendered of little avail in consequence of the circum-
stances stated in the text. In the only case of vegetation in which
the free atmosphere was excluded, the seeds grew in white sand,
which is stated to have been purified by washing in muriatic acid ;
but such a process was insufficient to deprive it of substances which
might afford carbon, or various inflammable matters. Carbonaceous
matter exists in several stonep which afford a whitish or greyish
powder ; and when in a stone, the quantity of carbonate of lime is
36 Davy.
I have endeavoured to show,* may contain both saline
and metallic impregnations ; and the free atmosphere
almost constantly holds in mechanical suspension solid
substances of various kinds.
In the common processes of nature, all the products of
living beings may be easily conceived to be elicited from
known combinations of matter. The compounds of iron,
of the alkalies, and earths, with mineral acids, generally
abound in soils. From the decomposition of basaltic,
porphyritic, t and granitic rocks, there is a constant supply
of earthy alkaline and ferruginous materials to the sur-
face of the earth. In the sap of all plants that have been
examined, certain neutrosaline compounds, containing
potash, or soda, or iron, have been found. From plants
they may be supplied to animals. And the chemical
tendency of organization seems to be rather to combine
substances into more complicated and diversified arrange-
ments, than to reduce them into simple elements.
very small in proportion to the other earthy ingredients, it is
scarcely acted on by acids.
* Bakerian Lecture, 1806, page 8.
f In the year 1804, for a particular purpose of geological enquiry,
I made an analysis of the porcelain clay of St. Stevens, in Cornwall,
which results from the decomposition of the feldspar of fine-grained
granite. I could not detect in it the smallest quantity of alkali. In
making some experiments on specimens of the undecompounded
rock taken from beneath the surface, there were evident indications
of the presence of a fixed alkali, which seemed to be potash. So that
it is very probable that the decomposition depends on the operation
of water and the carbonic acid of the atmosphere on the alkali
forming a constituent part of the chrystalline matter of the feldspar,
which may disintegrate from being deprived of it.
Decomposition of the Fixed Alkalies. 37
VIII. On the Nature of Ammonia and alkaline Bodies in
general ; with Observations on some prospects oj
Discovery offered by the preceding Facts.
Ammonia is a substance, the chemical composition of
which has always been considered of late years as most
perfectly ascertained, and the apparent conversion of it
into hydrogene and nitrogene, in the experiments of
SCHEELE, PRIESTLEY, and the more refined and accurate
experiments of BERTHOLLET, had left no doubt of its
nature in the minds of the most enlightened chemists.
All new facts must be accompanied however by a train
of analogies, and often by suspicions with regard to the
accuracy of former conclusions. As the two fixed alkalies
contain a small quantity of oxygene united to peculiar
bases, may not the volatile alkali likewise contain it ? was
a query which soon occurred to me in the course of
enquiry ; and in perusing the accounts of the various
experiments made on the subject, some of which I had
carefully repeated, I saw no reason to consider the cir-
cumstance as impossible. For supposing hydrogene and
nitrogene to exist in combination with oxygene in low
proportion, this last principle might easily disappear in the
analytical experiments of decomposition by heat and
electricity, in water deposited upon the vessels employed
or dissolved in the gasses produced.
Of the existence of oxygene in volatile alkali I soon
satisfied myself. When charcoal carefully burnt and
freed from moisture was ignited by the VOLTAIC battery
of the power of 250 of 6 and 4 inches square, in a small
quantity of very pure ammoniacal gas : * a great expansion
* The apparatus in which this experiment was made is described
in page 214 Journal of the Royal Institution. The gas was confined
by mercury which had been previously boiled to expel any moisture
that might adhere to it. The ammonia had been exposed to the
38 Davy.
of the aeriform matter took place, and a white substance
formed, which collected on the sides of the glass tube
employed in the process ; and this matter, exposed to the
action of diluted muriatic acid, effervesced, so that it was
probably carbonate of ammonia.
A process of another kind offered still more decisive
results. ' In this the two mercurial gazometers of the
invention of Mr PEPYS, described in No. XIV. of the
Phil. Trans, for 1807, were used with the same apparatus,
as that employed by Messrs. ALLEN and PEPYS for the
combustion of the diamond, and these gentlemen kindly
assisted in the experiment.
Very pure ammoniacal gas was passed over iron wire
ignited in a platina tube, and two curved glass tubes were
so arranged as to be inserted into a freezing mixture ; and
through one of these tubes the gas entered into the platina
tube, and through the other, it passed from the platina
tube into the airholder arranged for its reception.
The temperature of the atmosphere was 55 ; but it was
observed that no sensible quantity of water was deposited
in the cooled glass tube transmitting the unaltered
ammonia, but in that receiving it after its exposure to
heat, moisture was very distinct, and the gas appeared in
the airholder densely clouded.
This circumstance seems distinctly to prove the forma-
tion of water in this operation for the decomposition of
ammonia : unless indeed it be asserted that the hydro-
gene and nitrogene gasses evolved hold less water in
solution or suspension than the ammonia decomposed, an
action of dry pure potash, and a portion of it equal in volume to 10980
grains of mercury, when acted on by distilled water, left a residuum
equal to 9 grains of mercury only. So that the gas, there is every
reason to believe, contained no foreign a;riform matter ; for even the
minute residuum may be accounted for by supposing it derived from
air dissolved in the water.
Decomposition of. the Fixed Alkalies. 39
idea strongly opposed by the conclusions of Mr. DALTON*
and the experiments of Messrs. DESORMES and CLEMENT.!
After the gas had been passed several times through
the ignited tube from one gazometer to the other, the
results were examined. The iron wire became converted
superficially into oxide, and had gained in weight T 4 y 4 <j-
parts of a grain, about y 4 ^ of a grain of water were col-
lected from the cooled glass tubes by means of filtrating
paper, and 33.8 cubic inches of gas were expanded into
55.3 cubic inches, and by detonation with oxygene it was
found that the hydrogene gas in these was to the nitro-
gene as 3.2 to i in volume.
It will be useless to enter into the more minute details
of this experiment, as no perfectly accurate data for pro-
portions can be gained from them ; for the whole of the
ammonia was not decomposed, and as the gas had been
prepared by being sent from a heated mixture of sal
ammoniac and quicklime, into the airholder, it was pos-
sible that some solution of ammonia might have been
deposited, which, by giving out new gas during the
operation, would increase the absolute quantity of the
material acted upon.
In examining the results of M. BERTH OLLET'SJ elaborate
experiments on the decomposition of ammonia by elec-
tricity, I was surprised to find that the weight of the
hydrogene and nitrogene produced, rather exceeded than
fell short of that of the ammonia considered as decom-
posed, which was evidently contradictory to the idea of
its containing oxygene. This circumstance, as well as
the want of coincidence between the results and those of
PRIESTLEY and VAN MARUM on the same subject,
induced me to repeat the process of the electrization of
* Manchester Memoirs, Vol. V. Part II. page 535, 1785.
t Annales de Chimie, Vol. XLII. p. 125.
Mtlmoires de f Acadeniie^ 1785, page 324.
40 Davy.
ammonia, and I soon found that the quantities of the
products in their relations to the apparent quantity of
gas destroyed were influenced by many different causes.
Ammonia procured over dry mercury from a mixture
of dry lime and muriate of ammonia, I found deposited
moisture upon the sides of the vessel in which it was
collected, and in passing the gas into the tube for elec-
trization, it was not easy to avoid introducing some of this
moisture, which must have been a saturated solution of
ammonia, at the same time.
In my first trials made upon gas, passed immediately
from the vessel in which it had been collected into the
apparatus, I found the expansion of i of ammonia vary
in different instances from 2.8 to 2.2 measures, but the
proportions of the nitrogene and hydrogene appeared
uniform, as determined by detonation of the mixed gas
with oxygene, and nearly as i to 3 in volume.
To exclude free moisture entirely, I carefully prepared
ammonia in a mercurial airholder, and after it had been
some hours at rest, passed a quantity of it into the
tube for decomposition, which had been filled with dry
mercury. In this case 50 parts became 103 parts by
electrization, and there was still reason to suspect sources
of error.
I had used iron wires not perfectly free from rust, for
taking the spark, and a black film from the mercury
appeared on the sides of the tube. It was probable that
some ammonia had been absorbed by the metallic oxides
both upon the iron and the mercury, which might again
have been given out in the progress of the operation.
I now used recently distilled mercury, which did not
leave the slightest film on the glass tube, and wires of
platina. The ammonia had been exposed to dry caustic
potash, and proved to be equally pure with that men-
tioned in page 37. 60 measures of it, each equal to a
Decomposition of the Fixed Alkalies. 41
grain of water, were electrized till no farther expansion
could be produced, the gas filled a space equal to that
occupied by 108 grains of water. The thermometer in
this experiment was 56, and the barometer at 30.1
inches. The wire of platina transmitting the spark
was slightly tarnished.* The 108 measures of gas care-
fully analyzed, were found to consist of So measures in
volume of hydrogene, and 28 measures of nitrogene.
The results of an experiment that I made in 1799,1
give the weight of 100 cubic inches of ammonia, as 18.18
grains at the mean temperature and pressure. I had
reasons however for suspecting that this estimation might
be somewhat too low, and on mentioning the circumstance
to Messrs. ALLEN and PEPYS, they kindly undertook the
examination of the subject, and Mr. ALLEN soon fur-
nished me with the following data. " In the first experi-
ment 21 cubic inches of ammonia weighed 4.05 grains ;
in a second experiment the same quantity weighed 4.06
grains, barometer 30.65, thermometer 54 FAHRENHEIT."
Now if the corrections for temperature and pressure be
made for these estimations, and a mean taken, TOO cubic
inches of ammonia will weigh 18.67 grains, barometer
being at 30, and thermometer at 60 FAHRENHEIT ; and
if the quantity used in the experiment of decomposition
be calculated upon as cubic inches, 60 will weigh 11.2
grains. But the hydrogene gas evolved equal to 80 will
weigh 1.93 \ grains, and the nitrogene equal to 28, 8.3.
* This most probably was owing to oxydation. When platina is
made positive in the VOLTAIC circuit in contact with solution of
ammonia, it is rapidly corroded. This is an analogous instance.
t Researches Chem.. and Phil. p. 62.
I LAVOISIER'S Elements, p. 569. A cubical inch of hydrogene
is considered as weighing .0239.
Researches Chem. and Phil, page 9. From my experiments 100
cubical inches of nitrogene weigh at the standard temperature and
pressure, 29.6 grains.
42 Davy.
And ii. 2 grains - 1.9 + 8.3 = 10.2. and 11.2-10.2. = !,
all the estimations being made according to the standard
temperature and pressure.
So that in this experiment on the decomposition of
ammonia, the weight of the gasses evolved is less by nearly
YT than that of the ammonia employed ; and this loss
can only be ascribed to the existence of oxygene in the
alkali ; part of which probably combined with the platina
wires employed for electrization, and part with hydro-
gene.
After these ideas the oxygene in ammonia cannot well
be estimated at less than 7 or 8 parts in the hundred ;
and it possibly exists in a larger proportion as the gasses
evolved may contain more water than the gas decom-
posed, which of course would increase their volume and
their absolute weight*
In supposing ammonia a triple compound of nitrogene,
hydrogene, and oxygene, it is no less easy to give a
rational account of the phaenomena of its production and
decomposition, than in adopting the generally received
hypothesis of its composition.
Oxygene, hydrogene, and nitrogene are always present
in cases in which volatile alkali is formed ; and it usually
appears during the decomposition of bodies in which oxy-
gene is loosely attached, as in that of the compounds of
oxygene and nitrogene dissolved in water.
At common temperatures under favourable circum-
stances, the three elements may be conceived capable of
combining and of remaining in union : but at the heat of
* In the present state of our knowledge, perfectly correct data for
proportions cannot probably be gained in any experiments on the
decomposition of ammonia, as it seems impossible to ascertain the
absolute quantity of water in this gas, for electrization, according to
Dr HENRY'S ingenious researches, offers the only means known of
ascertaining the quantity of water in gasses.
Decomposition of the Fixed Alkalies. 43
ignition the affinity of hydrogene for oxygene prevails
over the complex attraction, water is formed, and hydro-
gene and nitrogene are evolved ; and according to these
conclusions, ammonia will bear the same relations to the
fixed alkalies, as the vegetable acids with compound
bases do to the mineral ones with simple bases.
Oxygene then may be considered as existing in, and
as forming, an element in all the true alkalies ; and the
principle of acidity of the French nomenclature, might
now likewise be called the principle of alkalescence.
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 oxygene. I have tried some experiments upon
barytes and strontites ; and they go far towards proving
that this must be the case. When barytes and strontites
moistened with water, were acted upon by the power of
the battery of 250 of 4 and 6, there was a vivid action
and a brilliant light at both points of communication, and
an inflammation at the negative point.
In these cases the water might possibly have inter-
fered. Other experiments gave however more distinct
results.
Barytes and strontites, even when heated to intense
whiteness, in the electrical circuit by a flame supported
by oxygene gas, are non-conductors ; but by means of
combination with a very small quantity of boracic acid,
they become conductors ; and in this case inflammable
matter, which burns with a deep red light in each
instance, is produced from them at the negative surface.
The high temperature has prevented the success of
attempts to collect this substance ; but there is much
reason to believe that it is the basis of the alkaline earth
employed.
Barytes and strontites have the strongest relations to
44 Davy,
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.
In the electrical circuit we have a regular series of
powers of decomposition, from an intensity of action, so
feeble as scarcely to destroy the weakest affinity existing
between the parts of a saline neutral compound, to one
sufficiently energetic to separate elements in the strongest
degree of union, in bodies undecomposable under other
circumstances.
When the powers are feeble, acids and alkalies, and
acids and metallic oxides, merely separate from each
other ; when they are increased to a certain degree, the
common metallic oxides and the compound acids are
decomposed ; and by means still more exalted, the
alkalies yield their elements. And as far as our know-
ledge of the composition of bodies extends, all substances
attracted by positive electricity, are oxygene, or such as
contain oxygene in excess ; and all that are attracted by
negative electricity, are pure combustibles, or such as
consist chiefly of combustible matter.
* The similarity between the properties of earths and metallic
oxides, was noticed in the early periods of chemistry. The poisonous
nature of barytes, and the great specific gravity of this substance as
well as of strontites, led LAVOISIER to the conjecture that they were
of a metallic nature. That metals existed in the fixed alkalies seems
however never to have been suspected. From their analogy to
ammonia, nitrogene and hydrogene have been supposed to be
amongst their elements. It is singular, with regard to this class of
bodies, that those most unlike metallic oxides are the first which
have been demonstrated to be such.
Decomposition of the Fixed Alkalies. 45
The idea of muriatic acid, fluoric acid, and boracic
acid containing oxygene, is highly strengthened by these
facts. And the general principle confirms the conjecture
just stated concerning the nature of the earths.
In the electrization of boracic acid moistened with
water, I find that a dark coloured combustible matter
is evolved at the negative surface ; but the researches
upon the alkalies have prevented me from pursuing
this fact, which seems however to indicate a decomposi-
tion.
Muriatic acid and fluoric acid in their gaseous states
are non-conductors : and as there is every reason to believe
that their bases have a stronger attraction for oxygene than
water, there can be little hope of decomposing them in
their aqueous solutions, even by the highest powers. In
the electrization of some of their combinations there is
however a probability of success.
An immense variety of objects of research is presented
in the powers and affinities of the new metals produced
from the alkalies.
In themselves they will undoubtedly prove powerful
agents for analysis ; and having an affinity for oxygene
stronger than any other known substances, they may
possibly supersede the application of electricity to some
of the undecompounded bodies.
The basis of potash I find oxidates in carbonic acid
and decomposes it, and produces charcoal when heated
in contact with carbonate of lime. It likewise oxidates
in muriatic acid ; but I have had no opportunity of
making the experiment with sufficient precision to ascer-
tain the results.
In sciences kindred to chemistry, the knowledge of the
nature of the alkalies, and the analogies arising in conse-
quence, will open many new views ; they may lead to the
solution of many problems in geology, and shew that
46 Davy.
agents may have operated in the formation of rocks and
earths which have not hitherto been suspected to exist.
It would be easy to pursue the speculative part of this
enquiry to a great extent, but I shall refrain from so
occupying the time of the Society, as the tenour of my
object in this lecture has not been to state hypotheses,
but to bring forward a new series of facts.
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 AM-
MONIA.*
Read June $oth 1808.
III. Attempts to procure the Metals of the alkaline
Earths ; and on their Properties.
To procure quantities of amalgams sufficient for distil-
lation, I combined the methods I had before employed,
with those of M. M. BERZELIUS and PONTIN.
The earths were slightly moistened, and mixed with
one-third of red oxide of mercury, the mixture was placed
on a plate of platina, a cavity was made in the upper part
of it to receive a globule of mercury, of from fifty to 60
* [From "Philosophical Transactions" for 1808, vol. 98, pp.
333-370; part reprinted pp. 341-346.]
Metals obtained from the Alkaline Earths. 47
grains in weight, the whole was covered by a film of
naphtha, and the plate was made positive, and the mercury
negative, by a proper communication with the battery of
five hundred.
The amalgams obtained in this way, were distilled in
tubes of plate glass, or in some cases in tubes of common
glass. These tubes were bent in the middle, and the
extremities were enlarged, and rendered globular by
blowing, so as to serve the purposes of a retort and
receiver.
The tube after the amalgam had been introduced, was
filled with naphtha, which was afterwards expelled by
boiling, through a small orifice in the end corresponding
to the receiver, which was hermetically sealed when the
tube contained nothing but the vapour of naphtha, and
the amalgam.
I found immediately that the mercury rose pure by
distillation from the amalgam, and it was very easy to
separate a part of it ; but to obtain a complete decom-
position was very difficult.
For this nearly a red heat was required, and at a red
heat the bases of the earths instantly acted upon the
glass, and became oxygenated. When the tube was
large in proportion to the quantity of amalgam, the
vapour of the naphtha furnished oxygene sufficient to
destroy part of the bases : and when a small tube was
employed, it was difficult to heat the part used as a retort
sufficient to drive off the whole of the mercury from the
basis, without raising too .highly the temperature of the
part serving for the receiver, so as to burst the tube.*
In consequence of these difficulties, in a multitude of
* When the quantity of the amalgam was about fifty or sixty
grains, I found that the tube could not be conveniently less than
one-sixth of an inch in diameter, and of the capacity of about half
a cubic inch,
48 Davy.
trials, I. obtained only a very few successful results, and
in no case could I be absolutely certain that there was
not a minute portion of mercury still in combination with
the metals of the earths.
In the best result that I obtained from the distillation
of the amalgam of barytes, the residuum appeared as a
white metal of the colour of silver. It was fixed at all
common temperatures, but became fluid at a heat below
redness, and did not rise in vapour when heated to redness,
in a tube of plate glass, but acted violently upon the
glass, producing a black mass, which seemed to contain
barytes, and a fixed alkaline basis, in the first degree of
oxygenation.*
* From this fact, compared with other facts that have been stated,
P- 336, it may be conjectured, that the basis of barytes has a higher
affinity for oxygene than sodium ; and hence, probably the bases of
the earths will be more powerful instruments for detecting oxygene,
than the bases of the alkalies.
I have tried a number of experiments on the action of potassium on
bodies supposed simple, and on the undecompounded acids. From
the affinity of the metal for oxygene, and of the acid for the substance
formed, I had entertained the greatest hopes of success. It would
be inconsistent with the object of this paper to enter into a full detail
of the methods of operation ; I hope to be able to state them fully
to the Society at a future time, when they shall be elucidated by
further researches ; I shall now merely mention the general results,
to shew that I have not been tardy in employing the means which
were in my power, towards effecting these important objects.
When potassium was heated in muriatic acid gas, as dry as it
could be obtained by common chemical means, there was a violent
chemical action with ignition ; and when the potassium was in suffi-
cient quantity, the muriatic acid gas wholly disappeared, and from
one-third to one-fourth of its volume of hydrogene was evolved, and
muriate of potash was formed.
On fluoric acid gas, which had been in contact with glass, the
potassium produced a similar effect ; but the quantity of hydrogene
generated was only one-sixth or one-seventh of the volume of gas,
and a white mass was formed, which principally consisted of fluate
Metals obtained from the Alkaline Earths. 49
When exposed to air, it rapidly tarnished, and fell into
a white powder, which was barytes. When this process
was conducted in a small portion of air, the oxygene was
found absorbed, and the nitrogene unaltered; when a
portion of it was introduced into water, it acted upon it
with great violence arid sunk to the bottom, producing
in it barytes ; and hydrogene was generated. The
of potash and silex, hut which emitted fumes of fluoric acid when
exposed to air.
When boracic acid, prepared in the usual manner, that had been
ignited, was heated in a gold tube with potassium, a very minute
quantity of gas only was liberated, which was hydrogene, mixed
with nitrogene, (the last probably from the common air in the tube) ;
borate of potash was -formed, and a black substance, which became
white by exposure to air.
In all these instances there is great reason to believe that the
hydrogene was produced from the water adhering to the acids ; and
the different proportions of it in the different cases, are a strong proof
of this opinion. Admitting this idea, it seems that muriatic acid
gas must contain at least one-eighth or one-tenth of its weight of
water ; and that the water oxygenates in the experiment a quantity
of potassium, sufficient to absorb the whole of the acid.
In the cases of fluoric and boracic acids, there is probably a
decomposition of these bodies ; the black substance produced from
the boracic acid is similar to that which I had obtained from it by
electricity. The quantities that I have operated upon, have been as
yet too small to enable me to separate and examine the products,
and till this is done, no ultimate conclusion can be drawn.
The action of potassium upon muriatic acid gas, indicates a much
larger quantity of water in this substance, than the action of elec*
tricity in Dr. HENRY'S elaborate experiments; but in the one
instance the acid enters into a solid salt, and in the other it remains
aeriform ; and the difficulty of decomposition by electricity, must
increase in proportion as the quantity of water diminishes, so that at
the apparent maximum of electrical effect, there is no reason to
suppose the gas free from water.
Those persons who have supposed hydrogene to be the basis of
muriatic acid may, perhaps, give another solution of the phenomena,
and consider the experiment I have detailed as a proof of this
opinion.
D
5O Davy.
quantities in which I obtained it were too minute for me
to be able to examine correctly, either its physical or
chemical properties. It sunk rapidly in water, and even
in sulphuric acid, though surrounded by globules of
hydrogene, equal to two or three times its volume ; from
which it seems probable, that it cannot be less than four
or five times as heavy as water. It flattened by pressure,
but required a considerable force for this effect.
The metal from strontites sunk in sulphuric acid, and
exhibited the same characters as that from barytes, except
in producing strontites by oxydation.
The metal from lime, I have never been able to examine
exposed to air or under naphtha. In the case in which I
was able to distil the quicksilver from it to the greatest
extent, the tube unfortunately broke, whilst warm, and at
the moment that the air entered, the metal, which had the
colour and lustre of silver, instantly took fire, and burnt
with an intense white light into quicklime.
The metal from magnesia seemed to act upon the glass,
even before the whole of the quicksilver was distilled from
it. In an experiment in which I stopped the process
before the mercury was entirely driven off, it appeared as
a solid, having the same whiteness and lustre as the other
metals of the earths. It sunk rapidly in water, though
surrounded by globules of gas, producing magnesia, and
quickly changed in air, becoming covered with a white
crust, and falling into a fine powder, which proved to be
magnesia.
In several cases in which amalgams of the metals of
the earths, containing only a small quantity of mercury
were obtained, I exposed them to air on a delicate
balance, and always found that during the conversion of
metal into earth, there was a considerable increase of
weight.
J endeavoured to ascertain the proportions of oxygene,
Metals obtained from the Alkaline Earths. 51
and bases, in barytes and strontites, by heating amalgams
of them in tubes filled with oxygene, but without success.
I satisfied myself, however, that when the metals of the
earths were burned in a small quantity of air they absorbed
oxygene, gained weight in the process, and were in the
highly caustic or unslacked state ; for they produced
strong heat by the contact of water, and did not effervesce
during their solution in acids.
The evidence for the composition of the alkaline earths
is then 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 oxygene 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, and would conse-
quently have been an equivocal term.
* BERGMAN, Opusc. torn. ii. p. 200.
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