MRS. B.
Certainly: the metal, however, would equally have been disengaged. Sir H. Davy has distinguished this new substance by the name of POTASSIUM, which is derived from that of the alkali, from which it is procured. I have some small pieces of it in this phial, but you have already seen it, as it is the metal which we burnt in contact with sulphur.
EMILY.
What is the liquid in which you keep it?
MRS. B.
It is naptha, a bituminous liquid, with which I shall hereafter make you acquainted. It is almost the only fluid in which potassium can be preserved, as it contains no oxygen, and this metal has so powerful an attraction for oxygen, that it will not only absorb it from the air, but likewise from water, or any body whatever that contains it.
EMILY.
This, then, is one of the bodies that oxydates spontaneously without the application of heat?
MRS. B.
Yes; and it has this remarkable peculiarity that it attracts oxygen much more rapidly from water than from air; so that when thrown into water, however cold, it actually bursts into flame. I shall now throw a small piece, about the size of a pin’s head, on this drop of water.
CAROLINE.
It instantaneously exploded, producing a little flash of light! this is, indeed, a most curious substance!
MRS. B.
By its combustion it is reconverted into potash; and as potash is now decidedly a compound body, I shall not enter into any of its properties till we have completed our review of the simple bodies; but we may here make a few observations on its basis, potassium. If this substance is left in contact with air, it rapidly returns to the state of potash, with a disengagement of heat, but without any flash of light.
EMILY.
But is it not very singular that it should burn better in water than in air?
CAROLINE.
I do not think so: for if the attraction of potassium for oxygen is so strong that it finds no more difficulty in separating it from the hydrogen in water, than in absorbing it from the air, it will no doubt be more amply and rapidly supplied by water than by air.
MRS. B.
That cannot, however, be precisely the reason, for when potassium is introduced under water, without contact of air, the combustion is not so rapid, and indeed, in that case, there is no luminous appearance; but a violent action takes place, much heat is excited, the potash is regenerated, and hydrogen gas is evolved.
Potassium is so eminently combustible, that instead of requiring, like other metals, an elevation of temperature, it will burn rapidly in contact with water, even below the freezing point. This you may witness by throwing a piece on this lump of ice.
CAROLINE.
It again exploded with flame, and has made a deep hole in the ice.
MRS. B.
This hole contains a solution of potash; for the alkali being extremely soluble, disappears in the water at the instant it is produced. Its presence, however, may be easily ascertained, alkalies having the property of changing paper, stained with turmeric, to a red colour; if you dip one end of this slip of paper into the hole in the ice you will see it change colour, and the same, if you wet it with the drop of water in which the first piece of potassium was burnt.
CAROLINE.
It has indeed changed the paper from yellow to red.
MRS. B.
This metal will burn likewise in carbonic acid gas, a gas that had always been supposed incapable of supporting combustion, as we were unacquainted with any substance that had a greater attraction for oxygen than carbon. Potassium, however, readily decomposes this gas, by absorbing its oxygen, as I shall show you. This retort is filled with carbonic acid gas.—I will put a small piece of potassium in it; but for this combustion a slight elevation of temperature is required, for which purpose I shall hold the retort over the lamp.
CAROLINE.
Now it has taken fire, and burns with violence! It has burst the retort.
MRS. B.
Here is the piece of regenerated potash; can you tell me why it is become so black?
EMILY.
No doubt it is blackened by the carbon, which, when its oxygen entered into combination with the potassium, was deposited on its surface.
MRS. B.
You are right. This metal is perfectly fluid at the temperature of one hundred degrees; at fifty degrees it is solid, but soft and malleable; at thirty-two degrees it is hard and brittle, and its fracture exhibits an appearance of confused crystallization. It is scarcely more than half as heavy as water; its specific gravity being about six when water is reckoned at ten; so that this metal is actually lighter than any known fluid, even than ether.
Potassium combines with sulphur and phosphorus, forming sulphurets and phosphurets; it likewise forms alloys with several metals, and amalgamates with mercury.
EMILY.
But can a sufficient quantity of potassium be obtained, by means of the Voltaic battery, to admit of all its properties and relations to other bodies being satisfactorily ascertained?
MRS. B.
Not easily; but I must not neglect to inform you that a method of obtaining this metal in considerable quantities has since been discovered. Two eminent French chemists, Thenard and Gay Lussac, stimulated by the triumph which Sir H. Davy had obtained, attempted to separate potassium from its combination with oxygen, by common chemical means, and without the aid of electricity. They caused red hot potash in a state of fusion to filter through iron turnings in an iron tube, heated to whiteness. Their experiment was crowned with the most complete success; more potassium was obtained by this single operation, that could have been collected in many weeks by the most diligent use of the Voltaic battery.
EMILY.
In this experiment, I suppose, the oxygen quitted its combination with the potassium to unite with the iron turnings?
MRS. B.
Exactly so; and the potassium was thus obtained in its simple state. From that time it has become a most convenient and powerful instrument of deoxygenation in chemical experiments. This important improvement, engrafted on Sir H. Davy’s previous discoveries, served but to add to his glory, since the facts which he had established, when possessed of only a few atoms of this curious substance, and the accuracy of his analytical statements, were all confirmed when an opportunity occurred of repeating his experiments upon this substance, which can now be obtained in unlimited quantities.
CAROLINE.
What a satisfaction Sir H. Davy must have felt, when by an effort of genius he succeeded in bringing to light and actually giving existence, to these curious bodies, which without him might perhaps have ever remained concealed from our view!
MRS. B.
The next substance which Sir H. Davy submitted to the influence of the Voltaic battery was Soda, the other fixed alkali, which yielded to the same powers of decomposition; from this alkali too, a metallic substance was obtained, very analogous in its properties to that which had been discovered in potash; Sir H. Davy has called it SODIUM. It is rather heavier than potassium, though considerably lighter than water; it is not so easily fusible as potassium.
Encouraged by these extraordinary results, Sir H. Davy next performed a series of beautiful experiments on Ammonia, or the volatile alkali, which, from analogy, he was led to suspect might also contain oxygen. This he soon ascertained to be the fact, but he has not yet succeeded in obtaining the basis of ammonia in a separate state; it is from analogy, and from the power which the volatile alkali has, in its gaseous form, to oxydate iron, and also from the amalgams which can be obtained from ammonia by various processes, that the proofs of that alkali being also a metallic oxyd are deduced.
Thus, then, the three alkalies, two of which had always been considered as simple bodies, have now lost all claim to that title, and I have accordingly classed the alkalies amongst the compounds, whose properties we shall treat of in a future conversation.
EMILY.
What are the other newly discovered metals which you have alluded to in your list of simple bodies?
MRS. B.
They are the metals of the earths which became next the object of Sir H. Davy’s researches; these bodies had never yet been decomposed, though they were strongly suspected not only of being compounds, but of being metallic oxyds. From the circumstance of their incombustibility it was conjectured, with some plausibility, that they might possibly be bodies that had been already burnt.
CAROLINE.
And metals, when oxydated, become, to all appearance, a kind of earthy substance.
MRS. B.
They have, besides, several features of resemblance with metallic oxyds; Sir H. Davy had therefore great reason to be sanguine in his expectations of decomposing them, and he was not disappointed. He could not, however, succeed in obtaining the basis of the earths in a pure separate state; but metallic alloys were formed with other metals, which sufficiently proved the existence of the metallic basis of the earths.
The last class of new metallic bodies which Sir H. Davy discovered was obtained from the three undecompounded acids, the boracic, the fluoric, and the muriatic acids; but as you are entirely unacquainted with these bodies, I shall reserve the account of their decomposition till we come to treat of their properties as acids.
Thus in the course of two years, by the unparalleled exertions of a single individual, chemical science has assumed a new aspect. Bodies have been brought to light which the human eye never before beheld, and which might have remained eternally concealed under their impenetrable disguise.
It is impossible at the present period to appreciate to their full extent the consequences which science or the arts may derive from these discoveries; we may, however, anticipate the most important results.
In chemical analysis we are now in possession of more energetic agents of decomposition than were ever before known.
In geology new views are opened, which will probably operate a revolution in that obscure and difficult science. It is already proved that all the earths, and, in fact, the solid surface of this globe, are metallic bodies mineralized by oxygen, and as our planet has been calculated to be considerably more dense upon the whole than on the surface, it is reasonable to suppose that the interior part is composed of a metallic mass, the surface of which only has been mineralized by the atmosphere.
The eruptions of volcanos, those stupendous problems of nature, admit now of an easy explanation. For if the bowels of the earth are the grand recess of these newly discovered inflammable bodies, whenever water penetrates into them, combustions and explosions must take place; and it is remarkable that the lava which is thrown out, is the very kind of substance which might be expected to result from these combustions.
I must now take my leave of you; we have had a very long conversation to-day, and I hope you will be able to recollect what you have learnt. At our next interview we shall enter on a new subject.
* By a process analogous to that described, page 155. of this volume.