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 w