h it a small piece of lighted tinder
to set fire to it. --This requires being done very quickly, lest the
atmospherical air should get in, and mix with the pure oxygen gas.

EMILY.

How beautifully it burns!

CAROLINE.

But it is already buried in the thick vapour. This, I suppose, is
sulphuric acid?

EMILY.

Are these acids always in a gaseous state?

MRS. B.

Sulphureous acid, as we have already observed, is a permanent gas, and
can be obtained in a liquid form only by condensing it in water. In its
pure state, the sulphureous acid is invisible, and it now appears in the
form of a white smoke, from its combining with the moisture. But the
vapour of sulphuric acid, which you have just seen to rise during the
combustion, is not a gas, but only a vapour, which condenses into liquid
sulphuric acid, by losing its caloric. But it appears from Sir H. Davy's
experiments, that this formation and condensation of sulphuric acid
requires the presence of water, for which purpose the vapour is received
into cold water, which may afterwards be separated from the acid by
evaporation.

Sulphur has hitherto been considered as a simple substance; but Sir H.
Davy has suspected that it contains a small portion of hydrogen, and
perhaps also of oxygen.

On submitting sulphur to the action of the Voltaic battery, he observed
that the negative wire gave out hydrogen; and the existence of hydrogen
in sulphur was rendered still more probable by his observing that a
small quantity of water was produced during the combustion of sulphur.

EMILY.

And pray of what nature is sulphur when perfectly pure?

MRS. B.

Sulphur has probably never been obtained perfectly free from
combination, so that its radical may possibly possess properties very
different from those of common sulphur. It has been suspected to be of a
metallic nature; but this is mere conjecture.

Before we quit the subject of sulphur, I must tell you that it is
susceptible of combining with a great variety of substances, and
especially with hydrogen, with which you are already acquainted.
Hydrogen gas can dissolve a small portion of it.

EMILY.

What! can a gas dissolve a solid substance?

MRS. B.

Yes; a solid substance may be so minutely divided by heat, as to become
soluble in a gas: and there are several instances of it. But you must
observe, that, in this case, a chemical union or combination of the
sulphur with the hydrogen gas is produced. In order to