te it.

MRS. B.

That would certainly weaken the caustic power of the acid, but it would
increase the heat to an intolerable degree. Do you recollect nothing
that would destroy its deleterious properties more effectually?

EMILY.

An alkali might, by combining with it; but, then, a pure alkali is
itself a poison, on account of its causticity.

MRS. B.

There is no necessity that the alkali should be caustic. Soap, in which
it is combined with oil; or magnesia, either in the state of carbonat,
or mixed with water, would prove the best antidotes.

EMILY.

In those cases then, I suppose, the potash and the magnesia would quit
their combinations to form salts with the sulphuric acid?

MRS. B.

Precisely.

We may now make a few observations on the sulphure_ous_ acid, which we
have found to be the product of sulphur slowly and imperfectly burnt.
This acid is distinguished by its pungent smell, and its gaseous form.

CAROLINE.

Its aeriform state is, I suppose, owing to the smaller proportion of
oxygen, which renders it lighter than sulphur_ic_ acid?

MRS. B.

Probably; for by adding oxygen to the weaker acid, it may be converted
into the stronger kind. But this change of state may also be connected
with a change of affinity with regard to caloric.

EMILY.

And may sulphureous acid be obtained from sulphuric acid by a diminution
of oxygen?

MRS. B.

Yes; it can be done by bringing any combustible substance in contact
with the acid. This decomposition is most easily performed by some of
the metals; these absorb a portion of the oxygen from the sulphuric
acid, which is thus converted into the sulphureous, and flies off in its
gaseous form.

CAROLINE.

And cannot the sulphureous acid itself be decomposed and reduced to
sulphur?

MRS. B.

Yes; if this gas be heated in contact with charcoal, the oxygen of the
gas will combine with it, and the pure sulphur is regenerated.

Sulphureous acid is readily absorbed by water; and in this liquid state
it is found particularly useful in bleaching linen and woollen cloths,
and is much used in manufactures for those purposes. I can show you its
effect in destroying colours, by taking out vegetable stains--I think I
see a spot on your gown, Emily, on which we may try the experiment.

EMILY.

It is the stain of mulberries; but I shall be almost afraid of exposing
my gown to the experiment, after seeing the effect which the sulphuric
acid produced on that of