ntity of the Seltzer water into the
lime-water--

EMILY.

How singular! The cloud is re-dissolved, and the liquid is again
transparent.

MRS. B.

All the mystery depends upon this circumstance, that carbonat of lime is
soluble in carbonic acid, whilst it is insoluble in water; the first
quantity of carbonic acid, therefore, which I introduce into the
lime-water, was employed in forming the carbonat of lime, which remained
visible, until an additional quantity of carbonic acid dissolved it.
Thus, you see, when the lime and carbonic acid are in proper proportions
to form chalk, the white cloud appears, but when the acid predominates,
the chalk is no sooner formed than it is dissolved.

CAROLINE.

That is now the case; but let us try whether a further addition of
lime-water will again precipitate the chalk.

EMILY.

It does, indeed! The cloud re-appears, because, I suppose, there is now
no more of the carbonic acid than is necessary to form chalk; and, in
order to dissolve the chalk, a superabundance of acid is required.

MRS. B.

We have, I think, carried this experiment far enough; every repetition
would but exhibit the same appearances.

Lime combines with most of the acids, to which the carbonic (as being
the weakest) readily yields it; but these combinations we shall have an
opportunity of noticing more particularly hereafter. It unites with
phosphorus, and with sulphur, in their simple state; in short, of all
the earths, lime is that which nature employs most frequently, and most
abundantly, in its innumerable combinations. It is the basis of all
calcareous earths and stones; we find it likewise in the animal and the
vegetable creations.

EMILY.

And in the arts is not lime of very great utility?

MRS. B.

Scarcely any substance more so; you know that it is a most essential
requisite in building, as it constitutes the basis of all cements, such
as mortar, stucco, plaister, &c.

Lime is also of infinite importance in agriculture; it lightens and
warms soils that are too cold, and compact, in consequence of too great
a proportion of clay. --But it would be endless to enumerate the various
purposes for which it is employed; and you know enough of it to form
some idea of its importance; we shall, therefore, now proceed to the
third alkaline earth, MAGNESIA.

CAROLINE.

I am already pretty well acquainted with that earth; it is a medicine.

MRS. B.

It is in the state of carbonat that magnesi