the purpose of combining
with, and neutralising, the superabundant acid which it meets with in
the stomach.

EMILY.

I am surprised that it is so perfectly clear; it does not at all partake
of the whiteness of the lime.

MRS. B.

Have you forgotten that, in solutions, the solid body is so minutely
subdivided by the fluid as to become invisible, and therefore will not
in the least degree impair the transparency of the solvent?

I said that the attraction of lime for carbonic acid was so strong, that
it would absorb it from the atmosphere. We may see this effect by
exposing a glass of lime-water to the air; the lime will then separate
from the water, combine with the carbonic acid, and re-appear on the
surface in the form of a white film, which is carbonat of lime, commonly
called _chalk_.

CAROLINE.

Chalk is, then, a compound salt! I never should have supposed that those
immense beds of chalk, that we see in many parts of the country, were a
salt. --Now, the white film begins to appear on the surface of the
water; but it is far from resembling hard solid chalk.

MRS. B.

That is owing to its state of extreme division; in a little time it will
collect into a more compact mass, and subside at the bottom of the
glass.

If you breathe into lime-water, the carbonic acid, which is mixed with
the air that you expire, will produce the same effect. It is an
experiment very easily made; --I shall pour some lime-water into this
glass tube, and, by breathing repeatedly into it, you will soon perceive
a precipitation of chalk--

EMILY.

I see already a small white cloud formed.

MRS. B.

It is composed of minute particles of chalk; at present it floats in the
water, but it will soon subside.

Carbonat of lime, or chalk, you see, is insoluble in water, since the
lime which was dissolved re-appears when converted into chalk; but you
must take notice of a very singular circumstance, which is, that chalk
is soluble in water impregnated with carbonic acid.

CAROLINE.

It is very curious, indeed, that carbonic acid gas should render lime
soluble in one instance, and insoluble in the other!

MRS. B.

I have here a bottle of Seltzer water, which, you know, is strongly
impregnated with carbonic acid:-- let us pour a little of it into a
glass of lime-water. You see that it immediately forms a precipitation
of carbonat of lime?

EMILY.

Yes, a white cloud appears.

MRS. B.

I shall now pour an additional qua