umed; it
has such an extraordinary avidity for oxygen, I suppose, that the
receiver did not contain enough to satisfy the whole.

MRS. B.

That is certainly the case; for if the combustion were performed in the
exact proportions of 28 parts of carbon to 72 of oxygen, both these
ingredients would disappear, and 100 parts of carbonic acid would be
produced.

CAROLINE.

Carbonic acid must be a very strong acid, since it contains so great a
proportion of oxygen?

MRS. B.

That is a very natural inference; yet it is erroneous. For the carbonic
is the weakest of all the acids. The strength of an acid seems to depend
upon the nature of its basis, and its mode of combination, as well as
upon the proportion of the acidifying principle. The same quantity of
oxygen that will convert some bodies into strong acids, will only be
sufficient simply to oxydate others.

CAROLINE.

Since this acid is so weak, I think chemists should have called it the
_carbonous_, instead of the _carbonic_ acid.

EMILY.

But, I suppose, the carbonous acid is still weaker, and is formed by
burning carbon in atmospherical air.

MRS. B.

It has been lately discovered, that carbon may be converted into a gas,
by uniting with a smaller proportion of oxygen; but as this gas does not
possess any acid properties, it is no more than an oxyd; it is called
_gaseous oxyd of carbon_.

CAROLINE.

Pray is not carbonic acid a very wholesome gas to breathe, as it
contains so much oxygen?

MRS. B.

On the contrary, it is extremely pernicious. Oxygen, when in a state of
combination with other substances, loses, in almost every instance, its
respirable properties, and the salubrious effects which it has on the
animal economy when in its unconfined state. Carbonic acid is not only
unfit for respiration, but extremely deleterious if taken into the
lungs.

EMILY.

You know, Caroline, how very unwholesome the fumes of burning charcoal
are reckoned.

CAROLINE.

Yes; but, to confess the truth, I did not consider that a charcoal fire
produced carbonic acid gas. --Can this gas be condensed into a liquid?

MRS. B.

No: for, as I told you before, it is a permanent elastic fluid. But
water can absorb a certain quantity of this gas, and can even be
impregnated with it, in a very strong degree, by the assistance of
agitation and pressure, as I am going to show you. I shall decant some
carbonic acid gas into this bottle, which I fill first with water, in