then pouring the fluoric acid over the wax, it corrodes the glass where
the scratches have been made.

CAROLINE.

I should like to have a bottle of this acid, to make engravings.

MRS. B.

But you could not have it in a _glass_ bottle, for in that case the acid
would be saturated with silex, and incapable of executing an engraving;
the same thing would happen were the acid kept in vessels of porcelain
or earthen-ware; this acid must therefore be both prepared and preserved
in vessels of silver.

If it be distilled from fluor spar and vitriolic acid, in silver or
leaden vessels, the receiver being kept very cold during the
distillation, it assumes the form of a dense fluid, and in that state is
the most intensely corrosive substance known. This seems to be the acid
combined with a little water. It may be called _hydro-fluoric acid_; and
Sir H. Davy has been led, from some late experiments on the subject, to
consider _pure_ fluoric acid as a compound of a certain unknown
principle, which he calls _fluorine_, with hydrogen.

Sir H. Davy has also attempted to decompose the fluoric acid by burning
potassium in contact with it; but he has not yet been able by this or
any other method, to obtain its basis in a distinct separate state.

We shall conclude our account of the acids with that of the MURIATIC
ACID, which is perhaps the most curious and interesting of all of them.
It is found in nature combined with soda, lime, and magnesia. _Muriat of
soda_ is the common sea-salt, and from this substance the acid is
usually disengaged by means of the sulphuric acid. The natural state of
the muriatic acid is that of an invisible permanent gas, at the common
temperature of the atmosphere; but it has a remarkably strong attraction
for water, and assumes the form of a whitish cloud whenever it meets any
moisture to combine with. This acid is remarkable for its peculiar and
very pungent smell, and possesses, in a powerful degree, most of the
acid properties. Here is a bottle containing muriatic acid in a liquid
state.

CAROLINE.

And how is it liquefied?

MRS. B.

By impregnating water with it; its strong attraction for water makes it
very easy to obtain it in a liquid form. Now, if I open the phial, you
may observe a kind of vapour rising from it, which is muriatic acid gas,
of itself invisible, but made apparent by combining with the moisture of
the atmosphere.

EMILY.

Have you not any of the pure muriatic acid ga