muriatic and oxy-muriatic acids, dry muriat of soda is a compound
of sodium and chlorine, for it may be formed by the direct
combination of oxy-muriatic gas and sodium. In his opinion,
therefore, what we commonly call muriat of soda contains neither
soda nor muriatic acid.]

EMILY.

I thought that salts, when solid, were always in the state of crystals;
but the common table-salt is in the form of a coarse white powder.

MRS. B.

Crystallisation depends, as you may recollect, on the slow and regular
reunion of particles dissolved in a fluid; common sea-salt is only in a
state of imperfect crystallisation, because the process by which it is
prepared is not favourable to the formation of regular crystals. But if
you dissolve it, and afterwards evaporate the water slowly, you will
obtain a regular crystallisation.

_Muriat of ammonia_ is another combination of this acid, which we have
already mentioned as the principal source from which ammonia is derived.

I can at once show you the formation of this salt by the immediate
combination of muriatic acid with ammonia. --These two glass jars
contain, the one muriatic acid gas, the other ammoniacal gas, both of
which are perfectly invisible--now, if I mix them together, you see they
immediately form an opake white cloud, like smoke. --If a thermometer
was placed in the jar in which these gases are mixed, you would perceive
that some heat is at the same time produced.

EMILY.

The effects of chemical combinations are, indeed, wonderful! --How
extraordinary it is that two invisible bodies should become visible by
their union!

MRS. B.

This strikes you with astonishment, because it is a phenomenon which
nature seldom exhibits to our view; but the most common of her
operations are as wonderful, and it is their frequency only that
prevents our regarding them with equal admiration. What would be more
surprising, for instance, than combustion, were it not rendered so
familiar by custom?

EMILY.

That is true. --But pray, Mrs. B., is this white cloud the salt that
produces ammonia? How different it is from the solid muriat of ammonia
which you once showed us!

MRS. B.

It is the same substance which first appears in the state of vapour, but
will soon be condensed by cooling against the sides of the jar, in the
form of very minute crystals.

We may now proceed to the _oxy-muriats_. In this class of salts the
_oxy-muriat of potash_ is the most worthy