of the connecting
moistened cotton?

MRS. B.

Exactly so; and you may render the experiment still more striking, by
putting into the central glass (k, fig. 3.) an alkaline solution, the
glauber salt being placed into the negative glass (l), and the positive
glass (i) containing only water. The acid will be attracted by the
positive wire (m), and will actually appear in the vessel (i), after
passing through the alkaline solution (k), without combining with it,
although, you know, acids and alkalies are so much disposed to combine.
--But this conversation has already much exceeded our usual limits, and
we cannot enlarge more upon this interesting subject at present.

CONVERSATION XIV.

ON ALKALIES.

MRS. B.

Having now given you some idea of the laws by which chemical attractions
are governed, we may proceed to the examination of bodies which are
formed in consequence of these attractions.

The first class of compounds that present themselves to our notice, in
our gradual ascent to the most complicated combinations, are bodies
composed of only two principles. The sulphurets, phosphurets, carburets,
&c. are of this description; but the most numerous and important of
these compounds are the combinations of oxygen with the various simple
substances with which it has a tendency to unite. Of these you have
already acquired some knowledge, but it will be necessary to enter into
further particulars respecting the nature and properties of those most
deserving our notice. Of this class are the ALKALIES and the EARTHS,
which we shall successively examine.

We shall first take a view of the alkalies, of which there are three,
viz. POTASH, SODA, and AMMONIA. The two first are called _fixed
alkalies_, because they exist in a solid form at the temperature of the
atmosphere, and require a great heat to be volatilised. They consist, as
you already know, of metallic bases combined with oxygen. In potash, the
proportions are about eighty-six parts of potassium to fourteen of
oxygen; and in soda, seventy-seven parts of sodium to twenty-three of
oxygen. The third alkali, ammonia, has been distinguished by the name of
_volatile alkali_, because its natural form is that of gas. Its
composition is of a more complicated nature, of which we shall speak
hereafter.

Some of the earths bear so strong a resemblance in their properties to
the alkalies, that it is difficult to know under which head to place
them. The celebrated Fre