Do you observe the internal commotion that already begins to take place?
It is produced by the combination of these two substances; and yet the
acid has in this case to overcome not only the resistance which the
strong cohesion of the particles of copper opposes to their combination
with it, but also to overcome the weight of the copper, which makes it
sink to the bottom of the glass, and prevents the acid from having such
free access to it as it would if the metal were suspended in the liquid.

EMILY.

The acid seems, however, to overcome both these obstacles without
difficulty, and appears to be very rapidly dissolving the copper.

MRS. B.

By this means it reduces the copper into more minute parts than could
possibly be done by any mechanical power. But as the acid can act only
on the surface of the metal, it will be some time before the union of
these two bodies will be completed.

You may, however, already see how totally different this compound is
from either of its ingredients. It is neither colourless, like the acid,
nor hard, heavy, and yellow like the copper. If you tasted it, you would
no longer perceive the sourness of the acid. It has at present the
appearance of a blue liquid; but when the union is completed, and the
water with which the acid is diluted is evaporated, the compound will
assume the form of regular crystals, of a fine blue colour, and
perfectly transparent*. Of these I can shew you a specimen, as I have
prepared some for that purpose.

[Footnote *: These crystals are more easily obtained from a
mixture of sulphuric with a little nitric acid.]

CAROLINE.

How very beautiful they are, in colour, form, and transparency!

EMILY.

Nothing can be more striking than this example of chemical attraction.

MRS. B.

The term _attraction_ has been lately introduced into chemistry as a
substitute for the word _affinity_, to which some chemists have
objected, because it originated in the vague notion that chemical
combinations depended upon a certain resemblance, or relationship,
between particles that are disposed to unite; and this idea is not only
imperfect, but erroneous, as it is generally particles of the most
dissimilar nature, that have the greatest tendency to combine.

CAROLINE.

Besides, there seems to be no advantage in using a variety of terms to
express the same meaning; on the contrary it creates confusion; and as
we are well acquainted with the term Attraction