; for the attraction between particles of a
similar nature is that of aggregation, or cohesion, which is independent
of any chemical power.

MRS. B.

The 2d law of chemical attraction is, that _it takes place only between
the most minute particles of bodies_; therefore, the more you divide the
particles of the bodies to be combined, the more readily they act upon
each other.

CAROLINE.

That is again a circumstance which we might have supposed, for the finer
the particles of the two substances are, the more easily and perfectly
they will come in contact with each other, which must greatly facilitate
their union. It was for this purpose, you said, that you used iron
filings, in preference to wires or pieces of iron, for the decomposition
of water.

MRS. B.

It was once supposed that no mechanical power could divide bodies into
particles sufficiently minute for them to act on each other; and that,
in order to produce the extreme division requisite for a chemical
action, one, if not both of the bodies, should be in a fluid state.
There are, however, a few instances in which two solid bodies, very
finely pulverized, exert a chemical action on one another; but such
exceptions to the general rule are very rare indeed.

EMILY.

In all the combinations that we have hitherto seen, one of the
constituents has, I believe, been either liquid or aeriform. In
combustions, for instance, the oxygen is taken from the atmosphere, in
which it existed in the state of gas; and whenever we have seen acids
combine with metals or with alkalies, they were either in a liquid or an
aeriform state.

MRS. B.

The 3d law of chemical attraction is, that _it can take place between
two, three, four, or even a greater number of bodies_.

CAROLINE.

Oxyds and acids are bodies composed of two constituents; but I recollect
no instance of the combination of a greater number of principles.

MRS. B.

The compound salts, formed by the union of the metals with acids, are
composed of three principles. And there are salts formed by the
combination of the alkalies with the earths which are of a similar
description.

CAROLINE.

Are they of the same kind as the metallic salts?

MRS. B.

Yes; they are very analogous in their nature, although different in many
of their properties.

A methodical nomenclature, similar to that of the acids, has been
adopted for the compound salts. Each individual salt derives its name
from its constituent pa