cted.
Every chemical fact or experiment is an instance of the same kind; and
whenever the decomposition of a body is performed by the addition of any
single new substance, it is said to be effected by _simple elective
attractions_. But it often happens that no simple substance will
decompose a body, and that, in order to effect this, you must offer to
the compound a body which is itself composed of two, or sometimes three
principles, which would not, each separately, perform the decomposition.
In this case there are two new compounds formed in consequence of a
reciprocal decomposition and recomposition. All instances of this kind
are called _double elective attractions_.

CAROLINE.

I confess I do not understand this clearly.

MRS. B.

You will easily comprehend it by the assistance of this diagram, in
which the reciprocal forces of attraction are represented by numbers:

_Original Compound_
Sulphat of Soda.

Soda 8 Sulphuric Acid

|
| _Quies-_
|
| _cent_
|
_Result_ _Result_
Nitrat 7 _Divellent Attractions_ 6} 13 Sulphat
of Soda of Lime
|
|
| _Attrac-_
|
| _tions_
|

Nitric Acid 4 Lime
--
12

_Original Compound_
Nitrat of Lime.

We here suppose that we are to decompose sulphat of soda; that is, to
separate the acid from the alkali; if, for this purpose, we add some
lime, in order to make it combine with the acid, we shall fail in our
attempt, because the soda and the sulphuric acid attract each other by a
force which is superior, and (by way of supposition) is represented by
the number 8; while the lime tends to unite with this acid by an
affinity equal only to the number 6. It is plain, therefore, that the
sulphat of soda will not be decomposed, since a force equal to 8 cannot
be overcome by a force equal only to 6.

CAROLINE.

So far, this appears very clear.

MRS. B.

If, on the other hand, we