ositions enter into the class of
ordinary effects.

549. It may be expressed as a general consequence, that the more directly
bodies are opposed to each other in chemical affinity, the more _ready_ is
their separation from each other in cases of electro-chemical
decomposition, i.e. provided other circumstances, as insolubility,
deficient conducting power, proportions, &c., do not interfere. This is
well known to be the case with water and saline solutions; and I have found
it to be equally true with _dry_ chlorides, iodides, salts, &c., rendered
subject to electro-chemical decomposition by fusion (402.). So that in
applying the voltaic battery for the purpose of decomposing bodies not yet
resolved into forms of matter simpler than their own, it must be
remembered, that success may depend not upon the weakness, or failure upon
the strength, of the affinity by which the elements sought for are held
together, but contrariwise; and then modes of application may be devised,
by which, in _association_ with ordinary chemical powers, and the
assistance of fusion (394. 417.), we may be able to penetrate much further
than at present into the constitution of our chemical elements.

550. Some of the most beautiful and surprising cases of electro-chemical
decomposition and _transfer_ which Sir Humphry Davy described in his
celebrated paper[A], were those in which acids were passed through
alkalies, and alkalies or earths through acids[B]; and the way in which
substances having the most powerful attractions for each other were thus
prevented from combining, or, as it is said, had their natural affinity
destroyed or suspended throughout the whole of the circuit, excited the
utmost astonishment. But if I be right in the view I have taken of the
effects, it will appear, that that which made the _wonder_, is in fact the
_essential condition_ of transfer and decomposition, and that the more
alkali there is in the course of an acid, the more will the transfer of
that acid be facilitated from pole to pole; and perhaps a better
illustration of the difference between the theory I have ventured, and
those previously existing, cannot be offered than the views they
respectively give of such facts as these.

[A] Philosophical Transactions, 1807, p. 1.

[B] Ibid. p, 24, &c.

551. The instances in which sulphuric acid could not be passed though
baryta, or baryta through sulphuric acid[A], because of the precipitation
of sulphate of baryta,