h passes_
(377. 783.). They prove, too, that this is not merely true with one
substance, as water, but generally with all electrolytic bodies; and,
further, that the results obtained with any _one substance_ do not merely
agree amongst themselves, but also with those obtained from _other
substances_, the whole combining together into _one series of definite
electro-chemical actions_ (505.). I do not mean to say that no exceptions
will appear: perhaps some may arise, especially amongst substances existing
only by weak affinity; but I do not expect that any will seriously disturb
the result announced. If, in the well-considered, well-examined, and, I may
surely say, well-ascertained doctrines of the definite nature of ordinary
chemical affinity, such exceptions occur, as they do in abundance, yet,
without being allowed to disturb our minds as to the general conclusion,
they ought also to be allowed if they should present themselves at this,
the opening of a new view of electro-chemical action; not being held up as
obstructions to those who may be engaged in rendering that view more and
more perfect, but laid aside for a while, in hopes that their perfect and
consistent explanation will ultimately appear.

* * * * *

822. The doctrine of _definite electro-chemical action_ just laid down,
and, I believe, established, leads to some new views of the relations and
classifications of bodies associated with or subject to this action. Some
of these I shall proceed to consider.

823. In the first place, compound bodies may be separated into two great
classes, namely, those which are decomposable by the electric current, and
those which are not: of the latter, some are conductors, others
non-conductors, of voltaic electricity[A]. The former do not depend for
their decomposability upon the nature of their elements only; for, of the
same two elements, bodies may be formed, of which one shall belong to one
class and another to the other class; but probably on the proportions also
(697.). It is further remarkable, that with very few, if any, exceptions
(414. 691.), these decomposable bodies are exactly those governed by the
remarkable law of conduction I have before described (694.); for that law
does not extend to the many compound fusible substances that are excluded
from this class. I propose to call bodies of this, the decomposable class,
_Electrolytes_ (664.).

[A] I mean here by voltaic electri