. The saline molecule is always
decomposed, as we know, in the primary phenomenon of electrolysis into
two elements which Faraday termed ions. Secondary reactions, no doubt,
often come to complicate the question, but these are chemical
reactions belonging to the general order of things, and have nothing
to do with the electric action working on the solution. The simple
phenomenon is always the same--decomposition into two ions, followed
by the appearance of one of these ions at the positive and of the
other at the negative electrode. But as the very slightest expenditure
of energy is sufficient to produce the commencement of electrolysis,
it is necessary to suppose that these two ions are not united by any
force. Thus the two ions are, in a way, dissociated. Clausius, who was
the first to represent the phenomena by this symbol, supposed, in
order not to shock the feelings of chemists too much, that this
dissociation only affected an infinitesimal fraction of the total
number of the molecules of the salt, and thereby escaped all check.
This concession was unfortunate, and the hypothesis thus lost the
greater part of its usefulness. M. Arrhenius was bolder, and frankly
recognized that dissociation occurs at once in the case of a great
number of molecules, and tends to increase more and more as the
solution becomes more dilute. It follows the comparison with a gas
which, while partially dissociated in an enclosed space, becomes
wholly so in an infinite one.
M. Arrhenius was led to adopt this hypothesis by the examination of
experimental results relating to the conductivity of electrolytes. In
order to interpret certain facts, it has to be recognized that a part
only of the molecules in a saline solution can be considered as
conductors of electricity, and that by adding water the number of
molecular conductors is increased. This increase, too, though rapid at
first, soon becomes slower, and approaches a certain limit which an
infinite dilution would enable it to attain. If the conducting
molecules are the dissociated molecules, then the dissociation (so
long as it is a question of strong acids and salts) tends to become
complete in the case of an unlimited dilution.
The opposition of a large number of chemists and physicists to the
ideas of M. Arrhenius was at first very fierce. It must be noted with
regret that, in France particularly, recourse was had to an arm which
scholars often wield rather clumsily. They joked
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