Experimental Researches in Electricity, Volume 1Faraday, Michael
Science
Experimental Researches in Electricity, Volume 1
Faraday, Michael
Electricity; Electricity -- Early works to 1850
982. Fused _nitre_ at _a_ conducted much better than water: I was unable to
decide with certainty whether it was electrolyzed, but I incline to think
not, for there was no discoloration against the platina at the _cathode_.
If sulpho-nitric acid had been used in the exciting vessel, both the nitre
and the chloride of lead would have suffered decomposition like the water
(906.).
983. The results thus obtained of conduction without decomposition, and the
necessity of a certain electrolytic intensity for the separation of the
_ions_ of different electrolytes, are immediately connected with the
experiments and results given in S 10. of the Fourth Series of these
Researches (418. 423. 444. 419.). But it will require a more exact
knowledge of the nature of intensity, both as regards the first origin of
the electric current, and also the manner in which it may be reduced, or
lowered by the intervention of longer or shorter portions of bad
conductors, whether decomposable or not, before their relation can be
minutely and fully understood.
984. In the case of water, the experiments I have as yet made, appear to
show, that, when the electric current is reduced in intensity below the
point required for decomposition, then the degree of conduction is the same
whether sulphuric acid, or any other of the many bodies which can affect
its transferring power as an electrolyte, are present or not. Or, in other
words, that the necessary electrolytic intensity for water is the same
whether it be pure, or rendered a better conductor by the addition of these
substances; and that for currents of less intensity than this, the water,
whether pure or acidulated, has equal conducting power. An apparatus, fig.
84, was arranged with dilute sulphuric acid in the vessel A, and pure
distilled water in the vessel B. By the decomposition at _c_, it appeared
as if water was a _better_ conductor than dilute sulphuric acid for a
current of such low intensity as to cause no decomposition. I am inclined,
however, to attribute this apparent superiority of water to variations in
that peculiar condition of the platina electrodes which is referred to
further on in this Series (1040.), and which is assumed, as far as I can
judge, to a greater degree in dilute sulphuric acid than in pure water. The
power therefore, of acids, alkalies, salts, and other bodies in solution,
to increase conducting power, appears to hold good only in those cases
where the electrolyte subject to the current suffers decomposition, and
loses all influence when the current transmitted has too low an intensity
to affect chemical change. It is probable that the ordinary conducting
power of an electrolyte in the solid state (419.) is the same as that which
it possesses in the fluid state for currents, the tension of which is
beneath the due electrolytic intensity.
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