2i 8 Faraday's Researches

decomposing fused chlorides, iodides,, and other compounds,
according to the law before established (116, etc.), and the
opportunity of collecting certain of the products, without any
loss, by the use of apparatus of the nature of those already
described (524., 549; etc.),, render it probable that the voltaic
battery may become a useful and even economical manufactur-
ing instrument; for theory evidently indicates that an equiva-
lent of a rare substance may be obtained at the expense of three
or four equivalents of a very common body, namely, zinc: and
practice seems thus far to justify the expectation. In this
point of view I think it very likely that plates of platina or
silver may be used instead of plates of copper with advantage,
and that then the evil arising occasionally from solution of the
copper, and its precipitation on the zinc (by which the electro-
motive power of the zinc is so much injured), will be avoided

(783).

^f iv. On the Resistance of an Electrolyte to Electrolytic
Action, and on Interpositions

743. I have already illustrated, in the simplest possible form
of experiment (626, 645), the resistance established at the place
of decomposition to the force active at the exciting place. I
purpose examining the effects of this resistance more generally;
but it is rather with reference to their practical interference
with the action and phenomena of the voltaic battery, than
with any intention at this time to offer a strict and philosophical
account of their nature. Their general and principal cause is
the resistance of the chemical affinities to be overcome; but
there are numerous other circumstances which have a joint
influence with these forces (770, 776, etc.), each of
which would require a minute examination before a
correct account of the whole could be given.

744. As it will be convenient to describe the experi-
ments in a form different to that in which they were
made, both forms shall first be explained. Plates of
platina, copper, zinc, and other metals, about three-
quarters of an inch wide and three inches long, were
Fig. 48 associated together in pairs by means of platina
wires to which they were soldered, fig. 48, the plates
of one pair being either alike or different, as might be required.
These were arranged in glasses, fig. 49, so as to form Volta's
crown of cups. The acid or fluid in the cups never coverednow be obtained with ten pairs of