Resistance to Electrolysis	223
purpose, if a little nitric acid were added to the liquid in the
retarding cells, then the transmission of the current was very
much facilitated. For instance, in the experiment with one
pair of exciting plates and one intervening plate (747), fig. 52,
when a few drops of nitric acid were added to the contents of
cell ii, then the current of electricity passed with considerable
strength (though it soon fell from other causes (772, 776)),
and the same increased effect was produced by the nitric acid
when many interposed plates were used.
 757.	This seems to be a consequence of the diminution of
the difficulty of decomposing water when its hydrogen, instead
of being absolutely expelled, as in the former cases, is transferred
to the oxygen of the nitric acid, producing a secondary result
at the cathode (487); for in accordance with the chemical views
of the electric current and its action already advanced (648),
the water, instead of opposing a resistance to decomposition
equal to the full amount of the force of mutual attraction
between its oxygen and hydrogen, has that force counteracted
in part, and therefore diminished by the attraction of the
hydrogen at the cathode for the oxygen of the nitric acid which
surrounds it, and with which it ultimately combines instead
of being evolved in its free state.
 758.	When a little nitric acid was put into the exciting cells,
then again the circumstances favouring the transmission of the
current were strengthened, for the intensity of the current itself
was increased by the addition (641).   When therefore a little
nitric acid was added to both the exciting and the retarding cells,
the current of electricity passed with very considerable freedom.
 759.	When dilute muriatic acid was used, it produced and
transmitted a current more easily than pure dilute sulphuric
acid, but not so readily as dilute nitric acid.   As muriatic acid
appears to be decomposed more freely than water (500), and as
the affinity of zinc for chlorine is very powerful, it might be
expected to produce a current more intense than that from, the
use of dilute sulphuric acid; and also to transmit it more freely
by undergoing decomposition at a lower intensity (647).
 760.	In relation to the effect of these interpositions, it is
necessary to state that they do not appear to be at all dependent
upon the size of the electrodes, or their distance from each
other in the acid, except that when a current can -pass, changes
in these facilitate or retard its passage.   For on repeating the
experiment with one intervening and one pair of exciting plates
(747), fig. 52, and in place of the interposed plate P using some-