ssel; for
after several days minute bubbles of gas gradually appeared upon a glass
rod, inserted to retain the zinc and platina apart, and also upon the
platina plate itself, and these were hydrogen. They resulted principally in
this way:--notwithstanding the amalgamation of the zinc, the acid exerted a
little direct action upon it, so that a small stream of hydrogen bubbles
was continually rising from its surface; a little of this hydrogen
gradually dissolved in the dilute acid, and was in part set free against
the surfaces of the rod and the plate, according to the well-known action
of such solid bodies in solutions of gases (623. &c.).

972. But if the gases had been evolved in the second vessel by the
decomposition of water, and had tended to dissolve, still there would have
been every reason to expect that a few bubbles should have appeared on the
electrodes, especially on the negative one, if it were only because of its
action as a nucleus on the solution supposed to be formed; but none
appeared even after twelve days.

973. When a few drops only of nitric acid were added to the vessel A, fig.
84, then the results were altogether different. In less than five minutes
bubbles of gas appeared on the plates P' and P" in the second vessel. To
prove that this was the effect of the electric current (which by trial at
_c_ was found at the same time to be passing,) the connexion at _c_ was
broken, the plates P'P" cleared from bubbles and left in the acid of the
vessel B, for fifteen minutes: during that time no bubbles appeared upon
them; but on restoring the communication at _c_, a minute did not elapse
before gas appeared in bubbles upon the plates. The proof, therefore, is
most full and complete, that the current excited by dilute sulphuric acid
with a little nitric acid in vessel A, has intensity enough to overcome the
chemical affinity exerted between the oxygen and hydrogen of the water in
the vessel B, whilst that excited by dilute sulphuric acid alone has _not_
sufficient intensity.

974. On using a strong solution of caustic potassa in the vessel A, to
excite the current, it was found by the decomposing effects at _e_, that
the current passed. But it had not intensity enough to decompose the water
in the vessel B; for though left for fourteen days, during the whole of
which time the current was found to be passing, still not the slightest
appearance of gas appeared on the plates P'P", nor any other signs of the