isturbances of the
electric fluid during chemical action, but am seeking to distinguish
and identify those actions on which the power of the voltaic battery
essentially depends.

929. If for the oxacid a hydracid be substituted (927.),--as one analogous
to the muriatic, for instance,--then the state of things changes
altogether, and a current due to the chemical action of the acid on the
base is possible. But now both the bodies act as electrolytes, for it is
only one principle of each which combine mutually,--as, for instance, the
chlorine with the metal,--and the hydrogen of the acid and the oxygen of
the base are ready to traverse with the chlorine of the acid and the metal
of the base in conformity with the current and according to the general
principles already so fully laid down.

930. This view of the oxidation of the metal, or other _direct_ chemical
action upon it, being the sole cause of the production of the electric
current in the ordinary voltaic pile, is supported by the effects which
take place when alkaline or sulphuretted solutions (931. 943.) are used for
the electrolytic conductor instead of dilute sulphuric acid. It was in
elucidation of this point that the experiments without metallic contact,
and with solution of alkali as the exciting fluid, already referred to
(884.), were made.

931. Advantage was then taken of the more favourable condition offered,
when metallic contact is allowed (895.), and the experiments upon the
decomposition of bodies by a single pair of plates (899.) were repeated,
solution of caustic potassa being employed in the vessel _v_, fig. 77. in
place of dilute sulphuric acid. All the effects occurred as before: the
galvanometer was deflected; the decompositions of the solutions of iodide
of potassium, nitrate of silver, muriatic acid, and sulphate of soda ensued
at _x_; and the places where the evolved principles appeared, as well as
the deflection of the galvanometer, indicated a current in the _same
direction_ as when acid was in the vessel _v_; i.e. from the zinc through
the solution to the platina, and back by the galvanometer and substance
suffering decomposition to the zinc.

932. The similarity in the action of either dilute sulphuric acid or
potassa goes indeed far beyond this, even to the proof of identity in
_quantity_ as well as in _direction_ of the electricity produced. If a
plate of amalgamated zinc be put into a solution of potassa, it is not
sensibly a