fact, resolves itself simply into an increase in the size of the electrodes
(725.).

727. The _third point_, in respect to which the principle of equal
electro-chemical action on water was tested, was _variation of the strength
of the solution used_. In order to render the water a conductor, sulphuric
acid had been added to it (707.); and it did not seem unlikely that this
substance, with many others, might render the water more subject to
decomposition, the electricity remaining the same in quantity. But such did
not prove to be the case. Diluted sulphuric acid, of different strengths,
was introduced into different decomposing apparatus, and submitted
simultaneously to the action of the same electric current (714.). Slight
differences occurred, as before, sometimes in one direction, sometimes in
another; but the final result was, that _exactly the same quantity of water
was decomposed in all the solutions by the same quantity of electricity_,
though the sulphuric acid in some was seventy-fold what it was in others.
The strengths used were of specific gravity 1.495, and downwards.

728. When an acid having a specific gravity of about 1.336 was employed,
the results were most uniform, and the oxygen and hydrogen (716.) most
constantly in the right proportion to each other. Such an acid gave more
gas than one much weaker acted upon by the same current, apparently because
it had less solvent power. If the acid were very strong, then a remarkable
disappearance of oxygen took place; thus, one made by mixing two measures
of strong oil of vitriol with one of water, gave forty-two volumes of
hydrogen, but only twelve of oxygen. The hydrogen was very nearly the same
with that evolved from acid of the specific gravity 1.232. I have not yet
had time to examine minutely the circumstances attending the disappearance
of the oxygen in this case, but imagine it is due to the formation of
oxywater, which Thenard has shown is favoured by the presence of acid.

729. Although not necessary for the practical use of the instrument I am
describing, yet as connected with the important point of constant
chemical action upon water, I now investigated the effects produced by an
electro-electric current passing through aqueous solutions of acids, salts,
and compounds, exceedingly different from each other in their nature, and
found them to yield astonishingly uniform results. But many of them which
are connected with a secondary action will be mo