130	Faraday's Researches
current (449). Slight differences occurred, as before,, some-
times in one direction, sometimes in another; but the final
result was, that exactly the same quantity of water was decom-
posed 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', an^
downwards.
 463.	When an acid having a specific gravity of about 1.336
was employed, the results were most uniform, and the oxygen
and hydrogen (451) 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 remark-
able 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 of 1.232.    I have not yet had time to
examine minutely the circumstances attending the disappear-
ance 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.
 464.	Although not necessary for the practical use of the
instrument I am describing, yet as connected with the important
point of constant electro-chemical action upon water, I now
investigated the effects produced by an electric current passing
through aqueous solutions of acids, salts, and compounds, ex-
ceedingly 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 more usefully
described hereafter (513).
 465.	When solutions of caustic potassa or soda, or sulphate of
magnesia, or sulphate of soda, were acted upon by the electric
current, just as much oxygen and hydrogen was evolved from
them as from the diluted sulphuric acid, with which they were
compared.   When a solution of ammonia, rendered a better
conductor by sulphate of ammonia (290), or a solution of sub-
carbonate of potassa was experimented with, the hydrogen
evolved was in the same quantity as that set free from the
diluted sulphuric acid with which they were compared.   Hence
changes in the nature of the solution do not alter the constancy of
electrolytic action upon water.