te of ammonia_, in aqueous solution, gives rise to secondary
results very varied and uncertain in their proportions.

755. _Sulphurous acid._--Pure liquid sulphurous acid does not conduct nor
suffer decomposition by the voltaic current[A], but, when dissolved in
water, the solution acquires conducting power, and is decomposed, yielding
oxygen at the _anode_, and hydrogen and sulphur at the _cathode_.

[A] See also De la Rive, Bibliotheque Universelle, tom. xl. p. 205; or
Quarterly Journal of Science, vol. xxvii. p, 407.

756. A solution containing sulphuric acid in addition to the sulphurous
acid, was a better conductor. It gave very little gas at either electrode:
that at the _anode_ was oxygen, that at the _cathode_ pure hydrogen. From
the _cathode_ also rose a white turbid stream, consisting of diffused
sulphur, which soon rendered the whole solution milky. The volumes of gases
were in no regular proportion to the quantities evolved from water in the
voltameter. I conclude that the sulphurous acid was not at all affected by
the electric current in any of these cases, and that the water present was
the only body electro-chemically decomposed; that, at the _anode_, the
oxygen from the water converted the sulphurous acid into sulphuric acid,
and, at the _cathode_, the hydrogen electrically evolved decomposed the
sulphurous acid, combining with its oxygen, and setting its sulphur free. I
conclude that the sulphur at the negative electrode was only a secondary
result; and, in fact, no part of it was found combined with the small
portion of hydrogen which escaped when weak solutions of sulphurous acid
were used.

757. _Sulphuric acid._--I have already given my reasons for concluding that
sulphuric acid is not electrolyzable, i.e. not decomposable directly by the
electric current, but occasionally suffering by a secondary action at the
_cathode_ from the hydrogen evolved there (681.). In the year 1800, Davy
considered the sulphur from sulphuric acid as the result of the action of
the nascent hydrogen[A]. In 1804, Hisinger and Berzelius stated that it was
the direct result of the action of the voltaic pile[B], an opinion which
from that time Davy seems to have adopted, and which has since been
commonly received by all. The change of my own opinion requires that I
should correct what I have already said of the decomposition of sulphuric
acid in a former series of these Researches (552.): I do not now think that
the appe