arance of the sulphur at the negative electrode is an immediate
consequence of electrolytic action.

[A] Nicholson's Quarterly Journal, vol. iv. pp. 280, 281.

[B] Annales de Chimie, 1804, tom. li. p. 173.

758. _Muriatic acid._--A strong solution gave hydrogen at the negative
electrode, and chlorine only at the positive electrode; of the latter, a
part acted on the platina and a part was dissolved. A minute bubble of gas
remained; it was not oxygen, but probably air previously held in solution.

759. It was an important matter to determine whether the chlorine was a
primary result, or only a secondary product, due to the action of the
oxygen evolved from water at the _anode_ upon the muriatic acid; i.e.
whether the muriatic acid was electrolyzable, and if so, whether the
decomposition was _definite_.

760. The muriatic acid was gradually diluted. One part with six of water
gave only chlorine at the _anode_. One part with eight of water gave only
chlorine; with nine of water, a little oxygen appeared with the chlorine;
but the occurrence or non-occurrence of oxygen at these strengths depended,
in part, on the strength of the voltaic battery used. With fifteen parts of
water, a little oxygen, with much chlorine, was evolved at the _anode_. As
the solution was now becoming a bad conductor of electricity, sulphuric
acid was added to it: this caused more ready decomposition, but did not
sensibly alter the proportion of chlorine and oxygen.

761. The muriatic acid was now diluted with 100 times its volume of dilute
sulphuric acid. It still gave a large proportion of chlorine at the
_anode_, mingled with oxygen; and the result was the same, whether a
voltaic battery of 40 pairs of plates or one containing only 5 pairs were
used. With acid of this strength, the oxygen evolved at the _anode_ was to
the hydrogen at the _cathode_, in volume, as 17 is to 64; and therefore the
chlorine would have been 30 volumes, had it not been dissolved by the
fluid.

762. Next with respect to the quantity of elements evolved. On using the
volta-electrometer, it was found that, whether the strongest or the weakest
muriatic acid were used, whether chlorine alone or chlorine mingled with
oxygen appeared at the _anode_, still the hydrogen evolved at the _cathode_
was a constant quantity, i.e. exactly the same as the hydrogen which the
_same quantity of electricity_ could evolve from water.

763. This constancy does not decide whether the