140 Faraday's Researches

497. 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.

498. This constancy does not decide whether the muriatic
acid is electrolysed or not, although it proves that if so, it must
be in definite proportions to the quantity of electricity used.
Other considerations may, however, be allowed to decide the
point. The analogy between chlorine and oxygen, in their
relations to hydrogen, is so strong, as to lead almost to the
certainty, that, when combined with that element, they would
perform similar parts in the process of electro-decomposition.
They both unite with it in single proportional or equivalent
quantities; and the number of proportionals appearing to have
an intimate and important relation to the decomposability of a
body (432), those in muriatic acid, as well as in water, are the
most favourable, or those perhaps even necessary, to decom-
position. In other binary compounds of chlorine also, where
nothing equivocal depending on the simultaneous presence of it
and oxygen is involved, the chlorine is directly eliminated at the
anode by the electric current. Such is the case with the chloride
of lead (131); which may be justly compared with protoxide of
lead (138), and stands in the same relation to it as muriatic acid
to water. The chlorides of potassium, sodium, barium, etc., are
in the same relation to the protoxides of the same metals and
present the same results under the influence of the electric
current (138).

499. From all the experiments, combined with these con-
siderations, I conclude that muriatic acid is decomposed by the
direct influence of the electric current, and that the quantities
evolved are, and therefore the chemical action is, definite for a
definite quantity of electricity. For though I have not collected
and measured the chlorine, in its separate state, at the anode,
there can exist no doubt as to its being proportional to the
hydrogen at the cathode ; and the results are therefore sufficient
to establish the general law of constant electro-chemical action
in the case of muriatic acid.

500. In the dilute acid (496), I conclude that a part of the
water is electro-chemically decomposed, giving origin to the
oxygen, which appears mingled with the chlorine at the anode.vii. p. 407.nclude thathilosophical Transactions, 1826, p. 388).2.|