Definite Electro-Chemical Action    153
volta-electrometer (446), and that with the negative end of the
voltaic battery.
 544.	Immediately that the circuit was complete, the electro-
chemical action commenced in all the vessels.   The hydrogen
still rose in, apparently,  undiminished  quantities  from  the
positive zinc electrode in the first basin.   No oxygen was evolved
at the positive copper electrode in the second basin, but a sul-
phate of copper was formed there;   whilst in the third basin
the positive platina electrode evolved pure oxygen gas, and was
itself unaffected.   But in all the basins the hydrogen liberated
at the negative platina electrodes was the same in quantity, and
the same with the volume of hydrogen evolved in the volta-
electrometer, showing that in all the vessels the current had
decomposed an equal quantity of water.    In this trying case,
therefore, the chemical action of electricity proved to be perfectly
definite.
 545.	A similar experiment was made with muriatic acid
diluted with its bulk of water.   The three positive electrodes
were zinc, silver, and platina; the first being able to separate and
combine with the chlorine without the aid of the current;  the
second combining with the chlorine only after the current had
set it free; and the third rejecting almost the whole of it.   The
three negative electrodes were, as before, platina plates fixed
within glass tubes.    In this experiment, as in the former, the
quantity of hydrogen evolved at the cathodes was the same for
all, and the same as the hydrogen evolved in the volta-electro-
meter.    I have already given my reasons for believing that in
these experiments it is the muriatic acid which is directly de-
composed by the electricity (499);  and the results prove that
the quantities so decomposed are -perfectly definite and pro-
portionate to the quantity of electricity which has passed.
 546.	In this experiment the chloride of silver formed in the
second basin retarded the passage of the current of electricity,
by virtue of the law of conduction before described (130), so
that it had to be cleaned off four or five times during the course
of the experiment;  but this caused no difference between the
results of that vessel and the others.
 547.	Charcoal was used as the positive electrode in both
sulphuric and muriactic acids (543, 545); but this .change pro-
duced no variation of the results.   A zinc positive electrode,
in sulphate of soda or solution of common salt, gave the same
constancy of operation.
 548.	Experiments of a similar kind were then made with