f decomposition he called Electrolysis. All these
terms have become current in science. He called the positive electrode
the Anode, and the negative one the Cathode, but these terms, though
frequently used, have not enjoyed the same currency as the others. The
terms Anion and Cation, which he applied to the constituents of the
decomposed electrolyte, and the term Ion, which included both anions and
cations, are still less frequently employed.

Faraday now passes from terminology to research; he sees the necessity
of quantitative determinations, and seeks to supply himself with a
measure of voltaic electricity. This he finds in the quantity of water
decomposed by the current. He tests this measure in all possible ways,
to assure himself that no error can arise from its employment. He
places in the course of one and the same current a series of cells with
electrodes of different sizes, some of them plates of platinum, others
merely platinum wires, and collects the gas liberated on each distinct
pair of electrodes. He finds the quantity of gas to be the same for all.
Thus he concludes that when the same quantity of electricity is caused
to pass through a series of cells containing acidulated water, the
electro-chemical action is independent of the size of the electrodes.[3]
He next proves that variations in intensity do not interfere with this
equality of action. Whether his battery is charged with strong acid
or with weak; whether it consists of five pairs or of fifty pairs; in
short, whatever be its source, when the same current is sent through his
series of cells the same amount of decomposition takes place in all. He
next assures himself that the strength or weakness of his dilute acid
does not interfere with this law. Sending the same current through
a series of cells containing mixtures of sulphuric acid and water of
different strengths, he finds, however the proportion of acid to water
might vary, the same amount of gas to be collected in all the cells.
A crowd of facts of this character forced upon Faraday's mind the
conclusion that the amount of electro-chemical decomposition depends,
not upon the size of the electrodes, not upon the intensity of the
current, not upon the strength of the solution, but solely upon the
quantity of electricity which passes through the cell. The quantity
of electricity he concludes is proportional to the amount of chemical
action. On this law Faraday based the construction of his celeb