Electrolysis.—Electric analysis or more briefly electrolysis was the term applied by Faraday to the process of decomposing a liquid by the passage of a current of electricity through it.
The vessel containing the liquid is known as an electrolytic cell. In fig. 89, A is the cell, which may be of glass or of any other suitable material, and B is the liquid which is to be electrolyzed. Current enters by the positive electrode C, also known as the anode, traverses the liquid, and leaves by the negative electrode, or cathode, D.
The passage of current through the water splits up its molecules into their constituent atoms of oxygen and hydrogen, the former being given off in bubbles at the anode, and the latter at the cathode.
When current is passed through a solution of copper sulphate between platinum electrodes, the liquid is decomposed, atoms of copper being deposited at the cathode, bubbles of oxygen being given off at the anode, and sulphuric acid being formed in the liquid, which latter becomes more and more acid as the copper is withdrawn.
If, however, the anode be of copper instead of platinum, no sulphuric acid will be formed, neither will oxygen be given off at the anode. As copper is deposited at the cathode, an equal quantity will be dissolved at the anode, so that the original constitution of the liquid is maintained.