I, Ebonite plate; B and P, upper and lower plates of brass; R, insulating handle for upper plate.
obtained either from a voltaic or a magneto-electric battery. The process is mostly confined to electro-typing and electro-plating. - Electro-typing is the method of securing copies of medals, statuettes, etc. When copper, for example, has to be deposited upon a mould (made of plas-ter of Paris or gutta-percha), the mould is made a conductor by brushing it over with black-lead ; and, after attaching it to the negative pole of the battery, it is suspended in the solution of sulphate of copper, the positive pole consisting of a plate of the same metal. By the electrolysis of the solution copper is deposited on the surface of the mould, while sulphuric acid is set free; and this, by dissolving a portion of the copper at the positive pole, keeps the solution at constant strength. - Electro-plating is the process of covering forks, spoons, etc., made of the cheaper metals, with a coating of silver. The process is in reality electro-typing in silver instead of copper. The solution of silver (called the bath) consists of two parts of cyanide of silver, 10 of cyanide of potasssium, and 250 of water. By the electrolysis of this solution silver is deposited on the object which is placed in it.