Plating, Electro-

The deposition of metal by electrolysis so as to coat the conducting surface of objects therewith. The full details of the many proce es are very lengthy and cannot be given here. The general principle includes a battery or source of electric current. The object to be plated is connected to the negative terminal and is immersed in the solution. Thus with a battery the object is in electrical connection with the zinc plate. To the other terminal a metallic plate is connected. The object and the plate termed the anode being introduced into a suitable bath, the metal whose solution is in the bath is deposited upon the surface of the object. The bath is a solution of the metal in some form that will lend itself to the electrolytic action. The anode is often a plate of the metal of the bath, so that it di olves as fast as metal is deposited on the object, thus keeping up the strength of the solution. The objects to be plated must be scrupulously clean, and great care must be taken to keep the bath uncontaminated. When the object has a non-conducting surface, it is made conducting by being brushed over with plumbago q.v. In addition iron dust is sometimes dusted over it. This acts by precipitating the metal of the bath directly and thus giving a conducting basis for the metal to deposit on. To avoid getting iron in a bath the object may be dipped in copper sulphate solution. This precipitates copper in place of the iron and leaves the article in good shape for silver or other plating. Electro-plating, if made thick enough, gives a reverse of the article when separated therefrom. A direct copy can be got by a second plating, on the first plating after separation, or a wax impre ion can be employed. Under the different metals, formulae for the baths will be found. (See also Quick ing-- Steeling--Plating Balance.)