_=376. Electroplating=_ is the name given to the process of coating substances with metal with the aid of the electric current. The copper sulphate, CuSO_{4}, is broken up into Cu and SO_{4} by the current. The Cu goes to the cathode, and the SO_{4} attacks the anode, gradually dissolving it if it be copper; that is, the _metal_ part of CuSO_{4} is carried in the direction of the current. Most metals are coated with copper before they are silver or gold plated. A solution of silver is used for silver plating, silver being used as the anode. =EXPERIMENT 150. To study the chemistry of electroplating.= _Apparatus._ Same as in last experiment, but use two carbon rods for the electrodes. Arrange as in Fig. 114, with the Cu replaced by another carbon. Two simple cells (§ 275) are also needed. =377. Directions.= (A) Allow the current to pass as before. Is copper still deposited? Does anything occur now at the surface of the anode? Is the copper deposited as rapidly as before? (B) Try the effect of the two simple cells joined in series, Instead of the two-fluid cell. (C) After a fair coating of copper has been deposited upon the carbon cathode, reverse the direction of the current through the copper solution; that is, use the coated rod for the anode. Allow the current to pass until a change takes place in the anode. _=378. Discussion.=_ Ions are the names given to the parts into which an electrolyte is decomposed by the electric current. In the case of CuSO_{4}, the ions are Cu and SO_{4}, which is called an acid radical. This SO_{4} can not dissolve carbon or platinum, so these are used when water is to be electrolyzed. Where copper is used as the anode for copper plating, the SO_{4} attacks it, forming CuSO_{4} again, and this keeps the solution strong. If carbon were used instead, the SO_{4} would take H_{2} from the water around the anode and H_{2}SO_{4} (sulphuric acid) would be formed, the oxygen of the water being set free at the anode. The amount of Cu dissolved from the copper anode equals nearly the amount deposited upon the cathode. Exp. 150 shows that the metal is carried in the direction of the current. As hydrogen is produced at the cathode it is chemically considered a metal.