These operations are carried out on a very large scale in the various factories, but it is possible to reproduce them in any boy’s workshop or laboratory, with very simple equipment.
The proper chemicals, a tank, and a battery are the only apparatus required. The current must be supplied by storage cells or a bichromate battery because the work will require five or six amperes for quite a long period.
A small rectangular glass jar will make a first class tank to hold the electrolyte.
The simplest electro-plating process, and the one that the experimenter should start with is copper-plating.
Fill the tank three-quarters full of pure water and then drop in some crystals of copper-sulphate until the liquid has a deep blue color and will dissolve no more.
Obtain two copper rods and lay them across the tank. Cut two pieces of sheet copper having a tongue at each of two corners so that they can be hung in the solution, as shown in Figure 313. Hang both of the sheets from one of the copper rods. Connect this rod to the positive pole of the battery. These sheets are known as the anodes.
Then if a piece of carbon, or some metallic object is hung from the other rod and connected to the negative pole of the battery, the electro-plating will commence. The apparatus should be allowed to run for about half an hour and then the object hung from the rod connected to the negative pole of the battery should be lifted out and examined. It will be found thickly coated with copper. It is absolutely necessary to have the poles of the battery connected in the manner stated, or no deposit of copper will take place.
Objects which are to be electro-plated must be free from all traces of oil or grease and absolutely clean in every respect, or the plating will not be uniform, because it will not stick to dirty spots.
Fig. 313.—A Glass Jar arranged to serve as an Electro-Plating Tank.