[Illustration: FIG. 185.—Apparatus for Electrolysis Experiment.]
Water is composed of oxygen and hydrogen and so bubbles of oxygen and hydrogen gas will rise from the liquid.
Figure 185 illustrates a very simple arrangement for decomposing acidulated water into oxygen and hydrogen gases.
It consists of a bottle with the bottom broken out, and provided with a cork fitted snugly into the neck. Two glass tubes pass through the cork. A small piece of platinum wire is sealed into the inside end of each glass tube. The platinum wires are connected to copper wires leading out of the lower ends of the tubes.
If the bottle is inverted and filled with a dilute solution of sulphuric acid, the current from two or three dry cells will decompose the water. The battery should be connected to the wires running through the glass tubes.
Bubbles of gas will rise from the platinum wires. Oxygen gas will rise from the positive wire or electrode and hydrogen gas from the negative electrode.
If two test tubes are filled with acidulated water and then inverted over the wires, the tubes will collect the gas. In a few minutes it will be noticed twice as much hydrogen as oxygen has been generated.
If copper or brass electrodes &re used the acid will attack the positive one and a chemical action will take place which will prevent the liberation of any appreciable amount of oxygen, unless an excessive amount of current is passed through.
ELECTROPLATING.
Electroplating consists of coating bodies with metal by means of an electric current.