Fig. 77 shows how water can be decomposed into its two constituents, hydrogen and oxygen, there being twice as much hydrogen formed as oxygen.
Fig. 78 shows a glass jar in which are placed two metal strips, A and C, these being connected with two cells. In this jar may be placed various conducting solutions to be tested. If, for example, we use a solution of copper sulphate, its chemical formula being CuSO4, the current will break it up into Cu (copper) and SO4. The Cu will be deposited upon C as the current passes from A to C through the solution. A is called the anode, and C the cathode.
Fig. 78.
Fig. 79 shows another form of jar used to study the decomposition of solutions by the electric current.
Fig 79.
80. Ions. When a solution is decomposed into parts by a current, the parts are called the Ions. When copper sulphate (Cu SO4) is used, the ions are Cu, which is a metal, and SO4, called an acid radical. When silver nitrate (Ag NO3) is used, Ag and NO3 are the ions. The metal part of the compound goes to the cathode.