A coil of copper wire is immersed in a colorless solution of silver nitrate. Silver ion is reduced to metallic silver, which forms on the copper coil, and the copper is oxidized to cupric ions, which form a blue solution. When the coil is lifted from the solution after several hours some of the silver coating flakes off.
In this voltaic cell two small pieces of platinum wire are used as electrodes. The right hand side of the cell is an acidic aqueous solution of potassium dichromate; the left hand beaker contains a solution of potassium iodide. The salt bridge contains a solution of potassium sulfate. The meter is first set to measure current (in milliamps) and then to voltage (in millivolts). The experiment is very sensitive to the construction of the salt bridge. Here the current observed is low because the construction (the way the glass wool plugs and solution are arranged) of the salt bridge does not allow for good transfer of ions.