Preparing a metal electrode: Use a small piece of sand paper to remove corrosion or oxidized metal on the surface. Sand until the surface is clean and shiny. Wipe the metal with a laboratory tissue to remove any dirt or small metal slivers clinging to the surface.
Many metals react with oxygen in the air to form a thin oxide coating on the surface of the metal. This coating interferes with the reaction between the metal and its metal salt solution. By
vigorously sanding the metal strip immediately before the experiment, the oxide coating is removed and the reaction may proceed.
Preparing a metal salt solution: The metal salt solution is prepared by dissolving a metal salt in water. The initial concentration of this solution is important and should be accurately recorded. The metal salt is selected on the basis of its solubility, the reactivity of the anions, and its ionic strength.
The concentration of metal ions in the solution in the half-cell will change during the measurement. As metals are oxidized or reduced, the conentration of metal ions in the solution will change. Thus, the first somewhat stable potential observed after connecting the cell should be recorded.
Why you should sand the metal?