4.2.1.1 Defects of a simple Electric Cell The practical value and performance of simple cells is limited by the following defects: (a) Polarization In the reaction in the simple cell, hydrogen gas is evolved. It collects in bubbles around the positive electrode and-eventually insulate the positive electrode from the solution. This stops the reaction. This process is known as polarization. It is minimized by use of a depolarizer. This is a chemical which reacts with the hydrogen to produce water e.g. manganese dioxide. (b) Local Action Impurities such as iron and lead embedded in the zinc electrode form small local cells. The impurity acts as the positive electrode and zinc as the negative. The formation of these local cells between the impurities and the zinc electrode is referred to as local action. It tends to wear the zinc electrod...