Leclanche Cell Construction and Working Principle


In the year 1886, the French scientist George Leclanche has developed a wet cell known as the Leclanche cell. At that time, the cell was very much useful for telegraphs, telephones, signaling and electric bell systems.

Construction of Leclanche Cell

A Leclanche cell consists of a big glass container. The glass container contains Ammonium Chloride solution. The ammonium chloride solution acts as the electrolyte of the battery. We immerse a zinc rod in the ammonium chloride solution. The zinc rod acts as the negative electrode of the battery.

Leclanche Cell

We immerse a porous pot in the ammonium chloride solution. Manganese dioxide is the positive electrode material of the battery. In other words, the manganese dioxide is the depolarize material of the battery. For that, the porous pot contains a mixture of manganese dioxide and carbon dust. There is a carbon rod along the central axis of the porous pot. The carbon rod serves for the conductive terminal of the positive electrode. The carbon dust improves the conductivity of the positive electrode mixture with the carbon rod.

Working Principle of Leclanche Cell

Whenever we connect a load externally in between positive and negative electrodes of the battery cell the oxidation and reduction reactions start.

First zinc atoms leave the zinc rod by leaving two electrons each in the zinc rod. In this way, the zinc atoms get ionized. At the same time, the zinc rod gets negativity.

The ammonium chloride splits into positive ammonium ions and negative chlorine irons. It is natural that an electrolyte always stays in its ionized form.

Then positive zinc ions combine with negative chlorine ions and form zinc chloride.

The free electrons of the negative zinc rod transfer to the positive carbon rod through the external load. These electrons then pass to the ammonium chloride solution. Then the ammonium ions in the solution take these electrons and produce hydrogen gas.

After that, the hydrogen gas diffuses inside the porous pot through the wall of the pot. Here, hydrogen reacts with manganese dioxide and forms manganese oxide and water.

The full oxidation and reduction reaction of the Leclanche cell is

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