Daniel Cell Construction and Working Principle

Construction of a Daniel Cell

A cylindrical shaped copper pot is the main container of the Daniel cell. This conductive outer container of the cell behaves as the positive terminal. The container contains a strong copper sulfate solution. This strong copper sulfate solution acts as a depolarize substance. Then there is a cylindrical porous pot placed coaxially in the main copper pot. Therefore the gap between the sidewall of the outer container and the porous pot is filled with the strong copper sulfate solution.

Again the porous pot contents dilute sulphuric acid inside it. The pot also holds the centrally immersed amalgamated zinc rod. The amalgamated zinc rod acts as the negative terminal of the daniel cell. The dilute sulphuric acid acts as the electrolyte of the battery cell.

daniel cell

Working Principle of a Daniel Cell

A Daniel cell produces hydrogen gas during its operation. The reaction between zinc and sulphuric acid takes place inside the porous pot. The outcomes of the reaction are zinc sulfate and hydrogen gas. Zinc leaves electrons in the zinc rod i.e. negative electrode.

The hydrogen then comes out to the outer copper sulfate solution through the wall of the porous pot. Where the hydrogen reacts with copper sulfate and produces sulphuric acid and pure copper.

This phenomenon deposits pure copper on the inner side of the main copper container. Actually, the reaction produces Cu++ ions. And when these ions reach the inner wall of the copper container i.e. positive electrode, the ions take electrons from the container. The electrons of the container are compensated by the electrons coming from the negative electrode through the external load. Although, we have not shown the load in the figure of Denial cell. But both the above oxidation and reduction reactions take place when there is a load between the negative and positive electrodes connected externally. At the same time, the negative terminal loses its zinc to create zinc sulfate in the electrolyte. Because the zinc sulfate gets dissolved in the electrolyte solution. As a result, there is a corrosion in the negative zinc rod during operation of the Daniel cell.

The standard EMF of a Daniel cell is about 1.07 to 1.14 volts. The internal resistance of the cell is about 2 to 3 ohms. The current-carrying capability of a Daniel cell is quite stable. Normally we use this type of cells in our laboratory experiments.

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