Clark cell

An overview of the Clark cell, a type of electrochemical cell

Clark cell

The Clark cell is a type of electrochemical cell invented by Latimer Clark in 1873. It was widely used as a voltage standard for many years due to its stable and reproducible electromotive force (EMF). The Clark cell is a wet cell that uses a zinc anode and a mercury cathode, with a zinc sulfate solution as the electrolyte.

Latimer Clark, inventor of the Clark cell

Construction

The Clark cell consists of a glass vessel containing a zinc rod as the anode and a pool of mercury at the bottom as the cathode. The electrolyte is a saturated solution of zinc sulfate (ZnSO_). The zinc rod is immersed in the zinc sulfate solution, and the mercury forms the other electrode at the bottom of the cell.

Operation

The chemical reaction in the Clark cell involves the oxidation of zinc at the anode and the reduction of mercury ions at the cathode. The overall cell reaction can be represented as:

Zn(s) + Hg_SO_(s) _ ZnSO_(aq) + 2Hg(l)

This reaction produces a stable EMF of approximately 1.432 volts at 15°C, which was used as a standard for voltage measurements.

Applications

The Clark cell was primarily used as a standard cell for calibrating voltmeters and other electrical instruments. Its stable voltage output made it ideal for laboratory and industrial applications where precise voltage measurements were required.

Limitations

Despite its advantages, the Clark cell had some limitations. It was sensitive to temperature changes, which affected its voltage output. Additionally, the use of mercury posed environmental and health risks, leading to the development of alternative standard cells, such as the Weston cell.

Related pages

• Electrochemical cell
• Standard cell
• Latimer Clark
• Weston cell