Types Of mercury cell

Mercury batteries were the most important energy source for small machinery and electronic tools like hearing aid, calculators, thermometers, watches, and various toys during world war and post-world War. Mercury cells were utilised for Large electronic equipment like a walkie-talkie. But a law was passed by the president of the United States, Bill Clinton, on May 13, 1996, called “the battery act.” Due to this law, the usage of batteries got reduced. The main objective of implementing this law was to reduce heavy metals and toxins from the surroundings like municipal waste, groundwater, and streams. Let us understand what mercury is and other important details about what type of battery is mercury.

What type of battery is mercury?

Another definition for Mercury cell is that it is a type of dry cell that contains potassium hydroxide and mercury oxide cathode, zinc anode as an electrolyte.

Types of mercury cell

There are mainly two types of mercury cells named zinc-mercuric oxide and cadmium-mercuric oxide cells.

1. Zinc-mercuric cell

It is a type of mercury cell that contains long storage life. The cell is usually stable with the voltage(1.35v). Their cell reaction is Zn + HgO= ZnO + Hg. Their electrochemical efficiency is 820 mAH/g (Zn) and 250 mAH/g (Hg).

2. Cadmium-mercuric cell

It is a cell that can be stable at high temperatures and low temperatures. It has a voltage of 0.91v. Its electrochemical efficiency is 480 mAH/g (Cd). Their cell reaction is Cd + HgO + H₂O = Cd(OH₂) + Hg.

Electrochemical reactions

It can be a pure mercury oxide (HgO) in the mercury cell or a mixture of manganese dioxide with mercury oxide. The use of graphite is usually seen in this because magnesium oxide is a non-conductor.

The half cell reaction at the anode is Zn (Hg) + 2OH gives ZnO + H₂O + 2e^–

The half cell reaction at the cathode is :-

HgO + H₂O + 2e^– gives Hg + 2OH

the standard potential of +0.0977 V during the reduction reaction.

The overall reaction is :-

Zn + HgO → ZnO + Hg

Working of mercury battery or cell

Sodium forms a mixture of two metals(amalgam) at the cathode with mercury. In the mercury cell, amalgam with water in a decomposer, a separate reactor where caustic soda solution and hydrogen gas are produced at a rate of 50%.

Recirculation of brine usually requires solid salt to maintain saltwater saturation. First, Dechlorination of brine occurs, and then purification is done by the precipitation filtration process. The purity of the product goes much higher. Along with oxygen, Chlorine is generally used without purification.

For the concentrate of the acidic solution, no steam is required. Out of all processes, the mercury cell consumes the most electricity.

Environmental contamination chances increase while using mercury. It demands protective measures to maintain the balance of nature and fair use of mercury. Mercury must be extracted from the caustic soda solution and hydrogen gas.

This production is not generally used in Europe, and mercury-based production is decreased.

Advantages of mercury cell

During the electrochemical reaction, zinc is converted into zinc chloride with the help of a dry cell. But the substance in the small container leaks out due to the porous zinc casing, and the lifetime of a cell is reduced by causing corrosion to the metal. Ions are not involved in the solution by the mercury cell during the reaction to change its lifetime.

Some extra points are as follows:

• They have a high capacity depending upon their size.

• They have a long shelf life of up to nine to ten years.

• They have a constant output of voltage which is (1.35v).

• It is very economical to produce mercury cells with old known technologies.

• Mercury cell chlorine gets separated by reducing impurities like sodium hypochlorite, sodium chloride, and oxygen.

Amount of mercury present in the mercury cell battery?

5mg of mercury can be present in a button cell battery.

Limitations

Mercury is a very harmful substance that can affect the human body. There are various environmental issues caused by it. It can largely affect organs like the kidney, digestive system, skin, eyes, immunity system, and nervous system. Even a small amount of mercury can be very harmful to the human body.

It’s also dangerous for the development of newborn children or early stages of children. Older people can also get affected by this as their organs become weak over the duration.

Conclusion

Usage of mercury and mercury cells was very popular during world wars. Still, due to environmental factors and various economic crises, they have been replaced by simple dry cells. Though they were very useful at that time, the risk factors were very great, and thus, they had to change by some means or other. But these batteries do not pose any health issues when used because the chances of mercury leak are very low. Bottom cell mercury batteries can leak out into the environment very easily.