Why is silver nitrate solution used for staining fingers of voters during election?

Silver nitrate solution is used for staining the fingers of voters during elections due to its chemical properties and practical advantages:

1. Formation of a permanent mark: When silver nitrate (AgNO₃) solution comes into contact with the skin, it reacts with the chloride ions present in sweat to form silver chloride (AgCl), which is insoluble and black in color. This reaction is: $$\mathrm{AgNO}{}_3+\mathrm{NaCl}\to \mathrm{AgCl}+\mathrm{NaNO}{}_3$$ The black AgCl deposits on the skin, creating a visible and long-lasting mark.

2. Non-toxic and safe: Silver nitrate is relatively non-toxic in dilute solutions, making it safe for use on human skin.

3. Durability: The stain remains visible for several days, ensuring that the voter cannot vote multiple times. The mark fades gradually due to natural skin exfoliation.

4. Easy application: The solution can be applied using a simple brush or swab, making the process quick and efficient.

This method ensures voter integrity and prevents electoral fraud effectively.