I observed a black coating on silver coins and a green coating on copper coins.which chemical phenomena is responsible for these coatings?what are the chemical names of green and black coatingss?

Asked by devangi meena | 29th May, 2013, 06:55: PM

Expert Answer:

Corrosion is the phenomena responsible for these coatings.

Black coating on silver coins is silver sulphide. It is formed by reaction of silver with hydrogen sulphide in the atmosphere.

Green coating on copper is copper carbonate. It is formed by reaction of copper with carbon dioxide, moisture and oxygen in the atmosphere.

Answered by  | 30th May, 2013, 03:15: PM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.