XII Chemistry BIEK Topic - Silvering Of Mirror (Short Note)

Silvering Of Mirror (Short Note)
Mirror
A mirror is a glass plate coated with silver film on one side.




Silvering of Mirror
Coating a glass plate with silver is called silvering of mirror.




Explanation
When ammonical silver nitrate solution is treated with an aldehyde or other organic reducing agent on the surface of a glass plate the silver (I) is reduced to silver (0). This metallic silver is deposited on the glass plate as a fine film.

The chemical reactions that occur are as follows.

AgNO3 + 2NH4OH ----> [Ag(NH3)2]+ + NO3- + 2H2O

[Ag(NH3)2]+ + RCHO + H2O ----> Ag0↓ + RCOOH + 2NH4+




Method
The process of silvering of mirror is carried out through the following steps.

1. A solution of silver nitrate and ammonia is prepared in distilled water.

2. The aqueous solution of ammonia is slowly added to the solution of silver nitrate until brown precipitates of silver oxide form and dissolve.

3. The mixture is ammonical silver nitrate solution. This solution is mixed with a solution of an organic reducing agent such as glucose.

4. After mixing all the compounds thoroughly, the solution is poured on to the centre of a clean glass surface.

5. The reaction immediately starts and thin film metallic silver deposited on the surface of the glass.

6. The silver film is then coated with either shellae of copal varnish. Finally it is painted with some colour, normally red.




Spraying Method
Silvering of mirror can also be carried out by spraying method. In this technique, the mixture of chemicals is sprayed onto the glass sheet.