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.
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