why silver chloride is stored in dark coloured bottles

Silver chloride (AgCl) is sensitive to light and can undergo a photochemical reaction when exposed to light, resulting in a change in color. The exposure to light causes the formation of silver metal, and this is visible as a darkening or discoloration of the silver chloride. To prevent this photochemical reaction and maintain the stability of silver chloride, it is stored in dark-colored bottles or containers.

Here’s how the process works:

1. Light Sensitivity:
   • Silver chloride is sensitive to light, especially to ultraviolet (UV) light. Exposure to light leads to the decomposition of silver chloride into silver metal and chlorine.
2. Darkening Reaction:
   • The reaction can be represented as follows: 2AgCl→LightUV2Ag+Cl22AgClUVLight​2Ag+Cl2​
3. Discoloration:
   • The formation of silver metal during this reaction is responsible for the darkening or discoloration observed in silver chloride.

To minimize the effects of light exposure and prevent the degradation of silver chloride, it is stored in dark-colored containers that block out UV light. This helps preserve the integrity and purity of the silver chloride for applications where its properties are crucial, such as in photographic materials.

It’s worth noting that silver chloride has been historically used in photography, where its light sensitivity is intentionally exploited to capture images. However, for storage and stability purposes, protection from light is necessary.