Why is silver chloride stored in dark coloured bottles?

Silver chloride is stored in dark coloured bottles because it decomposes in the presence of sunlight, releasing chlorine gas and forming metallic silver. Silver chloride (AgCl) is a white crystalline salt that is sensitive to light. When exposed to sunlight, it undergoes a chemical reaction called photodecomposition.

Chemical Reaction

2AgCl → 2Ag + Cl₂ (in presence of light)

• AgCl breaks down into metallic silver (Ag) and chlorine gas (Cl₂).
• This makes the salt lose its purity and usefulness.

Use of Dark Bottles

• Dark coloured bottles block or absorb sunlight.
• This prevents photodecomposition of AgCl.
• It ensures longer shelf life of the chemical.