Question

Why the bottles containing silver salts are deep blue or black in colour?

Answer 1

The bottles containing silver salts are deep blue or black in colour to protect the interference of sunlight. In the presence of sunlight, the silver salts may decompose. Therefore, they are kept in deep blue or black-coloured bottles to prevent their decomposition.

Example: Silver chloride decomposes in the presence of sunlight to form silver and chlorine gas.

$2\mathrm{AgCl}\left(\mathrm{s}\right)\stackrel{\mathrm{Sunlight}}{\to }2\mathrm{Ag}\left(\mathrm{s}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)$