Why does silver chloride turn grey in sunlight ?
Sunlight carries a good amount of energy, which makes silver chloride (AgCl) decompose in silver (Ag) and chloride ions. The metallic silver appears as very small ‘flakes’, esentially black, so these tiny black spots evenly distributed in the mass of white silver choride makes it look grey. Other silver salts are also decomposed by sunlight, that’s why they are kept in bottles made of dark glass or light-proof polimers. The interesting application is classic black&white photography: a thin layer of silver salts (usually silver bromide – AgBr) is evenly spread on a transparent film, the photographic film. When you take a picture, the camera lens projects a small but accurate image on the surface of this light-sensitive layer, and the silver bromide is decomposed more or less, depending of the intensity of the light received in various points of the image. As a consequence, there will be more or less decomposition of silver bromide to silver (black) and bromide ions – if you take a pictu
