Silver nitrate is a chemical substance that is used to develop photographs and in some medical procedures. If the substance comes into contact with the skin, it leaves a residue which will gradually darken to a black or grey colour over several hours. You can remove silver nitrate stains if they are caught early. Once the stain becomes fully developed, it is usually impossible to remove, but it will wear off naturally.
Pour 1 to 2 tsp of household ammonia onto the stained area of the skin. Scrub the area firmly with a cloth to remove the silver nitrate stain.
Rinse the cloth thoroughly in clean water and apply 1 tsp of liquid hand soap to it.
Scrub the skin firmly with the soapy cloth to remove any residual traces of the silver nitrate and all traces of the ammonia.
Wipe the skin dry with a towel.
You can also try rubbing your skin gently with table salt to remove the silver nitrate stain.