Silver Nitrate
By Dick Sullivan

Silver nitrate should never be mixed with ammonia compounds as it can form azides which are powerful explosives. Silver nitrate is an oxidizer and should be treated as such. Never mix with finely particulated metals such as aluminum or zinc. Also avoid contact with organics.

Silver nitrate stains skin and can even cause burns. Keep away from anything you do not wish to see stained black. The material does not at first stain, it is just absorbed into the skin. Later, exposure to light causes it to darken and then turn jet black. For years Bostick would never let me forget the big black stain in our porcelain kitchen sink, the ever-present reminder of an early Kallitype session.

If you get silver nitrate on your skin the obvious thing is to rinse immediately in plenty of water. Rubbing with some common kitchen salt (sodium chloride) will help. In most cases this will usually suffice. If the concentration of the silver nitrate is not strong, and it hasn’t been on too long, there may be no staining. If so, then the harm done is mostly cosmetic. Frequently, however, one does not know about the contamination until it starts to darken from the light.

Stains can be removed from some materials with a permanganate and bisulfite treatment. It will vary in effectiveness depending on the material, of course. Wash the material in potassium permanganate, of 1 teaspoon to a pint of water. The material will turn dark red brown. This can be a little unsettling. Using 1 teaspoon of sodium bisulfite to a pint of water, rinse the material in this and the red color will immediately and completely disappear. There may be a slight release of sulfur dioxide gas, which is pungent, so this should be done in a ventilated area. I probably could have removed the stain in our sink had I know about this treatment.

This treatment was used in the past to removes stains from skin as well. Though there appears to be no harm from this treatment, Bostick & Sullivan does not recommend it.