I think you're deeply confused -- possibly dangerously so, Kerik.Originally Posted by Kerik
HCN is a gas at room temperature, or when dissolved in water forms Prussic acid; it's the gas generated when potassium cyanide or sodium cyanide contact acids, and is the active ingredient in the gas chambers used to execute criminals.
For fixing wet collodion emulsions, KCN, potassium cyanide, is your chemical -- it's still hazardous, in that it will evolve hydrogen cyanide if it contacts acids, but it's not automatically deadly like HCN is in quantities above the lowest concentration you can smell. I would note that in a demo video I've seen of wet collodion tintype making, the KCN fixing step was done outdoors, after development was completed and the plate had been washed to remove all traces of the (acidic, ferrous sulfate based) developer. Given the rapidity with which you must work in wet plate, I'd say cyanide fixer is more hazardous than it needs to be if thiosulfates will do the job.