In both chemistry and alchemy, a precipitate is a chemical created by a reaction in solution that itself is insoluable in the same solution. It will crystalize from out of the waters and either float to the surface, or "precipitate" to the bottom of the vessel.

White precipitate is generated by reacting solutions of corrosive sublimate (Mercuric Chloride) with Volatile Alkali (Ammonia).

It was used like many other Mercuric compounds in attempts to clean infections and cure syphilis from antiquity. It is very toxic, causing uncontrollable drooling, hair and tooth loss.