ferric chloride

noun Chemistry.

1. a compound that in its anhydrous form, FeCl3, occurs as a black-brown, water-soluble solid; in its hydrated form, FeCl3⋅xH2O, it occurs in orange-yellow, deliquescent crystals: used chiefly in engraving, for deodorizing sewage, as a mordant, and in medicine as an astringent and styptic.