Nitroprussic

from The Collaborative International Dictionary of English v.0.48

Nitroprussic \Ni`tro*prus"sic\ (? or ?), a. [Nitro- + prussic.]
   (Chem.)
   Pertaining to, derived from, or designating, a complex acid
   called nitroprussic acid, obtained indirectly by the action
   of nitric acid on potassium ferrocyanide (yellow prussiate),
   as a red crystalline unstable substance. It forms salts
   called nitroprussides, which give a rich purple color with
   alkaline sulphides.
   [1913 Webster]