\Hy`dro*cy*an"ic\, a. [Hydro-, 2 + anic: cf. F.
hydrocyanique.] (Chem.)
Pertaining to, or derived from the combination of, hydrogen
and cyanogen.
{Hydrocyanic acid} (Chem.), a colorless, mobile, volatile
   liquid, {HCN}, having a characteristic peach-blossom odor.
   It is one of the most deadly poisons. It is made by the
   action of sulphuric acid on yellow prussiate of potassium
   (potassium ferrocyanide), and chemically resembles
   hydrochloric and hydrobromic acids. Called also {prussic
   acid}, {hydrogen cyanide}, etc.