cy·a·nide 
(sīə-nīd′)
(sīə-nīd′)n. also cy·a·nid (-nĭd)
The anionic univalent CN group, or any of various salts or esters of hydrogen cyanide containing a CN group, especially the extremely poisonous compounds potassium cyanide and sodium cyanide.
tr.v. cy·a·nid·ed, cy·a·nid·ing, cy·a·nides
1. To treat (a metal surface) with cyanide to produce a hard surface.
2. To treat (an ore) with cyanide to extract gold or silver.