n 1  :  any of numerous blue iron pigments formerly regarded as the ferric salt of ferrocyanide  2  :  a dark blue crystalline hydrated compound Fe₄[Fe(CN)₆]₃·xH₂O that is a ferrocyanide of iron and is used as a test for ferric iron - called also ferric ferrocyanide  .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.