Prussian blue
Prus·sian blue
noun \ˈprəsh-ən-ˈblü\Definition of PRUSSIAN BLUE
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
