The Collaborative International Dictionary
Williamson's blue
Prussian \Prus"sian\, a. [From Prussia, the country: cf. F. prussien.] Of or pertaining to Prussia. -- n. A native or inhabitant of Prussia.
Prussian blue (Chem.), any one of several complex double cyanides of ferrous and ferric iron; specifically, a dark blue amorphous substance having a coppery luster, obtained by adding a solution of potassium ferrocyanide (yellow prussiate of potash) to a ferric salt. It is used in dyeing, in ink, etc. Called also Williamson's blue, insoluble Prussian blue, Berlin blue, etc.
Prussian carp (Zo["o]l.) See Gibel.
Prussian green. (Chem.) Same as Berlin green, under Berlin.