Emily Dickinson Lexicon

PRUSS-IAN, a. [from Prussia.]

Pertaining to Prussia. Prussian blue, a bi-salt composed of two equivalents of the sesquicyanid of iron, which performs the functions of an acid, with one equivalent of sesquoxyd of iron, which performs the functions of a base. This salt is of a beautiful deep blue, and is much used as a pigment. It is also use in medicine.