What is "berlin 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.

Berlin \Ber"lin\, n. [The capital of Prussia]

1. A four-wheeled carriage, having a sheltered seat behind the body and separate from it, invented in the 17th century, at Berlin.

2. Fine worsted for fancy-work; zephyr worsted; -- called also Berlin wool.

   Berlin black, a black varnish, drying with almost a dead surface; -- used for coating the better kinds of ironware.
   --Ure.

   Berlin blue, Prussian blue.
   --Ure.

   Berlin green, a complex cyanide of iron, used as a green dye, and similar to Prussian blue.

   Berlin iron, a very fusible variety of cast iron, from which figures and other delicate articles are manufactured. These are often stained or lacquered in imitation of bronze.

   Berlin shop, a shop for the sale of worsted embroidery and the materials for such work.

   Berlin work, worsted embroidery.

Blue \Blue\ (bl[=u]), n.

1. One of the seven colors into which the rays of light divide themselves, when refracted through a glass prism; the color of the clear sky, or a color resembling that, whether lighter or darker; a pigment having such color. Sometimes, poetically, the sky; as, to fly off into the blue.

2. A pedantic woman; a bluestocking. [Colloq.]

3. pl. [Short for blue devils.] Low spirits; a fit of despondency; melancholy. [Colloq.]

   Berlin blue, Prussian blue.

   Mineral blue. See under Mineral.

   Prussian blue. See under Prussian.