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Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula Fe 3+ 4 [Fe 2+ ( CN ) 6 ] 3 .
Hiroshige also used Prussian blue extensively in his landscape prints. Other prominent Japanese artists to use it included Keisai Eisen , Utagawa Kunisada and Utagawa Sadahide . The theory that aizuri-e production was prompted by the 1842 sumptuary laws known as the TenpÅ Reforms is no longer widely accepted.
Prussian blue was developed around 1706. [6] It is on the World Health Organization's List of Essential Medicines. [7] As of 2016, it is only approved for medical use in Germany, the United States, and Japan. [8] [9] [10] Access to medical-grade Prussian blue can be difficult in many areas of the world including the developed world. [11]
The Prussian national and merchant flag was originally a simple black-white-black flag issued on May 22, 1818, but this was replaced on March 12, 1823, with a new flag. The revised one (3:5) was parted black, white, and black (1:4:1), showing in the white stripe the eagle with a blue orb bound in gold and a scepter ending in another eagle.
Prussian blue was first accidentally made around 1706, by heating substances containing iron and carbon and nitrogen, and other cyanides made subsequently (and named after it). Among its many uses, Prussian blue gives the blue color to blueprints , bluing , and cyanotypes .
Blue is used by the NATO Military Symbols for Land Based Systems to denote friendly forces, hence the term "blue on blue" for friendly fire, and Blue Force Tracking for location of friendly units. The People's Liberation Army of China (formerly known as the "Red Army") uses the term "Blue Army" to refer to hostile forces during exercises. [62]
Engineer's blue is prepared by mixing Prussian blue with a non-drying oily material (for example, grease).The coloured oil is rubbed onto a reference surface, and the workpiece is then rubbed against the coloured reference; the transfer (by contact) of the pigment indicates the position of high spots on the workpiece or conversely highlight low points. [1]
Marking blue or layout stain (sometimes called Dykem after trademark erosion of a popular brand, or Prussian blue after the blue pigment) is a dye used in metalworking to aid in marking out rough parts for further machining.