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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 .
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]
This was an important invention, because at that time, the available blue pigments were either not very successful or were not affordable for large scale use. The pigment was first mentioned in a letter, the first of several, from Frisch to the president of the Royal Academy of Sciences, Gottfried Wilhelm Leibniz , dated March 1708.
Copper phthalocyanine ("phthalo blue") is a synthetic blue pigment frequently used in paints, inks, and dyes. It is highly valued for its superior properties such as light fastness, tinting strength, covering power and resistance to the effects of alkalis and acids. It has the appearance of a blue powder, insoluble in most solvents including ...
Cyanides as a chemical class were named because they were discovered in ferrocyanide. Ferrocyanide in turn was named in Latin to mean "blue substance with iron." The dye Prussian blue had been first made in the early 18th century. The word "cyanide" used in the name is from κύανος kyanos, Greek for "(dark) blue."
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]
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]
Marking out a metal bar. 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.