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Indigo dye is an organic compound with a distinctive blue color. Indigo is a natural dye obtained from the leaves of some plants of the Indigofera genus, in particular Indigofera tinctoria. Dye-bearing Indigofera plants were once common throughout the world. It is now produced via chemical routes. Blue colorants are rare.
Isaac Newton's color sequence (red, orange, yellow, green, blue, indigo, violet) is kept alive today by several popular mnemonics. One is simply the nonsense word roygbiv, which is an acronym for the seven colors. [5] This word can also be envisioned as a person's name, "Roy G. Biv". [6]
True indigo is a shrub 1–2 metres (3 ft 3 in – 6 ft 7 in) high. It may be an annual, biennial, or perennial, depending on the climate in which it is grown. It has light green pinnate leaves and sheafs of pink or violet flowers. The rotenoids deguelin, dehydrodeguelin, rotenol, rotenone, tephrosin and sumatrol can be found in I. tinctoria. [3]
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Evidence indicates that what Newton meant by "indigo" and "blue" does not correspond to the modern meanings of those color words. Comparing Newton's observation of prismatic colors with a color image of the visible light spectrum shows that "indigo" corresponds to what is today called blue, whereas his "blue" corresponds to cyan. [14] [15] [16]
The first archaeological finds of woad seeds date to the Neolithic period. The seeds have been found in the cave of l'Audoste, Bouches-du-Rhône, France.Impressions of seeds of Färberwaid (Isatis tinctoria L.) or German indigo, of the plant family Brassicaceae, have been found on pottery in the Iron Age settlement of Heuneburg, Germany.
Generally, the color of a flame may be red, orange, blue, yellow, or white, and is dominated by blackbody radiation from soot and steam. When additional chemicals are added to the fuel burning, their atomic emission spectra can affect the frequencies of visible light radiation emitted - in other words, the flame appears in a different color ...
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