Indigo

Dye

It is a coloring naturalness coming from the Indigotier and being used mainly to color the jeans.

Empirical formula: C₁₆H₁₀N₂O₂
Topological formula:

Molecular mass: 262,27
Melting point: 390 - 392°C
Solubility in water: <01g/100ml

A version of the history wants that this natural dye imported into Europe since the colonies of the new world supplanted the pastel and thus ruined the European economies which depended on it (south-western of France in particular). However with the Middle Ages a blue (Prussian blue, near to the indigo) of medicinal spring, was very widespread. Ruin of the " feet bleus" , these dyers who dyed clothing by pressing them, simply came from the mode of the white lace which had replaced that of fabrics to the bright colors.

The rainbow does not have 7 colors but an infinity

As a " seventh couleur" rainbow, the indigo is a legend which with the hard life. Actually, this color is only one nuance melted in the spectrum of the visible colors. The retina of the normal eye human (if one omits the anomalies such as the Daltonisme), contains 3 types of different cones to perceive the colors, each one having the maximum of answer in the wavelengths of the primary education red (answer to the Beta-carotene), of the primary education green and primary education blue. The indigo is theoretically only one negligible part of the spectrum of visible and does not appear in the normal decomposition of the light (because it is a dark color).

The indigo color was added and so to speak invented by Isaac Newton after having broken up the visible Lumière with a prism (which is naturally a continuum of frequencies and which reveals in fact only 6 dominant colors), the 3 primary educations (red, green, blue) and them 3 secondaries or tertiary sectors (orange, yellow, purple). It consciously determined Seven colors to make them coincide with 7 planets (known then), the 7 days of the week, the 7 notes of music, and the other septenary ones held for cultural references.

Of which color is the indigo?

Certain frank colors do not raise any ambiguity. One knows perfectly what is a Rouge, a Jaune or a Vert. The indigo, on the other hand is a badly definite color because of the myth of the seventh color. Supposed to be located on the rainbow between blue and the purple one, one deduced from it that the indigo was to be a precise nuance halfway between the purple one and blue. However the human eye is not very sensitive to the nuances in this zone of the spectrum and it is thus very subjective to be able to affirm that such intermediate nuance between blue and the purple one is to be classified in the blue ones or to classify in the purple ones. The only natural reference that one has of the indigo is the dyeing used to color the blue jean. However this dye is not other thing only one nuance of dark blue.

Ambiguity is maintained by the fact that there exists a nuance of indigo defined as blue purplished in the names of the colors used in language HTML: Whereas the indigo dye is close to blue harms #191970 , the color " web" #4B0082 , car more on the purple one. Certain software proposes even a kind of pink purplished as an indigo!

Expressions

the indigo Passerin is a Oiseau of North America, whose Mâle has a Plumage Bleu indigo.
a theory at pseudo-psychological base designates certain children like children indigos, according to the Couleur of the Will have that they would release; this theory is denounced for its tendencies Sectaire S in France and in other countries Européen S.

Examples of indigo

This gallery of photo watch although the indigo is a dark blue and that it does not contain a trace of purple.

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