Coloring materials chemical compounds are called, which have the characteristic to color other materials. According to DIN 55934 there is such color means, which are soluble in their application medium. Unsolvable color means are called pigments.
Coloring materials, which are used to color food are called food colors and are food additives.
One divides the coloring materials also into animal, vegetable, i.e. organic and inorganic coloring materials. A further organization differentiates between synthetic and natural coloring material-synthetic coloring materials is for example the Azofarbstoffe.Tieri coloring materials is coloring materials, which are produced by animals. Those are for example hemoglobin (the coloring material of the blood) and magenta (of the magenta snail). Vegetable coloring materials are coloring materials, which are produced by plants, for example Indigo, chlorophyll or Carotin (from the carrot). Inorganic coloring materials are coloring materials without carbon compounds, for example ochers.
As standard work the Colour index is considered to coloring material chemistry, therein all well-known color means is specified and characterized.
Color means (thus soluble coloring materials and insoluble pigments) are already used in the primeval times of mankind for the most diverse causes and operational areas.
One of the colors used for primeval times was the white and one of the first used weiss-Pigmente was the calcium oxide (CaO), which by burning from limestone is won, see also Kalkfarbe.In of the painting finally was long time white lead (Pb (OH) 2 2 PbCO3) the only available white color, to this at the beginning 19. Century one replaced by the zinc white (ZnO), which was preferred to white lead because of its smaller toxicity. Today almost exclusively the only in the last century developed titanium white (TiO2) is used. White soluble coloring materials are however physically impossible.
One of the most expensive colors was up to 18. Century the blue, for which there was the half jewel at the time at that time beside the synthetically manufactured Smalte pigments only Lapislazuli as raw material, which results in the Ultramarin after a labor intensive process then.
The oldest well-known organic coloring material is the Indigo, which already 2000 v. Chr. in Egypt use found. In Europe this coloring material from the was won. Beyond that and a set of coloring materials from plants is won. A composition of is in the article useful plants.
The most expensive coloring material of all times is the genuine magenta. It can be won from the color glands of the magenta snail, which occurs at the coast of the eastern Mediterranean. For 1 g of the coloring material approximately 8000 snails are needed.
Only by the development of the synthetic coloring materials in the center 19. Jh. increased the number of available colors and rose their durability strongly.
The first synthetic coloring material is here the Mauvein discovered by William Henry Perkin, which it center 19. Jh. with experiments with tar components found.
White light (spectrum within range 380-780 Nm) is a mixture of light with most diverse wavelengths. The chromatic spectrum is enough here from long-wave red light (approx. 780 Nm) up to shorter-wave violet light (approx. 380 Nm).
The impact of coloring materials is based now to absorb certain parts flash spectrum. The complementary color of the absorbed wavelength is the color, in which the coloring material appears.
The absorption of electromagnetic radiation, to which also light belongs, is based thereby on the rise of the energy level of electrons in molecules or atoms (increase of the distance between electrons and the atomic nuclei). Those for this necessary energy is taken from the incident electromagnetic radiation, the light.
Since these procedures on the quantum level take place, this absorption is not continuous, but effected only in certain stages, which correspond to the energetic difference between/the electrons before and/or after the absorption. This energy difference is in reverse proportionally to the absorbed wavelength of the incident light and certainly thus the color, in which the coloring material appears. A list of of some substances is under absorption values of chemical substances.
see also: Solvatochromie
If only simple \ sigma connections arise in the regarded molecules or atoms, then the energy is, is needed around the appropriate \ sigma electrons on a higher energetic level to lift too largely, it could come to a level increase by the visible part of the electromagnetic spectrum. Generally takes place here an absorption within the range UV light or the x-ray, so that this kind connections normally are unsuitable as coloring material. More easily succeeds the suggestion of the electrons, which arise to e.g. insatiated connections in \ pi connections so mentioned. These absorb already electromagnetic waves within the range of the long-wave UVrange-arrange one several such insatiated connections (Mehrfachbindungen) alternating with simple atomic bonds, then it comes to a Delokalisierung \ of the pi electrons, whereby the distance between the lively and the initial state is again reduced. A shift of the absorbed wavelengths corresponds to that to larger wavelengths. Generally applies here that the absorption region is shifted all the more upward, the number of these insatiated connections is the larger. A further rise can be achieved, in which such materials with particularly suitable other atomic's groups or atoms are combined, which function as electron acceptors or electron donors and/or are As Auxochrome (electron donors) or Antiauxochrome (electron acceptors) the for example following functional groups use can find:
The effect of these Auxo and/or Antiauxochrome is based thereby on a polarization of the molecule and a shift of the existing delokalisierten electrons following from it, which are available by the insatiated connections in the remainder of the molecule. The groups, which make appropriate delokalisierte electrons available, are called also Chromophore. How can be derived from the explanations above, primarily the Chromophore and its frequency, with which they occur in the regarded molecule, are responsible for the colour of a coloring material. The following functional groups can function for example as Chromophore:
\ pi overlay of aromatic rings and a Azogruppe by the example of the Aminoazobenzols.
Here represented \ the groups of pi of the molecule parts involved as structural formula and 3D-Modell.
Unfortunately the benzene rings are satisfied represented with this 3D-Bild. In the 2D-Darstellung carries each ring carbon only a hydrogen atom. Otherwise none are formed \ pi connections. Polarization and charge transfer in the Aminoazobenzol. The NH2-Gruppe works with its free pair of electrons still colordeepening.
The designations such as Chromophore and Auxochrome originate from the coloring material theory from Otto Nikolaus Witt.
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|Magenta (coloring material)|
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