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By 1804, dye maker George Field in Britain had refined a technique to make lake madder by treating it with alum, and an alkali, [9] that converts the water-soluble madder extract into a solid, insoluble pigment. This resulting madder lake has a longer-lasting color, and can be used more efficaciously, for example by blending it into a paint.
It is soluble in fat, but insoluble in water. [4] Eleven conjugated double bonds give lycopene its deep red color. [4] Owing to the strong color, lycopene is used as a food coloring (registered as E160d) and is approved for use in the US, [5] Australia and New Zealand (registered as 160d), [6] and the European Union (E160d). [7]
Many soluble salts of acid dyes synthesized for textile-related purposes were transformed into insoluble salts or lake pigments by reaction with water-soluble salts of calcium, barium or lead, whereas basic dyes were treated with tannins or antimony potassium tartrate to yield pigments. [4] Synthetic coal tar alizarin dye samples, 1908.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Betalains are responsible for the deep red color of beets. Anthocyanins (literally "flower blue") are water-soluble flavonoid pigments that appear red to blue, according to pH. They occur in all tissues of higher plants, providing color in leaves, plant stem, roots, flowers, and fruits, though not always in sufficient quantities to be noticeable.
The season’s color palette is also shifting. Forget summer brights and spring pastels; autumn is all about warm, rich hues like burnt orange, golden yellow and maroon.
The formazans are compounds of the general formula [R-N=N-C(R')=N-NH-R"], formally derivatives of formazan [H 2 NN=CHN=NH], unknown in free form. [1]Formazan dyes are artificial chromogenic products obtained by reduction of tetrazolium salts by dehydrogenases and reductases.
Red dye No. 3 shows up in a lot of processed foods, Cording says. “Candy is where it’s most commonly seen,” she says. “But it’s also in certain drinks, like oral nutrition supplements ...