English alias: CI 73000; CI Vat Blue 1; 2-(1,3-Dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indol-3-one; 2,2 '-Bis(2,3-dihydro-3-oxoindolylidene); Indigo blue; Vat Blue 1; 2,2'-biindole-3,3'(1H,1'H)-dione;(delta(2,2' )-biindoline)-3,3'-dione;(delta(sup2,2')-biindoline)-3,3'-dione;(delta2,2'(3H,3'H)-Biindole)-3,3 '-dione;(delta2,2'-Biindoline)-3,3'-dione
Indigo pigment is one of the oldest pigments known to man and is widely used in the food, pharmaceutical and printing industries. The use of indigo as a fabric dye dates back at least to 2500 BC. Some costumes worn by ancient Egyptian mummies and blue hemp fabrics unearthed from Mawangdui in China are dyed by indigo. One of Yao’s people in China is named “Blue Yaoyao” because of its unique technology for producing and using indigo dyed fabrics. . In the food industry, indigo is used as a food coloring agent in the form of its sodium sulfonate or its aluminized form. It is called "bright blue" and bright blue aluminum lake in China, and its sodium sulfonate is the main form in the United States. It is called "indigo" .
Traits: blue powder (may be dark blue), odorless.
Solubility: slightly soluble in water, ethanol, glycerin and propylene glycol, insoluble in oils and fats. The 0.05% aqueous solution was dark blue. 1g is soluble in about 100ml, water at 25 ° C, the solubility in water is lower than other edible synthetic pigments, and the 0.05% aqueous solution is blue. Soluble in glycerin, propylene glycol, slightly soluble in ethanol, insoluble in oil. In case of concentrated sulfuric acid, it is dark blue, and after dilution, it is blue. Its aqueous solution plus sodium hydroxide is green to yellowish green. Indigo is easy to color, has a unique color tone, and is widely used. Heat resistance, light resistance, alkali resistance, oxidation resistance, salt tolerance and bacterial resistance are both poor. Fading when reducing, such as reduction with sodium sulfoxylate or glucose, it becomes white. The maximum absorption wavelength is 610 nm ± 2 nm .
Stability: Light resistance, poor heat resistance, unstable to citric acid, tartaric acid and alkali.
Melting point: 390-392 ° C (dec.)
Boiling point: 400.4 ° C at 760 mmHg
Flash point: 158.2 ° C
Steam pressure: 1.27E-06mmHg at 25°C
Mainly used for dyeing cotton, cotton, wool or silk. This pigment is an important pigmentation treatment of vat dye indigo. It has excellent light fastness, weather fastness and heat stability, giving blue tone and A liquid dispersion dosage form is prepared, which is mainly used for coloring and printing of viscose fiber. Used in biochemical agents and indicators as well as dyeing of cotton yarn, cotton, wool or silk.
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