PRODUCTS

Indigo is a blue powder that is soluble in hot aniline and practically insoluble in water and ethanol. It is yellow-green in concentrated sulfuric acid, and blue precipitate after dilution; indigo red in concentrated nitric acid, and then becomes reddish yellow. It is pale yellow in alkaline hydrosulfite reducing solution and colorless in acid solution.

Indigo is insoluble in water, acid and alkali. To make dye liquor adsorption fabrics, it must first undergo reduction to become indigo white. Indigo white is soluble in lye, and can be used to color animal or plant fibers. After dyeing, it is oxidized in the air to regenerate indigo, which is attached to the fiber and turns blue. Therefore, indigo dye must have reducing agent and lye.

Indigo is mainly used to dye cotton cloth or cotton yarn. Rural dye houses use fermentation to dye soil cloth. Most of the jeans are made of indigo dyed warp yarn and interwoven with white yarn. Cotton cloth that has not been mercerized is called wool blue cloth, which can be continuously impregnated with the insurance powder method, and can also be dyed with wool and silk, which is used in carpets and handicrafts. It is also used in the system of food dyes and organic pigments. Both indigo carmine and bromoindigo are derivatives of indigo.