Mainly used for the dyeing of cotton yarn, cotton cloth, wool or silk, this pigment is the pigmented product of the important vat dye indigo, has excellent light fastness, weather fastness and heat stability, gives blue tone, and can be A liquid dispersion dosage form is prepared, which is mainly used in the coloring.
Chemical properties. Indigo dye is a dark blue crystalline powder that sublimes at 390–392 °C (734–738 °F). It is insoluble in water, alcohol, or ether, but soluble in DMSO, chloroform, nitrobenzene, and concentrated sulfuric acid. The chemical formula of indigo is C16H10N2O2.