Direct Black 27

4-(4-Aminophenyl)benzenamine double nitriding, first and 4,5-Dihydroxynaphthalene-2,7-disulfonic acid coupling, and then in alkaline conditions and 6-Amino-4-hydroxynaphthalene-2-sulfonic acid?coupling, product to diazo, and Benzene-1,3-diamine coupling.

blue and black. Moderate soluble in water for hidden cyan, not soluble in alcohol. The strong sulfuric acid for Tracy in blue, diluted for dark purple. The dye solution to join strong hydrochloric acid have precipitation of dark; Add thick sodium hydroxide solution for purple.

Standard	Acid Resistance	Alkali Resistance	Light Fastness	Soaping		Water
				Fading	Stain	Fading	Stain
ISO	4	3	4	1-2		2-3