The nigrosine black series are divided into oil-soluble nigrosine, alcohol-soluble nigrosine, and water soluble nigrosine.

Oil-soluble nigrosine black, referred to as oil black, international index number: solvent black 7. It is black uniform powder, widely used in dyeing and printing of cotton fabrics. When dyeing, the cotton fabric is immersed in a solution prepared with aniline salt, etc., and then oxidized to be dyed black. The dyes are resistant to sunlight and rain, and are very strong to hot soap solutions and dilute bleach solutions. It is blue-black when over-oxidized.

Alcohol-soluble nigrosine black, referred to as alcohol black, international index number: Solvent Black 5, black uniform powder, insoluble in water, soluble in ethanol (bluish black), benzene and toluene, easily soluble in oleic acid and stearic acid, when concentrated Sulfuric acid is blue to blue-black, after dilution, blue-black precipitation, when it meets concentrated nitric acid, it turns blue to blue-black. It has good acid resistance and light fastness. Solvent black 5 melting point is 275℃ and is mainly used for coloring rubber, insulating bakelite, carbon paper and resin.

Acid nirgrosine black international index number: acid black 2, black glittering granular material, soluble in water, the aqueous solution is blue-purple, adding sodium hydroxide solution produces brown-purple precipitation. It is blue when soluble in ethanol. It is also blue in concentrated sulfuric acid, and turns to purple after dilution, with precipitation.

Use 1: Mainly used for dyeing wool and silk, but also for leather dyeing (usually chromium mordant), as well as paper, wood products, soap, anodized aluminum coloring and manufacturing ink.

Use 2: Mainly used for the dyeing of leather, silk and woolen fabrics, and can also be made into lakes for color paper and printing.

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