Any azo compound containing two -N=N- groups.
| Member | Definition | Role |
|---|
| congo red | An indicator dye that is blue-violet at pH 3.0 and red at pH 5.0. | Congo Red |
| reactive red 120 dye | A bis(azo) compound that consists of a benzene core having two (4-amino-6-chloro-1,3,5-triazin-2-yl)amino groups attached at positions 1 and 4 and which in turn have 5-hydroxy-6-[(2-sulfophenyl)diazenyl]-2,7-disulfonaphthalen-4-yl groups attached to their 4-amino functions. | Reactive red 120 |
| scarlet red | A bis(azo) compound that is 2-naphthol substituted at position 1 by a {2-methyl-4-[(2-methylphenyl)diazenyl]phenyl}diazenyl group. A fat-soluble dye predominantly used for demonstrating triglycerides in frozen sections, but which may also stain some protein bound lipids in paraffin sections. | Sudan IV |
| sudan black b | A member of the class of perimidines that is 2,2-dimethyl-2,3-dihydro-1H-perimidine carrying a [4-(phenyldiazenyl)naphthalen-1-yl]diazenyl substituent at position 6. A fat-soluble dye predominantly used for demonstrating triglycerides in frozen sections and for staining of protein bound lipids in paraffin sections. | Sudan black B |
| sudan iii | A bis(azo) compound that is 2-naphthol substituted at position 1 by a 4-{[(2-methylphenyl)diazenyl]phenyl}diazenyl group. A fat-soluble dye predominantly used for demonstrating triglycerides in frozen sections, but which may also stain some protein bound lipids in paraffin sections. | Sudan III |