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style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number 91-95-2
[7411-49-6] (4HCl)
RTECS number DV8750000
DV8753000 (4HCl)
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula C12H14N4
C12H18Cl4N4 (4HCl)
Molar mass 214.27 g/mol
360.11 g/mol (4HCl)
Melting point

175–177 °C
280 °C (4HCl.2H2O)

style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
MSDS External MSDS
EU classification Harmful (Xn)
S-phrases S36 S37 S45
R/S statement R20 R21 R22 R40
NFPA 704
LD50 mouse, oral Acute: 1834 mg/kg.
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

3,3'-Diaminobenzidine (DAB) is an organic compound. This derivative of benzidine is a precursor to polybenzimidazole fiber[1]. As its water-soluble tetrahydrochloride, it has been used in immunohistochemical staining of nucleic acids and proteins.[citation needed]


Diaminobenzidine, which is commercially available, is prepared by reacting 3,3'-dichlorobenzidine and ammonia with a copper catalyst at high temperature and pressure, followed by acidic workup.[2]


Diaminobenzidine is oxidized by hydrogen peroxide in the presence of hemoglobin to give a dark brown color. This is used to detect fingerprints in blood.[3] Improperly prepared tissue samples may give false positives[4] In neuroscience, this reaction is used to stain neurons which were prepared to contain hydrogen peroxidase, using complexes of injected biocytin with avidine or streptavidine, biotin, and the peroxidase.


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External links

  • Hans Schwenecke, Dieter Mayer “Benzidine and Benzidine Derivatives” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
  • US 3943175, Druin, Melvin L. & Oringer, Kenneth, "Synthesis of pure 3,3'-diaminobenzidine", issued 1976-03-09, assigned to Celanese Corporation 
  • "D.A.B. (Diaminobenzidine)". Chesapeake Bay Division, International Association for Identification. Retrieved 2007-11-09. 
  • "Liquid DAB Substrate" (pdf). Dako. Retrieved 2008-02-02.