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(organic chemistry)
NH2C6H4C6H4NH2 An aromatic amine with a melting point of 128°C; used as an intermediate in syntheses of direct dyes for cotton.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



4,4’-diaminodiphenyl, an organic compound.

Clear, lustrous crystals that darken in air and under the influence of light because of oxidation. Melting point Tm= 128° C; boiling point Tb = 400°C. It is readily soluble in alcohol and ether; it is an aromatic diamine. It forms salts with solutions of organic and inorganic acids—for example, with HC1, a dichlorhydrate, and with H2 SO4, a monosulfate. Benzidine is obtained by the isomerization of hydrazobenzene under the action of mineral acids. Benzidine was first obtained by this method by N. N. Zinin in 1845. It is an important intermediate product in the production of azo dyes. It is also widely used in analytical chemistry for the qualitative and quantitative determination of various cations and anions that oxidize benzidine to colored compounds (to yellow in a strongly acidic medium and blue in a neutral medium). Benzidine is a carcinogenic substance; its maximum permissible concentration in air is 1 mg/m3.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
We observed inverse (protective) associations between ASD diagnosis and several air toxics: 1,4-dichlorobenzene, 4,4'-methylene diphenyl diisocyanate (MDI), benzidine, and ethyl carbamate (urethane) and for 1,4-dichlorobenzene with autism severity.
Results and Discussion Synthesis of Dyes 6a-j Synthesis of Congo red dye and its derivatives (6a-j) was achieved in excellent yields, according to the synthetic strategy outlined in scheme 1 starting from benzidine (1).
** Worked at work or home with asbestos, arsenic salts, chromium salts, cadmium salts, asphalt, mineral oils, benzidine, benzene, isopropyl oil, dyestuffs, vinyl chloride, pesticides, herbicides, mustard gas, welding, and wood dust.
Next, the enzyme substrate (3,3',5,5'-tetramethyl benzidine peroxidase substrate and peroxidase solution B) was added, and the samples were incubated for 15 min (IgM) or 30 min (IgG).
Each sample was analyzed in duplicate using, peroxidase as the enzymatic tracer, a polyclonal antibody (L2) and tetramethyl benzidine as color reagent (L2 antibodies have a six-to eightfold higher affinity for ecdysone than for 20E).
A 50 [micro]l aliquot of the supernatant was added to the reaction mixture consisting of 1.6 mM tetramethyl benzidine and 0.1 mM H202, incubated at 37[degrees]C for 3 min, and then monitored the absorbance at 650 nm.
In this assay, performed in duplicate, the following was added to every 20 [micro]l of homogenate: 60 [micro]l of 90 mM potassium phosphate buffer (final pH adjusted to 7.2), 200 [micro]l of Na acetate/TMBZ working solution (0.012g of 3,3,5,5 tetramethyl benzidine dihydrochloride in 6 ml of methanol and 18 ml of 250 mM sodium acetate buffer at pH 5.0), and 25 [micro]l of 3% hydrogen peroxide ([H.sub.2][O.sub.2]).
Excess HRP-conjugate is washed off and solution of tetra methyl benzidine (TMP) reagent was added.
In brief, 10 [micro]L of Hb-enriched plasma was subjected to electrophoresis in a nondenaturing gel, and the gel was subsequently immersed in solution containing a congener of benzidine with a precipitate forming in the gel corresponding to the location of Hb-Hp complexes.
I noticed that one of the starting materials for the API resembled benzidine (4,4'-diaminobiphenyl), a known carcinogen.
Govindwar 2007.Biodegradation of benzidine based dye Direct Blue-6 byPseudomonas desmolyticum NCIM 2112.