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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.



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.

References in periodicals archive ?
The five chemicals EPA is targeting are polybrominated diphenylethers (PBDEs), benzidine dyes, a short chain chlorinated paraffin, hexabromocyclododecane (HBCD), and phthalate di-n-pentyl phthalate (DnPP).
The FDA's primary form of oversight is to ensure that legal levels of contaminants like lead, arsenic and benzidine are not exceeded.
One hundred p1 of tetramethylene benzidine dihydrochloride (Kem-En-Tec) was then added as the substrate.
These dyes are also used as a substitute for benzidine dyes which shows dangerous carcinogen properties.
The presence of a small amount of blood may also be noted by using the Gualac test or the Benzidine test.
And the Environmental Protection Agency plans to evaluate six high-profile chemicals: BPA, phthalates used in vinyl and cosmetics, flame retardants, perflourinated compounds in nonstick surfaces, some parafins, and benzidine dyes and pigments.
Another reason to worry about Yellow 5: it can be contaminated with the human carcinogen benzidine.
Tetramethyl benzidine for horseradish peroxidase neurohistochemistry: a non carcinogenic blue reaction product with superior sensitivity for visualizing neural afferents and efferents.
Biomarker risk assessment and bladder cancer detection in a cohort exposed to benzidine.
After another washing step, plates were developed by adding peroxidase substrate tetramethyl benzidine (no.
The World Health Organisation has listed several dyes used in the textile industry as carcinogenic, including any dyes with a benzidine base, including Direct Blue 6, Direct Black 38 and Direct Brown 95, which have been banned in the US and the EU.
The key culprits are aromatic amines, benzidine and benzidine derivatives, all of which are used in the production of dyes.